advances in experimental investigation on hydraulic fracturing behavior of bentonite based materials used for hlw disposal bentonite based materials bbm in the form of blocks or rings have been commonly proposed as buffer materials for high level radioactive waste disposal in a real repository hydraulic fracturing is likely to be present when the ground water pressure exceeds to hydraulic resistance and the existence of technological gaps increases the risk of hydraulic fracturing based on the previous studies of hydraulic fracturing of bbm and technological interfaces the present work systematically analyzes the experimental achievements results show that the fracturing pressure of bbm and interfaces increases with hydration time initial dry density bentonite content and overburden pressure while it decreases with initial water content and gap thickness the temperature effect on hydraulic fracturing depends on the predominant cation of bentonite for na bentonite the higher temperature leads to the larger swelling pressure and thus the stronger hydraulic resistance tensile failure shear failure and synthesis failures are increasingly accepted for hydraulic fracturing mechanism the hydraulic fracturing of highly compacted bbm is mainly controlled by tensile failure while the initial shear failure can be found for bbm with a low enough density since hydraulic fracturing is expected to occur several times during the repository operation the long time monitoring of hydro mechanical behavior is of vital importance until the technological gaps are completely sealed furthermore the failure mechanism of hydraulic fracturing of bbm should be further researched as well as the sealing properties of interfaces under thermo hydro mechanically coupled conditions are proposed to be studied thoroughly

structural controls on sulfide mobilization at the high grade flying fox ni cu pge sulfide deposit forrestania greenstone belt western australia the flying fox komatiite hosted ni deposit is located in the forrestania greenstone belt of the yilgarn craton in western australia the host volcanosedimentary succession has been metamorphosed to amphibolite facies and deformation has sheared and dismembered the orebody creating 11 distinct ore shoots the ore shoots are hosted at the base of a komatiite sequence structurally overlying deformed metasedimentary rocks the ni sulfide orebody has undergone six phases of deformation 1 d 1areg e w compression resulted in tilting of the stratigraphy 2 d 1bff continued e w compression resulted in coaxial flattening along the footwall sedimentary rock sulfide komatiite contact and the basalt hanging wall sedimentary rock contact 3 d 2ff ene wsw compression resulted in noncoaxial shearing of the d 1bff structures 4 d 3ff ese wnw compression resulted in shallow angle thrusts 5 d 4ff during e w extension normal ductile brittle faults formed by the pooling and dilation of granitic magma along the f 2 structural contact between the footwall sedimentary and komatiite rocks and 6 d 5ff intrusion of a proterozoic dolerite dike during n s extension accompanied by late stage brittle normal faulting during deformation the ni sulfides reverted to monosulfide solid solution mss and were mechanically relocated along the footwall sedimentary rock komatiite contact offset into the footwall sedimentary rocks and entrained in the granitic magma creating atypical granite hosted sulfides the ni sulfides were mobilized up to 5 m away from the ultramafic rocks during the d 1 and d 2 events however subsequent dismemberment of the original orebody into separate ore shoots along flat lying faults during the d 3 event led to offsets of up to 300 m the detailed structural analysis of the flying fox deposit has shown that restoration of the lithostratigraphy along known faults can be used to define the volcanic stratigraphy including primary ni ore horizons this information can be used as a guide to the location of concealed extensions to known ore shoots or completely unknown orebodies at depth or along strike

volcanology of arnus vallis mars abstract arnus vallis av is a 300 km long sinuous rille located on the northeastern flank of the syrtis major volcano on mars observational evidence presented here suggests that av formed as an open lava channel that was at least partly incised into the pre existing terrain the lava source area consists of a sub circular pit at the southwestern end of a 7 km long straight section of channel av trends down slope from this source with an average bottom slope of 0 26 or 0 14 width varies from 1 km at the source to 0 6 km near the distal end with a mean of 0 76 km depth decreases from 180 m at the source to 25 m near the distal end the av terminus is obscured by a large impact crater we suggest that the material that flowed in av must have been a relatively high temperature low viscosity lava dynamically and perhaps compositionally similar to terrestrial komatiite or some lunar basalt lavas if correct this finding has implications for the mode of construction of syrtis major

simulation of groundwater exchange between an unconfined aquifer and a discrete fracture network with laminar and turbulent flows abstract in this study a new approach is developed to simulate groundwater flow through both an overlying unconfined aquifer and an underlying discrete fracture network the groundwater exchange between the aquifer and the fracture network including magnitude and direction is explicitly simulated based on the mass conservation which depends on a variety of parameters related to flow and network characteristics in the overlying unconfined aquifer we approximate the flow using the dupuit assumptions in the underlying fracture network we use the cubic law and forchheimer s law to iteratively simulate laminar or turbulent flow in individual fractures depending on the reynolds number explicitly separating laminar and turbulent flows in the fractures results in a system of nonlinear equations which is iteratively solved while the flow from the overlying unconfined aquifer is a small portion of the overall flow in the underlying fracture network incorrect use of the laminar or turbulent flow equation in the fractures can lead to significant errors in simulating the flow exchange as apertures increase both the portion of the total flowrate in the aquifer and the portion of the flow in the fractures coming from the aquifer decrease as the overall hydraulic gradient increases both the portion of the total flow in the aquifer and the portion of the fracture flow that comes from the aquifer increase the portion of the total flow in the aquifer increases with the aquifer thickness while the portion of fracture flow coming from the overlying aquifer decreases

hydrochemical disturbances measured in groundwater during the construction and operation of a large scale underground facility in deep crystalline rock in japan changes in the hydrochemical conditions of groundwater were evaluated following the construction of a large scale underground facility at the mizunami underground research laboratory miu japan the facility was constructed to a depth of 500 m in sedimentary and granitic rocks drawdown of the groundwater level in the range of several tens to hundreds of meters was observed up to hundreds of meters away from the shafts during the first ten years of facility construction and operation subsequent changes in groundwater chemistry occurred due to upconing of high salinity groundwater from the deepest part of the shaft and the infiltration of low salinity shallow groundwater we predict that future deep groundwater chemistry in the vicinity of the miu facility will resemble that of the present day shallow groundwater multivariate statistical analysis provides fundamental insights into such a site we found that the extent of hydrochemical variability related to miu construction and operation was dependent on the distance from the facility shafts and galleries and on hydrogeological compartmentalization resulting from lithological boundaries such as permeable conglomerates vs more compact lithological units and other features such as faults or clay layers we conclude that hydrochemical impact assessment of groundwater in low permeability rock is essential prior to the construction of such a facility this should include characterization of hydrogeological structures and compartments to propose suitable location of shafts and galleries

