tracking holocene glacial and high altitude alpine environments fluctuations from minerogenic and organic markers in proglacial lake sediments lake blanc huez western french alps holocene palaeoenvironmental evolution and glacial fluctuations at high altitude in the western french alps are reconstructed based on a multiproxy approach within lake blanc huez 2550 m a s l drainage basin the combination of seismic profiling 3 5 khz piston coring and radiocarbon dating in proglacial lacustrine sediments together with a detailed organic analysis of autochthonous and allochthonous supply allows documenting the evolution of glacier activity during the holocene over the last 9700 years the holocene lake record has a bimodal pattern whose transition is progressive and occurring between 5400 and 4700 cal bp during the early holocene the organic lacustrine facies reflects reduced glacial activity in the catchment this major glacial retreat seems to result from solar forcing and high summer insolation after 5400 cal bp lacustrine sedimentation is marked by the gradual increase both of minerogenic supply and soil erosion suggesting a progressive transition to wetter climatic conditions this climate change is synchronous both from the gradual decrease of summer insolation and the gradual reorganization of oceanic and atmospheric circulations characterizing the beginning of the neoglacial period both colder temperature and humid climate induced significant glacier advance since 4700 cal bp over this global trend three periods are particularly associated with higher runoff processes and higher soil erosion interpreted as wetter time intervals resulting from enhanced northern westerlies regimes across the north atlantic and western europe they are dated from 8700 to 7000 4700 to 2500 and 1200 to 200 cal bp these wetter phases drastically contrast with periods of reduced glacial activities dated from the early bronze age ca 3870 3770 cal bp the iron age ca 2220 2150 cal bp the roman period ca ad115 330 and the medieval warm period ca ad760 1160 in addition these dryer periods are associated with mining activities at high altitude

incipient metamorphism in the lower palaeozoic marginal basin of wales a diagenctic through anchizone to epizone transition is demonstrated in pelitic rocks of the lower palaeozoic marginal basin of wales by examination of variations in phyllo silicate mineralogy illite crystallinity and bo parameter of white micas this transition represents a temperature range from 150 c to 400 c and the metamorphism is of a low pressure facies series type with a geothermal gradient of 40 ckm 1 variations in grade can be correlated largely with the original basin and shelf form suggesting a depth related metamorphism however in areas closer to the site of caledonian plate collision an increasingly syn tectonic metamorphic event is apparent correlation of pelite data with metabasite assemblages is variable the most consistent relationship being between epizone crystallinity values andepidote actinolite greenschist facies assemblages diagenetic clay mineral assemblages are found associated with prehnite pumpellyite assemblages in metabasites and it is suggested that the latter represent non buffered and therefore non diagnostic assemblages

little ice age precipitation in jotunheimen southern norway recently published glaciological data from southern norway enable analysis of changes in glacier geometry since the little ice age lia and estimation of the magnitude of the lia precipitation anomaly glacier area extents in the jotunheimen region have been created for 2003 using glacier outlines derived from landsat and for the lia maximum about ad 1750 by using glacier outlines defined by moraines a 25 m digital terrain model from 1980 was used to derive inventory data for both times both inventories provide area and altitude range as well as length slope and aspect of the glaciers area altitude profiles a z for the lia maximum are calculated from the 1980 profiles by assuming that the area increase distribution a z was concentrated at low altitude and it integrates to the measured area difference between 1980 and the lia under this assumption the regionally averaged mean altitude change from 1980 to the lia z 68 m glacier mass balance measurements show that the mass balance gradie

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

syn metamorphic element transfer across lithological boundaries in the port aux basques gneiss complex newfoundland mineralogical reaction zones developed between mafic gneiss amphibolite and metapelite reveal the role of cm scale metasomatism during amphibolite facies metamorphism of the port aux basques gneiss complex pbgc ionic diffusion between mafic and pelitic layers led to the development of 1 3 cm wide schistose biotite garnet rich type 1 reaction zones at the margins of mafic layers and or the crystallization of poikiloblastic hornblende within a garnet and biotite depleted type 2 reaction zone up to 20 cm wide within nearby paragneiss garnet biotite thermometry of the type 1 reaction zones indicates tmax of c 560 645 c at a pressure of c 6 kbar constrained by gasp and grail subassemblages in the host rock compared to the unaltered amphibolite type 1 reaction zones are enriched in k rb and ba and depleted in ca and sr compared to the unaltered metapelite type 2 reaction zones show opposite trends they are depleted in k rb and ba and enriched in ca and sr this indicates that the formation of the reaction zones involved the exchange of k ca and related trace elements in opposite directions across the amphibolite paragneiss interface and that the system was approximately closed to these components where both reaction zones are present

low grade and very low grade regional metabasic ordovician rocks of llŷn and snowdonia gwynedd north wales metabasic assemblages belong to the prehnite pumpellyite and greenschist facies the isograds pumpellyite in pumpellyite out clinozoisite in and biotite in have been mapped and divide the area into four metamorphic zones field and petrographic evidence indicate that the metamorphic crystallization was largely syn and immediately post tectonic viz end silurian to devonian the use of published schreinemakers bundles indicates that most of the prehnite pumpellyite bearing assemblages formed at high grades within the facies and that the greenschist facies rocks crystallized in the higher pressure field as the amount of calcite increases so diagnostic ca al silicates are reduced and eventually eliminated from assemblages contrary to recent claims the evidence indicates that the gwna group and the gwyddel felsitic beds of ll n were metamorphosed prior to the arenig

