shear stress in the graphitization of carbonaceous matter during the low grade metamorphism from the northern parang mountains south carpathians implications to graphite geothermometry abstract low grade metamorphic rocks from the northern parang mountains south carpathians were examined to infer the temperature of metamorphism and to obtain new data to study the applicability of the geothermometers relying on the graphite crystallinity to rocks that underwent different shear stress conditions there were analyzed samples of graphitic carbonaceous matter bearing rocks that exposed dissimilar degrees of strain for which the temperature of metamorphism was calculated using the graphite geothermometers based on the lattice parameter c0 determined through x ray diffractometry and based on the peak area ratio of the first order raman spectrum the temperature was also inferred from the chemical composition of the chlorite and from the fe mg partitioning between chlorite and chloritoid the mineral chemistry being determined through electron microprobe analyses the results obtained have shown i differences of up to more than 150 c between vicinal strained and less strained zones when applying the geothermometers based on the graphite crystallinity and ii considerable discrepancies between the temperatures calculated based on the graphite crystallinity and those based on the chlorite and chloritoid chemical compositions these inconsistencies are most likely caused by the fact that the calibration of the graphite geothermometers considers temperature as being exclusively responsible for enhancing the degree of graphite crystallinity and therefore these graphite geothermometers should be adjusted accordingly by introducing a correction factor that quantifies the degree of strain of the samples analyzed in order to obtain more accurate results

geophysical geological transect and tectonic evolution of the swiss italian alps a complete alpine cross section integrates numerous seismic reflection and refraction profiles across and along strike with published and new field data the deepest parts of the profile are constrained by geophysical data only while structural features at intermediate levels are largely depicted according to the results of three dimensional models making use of seismic and field geological data the geometry of the highest structural levels is constrained by classical along strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units because the transect is placed close to the western erosional margin of the austroalpine nappes of the eastern alps it contains all the major tectonic units of the alps a model for the tectonic evolution along the transect is proposed in the form of scaled and area balanced profile sketches shortening within the austroalpine nappes is testimony of a separate cretaceous age orogenic event west directed thrusting in these units is related to westward propagation of a thrust wedge resulting from continental collision along the meliata hallstatt ocean further to the east considerable amounts of oceanic and continental crustal material were subducted during tertiary orogeny which involved some 500 km of n s convergence between europe and apulia consequently only a very small percentage of this crustal material is preserved within the nappes depicted in the transect postcollisional shortening is characterized by the simultaneous activity of gently dipping north directed detachments and steeply inclined south directed detachments both detachments nucleating at the interface between lower and upper crust large scale wedging of the adriatic or apulian lower crust into a gap opening between the subduced european lower crust and the pile of thin upper crustal flakes alpine nappes indicates a relatively strong lower crust and detachment between upper and lower crust

petrology and geochronology of muscovite age standard b4m muscovite b4m distributed in 1961 as an age standard was ground under ethanol five grain size fractions were obtained and characterized by x ray diffraction they display a mixing trend between a phengitic enriched in the fraction 20 m high pressure phengite is preserved as a relict in retrograde muscovite electron microprobe analyses of the distributed mineral separate reveal at least four white mica populations based on si al mg na fe and f rb k ratios vary by one order of magnitude rb sr analyses link the mineralogical heterogeneity to variable rb sr and 87sr 86sr ratios the grain size fractions define no internal isochron relict fine grained phengite gives older ages than coarse grained retrograde greenschist facies muscovite the inverse grain size age relationship also characterizes 39ar 40ar analyses cl k anticorrelates with step ages cl rich coarse muscovite is younger than cl poor fine relict phengite sr and ar preserve a similar isotopic inheritance despite peak metamorphism reaching 635 20 c a suitable mineral standard requires that its petrological equilibrium first be demonstrated relicts and retrograde reaction textures are a guarantee of isotopic disequilibrium and heterogeneous ages within single crystal at the micrometre scale

protracted fluid induced melting during barrovian metamorphism in the central alps the timing and dynamics of fluid induced melting in the typical barrovian sequence of the central alps has been investigated using zircon chronology and trace element composition multiple zircon domains in leucosomes and country rocks yield u pb ages spanning from 32 to 22 ma the zircon formed during alpine melting can be distinguished from the inherited and detrital cores on the basis of their age th u 0 1 and trace element composition ti in zircon thermometry indicates crystallization temperatures around 620 700 c their composition allows discriminating between 1 zircon formation in the presence of early garnet 2 zircon in equilibrium with abundant l mree rich accessory phases allanite titanite and apatite typical of metatonalites and 3 zircon formed during melting of metasediments in feldspar dominated assemblages the distribution of zircon overgrowths and ages indicate that repeated melting events occurred within a single barrovian metamorphic cycle at roughly constant temperature that in the country rocks zircon formation was limited to the initial stages of melting whereas further melting concentrated in the segregated leucosomes that melting occurred at different times in samples a few meters apart because of the local rock composition and localized influx of the fluids and that leucosomes were repeatedly melted when fluids became available the geochronological data force a revision of the temperature time path of the migmatite belt in the central alps protracted melting over 10 my followed the fast exhumation of alpine eclogites contained within the same region and preceded fast cooling in the order of 100 c ma to upper crustal levels

metamorphic field gradients in the central alps metamorphic field gradients were determined across the entire amphibolite grade central alps c 50 100 km p t were calculated from 116 samples acquired from our own field work from samples provided to us by others and from rocks with mineral compositions described in the literature only fluid conserved equilibria were used to determine p t the use of an internally consistent thermodynamic database and mineral solid solution models makes the results robust and reduces relative errors the results are presented in contour maps temperature increases from 500 to 550 c along the limit of amphibolite grade metamorphism in the north and west to c 675 c toward the south at the insubric line near the town of bellinzona maximum recorded pressures of c 7 kbar are in a central region c 20 km north of the insubric line and decrease both to the north 5 5 kbar and south 4 5 kbar the p t results indicate that there is a relatively large area that reached conditions in the sillimanite stability field but developed neither sillimanite nor fibrolite this is interpreted as a result of kinetic constraints on nucleation and growth because of the small amounts of thermal overstep 40 c of the kyanite sillimanite phase boundary comparison of p t conditions with carbonate isograds in the region indicate that fluids present during metamorphism were not dominated by a homogeneous external source examination of the two dimensional distribution of pressure and temperature in the context of thermal and tectonic models indicates that two thermal pulses aected the central alps during the tertiary in the second heat aected only the southern parts of the area and overprinted the previously established p t gradients

salt crystallization in pores quantification and estimation of damage the objective of this study is to understand and predict the alteration of porous rock by crystallization of salts samples of different rocks have been tested according to the en 12370 standard test two parameters are proposed to evaluate the alteration of a rock during these tests the alteration index ai represents the cycle in which the first damages occur the alteration velocity av represents the alteration rate at the end of the experiment when the decay has become regular these parameters can be estimated with the help of a microstructural study of the rocks the most relevant intrinsic parameters of the stones for this estimation are capillary coefficient evaporation coefficient tensile strength and p waves velocity an evaluation of the alteration pattern is also proposed depending on the eventual heterogeneities and anisotropies of the rocks the influence of the dimension and shape of the samples is also discussed