continuum discontinuum analysis of failure mechanisms around unsupported circular excavations in anisotropic clay shales abstract the stability of circular excavations in clay shales is a key issue in the drilling and tunnelling industries as well as in the field of deep geological waste storage a large body of experimental evidence indicates that the damaged zone around these cavities is influenced by strong mechanical anisotropy induced by the layered material structure the vast majority of numerical models adopted to date to analyse the stability of openings in layered rocks have been based on continuum mechanics principles using classic shear failure theory for elasto plastic materials however a number of experimental observations demonstrate that clay shales may fail in a brittle manner under low confinement conditions such as those characterizing the near field of the excavation therefore an alternative numerical approach based on non linear fracture mechanics principles and the discrete element method is adopted to gain new insight into the failure process of this class of geomaterials in order to account for the influence of clay shale microstructure on its mechanical behaviour a newly developed approach to capture the anisotropy of strength is proposed with this numerical approach the cohesive strength parameters of the fracture model are assumed to be a function of the relative orientation between the element bonds and the layering orientation the effectiveness of the numerical technique is quantitatively demonstrated by simulating standard rock mechanics tests on an indurated claystone namely opalinus clay emergent strength and deformation properties together with the simulated fracture mechanisms are shown to be in good agreement with experimental observations the modelling technique is then applied to the simulation of the excavation damaged zone edz around a circular tunnel in horizontally bedded opalinus clay the simulated fracturing process is mainly discussed in the context of the damage mechanisms observed at the mont terri url furthermore the influence of in situ stress on resulting edz geometry is analysed together with possible implications for ground support and tunnel constructability modelling results highlight the importance of shear strength mobilization along bedding planes in controlling the edz formation process in particular slippage of bedding planes is shown to cause rock mass deconfinement which in turn promotes brittle failure processes in the form of spalling the numerical technique is currently limited to two dimensional analyses without any thermo hydro mechanical coupling

petrology and stratigraphy of some texturally well preserved thin komatiites from kambalda western australia archaean komatiite volcanics at kambalda western australia have been metamorphosed to upper greenschist lower amphibolite grade and have experienced intense though heterogeneously developed polyphase deformation despite this preservation of igneous textural features is often good particularly in areas which underwent only static style metamorphism thin lavas from the tripod hill member of the kambalda komatiite formation over the western margin of the hunt nickel shoot display textural elements and facies variations which are virtually identical to those found in fresher thin komatiite sequences in other archaean greenstone belts four principal flow profile facies types are defined comprising nine subtypes these represent stages in a facies continuum ranging from mature profiles which comprise thick spinifex textured tops and close packed cumulate bases through to massive jointed immature profiles devoid of mesoscopic spinifex texture the causes of textural diversity within and between profiles are many and complex however facies variations can be attributed mainly to the effects of lava velocity at the time of major heat loss combined with relative lateral position within any flow the most mature textural and geochemical profiles developed in parts of lavas which had become ponded prior to major heat loss whereas the least evolved profiles developed along the lateral margins levees of moving lavas the study area komatiites occur as alternating stacks of flows of similar type this stratigraphy records temporal and spatial shifts in the locus of lava ponding over the western margin of the hunt nickel shoot such shifts may have been caused by irregularities in the underlying volcanic topography and or by synvolcanic faulting and subsidence

gas and water flow in an excavation induced fracture network around an underground drift a case study for a radioactive waste repository in clay rock summary the excavation damaged zone edz surrounding a drift and in particular its evolution is being studied for the performance assessment of a radioactive waste underground repository a specific experiment called cdz was designed and implemented in the meuse haute marne underground research laboratory url in france to investigate the edz this experiment is dedicated to study the evolution of the edz hydrogeological properties conductivity and specific storage of the callovo oxfordian claystone under mechanical compression and artificial hydration firstly a loading cycle applied on a drift wall was performed to simulate the compression effect from bentonite swelling in a repository drift bentonite is a clay material to be used to seal drifts and shafts for repository closure purpose gas tests permeability tests with nitrogen and tracer tests with helium were conducted during the first phase of the experiment the results showed that the fracture network within the edz was initially interconnected and opened for gas flow particularly along the drift and then progressively closed with the increasing mechanical stress applied on the drift wall moreover the evolution of the edz after unloading indicated a self sealing process secondly the remaining fracture network was resaturated to demonstrate the ability to self seal of the cox claystone without mechanical loading by conducting from 11 to 15 repetitive hydraulic tests with monitoring of the hydraulic parameters during this hydration process the edz effective transmissivity dropped due to the swelling of the clay materials near the fracture network the hydraulic conductivity evolution was relatively fast during the first few days low conductivities ranging at 10 10 m s were observed after four months conversely the specific storage showed an erratic evolution during the first phase of hydration up to 60 days some uncertainty remains on this parameter due to volumetric strain during the sealing of the fractures the hydration was stopped after one year and cross hole hydraulic tests were performed to determine more accurately the specific storage as well as the hydraulic conductivity at a meter scale all hydraulic conductivity values measured at the injection interval and at the observation intervals were all below 10 10 m s moreover the preferential inter connectivity along the drift disappeared specific storage values at the observation and injection intervals were similar furthermore they were in agreement with the value obtained at the injection interval within the second hydration phase 60 days after starting hydration the graphical abstract synthesizes the evolution of the hydraulic gas conductivity for 8 intervals since the beginning of the cdz experiment the conductivity limit of 10 10 m s corresponds to the lower bound hydraulic definition of the edz and it is demonstrated that edz can be sealed this is a significant result in the demonstration of the long term safety of a repository

