impact of active faulting on the post lgm infill of le bourget lake western alps france we have used high resolution seismic imaging to detect and characterize the recent deformation recorded by the quaternary sediments of le bourget lake the last glacial episodes mis 6a and 2 i e riss and wurm scoured out an elongated over deepened basin to more than 300 m below the present lake level and the basin accumulated 150 m of post lgm to holocene sediments the well stratified character of the infill is locally disturbed by tectonic deformations and gravity reworking a northern fault zone in continuation with the left lateral strike slip culoz fault is imaged within the holocene and late glacial accumulations a southern fault zone is also detected which can be related to the sublacustrine continuation of a much smaller fault affecting the jura alpine foreland the col du chat left lateral strike slip fault different generations of fractures have been identified in the lake allowing correlation and mapping in pre quaternary substratum the culoz fault has a n 160 orientation within the post lgm sediments fractures related to the culoz fault have an orientation between n135 and 95 a cloos model 1932 is thus proposed to explain the observed pattern of lacustrine deformations the calculated horizontal slip rate for culoz fault during holocene is about 1 3 mm yr 1 and for the col du chat fault is around 0 6 mm yr 1

seismic stratigraphy of waterton lake a sediment starved glaciated basin in the rocky mountains of alberta canada and montana usa abstract upper and middle waterton lakes fill a glacially scoured bedrock basin in a large 614 km2 watershed in the eastern front ranges of the rocky mountains of southern alberta canada and northern montana u s a the stratigraphic infill of the lake has been imaged with 123 km of single channel fm sonar chirp reflection profiles offshore sonar data are combined with more than 2 5 km of multi channel land based seismic reflection profiles collected from a large fan delta three seismic stratigraphic successions sss i to iii are identified in waterton lake resting on a prominent basal reflector bedrock that reaches a maximum depth of about 250 m below lake level high standing rock steps reigels divide the lake into sub basins that can be mapped using lake floor reflection coefficients a lowermost transparent to poorly stratified seismic succession sss i up to 30 m thick is present locally between bedrock highs and has high seismic velocities 1750 2100 m s typical of compact till or outwash a second stratigraphic succession sss ii up to 50 m thick occurs throughout the lake basin and is characterised by continuous closely spaced reflectors typical of repetitively bedded and rhythmically laminated silts and clays most likely deposited by underflows from fan deltas paleo depositional surfaces identify likely source areas during deglaciation intervals of acoustically transparent seismic facies up to 5 m thick are present within sss ii at the northern end of upper waterton lake sss ii has a hummocky surface underlain by collapse structures and chaotic facies recording the melt of buried ice sediment collapse may have triggered downslope mass flows and may account for massive facies in sss ii a thin holocene succession sss iii

the effect of fluorine boron and excess sodium on the critical curve in the albite h 2 o system experiments to define the critical curve for a series of silicate melts in equilibrium with a hydrous fluid were carried out in a hydrothermal diamond anvil cell silicate compositions studied were albite with several wt excess na2o b2o3 and f2o 1 complete miscibility between melt and water was observed at lower pressure and temperature conditions compared to pure albite for all compositions for albite excess na2o the critical curve had been lowered by 143 and 247 c at 10 kbar for 5 and 10 wt excess na for albite 5 and 10 wt f the difference at 10 kbar was 147 and 246 c respectively and for albite 5 and 10 wt b differences of 168 and 262 c were found these results are likely to be additive with the presence of more than one of the components depressing the critical curve to even lower temperatures and pressures the results suggest that in complex pegmatitic systems complete miscibility between melt and fluid may be important in the final stages of crystallisation the unusual properties of fluid phases under conditions close to the critical curve in a silicate melt water system may be essential for the enrichment of trace elements in pegmatites as well as for the formation of typical pegmatite textures

the role of h 2 o in rapid emplacement and crystallization of granite pegmatites resolving the paradox of large crystals in highly undercooled melts granite pegmatite sheets in the continental crust are characterized by very large crystals there has been a shift in viewing pegmatites as products of very slow cooling of granite melts to viewing them as products of crystal growth in undercooled liquids with this shift there has been a renewed debate about the role of h2o in the petrogenesis of pegmatites based on data on nucleation of minerals and new viscosity models for hydrous granite melts it is argued that h2o is the essential component in the petrogenesis of granite pegmatites h2o is key to reducing the viscosity of granite melts which enhances their transport within the crust it also dramatically reduces the glass transition temperature which permits crystallization of melts at hundreds of degrees below the thermodynamic solidus which has been demonstrated by fluid inclusion studies and other geothermometers published experimental data show that because h2o drastically reduces the nucleation rates of silicate minerals the minerals may not be able to nucleate until melt is substantially undercooled in a rapidly cooling intrusion nucleation starts at its highly undercooled margins followed by inward crystal growth towards its slower cooling hotter core delay in nucleation may be caused by competition for crystallization by several minerals in the near eutectic melts and by the very different structures of minerals and the highly hydrated melts once a mineral nucleates however it may grow rapidly to a size that is determined by the distance between the site of nucleation and the point in the magma at which the temperature is approximately that of the mineral s liquidus assuming components necessary for mineral growth are available along the growth path granite pegmatites are apparently able to retain h2o during most of their crystallization histories within the confinement of their wall rocks pegmatitic texture is a consequence of delayed nucleation and rapid growth at large undercooling both of which are facilitated by high h2o li b f and p contents in granite pegmatite melts without retention of h2o the conditions for pegmatitic textural growth may be difficult to achieve loss of h2o due to decompression and venting leads to microcrystalline texture and potentially glass during rapid cooling as seen in rhyolites in contrast slow cooling within a large magma chamber promotes continuous exsolution of h2o from crystallizing magma growth of equant crystals and final solidification at the thermodynamic solidus these are the characteristics of normal granites that distinguish them from pegmatites

u pb ages of detrital zircons in lower cretaceous non marine successions of the gyeongsang basin northeast asia implications for sediment provenance abstract the cretaceous gyeongsang basin is the largest non marine mesozoic sedimentary basin of the korean peninsula the lower cretaceous successions of the gyeongsang basin are coevally correlated to those of the cretaceous gunsan basin in the yellow sea which is located far to the west of the gyeongsang basin this study presents u pb ages of detrital zircons to evaluate the sediment provenances of the gyeongsang basin the detrital zircon ages clearly show the different distributions between the northern uiseong area and southern jinju area areas of the gyeongsang basin the detrital zircons of the northern area have an age cluster in the jurassic or triassic whereas the detrital zircons of the southern area show a wide range of ages from early cretaceous to neoarchean in the gunsan basin detrital zircons from a core also yield ages ranging from early cretaceous to neoarchean the age distribution from the gunsan basin is similar to those of the southern gyeongsang basin except for the absence of jurassic detrital zircons the petrographic modal analysis of sandstones in the gyeongsang basin suggests a mixed provenance this study indicates that possible sediment provenances of the gyeongsang basin were shared with those of the gunsan basin we suggest that the sediment provenance of the northern gyeongsang basin was adjacent basement highs whereas sediments to the southern gyeongsang basin were probably derived from relatively distant source areas that possibly were located in the vicinity of the gunsan basin during the early cretaceous ca 113 ma

petrology geochemistry and geochronology of the post collisional triassic mangerite and syenite in the gwangcheon area hongseong belt south korea abstract the gwangcheon intrusive rocks occur in the hongseong collision belt of south korea which is thought to represent the eastern extension of the dabie sulu collision zone of china the central part of the gwangcheon intrusive complex consists of orthopyroxene bearing monzonite mangerite and the marginal part is composed of syenite north of the gwangcheon mangerite the post collisional 233 2 ma haemi biotite granite contains syenite enclaves shrimp u pb zircon analysis yields ages of 232 3 ma for the mangerite and 230 3 ma for a syenite enclave within the haemi biotite granite the mangerite syenite complex and syenite enclaves exhibit a shoshonitic affinity with a total alkalinity na2o k2o of 7 38 9 64 wt high k2o mg ba sr cr ni and lree contents and insignificant negative eu anomalies geochemical data indicate that the mangerite syenite intrusion and the syenite enclaves are post collisional igneous rocks formed by the partial melting of an enriched lithospheric mantle the heat for this melting was derived from asthenospheric upwelling following oceanic slab break off the shrimp age data suggest that both the gwangcheon intrusives and the syenite enclaves formed after the triassic continental collision of the north and south china blocks in korea