cooling and uplift patterns in the lepontine alps south central switzerland and an age of vertical movement on the insubric fault line 96 new fission track ft apatite and zircon k ar and rb sr biotite and muscovite ages are presented for 19 samples mainly acid gneisses from a 40 km traverse through the lepontine alps in the maggia valley south central switzerland plotting measured mineral ages against assumed system closure temperatures yields cooling rates for each sample the entire profile shows a fairly uniform late neogene recent mean uplift rate of 0 5 mm a confirmed by a gradient of ft apatite age with elevation cooling from higher temperatures occurred earlier in the south where uplift rates of 2 2 mm a in the steep belt root zone indicate 9 km early miocene uplift of the northern pennine block this uplift started before 23 ma and is interpreted as resulting from a major phase of backthrusting along the insubric line and as dating the formation of the mylonite belt estimated cooling rates constrain the timing of lepontine mid tertiary metamorphism 3 schematic models are proposed which also consider published rb sr k ar mica and hornblende and u pb monazite ages slow cooling differential initial heating and subsequent cooling of different parts of the central alps and post 38 ma cooling with syntectonic metamorphism at 27 ma are postulated as alternative interpretations of isotopic data and geologic evidence from extrapolation between k ar and rb sr mica ages and apatite ft ages 240 50 c is proposed as the closure temperature for the retention of fission tracks in zircon

assessment of granitic rocks degradability susceptive to acid solutions in urban area granitic rocks have been used in wide range of studies when using these rocks the most important aspect to be considered is their weathering potential especially in acidic and wet environments in these conditions acid rainfall that is generated from atmospheric pollutions can accelerate the weathering trend of these rocks the aim of this article is to assess the relationship between the weathering processes and environmental conditions for this purpose four types of alvand granitic rocks were collected then using optical microscopy and x ray diffractometry the textural and mineral compositions of the rocks were studied as the second step the physical properties of these rocks were determined to assess the effect of ph on the degradability of rocks three solutions with different ph were prepared by adding sulfuric acid finally slake durability test for each type in sulfuric acid with ph 2 5 4 and 5 5 up to 15 cycles was performed the results indicated that these rocks posses a very high durability and their use as building stones are recommended in spite of these facts long term effects such as the weathering process can cause serious problems to ancient buildings as in the inscription of darius

metamorphic rates in collisional orogeny from in situ allanite and monazite dating the prograde sequence of rare earth minerals recorded in metapelites during regional metamorphism reveals a series of irreversible reactions among silicates and phosphates in individual samples from the northern lepontine central alps allanite is partly replaced by monazite at 560 580 c relic allanite retains its characteristic growth zoning acquired at greenschist facies conditions 430 450 c coexisting monazite and allanite were dated in situ to delimit in time successive stages of the barrovian metamorphism in situ sensitive high resolution ion microprobe shrimp u th pb dating of allanite 31 5 1 3 and 29 2 1 0 ma and monazite 18 0 0 3 and 19 1 0 3 ma constrains the time elapsed between 430 450 c and 560 580 c which implies an average heating rate of 8 15 c m y combined with new fission track ages zircon 10 9 ma apatite 7 5 6 5 ma metamorphic rates of the entire orogenic cycle from prograde to final cooling can be reconstructed

deterioration mechanisms of tuffs in midas monument slightly weathered white and pink tuffs of the midas monument have deterioration problems in this study depths and characteristics of the weathering zones developed within the tuffs are investigated through optical microscopy x ray diffractometry xrd chemical analyses scanning electron microscopy sem and some index parameters accelerated weathering tests including wetting drying freezing thawing and salt crystallization are performed and durability assessment methods are used to predict the durabilities of the tuffs the findings are compared with field observations by examining quantitative weathering indices and comparing them with thin section studies it is found that thin section analyses of the crystals loi and wpi are good indicators to quantify the depth of weathering for the tuffs however thin section studies have limited value for fine grained tuffaceous matrix the chemical weathering of the tuffs produces weathered zones that are 4 5 cm thick within the white tuff and 2 5 cm thick within the pink tuff physical weathering causes scaling of outer layers of the tuffs and fracturing of feldspars along their cleavage planes however variations of the index properties of the tuffs due to weathering are not so significant to quantify the weathering depths in the tuffs among the accelerated weathering tests salt crystallization is found to be the most destructive environmental condition pigeon droppings rich in no3 are found to be the main source of soluble salt at the midas monument the salt transported up by capillary rise due to surface water causes spalling of the tuffs in the capillary zone surface water and salt of any kind in the close vicinity of the monument should be totally eliminated for the purpose of conservation field observations and the durability equations reveal that the white tuff is less durable than the pink tuff wet to dry strength ratio yields a better stone durability assessment among various durability methods used in this study d 2002 elsevier science b v all rights reserved

influence of pore morphology on the durability of sedimentary building stones from aragon spain subjected to standard salt decay tests the aim of the present article is to identify the influence of the pore morphology on the physical behaviour and durability of natural stone fifteen sedimentary rocks commonly used in the cultural and architectural heritage of aragon spain were characterized the petrography porous structure fluid transport properties and durability of these rocks were analysed they were classified into two different groups according to the results of the different tests for each of these groups the physical behaviour was established a principal components analysis was used in order to examine the correlation between pore structure hydric properties and durability the results show that the percentage of pore throats 0 1 m control the fluid transport properties have an important influence on stone durability and can be used to predict resistance to salt decay while the average pore size does not stones with a high percentage of pore throats 0 1 m are less susceptible to salt decay than stones with higher pore size if their pore network is characterized by high tortuosity and low connectivity

characterising the u th pb systematics of allanite by id and la icpms implications for geochronology abstract allanite has the potential to be a useful chronometer of crustal evolution forming in response to a wide spectrum of metamorphic and magmatic conditions and incorporating weight percent concentrations of lree th and u despite its growing use in in situ u th pb geochronology allanite reference materials lack sufficient u th pb isotopic characterisation and little is known concerning the response of u th pb systematics of allanite to hydrothermal alteration and self irradiation this contribution presents the results of a combined id tims and la icpms u th pb study on a suite of five allanite crystals spanning 2 6 ga and including three commonly used allanite reference materials the siss bona and tara allanites siss and bona allanites preserve an inherited ca 1 ga pb component consistent with the presence of xenocrystic allanite cores or the presence of zircon micro inclusions tara allanite yields concordant u pb ages 407 430 ma but is affected by th u fractionation likely caused by hydrothermal alteration additionally the tendency for th to become mobilised post crystallisation is further evidenced by two precambrian allanite megacrysts le40010 ca 2 8 ga and le2808 ca 1 1 ga that both exhibit discordant th pb analyses linked to the formation of thorite micro inclusions along hydration pathways self irradiation dose versus discordance relationships show that a percolation threshold is present in allanite at cumulative dose values close to 3 10 17 decay g 1 an order of magnitude smaller than zircon collectively the presence of common pb and excess 206 pb its susceptibility to incur th u fractionation and hydrothermal pb loss complicates the use of allanite as a geochronometer these factors explain dispersion of 4 in the isotopic compositions of siss and tara allanites measured by la icpms providing a fundamental limit on the accuracy of the allanite chronometer using these reference materials

raman spectra of carbonaceous material in metasediments a new geothermometer metasedimentary rocks generally contain carbonaceous material cm deriving from the evolution of organic matter originally present in the host sedimentary rock during metamorphic processes this organic matter is progressively transformed into graphite s s and the degree of organisation of cm is known as a reliable indicator of metamorphic grade in this study the degree of organisation of cm was systematically characterised by raman microspectroscopy across several mesozoic and cenozoic reference metamorphic belts this degree of organisation including within sample heterogeneity was quantified by the relative area of the defect band r2 ratio the results from the schistes lustres western alps and sanbagawa japan cross sections show that 1 even through simple visual inspection changes in the cm raman spectrum appear sensitive to variations of metamorphic grade 2 there is an excellent agreement between the r2 values calculated for the two sections when considering samples with an equivalent metamorphic grade and 3 the evolution of the r2 ratio with metamorphic grade is controlled by temperature t along the tinos cross section greece which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks the r2 ratio is nearly constant consequently the degree of organisation of cm is not affected by the retrogression and records peak metamorphic conditions more generally analysis of 54 samples representative of high temperature low pressure to high pressure low temperature metamorphic gradients shows that there is a linear correlation between the r2 ratio and the peak temperature t c 445 r2 641 whatever the metamorphic gradient and probably the organic precursor the raman spectrum of cm can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism temperature can be estimated to 50 c in the range 330 650 c a few technical indications are given for optimal application