localization and characterization of cracks in clay rocks using frequency and time domain induced polarization induced polarization ip is a geophysical method that is potentially sensitive to the presence of cracks in porous rocks and therefore to damage we performed time domain and frequency domain ip measurements at the tournemire underground research laboratory url aveyron france in areas where different types of cracks are observed these cracks correspond to both tectonic fractures and new cracks associated with stress release and desiccation resulting from the excavation of a gallery these measurements were performed both in eastern and northern galleries of the test site the eastern gallery was excavated in 1996 while the northern gallery was excavated recently in 2008 this gives us the opportunity to study the electrical characteristics of the excavation damaged zone surrounding the galleries with respect to the age of the excavation longitudinal profiles were performed along the floor of the galleries with 48 cu cuso4 electrodes separated by a distance of 20 cm chargeability and resistivity were inverted using a gauss newton iterative approach assuming an isotropic heterogeneous clay rock material the resulting ip tomograms show a correlation between high values of chargeability and the presence of calcite filled tectonic fractures x ray analysis indicates that the presence of pyrite in these fractures is a potential source of the observed ip signals the cracks associated with the mechanical damage of the formation exhibit low values of chargeability on the same order of magnitude than the chargeability of the clay rock matrix and are therefore hardly observable a smaller ip response associated with the presence of these cracks is observed in the older gallery and this observation is qualitatively related to the desaturation process associated with these cracks in a specific area of one of the galleries the presence of calcareous nodules is observed to be an important source of anomalous chargeability this signature seems to be associated with the presence of pyrite

faults and fractures in the gallery 04 of the mont terri rock laboratory characterization simulation and application this paper deals with the reconstruction of a fracture network observed in an underground gallery of a tunnel buried in clay stones in switzerland below mont terri the trace maps of the gallery 04 and of the ez g niche of this site have first been digitized and used in various ways to characterize the data the traces have been divided into two groups i e the pre existing faults in the gallery and the fractures of the excavated damaged zone edz in the niche each group has been analyzed individually the number of data for the faults has turned out to be statistically significant while it was very limited for the edz fractures for both cases the major statistical characteristics of the traces have been extracted and a reconstruction procedure developed and tested a full example has been worked out a gallery immersed in a reconstructed fractured porous medium has been meshed and the electrical field created by a dipole at the wall calculated by solving the three dimensional laplace equations in the fractures and in the porous medium

a comparative study of olivine and clinopyroxene spinifex flows from alexo abitibi greenstone belt ontario canada a petrological and geochemical study of an olivine and of a clinipyroxene spinifex textured flow from alexo indicates that the initial liquid in both flows probably came from the same mantle melting event and that the source was incompatible element depleted the starting liquid of the clinopyroxene flow had experienced more olivine fractionation 10 prior to its emplacement at alexo than the initial liquid of the olivine spinifex flow

precambrian tectonic evolution of part of gondwana southwestern australia southwestern australia has a long dynamic precambrian history of crustal fragmentation and aggregation by continental collision and accretion this interpretation contrasts with the widely held belief that most of australia was part of a proterozoic supercontinent in which all tectonic magmatic and metamorphic activity was intracontinental the pilbara and yilgarn cratons are two quite different fragments of archean continental crust that collided to form the capricorn orogen between 2000 and 1600 ma the albany fraser orogen formed along the southern margin of the yilgarn craton during another major continental collision at 1300 to 1100 ma rifting removed the northeastern part of these combined cratons and orogens between 1100 and 700 ma subsequent continental collision along this rifted margin formed the paterson orogen at 700 to 600 ma therefore the assembly of this considerable part of gondwana may not have been completed until about 600 ma

the association between ni cu pge sulfide and ni co lateritic ores and volcanic facies within the komatiites of the 2 7 ga east yilgarn craton large igneous province western australia abstract a critical factor in the generation of komatiite hosted ni cu pge sulfide deposits the addition of external sulfur via assimilation of s bearing substrate beneath channelised lava flows is a function of the komatiite flow field architecture this architecture is also critical in the development of magnesium rich bedrock lithologies that are prerequisites for the formation of komatiite hosted ni co laterite deposits to better understand the controls on the spatial distribution of both these deposit types a gis referenced map of komatiite flow regimes within the komatiitic component of the c 2 7 ga east yilgarn large igneous province and from parts of adjacent older greenstone belts in the yilgarn craton has been constructed using data from the field and the literature the regimes essentially divide komatiite sequences into those composed of thin 0 5 100 m laterally restricted 50 m 3 km cooling units and those composed dominantly of thick 100 m 1 km and laterally extensive 3 100 km cooling units the regimes are subdivided into six facies and five sub facies based on both stratigraphic and lateral variations in lithologies the facies define regional scale variations reflecting markedly different spatial and temporal crystallisation conditions within komatiite flow fields there is a marked spatial association between known magmatic nickel sulfides and particular komatiite facies facies favourable for hosting magmatic sulfides are those that contain early formed very magnesian cumulate sequences requiring high effusion rates of very hot turbulently flowing lava to form and thus have the potential to be contaminated by s bearing substrate rocks sulfide mineralised komatiites make up about 9 of the area of the current outcrop of the 2705 ma komatiite lip facies that have a low potential for nickel sulfide mineralisation are sheet like bodies in which basal rocks were emplaced under relatively quiescent conditions and where hot turbulently flowing lava and crystallisation of olivine rich cumulates developed only after the build up of a pile of high porosity olivine cumulates allowing no interaction with the substrate nickel cobalt laterite deposits are associated with thick originally laterally extensive high magnesian sequences some such sequences are also favourable for magmatic sulfide mineralisation but others occur in sheet like sequences