melt inclusions in pegmatite quartz complete miscibility between silicate melts and hydrous fluids at low pressure fluorine boron and phosphorus rich pegmatites of the variscan ehrenfriedersdorf complex crystallized over a temperature range from about 700 to 500 c at a pressure of about 1 kbar pegmatite quartz crystals continuously trapped two different types of melt inclusions during cooling and growth a silicate rich h2o poor melt and a silicate poor h2o rich melt both melts were simultaneously trapped on the solvus boundaries of the silicate fluorine boron phosphorus water system the partially crystallized melt inclusions were rehomogenized at 1 kbar between 500 and 712 c in steps of 50 c by conventional rapid quench hydrothermal experiments glasses of completely rehomogenized inclusions were analyzed for h2o by raman spectroscopy and for major and some trace elements by emp electron microprobe both types of melt inclusions define a solvus boundary in an xh2o t pseudobinary system at 500 c the silicate rich melt contains about 2 5 wt h2o and the conjugate water rich melt about 47 wt h2o the solvus closes rapidly with increasing temperature at 650 c the water contents are about 10 and 32 wt respectively complete miscibility is attained at the critical point 712 c and 21 5 wt h2o many pegmatites show high concentrations of f b and p this is particularly true for those pegmatites associated with highly evolved peraluminous granites the presence of these elements dramatically reduces the critical pressure for fluid melt systems at shallow intrusion levels at t 720 c water is infinitely soluble in a f b and p rich melt simple cooling induces a separation into two coexisting melts accompanied with strong element fractionation on the water rich side of the solvus very volatile rich melts are produced that have vastly different physical properties as compared to normal silicate melts the density viscosity diffusivity and mobility of such hyper aqueous melts under these conditions are more comparable to an aqueous fluid

palynostratigraphy of some pleistocene deposits in the western alps a review in the alps interglacial and interstadial deposits are rarely preserved due to the intense erosive effect of glaciers in the valleys fortunately some outcrops and cored sequences located in the field area ranging from lyon to evian provided sedimentary profiles datable by palynostratigraphy in a highly documented geomorphological context an overview of several palynological sequences studied in this large area is proposed and their position in a general chronostratigraphical pattern is discussed particular attention is paid to palynostratigraphical evidence whose relevance is tested with systematic comparisons with long reference european pollen sequences spanning several glacial cycles minimum ages are suggested for non glacial episodes corresponding to the deposits studied

coupled thermo hydro mechanical processes in the near field of a high level radioactive waste repository in clay formations the present paper provides an overview of key coupled thermo hydro mechanical thm processes in clay formations that would result from the development of a high level radioactive waste repository here in this paper clay formations include plastic clay such as the boom clay of belgium as well as more indurated clay such as the callovo oxfordian and upper toarcian of france and opalinus clay of switzerland first we briefly introduce and describe four major underground research laboratories urls that have been devoted to clay repository research over the last few decades much of the research results in this area have been gained through investigations in these urls and their supporting laboratory and modeling research activities then the basic elements in the development of a waste repository in clays are presented in terms of four distinct stages in repository development for each of these four stages key processes and outstanding issues are discussed a summary of the important areas of research needs and some general remarks then conclude this paper

high resolution seismic imaging of outcrop scale channels and an incised valley system within the fluvial dominated lower freshwater molasse aquitanian western swiss molasse basin abstract high resolution seismic reflection surveys on lake geneva near lausanne switzerland allow the interpretation of outcrop scale sedimentary features within the fluvial dominated lower miocene lower freshwater molasse bedrock seismic modelling of an outcrop is used to calibrate the seismic data and assist with interpretation seismic resolution is sufficient to image sandstone channel fill complexes 4 5 m thick five seismic facies are recognized and interpreted as fluvial architectural elements of the lower freshwater molasse two of these facies are characterized by fairly continuous reflections of variable frequency and low to moderate amplitude interpreted as metre thick channel fill complexes the lateral extent of such channels ranges from 100 to 170 m the other three seismic facies are characterized by moderate to high amplitude sub parallel continuous reflections the three facies are mainly distinguished using reflection frequency and continuity they correspond to distinct floodplain settings i e proximal intermediate and distal with respect to the active channel belt on a larger scale a portion of a ca 50 m deep incised valley system probably caused by a relative base level fall was identified two distinct valley fill units are recognized the lower unit was interpreted as comprising valley edge slump units by comparison with outcrop data the upper unit is interpreted as the fluvial fill deposited in the most landward portion of the valley

the seismic stratigraphy of okanagan lake british columbia a record of rapid deglaciation in a deep fiord lake basin this paper presents the first detailed data regarding the newly discovered deep infill of okanagan lake okanagan lake 50 00 n 119 30 w is 120 km long 3 5 km wide and occupies a glacially overdeepened bedrock basin in the southern interior of british columbia this basin and other elongate lakes of the region e g shuswap kootenay kalamalka canim and mahood lakes mark the site of westward flowing ice streams within successive cordilleran ice sheets an air gun seismic survey of okanagan lake shows that the bedrock floor is nearly 650 m below sea level more than 2000 m below the rim of the surrounding plateau the maximum thickness of pleistocene sediment in okanagan lake basin approaches 800 m forty six seismic reflection traverses and an axial profile show a relatively simple stratigraphy composed of three seismic sequences argued to be no older than the last glacial cycle 30 ka a discontinuous basal unit sequence i characterized by large scale diffractions and up to 460 m thick infills the narrow v shaped bedrock floor of the basin and is interpreted as a boulder gravel deposited by subglacial meltwaters overlying seismic sequence ii is composed of two sub sequences sub sequence iia is a chaotic to massive facies up to 736 m thick lakeshore exposures close to where this unit reaches lake level show deformed and chaotically bedded glaciolacustrine silts containing gravel lens and large ice rafted boulders the surface topography of this sub sequence is irregular and in general mimics the form of the underlying bedrock as a result of compaction this sequence passes laterally into stratified facies sub sequence iib at the northern end of the basin seismic sequence ii appears to record rapid ice proximal dumping of glaciolacustrine silt as the okanagan glacier backwasted upvalley in a deep lake a thin 60 m max laminated seismic sequence iii drapes the hummocky surface of sequence ii and represents postglacial sedimentation from fan deltas the extreme thickness of sequences i and ii in okanagan lake reflects the focussing of large volumes of meltwater and sediment into the basin during deglaciation pre existing sediments that pre date the last glacial cycle appear to have been completely eroded glaciological conditions during sedimentation may have been similar to marine based outlet glaciers calving in deep water in fiord basins in contrast to marine settings where ice bergs are free to disperse large volumes of dead ice were trapped within the basin structural evidence for sedimentation around dead ice blocks has been previously used to argue that the cordilleran ice sheet downwasted in situ we emphasize in contrast the trapping of dead ice left behind by rapidly calving lake based outlet glaciers

high resolution bathymetric mapping reveals subaqueous glacial landforms in the arctic alpine lake tarfala sweden in arctic alpine regions glacio lacustrine environments respond sensitively to variations in climate conditions impacting for example glacier extent and rendering former ice contact lakes into i

late pleistocene and holocene depositional history of sediments in flathead lake montana evidence from high resolution seismic reflection interpretation abstract this paper presents an interpretation of 3 5 khz reflection seismic data together with information from lower frequency seismic data and sediment cores from flathead lake in northwestern montana flathead lake is located at the margin of the cordilleran ice sheet during the last glacial maximum and is the repository for about 160 m of syn and post glacial sediment six seismic stratigraphic units a f are identified in flathead lake above the acoustic basement reflector the deepest unit is interpreted to be late pleistocene glacial till unit a overlain by well layered glaciolacustrine sediments unit b overlying seismic reflectors unit c include slump deposits turbidites fed by meltwater surges associated with retreat of the flathead glacial lobe and homogeneous silty mud preliminary age models suggest that the transition from glacial rhythmites unit b to more homogenous lake sediments unit c occurred approximately between 14 500 and 13 180 cal y b p parallel high amplitude reflectors of the oldest holocene unit unit d drape pleistocene stratigraphy sediment core analyses suggest that these fine sediments were deposited below wave base by suspension settle out in a lake similar to today s the mt mazama tephra 7630 80 cal y b p is interpreted as the top reflector of unit d onlap geometries between units d and e imply a significant drop in lake level before deposition of unit e sedimentation of unit e was confined to several sub basins that were separated by bedrock highs lake level rose gradually during deposition of unit e to form the well developed basal onlap geometry parallel high amplitude reflectors of the youngest holocene sediments unit f drape all of the older stratigraphy and bedrock highs across the lake basin suggesting a late holocene lake highstand

