constraints on the deep structure and dynamic processes beneath the alps and adjacent regions from an analysis of gravity anomalies summary gravity anomalies including terrain corrections over the western alps and the molasse basin are within 30 mgal of those calculated assuming local airy isostatic equilibrium but isostatic anomalies over regions nw and se of the alps exceed 50 mgal therefore mass excesses and deficits that must be supported by the strength of the lithosphere or by dynamically induced stress in the asthenosphere appear to be greater beneath the areas surrounding the alps than beneath the alpine chain itself attempts to account for the gravity gradient over the molasse basin and sub alpine chains and the small bouguer anomalies measured over the elevated areas of the vosges and black forest by the flexure of an elastic plate require an absurd set of parameters the high elevations of the vosges and the black forest are presumably due to high temperature in the underlying uppermost mantle but the deviations from isostatic equilibrium as well as the high temperature probably result from active upwelling in the asthenosphere beneath this area the absence of large isostatic anomalies over the alps and the failure of an elastic model to account for the gravity anomalies over the molasse basin suggest that the dynamic processes that flexed the european plate down to form the molasse basin and that built the alpine chain have waned the late cenozoic uplift of the molasse basin and the alps might be a consequence of a diminution or termination of downwelling of mantle material beneath the alps

quantifying the eocene to pleistocene topographic evolution of the soutwestern alps france and italy we evaluate the topographic evolution of the southwestern alps using eocene to pleistocene pollen data combined with existing sedimentological petrographic and detrital geo and thermochronological data we report 32 new pollen analyses from 10 sites completed by an existing dataset of 83 samples from 14 localities situated across the southwestern alps including both the pro and the retro foreland basins the presence of microthermic tree pollen mainly abies picea indicates that this part of the mountain belt attained elevations over 1900 m as early as the oligocene inferred rapid surface uplift during the mid oligocene coincided with a previously documented brief phase of rapid erosional exhumation when maximum erosion rates may have reached values of up to 1 5 2km myr slower long term average exhumation rates of 0 3km myr since the late oligocene helped maintaining the high alpine topography of the southwestern alps until today the relative abundances of meso microthermic tree pollen cathaya cedrusand tsuga and microthermic tree pollen abies picea in the pro and retro foreland basin deposits indicate that the present day asymmetric topography with a relatively gentle western flank and steeper eastern flank was established early in the southwestern alps at least since

recent climate driven river incision rate fluctuations in the mercantour crystalline massif southern french alps abstract we present a new geomorphological analysis of the tinee river tributaries in the southern french alps based on numerical inverse and forward modelling of their longitudinal profiles we model their relative uplift history with respect to the main channel hence the incision rate history of this channel inverse models show that all tributaries have consistent incision rate histories with alternating high and low values a comparison with global temperature curves shows that these variations correlate with quaternary climate changes we suggest that during warm periods a wave of regressive erosion propagates in the tinee river while its tributaries deeply incise their substratum to catch up with the falling base level we also show that the post 140 ka history of this landscape evolution is dominated by fluvial incision we then perform forward models of river incision and simulate the incision of the tinee river system over a time span of 600 ka this model allows us to extract time and space incision rate variations of the tinee river with a background of a few mm yr 1 incision rate can increase up to more than 1 cm yr 1 during short periods of time due to climatic oscillations this result is compatible with published cosmogenic nuclide based dating which evidenced incision rates from 0 2 to 24 mm yr 1 the part of the channel located between 12 and 20 km downstream from the source has undergone several periods of rapid incision rates which could explain the steep hillslopes and the triggering of a landslide 10 ka ago

emerald deposits and occurrences a review abstract emerald the green gem variety of beryl is the third most valuable gemstone after diamond and ruby although it is difficult to obtain accurate statistics colombia supplies most an estimated 60 worth more than 500 000 000 per year of the world s emeralds however there is speculation that the emerald mines in colombia are becoming depleted brazil currently accounts for approximately 10 of world emerald production emeralds have also been mined in afghanistan australia austria bulgaria china india madagascar namibia nigeria pakistan south africa spain tanzania the united states and zimbabwe because it is difficult to obtain accurate analyses of beryllium most published analyses of beryl are renormalized on the basis of 18 oxygen and 3 be atoms per formula unit the color of emerald is due to trace amounts of chromium and or vanadium replacing aluminum at the y site in most cases the cr content is much greater than that of v to achieve charge balance the substitution of divalent cations at the y site is coupled with the substitution of a monovalent cation for a vacancy at a channel site beryl is relatively rare because there is very little be in the upper continental crust unusual geologic and geochemical conditions are required for be and cr and or v to meet in the classic model be bearing pegmatites interact with cr bearing ultrama c or ma c rocks however in the colombian deposits there is no evidence of magmatic activity and it has been demonstrated that circulation processes within the host black shales were sufficient to form emerald in addition researchers are recognizing that regional metamorphism and tectonometamorphic processes such as shear zone formation may play a signi cant role in certain emerald deposits a number of genetic classification schemes have been proposed for emerald deposits most are ambiguous when it comes to understanding the mechanisms and conditions that lead to the formation of an emerald deposit studies of individual emerald deposits show that in most cases a combination of mechanisms magmatic hydrothermal and metamorphic were needed to bring be into contact with the chromophores this suggests the need for a more flexible classification scheme based on mode of formation stable isotopes can be used to estimate the contribution of each mechanism in the formation of a particular deposit such estimates could perhaps be more precisely defined using trace element data which should reflect the mode of formation emerald may be identified in the field by color hardness and form it will tend to show up in stream sediment samples but because its specific gravity is relatively low it will not concentrate in the heavy mineral fraction in colombia structural geology the sodium content of stream sediment samples and the lithium sodium and lead contents of soil samples have all been used to find emerald occurrences exploration for gem beryl could result in the discovery of new occurrences of non gem beryl or other be minerals that could become new sources of be and be oxide future efforts should go towards creating a comprehensive data base of emerald compositions including trace elements determination of the role of metamorphism in the formation of some emerald deposits improved classification schemes and more effective exploration guidelines