modelling the evolution of vadret da morteratsch switzerland since the little ice age and into the future we use a 3 d higher order glacier flow model for vadret da morteratsch engadin switzerland to simulate its strong retreat since the end of the little ice age lia and to project its future disintegration under a warming climate the flow model coupled to a 2 d energy balance model is initialized with the known maximum glacier extent during the lia and subsequently forced with mean monthly precipitation and temperature records to correctly reproduce the observed retreat of the glacier front for the period 1864 2010 additional mass balance perturbations are required to account for uncertainties in the initial state the mass balance model and climate variations not captured by the ambient meteorological records changes in glacier volume and area are in good agreement with additional information from historical topographic maps under constant 2001 10 climate conditions a strong retreat and mass loss continue and vadret da morteratsch disconnects from its main tributary vadret pers before 2020 the future glacier evolution is analysed in detail to understand the timing and rate of retreat and to assess the role of ice dynamics assuming a linearly increasing warming of 3 c by 2100 only isolated and largely stagnant ice patches remain at high elevation

very high elevation mont blanc glaciated areas not affected by the 20th century climate change 1 this paper analyses the impact of climate change over the last 100 years on high elevation glaciated areas of the mont blanc range comprising ice fields covering the top of the mont blanc 4808 m and dome du gouter 4300 m areas surface ablation is negligible for these high elevation areas and the surface mass balance is mainly controlled by snow accumulation at dome du gouter ice fluxes have been calculated through two transversal sections by two independent methods in order to assess long term surface accumulation a comparison between these results and recent accumulation observations together with the strong relationship between valley precipitation and snow accumulation suggests that surface accumulation rates did not change significantly over the entire 20th century moreover the small ice thickness changes less than 3 m on the average observed at mont blanc and dome du gouter between 1905 and 2005 clearly reveal that these high elevation glaciated areas have not been significantly affected by climate change over the last 100 years

micron to nanoscale characterisation and u pb geochronology of zircon from granites of the samphire pluton south australia abstract zircons from three distinct granites within the samphire pluton south australia are characterised at the micron to nanoscale sensitive high resolution ion microprobe shrimp u pb zircon dating generated 207pb 206pb weighted average ages of 1586 9 3 ma 1583 2 8 5 ma and 1578 9 5 ma respectively although zircons from all three granites display evidence of hydrothermal overprinting this is most strongly expressed in a distinct red colored granite referred to here as granite c alteration is expressed as variation in the concentrations of hree y th and pb whereby grain margins are relatively enriched in these elements and both zr and si are depleted altered zircon cores have high u contents relative to grain margins which are appreciably poorer in this element whereas th is strongly enriched within crosscutting microfractures coupled with the relative enrichment in non formula elements and marked disturbance of u th pb isotope ratios the nanoscale observations of pb bearing nanoparticles galena implying mobility of pb and other elements nanofractures and structural defects demonstrate that zircon in granite c has undergone multi stage alteration impacting upon accurate dating importantly and with implications for analogous systems elsewhere our results confirm nanoscale open system u pb behaviour in hiltaba suite zircon shrimp u pb zircon geochronology cannot confidently resolve any statistical differences in the age of the three granites despite their distinct appearance suggesting they might represent temporally distinct phases of a larger magmatic system zircons within the most altered granite c directly underlying the blackbush uranium prospect contain convincing micron to nanoscale evidence for an alteration event that triggered a remobilisation of uranium from granite into the cover sequence

10 be exposure dating of the timing of neoglacial glacier advances in the ecrins pelvoux massif southern french alps alpine glacier variations are known to be reliable proxies of holocene climate here we present a terrestrial cosmogenic nuclide tcn based glacier chronology relying on 24 new be 10 exposure ages which constrain maximum neoglacial positions of four small to mid sized glaciers rateau lautaret bonnepierre and etages in the ecrins pelvoux massif southern french alps glacier advances marked by mainly lateral moraine ridges that are located slightly outboard of the little ice age lia c 1250 1860 ad maximum positions were dated to 4 25 0 44 ka 3 66 0 09 ka 2 09 0 10 ka c 1 31 0 17 ka and to 0 92 0 02 ka the 4 2 ka advance albeit constrained by rather scattered dates is to our knowledge exposure dated here for the first time in the alps it is considered as one of the first major neoglacial advance in the western alps in agreement with other regional paleoclimatological proxies we further review alpine and northern hemisphere mid to high latitude evidence for climate change and glacier activity concomitant with the 4 2 ka event the 2 1 ka advance was not extensively dated in the alps and is thought to represent a prominent advance in early roman times other neoglacial advances dated here match the timing of previously described alpine neoglacial events our results also suggest that a neoglacial maximum occurred at etages glacier 0 9 ka ago i e during the medieval climate anomaly mca c 850 1250 ad at rateau glacier discordant results are thought to reflect exhumation and snow cover of the shortest moraine boulders overall this study highlights the need to combine several sites to develop robust neoglacial glacier chronologies in order to take into account the variability in moraine deposition pattern and landform obliteration and conservation

solving the paradox of the end of the little ice age in the alps 1 the causes and timing of the little ice age fifteenth to nineteenth centuries are still unclear crowley 2000 bond et al 2001 shindell et al 2001 during the last part of this event 1760 1830 the advance of glaciers in the alps conflicts with the summer temperature signal intergovernmental panel on climate change 2001 this paper attempts to solve this paradox from glacier fluctuations and monthly temperature data we show that mean winter precipitation was higher by at least 25 during this final phase compared to the twentieth century average and that glacier recession after 1830 clearly resulted from a winter precipitation decrease and not a temperature increase conversely since the beginning of the twentieth century glacier changes have been driven mainly by temperature change

glacier decline between 1963 and 2006 in the cordillera real bolivia 1 the volume changes of 21 glaciers in the cordillera real have been determined between 1963 and 2006 using photogrammetric measurements these data form the longest series of mass balances obtained with such accuracy in the tropical andes our analysis reveals that temporal mass balance fluctuations are similar revealing a common response to climate over the entire studied region the mass of these glaciers has clearly been decreasing since 1975 without any significant acceleration of this trend over recent years we have found a clear relationship between the average mass balance of these glaciers as a function of exposure and altitude from this relationship the ice volume loss of 376 glaciers has been assessed in this region the results show that these glaciers lost 43 of their volume between 1963 and 2006 essentially over the 1975 2006 period and 48 of their surface area between 1975 and 2006