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

till tongue stratigraphy seismostratigraphic studies on the scotian and mid norwegian continental shelves have led to the development of a conceptual model for glacial deposition and erosion by ice sheets in a marine environment till tongue model some of the terminal deposits of the marine ending glaciers are composed in part of acoustically incoherent wedge shaped bodies the wedges are thought to be part of a grounding line system associated with a floating terminus according to the model the sedimentary wedges are formed through the accumulation of glacial debris by subglacial processes proximal to the grounding line together with a penecontemporaneous proglacial contribution from sediment gravity flows sedimentation rates appear to be highest near and proximal to the grounding line that is within a grounding line zone ice proximal stratified glaciomarine sediment accumulates from plumes within the water column and rain out of ice rafted debris the glaciomarine sediment interfingers with the till tongues resulting from oscillations of the grounding line till tongues represent discrete stratigraphic units formed in both vertical and lateral successions marginal to massive till deposits major till tongues can be correlated regionally for hundreds of kilometers and thus can provide a basis for stratigraphic correlation on the mid norwegian shelf lateral and vertical successions of till tongues delineate several large scale till units which represent major advances and retreats of the ice that probably were of both stadial and glacial rank we refer to this type of succession as a till tongue stratigraphy it appears that till tongue formation is limited to intermediate water depths which range from 75 to 1 000 m present water depth but those formed in water depths 600 700 in may not be strictly subglacial in origin we speculate that processes leading to the development of till tongues possibly give rise to the formation of subglacial undermelt till together with thin flow tills near the grounding line it is also possible that another type of subglacial till embracing concepts inherent in the expression deforming basal tills as described by alley and others 1989 may contribute to the formation of till tongues boundaries between the major till units of the mid norwegian shelf are mainly depositional in the zone of maximum glaciation near the shelf edge and upper slope proximal to this zone of major deposition intraformational erosional processes dominate and give rise to smooth widespread time transgressive erosional surfaces erosion progressively increases in a proximal direction beveling the earlier glacial deposits and ultimately reaches and modifies the bedrock surface these regional surfaces are analogous to the ross sea unconformity which was also formed by glacial erosion morainic deposits within a till tongue stratigraphy are termed grounding zone moraines and are subdivided into advance and retreat varieties with linear tabular and hummocky attributes fields of small morainic ridges lift off moraines form in basinal areas during recession

recent clastic sedimentation processes in lake puyehue chilean lake district 40 5 s clastic sedimentation processes in lake puyehue 40 5 s 72 5 w chile are described based on correlation of high resolution seismic profiles and multidisciplinary analysis of short sediment cores from two contrasting coring sites pu i and pu ii two main sedimentary environments are recognized in this oligotrophic lake i a proximal one which includes the delta of the main tributary the golgol river and is a deep flat basin with a ponded geometry and limited acoustic penetration and ii a distal one that is composed of several sub basins highlighting a drape geometry and better acoustic penetration based on the correlation of seismic data and sediment cores dated by radionuclides and the identification of tephra layers rininahue1907 cordon caulle 1921 22 and 1960 we argue that clastic sedimentation results essentially from the development of homopycnal flows at the end of the winter season in this monomictic lake whereas distal clastic environments pu ii coring site are dominated by biogenic production and appear to have been little affected by the 1960 chilean earthquake mw 9 5 and nearby volcanic eruptions this may not be the case for more proximal clastic environments pu i coring site which also experience sporadic hyperpycnal flows during major flood events in may june 1960 for example as several earthquake triggered landslides dammed the course of the golgol river and ca 7 106 m3 of volcaniclastic sediments fell over the drainage basin of the lake during the earthquake induced puyehue cordon caulle eruption successive outbursts in the golgol valley induced a mega flood in lake puyehue this hyperpycnal flow reworked a mixture of volcaniclastic and regolith derived sediments from the catchment as well as lacustrine sediments surrounding the golgol delta during the rising limb of the flood these recently reworked sediments are strikingly enriched in excess 210pb activity suggesting that positive anomalies in the activity of this isotope can be used to determine the source area of clastic sediments

earthquake triggered slumps 1935 timiskaming m6 2 in lake kipawa western quebec seismic zone canada abstract the western quebec seismic zone wqsz of eastern north america is characterised by frequent moderate magnitude intracratonic earthquakes e g 1732 m5 8 1935 m6 2 and 1944 m5 2 the wqsz is centered along the timiskaming and ottawa bonnechere grabens which form part of a complex aulacogen st lawrence rift within the canadian shield the wqsz includes the urban areas of montreal and ottawa but seismic risk analysis is challenged by short instrumental records and long recurrence intervals the m6 2 1935 timiskaming earthquake is the largest recorded to date and was felt over some 1 3 million km 2 of eastern north america with many aftershocks of magnitude 4 to 5 its epicenter lies below the western margin of lake kipawa quebec in the area where a major proterozoic crustal boundary the grenville front tectonic zone crosses the timiskaming graben a high resolution chirp seismic reflection survey of the lateglacial and postglacial sediment infill of lake kipawa reveals a clear record of recent ground shaking that is attributed to the 1935 earthquake widespread large slumps record down slope failure of the lateglacial and postglacial sediment fill indicating that the 1935 temblor was the largest in this area since deglaciation some 8000 years ago systematic mapping of landslides shows that they extend across an area of 600 km 2 around the earthquake s epicenter lakes cover a large area of eastern canada a regional scale survey of lake floors could constrain historic epicenters and postglacial seismic history of the heavily populated wqsz

detailed seismic stratigraphy of lago puyehue implications for the mode and timing of glacier retreat in the chilean lake district lago puyehue is a glacigenic lake in the chilean lake district 40 s with a complex deglaciation history a detailed seismic stratigraphic study of its sedimentary infill indicates a much earlier retreat of the glacier from the lago puyehue basin than the neighbouring glacier from the lago rupanco basin because of their close proximity rupanco meltwater streams played an important part in the depositional processes of lago puyehue a timing discrepancy between the in lake ages of a sediment core and the outer lake ages of moraine deposits re opens the discussion on the timing of deglaciation in the southern hemisphere copyright 2011 john wiley sons ltd

late quaternary evolution of lago castor chile 45 6 s timing of the deglaciation in northern patagonia and evolution of the southern westerlies during the last 17 kyr abstract even though patagonia is ideally located to study climate of the southern mid latitudes many questions on the late quaternary climate evolution remain unresolved the timing of maximum glacier extent is still uncertain in vast areas and the postglacial evolution of the southern westerly wind belt swwb remains highly debated here we study the sedimentary infill of a glacigenic lake lago castor 45 6 s 71 8 w located at the leeside of the andes in chilean patagonia to i reconstruct the deglacial evolution of the eastern flank of the patagonian ice sheet pis and ii discuss postglacial changes in wind strength at a critical location where westerly wind records are critically lacking a dense grid of high resolution reflection seismic data was used to reconstruct the large scale infill history of the lake and a radiocarbon dated sediment core penetrating all lacustrine seismic units was retrieved results indicate that the deglaciation of the lake basin and its catchment occurred no later than 28 cal kyr bp i e an early lgm but possibly even already after mis 4 afterwards the lago castor area was covered by a large proglacial lake that drained possibly through an outburst flood when the pis outlet glaciers retreated to a critical location subsequently very dry conditions caused the lake to desiccate as evidenced by an unconformity visible on the seismic profiles and in the sediment core this dry period likely resulted from the increased orographic effect of the pis covered andes accompanied by weaker westerlies from 20 kyr bp onwards the combination of a shrinking pis and a southward shift of the swwb resulted in increased precipitation which caused the lake level to rise after 17 cal kyr bp lake sedimentation was more directly influenced by the southern westerlies with the formation of sediment drifts resulting from strong bottom current during periods of intense westerly winds our results suggest a progressive increase in wind strength at 46 s from 11 2 to 4 5 cal kyr bp which supports the hypothesis that the swwb broadened during the early and middle holocene

evidence for an early glacial maximum in the french vosges during the last glacial cycle the last glacial maximum is observed to have occurred between 18 000 and 20 000 years ago throughout northern europe here we present evidence for the surprising result that in the region of the french vosges the regional ice sheet advanced during the early part of the last glacial cycle and this expansion was considerably larger than that which occurred during the last glacial maximum from these results we conclude that the glacial maximum may not have occurred at the same time worldwide contrary to what has usually been assumed1