metallogeny of precious and base metal mineralization in the murchison greenstone belt south africa indications from u pb and pb pb geochronology the 3 09 to 2 97 ga murchison greenstone belt is an important metallotect in the northern kaapvaal craton south africa hosting several precious and base metal deposits central to the metallotect is the antimony line striking ene for over 35 km which hosts a series of structurally controlled sb au deposits to the north of the antimony line hosted within felsic volcanic rocks is the copper zinc line where a series of small ca 2 97 ga cu zn volcanogenic massive sulfide vms type deposits occur new data are provided for the malati pump gold mine located at the eastern end of the antimony line crystallizations of a granodiorite in the malati pump mine and of the baderoukwe granodiorite are dated at 2 964 7 and 2 970 7 ma respectively zircon u pb while pyrite associated with gold mineralization yielded a pb pb age of 2 967 48 ma therefore granodiorite emplacement sulfide mineral deposition and gold mineralization all happened at ca 2 97 ga it is thus suggested that the major styles of orogenic au sb and the cu zn vms mineralization in the murchison greenstone belt are contemporaneous and that the formation of meso to epithermal au sb mineralization at fairly shallow levels was accompanied by submarine extrusion of felsic volcanic rocks to form associated cu zn vms mineralization

long term fluvial incision rates and postglacial river relaxation time in the french western alps from 10be dating of alluvial terraces with assessment of inheritance soil development and wind ablation effects studying river long profile development as a response to tectonic and climatic controls requires reliable age dating of paleo profile remnants preserved as river terraces cosmic ray exposure cre dating often represents the only method available to date river terraces but the interpretation of cosmogenic nuclide concentrations is complicated by pre depositional inheritance and post depositional disturbance of the terrace deposits through pedogenesis and surface inflation or deflation here we use cosmogenic 10be measurements to date alluvial terraces in the french western alps in order to estimate river incision rates and to infer river response to climatic fluctuations and tectonic forcing we assess inheritance by constructing 10be concentration vs pebble depth profiles and use a monte carlo technique to estimate terrace ages we find that inheritance is negligible on all terraces enabling us to date terraces as young as 5 ky terraces that predate the last glaciation experienced intense pedogenesis and wind ablation which led to significant scatter in the 10be concentrations of surface samples we assess these effects using a model of 10be ingrowth and show that the oldest cre ages of surface clasts are close to the probable terrace age we study two catchments which have undergone varying degrees of glacial disruption the buech river experienced variations in runoff and sediment flux during the last glaciation as well as occasional ice dammings of its outlet its upper terraces record incision rates averaged over 190 ky of 0 8 mm yr consistent with denudation rates estimated in the surrounding areas and suggesting long term stability of river incision rates climatic forcing is well documented for the drac river which was repeatedly dammed by glaciers during cold periods its postglacial incision history was triggered by an 800 m drop in base level following ice dam disappearance long profile development by knickpoint propagation explains the time lag of 2 5 ky between this base level drop and terrace abandonment upstream as well as subsequent peak incision rates of 6 cm yr followed by a gradual decrease in incision rates the present knickpoint location 55 km upstream from the glacial damming site enables us to calculate a fluvial response time of 15 20 ky controlled by knickpoint propagation rates of several meters per year within the drac river

3 07 2 97 ga greenstone belt formation in the northeastern kaapvaal craton implications for the origin of the witwatersrand basin

climatic forcing on channel profiles in the eastern cordillera of the coroico region bolivia abstractorographic precipitation has a large impact on channel morphology and rock uplift via a positive feedback to erosion we show that in the eastern cordillera of bolivia channel concavities reach their highest values where annual precipitation increases in the downstream direction exceeding 3000 mm the steepest channels are upstream of this zone of high concavity where precipitation rates are 1000 mm yr 1 channels exhibit graded forms both upstream and downstream of this transient reach we conclude that the prolonged effect of orographic erosion and related tectonic uplift is the preservation of channels with extreme concavities in the eastern cordillera

spatial correlation between long term exhumation rates and present day forcing parameters in the western european alps the relative intensity of tectonic and climatic forcing in the western european alps has been a matter of debate since the recognition of a significant increase in denudation rates over the past few million years we address this question by quantitatively correlating the spatial pattern of long term exhumation rates with those of potential short term tectonic climatic and morphologic variables we find that present day rock uplift rates as measured by geodesy relative to a specific reference point and mean elevation are correlated with long term exhumation rates whereas relief present day precipitation discharge stream power and released seismic energy are not or are only weakly correlated we attribute the lack of correlation between long term exhumation and precipitation to a strong temporal variability in climate and erosional processes during pliocene pleistocene time the correlations among present day rock uplift rates present day elevations and long term exhumation rates suggest that rock uplift rates have been sustained for millions of years consistent with rock uplift rates being the isostatic response to crustal unloading the lack of a correlation of the released seismic energy with either rock uplift or long term exhumation denies active tectonics supporting evidence

rapid long term erosion in the rain shadow of the shillong plateau eastern himalaya abstract geodynamic models of collisional orogens suggest that precipitation gradients profoundly influence spatial patterns of exhumation and deformation in active collisional mountain ranges a basic tenet of this hypothesis is that in unglaciated areas spatial patterns of long term precipitation erosion and exhumation should be correlated a correlation of this type has been observed in the eastern himalaya where uplift of the shillong plateau by pliocene time drastically reduced monsoonal rainfall in the himalayan range downwind existing apatite fission track data suggest that the resulting precipitation gradient caused a twofold gradient in long term erosion rates across an area with similar geology suggesting a strong influence of climate on the region s geomorphic and tectonic evolution we extend this dataset by presenting 53 new bedrock apatite and zircon fission track ages from deeper within the rain shadow we expected latest miocene to pliocene apatite ages similar to previously published ages from neighboring areas in the rain shadow instead apatites as young as 1 3 0 2 ma and zircons as young as 4 5 1 0 ma 2 demonstrate that spatial gradients in precipitation do not correlate with variations in long term erosion and crustal strain as predicted by geodynamic models thermal kinematic modeling of these data suggests that local exhumation patterns reflect gradients in rock uplift dictated by fault kinematics in this rapidly deforming area despite a dramatic precipitation gradient these findings both highlight the need to better understand how erosive processes scale with precipitation amount and intensity in such settings and suggest a disconnect between the predictions of orogen scale geodynamic models and the relationship between erosion and tectonics at the regional scale