sensitivity of mass balance and equilibrium line altitude to climate change in the french alps assessment of the sensitivity of surface mass balance and equilibrium line altitude ela to climate change is crucial for simulating the future evolution of glaciers such an assessment has been carried out using an extensive dataset comprising numerous measurements of snow accumulation and snow and ice ablation made on four french glaciers over the past 16 years winter mass balance shows a complicated pattern with respect to altitude with no clear linear relationship although the ratios of winter mass balance to valley precipitation differ considerably from site to site they are relatively constant over time relationships between snow ice ablation and temperature are stable with no link with altitude the mean snow and ice positive degree day pdd factors are 0 003 and 0 0061 m w e c 1 d 1 this analysis shows that at a given site ablation depends mainly on the amount of snow precipitation and on cumulative pdds the sensitivity of annual ablation to temperature change increases almost linearly from 0 25 m w e c 1 at 3500 m to 1 55 m w e c 1 at 1650 m ela sensitivity to temperature change was found to range from 50 to 85 m c 1

hematite geochemistry and geochronology resolve genetic and temporal links among iron oxide copper gold systems olympic dam district south australia abstract the wirrda well and acropolis prospects 25 km south from the olympic dam deposit are among several dozen examples of iron oxide copper gold iocg mineralisation forming a 600 km long province in the eastern gawler craton south australia iocg systems across the province differ in terms of host lithology iron oxide mineral associations intensity of brecciation and grade of cu u au mineralisation previous efforts to provide a geochronological framework for mineralisation and correlate this with igneous activity were inhibited by a lack of clear crosscutting features particularly in breccia hosted systems and a scarcity of reliable hydrothermal mineral geochronometers the earliest generation of hematite characterised by enrichment in u w sn mo and previously reported from olympic dam provides confident u pb dates and insights into hydrothermal fluid signatures similar hematite is recognised from wirrda well and acropolis allowing direct comparison between the three iocg systems relationships between early silician wirrda well and titaniferous acropolis magnetite and u bearing hematite at the two prospects differ inferred martitisation of magnetite at acropolis has generated zoned hematite with u w mo enrichment at constant sn concentration but with a marked loss of ree y rey and ti whereas at wirrda well single crystal zoned hematite resembling that from olympic dam retains high rey and sn concentrations although morphologies textures and compositions of u bearing hematite at olympic dam wirrda well and acropolis vary significantly a common u pb laser ablation inductively coupled plasma mass spectrometry age of 1590 ma is obtained from the most reliable data 207pb 206pb 1598 9 6 3 ma at wirrda well and 1590 6 6 5 ma at acropolis the geochemical signatures of iron oxides from the two prospects share common trends for u w sn mo high field strength and siderophile elements comparable with signatures of fe oxides from the outer shell of the olympic dam deposit given that datable iron oxides would seem to be ubiquitous phases throughout the eastern gawler craton the commonality in geochemistry and age of u bearing hematite from the olympic dam district is significant as it provides a single traceable mineral to compare iocg systems across the province

common climatic signal from glaciers in the european alps over the last 50 years conventional glacier wide mass balances are commonly used to study the effect of climate forcing on glacier melt unfortunately the glacier wide mass balances are also influenced by the glacier s dynamic response investigations on the effects of climate forcing on glaciers can be largely improved by analyzing point mass balances using a statistical model we have found that 52 of the year to year deviations in the point mass balances of six glaciers distributed across the entire european alps can be attributed to a common variability point mass balance changes reveal remarkable regional consistencies reaching 80 for glaciers less than 10 km apart compared to the steady state conditions of the 1962 1982 period the surface mass balance changes are 0 85 m water equivalent w e a 1 for 1983 2002 and 1 63 m w e a 1 for 2003 2013 this indicates a clear and regionally consistent acceleration of mass loss over recent decades over the entire european alps

1760 ma magnetite bearing protoliths in the olympic dam deposit south australia implications for ore genesis and regional metallogeny spatial associations between banded iron formation and iron oxide cu au iocg style mineralization are well documented in the gawler craton south australia but the possible genetic relationships between these two distinct types of mineralization are hitherto unclear a texturally conspicuous generation of coarse grained silician magnetite intergrown with carbonates and quartz is observed in drillholes intersecting the outer shell of the olympic dam iocg type deposit this magnetite is characterised by high u content 50 ppm siliceous chemistry and unusual zonal textures with respect to si fe nanoprecipitates direct dating of this magnetite by laser ablation inductively coupled plasma mass spectrometry yields reproducible 207pb 206pb dates 1761 16 ma that are significantly older than the granite hosting the deposit 1593 ma or the mineralized breccias constituting the cu u au ag resource 1592 1589 ma the older fe rich crustal material can be correlated with the 1 76 1 74 ga meta sedimentary wallaroo group host to fe rich horizons across the gawler craton including locations 15 km nw of olympic dam a generation of granitic rocks which intruded bedrock at 1 75 ga are present 30 km ne of olympic dam and likely exsolved hydrothermal fluids that enriched pre existing magnetite bearing protoliths in both u and ree such material was physically and likely chemically incorporated into the outer shell at olympic dam some 150 ma later during granite uplift along faults the coincidence between fe rich horizons bif and 1750 ma granitoids may have provided iocg systems with an additional source of both fe and u that predates the 1 59 ga craton scale metallogenic event the uranium concentrations in some south australian iocg systems represent major global anomalies in the element a combination of the fortuitous geological circumstances outlined here may help explain the highly anomalous accumulation of uranium found at olympic dam