dating iron skarn mineralization using hydrothermal allanite la u th pb isotopes by laser ablation icp ms abstract trace elements and u th pb isotopes of hydrothermal allanite from the beiminghe iron skarn deposit eastern north china craton were simultaneously analyzed using laser ablation inductively coupled plasma mass spectrometry la icpms to demonstrate the suitability and robustness of the u th pb system in this phase as a geochronometer of ore forming processes allanite grains from the beiminghe deposit typically exhibit optical and chemical zoning and are intergrown or texturally equilibrated with prograde and or retrograde skarn assemblages mainly consisting of tremolite diopside magnetite and garnet in addition they contain abundant aqueous two phase or daughter mineral bearing three phase aqueous fluid inclusions confirming their hydrothermal origin most grains have high la ce ratios 1 19 1 74 and thus are classified as allanite la a notable feature of the hydrothermal allanite la is the lack of common pb with values comparable with those of the zircon standards 91500 and gj 1 used in this study la icpms spot analyses reveal remarkable variation in ca rees rare earth elements fe al and mg within a single grain consistent with the substitution of ree3 mg fe2 for ca al fe3 in the mineral structure traverses of zoned grains show that the rims have th u ratios ranging from 0 73 to 11 55 significantly higher than the core areas 0 07 1 81 fifty nine spot analyses beam size of 32 m or 60 m on 5 allanite la grains yield reproducible 206pb 238u ages of 134 7 to 139 6 ma with a weighted mean 206pb 238u age 206pbexcess corrected 206pb 238u age of 136 1 ma 2 of these 34 analyses on allanite rims have a weighted mean 208pb 232th age of 139 2 ma 2 that is within error of the 206pb 238u age the dating results showed that an increase of beam size from 32 to 60 m significantly reduces the analytical uncertainties 2 petrographic and textural data have demonstrated that the allanite la grains formed during skarn alteration and notably have close paragenetic relationships with retrograde skarn assemblages and iron oxide minerals their u th pb ages therefore are interpreted as the timing of iron skarn mineralization at beiminghe thirteen zircon grains from the ore related diorite intrusion have a weighted mean 206pb 238u age of 136 2 ma 2 consistent with and thus confirming the reliability of the allanite la u th pb ages when interpreted as the formation age of the beiminghe iron deposit our results suggest that hydrothermal allanite with low th and u is a promising u th pb geochronometer and can provide reliable constraints on the timing of hydrothermal mineralization without requiring a matrix matched external standard the present dating results also indicate that the u pb rather than th pb isotope system is preferable for u th pb dating of low th u allanite

high pressure low temperature metamorphism and deformation in the bundnerschiefer of the engadine window implications for the regional evolution of the eastern central alps a study of the metamorphic and tectonic evolution of the bundnerschiefer of the engadine window shows that the individual nappes have been thinned by a large amount and that extension was active during and soon after nappe stacking based on contrasting p t histories the penninic bundnerschiefer can be divided in two major units bounded by a horizontal contact the lower mundin unit shows typical high p low t parageneses in metapelites mg carpholite and in metabasites glaucophane metamorphic conditions are estimated around 12 kbar 375 c the upper arina unit contains no specific high p minerals metamorphic conditions are estimated around 7 kbar 325 c a minimum pressure gap of 5 kbar is thus observed the contact between the two units is marked by a mappable normal shear zone with top to the north west sense of shear near the shear zone fresh carpholite fibres trend parallel to the regional stretching lineation implying that the detachment is an early structure active from the depth of stability of the carpholite and persisting during subsequent exhumation the good preservation of carpholite and the absence of retrograde chloritoid below the shear zone show that exhumation occurred along a cooling path whereas the deeper units are exhumed along an isothermal path exhumation probably occurred during convergence and further nappe stacking during the earlier eocene these results suggest that pre collisional tectonic thinning of the penninic oceanic units may be more widespread and significant than generally recognized

pervasive eclogitization due to brittle deformation and rehydration of subducted basement effects on continental recycling the buoyancy of continental crust opposes its subduction to mantle depths except where mineral reactions substantially increase rock density sluggish kinetics limit such densification especially in dry rocks unless deformation and hydrous fluids intervene here we document how hydrous fluids in the subduction channel invaded lower crustal granulites at 50 60 km depth through a dense network of probably seismically induced fractures we combine analyses of textures and mineral composition with thermodynamic modeling to reconstruct repeated stages of interaction with pulses of high pressure hp fluid at 650 670 c rehydrating the initially dry rocks to micaschists sims oxygen isotopic data of quartz indicate fluids of crustal composition hp growth rims in allanite and zircon show uniform u th pb ages of 65 ma and indicate that hydration occurred during subduction at eclogite facies conditions based on this case study in the sesia zone western italian alps we conclude that continental crust and in particular deep basement fragments during subduction can behave as substantial fluid sinks not sources density modeling indicates a bifurcation in continental recycling chiefly mafic crust once it is eclogitized to 60 are prone to end up in a subduction graveyard such as is tomographically evident beneath the alps at 550 km depth by contrast dominantly felsic hp fragments and mafic granulites remain positively buoyant and tend be incorporated into an orogen and be exhumed with it felsic and intermediate lithotypes remain positively buoyant even where deformation and fluid percolation allowed them to equilibrate at hp

an investigation on the effect of accelerated weathering on strength and durability of tertiary sandstones qazvin province iran damages to stones induced by the action of freeze thaw and salt crystallization are considered to be of great importance in engineering construction these processes can influence the strength and durability of porous materials and consequently deteriorate them in this study the effects of freeze thaw f t and salt crystallization s c phenomena on strength and durability of upper red formation sandstones were investigated nine specimens of sandstones were collected from different parts of qazvin area iran and then their physical and mechanical characteristics were determined to assess the effect of f t and s c on physical and mechanical characteristics of sandstones 60 cycles of f t test and 20 cycles of s c test were performed physical and mechanical characteristics of these sandstones including wave velocity vp changes weight loss point load index and brazilian tensile strength were determined after different cycles for assessing the effect of freeze thaw and salt crystallization phenomena on slake durability index sdi of sandstones slake durability test was performed on specimens subjected to f t and s c then changes occurred in the sdi after 15 cycles were investigated finally the long term durability of sandstones against freeze thaw and salt crystallization action was evaluated using a decay function model this model postulates a first order process and provides some meaningful parameters such as decay constant and half life for the evaluation of long term durability of stones based on results obtained from current study it can be concluded that in comparison to freeze thaw salt crystallization can considerably reduce the strength and durability of sandstones also parameters obtained from decay function model showed that the rate of integrity loss is different for different weathering processes and stone durability can be predicted by this method with good accuracy