albitization in the antimony line murchison greenstone belt kaapvaal craton a geochemical and geochronological investigation abstract the 3 09 2 97 ga murchison greenstone belt is one of several archean volcano sedimentary belts within the kaapvaal craton in southern africa among the diverse ore deposits found within the belt a set of sb au deposits are located in a major quartz carbonate altered brittle ductile structure known as the antimony line the antimony line is thus clearly related to hydrothermal fluid circulation in this study we focus on albitites that run along the antimony line petrological and geochemical investigations indicate that albitization developed at the expense of a granodioritic protoliths under high fluid rock ratios and also that sb enrichment was concomitant with albitization oxygen isotopes on albitites point to a crustal origin for the hydrothermal fluid responsible for the albitization process geochronology on zircon and hydrothermal monazite identifies a 2 97 2 92 ga magmatic crystallization event disconnected from a ca 2 8 ga hydrothermal alteration and a potentially younger event around 2 0 ga these data highlight a likely magmatic related primary enrichment at 2 97 2 92 ga followed by a secondary metamorphic related mobilization event around 2 8 ga leading to a sb enrichment in the albitites and a last episode of alteration around 2 0 ga

high magnitude and rapid incision from river capture rhine river switzerland 1 landscape evolution is controlled by the development and organization of drainage basins as a landscape evolves drainage reorganization events can occur via river capture or piracy whereby one river basin grows at the expense of another the river downstream of a capture location will generate a transient topographic response as the added water discharge increases sediment transport and erosion efficiency this erosional response will propagate upstream through both the captured and original river basins here we focus on quantifying the impact of drainage reorganization along the rhine aare river system 45 000 km2 during the late pliocene early pleistocene where gravel remnants indicate total incision of 650 m during the last 4 2 myr in the region of the recent aare rhine confluence we develop a numerical model of drainage capture to quantify the range of possible magnitudes of erosion and the transient river response resulting from the reorganization of the rhine river the model accounts for both fluvial incision and sediment transport our model estimates 400 800 m of river elevation change lowering profiles during the last 4 myr due to river capture events providing an important component to the recent exhumation budget of the swiss alpine foreland the model indicates a rapid response to capture events re equilibration timescale of 1 myr the predicted incision magnitudes are consistent with incision measured from the elevation of pliocene and early pleistocene river gravels suggesting that across northern switzerland a significant amount of incision can be explained by drainage reorganization

post collisional sediment budget history of the alps tectonic versus climatic control based on the sediment budget of the eastern swiss and western alps since the oligocene the regional tectonic evolution has been identified as the dominant factor it is superimposed on the influence of both regional and global climate change and global sea level change during late pliocene and pleistocene times climate became the dominant factor because of cyclic glaciations the early post collisional history of the alps is characterized by a doubling of sediment discharge rates around the rupelian chattian boundary this increase is attributed to isostatic re adjustment either after large scale thermal reorganization of the lithosphere related to slab break off or to crustal thickening as continental crust became subducted from middle oligocene to late miocene times the overall trend of sediment discharge rates in the entire alps was modified only during relatively short lived phases these are characterized by an increase in aquitanian ca 23 21 ma and late burdigalian times ca 18 16 4 ma and a decrease in early to middle burdigalian 21 19 ma and langhian to serravalian times 16 4 12 ma an important still ongoing period of uplift reflected by rapidly increasing sediment discharge rates started in latest miocene times in the swiss and western alps and affected the eastern alps some 2 million years later the reason for this uplift is not clear but deep seated lithospheric processes appear to be likely

has focused denudation sustained active thrusting at the himalayan topographic front the geomorphic character of major river drainages in the himalayan foothills of central nepal suggests the existence of a discrete west northwest trending break in rock uplift rates that does not correspond to previously mapped faults the 40 ar 39 ar thermochronologic data from detrital muscovites with provenance from both sides of the discontinuity indicate that this geomorphic break also corresponds to a major discontinuity in cooling ages samples to the south are proterozoic to paleozoic whereas those to the north are miocene and younger combined these observations virtually require recent pliocene holocene motion on a thrust sense shear zone in the central nepal himalaya 20 30 km south of the main central thrust field observations are consistent with motion on a broad shear zone subparallel to the fabric of the lesser himalayan lithotectonic sequence the results suggest that motion on thrusts in the toe of the himalayan wedge may be synchronous with deeper exhumation on more hinterland structures in central nepal we speculate that this continued exhumation in the hinterland may be related to intense sustained erosion driven by focused orographic precipitation at the foot of the high himalaya

extensional neotectonics around the bend of the western central alps an overview the western alps active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive compressive tectonics along its borders we examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics numerical modeling gps morphotectonics fieldwork and brittle deformation analysis extension appears to be the dominant process in the present day tectonic activity in the western alps affecting its internal areas all along the arc shortening in contrast is limited to small areas located along at the outer borders of the chain strike slip is observed throughout the alpine realm and in the foreland the stress orientation pattern is radial for 3 in the inner extensional zones and for 1 in the outer transcurrent tranpressional ones extensional areas can be correlated with the parts of the belt with the thickest crust quantification of seismic strain in tectonically homogeneous areas shows that only 10 20 of the geodesy documented deformation can be explained by the alpine seismicity we propose that alpine active tectonics are ruled by isostasy buoyancy forces rather than the ongoing shortening along the alpine europe adria collision zone this interpretation is corroborated by numerical modeling the neogene extensional structures in the alps formed under increasingly brittle conditions a synthesis of paleostress tensors for the internal parts of the west alpine arc documents major orogen parallel extension with a continuous change in 3 directions from ene wsw in the simplon area to n s in the vanoise area and to nnw sse in the briancon area minor orogen perpendicular extension increases from n to s this second signal correlates with the present day geodynamics as revealed by focal plane mechanisms analysis the orogen parallel extension could be related to the opening of the ligurian sea during the early middle miocene and to compression rotation of the adriatic indenter inducing lateral extrusion

aseismic deformation in the alps gps vs seismic strain quantification neotectonics of the western and central alps is characterized by ongoing widespread extension in the highest zones of the chain and transcurrent compressive tectonics at the external limits of the belt the overall geodetically measured deformations also indicate extension across the western alps there is a good qualitative coherency between seismotectonic and geodetic approaches here we attempt to quantify the seismic part of the deformation the seismic strain is compared to the deformation derived from geodesy in sub areas of homogeneous seismic stress strain we computed the total seismic moment tensor and related strain tensor this study provides new quantitative elements about the ongoing geodynamic processes in the alpine belt the important discrepancies obtained between seismic strains and geodetically measured deformations raise the issue of aseismic deformation in the alps which could be related to elastic loading creeping and or a slower ductile style deformation