ice ablation as evidence of climate change in the alps over the 20th century 1 over fifty years of cumulative annual mass balance data for several glaciers in the alps shows similar fluctuations which seem to provide evidence of a common climatic signal separate winter and summer mass balance measurements from the claridenfirn glacier in switzerland since 1914 and the sarennes glacier france since 1949 show that 1 the annual mass balance is primarily driven by the summer mass balance term and 2 melting rate variations with time are very similar for these two glaciers located 290 km apart the increase in the ablation rate of 0 5 cm w e day 1 between the two periods 1954 1981 and 1982 2002 over these two glaciers corresponds to a 20 wm 2 rise in the energy flux at the glacier surface these results suggest that a common summer melting rate change may have affected the alps as a whole detailed observations on the sarennes glacier show that the origin of this strong increase in summer ablation since 1982 is not only a rise in the summer melting rate but also an increase in the ablation period during the months of september and october

iron oxides constrain bif evolution in terranes with protracted geological histories the iron count prospect middleback ranges south australia abstract when studied at appropriate scales of observation and using complementary methods the intrinsic textural and geochemical complexity of iron oxides can provide unparalleled insights into the evolution of iron ore resources from banded iron formation deposition to ore formation iron count is one of 20 deposits and prospects within the archean middleback ranges iron ore belt south australia in which iron oxides from bifs and ores display variable textural and trace element signatures integrated petrography iron oxide laser ablation mapping and geochemistry and in situ dating of bif derived ores was undertaken to assess whether features observed in samples from this representative prospect might be attributed to localized and superimposed overprint processes the prospect consists of a west and east ridge each characterized by a sequence of overprints expressed as interconversions between iron hydr oxides and accompanying variation in trace element concentrations pseudomorphic replacement of early magnetite by hematite martite followed by replacement by iron hydroxides is recognized in samples from the east ridge further overprints are expressed as veining brecciation and crystallization of micro platy hematite rich in granitophile elements sn mo w u martitization of early magnetite in the west ridge is accompanied by enrichment in zn co and ni in martite subsequent recrystallization of martite iron hydroxides by granoblastic hematite is marked by enrichment in ti ta nb ree and granitophile elements and co crystallization of ree minerals this is followed by crystallization of micro platy hematite similarly rich in these elements enrichment in ti and granitophile elements in granoblastic hematite is interpreted to infer crystallization from highly saline fluids generated by interaction between evaporite bearing sedimentary rocks and granite derived fluids post archean australian shale normalized rey fractionation trends of iron oxides from the east ridge are consistent with precipitation of iron rich minerals from a mixture of anoxic seawater and hydrothermal vent fluids analogous trends from the west ridge lack a seawater signature contrasts in rey fractionation trends between the two ridges is interpreted as a combination of the loss of primary seawater signature due to severe overprinting in the west ridge and to lateral variation in the marine depositional environment results validate the hypothesis that variation in iron oxide trace element signatures seen throughout the middleback ranges iron ore belt results from overprinting due to superimposed tectono magmatic events that have locally affected each deposit despite undergoing different sequences of ore forming stages as well as possibly distinct depositional environments the two ridges share a common overprint dated here at 1790 ma using in situ u pb geochronology of co existing hematite monazite and xenotime this age is considered to represent the timing of interaction between granite derived fluids with ore hosting rock such interpretation is supported by the geochemical signatures of the dated iron oxides showing enrichment in granitophile elements and coincident ages for the wertigo granite and myola volcanics which occur proximal to the prospect and were emplaced erupted during intracontinental rifting the approach undertaken here combining petrography iron oxide geochemistry and in situ dating of bif derived ores is generically applicable to other iron resources within the middleback ranges or analogous terranes elsewhere

coticules of the belgian type area stavelot venn massif limy turbidites within the nascent rheic oceanic basin abstract coticule is the name originating in belgium for a fine grained metasedimentary yellowish rock mainly composed of quartz spessartine and mica which is repeatedly interstratified in the hematite rich purple slates of the lower ordovician of the ardenne region it was described for the first time in the nineteenth century in the stavelot venn massif ardenne which is accordingly the type area for this peculiar lithology since then numerous occurrences were described all over the world in metamorphic rocks of various grades and ages the exact nature of the belgian coticule protolith remained hypothetical although intensively discussed for a long time in the literature after an extensive review of all the stratigraphical sedimentological and geochemical results and new field geochemical major and trace elements and nd isotopic investigations we propose a significantly improved and sustained genetic model the thin coticule layers were deposited offshore in a deep oceanic basin as limy mud turbidites during the early floian c 477 ma early ordovician density currents came from the north from the shelf which bordered the emergent brabant massif at that time and flowed down the slope to the deep basin plain the purple shales enclosing the coticule layers represent the normal pelagic sedimentation in the basin these shales are exceptionally rich in fe and mn because of the hydrothermal activity of the nearby and young rheic ocean ridge indeed the rheic ocean opened in the early ordovician c 482 ma during diagenesis the strongly oxidizing depositional environment favoured the mobility of mn 2 as opposed to fe 3 that remained insoluble and immobile this allowed for the migration of divalent manganese from the pelagic shales and for replacing calcium in the turbiditic carbonate fraction to form rhodochrosite later epizonal metamorphism transformed the clay quartz rhodochrosite paragenesis of the protolith into the muscovite quartz spessartine paragenesis of the coticule hence in the type area coticule genesis needed a peculiar environment including a continental shelf with limy mud deposits a continental slope generating periodical turbidites and a nearby oceanic ridge here the nascent rheic ocean delivering hydrothermal iron and manganese