salt weathering influence of evaporation rate supersaturation and crystallization pattern micro and macroscale experiments which document the dynamics of salt damage to porous stone have yielded data which expose weaknesses in earlier interpretations previously unexplained differences are found in crystal morphology crystallization patterns kinetics and substrate damage when comparing the growth of mirabilite na2so4 10h2o and thenardite na2so4 versus halite nacl the crystallization pattern of sodium sulphate was strongly affected by relative humidity rh while a lesser rh effect was observed for sodium chloride macroscale experiments confirmed that mirabilite crystallizing at rh 50 per cent and thenardite crystallizing at rh 50 per cent tend to form subflorescence in highly localized areas under conditions of constant rh and temperature this crystallization pattern was more damaging than that of halite since halite tended to grow as efflorescence or by filling the smallest pores of the stone in a homogeneous fashion a result which contradicts wellman and wilson s theoretical model of salt damage low rh promoted rapid evaporation of saline solutions and higher supersaturation levels resulting in the greatest damage to the stone in the case of both sodium sulphate and sodium chloride crystallization at any particular crystallization condition sodium chloride tended to reach lower supersaturation levels resulting in the crystallization of isometric crystals and created negligible damage while sodium sulphate reached higher supersaturation ratios resulting in non equilibrium crystal shapes resulting in significant damage esem showed no damage from sodium sulphate due to hydration instead after water condensation on thenardite crystals rapid dissolution followed by precipitation of mirabilite took place resulting in stone damage by means of crystallization pressure generation it is concluded that salt damage due to crystallization pressure appears to be largely a function of solution supersaturation ratio and location of crystallization these key factors are related to solution properties and evaporation rates which are constrained by solution composition environmental conditions substrate properties and salt crystallization growth patterns when combined with a critical review of salt damage literature these experiments allow the development of a model which explains variations in damage related to combinations of different salts substrates and environmental conditions

ti diffusion in quartz inclusions implications for metamorphic time scales quartz inclusions in garnet from samples collected from the staurolite zone in central new england are zoned in cathodoluminescence cl the cl intensity is interpreted to be a proxy for ti concentration and the zoning attributed to ti diffusion into the quartz grains driven by ti exchange between quartz and enclosing garnet as a function of changing temperature the cl zoning has been interpreted using a numerical diffusion model to constrain the time scales over which the diffusion has occurred temperature time histories are sensitive to the presumed peak temperature but not to other model parameters the total time of the metamorphic heating and cooling cycle from around 450 c to the peak temperature 550 600 c back to 450 c is surprisingly short and encompasses only 0 2 2 million years for peak temperatures of 600 550 c the metamorphism was accompanied by large scale nappe and dome formation and it is suggested that this occurred as a consequence of in sequence thrusting resulting in a mid crustal ductile duplex structure

origins of yttrium and rare earth element distributions in metamorphic garnet highly variable distributions of yttrium and rare earth elements y rees are documented in pelitic garnet from the picuris mountains new mexico and from passo del sole switzerland and in mafic garnet from the franciscan complex california the wide variety of these y ree zoning patterns and those described previously in other occurrences imply diverse origins linked to differing degrees of mobility of these elements through the intergranular medium during garnet growth in the picuris mountains large early nucleating crystals have radial profiles of y ree dominated by central peaks and annular maxima in patterns that vary systematically with atomic number superimposed on these features are narrow spikes in hrees and mrees located progressively rimward with decreasing atomic number in contrast profiles in small late nucleating crystals contain only broad central maxima for all y rees in garnet from passo del sole y ree zoning varies radically from sample to sample in some rocks crystals of all sizes display only central peaks for all y rees in others profiles exhibit irregular fluctuations in y ree contents that match up with small scale patchy zoning in y and ca x ray maps in the franciscan complex y ree in garnet cores fluctuate unsystematically but mantles and rims display concentric oscillatory zoning for both major elements and y rees our interpretation of the complexity of y ree distributions in metamorphic garnet centres on the concept that these distributions vary primarily in response to the length scales over which these elements can equilibrate during garnet growth very short length scales of equilibration due to low intergranular mobility produce overprint zoning characterized by small scale irregularities higher but still restricted mobility yields diffusion controlled uptake characterized by patterns of central peaks and annular maxima that vary with atomic number and are strongly influenced by t t paths during garnet growth still greater mobility permits progressively greater potentially rock wide equilibration with major and accessory phase assemblages leading to mineralogical controls an unchanging mineral assemblage during garnet growth produces bell shaped profiles resembling those produced by rayleigh fractionation whereas changes in major and or accessory phase assemblages produce profiles with distinct annuli and sharp discontinuities in concentration the very high mobility associated with influxes of y ree bearing fluids can cause these element distributions to be dominated by factors external to the rock yielding profiles characterized by abrupt shifts or oscillations that are not correlated to changes in mineral assemblages

durability of carbonate rock as building stone with comments on its preservation carbonate rocks have been extensively used as building stones because of their availability workability and attractiveness unfortunately however some stones suffer from chemical attack or freeze thaw activity the environmental affects especially those due to pollution of the atmosphere are discussed in terms of weathering processes salt crystallization and acid deposition a review of some recent research in relation to deterioration of stone in urban environments is given and carbonate rocks are classified in relation to position within a building geographical location and degree of pollution some comments on stone preservation are provided especially in terms of the properties a preservative should possess

slake durability and mineralogical properties of some pyroclastic and sedimentary rocks abstract slake durability of rocks is an important property of rock mass and rock materials in geotechnical practice the slake durability of rocks is closely related to their mineralogical composition in this paper mineralogical examinations and slake durability tests for argillaceous clastic rocks especially pyroclastic rocks sandstones and mudstones of neogene tertiary age from japan were performed in order to assess the slake durability and rock alteration process of these rocks as well as to understand the relationship between mineralogy and durability the mineral composition and textural features of the rocks were studied by means of optical microscopy om x ray diffractometry xrd electron microprobe analysis epma and scanning electron microscopy sem in addition the slake durability test was carried out by using the standard testing method of isrm int j rock mech min sci 16 1979 148 in distilled water and in the aqueous solutions with dissolved electrolytes of nacl and cacl 2 the pyroclastic rocks and tuffaceous sandstone rich in di octahedral and tri octahedral fe smectite respectively show distinctively different slaking behaviors the pyroclastic rocks show relatively high slaking id 2 55 5 and id 10 10 5 than the tuffaceous sandstone id 2 94 1 and id 10 87 8 refer to text for id 2 and id 10 this difference in the slake durability observed in these rocks is due to the microscopic occurrences of smectite present in the interspaces between the particles pyroclastic rocks and zeolite cementing the interspaces tuffaceous sandstone as alteration minerals in addition the durability results of tuffaceous sandstone show that the slake durability decreases as the degree of weathering increases weathered material id 2 88 7 and id 10 65 3 furthermore two mudstones of miocene and pliocene ages having different clay mineral compositions smectite vs illite chlorite show the lowest and the highest slake durability among the tested clastic rocks hard mudstone shows the highest id 2 98 1 and id 10 95 5 while the soft mudstone shows the lowest id 2 33 9 and id 6 0 4 slake durability thus the slake durability of pyroclastic and sedimentary rocks is greatly affected by their mineral composition and texture and is closely related to their alteration history slake durability is also affected by the kind of dissolved electrolyte and its concentration in the aqueous solution providing some useful information for geotechnical practice

physical weathering of building stones induced by freeze thaw action a laboratory long term study damages to natural building stones induced by the action of frost are considered to be of great importance commonly the frost resistance of building stones is checked by standardised freeze thaw tests before using corresponding tests normally involve 30 50 freeze thaw action cycles in order to verify the significance of such measurements we performed long term tests on four selected rocks over 1 400 freeze thaw action cycles additionally numerous petrophysical parameters were analysed to compare the behaviour of rocks in the weathering tests according to the current explanatory models of stress formation by growing ice crystals in the pore space the long term tests yield more information about the real frost sensibility of the rocks a clear deterioration cannot be determined in most cases until 50 weathering cycles have been completed in the freeze thaw tests the samples are also stressed by changing temperature and moisture indicating that different decay mechanisms can interfere with each other thus thermohygric and moisture expansion are important damage processes