frost cracking control on catchment denudation rates insights from in situ produced 10be concentrations in stream sediments ecrins pelvoux massif french western alps the potential tectonic and climatic controls on erosion rates in the european alps and other mountain belts remain strongly debated we have quantified denudation rates at catchment scales using in situ produced cosmogenic nuclides 10be in stream sediments sampled at the outlets of twelve variously sized 27 1072 km2 catchments of the ecrins pelvoux massif french western alps with average elevations ranging from 1700 to 2800 m spatially averaged denudation rates corrected for potential shielding by little ice age glaciers vary from 0 27 0 05 to 1 07 0 20 mm yr on millennial timescales our results exhibit a correlation 2 0 56 between denudation rate and mean catchment elevation in the absence of significant correlation with any other morphometric parameters relief slope catchment size hypsometry etc although such variations in erosion rates have been previously linked to variations in tectonic uplift rate the relatively small size and tectonic homogeneity of our study area exclude a strongly variable tectonic control we interpret the increase in erosion rate with elevation as the effect of frost controlled processes which are strongly temperature dependent we use a one dimensional heat flow model driven by high resolution instrumental temperature records from the study area to correlate the variability in denudation rates with the integral of the absolute temperature gradient within the frost cracking window 3 to 8 c a proxy of the frost cracking intensity for each catchment the results imply that the efficiency of frost cracking constitutes a major control on catchment wide denudation rates in the study area explaining more than half the measured variability in these rates our study shows that present day denudation of the ecrins pelvoux massif is controlled by a climatically driven factor and suggests that frost cracking processes impose an important control on the post glacial topographic evolution of mid latitude mountain belts

potentially active faults in the rapidly eroding landscape adjacent to the alpine fault central southern alps new zealand 1 potentially active faults are exposed in the steep glaciated topography of the central southern alps new zealand immediately adjacent to the alpine fault plate boundary four major faults exposed along the flanks of three of the highest mountain ranges strike 10 23 km potentially 40 km nne oblique to the alpine fault dipping 57 12 nw in the opposite direction youngest discernable motions were reverse dip slip accommodating both margin perpendicular shortening and dextral margin parallel components of plate motion kinematic analysis yields a compression axis 295 10 9 trend or plunge equivalent to the contemporary shortening determined from seismological and geodetic studies suggesting the faults may be active although definitive evidence for recent movement or single event displacements is lacking there are 106 other potentially active faults mapped in central southern alps with strike lengths 4 73 km earthquake parameters were assigned from fault trace lengths and historical earthquake statistics indicating potential for mw 5 5 7 4 earthquakes at recurrence intervals of 1000 10 000 years such long recurrence intervals are consistent with the faults having little surface expression with rapid erosion of these seismically agitated mountains erasing any evidence of surface rupture during periods between earthquakes the central southern alps faults exemplify the difficulty in fully deciphering long term e g holocene or quaternary records of seismicity in tectonically active regions with rapidly evolving landscapes although there may be little evidence of surface ruptures remaining in the landscape the faults are still an important potential source of earthquakes and seismic hazard

decoupling of erosion and precipitation in the himalayas the hypothesis that abrupt spatial gradients in erosion can cause high strain rates in active orogens has been supported by numerical models that couple erosional processes with lithospheric deformation via gravitational feedbacks1 2 3 most such models invoke a stream power rule in which either increased discharge or steeper channel slopes cause higher erosion rates spatial variations in precipitation and slopes are therefore predicted to correlate with gradients in both erosion rates and crustal strain here we combine observations from a meteorological network across the greater himalaya nepal along with estimates of erosion rates at geologic timescales greater than 100 000 yr from low temperature thermochronometry across a zone of about 20 km length spanning the himalayan crest and encompassing a more than fivefold difference in monsoon precipitation significant spatial variations in geologic erosion rates are not detectable decreased rainfall is not balanced by steeper channels instead additional factors that influence river incision rates such as channel width and sediment concentrations must compensate for decreasing precipitation overall spatially constant erosion is a response to uniform upward tectonic transport of greater himalayan rock above a crustal ramp

relation between rock uplift and denudation from cosmogenic nuclides in river sediment in the central alps of switzerland 1 a north south traverse through the swiss central alps reveals that denudation rates correlate with recent rock uplift rates in both magnitude and spatial distribution this result emerges from a study of in situ produced cosmogenic 10be in riverborne quartz in central alpine catchments as a prerequisite we took care to investigate the potential influence of shielding from cosmic rays due to snow glaciers and topographic obstructions to calculate a possible memory from last glacial maximum lgm glaciation and to identify a watershed size that is appropriate for systematic sampling mean denudation rates are 0 27 0 14 mm a for the alpine foreland and 0 9 0 3 mm a for the crystalline central alps the measured cosmogenic nuclide derived denudation rates are in good agreement with post lgm lake infill rates and are about twice as high as denudation rates from apatite fission track ages that record denudation from 9 to 5 ma in general denudation rates are high in areas of high topography and high crustal thickness the similarity in the spatial distribution and magnitude of denudation rates and those of rock uplift rates can be interpreted in several ways 1 postglacial rebound or climate change has introduced a transient change in which both uplift and denudation follow each other with a short lag time 2 the amplitude of glacial to interglacial changes in both is small and is contained in the scatter of the data 3 both are driven by ongoing convergence where their similarity might hint at some form of long term quasi steady state or 4 enhanced continuous quaternary erosion and isostatic compensation of the mass removed accounts for the distribution of present day rock uplift

present day geodynamics in the bend of the western and central alps as constrained by earthquake analysis summary the contrasted tectonics of the western central alps is examined using a synthesis of 389 reliable focal mechanisms the present day strain regime is mapped and interpolated for the entire alpine belt based on a newly developed method of regionalization the most striking feature is a continuous area of extension which closely follows the large scale topographic crest line of the alpine arc thrusting is observed locally limited to areas near the border of the alpine chain a majority of earthquakes within the alps and its forelands are in strike slip mode stress inversion methods have been applied to homogenous subsets of focal plane mechanisms in order to map regional variations in stress orientation the stress state is confirmed to be orogen perpendicular both for 3 in the inner extensional zones and 1 in the outer transcurrent transpressional zones extensional areas are well correlated with the part of the belt which presents the thickest crust as shown by the comparison with the bouguer anomaly and the average topography of the belt in the northwestern swiss alps extension is also correlated with currently uplifting zones these observations and our strain stress analyses support a geodynamic model for the western alps in which the current activity is mostly a result of gravitational body forces earthquakes do not provide any direct evidence for ongoing convergence in the alpine system but a relationship with ongoing activity of complex block rotations of the apulian microplate cannot be ruled out