timing of iron oxide cu au u hydrothermal activity and nd isotope constraints on metal sources in the gawler craton south australia the eastern gawler craton hosts australia s premier uranium bearing iron oxide copper gold iocg belt the 500 km long olympic cu au u province in addition to the olympic dam cu u au and prominent hill cu au deposits numerous barren and weakly mineralized iocg prospects are present in the province new geochronological data for hydrothermal minerals combined with constraints from host rock ages demonstrate that alteration and associated iocg mineralization formed between 1570 and 1600 ma in three districts of the province this iocg hydrothermal activity temporally overlaps with magmatism of the hiltaba suite and gawler range volcanics titanites in paragenetically early magnetite bearing alteration in the olympic dam and prominent hill districts yield u pb ion probe ages of 1576 5 and 1567 10 ma respectively molybdenite in veins crosscutting magnetite biotite and albitic alteration in the moonta wallaroo district have re os ages of 1574 6 and 1599 6 ma respectively these represent minimum ages of the iocg alteration assemblages in this district a muscovite 40ar 39ar age of 1575 11 ma provides a minimum age of paragenetically later hematitic alteration in the olympic dam district neodymium isotope compositions were determined for 44 whole rock samples from barren and weakly mineralized cu au prospects and host rocks in the olympic dam and prominent hill districts the new geochronological framework enables comparison of the nd isotope data across two iocg districts at the time of formation of the olympic dam deposit ca 1590 ma magnetite rich weakly cu mineralized alteration from five prospects yields a relatively narrow range end 1590 values of 5 8 to 4 1 both hematite and magnetite rich alteration yield generally similar end 1590 values that match values from fresh and weakly altered paleoproterozoic metasedimentary and metagranitic rocks 6 6 to 3 5 as well as from most felsic hiltaba suite intrusions and gawler range volcanics in the eastern gawler craton ca 6 to 4 these data are consistent with crustal sources for ree and by implication for associated copper in the barren and weakly mineralized prospects mineralization and alteration in these minor iocg systems can be geochemically discriminated from the giant olympic dam deposit where greater inputs of mantle derived ree and other ore components are evident 2007 society of economic geologists inc

towards chronologies of gully formation optical dating of gully fill sediments from central europe relic gullies are commonplace in the hill landscapes of central and western europe understanding their formation is essential to identify how landscapes respond to environmental change and especially high magnitude rainfall events the relic gully systems were studied intensively but their genesis is still a matter of debate the major problem being insufficient information on the timing of their formation and infilling here we investigate if optical dating of quartz can be used to determine the ages of relic gully systems we studied known age deposits and used quartz grains of different size fractions based on single aliquot regenerative dose protocols equivalent doses were estimated the dose distributions analysed and minimum age models calculated the results show that in many cases optical dating can be successfully applied larger grains seem to be better bleached as optical ages of the coarsest grain size fractions middle sand are in agreement with independent age information from 14c dating and historical sources whereas optical ages of smaller grain size fractions fine sand are overestimates

origin of the outburst flood from glacier de tete rousse in 1892 mont blanc area france extensive field measurements and historical data have been used to re analyse the cause of the outburst flood from glacier de tete rousse that devastated the village of saint gervais le fayet french alps in 1892 causing 175 fatalities the origin of this disaster was the rupture of an intraglacial cavity in glacier de tete rousse that released 200 000 m 3 of water and ice all previous studies have concluded that the intraglacial cavity was formed from a crevasse that was filled and enlarged by meltwater the re analysis presented here suggests that the reservoir of the upper cavity did not originate as an enlarging crevasse the origin of the meltwater reservoir was more likely a supraglacial lake formed before 1878 during a period of negative mass balance following a period of positive mass balance after 1878 the lake was hidden until the outburst flood of 1892 this means that such hazards may be detected by checking regularly for the formation of a lake on the surface of the glacier before it is hidden

petrographic and geochronological constraints on the granitic basement to the middleback ranges south australia abstract the middleback ranges is a 60 km long bif endowed iron ore belt located in the southeastern gawler craton and is the largest exploited iron resource in south australia the belt is hosted within an archean to paleoproterozoic aged granitic gneissic basement terrane petrographic and geochronological constraints are given for a suite of granites associated with deposits throughout the middleback ranges and compared with other regional granites granites from the middleback ranges show complex mineralogical and geochemical features indicating multiple overprinting events sensitive high resolution ion microprobe u pb zircon ages from all granites across the middleback ranges yield archean ages suggesting the existence and a more extensive distribution of mesoarchean crust than previously recognized beneath the entire middleback ranges bif sequence grey and pink granites from the central middleback ranges sultan prospect produced the oldest 207pb 206pb weighted mean ages within the sample suite 3241 6 and 3238 9 ma respectively zircon in the latter granite also features overgrowths dated at 2 6 ga and interpreted to be metamorphic a second group of younger granites from the iron monarch deposit and a sample of cooyerdoo granite northern middleback ranges have a minimum crystallization age of 3165 8 ma and a 207pb 206pb weighted mean magmatic age of 3134 18 ma respectively the youngest granites analyzed here derive from the iron baron deposit in the central part of the belt which display strong deformation and have a minimum crystallization age of 3089 9 ma and from the iron magnet deposit in the southern part of the belt 207pb 206pb weighted mean age of 3023 33 ma petrographic and geochemical features observed within the sample suite indicate that post archean overprinting events led to alteration of the granitic basement and may infer that fluid rock interaction and granite leaching were important for bif upgrading processes and iron oxide formation

climatic warming glacier recession and runoff from alpine basins after the little ice age maximum records of discharge of rivers draining alpine basins with between 0 and 70 ice cover in the upper aare and rhone catchments switzerland for the period 1894 2006 have been examined together with climatic data for 1866 2006 with a view to assessing the effects on runoff from glacierized basins of climatic warming coupled with glacier recession following the little ice age maximum annual runoff from ice free basins reflects precipitation variations rising from minima between 1880 and 1910 to maxima between the late 1960s and early 1980s the more highly glacierized the basin the more runoff mimicked mean may september air temperature during two periods of warming runoff increased gradually from the 1900s rapidly in the 1940s before decreasing to the late 1970s rising runoff levels during the second warming period failed to exceed those attained during the first despite higher summer temperatures although temperatures continued to rise discharge from glacierized basins declined after reaching maxima in the late 1980s to early 1990s in the first warming period rising specific melt rates augmented by increasing precipitation opposed the impact of declining glacier area on runoff although melt continued to increase in the second period enhanced melting even in the exceptionally warm summer of 2003 appears to have been insufficient to offset reducing glacier surface area exposed to melt low or reducing levels of precipitation and increasing evaporation thus runoff from glacierized basins peaked in the late 1940s to early 1950s