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

palaeogeographical relationships between alpine and jura glaciers during the two last pleistocene glaciations abstract two main moraine complexes are usually defined in the northwestern alpine piedmont the external moraine complex emc dated to the penultimate glaciation riss sensu lato and the internal moraine complex imc dated to the last glaciation wurm until recently the prevalent concept was that these two complexes had been built by glaciers originating in the central alpine zone this paper presents a new palaeogeographical diagram based on mapping and petrographical studies of these two moraine complexes and especially on the relationships between alpine and jura tills we reach the following conclusions 1 1 the jura glaciers were independent of the alpine glaciers during the two last pleistocene glaciations 2 2 the jura mountains formed a topographical barrier blocking and modifying the alpine glacier advance towards the northwest with the result that during the wurmian glaciation the maximum elevation 1200 m a s l of the alpine glaciers on the eastern margin of the jura was too low to allow alpine ice to enter the jura and during the rissian glaciation the greater thickness of the alpine glaciers resulted in their penetration only into the lower marginal zone of the jura 3 3 thus in the studied area the central alps were not the only centre of ice dispersal during the two last pleistocene glaciations on the northwestern jura slopes the corresponding moraine complexes were mainly built by glaciers emanating from the central jura

push moraines and glacier contact fans in marine and terrestrial environments the local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts which in turn determine the sediments and landforms produced at the glacier front many modern glaciers undergoing overall retreat in areas of maritime climate produce winter push moraines during a late winter readvance followed by a summer retreat whilst in more continental regions no significant winter readvance occurs and annual push moraines are absent the frontal dynamics which lead to these changes are analysed and the form structure sequence and field relations of both terrestrial and marine push moraines are described from iceland spitsbergen and baffin island long term changes in mass balance leading to major glacier advances or readvances also generate large push moraines in terrestrial environments push moraine formation is accompanied by uplift rejuvenation and down cutting of outwash systems whose sediments become closely associated with glaciotectonic structures which permit pre syn and post tectonic sequences to be identified the development of ice marginal fan moraine complexes is modelled as a function of the relative magnitude of two parameters the velocity of ice movement and the calving rate a high ice velocity just exceeded by the calving rate gives closely spaced push moraines and confluent ice marginal fans a high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans a low ice velocity in combination with a high calving rate results in well separated and feebly developed push moraines while a low ice velocity and a low calving rate produces feeble push moraines and coalescent fans

nearly contemporaneous evolution of the a and s type fractionated granites in the krusne hory erzgebirge mts central europe abstract the krusne hory erzgebirge mountains is one of the best known provinces of granite magmatism and associated metallogenesis in europe variscan magmatic activity in the krusne hory erzgebirge area spanned the period from 330 to 295 ma for much of this time two types of magma were generated and emplaced in close proximity in this province strongly peraluminous p rich s type melts were formed alongside slightly peraluminous p poor melts a type two suites of strongly peraluminous p f li rb cs u sn rich and zr th y hree poor magmas were intruded in rapid succession over a period of about 10 ma about 330 320 ma over the entire region of the krusne hory several peraluminous rhyolitic dykes near gottesberg mark an isolated event at about 295 ma slightly peraluminous f li rb cs sn zr y hree rich and p poor magmas were intruded in several events separated in space and time 325 295 ma both magmatic episodes culminated with strongly fractionated subvolcanic granite intrusions accompanied by explosive brecciation and followed by sn w mineralization of greisen type successive volcanic eruption of rhyolites and dacites of s type and rhyolites of a type form the fill of the altenberg teplice caldera atc thus demonstrating the close temporal and spatial relationship between these two types of magma when these two geochemically distinct types of rock are in direct contact then the rocks of a type are always younger the absolute time difference between the two types can range from less than 1 ma the first eruption of the teplice rhyolite versus the schonfeld dacite in the atc to about 15 ma eruption of rhyolites at gottesberg versus emplacement of the eibenstock granite the assumed protolith of all late variscan granites in the area of krusne hory erzgebirge is a mixture of fertile quartzo feldspathic rocks with micaceous metapelites enriched in lile and sn w the differences in chemical composition of s and a type melts originated from local changes in the proportion of quartzo feldspathic and pelitic lithologies different pt conditions of melting the degree of melting and the degree of metamorphic dehydratation of the protolith prior to the melting

conditions of pocket formation in the oktyabrskaya tourmaline rich gem pegmatite the malkhan field central transbaikalia russia coexisting melt mi fluid melt fmi and fluid fi inclusions in quartz from the oktaybrskaya pegmatite central transbaikalia have been studied and the thermodynamic modeling of pvtx properties of aqueous orthoboric acid fluids has been carried out to define the conditions of pocket formation at room temperature fmi in early pocket quartz and in quartz from the coarse grained quartz oligoclase host pegmatite contain crystalline aggregates and an orthoboric acid fluid the portion of fmi in inclusion assemblages decreases and the volume of fluid in inclusions increases from the early to the late growth zones in the pocket quartz no fmi have been found in the late growth zones significant variations of solid fluid ratios in the neighboring fmi result from heterogeneous entrapment of coexisting melts and fluids by a host mineral raman spectroscopy sem eds and empa indicate that the crystalline aggregates in fmi are dominated by mica minerals of the boron rich muscovite nanpingite csal2 alsi3o10 oh f 2 series as well as lepidolite topaz quartz potassium feldspar and several unidentified minerals occur in much lower amounts fluid isolations in fmi and fi have similar total salinity 4 8 wt nacl eq and h3bo3 contents 12 16 wt the melt inclusions in host pegmatite quartz homogenize at 570 600 c the silicate crystalline aggregates in large inclusions in pocket quartz completely melt at 615 c however even after those inclusions were significantly overheated at 650 10 c and 2 5 kbar during 24 h they remained non homogeneous and displayed two types i glass unmelted crystals and ii fluid glass the fmi glasses contain 1 94 2 73 wt f 2 51 wt b2o3 3 64 5 20 wt cs2o 0 54 wt li2o 0 57 wt ta2o5 0 10 wt nb2o5 0 12 wt beo the h2o content of the glass could exceed 12 wt such compositions suggest that the residual melts of the latest magmatic stage were strongly enriched in h2o b f cs and contained elevated concentrations of li be ta and nb fmi microthermometry showed that those melts could have crystallized at 615 550 c crystallization of quartz feldspar pegmatite matrix leads to the formation of h2o b and f enriched residual melts and associated fluids prototypes of pockets fluids of different compositions and residual melts of different liquidus solidus p t conditions would form pockets with various internal fluid pressures during crystallization those melts release more aqueous fluids resulting in a further increase of the fluid pressure in pockets a significant overpressure and a possible pressure gradient between the neighboring pockets would induce fracturing of pockets and fluid explosions the fracturing commonly results in the crushing of pocket walls formation of new fractures connecting adjacent pockets heterogenization and mixing of pocket fluids such newly formed fluids would interact with a primary pegmatite matrix along the fractures and cause autometasomatic alteration recrystallization leaching and formation of primary secondary pockets

the role of magmatic and hydrothermal processes in the evolution of be bearing pegmatites evidence from beryl and its breakdown products beryl and euclase crystals from the mina do santino and the jacu pegmatites in the borborema pegmatite province in northeastern brazil contain several generations of melt and fluid inclusions which allow interpretation of p t x conditions responsible for beryl crystallization and for alteration of a primary pegmatitic mineral assemblage to a mixture of hydrothermal minerals euclase bertrandite kaolinite and quartz primary melt and fluid inclusions hosted by beryl were trapped simultaneously however their homogenization temperatures are significantly higher 870 900 c than the values previously reported for pegmatitic systems 712 c and should be treated with caution an isobaric drop of temperature resulted in the exsolution of a fluid a low salinity co2 enriched phase and a saline water rich phase were trapped in pseudosecondary inclusions in beryl at a pressure of 2 1 2 7 kbar and temperature of 390 480 c cooling of the country rocks below 400 c caused a ductile to brittle transition and allowed infiltration of cold groundwater which further decreased the temperature in the system to 190 240 c at the same time the pressure dropped from a lithostatic 2 1 2 7 kbar to a hydrostatic value 0 57 0 73 kbar consequently minerals deposited under magmatic conditions feldspars and beryl became unstable and a newly formed hydrothermal mineral paragenesis euclase bertrandite kaolinite and quartz overprinted the earlier one the hydrothermal fluids responsible for the alteration differ from the earlier exsolved fluids in having a lower salinity lower homogenization temperature the absence of co2 and the presence of ch4

dating multiply overprinted sn mineralized granites examples from the erzgebirge germany granites and primary tin mineralization in the erzgebirge were dated using 1 conventional u pb dating of uraninite inclusions in mica 2 rb sr dating of inclusions in quartz that represent highly evolved melts 3 re os dating of magmatic hydrothermal molybdenite and 4 chemical th u pb dating of uraninite conventional isotope dilution and thermal ion mass spectrometry and chemical th u pb dating of uraninite in granites from the ehrenfriedersdorf mining district provide ages of 323 9 3 5 ma 2 greifenstein granite and 320 6 1 9 and 319 7 3 4 ma 2 both sauberg mine in agreement with u pb apatite ages of 323 9 2 9 and 317 3 1 6 ms 2 both sauberg mine rb sr analysis of melt inclusions from zinnwald gives highly radiogenic sr isotopic compositions that with an assumed initial sr isotopic composition permit calculation of precise ages from single inclusions the scatter of the data indicates that some quartz hosted melt inclusions have been affected by partial loss of fluid exsolved from the melt inclusion re os dating of two molybdenite samples from altenberg provides ages of 323 9 2 5 and 317 9 2 4 ma 2 together with age data from the literature our new ages demonstrate that primary tin mineralization and the emplacement of the large sn specialized granites in the erzgebirge fall in a narrow range between 318 and 323 ma primary sn mineralization occurred within a short interval during post collisional collapse of the variscan orogen and was essentially synchronous over the entire erzgebirge in contrast to earlier claims no systematic age difference between granites of the eastern and western erzgebirge was established furthermore our data do not support a large age range for late variscan granites of the erzgebirge 330 290 ma as has been previously suggested