crustal uplift in the alps why the drainage pattern matters introductionmountain belts grow by accretion ofupper crustal material into the orogen icwedge fig 1 materialenteringthewedge gets deformed uplifted andexhumed basedontheoreticalmodels willett et al 1993 concluded thatorogensadoptadistinctgeometrywitha low tapered pro wedge facing thesubduction plate and a high taperedretro side this geometry establishesbecauseorogenstendtobeonthevergeof gravitational failure davis et al 1983 according to these models thevelocity eld of the crust and hence the exhumation path of rock particles depends on erosion at the surface e g horton 1999 consequently anychanges in erosion rates potentiallyresult in a modi cation of the patternof strain rates of surface erosion however depend on climate exposedlithologies the size of the catchmentarea thegeometriccon gurationofthedrainage basin and rates of crustaluplift tucker and slingerland 1996 although the impact of these para meters on surface erosion has beenstudied extensively using numericalmodels tucker and slingerland 1997 ku hni and p ffner 2001 schlu neggeret al 2001 verylittleattentionhas been paid to the in uence of thedrainage geometry on the spatial pat tern of erosion and on strain the central swiss alps provide anexample where the present daydrainage geometry reveals a distinctpattern that is characterized by largeorogen parallel dispersal systems therhone and rhine rivers fig 2a that drain the core of the alps and smaller orogen normal rivers according to the conceptual modelsoutlined above it is reasonable tospeculate that the asymmetry of thealpine drainage pattern is likely toin uence the pattern of crustal up lift speci cally the highest rates ofstrain release are expected in therhone and rhine valleys becausethe large drainage basins of theserivers are likely to result in enhancederosional potentials this hypothesiswill be tested in the following chap ters this present paper evaluates thepotential controls of the asymmetriccon guration of the alpine drainagepattern on possible variations oferosional potential as well as onpresent day and glacial sedimentyield this information is then rela ted to the published pattern ofcrustal uplift allowing possible pos itive feedback between surface ero sion and lithospheric forcing to beidenti ed the intention is not todiscard other processes as possiblecontrols on the pattern of crustaluplift e g exural rebound afterremoval of the pleistocene ice sheet kahle et al 1997 but rather topropose an alternative model thatmight enrich the range of possibleinterpretations pattern of crustal upliftand seismic activityfigure 2 a displays the recent verti cal movements of the swiss alpscomputed for rst order levellingbenchmarks relative to the benchmarkat aarburg gubler et al 1981 kahleet al 1997 the geodetic data wascollected repeatedly between c 1905and 1990 measured uplift is inter preted in terms of crustal upliftbecause benchmarks have not experi enced erosion i e they record theshort term velocity eld of upper most crustal levels the data indicatea considerable increase of crustaluplift rates from the foreland tothe rear of the alps where currentrates of 1 mm yr

water versus ice the competing roles of modern climate and pleistocene glacial erosion in the central alps of switzerland recent studies have identified relationships between landscape form erosion and climate in regions of landscape rejuvenation associated with increased denudation most of these landscapes are located in non glaciated mountain ranges and are characterized by transient geomorphic features the landscapes of the swiss alps are likewise in a transient geomorphic state as seen by multiple knickzones in this mountain belt the transient state has been related to erosional effects during the late glacial maximum lgm here we focus on the catchment scale and categorize hillslopes based on erosional mechanisms landscape form and landcover we then explore relationships of these variables to precipitation and extent of lgm glaciers to disentangle modern versus palaeo controls on the modern shape of the alpine landscape we find that in grasslands the downslope flux of material mainly involves unconsolidated material through hillslope creep testifying a transport limited erosional regime alternatively strength limited hillslopes where erosion is driven by bedrock failure are covered by forests and or expose bedrock and they display oversteepened hillslopes and channels there hillslope gradients and relief are more closely correlated with lgm ice occurrence than with precipitation or the erodibility of the underlying bedrock we relate the spatial occurrence of the transport and strength limited process domains to the erosive effects of lgm glaciers in particular strength limited rock dominated basins are situated above the equilibrium line altitude ela of the lgm reflecting the ability of glaciers to scour the landscape beyond threshold slope conditions in contrast transport limited soil mantled landscapes are common below the ela hillslopes covered by forests occupy the elevations around the ela and are constrained by the tree line we conclude that the current erosional forces at work in the central alps are still responding to lgm glaciation and that the modern climate has not yet impacted on the modern landscape

juvenile crust formation in the northeastern kaapvaal craton at 2 97 ga implications for archean terrane accretion and the source of the pietersburg gold abstract combined u pb and lu hf isotope data of detrital and magmatic zircon grains provide evidence that the murchison greenstone belt ne kaapvaal craton south africa hosts an important archean suture zone which primarily formed by a collision 2 97 ga ago between a back arc system to the north and an evolved terrane the proto kaapvaal craton to the south this model is supported by the observations that igneous rocks of the northern terrane comprising mafic rocks and tonalites of the rooiwater complex and felsic volcanics of the rubbervale formation were both emplaced at about 2 97 ga and show highly superchondritic hft of 4 4 to 5 1 in contrast u pb hf isotope data of detrital zircon grains from quartzitic schists of the murchison unit and the la france formation both part of the southern terrane provide evidence for a southern provenance which was affected by granitoid intrusions accompanied by crust re working at 3 53 3 42 ga hft 1 8 to 4 8 3 30 3 20 ga hft 1 8 to 6 3 and 3 13 3 05 ga hft 1 3 to 5 6 pointing to a connection with the barberton greenstone belt and swaziland a spatial separation of the two terranes prior to 2 97 ga is furthermore supported by the facts that the youngest detrital zircon grains of the southern terrane having ages between 2 99 and 2 97 ga show subchondritic hft between 6 5 and 1 5 in contrast to the highly superchondritic hft obtained from the contemporaneous magmatic rocks of the northern terrane the juvenile character of the rooiwater and rubbervale magmatic rocks along with the occurrence of vms deposits makes them a likely candidate for the source of the gold pyrite bearing conglomerates exposed in the adjacent pietersburg greenstone belt

u pb and pb pb isotopic studies relating to the origin of gold mineralization in the evander goldfield witwatersrand basin south africa abstract this study presents new u pb and pb pb isotopic data for the central rand group in the evander goldfield located in the eastern extremity of the witwatersrand basin single grain detrital zircon dating exhibits a more restricted range of u pb ages than has previously been published from elsewhere in the witwatersrand basin and a shift towards younger ages the oldest grain measured is c 3180 ma while the majority of detritus falls in the range 3050 2850 ma several zircon grains from the sheared and altered portions of the kimberley reef yield ages that are younger or similar to that of the overlying ventersdorp lavas these ages are attributed to partial or complete isotopic resetting of older detritus at some stages during the post depositional history of the basin the existence of both detrital and authigenic pyrites is also supported by pb pb isotopic data of the present study a small proportion of the pyrite mainly extracted from unaltered sediments in the kimberley reef footwall yield ages that are in excess of the minimum depositional age of the witwatersrand basin authigenic pyrite as well as detrital grains from highly altered portions of the kimberley reef define secondary isochrons at about 2370 ma and 2020 ma suggesting fluid circulation in the basin at approximately these times