glacier thickening and decay analysis from 50 years of glaciological observations performed on glacier d argentiere mont blanc area france numerous glaciological data have been obtained from measurements carried out on glacier d argentiere mont blanc area france since the beginning of the 20th century moreover data on annual mass balance ice flow velocity thickness variation and length fluctuation have been obtained from yearly measurements performed since 1975 this dataset provides an excellent opportunity to analyze the relationships between surface mass balance and dynamic response over time periods during which net mass balance changed from positive to negative following a positive specific net balance period between 1960 and 1981 the ablation zone experienced a large increase in thickness and ice flow velocities conversely the highly negative specific net balance period since 1982 has led to strong thinning deceleration and retreat of the tongue the response of these observed dynamics to surface mass balance is analyzed from ice flux calculations performed on three transverse cross sections our results reveal that the ice fluxes are largely accommodated by ice flow velocities velocity fluctuations are synchronous over the entire area studied in the largest part of the glacier no compressing extending flow change has been observed over the last 30 years and thickness changes are solely driven by surface mass balance changes however on the tongue of the glacier thickness changes do not depend on surface mass balance but are mainly driven by changes in the longitudinal strain rate

refined proterozoic evolution of the gawler craton south australia through u pb zircon geochronology abstract through the application of both conventional u pb zircon analyses and small sample u pb isotopic analyses the nature and timing of tectonic events leading to the formation of the gawler craton have been defined more precisely constraints on deposition of early proterozoic iron formation bearing sediments have been narrowed down to the period 1960 1847 ma deformed acid volcanics including the economically important moonta porphyry have zircon ages of 1790 and 1740 ma the voluminous acid gawler range volcanics and correlatives to the east were erupted over a short interval at 1592 2 ma and were intruded by anorogenic granites at 1575 ma small sample zircon analyses proved to be an extremely valuable adjunct to conventional analyses generally yielding more concordant data which forced a curved discordia through an upper intercept slightly younger than from a conventional straight line discordia

the geochemistry of manganese carbonate in panama basin sediments abstract the mn distribution in panama basin area sediments and interstitial waters is discussed striking surficial mn enrichments produced by a well known diagenetic recycling process characterize the sediments of the region thermodynamic solubility calculations indicate that in at least one core interstitial waters approach saturation with respect to mnco3 a mixed carbonate phase of composition mn48 ca47 mg5 co3 was recovered from an ash band in the same core the association of this material with the coarse volcaniclastic debris is thought to result from facile manganous carbonate precipitation in sediment horizons of coarser mean grain size since sulphate reduction in the upper two metres of panama basin sediments is fairly minor little increase in alkalinity is observed and it is postulated that significant production of carbonate alkalinity is not a prerequisite for manganous carbonate generation in hemipelagic sediments a more important factor appears to be the availability of mn oxides for solution during early diagenesis stable c isotopic analyses indicate that little c of organic origin is used in the precipitation reaction in either panama basin or loch fyne scotland sediments

mid to late holocene paleoenvironmental changes and glacier fluctuations reconstructed from the sediments of proglacial lake buruo co northern tibetan plateau abstract glaciers on the tibetan plateau are an important freshwater resource for large populations in south and southeast asia therefore it is important to understand past variations in glacier activity in the region to assess their possible response to ongoing climatic warming here we present the results of analyses of grain size total organic carbon pollen ratio artemisia to chenopodiaceae and the element content of a 435 cm long sediment core from proglacial lake buruo co on the northern tibetan plateau our results indicate that the buruo co catchment experienced relatively warm and humid conditions during 5 2 4 0 cal kyr bp during which retreating glaciers released large amounts of freshwater precipitation was also abundant during this interval as a result of the relatively strong indian summer monsoon and weaker westerlies and thus the lake level was high during 4 0 1 3 cal kyr bp the westerlies were gradually enhanced and the climate became colder and drier in response the glaciers advanced and the lake level decreased during 1 3 0 cal kyr bp under relatively cold conditions a large volume of glacial ice was maintained nevertheless under the westerlies influence the lake level rose four episodes of glacial advance are detected at 3 6 3 4 3 2 2 3 1 9 1 7 and 0 4 0 1 cal kyr bp these episodes correspond well with bond events in the north atlantic implying that climate change and glacial activity at buruo co were largely driven by variations in northern hemisphere insolation and by climatic oscillations in the north atlantic region via the influence of the westerlies

late holocene nao and oceanic forcing on high altitude proglacial sedimentation lake bramant western french alps comparison of glacially derived clastic inputs in high altitude proglacial lake bramant western french alps with measured north atlantic oscillation winter naow index reveals an inverse correlation between ad 1884 and 1968 at the pluridecadal timescale 20 25 years this reflects periodical variations in snow accumulation over lake bramant catchment area partly influencing the glacier mass balance in the watershed further comparisons with reconstructed naow index since ad 1500 highlight spatial and temporal variations of the pluridecadal naow influence on this alpine climate especially at the end of the little ice age in addition wavelet analysis of continuous proxies of clastic sedimentation over the last 4150 years indicates significant pluridecadal variability at frequencies compatible with the nao 30 years while periods centered at 60 70 years could also be linked to the north atlantic ocean atmosphere internal variability atlantic multidecadal oscillation amo the influence of the n

the history of soil erosion and fluvial deposits in small catchments of central europe deciphering the long term interaction between humans and the environment a review abstract during the last few decades many case studies focused on the dynamics of fluvial systems in response to hillslope erosion land use impact and climate changes this paper will review the current state of knowledge of the dynamics of past soil erosion and gullying in small catchments