the nickel sulfide mineralization and metamorphic setting of the forrestania area western australia the forrestania group of nickel sulfide occurrences of the archean southern cross province is localized in intrusive dunite bodies at the base of a lower komatiite unit which is interlayered with tholeiitic mafic rocks para amphibolites quartz biotite schists chemical sedimentary rocks iron formation and sulfide cherts and komatiites concordant lenticular metamor phosed sill like mineralized dunites have komatiitic affinities and appear to be feeder chambers to overlying thick sequences of dominantly extrusive ultramafic komatiites and rare pyroclastic komatiites unmineralized portions of the dunites are extremely rich in magnesium with mgo values ranging between 45 and 51 percent the important nickel sulfide occurrences are pentlandite rich disseminations distributed in the basal portions of metamorphosed intrusive dunites e g cosmic boy and digger rocks south digger rocks similar mineralization also occurs in hanging wall and internal portions of dunites but is generally of less importance than the basal mineralization because of lower nickel tenor massive pyrrhotite rich sulfides occur within reaction zones between dunite and footwall country rocks and as remobilized veins and stringers in footwall metasediments this type of mineralization forms important small tonnage high grade deposits at new morning and flying fox supergene alteration of primary sulfides is extensive and massive violarite pyrite magnetite zones are developed in weathering profiles polyphase deformation and metamorphism with peak conditions estimated at 655 degrees or 30 degrees c and 4 0 or 1 0 kb resulted in widespread recrystallization and tectonic remobilization of ductile sulfides cumulate dunites were metamorphosed to bladed granular and granoblastic aggregates of forsterite talc forsterite talc anthophyllite and forsterite talc enstatite formed under varying f sub co 2 and f sub h 2 o conditions retrograde serpentinization and talc carbonate alteration followed by later supergene alteration has caused textural modification and oxidation of primary sulfides with development of pyrite violarite and magnetite rich ores nickel values and ni cu ratios vary for different types of mineralization the economically important basal disseminations of pentlandite pyrite pyrrhotite chalcopyrite have ni values in the range 2 to 5 percent and constant ni cu ratios in the range 14 1 to 22 1 bulk composition of primary sulfides of this type at cosmic boy is s rich with fe 39 4 percent ni co 18 6 percent and s 42 0 percent massive remobilized veins of pyrrhotite pentlandite pyrite chalcopyrite have high ni 3 to 8 and erratic ni cu ratios generally in the range from 10 1 to 200 1 with a mean of 45 1 this mineralization is fe rich with fe 50 4 percent ni co 7 4 percent and s 42 2 percent broad irregular sparse disseminations less than 2 of pentlandite heazlewood chalcopyrite form in the internal portions of cumulate and metamorphosed dunites they have low ni 0 3 to 0 5 high ni cu ratio 50 1 to 100 1 and bulk composition close to pentlandite composition with fe 31 8 percent ni co 34 2 percent and s 34 0 percent the bulk compositions of sulfides generally plot on the s rich side of the monosulfide solid solution field at 650 degrees c and this appears to reflect nickel and sulfur mobility during retrograde metamorphism

winter monsoon convection in the vicinity of north borneo part i structure and time variation of the clouds and precipitation abstract radar and satellite observations in the vicinity of northern borneo obtained during the international winter monsoon experiment wmonex showed that the convection in that region underwent an extremely regular diurnal cycle over the sea to the north of borneo the general level of convective activity was increased during monsoon surges and during the passages of westward propagating near equatorial disturbances convective activity was decreased during monsoon lulls the diurnal cycle was well defined regardless of whether the general level of convective activity was enhanced or suppressed by synoptic scale events the cycle of convection over the sea was especially well documented it was typically initiated at about midnight when an offshore low level wind began where this wind met the monsoonal northeasterly flow usually just off the coast convective cells formed after midnight the convection continued to develop and by 0800 lst it had evolved into an organized mesoscale system with a

introduction to nickel sulfide orebodies and komatiites of the black swan area yilgarn craton western australia the black swan district 70 km north east of kalgoorlie in the archaean yilgarn craton of western australia hosts massive and disseminated nickel sulfide orebodies associated with komatiites the host rocks and ores preserve some remarkable primary igneous features which provide important clues as to the origin of komatiite hosted nickel ores the series of papers that follow report an extremely detailed study of the petrology volcanology and geochemistry of these unusually well preserved orebodies and their host rocks

chromite in komatiites 3d morphologies with implications for crystallization mechanisms high resolution x ray computed tomography has been carried out on a suite of komatiite samples representing a range of volcanic facies chromite contents and degrees of alteration and metamorphism to reveal the wide range of sizes shapes and degrees of clustering that chromite grains display as a function of cooling history dendrites are spectacularly skeletal chromite grains formed during very rapid crystallization of supercooled melt in spinifex zones close to flow tops at slower cooling rates in the interiors of thick flows chromite forms predominantly euhedral grains large clusters up to a dozen of grains are characteristic of liquidus chromite whereas fine dustings of mostly individual 20 m grains form by in situ crystallization from trapped intercumulus liquid chromite in coarse grained olivine cumulates from komatiitic dunite bodies occurs in two forms as clusters or chains of euhedral crystals developing into chicken wire texture where chromite is present in supra cotectic proportions and as strongly dendritic semi poikilitic grains these dendritic grains are likely to have formed by rapid crescumulate growth from magma that was close to its liquidus temperature but supersaturated with chromite in some cases this process seems to have been favoured by nucleation of chromite on the margins of sulphide liquid blebs this texture is a good evidence for the predominantly cumulus origin of oikocrysts and in situ origin of heteradcumulate textures our 3d textural analysis confirms that the morphology of chromite crystals is a distinctive indicator of crystallization environment even in highly altered rocks