physical deterioration of sedimentary rocks subjected to experimental freeze thaw weathering ten types of sedimentary rock were subjected to repeated cycles of freezing and thawing in addition to monitoring sample weight loss throughout testing a detailed graphic record was made of deterioration mode and its relationship to pre existing rock flaws results suggest that the presence or absence of rock flaws alone does not control deterioration mode but rather that it is the coupled relationship between these flaws and rock strength and textural properties which exerts greatest influence while some pre existing flaws such as syndepositional deformation structures do not appear to influence breakdown others such as incipient fractures cavities and minor lithological boundaries frequently coincide with concentrations of deterioration a characteristic mode of deterioration which is independent of pre existing flaws tends to develop in sandstones indicating the influence in this case of rock texture particularly strong rocks such as crystalline limestone and metasediment tend to fracture preferentially along distinct linear weaknesses such as mineral veins stylolites and incipient fractures particularly weak rocks such as low density chalk break down in a random fashion without regard to pre existing flaws in addition to providing some insight into the role of pre existing flaws in rock deterioration this work also has practical implications for i the study of landform development due to weathering and ii the selection of representative rock samples in durability testing for building stone copyright 2000 john wiley sons ltd

slake durability study of shaly rock and its predictions more than 35 of the earth s crust is comprised of clay bearing rocks characterized by a wide variation in engineering properties and their resistance to short term weathering by wetting and drying phenomenon the resistance to short term weathering can be determined by slake durability index test there are various methods to determine the slake durability indices of weak rock the effect of acidity of water slaking fluid on slake durability index of shale in the laboratory is investigated these methods are cumbersome and time consuming but they can provide valuable information on lithology durability and weather ability of rock fuzzy set theory fuzzy logic and artificial neural networks ann techniques seem very well suited for typical complex geotechnical problems in conjunction with statistics and conventional mathematical methods a hybrid method can be developed that may prove a step forward in modeling geotechnical problems during this investigation a model was developed and compared with two other models i e neuro fuzzy systems combination of fuzzy and artificial neural network systems and artificial neural network system for the prediction of slake durability index of shaly rock to evaluate the performance of its prediction capability

the geologic history of vesta inferred from combined 207pb 206pb and 40ar 39ar chronology of basaltic eucrites abstract eucrites represent samples of mafic crust of the parent body likely vesta and record a complex geologic history involving magmatism metamorphism impact processing and metasomatism for better understanding of the geologic history we present combined 207pb 206pb and 40ar 39ar chronology of four basaltic eucrites showing distinct petrologic features agoult an equilibrated eucrite with granulitic textures camel donga a brecciated equilibrated eucrite enriched in metallic iron dag 380 a partially equilibrated monomict eucrite and nwa 049 a metasomatized polymict eucrite comprising mostly unequilibrated clasts the 207pb 206pb dating in combination with the acid washing technique was applied to pyroxene rich and plagioclase rich fractions while the 40ar 39ar dating was performed mainly on plagioclase grains using the laser incremental heating method the pb isotopic data for acid leaching residues are more radiogenic than those for acid washes reflecting efficient removal of non radiogenic pb components by the acid washing among the residues however only those of the agoult and camel donga plagioclase rich fractions yielded isochrons rather than errorchrons with 207pb 206pb ages of 4532 39 0 87 ma and 4515 43 0 42 ma respectively the trace element systematics further suggest that these residues essentially represent contaminant oxide minerals such as ilmenite and chromite rather than plagioclase on the other hand the ar isotopic data for agoult and camel donga yielded plateau ages with weighted means of 4494 9 ma and 3749 25 ma in contrast to those for dag 380 and nwa 049 that did not return any plateau the 207pb 206pb and 40ar 39ar ages of agoult are interpreted to reflect the time of the u pb and k ar system closure during a prolonged thermal metamorphism by combining the ages reported here and in the literature with the calculated closure temperatures the cooling rate of agoult is determined to be 11 2 c ma this cooling rate corresponds to a burial depth of 10 20 km indicating that granulitic eucrites were originally crystallized near the surface and were subsequently buried and metamorphosed the 20 ma younger 207pb 206pb ages of camel donga than agoult are considered to reflect delayed burial metamorphism in the source region whereas the plateau 40ar 39ar age would record the time of an impact causing brecciation and efficient ar degassing of the buried crust furthermore the model 207pb 206pb dates calculated for acid washed pyroxenes imply that the burial metamorphism of agoult and dag 380 were broadly contemporaneous and also that nwa 049 was metasomatized by fluids within the uppermost crust later than 4 4 ga

evolution of the ree mineralogy in hp lt metapelites of the sebtide complex rif morocco monazite stability and geochronology abstract ree mineralogy was characterized at the micrometer scale using scanning electron microscopy in the four tectono metamorphic units of the beni mzala window sebtide complex internal rif morocco which sample a hp lt metamorphic gradient from subgreenschist to blueschist eclogite facies these tectonic units are composed of garnet free metapelites and associated synmetamorphic veins from the same homogeneous aluminium rich and calcium poor protolith in that context mineralogical differences between units are assumed to result from contrasted pressure and temperature histories light ree bearing al phosphates of the crandallite group with florencite rich composition and variable goyazite content are the dominant lree minerals in the lowest grade units tizgarine 300 c 3 kbar as peak conditions and boquete de anjera 350 c 10 kbar in the latter unit metamorphic florencite is associated with mree rich monazite in the schist of the highest grade units beni mzala 2 420 450 c 12 kbar and beni mzala 1 550 c 16 kbar associations of allanite rich epidote and synchisite a lree fluorocarbonate are found whereas florencite and monazite are no longer observed at the wall of the quartz kyanite veins retrograde monazite ce with grain size of 20 to 50 m is the only lree bearing mineral th pb and u pb sims data on some of these grains yield ages of 21 3 1 7 ma and 20 9 2 1 ma respectively consistent with previous k ar ages obtained on retrograde clay mica mixtures in rocks from the same locality the identification of a stability field for monazite in high pressure aluminous metapelites with an upper thermal limit below 450 c as well as the derivation of meaningful u pb and th pb sims ages demonstrates the monazite potential for dating hp lt metapelites however since under these conditions monazite growth occurs below its admitted closure temperature these ages must be interpreted on the basis of monazite textural relationships

mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy 1 tectonic and metamorphic data for the central alps switzerland italy are used to discuss this classic example of a barrovian metamorphic terrain notably the evolution of its thermal structure in space and time available p t t data indicate variable contributions of advective and conductive heat transport during collision and subsequent cooling and exhumation some areas experienced a prolonged period of partial melting while other areas at the same time show but moderate heating the barrow type metamorphic field gradient observed in the final orogen is the result of two distinct tectonic processes with their related advective and conductive heat transport processes the two tectonic processes are 1 accretion of material within a subduction channel related to decompression and emplacement of high pressure units in the middle crust and 2 wedging and related nappe formation in the continental lower plate the second process postdates the first one wedging and underthrusting of continental lower plate material produces heat input into lower crustal levels and this process is responsible for predominantly conductive heat transport in the overlying units the interacting processes lead to different maximum temperatures at different times producing the final barrovian metamorphic field gradient the south experienced rapid cooling whereas the north shows moderate cooling rates this discrepancy principally reflects differences in the temperature distribution in the deeper crust prior to cooling differences in the local thermal gradient that prevailed before the cooling also determined the relationships between cooling rate and exhumation rate in the different areas citation berger a s m schmid m engi r bousquet and m wiederkehr 2011 mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy tectonics 30 tc1007 doi 10 1029 2009tc002622