implications of thermally induced fracture slip and permeability change on the long term performance of a deep geological repository abstract this paper addresses thermally induced shear slip i e thermoshearing and changes in permeability of a deep geological repository in large scale we present a systematic examination of the thermal stress expected to be generated in the far field around the repository the main mechanisms for generation of thermal stress that can affect permeability are comparatively high horizontal compressive thermal stress at the repository level vertical tensile thermal stress right above the repository and horizontal tensile stress near the surface and shear stress at the corners of the repository based on thermal loading history probabilistic shear slip analysis was conducted to investigate the possibility of thermoshearing higher probability of shear slip is expected with higher differential thermal stress and this was highly affected by fracture orientations stress paths obtained from the thermo mechanical analysis were used as stress boundary conditions for discrete fracture network discrete element method dfn dem analysis to investigate the effect of stress changes on permeability in four out of the six dfn models normal deformation dominated the closure and opening of fractures with shear dilation being the dominant factor in the other two models changes in permeability caused by shear dilation were not reversed after the repository cooled which is explained by the irreversible fracture shear deformation after shear slip this study was conducted on data from the forsmark site in sweden and this analysis has implications for sites that have comparatively large horizontal in situ stresses and relatively few fractures

monitoring the crystallization of water saturated granitic melts in real time using the hydrothermal diamond anvil cell critical aspects of the crystallization dynamics of h2o saturated melts of a typical granitic composition as well as granitic melts enriched in lithium 8800 ppm were investigated in real time experiments using the hydrothermal diamond anvil cell at 480 700 c and 220 960 mpa complete crystallization of the charges was achieved within 5 118 h with average crystal growth rates ranging from 3 to 41 cm year for quartz and from 18 to 58 cm year for alkali feldspars demonstrating that crystals formed from a silicate melt in the presence of a coexisting aqueous phase crystallize rapidly the combination of substantial nucleation delays low nucleation densities and rapid growth rates for quartz and alkali feldspars led to the formation of euhedral megacrysts of these minerals in the vicinity of clusters comprised of much smaller muscovite or spodumene crystals subsolidus replacement processes initiated during crystal fluid interactions after the silicate melt was consumed were directly observed in the experiments the experimental results underscore the important role of water as a medium for the transport of essential elements such as si al na and k from the silicate melt to the newly formed crystals and provide important insights into the crystallization of miarolitic pegmatites

high resolution seismic reflection profiling of neotectonic faults in lake timiskaming timiskaming graben ontario quebec canada the timiskaming graben is a 400 km long 50 km wide north west trending morphotectonic depression within the canadian shield of eastern north america and experiences frequent intraplate earthquakes the graben extends along the border of ontario and quebec connecting southward with the nipissing and ottawa bonnechere grabens and the st lawrence rift system which includes a similar structure underlying the hudson valley of the eastern usa together they form a complex failed rift system related to regional extension of north american crust during the breakup of rodinia and later pangea the timiskaming graben lies within a belt of heightened seismic activity western quebec seismic zone with frequent moderate magnitude greater than magnitude 5 earthquakes including a magnitude 6 2 in 1935 these events threaten aging urban infrastructure built on soft glacial sediments post glacial landslides along the ottawa valley suggest earthquakes as large as magnitude 7 the inner part of the timiskaming graben is filled by lake timiskaming a large 110 km long post glacial successor to glacial lake barlow that was ponded by the laurentide ice sheet 9500 years ago the effects of frequent ground shaking on lake floor sediments was assessed by collecting more than 1000 line kilometres of high resolution chirp seismic profiles late glacial lake barlow glaciolacustrine and overlying post glacial sediments are extensively deformed by extensional faults that define prominent horsts and grabens multibeam bathymetry data suggest that faults influence the morphology of the modern lake floor despite high sedimentation rates and indicate recent neotectonic deformation the lake timiskaming area provides evidence of post glacial intracratonic faulting related to recurring earthquake activity along a weak spot within the north american plate

crystallization conditions and evolution of magmatic fluids in the harney peak granite and associated pegmatites black hills south dakota evidence from fluid inclusions abstract a microthermometric study of inclusions in granites and pegmatites in the proterozoic harney peak granite system identified four types of inclusions type 1 inclusions are mixtures of co2 and h2o and have low salinities on average 3 5 wt nacleq type 2 inclusions are aqueous solutions of variable salinities from 0 to 40 wt nacleq type 3 inclusions are carbonic dominated by co2 with no detectable water and type 4 inclusions consist of 20 to 100 solids with the remaining volume occupied by a co2 h2o fluid many inclusions have a secondary character however a primary character can be unambiguously established in several occurrences of the type 1 inclusions these inclusions were trapped above the solidus and represent the exsolved magmatic fluid the secondary populations of types 1 2 and 3 probably formed as a result of reequilibration and unmixing of the type 1 fluid that progressively changed composition and density with decreasing temperature and pressure and was finally trapped along healed microfractures under subsolidus conditions type 4 inclusions are primary and are interpreted to be trapped fluid bearing complex silicate melts that subsequently solidified or underwent other posttrapping changes it is demonstrated that primary type 1 fluid inclusions that coexist with crystallized melt inclusions in the complex li bearing tin mountain pegmatite were trapped along the two fluid phase boundary in the system co2 h2o nacleq consequently the temperature and pressure conditions of trapping are identical to the bulk homogenization conditions on average 340 c and 2 7 kbar these conditions indicate that this li cs rb p and b rich pegmatite crystallized at some of the lowest known temperatures for a silicate melt in the crust an internally consistent empirical solvus surface in p t xco2 coordinates was generated for the pseudobinary co2 h2o 4 3 wt nacleq pegmatite fluid system distribution coefficients for the major species co2 h2o nacl and ch4 between the immiscible co2 rich and h2o rich fluid phases as a function of pressure and temperature were extracted from data for the two cogenetic fluid inclusions types

late quaternary lacustrine paleo seismic archives in north western alps examples of earthquake origin assessment of sedimentary disturbances abstract the late quaternary sedimentary fills of several lakes of the north western alps are revealed to be possible paleo seismological archives in a moderately active seismo tectonic region the strongest historically reported events can be correlated with specific layers whose textures result from different processes i mass failures of sub aqueous slope deposits especially delta foresets evolving into hyperpycnal currents influenced by seiche effects and or multiple reflections on lake basin slopes ii in situ liquefaction and flowage and iii micro fracturing based on identification of the sedimentary signature of a well documented historical earthquake the paleoseismic interpretation can be extrapolated back to 16 000 yrs bp with a reconstruction of a time series and textural identification of slope failure related turbidites the most frequent earthquake signature the obtained time series are compatible with historical seismicity in terms of recurrence interval

late quaternary morphostratigraphy of lake st joseph southeastern canadian shield evolution from a semi enclosed glacimarine basin to a postglacial lake abstract this paper reports and describes multibeam echosounder subbottom profiler and sediment sampling data collected in lake st joseph southern quebec a formerly glacimarine sedimentary basin that has been glacio isostatically uplifted to form a small lake its study provides a unique opportunity for investigating changes in sedimentary environments from a glacial sea to a postglacial lake multibeam bathymetry allows the observation of two basins separated by a bathymetric ridge and of mass movement deposits in both basins high resolution seismic stratigraphy reveals the presence of seven seismic units these seven units relate to the advance and retreat of the laurentide ice sheet over the region following ice retreat transparent u3 and high amplitude reflection u4 units were deposited during the champlain sea invasion the transparent unit likely represents a rapidly retreating glacier which allowed the deposition of massive silt and clay whereas the high amplitude reflectors which are internally composed of transparent to chaotic lenses are interpreted as the result of a deceleration of ice retreat or a stabilization of the glacier and of glacio isostatic rebound overlying the champlain sea sediments a unit composed of smaller laminations u5 suggests that it was deposited during the marine to lacustrine transition in a paraglacial environment this is supported by its presence in the northern basin where the riviere aux pins mouth is located and its absence in the southern basin where no river is observed the bathymetric ridge between the two basins thus limited sediment transport following the complete retreat of the champlain sea organic rich sediments u7 were deposited in the lake in the northern basin the presence of the riviere aux pins allowed their deposition in the form of rhythmites whereas the absence of rivers in the southern basin resulted in the deposition of an acoustically transparent unit a mass movement u6 identified during the deposition of unit 7 occurred around 1250 ad and is interpreted as earthquake triggered