active deformation in the eastern swiss alps post glacial faults seismicity and surface uplift abstract post glacial tectonic faults in the eastern swiss alps occur as single lineaments clusters of faults or extensive fault zones consisting of several individual faults aligned along the same trend the orientation of the faults reflects the underlying lithology and the pre existing structures joints pervasive foliations within these lithologies most post glacially formed faults in the area around chur which undergoes active surface uplift of 1 6 mm year trend e w and cut across alpine and glacial features such as active screes and moraines additionally there are nnw and ene striking faults reactivating pervasive alpine foliations and shear zones based on a comparison with the nodal planes of recent earthquakes e w striking faults are interpreted as active faults because of very short rupture lengths and mismatches of fault location with earthquake distribution magnitude and abundance the faults are considered to be secondary faults due to earthquake shaking cumulative deformation in post or interseismic periods or creep and not primary earthquake related faults the maximum of recent surface uplift rates coincides with the youngest cooling of the rocks according to apatite fission track data and is therefore a long lived feature that extends well into pre glacial times isostatic rebound owing to overthickened crust or to melting of glacial overburden cannot explain the observed surface uplift pattern rather the faults earthquakes and surface uplift patterns suggest that the alps are deforming under active compression and that the aar massif basement uplift is still active in response to ongoing collision

quaternary erosion induced isostatic rebound in the western alps the high elevation and deep incision of the alps have traditionally been used as an argument for recent tectonic activity that has elevated the belt and increased erosion rates normal faulting and horizontal extension however dominate current tectonic activity and isostatic compensation of thinning crust should lead not to increased but to decreased mean elevations here we test the idea that enhanced quaternary erosion of the alps and isostatic compensation of the mass removed can account for the distribution of present day geodetically measured rates of vertical movement in the western alps using geophysical relief and kuhlemann s estimated average erosion rate for the alps we quantify the spatial distribution of erosion and the volume of eroded rock respectively from these we obtain a map of rock eroded within a given time span the calculated isostatic response of the alpine lithosphere to erosional unloading for a variety of values of the flexural rigidity of the alpine lithosphere reaches a maximum of 500 m since 1 ma in the inner swiss alps and vertical movement extends across the entire belt including peri alpine basins assuming a steady erosion rate since 1 ma this rebound accounts for half of the measured vertical motion of 1 1 mm yr in the southern valais thus a significant fraction 50 of the present day vertical movement results from the isostatic response to enhanced erosion during plio quaternary time

pleistocene holocene climate change re establishment of fluvial drainage network and increase in relief in the swiss alps abstract data are presented about modern sediment discharge of the swiss rivers and related to the size of catchments the information reveals that the central alps have experienced denudation rates of 0 15 mm yr 1 in the foreland and 0 5 mm yr 1 in the alpine core mapping however indicates that modern erosion only affects 30 50 of the alpine surface and that fluvial and associated hillslope processes have focused erosion in 50 200 m deep valleys these valleys are incised into the glacial surface if this limited spatial extent of erosion is considered then effective erosion rates are significantly higher than average denudation rates these effective rates equal or locally exceed modern rates of rock uplift this implies that the modification of erosional processes related to the pleistocene holocene climate change has resulted in an increase in the relief at a local scale at a drainage basin scale however the relief appears not to change at present

late neogene erosion of the alps a climate driver as with many mountain belts globally the alps have seen a large increase in sediment yield in the late neogene the hypothesis that this increase results from climate change impacts on erosion rate over the past 5 ma is testable given the extensive work completed in the alps sediment budgets thermochronology based cooling rates and estimates of modern rock uplift and erosion in the western alps are reviewed to search for correlation in space and time that might fingerprint climatic events major increases in sediment yield are apparent starting in the late messinian 5 5 mya and accelerating toward the present day this suggests the occurrence of a series of climatic changes that increased erosion rates even as tectonic processes appear to have slowed or stopped at present tight correlations in time are difficult to establish and there remain open questions about the role of tectonics in the coupled system

structure and metamorphism of the archean murchison belt kaapvaal craton south africa critical examination of five popular prejudices applied to greenstone belts in general and the murchison belt in particular show that 1 the term murchison schist belt is preferred to that of murchison greenstone belt which differs significantly from the barberton greenstone belt 2 the murchison belt is tectonized such that no simple stratigraphy may be erected 3 the murchison belt lacks a synclinal keel 4 heterogeneous oblique to dip slip shear characterizes much of the murchison belt but strike slip deformation occurred in the letaba shear zone along the northeastern margin of the belt and 5 contact metamorphism was a limited phenomenon that was not responsible for the highest grade rocks of the murchison belt the belt comprises a number of domains each with its own characteristic lithologies structural style and metamorphic history bounded by tectonic breaks which have juxtaposed rocks from different crustal levels

cosmogenic 10be derived denudation rates of the eastern and southern european alps denudation rates from cosmogenic 10be measured in quartz from recent river sediment have previously been used in the central alps to argue that rock uplift occurs through isostatic response to erosion in the absence of ongoing convergence we present new basin averaged denudation rates from large rivers in the eastern and southern european alps together with a detailed topographic analysis in order to infer the forces driving erosion denudation rates in the eastern and southern alps of 170 1 400 mm ky 1 are within a similar range to those in the central alps for similar lithologies however these denudation rates vary considerably with lithology and their variability generally increases with steeper landscapes where correlations with topographic metrics also become poorer tertiary igneous rocks are associated with steep hillslopes and channels and low denudation rates whereas pre alpine gneisses usually exhibit steep hillslopes and higher denudation rates molasse flysch and schists display lower mean basin slopes and channel gradients and despite their high erodibility low erosion rates exceptionally low denudation rates are also measured in permian rhyolite which has high mean basin slopes we invoke geomorphic inheritance as a major factor controlling erosion such that large erosive glaciers in the late quaternary cold periods were more effective in priming landscapes in the central alps for erosion than in the interior eastern alps however the difference in tectonic evolution of the eastern and central alps potentially adds to differences in their geomorphic response their deep structures differ significantly and unlike the central alps the eastern alps are affected by ongoing tectonic influx due to the slow motion and rotation of adria the result is a complex pattern of high mountain erosion in the eastern alps which has evolved from one confined to the narrow belt of the tauern window in late tertiary time to one affecting the entire underthrust basement orogenic lid and parts of the southern alps today