3 d assessment of peak metamorphic conditions by raman spectroscopy of carbonaceous material an example from the margin of the lepontine dome swiss central alps this study monitors regional changes in the crystallinity of carbonaceous matter cm by applying micro raman spectroscopy to a total of 214 metasediment samples largely so called bundnerschiefer dominantly metamorphosed under blueschist to amphibolite facies conditions they were collected within the northeastern margin of the lepontine dome and easterly adjacent areas of the swiss central alps three dimensional mapping of isotemperature contours in map and profile views shows that the isotemperature contours associated with the miocene barrow type lepontine metamorphic event cut across refolded nappe contacts both along and across strike within the northeastern margin of the lepontine dome and adjacent areas further to the northeast the isotemperature contours reflect temperatures reached during the late eocene subduction related blueschist facies event and or during subsequent near isothermal decompression these contours appear folded by younger large scale post nappe stacking folds a substantial jump in the recorded maximum temperatures across the tectonic contact between the frontal adula nappe complex and surrounding metasediments indicates that this contact accommodated differential tectonic movement of the adula nappe with respect to the enveloping bundnerschiefer after maximum temperatures were reached within the northern adula nappe i e after late eocene time

on the causes and modes of exhumation and lateral growth of the alps 1 a compilation of the apatite and zircon fission track ages of the alpine chain points to markedly different patterns of cooling and exhumation of the eastern alps compared to the central and western alps the site of exhumation and shortening in the western alps migrated outward whereas it was more stationary in the eastern alps where it created a narrower metamorphic belt a correlation of these observations to the deep structure of the orogen suggests that north directed lower crustal wedging induces northward propagation of the deformation and exhumation front in the middle and upper crust of the central and western alps the absence of such lower crustal wedges in the eastern alps does not induce a similar shift of deformation but rather a long term localization of shortening and exhumation in one and the same area namely the axial zone of the orogen a critical review of the temporal correlations between inferred changes in the erosional efficiency of the alps and tectonic phases points to a negative correlation and hence no erosional control on the shifts of the deformation front of the alps therefore we conclude that changes in the deep structure and rheology of the orogen instead of changes in its erosional efficiency exerted the prime control on the lateral growth of the alps

physico chemical control on the ree minerals in chloritoid grade metasediments from a single outcrop central alps switzerland this study assesses the effects of fluid whole rock composition and oxygen fugacity on the texture and composition of monazite allanite and xenotime for this purpose these were investigated in 13 mono metamorphic metasediments from a single locality of the central alps switzerland which record greenschist facies conditions t 400 450 c two of the samples contain hydrothermal veins dominated by quartz and calcite quartz respectively in metasediments devoid of veins the light rare earth elements lree are concentrated in allanite in all samples except for one metamarl ga06 allanite formation is texturally coeval with apatite chloritoid and xenotime during the main tectono metamorphic stage allanite formation implies significant mass transfer of ca and p via a fluid phase which is not clearly related to advective transport in ga06 elongate monazite grains have a detrital core rimmed by newly formed monazite significant arsenic contents are found in newly formed monazite xenotime and apatite monazite texture and composition suggest re crystallization by pressure solution at an oxygen fugacity sufficient to partly oxidize as s u and fe whether or not monazite is preserved appears to be but weakly dependent on the ca al ratio and thus whole rock composition at greenschist facies conditions samples with veins show peculiar features along carbonate bearing veins allanite occurs as porphyroblasts overgrowing the main foliation of the host rock as similar allanite porphyroblasts occur in calcite bearing metamarl their formation is attributed to environments rich in co2 bearing fluid a new generation of monazite is found in and along retrograde quartz veins this study demonstrates that at least in metasediments up to chloritoid grade ree minerals record fluid rock interaction that occurred at different deformation stages arsenic concentrations in ree phosphates appear to reflect conditions of elevated oxygen fugacity in cases where such conditions are not inherited from the sedimentary protolith the oxidation reflects a hydrothermal event the age of which may be directly datable by u th pb of as rich monazite

collision tectonics in the swiss alps insight from geodynamic modeling this paper compares results from two dimensional finite element dynamic modeling with the kinematic evolution of the swiss alps during the collision phase in particular we investigate the role of inherited lateral strength heterogeneities on orogenesis a number of first order characteristics are directly comparable at crustal scales in the models the entry of continental crust into the convergent margin marks the end of near perfect subduction accretion of material of the subducting plate to the upper plate creates an orogenic wedge on the incoming pro side and initiates a retroshear zone or model backthrust the addition of material to the upper plate builds a bivergent orogen heterogeneities in the pro crust focus shear and lead to the development of nappe structures the combined action of pro shear nappe stacking and retroshear backthrusting uplifts a plug between the two shear zones subsequent focusing of shear along the retroshear zone results in rotation of the plug and overlying units leading to crustal scale backfolds as observed in the swiss alps the model experiments predict features relevant to alpine dynamics including 1 similar crustal thicknesses and exhumation patterns to those observed in the swiss alps today for erosion rates comparable to natural ones 1 mm yr 1 2 continued accretion and subduction of upper crustal fragments allowing high pressure metamorphic conditions 3 tilting and exhumation of lower crust when a midcrustal weak zone is present and 4 shunting of material across the strong lower crustal wedge of the upper plate

rare earth elements and sm nd isotope redistribution in apatite and accessory minerals in retrogressed lower crust material bergen arcs norway in the bergen arcs norway grenvillian granulite retrogressed under eclogite and amphibolite facies conditions during caledonian subduction collision offer a unique opportunity to investigate rare earth elements ree and sm nd isotope redistribution in accessory minerals during fluid assisted metamorphism our sampling targeted apatite bearing ree rich protoliths mangerite and jotunite that preserve distinct mineral assemblages depending on the external fluid availability and metamorphic conditions ree concentrations in apatite are the highest in the granulite two populations are present magmatic apatite ap1 relics that occur as inclusions in ilmenite hematite and intergranular apatite ap2 formed under granulite facies conditions the presence of abundant needle like monazite and sulphide inclusions in ap2 indicate that granulite reactions were fluid assisted a thin typically 10 m rim of ree rich epidote ep1 commonly surrounds ap2 in these accessory minerals u and th contents are too low or grains are too small for in situ u th pb dating sm nd isotope data of ap2 monazite and ep1 give an isochron age of 601 69 ma which is interpreted to represent a partially reset grenvillian age affected by caledonian fluid assisted mineral growth in amphibolitized samples granulite ap2 is replaced by apatite ap3 with lower ree contents and no monazite inclusions the ree released by this replacement are redistributed in a corona of epidote group minerals ep2 surrounding ap3 the in situ sm nd isotope data for ep2 and titanite found in replacement of ilmenite hematite return an isochron age of 395 65 ma recording the timing of amphibolite facies mineral growth when fluids were introduced into the rock in eclogitized samples eclogitic apatite ap4 occurs as polycrystalline aggregates suggesting for a complex replacement process during deformation ree contents of ap4 are low as ree originally contained in the precursor apatite were redistributed mainly into zoisite apatite shielded as inclusions in ilmenite and garnet preserve the ree rich signature of the initial magmatic ap1 and granulite ap2 apatite indicating these grains did not undergo further re equilibration during caledonian metamorphism the resistance of apatite to compositional re equilibration in this case confirms the petrological potential of apatite inclusions shielded in chemically inert minerals to track early magmatic or metamorphic crystallisation stages

the effect of ph of water and mineralogical properties on the slake durability degradability of different rocks from the lesser himalaya india slake durability is an important geotechnical parameter and is a measure of degradability of rocks due to the process of mechanical and chemical breakdown it is closely related to the mineralogical composition and the texture of the rocks in this paper mineralogical examination along with slake durability tests under variable ph conditions both in acidic and alkaline environments on the limestone shale and siltsone were evaluated to understand the relationship between mineralogy and the degradability of rocks the study revealed that rocks rich in calcium carbonate and or magnesium carbonate are adversely affected in the acidic environment whereas the rocks rich in quartz feldspar and muscovite are independent of the ph of the slaking fluid which in turn is more influenced by the texture of the constituent minerals it has also been observed that fine grained rocks are more susceptible to degrade in comparison to the coarse grained rocks