thermomechanical erosion of ore hosting embayments beneath komatiite lava channels textural evidence from kambalda western australia abstract archean komatiite hosted nickel deposits at kambalda western australia are located in embayments within channelized lava flows the origin of these embayments is controversial the currently favoured model invokes pre existing topographic features filled in by the komatiite and sulfide melt and subsequently modified by thermomechanical erosion new evidence from sulfide deposits on the eastern limb of the kambalda dome includes well preserved magmatic textural relationships of the sulfides with the surrounding rocks suggesting the entire embayment was formed by thermomechanical erosion these textures are particularly well preserved within the moran deposit of the long victor complex which lacks the younger intense structural deformation that other kambalda deposits have undergone the vestiges of an older broad concave embayment are represented by sediment sulfide textures present on the flanks up to 150 m away from the younger steep sided embayment sediment sulfide contacts are marked here by a globular silicate sulfide intergrowth interpreted as emulsion and cumulate like mono sulfide solid solution mss grains surrounded by interstitial silicate melt textures preserved from the formation of a steep sided embayment are frozen into the basalt sulfide contact and include an undulating contact with sulfide filled microfractures and a ferrichromite layer basalt sulfide breccia and interpreted crystallized silicate sulfide liquid emulsions and basalt plumes rising into the sulfides textures from the last step of embayment formation are found in the pinchouts i e where the massive sulfide ore is bounded top and bottom by basalt they include the same textures that were formed during the excavation of the steep sided embayment but they also feature interpreted basalt sulfide emulsions on the upper contact cm scale silicate sulfide ferrichromite layering on the upper contact and a vesicular basalt scum layer floating on the sulfides beneath the solid older basalt all these textures represent frozen examples of different stages during the excavation and formation of the embayment and reflect physical processes responsible for thermomechanical erosion the initial disposition and orientation of ore hosting channels was controlled by paleo topography probably defined by syn volcanic faults but the textures we describe show that within the channel the geometry of the entire embayment was the product of erosion the sulfide melt itself played a major role in the process owing to its high density high heat content and very low viscosity but the hydrated nature of the underlying altered basalt was also critical fluids were released from the basalt due to the high temperature in the 1 2 cm immediately beneath the sulfide melt with instant flash boiling creating a network of microfractures pre existing fracture networks and breccia in the basalt allowed the sulfide melt to locally infiltrate the substrate to a greater depth increasing the hydraulic head at the tip of the fracture thus accelerating the erosion process once a critical sulfide melt thickness is reached partly aided by a growing pile of matrix net textured sulfides the pressure difference on the embayment floor compared to the basalt at the bottom edges of the embayment becomes high enough to allow the liquid sulfides to melt sideways to form a pinchout

analytical numerical modeling of komatiite lava emplacement and thermal erosion at perseverance western australia abstract we have applied a thermal fluid dynamic geochemical model to investigate the emplacement and erosional potential of archean komatiite flows at perseverance western australia perseverance has been proposed as a site of large scale thermal erosion by large volume komatiite eruption s resulting in a 100 150 m deep lava channel containing one of the world s largest komatiite hosted fe ni cu pge sulfide deposits using constraints based on field theoretical and geochemical data we have modeled the emplacement of a range of flow thicknesses over felsic tuffaceous substrates with various degrees of consolidation and water contents thermo mechanical erosion becomes more effective for substrates that are increasingly unconsolidated and water rich for thermo mechanical erosion to be responsible for the formation of the 100 m deep concave perseverance embayment and the highly contaminated 10 20 perseverance komatiites the most likely scenarios require emplacement of thick e g 10 30 m turbulent channelized liquidus or superheated komatiite lavas over a welded or unconsolidated submarine tuff flow distances must have been long tens to hundreds of kilometers and flow volumes must have been very high hundreds to thousands of km 3 lava channels and tubes 110 km long have not been observed on earth but are consistent with those formed by low viscosity lavas on venus the moon mars and io flow volumes are consistent with those in continental flood basalt eruptions and oceanic plateau large igneous provinces and may represent the initial outpourings of komatiite lavas from archean mantle plume activity

the perseverance ultramafic complex western australia the product of a komatiite lava river the perseverance ultramafic complex is a body of olivine rich komatiitic rocks spatially associated with the agnew nickel deposit in the agnew wiluna greenstone belt of the archaean yilgarn block in western australia the complex consists of a central lenticular body up to 700 m thick of olivine adcumulates flanked by laterally extensive sheet like bodies of olivine orthocumulates and spinifextextured komatiite flows rocks progressively further away from the central lens have chemical compositions reflecting higher original proportions of komatiite liquid to cumulus olivine parent liquids had mgo contents between 25 and 32 mgo approximately chondritic al ti ratios and hree patterns and moderate depletion in lree olivines within the adcumulate lens show a progressive increase in forsterite content from fo93 at the bottom to fo94 5 at the top calculated original olivine compositions in ihe flanking rocks are similar to those at the base of the central lens original olivine nickel contents show a symmetrical variation from maximum values of 3500 ppm at the top of the central lens through minimum values of 1000 ppm at the base and margins of the central lens to intermediate values in the distal rocks the complex as a whole shows evidence for nickel depletion relative to other komatiite suites these observations are explained in terms of prolonged eruption and flow of komatiitic lava down a major flow channel or lava river adcumulates crystallized on the floor and sides of the central channel which was formed at an early stage by thermal erosion of floor rocks episodic overflow of the central channel produced distal flood plain rocks consisting of olivine orthocumulates and layered flows lavas became more magnesian and nickel rich with time giving rise to the observed spatial variation in primary olivine composition nickel depletion of the earliest lavas is attributed to pre eruption segregation of large volumes of immiscible fe ni sulfide which were concentrated to form the underlying agnew nickel deposit

relation between hydrogeological setting and swelling potential of clay sulfate rocks in tunneling abstract in this study an approach to estimate the swelling potential of clay sulfate rocks in tunneling is presented swelling of clay sulfate rocks leads to damage in tunnels that is difficult and costly to repair swelling is caused by the transformation of the sulfate mineral anhydrite into gypsum which involves an increase in rock volume in a system open to water flow knowledge of the hydrogeological situation and the groundwater flow systems at the tunnel is essential to better understand the swelling processes the present study was conducted for the chienberg tunnel in switzerland it investigates the hydrogeological situation of four zones in this tunnel crossing the triassic gipskeuper formation in two of them heavy swelling occurred after tunnel excavation while in the other two no swelling occurred in addition the groundwater flow systems before and after tunnel excavation are investigated based on numerical flow modeling the findings suggest that in certain situations after tunnel excavation depending on geological and changing hydraulic conditions the excavation damaged zone around the tunnel provides a hydraulic short circuit between the weathered gipskeuper and the anhydrite bearing strata of the unweathered gipskeuper as a result water from the weathered gipskeuper gets in contact with anhydrite triggering its transformation into gypsum and thus rock swelling the results of the study may also contribute to improved swelling experiments in the laboratory and a more reliable planning of restoration measures in tunnels that are damaged by rock swelling