geological setting and genesis of coticules spessartine metapelites in the lower ordovician of the stavelot massif belgium the lower ordovician in the caledonian stavelot massif belgium contains a coticule member probably arenig in age composed of red hematite rich shales alternating with thin yellowish coticule beds these coticules are fine grained highly manganiferous metamorphic rocks mainly composed of spessartine garnet mica and quartz similar rocks of about the same age occur in several localities along the appalachian and caledonian fold belts the belgian coticules are thought to have originated from marly sediments which had been deposited rapidly probably by density currents and in which caco 3 had been diagenetically replaced by mnco 3 during metamorphism spessartine garnets were formed from this mnco 3 and mica manganese and iron are thought to have originated from volcanic exhalative processes

simulation of the historical variations in length of unterer grindelwaldgletscher switzerland the historical length variations in unterer grindelwaldgletscher have been simulated by coupling a numerical mass balance model to a dynamic ice flow model as forcing functions we used partly reconstructed local climatic records which were transformed by the mass balance model into a mass balance history the ice flow model then computes the length variations that have occurred over the course of time in a model run from ad 1530 to the present with both seasonal temperature and precipitation variations as forcing functions the observed maximum length of the glacier around ad 1860 and the subsequent retreat are simulated the observed ad 1600 maximum however does not show up in the simulation this is probably due to an incorrect reconstruction of the mass balance for this period as detailed climatic data are available only since 1865 the root mean square difference between the simulated and the observed front positions is 0 28 km the simulated glacier geometry for 1987 fits the observed geometry for that year reasonably well because of the success of the historical simulation an attempt is made to predict future glacier retreat on the basis of two different greenhouse gas scenarios for a business asusual scenario only 29 of the 1990 volume would remain in ad 2100

tectonic framework and evolution of the gawler craton southern australia the gawler craton is the major crustal province in the southern australian proterozoic and is pivotal in models seeking to describe the evolution of proterozoic australia the craton is host to the olympic dam iron oxide cu au u ree deposit as well as a number of other iron oxide copper gold iocg au and iron ore deposits the evolution of the gawler craton is dominated by two major phases of tectonic activity late archean and late paleoproterozoic early mesoproterozoic in total spanning ca 1 billion years the late archean 2560 2500 ma basin development was coeval with arclike felsic magmatism and mafic ultramafic magmas including komatiites collisional deformation between 2480 and 2420 ma led to ca 400 m y of tectonic quiescence conceivably within an early paleoproterozoic continental interior the second major phase of tectonic activity was in the middle to late paleoproterozoic and early mesoproterozoic 2000 1450 ma paleoproterozoic tectonism was initially dominated by rift related events which produced a series of basins over the interval ca 1900 to 1730 ma some of which contain significant iron ore reserves transient contractional deformation at ca 1850 ma led to batholith scale granitic magmatism in part derived from melting of the late archean basement major basin development was finally terminated by the 1730 to 1690 ma kimban orogeny the effects of which are widespread and include the formation of crustal scale shear systems granitic magmatism and low to high grade metamorphism the kimban orogeny was followed by a renewed period of extension between ca 1680 and 1640 ma leading to local magmatism and sedimentation which appears in part to have been coeval with the high grade ca 1650 ma ooldean event in the western gawler craton at ca 1620 to 1615 ma the generation of the arc related st peter suite in the southern gawler craton implies that craton components were located at an active plate margin the arc environment was superseded by a transition to a continental interior regime which coincided with the voluminous gawler range volcanics 1595 1590 ma and hiltaba suite granitoids 1595 1575 ma the hiltaba suite is dominated by high t fractionated felsic rocks with coeval mafic magmatism confirming a mantle involvement emplacement of the hiltaba suite coincided with the major mineralizing interval in the gawler craton regionally two distinct mineral systems have been recognized the olympic iocg province in the eastern part of the craton and the gold dominated systems within the central gawler gold province the spatial distribution of iocg versus au dominated mineral systems appears to reflect regional variations in crustal composition and hiltaba suite petrogeneses hiltaba aged granites in the olympic iocg province are isotopically more evolved richer in u and th and oxidized compared to similar aged granites in the au dominated province modern day heat flow in the iocg province is significantly higher 90 10 mwm 2 compared to the au dominated province 54 5 mwm 2 suggesting there are important lithospheric compositional differences between the two metallogenic provinces which may reflect an older phase of craton assembly widespread northwest southeast contractional deformation coeval with the emplacement of the hiltaba suite is expressed by the formation and or reactivation of shear zones ranging up to crustal scale within this regime northwest trending structures such as those in the vicinity of the olympic dam deposit are likely to have accommodated dilation associated with strike slip movements intersection between these structures and northeast trending contractional faults may have formed suitable structural traps for 1590 to 1580 ma mineralization the timing of syn hiltaba deformation overlaps with transpression and medium to high grade metamorphism associated with the ca 1570 to 1540 ma kararan orogeny which dominates the geophysical architecture of the central northern part of the craton the youngest phase of deformation in the craton is expressed by reactivation of shear zones between ca 1470 and 1450 ma and regional cooling

geomorphologic and paleoclimatic evidence of holocene glaciation on mount olympus greece this study investigates the possibility of holocene glaciation on mount olympus greece with a respective local temperature precipitation equilibrium line altitude tp ela at c 2200m a s l based on geomorphologic and paleoclimatic evidence at present the local tp ela is situated above the mountain s summit c 2918 m a s l but permanent snowfields and ice bodies survive within megala kazania cirque between c 2400 and c 2300 m a s l because of the cirque s maritime setting that results from its close proximity c 18km to the aegean sea and of the local topographical controls the snow and ice bodies occupied a considerably larger area and attained a stabilization phase between ad 1960 and 1980 also manifested from aerial photographs a period characterized by increased winter precipitation pw with subsequent tp ela depression to c 2410m a s l mid to late 20th century pw and tp ela variations exhibit negative correlations with the winter north atlantic oscillation index naow at annual and multidecadal 30 years timescales late holocene ad 1680 1860 reconstructed summer mean temperatures were lower by ts 1 1 c in relation to the reference period between ad 1960 and 1980 and were also superimposed to negative naow phases thus bracketing this time interval as a favorable one to glacial formation and or advance millennial scale annual precipitation reconstructions at the hypothesized tp ela c 2200m a s l point the period between 8 and 4 kyr bp as another glacier friendly candidate the mid holocene rather simplistic sequence of potential glacial advance phase was disturbed by short lived cold climatic deteriorations well documented over the northern aegean region that may partly explain the multicrested shape of the highest c 2200 m a s l morainic complex of megala kazania cirque