geochronology of accessory allanite and monazite in the barrovian metamorphic sequence of the central alps switzerland abstract the formation of accessory allanite monazite and rutile in amphibolite facies rocks across the barrovian sequence of the central alps switzerland was investigated with a combination of petrography and geochemistry and related to the known structural and metamorphic evolution of the lepontine dome for each of these minerals a specific approach was adopted for geochronology taking into account internal zoning and u th pb systematics in situ u th pb dating of allanite and monazite by ion microprobe revealed systematic trends for the ages of main deformation and temperature in the lepontine dome isotope dilution tims dating of rutile returns dates in line with this picture but is complicated by inheritance of pre alpine rutile and possible pb loss during alpine metamorphism allanite is generally a prograde mineral that is aligned along the main foliation of the samples and found also as inclusions in garnet prograde allanite formation is further documented by rutile inclusions with formation temperatures significantly lower than the maximum t recorded by the rock mineral assemblage allanite ages vary from 31 3 1 1 ma in orthogneisses in the east to 31 7 1 1 ma for a bundnerschiefer and 28 5 1 3 ma for a metaquartzite in the central area to 26 8 1 1 ma in the western part of the lepontine dome these ages are interpreted to date the main deformation events nappe stacking and isoclinal deformation of the nappe stack close to peak pressure conditions the timing of the thermal peak in the lepontine dome is recorded in monazite that grew at the expense of allanite and after a main episode of garnet growth at temperatures of 620 c monazite in the central area yields an age of 22 0 0 3 ma which is indistinguishable from the age of 21 7 0 4 ma from a metapelite in the western part of the lepontine dome in the central area some of the classical kyanite staurolite garnet schists directly underlying the metamorphosed mesozoic sediments contain monazite that records only a pre alpine variscan metamorphic event of upper greenschist to lower amphibolite facies conditions dated at 330 ma the new age data provide evidence that nappe stacking at prograde amphibolite facies conditions and refolding of the nappe stack occurred between 32 and 27 ma only a few million years after eclogite facies metamorphism in the adula cima lunga unit amphibolite facies metamorphism lasted for about 10 my to 22 ma allowing for multiple ductile deformation and recrystallization events the long lasting amphibolite facies metamorphism requires fast cooling between 20 and 15 ma in the central alps this fast cooling was not related to an increase in sedimentation rates in the foreland basins suggesting that tectonic exhumation was responsible for termination of amphibolite facies metamorphism in the lepontine dome

thermal and salt crystallization effects on marble deterioration examples from western anatolia turkey six commercially available and extensively used turkish marbles having different textural properties were subjected to ageing tests in order to assess their resistance against salt crystallization with thermal effect the change in physico mechanical properties of the marbles including weight dry unit weight effective porosity water absorption dry and saturated sonic velocities uniaxial compressive strength ucs indirect brazilian tensile strength flexural strength abrasion value and impact resistance has been determined for various stages of the ageing tests the results are evaluated in terms of the grain size grain boundary and grain size distribution of the marbles based on the test results the physico mechanical properties of the marbles are not uniformly affected from the ageing tests the water absorption effective porosity ucs sonic velocity and abrasion value of the marbles are found to be good parameters to assess the deterioration and quality of the marbles whereas the weight loss unit weight brazilian tensile strength and impact resistance of the marbles are not the marbles having small grain size dominant grain size distribution in a narrow range and irregular grain boundary are more resistant against the ageing tests than the ones with large grain size grain size distribution in a wide range and straight grain boundary

quantification of rock control in geomorphology abstract rock control the influence of rock properties on landform development has for long been a relatively under researched topic but numerous techniques have been developed especially by geotechnical engineers and stone conservationists that are now being applied to geomorphological issues by geomorphologists these techniques range in scale from the quantification of major discontinuities through to analysis of micro pores rock control studies that have taken place over the last few decades have contributed important insights into our understanding of such diverse phenomena as 1 river terraces bedrock channel forms and gradients pot hole development drainage density and gully badland development 2 slope forms and failures especially with respect to rock mass strength 3 the form of glacial troughs and of subglacial erosional landforms 4 weathering controls on rock durability and the association of weathering with porosity 5 classic karst features including various types of karren 6 sandstone landforms 7 inselbergs and tors and 8 cliffs and shore platforms

constraints on fluid evolution during metamorphism from u th pb systematics in alpine hydrothermal monazite abstract the timing and duration of hydrothermal activity during orogenesis are difficult to constrain because such systems are open and multistage using mm sized monazite crystals from two alpine clefts from the central alps switzerland we demonstrate that combined u th pb isotopic systematics of hydrothermal monazite can constrain both timing and fluid evolution during crystallization our data highlight four major characteristics of the cleft monazites i extreme th u ratios ii significant common pb in the u system up to 39 206 pb iii excess 206 pb up to 54 and iv precise and reliable th pb ages comparison of our results with literature data indicates that th u in monazite is a remarkable discriminant of geological conditions capable of distinguishing metasedimentary magmatic and hydrothermal origin hydrothermal monazite crystals are characterized by th u ratios up to 629 among the highest values ever reported extreme th u ratios in monazite enhance incorporation of 230 th a short lived intermediate product in the 238 u 206 pb decay chain generating 206 pb excess which if not accounted for results in 206 pb 238 u ages that are too old for example in the samples investigated here by as much as 300 for the two zoned monazite crystals studied in detail 208 pb 232 th ages are reliable for the different compositional domains visible in back scattered electron bse images 232 th 208 pb ages for the older domains 15 2 0 3 ma and 14 1 0 3 ma respectively are consistent with the structural relationships of the hydrothermal veins indicating early retrograde genesis the youngest rim age at 13 5 0 4 ma for the blauberg crystal marks termination of monazite precipitation the resolvable age difference is interpreted to reflect pulsed monazite growth over an extended period of hydrothermal activity in both crystals the outer rims have the highest 206 pb excess confirming a two stage crystallization two scenarios are envisaged to account for the 206 pb excess evolution in the first increasing 206 pb excess is caused by a modification of the th u fractionation between monazite and fluid due to an evolution of the fluid towards more oxidizing conditions that favor partitioning of hexavalent u into the fluid alternatively it is possible that 230 th increased with time in the fluid in this second case monazite growth would have occurred in a closed system from a fluid that was initially in disequilibrium with the 238 u 206 pb decay chain and progressively equilibrated t

solubility of cepo4 monazite and ypo4 xenotime in h2o and h2o nacl at 800 c and 1 gpa implications for ree and y transport during high grade metamorphism abstract monazite and xenotime are important accessory minerals in metasediments because they host ree and are useful for geochronology and geothermometry it is therefore essential to understand their behavior during metasomatic processes that attend metamorphism and subduction in order to constrain the solubility of monazite and ypo 4 xenotime at high pressure and temperature we carried out weight loss experiments on synthetic single crystals of cepo 4 monazite and ypo 4 xenotime using hydrothermal piston cylinder methods at 800 c and 1 gpa in h 2 o and h 2 o nacl fluids results indicate that cepo 4 and ypo 4 dissolved congruently and that their solubilities in pure h 2 o are very low 0 04 0 04 and 0 25 millimolal respectively the solubility of cepo 4 rises to an increasing extent with added nacl to 7 94 0 07 millimolal at 50 mol nacl in contrast the solubility of ypo 4 rises to a decreasing degree with increasing nacl to 4 36 0 08 millimolal at 50 mol nacl best fit equations for the solubilities of the two phases are m cepo 4 3 56 10 5 5 82 10 3 x nacl 1 97 10 2 x 2 nacl and m ypo 4 2 48 10 4 1 26 10 2 x nacl 8 89 10 3 x 2 nacl the solubility of ypo 4 is greater than that of cepo 4 at nacl mole fractions x nacl of 0 00 0 27 the solubility enhancement behavior implies that ce dissolves as anhydrous chloride complexes whereas y forms mixed cl oh solutes the results provide a simple mechanism for redistributing ree and y in deep crustal and upper mantle environments the h 2 o ce ratio inferred for subduction zone melts and silicate rich fluids can also be produced by a cepo 4 saturated fluid with x nacl 0 1 in addition neutral ph h 2 o nacl fluids can transport substantial ree and y obviating the need to invoke highly acid solutions in environments where they are unlikely