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

glacial conditioning as an erosional driving force in the central alps unparalleled data availability in the european alps has led to an ongoing debate about the driving mechanism behind the concurrent patterns of surface denudation and modern rock uplift analysis of stream channels reveals that oversteepened stream segments are primarily located in landscapes with strong glacial inheritance this leads to a transient signal in the landscape with the result that erosion is spatially focused by a combination of glacial conditioning and lithologic controls we postulate that the effect of glacial forcing is a positive feedback cycle between erosion and rock uplift driving rapid rates of both in the alpine landscape this mechanism may explain the observed increases in sediment flux since the late pliocene

climate induced rebound and exhumation of the european alps foreland basins record the regional isostatic compensation of mountain belts during periods of crustal thickening they subside and when erosion unloads the mass of the mountains the basins rebound and are eroded in order to evaluate this mechanism for rebound it is critical that the timing and magnitude of erosion are documented we present data estimating the timing and magnitude of late orogenic or postorogenic erosion in the north alpine foreland basin of switzerland mineral cooling ages demonstrate that the basin underwent 1 3 km of erosion soon after 5 ma this erosion coincided with a decline in structural deformation in the swiss alps and a doubling of sediment accu mulation rates in surrounding depocenters we propose that accelerated erosional un roofing of the swiss alps triggered isostatic rebound and erosion of the foreland basin after 5 ma a projection of the isostatic rebound of the basin into the mountains suggests that at least 6 5 km of erosion should have occurred in the high topography of the aar massif accelerated erosion in the swiss alps at that time is explained by an increase in atmospheric moisture driven by an intensification of the atlantic gulf stream at 4 6 ma consequently we propose that the changing erosional capacity of the climate triggered late orogenic to postorogenic mass reduction and isostatic rebound of the swiss alps and their neighboring foreland basin

the exhumation of the western greater caucasus a thermochronometric study this study provides 39 new thermochronometric analyses from the western part of the greater caucasus a region in which existing data are extremely limited and of questionable quality the new results are consistent with field studies that identify triassic to middle jurassic cimmerian and oligo miocene alpine orogenic erosional events an inverse relationship between the fission track and depositional ages of oligo miocene sedimentary samples also implies some degree of eocene erosion of the greater caucasus and intermediate sediment storage cooling ages and field relationships within the core of the range west of mt elbrus require 5 km of permo triassic exhumation and restrict the overall amount of cenozoic exhumation to 2 5 km current exhumation rates are typically low and do not support a plio pleistocene increase in climate driven denudation high 1 km ma 1 rates of exhumation are restricted to the southern flank of the range in northwest georgia despite a general lack of significant seismicity within the study region this exhumation peak is close to the largest instrumentally recorded earthquake in the caucasus ms 7 0 this may suggest that exhumation is associated with the decoupling of the sedimentary succession from its crystalline basement in the southern part of the range and the inversion of the largely jurassic fill of the greater caucasus basin rates of exhumation are compatible with this being driven by active shortening further sampling and analysis are required to provide a higher resolution low temperature thermochronology of alpine exhumation to isolate the drivers for palaeogene dziruli massif cooling and uplift and to constrain better the extent of the current localized phase of rapid exhumation

structures related to the antimony line murchison schist belt kaapvaal craton south africa abstract sporadic epigenetic antimony gold mineralisation along the ene trending antimony line of the murchison schist belt is structurally controlled and spatially related to carbonated rock types with quartz carbonate veins in tension fractures the antimony line is a discontinuous zone of brittle ductile deformation and is locally oblique to lithological layering within a broad ductile shear zone this tectonically early d 1 shear zone has an oblique to dip slip reverse north side up movement sense with downward facing fold structures in the hangingwall later d 2 fold structures deformed the antimony line and its wallrocks into steep structures the antimony line is intruded by granitoids which post date d 1 and are not directly related to mineralisation the source of which may have been metamorphic fluids

the last erosional stage of the molasse basin and the alps we present a synoptic overview of the miocene present development of the northern alpine foreland basin molasse basin with special attention to the pattern of surface erosion and sediment discharge in the alps erosion of the molasse basin started at the same time that the rivers originating in the central alps were deflected toward the bresse graben which formed part of the european cenozoic rift system this change in the drainage direction decreased the distance to the marine base level by approximately 1 000 km which in turn decreased the average topographic elevation in the molasse basin by at least 200 m isostatic adjustment to erosional unloading required ca 1 000 m of erosion to account for this inferred topographic lowering a further inference is that the resulting increase in the sediment discharge at the miocene pliocene boundary reflects the recycling of molasse units we consider that erosion of the molasse basin occurred in response to a shift in the drainage direction rather than because of a change in paleoclimate climate left an imprint on the alpine landscape but presumably not before the beginning of glaciation at the pliocene pleistocene boundary similar to the northern alpine foreland we do not see a strong climatic fingerprint on the pattern or rates of exhumation of the external massifs in particular the initiation and acceleration of imbrication and antiformal stacking of the foreland crust can be considered solely as a response to the convergence of adria and europe irrespective of erosion rates however the recycling of the molasse deposits since 5 ma and the associated reduction of the loads in the foreland could have activated basement thrusts beneath the molasse basin in order to restore a critical wedge in conclusion we see the need for a more careful consideration of both tectonic and climatic forcing on the development of the alps and the adjacent molasse basin

messinian climate change and erosional destruction of the central european alps at the end of the miocene the european alps ceased outward expansion and tectonic uplift and exhumation shifted into the orogen interior this shift is consistent with a change from orogenic construction to orogenic destruction reflecting an increase in the ratio of erosional flux to accretionary flux the coincidence of this change with an increase in sediment yield from the alps suggests a climate driven increase in erosional flux the timing of deformation and sediment release from the southern alps indicates that the tectonic change occurred synchronous with the last phase of the messinian salinity crisis we attribute the increase in erosional flux to a climatic shift to wetter conditions throughout europe likely augmented by the base level fall that occurred during the mediterranean dessication this climate change is represented in the stratigraphic record by the lago mare deposits of the mediterranean salinity crisis