high resolution seismic stratigraphy of late quaternary fill of lake annecy northwestern alps evolution from glacial to interglacial sedimentary processes abstract lake annecy is a peri alpine lake of glacial origin remnant of the last glaciation the lake basin accumulated over 150 m of sediment since the last glacial maximum a dense grid of high resolution seismic data acquired during a 1993 sparker survey revealed the glacial and post glacial sedimentary infill the depth and morphology of the wurm erosion surface and penetrated the riss wurm interglacial deposits as deep as the underlying riss erosion surface this paper focuses on the interpretation of the high resolution seismic facies of the infilling sediments of the lake basin in correlation with the results of the annecy core the quality and density of the seismic data allow in this case detailed analysis of the seismic facies in their three dimensional organisation and permit reliable interpretation in terms of depositional process and palaeo environmental setting the study reveals that the geometry and seismic facies of the infilling deposits are controlled essentially by the basin morphology and the characteristics of the sediment supply the sediment supply to the lake changes throughout the deglaciation from subglacial drainage to proglacial meltwater streams to alluvial streams and finally to the present day interglacial condition where authigenic sedimentation prevails the depositional patterns change accordingly from chaotic outwash deposits and glacio lacustrine muds at the base over axially aggrading lacustrine fans prograding alluvial fan deltas at the lake margins to finally a drape of lacustrine chalk and marl the interpreted sedimentary environment and deduced character of the sediment source are used to reconstruct the changing palaeo environment in the catchment area

geophysical surveys of the sediments of loch ness scotland implications for the deglaciation of the moray firth ice stream british irish ice sheet we present results from three geophysical campaigns using high resolution sub bottom profiling to image sediments deposited in loch ness scotland sonar profiles show distinct packages of sediment providing insight into the loch s deglacial history a recessional moraine complex in the north of the loch indicates initial punctuated retreat subsequent retreat was rapid before stabilisation at foyers rise formed a large stillstand moraine here the calving margin produced significant volumes of laminated sediments in a proglacial fjord like environment subsequent to this ice retreated rapidly to the southern end of the loch where it again deposited a sequence of proglacial laminated sediments sediment sequences were then disturbed by the deposition of a thick gravel layer and a large turbidite deposit as a result of a jo kulhlaup from the spean roy ice dammed lake these sediments are overlain by a holocene sheet drape data indicate i a former tributary of the moray firth ice stream migrated back into loch ness as a major outlet glacier with a calving margin in a fjord like setting ii there was significant sediment supply to the terminus of this outlet glacier in loch ness and iii that jo kulhlaups are important for sediment supply into proglacial fjord lake environments and may compose 20 of proglacial sedimentary sequences

origin of miarolitic pegmatites in the konigshain granite lusatia abstract in this study we examine an interesting occurrence of miarolitic pegmatites in the konigshain granite of the lusatia region of the bohemian massif this granite is characterized by the extensive development of micro sized miarolitic pegmatites typically with diameters of 5 to 15 mm irregularly distributed through its upper levels and larger miarolitic pegmatites up to 1 m in the uppermost levels this granite also shows evidence of varied forms of transport of extremely volatile rich residual melts fluids in the form of more or less discrete inter granular melt bodies and associated magmatic quartz veins formed in tectonic fissures together these provide evidence for the origin of miarolitic pegmatites both in the specific case of konigshain and more generally our evidence suggests that miarolitic pegmatites form from volatile and alkali rich residual melts ranging from 10 to 50 h 2 o far more than typical granitic melts but far more silicate components than aqueous fluids or vapor suggested by some authors using melt inclusions in quartz from the aplitic and graphic granite zones in miarolitic pegmatites in the konigshain granite we show that two different inclusion populations are present we provide evidence that the first inclusion population are those related to the primary granite at the level of intrusion and the second were trapped during the re crystallization of the granite wall rocks by silicate rich supercritical fluids moving through the solid crystal framework with a porosity 0 see clarke et al 2013 our results show that a significant volume fraction of the miarolitic pegmatites was not created by a pegmatite forming fluid but formed in situ by re crystallization of wall rocks triggered by highly reactive volatiles exsolved from the pegmatite forming melts evidence is also presented which suggests the nature and speed of emplacement of the konigshain granite this evidence may explain the unusual form and abundance of miarolitic pegmatites in the studied area and may have application to similar occurrences thus there is a mixture of features which are applicable to miarolitic pegmatites in general and others which help separate the overriding processes from the variations produced by local or regional chemical or tectonic characteristics

high resolution seismic stratigraphy of glacial to interglacial fill of a deep glacigenic lake lake le bourget northwestern alps france abstract lake le bourget is a deep peri alpine glacial lake originating from the last glacial the wurm the lake has amassed over 250 m of sediment since the last glacial maximum two seismic sparker surveys on the lake revealed the glacial and post glacial sedimentary infill the depth and the morphology of the wurm erosion surface and penetrated the riss wurm interglacial deposits as deep as the underlying riss erosion surface the density of the seismic grid and the high resolution of the data even at greater depths allowed a detailed study of the sedimentary processes and of their evolution throughout the deglaciation five main seismic facies characterise the basin fill they are interpreted as glacial deposits glacio lacustrine sediments proglacial lacustrine fans alluvial fan deltas and authigenic lacustrine drape these occur as a suite of deposits associated with the major lake tributaries and are the result of major changes in sediment supply and style of discharge into the lake the three dimensional facies associations within the basin fill document the history of the basin and its catchment area since the onset of the deglaciation

wurmian deglaciation of western lake geneva switzerland based on seismic stratigraphy abstract western lake geneva le petit lac was filled during the quaternary over a major erosion surface truncating the cemented folded and thrusted tertiary sediments of the foreland alpine basin the carving of the lake occurred during quaternary glaciations with ice originating from the rhone valley catchment basin flowing in two branches oriented sw and ne over the swiss plateau lake geneva is situated on the south western branch of this paleo ice cap for the first time a dense grid of high resolution seismic profiles airgun 5 inch3 airgun 1 inch3 and echosounder has imaged the whole quaternary sequence providing a paleoenvironmental interpretation and a detailed reconstruction of the rhone glacier retreat stages during glacial events that led to the formation of western lake geneva the quaternary sequence filling up the bedrock valley is exceptionally thick with up to 220 m of deposits and consists of glacial glacio lacustrine and lacustrine sediments fourteen seismic units have been defined units u1 u14 unit u1 represents the remnants of glacial deposits older than the last glacial cycle preserved in the deepest part of the lake and in secondary bedrock valleys unit u2 represents gravel and sands deposited by meltwater circulation at the bottom of the glacial valley unit u3 is a thick stratified unit marking the beginning of the deglaciation when the rhone glacier became thinner and buoyant and allowed the formation of a subglacial lake younger glacial units units u4 u5 u7 u9 u11 are acoustically chaotic sediments deposited subglacially under the water table undermelt tills while the glacier was thinning these glacial units are bounded by synform erosion surfaces corresponding to readvances of the glacier the transition from a glacial to a glacio lacustrine environment started with the appearance of a marginal esker fan system unit u6 esker formation was followed by a small advance retreat cycle leading to the deposition of unit u7 then the ice front receded and stratified sediments were deposited in a glacio lacustrine environment units u8 u10 and u12 this retreat was punctuated by two readvances coppet unit u9 and nyon unit u11 producing large push moraines and proglacial debris flows finally a lacustrine environment with a characteristic lake current pattern and mass movement deposits took place units u13 and u14 except for unit u1 the sedimentary sequence records the wurmian deglaciation in a fjord like environment occupied by a tidewater glacier with a steep calving ice front the presence of an esker fan system reveals the importance of subglacial meltwater flow in continental deglaciation push moraines and erosion surfaces below the glacier indicate at least 5 readvances during the deglaciation thus revealing that oscillations of ice front are the key process in deglaciation of perialpine fjord lakes the dating of these continental glacier fluctuations would allow correlation with oceanic and ice records and help to understand the climatic mechanisms between oceans and continents

post last glacial maximum evolution of a fjord type lake based on high resolution seismic data the lago roca acigami southern tierra del fuego argentina chile