timing of diagenesis and very low grade metamorphism in the eastern sector of the sierra de cameros iberian range spain a u pb shrimp study on monazite the sierra de cameros is an intracontinental orogen and represents the north western part of the iberian range in northern spain it comprises a thick sequence of syn rift continental sediments mainly sandstones and carbonates deposited during lower cretaceous times a unique characteristic of the sierra de cameros in relation to the rest of the iberian range is the presence of low grade metamorphism in certain parts of the basin an event that predates basin inversion this paper describes the presence textural relationships and geochemical aspects of authigenic and or metamorphic monazite within different lithologies from the deepest parts of the basin sensitive high resolution ion microprobe shrimp u pb dating of monazite records the presence of two age populations the first with 206 pb 238 u ages ranging from 122 to 116 ma which is considered as diagenetic in origin whilst the second is dated at 99 2 ma and postdates the metamorphic climax

weathering behaviour and construction suitability of dimension stones from the drei gleichen area thuringia germany the construction suitability of a dimension stone depends on its weathering properties along with the petrology and the petrophysical properties the aim of this study was to evaluate the suitability of the dimension stones from the drei gleichen area for construction and replacement purposes in total six sandstones ingersleben wachsenburg hindfelden seeberg rohnberg gleichenberg upper triassic as well as two carbonates wachsenburg sinter quaternary wandersleben dolomite middle triassic were analysed the results from our laboratory and on site studies of the dimension stones show that rocks from the same stratigraphic layer like the sandstones from the upper triassic can show major differences in their petrophysical and weathering properties these differences are attributed to their different diagenesis resulting e g in varying pore space water balance and strength properties the pore size distribution can be divided into four different groups based on their occurring maxima and micropore content the determined water balance properties as well as moisture expansion and salt attack depend on these groups next to this the mineralogical composition significantly influences the weathering resistance sandstones with a high content of altered lithoclasts show a high amount of moisture expansion low strength and in consequence a low weathering resistance against salt attack based on the results of the present study an evaluation of construction suitability could be accomplished from the analysed sandstones only the seebergen sandstone is suitable for construction purposes due to its good availability good strength properties high compressive and tensile strength low softening degree as well as a low porosity furthermore the wachsenburg sandstone also shows good petrophysical and petrological properties but exploitable deposits are too sparse to be of commercial interest from the carbonates the wachsenburg sinter shows very suitable rock parameters but only sparse outcrops occur which are not appropriate for mining

slow cooling and crystallization of the roots of the neoproterozoic aracuai hot orogen se brazil implications for rheology strain distribution and deformation analysis the aracuai ribeira belt formed during the amalgamation of west gondwana in the late neoproterozoic its evolution included a main tectonometamorphic peak at 600 580 ma and a minor peak associated with the final collision with the western congo at 540 530 ma this belt has the characteristics of a hot orogen including a high thermal gradient 30 c km pervasive partial melting of the middle crust emplacement of large volumes of magmas resulting from partial melting of the lower crust and underlying mantle and slow cooling after the peak temperature we report 21 new amphibole biotite and muscovite 40ar 39ar ages that complement previously published data these data suggest slow cooling 3 5 c myr over several tens of million years after the peak temperature 800 c at 600 ma followed by faster cooling 10 c myr after the final amalgamation of west gondwana we estimate that 30 myr was required to heat the middle crust to the peak temperature and that anatectic and plutonic bodies remained in the magmatic state for 40 myr this protracted thermal evolution likely had major effects on the rheology of the middle crust and on the tectonic evolution of this orogen for example the correlation of u pb zircon crystallization ages and 40ar 39ar biotite cooling ages in the anatectic core of the orogen denotes a diachronic thermal evolution likely related to 3d deformation involving successive upwelling of anatectic components within a thrust unit crosscutting the pre existing fabric channel flow like this study also highlights that classical structural analysis techniques relying on changes in pressure or temperature conditions to identify the succession of deformation phases are not efficient at deciphering the tectonic evolution of hot slowly cooling orogenic belts where the temperature varies slowly over tens of million years allowing diachronic episodes of deformation to occur under nearly similar pressure and temperature conditions

thermochemistry of monazite la and dissakisite la implications for monazite and allanite stability in metapelites thermochemical properties have been either measured or estimated for synthetic monazite lapo4 and dissakisite calamgal2 sio4 3oh the mg equivalent of allanite a dissakisite formation enthalpy of 6 976 5 10 0 kj mol 1 was derived from high temperature drop solution measurements in lead borate at 975 k a third law entropy value of 104 9 1 6 j mol 1 k 1 was retrieved from low temperature heat capacity c p measured on synthetic lapo4 with an adiabatic calorimeter in the 30 300 k range the c p values of lanthanum phases were measured in the 143 723 k range by differential scanning calorimetry in this study la oh 3 appeared as suitable for drop solution in lead borate and represents an attractive alternative to la2o3 pseudo sections were calculated with the theriak domino software using the thermochemical data retrieved here for a simplified metapelitic composition la ree y and considering monazite and fe free epidotes along the dissakisite clinozoisite join as the only ree bearing minerals calculation shows a stability window for dissakisite clinozoisite epidotes t between 250 and 550 c and p between 1 and 16 kbar included in a wide monazite field the p t extension of this stability window depends on the bulk rock ca content assuming that synthetic lapo4 and dissakisite la are good analogues of natural monazite and allanite these results are consistent with the ree mineralogy sequence observed in metapelites where 1 monazite is found to be stable below 250 c 2 around 250 450 c depending on the pressure allanite forms at the expense of monazite and 3 towards amphibolite conditions monazite reappears at the expense of allanite

relating orogen width to shortening erosion and exhumation during alpine collision we investigate along strike width changes of the thickened accreted lower plate talp in the central and in the eastern alps we set the width of the talp in relation to the inferred amount of collisional shortening and exhumation along six orogen scale cross sections taking the present day along strike gradients in the amount of collisional shortening to represent the temporal evolution of the collisional wedge it may be concluded that the cross sectional area of the talp diminishes during ongoing shortening indicating that the erosional flux outpaced the accretionary flux higher amounts of collisional shortening systematically coincide with smaller widths of the talp and dramatic increases of the reconstructed eroded rock column higher amounts of shortening also coincide with larger amplitudes of orogen scale upright folds with higher exhumation and with higher exhumation rates hence erosion did play a major role in reducing by 30 km the vertical crustal thickness in order to accommodate and allow shortening by folding long term climate differences cannot explain alternating changes of width by a factor of almost 2 along straight segments of the orogen on length scales less than 200 km as observed from the western central alps to the easternmost eastern alps sedimentary or paleontological evidences supporting such paleo climatic differences are lacking suggesting that erosional processes did not directly control the width of the orogen

a decay function model for the integrity loss of rock when subjected to recurrent cycles of freezing thawing and heating cooling rocks are used in engineering works as monument or building stone and as architectural covering stone as a result they can be subjected to recurrent cycles of freezing and thawing and will be subjected to heating and cooling they loose some of their integrity under these cyclic temperature variations and the more frequent and severe these cycles the higher the integrity loss however the rates of progressive disintegration is not the same for different rock types or even within rock types this paper presents a mathematical model describing the integrity loss process when a rock is subjected to such recurrent cycles the model postulates a first order process and provides meaningful parameters for the integrity characteristic of rocks the validity of the model has been established by an experimental laboratory study carried out on 10 different rock types