a modified least squares collocation method for the determination of crustal deformation first results in the swiss alps summary the calculation of recent crustal movements and the associated crustal deformation rely on a suitable interpolation of geodetic measurements with repetition cycles of years or decades and modern gps permanent networks a common interpolation methods is the least square collocation lsc lsc requires some a priori assumptions about the characteristics of the velocity field that is stocasticity in moritz s definition of lsc we present a novel approach called adaptative lsc alsc to the interpolation of non stochastic fields which encompass the traditional lsc and the block model as special cases this modified collocation method is based on the empirical estimation of a anisotropic and inhomogeneous covariance function of the interpolated field the method has been tested on synthetic data that simulate geodetic measurements over a triple plate junction and with real data from precise levelling measurements over the swiss alps in both cases alsc gave better and more stable results compared to lsc and other interpolation methods such as smoothed splines

tectonics controls on fluvial landscapes and drainage development in the westernmost part of switzerland insights from dem derived geomorphic indices abstract this work focuses particularly on the geomorphological evidence for the tectonic controls on the development of the present day fluvial landscapes in the westernmost part of switzerland the tectonic deformation was evaluated on the basis of a combined analysis of several classical geomorphic indices hypsometric curves and integrals transverse topographic symmetry index and channel s bottom gradients through high precision dem processing a new optimization strategy was applied for defining geomorphic anomalies related to tectonic activity along the channels of three rivers based on a combined investigation of topographic swath longitudinal profiles geological and geophysical observations the results show that the abnormally high values of hypsometric integral are spatially occurred on the hanging walls of thrust faults while abnormally low ones are spatially observed in the same locations of paleo ice stream pathways observations obtained from transverse topographic symmetry index display asymmetries in the most of the studied drainage basins with a predominant se direction of lateral migration this direction is in agreement with the dominant dip direction of the bedding planes within the study area abnormal changes in the channel s bottom gradients which almost coincide in space with pronounced change in the depth of the subsurface geologic layers and in the geophysical properties are marked by distinct topographic relief in areas where rivers flow above blind and emergent faults our analysis not only confirms that there is a significant tectonic control on the evolution of drainage systems but also revealed a possible evidence for the reactivation of some inherited faults

increase in late neogene denudation of the european alps confirmed by analysis of a fission track thermochronology database abstract a sharp increase in deposited sediment volume since pliocene times has been observed worldwide and in particular around the european alps this phenomenon has been linked to a rise in denudation rates controlled by an increase of either climatic or tectonic forcing observation of in situ cooling histories for orogens is critical to assess the reality of the inferred increase in denudation rates and to determine whether this phenomenon is widespread or localized at active tectonic structures we exploit the unique density of fission track ages in the western european alps to reconstruct cooling isoage surfaces and to estimate exhumation rates on the orogen scale between 13 5 and 2 5 ma our novel technique is based on the association of isoage contours with age elevation relationships it uses map view interpolation enabling a spatio temporal analysis of exhumation rates over the entire western alps the resulting exhumation histories reconstructed for eight areas of the western alps display strong similarities in timing and rates with orogen wide average denudation rates inferred from sediment volumes this consistency validates the use of both techniques for the study of an orogen characterized by strong relief and high recent exhumation rates we conclude that exhumation rates in the western alps have increased more than twofold since late miocene times this increase may have been locally modulated by the distinct response of different tectonic units

are the alps collapsing abstract orogenic collapse is a process that transfers gravitational potential energy from regions of high potential energy to regions of lower potential energy this transfer is classically considered to be accomplished by extension in the orogenic core and by synchronous shortening in foreland regions of the orogen not all extensional features in collisional mountain belts need however reflect orogenic collapse normal faulting thrust faulting and strike slip faulting are all active in different parts of the alps today and reflect complex local responses to ongoing europe adria convergence the western alps is the only area today where extension and shortening radial to orogen trend occur synchronously and where orogenic collapse may be an important process elsewhere in the alps normal faults are oriented at a high angle to orogen trend and were primarily active in oligocene and miocene time most present day activity in the central and eastern alps is on strike slip faults that are accommodati

contrasting tectonically driven exhumation and incision patterns western versus central nepal himalaya although the himalayan range is classically presented as cylindrical along strike segmentation of the range in terms of structure topography precipitation and erosion patterns is becoming widely recognized the potential climatic or tectonic controls on these lateral variations remain controversial thermokinematic models predict that the geometry of the main himalayan detachment controls the kinematics exhumation and topography of the orogen where the detachment includes a major crustal ramp the topography shows a steep gradient that focuses orographic precipitation and exhumation whereas the topography is gentler and exhumation less focused above a flatter detachment we test this prediction by comparing the patterns of river incision specific stream power and long term exhumation from apatite fission track thermochronology in central nepal where a major crustal ramp has been imaged by geophysical methods with new exploratory data from the remote karnali river transect in western nepal where a ramp is predicted to be absent or minor our results show that both exhumation rates and river incision capacity are significantly higher and focused on the crustal ramp in central nepal whereas they are lower and the pattern is more diffuse in western nepal these differences support a model in which lateral variations in topography and exhumation are controlled by variations in the geometry of the detachment and imply that along strike climatic variations in the himalaya respond to tectonics rather than driving it

stable isotopes c o and fluid inclusion study of quartz carbonate veins from the antimony line murchison greenstone belt in the homogeneously deformed murchison greenstone belt region fluids circulations were focused along a localized deformation brittle ductile zone and the so called antimony line in order to trace the origin of the fluid its composition the temperature of the precipitation along the antimony line we investigate the stable isotope oxygen and carbon and fluid inclusion compositions of the quartz carbonate veins as well as chemical analyses of the carbonates and 40ar 39ar dating on the fuchsite associated with the veins three types of fluid inclusions are recognized for the h2o co2 dominated plus minor ch4 n2 fluid s microthermometric measurements together with the paragenesis of the veins and host rocks indicate that the pressure temperature of the precipitation is 350 to 450 c 200 to 300 mpa which is an unusually high temperature for an antimony deposit the carbonates are fe mg rich and are characterized by flat mree and hree patterns with slight depletions in lree the oxygen isotope compositions of the quartz are rather homogeneous at the scale of the antimony line 18oquartz 10 9 14 3 in detail subtle differences in the 18o values for the quartz and carbonate exist depending on the sampling sites these differences are likely due to minor temperature and or host rock geochemistry variations along the antimony line data point to a metamorphic origin for the fluids responsible for the mineralization which likely escaped from the nearby greenstone lithologies finally we present an overview of the murchison greenstone belt geological evolution by integrating the antimony metallogeny of the antimony line which can be compared to that of an orogenic gold deposit