spheroidal textures in igneous rocks textural consequences of h2o saturation in basaltic melts abstract when melts reach h 2 o saturation before they are emplaced at the earth s surface they exsolve a hydrous fluid phase at elevated pressure and high temperature a hydrous fluid is not pure h 2 o but can contain some quantities of silicate and metal oxide solute notably if fluid saturation occurs at high pressure chemically and physically fluid saturated basalts behave like any other system with liquid immiscibility textures that can result after solidification are globules of former fluid dispersed in a former silicate melt or silicate melt orbs embedded in a former fluid matrix the troodos ophiolite on the island of cyprus generated in a back arc basin above a wet intra oceanic subduction zone carries in its magmatic stratigraphy lithologies distinctly orbicular and globular in shape many melt compositions parental to the ophiolite were h 2 o saturated near their liquidus temperatures before they reached their depths of emplacement within the ophiolite sequence spheroids are not uncommon in magmatic rocks but still debated as to how they form we propose that globular and orbicular textures in igneous worldwide may result when melts reach h 2 o saturation and exsolve an immiscible solute bearing h 2 o dominated fluid phase at elevated temperature and pressure before or while they are emplaced

deposition in an esker bead and fan complex lanark ontario canada abstract a glaciofluvial landform complex comprising a single esker ridge proximally multiple ridges and beads in the middle section and a complex of ridges and fans distally is mapped and described we present detailed successions in the associated sediment showing sedimentary structure grain size and palaeocurrent estimates sediment in the esker is mainly coarse grained and varies from boulders with a fine sand matrix deposited at maximum discharges to diamicton interpreted as a product of ice pressing under low discharges early stage deposition in the esker at high flow was from suspension and bed load intermediate stage deposition was mainly from bed load and late stage deposition was from hyperconcentrated suspension the esker rests in a bedrock channel which functioned as a nye channel prior to esker formation the channel surface carries a variety of fluvial erosional marks short distributary ridges of the ridges and beads complex contain mainly cobbles and boulders but beads are mainly in sand with rapid down flow fining and change in sedimentary structure faulting and overfolding of bead sediment suggest a subglacial origin deposition of the esker fan complex was highly variable in space and time down fan sedimentary changes with transitions from gravel to cross laminated fine sand in a few tens of metres indicate rapid loss in competence fan location lateral to the esker indicates a broadening of the zone of subglacial meltwater with time deposition from suspension and steep sided scours are interpreted to result from deposition and erosion by hyperconcentrated flows a model of underflows with submerged hydraulic jumps spilling laterally from the esker tunnel into subglacial cavities explains the morphological and sedimentary characteristics of the fans detailed analysis of small scale fining upwards sequences in the fans and beads indicates deposition by a large number of flow events these events are explained by glacier hydraulics whereby periodic separation of the glacier from its bed caused water with a high suspended sediment concentration to spill out from the esker tunnel into adjacent subglacial cavities evolution of the subglacial drainage system indicates a complexity of subglacial sedimentation near to a grounding line which is not readily apparent from observations at modern glaciers terminating in relatively deep water

thermal response of a canadian conceptual deep geological repository in crystalline rock and a method to correct the influence of the near field adiabatic boundary condition abstract this paper describes the thermal performance of a conceptual deep geological repository dgr involving a container for used candu fuel and its placement concept in crystalline rock for numerical reasons separate near field and far field models are usually used to model a dgr in the near field models an adiabatic thermal condition is applied on the four vertical outside boundaries and as such this represents a repository with an infinite horizontal dimension the results from such models are known to be accurate at early times with the thermal response overestimated at longer times to examine the influence of this boundary condition a simplified near field model is built using comsol and a method is developed to account for boundary condition effects the method is validated by comparing the modified comsol results with a theoretical solution produced using hotrok the proposed method can be used in thermal modelling of a used fuel dgr to obtain accurate results as long as the horizontal dimension of the near field unit cell is very small compared to the repository panel horizontal dimension e g less than one tenth of the panel dimension

a subaquatic moraine complex in overdeepened lake thun switzerland unravelling the deglaciation history of the aare glacier abstract to investigate the history of the aare glacier and its overdeepened valley a high resolution multibeam bathymetric dataset and a 2d multi channel reflection seismic dataset were acquired on perialpine lake thun switzerland the overdeepened basin was formed by a combination of tectonically predefined weak zones and glacial erosion during several glacial cycles in the deepest region of the basin top of bedrock lies at 200 m below sea level implying more than 750 m of overdeepening with respect to the current fluvial base level i e lake level seismic stratigraphic analysis reveals the evolution of the basin and indicates a subaquatic moraine complex marked by high amplitude reflections below the outermost edge of a morphologically distinct platform in the southeastern part of the lake this stack of seven subaquatic terminal moraine crests was created by a fluctuating quasi stagnant grounded aare glacier during its overall recessional phase single packages of overridden moraine crests are seismically distuinguishable which show a transition downstream into prograding clinoforms with foresets at the ice distal slope the succession of subaquatic glacial sequences foresets and adjacent bottomsets represent one fifth of the entire sedimentary thickness exact time constraints concerning the deglacial history of the aare glacier are very sparse however existing 10be exposure ages from the accumulation area of the aare glacier and radiocarbon ages from a late glacial lake close to the outlet of lake thun indicate that the formation of the subaquatic moraine complex and the associated sedimentary infill must have occurred in less than 1000 years implying high sedimentation rates and rapid disintegration of the glacier these new data improve our comprehension of the landforms associated with the ice contact zone in water the facies architecture of the sub to proglacial units the related depositional processes and thus the retreat mechanisms of the aare glacier

experimental study of boron solubility and speciation in the na2o b2o3 sio2 h2o system abstract the na2o b2o3 sio2 h2o system has been studied at 520 c and 1 5 kbar in order to understand boron solubility and speciation under hydrothermal conditions at different sodium content within the studied compositional range excess of sio2 na2o 0 5 8 wt b2o3 3 5 6 7 wt and h2o 50 5 68 2 wt the system contains three phases aqueous fluid quartz and borosilicate liquid at na2o raman spectroscopy has not detected known sodium borate and borate polyanionic meta ortho tri tetra and pentaborate species in inclusions from all experiments within 20 400 c dissolved orthoboric acid line 876 cm 1 was the only raman spectral feature determined in fluid inclusions within the region typical for aqueous borate species 500 1200 cm 1 high temperature raman spectroscopy along with microthermometrical data suggests that a significant part of boron in the fluid and borosilicate liquid at the experimental temperature and pressure is bonded to sodium borosilicate species it was shown that boron has no significant effect on the phase relations within the studied part of the system na2o b2o3 sio2 h2o and under the studied conditions the system can be regarded as na2o sio2 h2o to a first approximation the obtained experimental data show that under natural hydrothermal conditions slightly alkaline aqueous fluids can transport significant amounts of boron and silica far away from the hydrothermal fluid source on the other hand in natural systems with relatively high alkalinity one can expect that boron does not migrate too far from the fluid source and being accumulated in the borosilicate liquid will form borosilicate mineralization at appropriate conditions

laser raman spectroscopic measurements of water in unexposed glass inclusions a method is proposed for determining the water concentration in silicate melt inclusions mi by confocal micro raman spectroscopy without exposing the inclusions for measurement a prerequisite of all previous methods the latter is important for extremely water rich mi e g those in evolved granites and pegmatites which would loose h2o on exposure furthermore this technique permits determination of the water concentration in a single mi we use a comparative technique determining the total water content of a sample against a reference glass of known water content because this process is non destructive it does not preclude the subsequent use of other analytical techniques

a boundary element formation for three dimensional thermo elasticity of a semi infinite space with buried decaying heat sources abstract the nuclear waste disposal project involves thermo mechanical interactions in rock induced by buried decaying heat sources to satisfy the condition of zero stress on ground surface mirror heat sinks and boundary solutions are used specifically mirror heat sinks are aimed at removing normal tractions at ground surface generated by heat sources and boundary solutions are intended for handling residual tangential stresses on ground surface caused by heat sinks and heat sources multitudes of rectangles are employed to discretize the ground surface under the assumption of evenly distributed shear loads over a rectangular element an analytical formula about the influence coefficient is derived simplifying cylindrical canister heat sources into finite line ones a repository scale model for evaluating the thermo elastic response of rock is proposed given a conceptual nuclear waste repository the temperature increment thermal stress and displacement of surrounding rock are investigated the results demonstrate that the present model provides an efficient tool to analyze the thermo mechanical response of a geologic repository with different heat loading patterns

the record of density induced underflows in a glacial lake as part of an overall study of sedimentation processes in a proglacial lake an effort was made to compare field results with some of the general equations for density flows the results suggest that in relatively small glacial lakes the occurrence of underflows with lower sediment loads involves a complex interplay between thermal and sediment effects which is extremely sensitive to varying hydrologic and climatic conditions in terms of actual transport mechanics the results i indicate that a higher value of 0 6 or 0 7 gives a closer agreement between the measured velocity values and the established equations on moderately shallow slopes ii provide field support for the experimentally derived relationship of britter linden 1980 for the velocity of underflows and suggest the equation may be applicable in situations below 5 slopes and iii support the relationship between velocity of the front and body of a continuous underflow for moderate slope situations suggested by middleton 1966b finally the velocity values measured by electromagnetic current meters stationed in the lake the grain size data obtained from mapping core data and the application of other criteria support the concept that in this environment the underflows are capable of erosion