a 3 d geological and structural synthesis of the leinster area of the agnew wiluna belt yilgarn craton western australia with special reference to the volcanological setting of komatiite associated nickel sulfide deposits the leinster area is situated toward the southern end of the agnew wiluna belt in the yilgarn craton of western australia and hosts the giant perseverance komatiite associated nickel sulfide deposit at in excess of 1 2 mt contained ni this is the biggest type 1 basal sulfide rich accumulation deposit in the world and it is associated with a number of smaller deposits that extend over a strike length of 20 km adjacent to the perseverance fault on the eastern margin of the belt in broad terms the greenstone sequence comprises an eastern rift proximal komatiite dacite sequence and a western and more marginal basalt dominated sequence with minor komatiite the komatiites display a wide range of compositions and textures from highly magnesian olivine meso to adcumulate rocks composed of olivine with forsterite contents of up to 94 5 to sequences of thin spinifex textured komatiite flow units this compositional range indicates considerable variation in volcanic facies from rift proximal to distal loci of focused flow termed pathways indicated by thickened cord like bodies of more olivine rich rock occur at all scales and are intimately associated with the ni sulfide mineralization the pathways are linked by thinner sequences of lower mgo rocks either layered olivine orthocumulate rocks or sequences of thin spinifex textured flow units some of the lower mgo komatiite sequences appear to emanate from the tops of pathways in the manner of breakout flows in tube fed basaltic terrains variably sulfidic black shales and cherts and barren exhalative iron sulfide horizons are intimately interlayered with the komatiitic rocks the overprinting effects of regional deformation and metamorphism spanning at least 80 m y are considerable at least eight local deformation events have been recognized by previous workers these have been used to constrain the 3 d model and can be linked to craton wide structural schemes some of the major faults are clearly accretionary and reflect reactivation of underlying basin forming structures early north over south thrusting was followed by e w directed basin closure and the development of nnw trending open regional folds extension accompanied batholithic granitoid intrusion and reactivated rift parallel nnw trending faults producing the major strike slip fault systems that divide the greenstone succession into a series of structural and stratigraphic domains the ensuing orogenic collapse resulted in overturning of the stratigraphy to the east subsequent brittle deformation events have produced fault sets in a variety of orientations that can be related to ongoing shortening with a variable principal stress orientation there is a complex interplay of structural and volcanological controls on the formation and subsequent deformation of the ni sulfide deposits in this ancient terrane three dimensional modeling has furthered a detailed understanding of the geologic and structural evolution of the belt allowed the identification of komatiite pathway positions and their plunges and provided quantitative data on the magnitude and direction of fault offsets of different generations the modeling exercise has shown that it is possible to strip away the effects of overprinting metamorphism and deformation to reveal some of the primary controls on komatiite volcanism and the location of ni sulfide deposits even in those portions of greenstone belts that are highly deformed and have undergone amphibolite facies metamorphism this is illustrated with case studies of the perseverance venus rocky s reward harmony and sir lancelot deposits three dimensional modeling has the capacity to integrate geologic geochemical and geophysical datasets in a way that fully utilizes the results of past exploration programs and produces a premium geologic product that can be used to guide further exploration the recent discovery of the venus deposit is in part a tribute to the power of this approach

winter monsoon convection in the vicinity of north borneo part ii effects on large scale fields abstract an observational study of the thermodynamic and kinematic structure and properties of monsoon convective systems and their large scale environment over the southern south china sea during the field phase december 1978 of the winter monsoon experiment wmonex has been carried out the primary observations used are from three soviet research vessels positioned in a triangular array off the north coast of borneo during the period 6 28 december computations of thermodynamic fields divergence and vertical motion have been made for the duration of the field phase based on six hourly rawinsonde releases at the ship sites analysis of the data indicates that the degree of convective activity over the southern south china sea is modulated by long period synoptic forcing monsoon surges easterly waves and also significantly by diurnal forcing land sea breeze circulations a diurnal cycle of convection persists in the region whether the synoptic scale forcing is weak or strong convection over wate

mean state of the troposphere over south east asia and the east indies december 1978 the mean state of the troposphere over south east asia from 8 30 december 1978 is described in the lower troposphere a jet was observed over the south china sea extending south westward from the philippines evidence suggests that this north easterly jet was supported by downstream blocking induced by the borneo land mass at the equator the jet had the appearance of being channelled between the highlands of borneo and sumatra on its left flank near the west coast of borneo was a semi permanent and quasi stationary vortex being warm core this vortex was probably maintained in part by latent heat release in cumulus convection by partitioning the data into means at 00 and 12 gmt the intensity of the rising branch of the hadley circulation over borneo was shown to increase by a factor of two from 100 10 5 to 200 10 5mb s 1 from 00 to 12 gmt

mechanical properties of abandoned and closed roadways in the kushiro coal mine japan abstract the objective of this research is to clarify the mechanical properties and self healing ability of the excavation damaged zone edz around rock caverns in clastic rock observations of nearly one hundred closed roadways up to fifty years old which can be regarded as very severe edzs with no initial sealability and are up to 300 m deep in clastic rock were made at the kushiro coal mine japan to accomplish the objective most old roadways were closed though a few remain open closure of old roadways was mainly due to roof deflection and or floor heave large plastic deformations dominated however severe fractures were seldom observed in closed old roadways rayleigh wave velocity and hydraulic conductivity in the closed old roadways were in the range of 0 3 1 2 km s and 5 10 7 1 10 7 m s respectively and those in edz and edz excavation disturbed zone around recently excavated roadways were 1 1 1 8 km s and 1 10 8 5 10 8 m s respectively the extent of edz around the present tailgate was in the range of 1 5 m mechanical excavation and prevention from water are suggested as the key points for long term maintenance of rock repositories pressurization from inside the cavern to decrease the permeability of edz is proposed for maintenance of rock repositories in medium hard clastic rock masses at similar depths for long periods