one thousand seven hundred years of interaction between glacial activity and flood frequency in proglacial lake muzelle western french alps local glacial fluctuations and flood occurrences were investigated in the sediment sequence of proglacial lake muzelle based on geochemical analysis and organic matter content established using loss on ignition and reflectance spectroscopy we identified six periods of increased glacial activity over the last 1700 yr each is in accordance with records from reference glaciers in the alps a total of 255 graded layers were identified and interpreted as flood deposits most of these occurred during glacial advances such as the little ice age period and exhibit thicker deposits characterized by an increase in the fine grain size fraction fine sediment produced by glacial activity is transported to the proglacial lake during heavy rainfall events the excess of glacial flour during these periods seems to increase the watershed s tendency to produce flood deposits in the lake sediment suggesting a strong influence of the glacier on flood reconstruction records thus both flood frequency and intensity which is estimated based on layer thickness as a proxy cannot be used in reconstruction of past extreme events because of their variability there is a need to take into account changes in sediment supply in proglacial areas that could preclude satisfactory interpretation of floods in terms of past climate variability

feldspar evolution in the roxby downs granite host to fe oxide cu au u mineralisation at olympic dam south australia abstract the textural relationships and geochemistry of feldspars from least altered to sericite hematite altered and mineralised 1 595 ga roxby downs granite rdg at olympic dam south australia were examined the sample suite is representative of rdg both distal 5 km and proximal 27 34 is recognised along with a more abundant less calcic plagioclase an 12 20 both displaying rapakivi and anti rapakivi textures with alkali feldspar alkali feldspars or 55 ab 43 an 2 record post magmatic evolution from cryptoperthite to patch perthite subsequent patch perthite is overprinted by highly porous near end member albite and k feldspar while plagioclase undergoes replacement by albite sericite ba rich k feldspar in sericite hematite altered and mineralised rdg along the margin of the odbc sericite replaces all plagioclase whereas red stained fe rich k feldspar persists sulphide uranium rare earth element mineralisation is observed in association with hydrothermal feldspars and increases in abundance with proximity to the orebody petrographic observations and whole rock geochemistry illustrate the transformation of plagioclase and alkali feldspar from igneous to hydrothermal processes and indicate that hydrothermal albite and k feldspar formed within the rdg without the need for an external source of alkalis feldspar geothermometry indicates a minimum crystallisation temperature of 765 c at 2 2 kbar for alkali feldspar pressure estimate obtained using plagioclase amphibole geobarometry followed by a range of lower temperature transformations late stage magma mixing contamination is postulated from supportive temperature and pressure estimates along with feldspar and mafic mineral relationships

petrography and geochemistry of granitoids from the samphire pluton south australia implications for uranium mineralisation in overlying sediments abstract the blackbush uranium deposit jorc inferred resource 12 580 tonnes u located on the north eastern eyre peninsula is currently the only sediment hosted u deposit investigated in detail in the gawler craton uranium is hosted within eocene sandstone of the kanaka beds overlying mesoproterozoic granites of the samphire pluton affiliated with the hiltaba intrusive suite 1 6 ga these are considered the most probable source rocks for uranium mineralisation by constraining the petrography and mineralogy of the granites insights into the post emplacement evolution can be gained which may provide an exploration indicator for other sediment hosted uranium systems three geochemically distinct granite types were identified in the samphire pluton and correspond to domains interpreted from geophysical data all granites show complex alteration overprints and textures with increasing intensity closer to the deposit as well as crosscutting veining alkali feldspar has been replaced by porous k feldspar and albite and plagioclase is overprinted by an assemblage of porous albite sericite calc silicates prehnite pumpellyite and epidote this style of feldspar alteration is regionally widespread and known from hiltaba aged granites associated with iron oxide copper gold mineralisation at olympic dam and in the moonta wallaroo region in two granite types biotite is replaced by calcic garnet calc silicates are indicative of ca metasomatism sourced from the anorthite component of altered plagioclase minor clay alteration of feldspars is present in all samples mineral assemblages in veins include quartz hematite hematite coffinite fluorite quartz and clay minerals minor chlorite and sericite are found in all vein types all granite types are anomalously rich in u concentrations between 10 and 81 ppm highly variable th u ratios as well as hydrothermal u minerals mostly coffinite in granites and veins are clear evidence for u mobility uranium may have been preconcentrated in veins in the upper parts of the pluton and was subsequently leached after deposition of the sediment

quartz spessartine metasediments coticules and their protoliths in north wales thin beds and small pods of quartz spessartine metasediments coticules occur in pelites of the gamlan formation cambrian of the harlech dome the original microfabric of these sediments has been largely destroyed by recrystallization under low greenschist facies conditions the quartz spessartine pods occur throughout the pelites and appear to have formed by the metamorphism of diagenetic mn carbonate concretions the thin beds of quartz spessartine rock appear to have formed by the metamorphism of a protolith which was deposited rapidly and repeatedly over a wide area although there is no direct evidence of the nature of this protolith the presence of altered mn carbonate rich tuff beds in anchizonal mudstones of similar age in the st tudwal s peninsula suggests that the bedded quartz spessartine rocks are in fact metamorphosed mn carbonate rich tuff units both the bedded and podiform quartz spessartine metasediments appear to have formed by reaction between clay minerals and mn carbonates of earlier diagenetic origin