crystallization of alpo4 sio2 solid solutions from granitic melt and implications for p rich melt inclusions in pegmatitic quartz aluminum orthoposphate alpo 4 has polymorphs isostructural with tridymite cristobalite and quartz berlinite is the low temperature form that corresponds to quartz we report berlinite quartz solid solutions to crystallize from a synthetic p rich peraluminous granitic melt similar in composition to the most volatile rich silicate melt inclusions found in pegmatites the crystallization took place in experiments performed in cold seal pressure vessels at 450 700 c and 0 1 0 2 gpa h 2 o pressure at these conditions the berlinite quartz mutual solubility is limited to 5 7 mol sio 2 on the phosphate side of the solvus and to the maximum of 1 mol alpo 4 on the silica rich side the mutual solubility appears to decrease with falling temperature at low t the crystals of berlinite quartz solid solutions are strongly zoned and show complex intergrowths between the p rich and silica rich phases they were studied by electron microprobe transmission electron microscopy and raman spectroscopy in the light of our new experimental results the extreme p enrichment reported earlier for some natural quartz hosted melt inclusions may be explained as a post entrapment contamination by the berlinite bearing host

rapid crystallization of the animikie red ace pegmatite florence county northeastern wisconsin inclusion microthermometry and conductive cooling modeling we evaluated the crystallization regime of a zoned pegmatite dike and the degree of magma undercooling at the onset of crystallization by analyzing coeval fluid and melt inclusion assemblages the liquidus temperature of the pegmatite magma was 720 c based on re melting of crystallized melt inclusions in heating experiments the magma crystallized sequentially starting with a thin border zone which formed in less than one day at an average temperature of 480 c based on primary fluid inclusions meaning 240 c undercooling the primary inclusions from the outer zones were postdated by secondary inclusions trapped between 580 and 720 c representing fluid exsolved from hotter still crystallizing inner pegmatite units the huge temperature contrast between the pegmatite s inner and outer zones was simulated by conductive heat numerical modeling a 2 5 m wide dike emplaced in 220 c rocks cools entirely to 400 c in less than 50 days unidirectional and skeletal textures also indicate rapid disequilibrium crystallization

geochronology geochemistry mineralogy and metallogenic implications of the zhaojinggou nb ta deposit in the northern margin of the north china craton china abstract the large zhaojinggou nb ta deposit is located in the northern margin of the north china craton ncc inner mongolia china the deposit is mainly hosted in the mineralized dikes around the hutoushan pluton and the residual pegmatite shell at the top of the pluton samples from the pluton and the mineralized dikes are characterized by high contents of sio2 73 3 84 3 total alkalis 5 24 9 60 and al2o3 7 94 13 8 and moderate a cnk values with an average of 1 04 indicating a weakly peraluminous affinity the trace element patterns are characterized by rb nb ta zr and hf enrichment and markedly negative ba sr p eu and ti anomalies zircon u pb dating suggests that the emplacement of the pluton and the nb ta mineralization occurred coevally in the early cretaceous 126 1 ma and 127 2 ma respectively variations in both bulk rock geochemistry k rb zr hf nb ta and mineral composition mica and columbite consistently unveil a magmatic evolutionary trend from the hutoushan alkali feldspar granite through the hutoushan pegmatite shell to the mineralized dikes typical a type characteristics of the granite and ancient hf isotopic features ehf t ranging from 6 80 to 12 95 and crust model ages from 1 61 to 2 00 ga indicate that the parental magma was derived from the partial melting of palaeoproterozoic crust with insignificant mantle material involved considering the significantly higher bulk contents of nb ta and f in the pegmatite shell and the mineralized dikes than that in the alkali feldspar granite as well as the similar composition in the biotite from the pegmatite shell and the alkali feldspar granite we propose that a residual nb ta enriched brine melt phase segregated from the crystal mush at the late stage of crystallization the progressive concentration of f in the melt was conducive to the solubility of nb and ta in granitic melts and decreased the viscosity by depolymerizing the melt and thus contributed to the high magma differentiation and nb ta concentration the post magmatic fluid triggered the fluid rock interaction resulting in the extensive albitization m type tetrad effect extremely low nb ta ratio

diffusion and fluid interaction in itrongay pegmatite madagascar evidence from in situ 40ar 39ar dating of gem quality alkali feldspar and u pb dating of protogenetic apatite inclusions alkali feldspar 40ar 39ar and apatite upb geochronological studies have typically invoked two mechanisms to account for apparent loss of radiogenic 40ar and 206 208pb some studies have suggested that the radiogenic isotopes were lost by volume diffusion and used these dates to constrain temporal variations of rock temperatures others have argued that the radiogenic isotopes were lost due to interaction with fluids and related these dates to chemical alteration these two end member interpretations have fundamentally different implications for tectonic models derived from geochronological data and therefore it is important to reliably identify the principal mechanism for loss of radiogenic isotopes here we revisit the mechanisms of 40ar loss in the famous gem quality alkali feldspar from the itrongay pegmatite in madagascar previous studies have suggested that volume diffusion is the dominant mechanism of 40ar loss providing key evidence to support the use of 40ar 39ar dating of alkali feldspar for thermochronology we attempted to verify these results by obtaining time temperature paths from petrologically characterised cogenetic feldspar and apatite from the itrongay pegmatite and comparing them with each other however our results suggest that only a minor component in the variability of 40ar 39ar dates of itrongay feldspar is related to the diffusive loss of 40ar and that this loss was not compatible with the majority of previously proposed models which hinders quantitative interpretations the crystal studied here grew in five episodes related to the influx initially of co existing dense sio2 rich solution and co2 dominated fluid the first and supposedly the following two episodes and subsequently of h2o rich fluid supposedly the final two episodes much greater component in the variability of the acquired 40ar 39ar dates is interpreted to reflect the differences in the ages of these growth episodes which we estimate to span from 477 ma to 176 ma the first four episodes apatite inclusions in this crystal are interpreted to be xenocrysts derived from the country rocks of the itrongay pegmatite these yield older upb dates than the estimated age of their host feldspar and have apparently experienced diffusive loss of 206 207pb prior to entrapment our 40ar 39ar results indicate that there is a lack of unambiguous evidence for diffusive loss of 40ar from alkali feldspar that can be readily interpreted for thermochronological purposes however in situ 40ar 39ar dating of alkali feldspar appears to be a promising tool for tracking fluid flow events in the earth s crust whose applicability is not restricted to sedimentary rocks our upb results corroborate previous suggestions that upb dating of apatite can be used for thermochronology

unique sodic calcic skarn hosted by ultramafic rocks and albitite at the ulsan skarn deposit gyeongsang basin south korea abstract the ulsan fe w skarn deposit is located within the cretaceous gyeongsang basin in the southeastern part of the korean peninsula the skarn and mineralization formed along contacts between the paleogene gadaeri granite limestone partially serpentinized ultramafic rocks dunite and harzburgite and hornfelsed volcanic and siliciclastic rocks these various country rock types produced a system with multiple types of skarn typically skarn within limestone occurs as clinopyroxene magnetite skarn clinopyroxene garnet skarn and garnet skarn but the unique host rocks ultramafic rocks albitite at ulsan also produced unusual skarn types such as a sodic calcic skarn system na ca skarn formed by chemical interactions between albitized granites and adjacent ultramafic rocks this na ca skarn contains unusual na rich clinopyroxene acmite na rich amphiboles cr rich clinopyroxene cr rich amphiboles sr bearing plagioclase and ba bearing k feldspar clinopyroxene and amphibole have na2o concentrations up to 6 5 wt and these minerals contain up to 12 1 and 2 5 wt cr2o3 respectively na was derived from albitite and the formation of cr bearing acmite kosmochlor and na amphibole richterite appears to have been related to the release of cr into the fluid phase by the breakdown of chromite in ultramafic rocks during prograde skarn formation k feldspar k ar dating yields an age of 50 3 1 7 ma for the prograde garnet skarn the related gadaeri granite exhibits a high k calc alkaline signature and a weakly metaluminous to peraluminous i type affinity with a total alkalinity na2o k2o of 8 5 8 8 wt the gadaeri granite shows an enriched ree pattern compared with albitite as well as negative eu anomalies which together with the k rb values 200 500 are suggestive of a highly evolved magma from a continental margin setting

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