darcy flux as hydrological indicator for the swelling potential of clay sulfate rocks in tunneling abstract swelling of clay sulfate rocks often poses a severe threat in tunneling it causes serious damage and produces high additional costs during tunnel construction and operation the swelling of clay sulfate rocks requires groundwater inflow into anhydrite bearing layers therefore the darcy flux into anhydrite bearing layers surrounding the tunnel is suggested as a hydrological indicator for the swelling potential a case study from switzerland is presented that uses numerical groundwater models to calculate the darcy flux at the anhydrite level in different tunnel sections after tunnel excavation the approach which assumes that a high darcy flux at the anhydrite level after excavation indicates a high swelling potential is tested at the study site the results suggest that the darcy flux can serve as a hydrological indicator for the swelling potential in tunneling equally important however is the fact that the darcy flux depends on many parameters all of which are uncertain hence a sensitivity study is conducted to analyze the influence of these parameters the sensitivity study shows that the significant parameters in the case study are the hydraulic conductivity of the aquifer above the tunnel the groundwater level in this aquifer as well as the hydraulic properties of the excavation damaged zone of the tunnel lining and of faults based on the results of the sensitivity study implications for site investigation and measures to counteract the swelling problem are discussed the major contributions of this paper are therefore the development of an approach to estimate the swelling potential of clay sulfate rocks based on a hydrological indicator and the derivation of the parameters that have the strongest impact on the swelling potential of such rock

erosion by flowing lava field evidence erosion of substrate materials by melting or mechanical means has been suggested in active lava flows on earth and other planets although there are many references to lava erosion on earth unambiguous evidence is rare geological relationships commonly cited as evidence of downcutting by lava can be explained without recourse to erosion in order to assess possible erosion by flowing lava we carried out field studies of tube fed basalt flows sheet flows of the columbia river basalt province crb and precambrian komatiites unequivocal evidence for thermal erosion melted dacite substrate was found at the cave basalt lava tube mount st helens for which fluid dynamic analysis indicates laminar flow although erosion was enhanced in areas of locally steep slopes possibly as a result of localized turbulence other lava tubes in our study display strong but inconclusive evidence for erosion komatiite flows display good evidence for erosion of their substrate possibly in a turbulent regime but assessment of the extent of erosion is hampered by limited and disrupted exposures no evidence for thermal erosion was found in the crb our findings suggest that an erosional origin for planetary sinuous rilles and canali would be favored by high reynolds number flows high mass flux low viscosity lava steep slopes and substrates having a lower melting temperature than the lava or low mechanical strength e g regolith

the physical volcanology of archaean komatiite sequences from forrestania southern cross province western australia abstract the archaean supracrustal sequence at forrestania contains at least five komatiitic belts which can be traced along strike for distances in excess of 30 km lithologies range from olivine cumulates which crystallised at the interface between substrate and flowing lava to spinifex textured rocks which underwent rapid crystallisation within ponded lava lobes characteristic associations of different rock types are interpreted in terms of variations in eruption rate which presumably reflect proximity to the vent or to a major lava river thick sequences of olivine adcumulate to mesocumulate crystallised in a dynamic environment where lava flow was continuous and eruptive velocities were high sheeted bodies of olivine cumulate formed from voluminous turbulent flow of lava over relatively refractory substrates such as basalt and oxide facies banded iron formation ribbon shaped olivine cumulate bodies formed in an equally dynamic environment within major lava channels where the substrate was less refractory and consisted of quartz rich sedimentary rocks which were susceptible to thermal erosion distributary lava channels in more distal settings are represented by thinner ribbon like accumulations of olivine mesocumulate to orthocumulate unusual poikilitic pyroxene bearing rocks are present at the base of some lava channels and appear to represent the crystallisation product of a komatiitic lava which has been contaminated by cherty sedimentary rocks pyroxene and plagioclase bearing cumulates are present at the top of other channel sequences and reflect late stage ponding and in situ differentiation of komatiitic lava within the channel the channel facies rocks are flanked by sequences comprising multiple thin spinifex textured flow units which formed from the episodic overflow of lava from the distributary channels similar rocks also occur stratigraphically above many of the thick olivine cumulate bodies and reflect episodic emplacement of thin cooling units during the waning stages of the eruptive cycle

in situ monitoring of tunnel deformation evolutions from auxiliary tunnel in deep mine abstract deformation caused by excavation is of great effects on tunnel stability and tunnel support design monitoring using instruments that are installed in place within the examined tunnel cannot record a large amount of surrounding rock deformation that usually takes place ahead and close to the tunnel face for this important reason the overall deformation process was observed using instruments installed prior to excavation from auxiliary tunnel in a 900 m deep coal mine tunnel two monitoring methods i e multipoint extensometers and wave velocity tomography were used at two monitoring sections with different rock lithology the results showed that a large amount of deformation at both monitoring sections had already been occurred when the excavation face passed the monitoring sections at a very small distance the size of the plastic zone at monitoring section 1 is identified as 1 8 m 0 36 d d denotes the diameter of the examined tunnel and the velocities within this zone decreased from 4 5 km s to 2 km s the primary deformation was generated in a distance from 0 8 d ahead the excavation face to 2 3 d behind the excavation face the induced deformation was also observed after the primary deformation period and some additional deformation was still occurred in the plastic zone although the size of plastic zone remains constant the displacements and p wave velocities at the two monitoring sections showed little differences

zoned orthopyroxenes in the ni co sulfide ore bearing xiarihamu mafic ultramafic intrusion in northern tibetan plateau china implications for multiple magma replenishments abstract the xiarihamu mafic ultramafic intrusion is situated in the east kunlun orogenic belt e kob northern tibetan plateau china with ni co sulfide mineralization mainly in orthopyroxenite and olivine orthopyroxenite whole rock and mineral compositions show cyclic variations in drill hole intersections through the xiarihamu mafic ultramafic intrusion microbeam x ray fluorescence xrf mapping shows reverse zoning cr poor core cr rich rim and oscillatory zoning cr poor core cr rich mantle and cr poor rim in orthopyroxene of olivine orthopyroxenite and orthopyroxenite zoned orthopyroxenes are euhedral or subhedral and there are relatively sharp interfaces between zones with distinct cr contents crystal size distribution csd curves of orthopyroxenes in olivine orthopyroxenite show concave upward curvature at size larger than 3 0 mm and larger orthopyroxenes commonly display zoning implying a secondary recrystallization and grain growth of larger orthopyroxenes quantitative analyses show that cr and enstatite contents of cores are relatively lower but incompatible element e g ti zr ga and sr contents of cores are higher than rims in reverse zoned orthopyroxenes and chemical profiles of unzoned orthopyroxenes resemble those of rims but different from those of cores in reverse zoned orthopyroxenes chemical profiles of orthopyroxenes indicate that cr zoning is not due to the change in cr partitioning behavior between orthopyroxene and silicate melt which shows significant temperature and redox dependence textural feature and crystal size distribution of orthopyroxenes suggest the formation of cr rich zones attests to the multi stage growth in the process of magma replenishment rather than a reactive liquid flow model or in situ trapped liquid overgrowth orthopyroxene zoning together with compositional variation and intrusive relationship between olivine orthopyroxenite and orthopyroxenite imply that the xiarihamu mafic ultramafic intrusion was formed by multiple magma replenishments with magma varying roughly from a more evolved to a more primitive composition

archean polyphase deformation in the lake johnston greenstone belt area implications for the understanding of ore systems of the yilgarn craton abstract a structural and geochronology study on the 2900 ma lake johnston greenstone belt ljgb has defined multiple deformation events quantitative u pb age constraints have been obtained on the ductile deformation and peak metamorphic assemblages the d 1lj event is associated with the development of fold nappes during interpreted nne ssw shortening u pb shrimp dating on monazite from a dyke folded by the d 1lj event gives an age of 2634 1 ma providing an upper age limit on d 1lj this age could have been reset by the d 2lj metamorphic event a major metamorphic thermal event post dates the d 1lj event and is inferred to be the result of elevated temperatures coeval with the emplacement of granitoid intrusions the d 2lj event is associated with peak metamorphic temperatures and reflects nne ssw to ne sw shortening associated with dextral shearing a dyke that intrudes and crosscuts d 2lj fabrics yield a u pb shrimp age on monazite at 2629 1 ma and provides a lower age limit on the d 2lj event d 3lj is defined by crenulation cleavages developed during e w shortening the d 4lj episode is defined by brittle deformation and a series of n to ne trending steep dipping dextral faults formed during craton scale shortening under a ne sw directed far field stress the brittle d 5lj event is characterized by e w shortening with dip slip reverse n s faults the new d 2lj deformation age is younger than previously constrained ages for major deformation in the 2900 ma greenstone belts deformation within the ljgb was broadly coeval with the waning stage of formation of gold deposits in adjacent greenstone belts most peak magmatic and metamorphic events preserved in the greenstone belts have been constrained to ca 2640 2650 ma the presence of such a high temperature deformation event recorded at ca 2630 ma in the ljgb belt has implications for the thermal history fluid formation and geodynamic context of the development of these gold systems the 2630 ma age correlates with late stage and post gold emplacement of pegmatite dykes in surrounding terranes the ljgb is interpreted to have been a mobile belt associated with high grade metamorphism that was inboard west of and active during the formation of major world class gold systems in the eastern goldfields terranes the d 1lj to d 2lj changes in the kinematics of the system i e d 1lj to d 2lj may correlate with a stress switch linked to the influxes of gold bearing fluids in adjacent greenstone belts

roles of xenomelts xenoliths xenocrysts xenovolatiles residues and skarns in the genesis transport and localization of magmatic fe ni cu pge sulfides and chromite abstract most sulfide rich magmatic ni cu pge deposits form in dynamic magmatic systems by partial melting s bearing wall rocks with variable degrees of assimilation of miscible silicate and volatile components and generation of barren to weakly mineralized immiscible fe sulfide xenomelts into which ni cu co pge partition from the magma some exceptionally thick magmatic cr deposits may form by partial melting oxide bearing wall rocks with variable degrees of assimilation of the miscible silicate and volatile components and generation of barren fe ti oxide xenocrysts into which cr mg v ti partition from the magma the products of these processes are variably preserved as skarns residues xenoliths xenocrysts xenomelts and xenovolatiles which play important to critical roles in ore genesis transport localization and or modification incorporation of barren xenoliths autoliths may induce small amounts of sulfide chromite to segregate but incorporation of sulfide xenomelts or oxide xenocrysts with dynamic upgrading of metal tenors pge cu ni co and cr v ti respectively is required to make significant ore deposits silicate xenomelts are only rarely preserved but will be variably depleted in chalcophile and ferrous metals less dense felsic xenoliths may aid upward sulfide transport by increasing the effective viscosity and decreasing the bulk density of the magma denser mafic or metamorphosed xenoliths may also increase the effective viscosity of the magma but may aid downward sulfide transport by increasing the bulk density of the magma sulfide wets olivine so olivine xenocrysts may act as filter beds to collect advected finely dispersed sulfide droplets but other silicates and xenoliths may not be wetted by sulfides xenovolatiles may retard settling of or in some cases float dense sulfide droplets reactions of sulfide melts with felsic country rocks may generate fe rich skarns that may allow sulfide melts to fractionate to more extreme cu ni rich compositions xenoliths xenocrysts xenomelts and xenovolatiles are more likely to be preserved in cooler basaltic magmas than in hotter komatiitic magmas and are more likely to be preserved in less dynamic less turbulent systems domain phases than in more dynamic more turbulent systems domains phases massive to semi massive ni cu pge and cr mineralization and xenoliths are often localized within footwall embayments dilations jogs in dikes throats of magma conduits and the horizontal segments of dike chonolith and dike sill complexes which represent fluid dynamic traps for both ascending and descending sulfides oxides if skarns residues xenoliths xenocrysts xenomelts and or xenovolatiles are present they provide important constraints on ore genesis and they are valuable exploration indicators but they must be included in elemental and isotopic mass balance calculations

impact of tunneling on regional groundwater flow and implications for swelling of clay sulfate rocks tunnels play a key role in many transportation concepts the swelling of clay sulfate rocks leads to serious damage to many tunnels crossing such rock producing great difficulties and high extra costs in tunnel engineering the swelling is caused by the transformation of the sulfate mineral anhydrite into gypsum entailing a 60 volume increase the transformation involves anhydrite dissolution in water transport of the solution with groundwater flow and gypsum precipitation at a different location therefore the knowledge of groundwater flow systems at the tunnel and adjacent areas is essential to better understand the swelling processes the present study investigates the groundwater flow systems at the chienberg tunnel in switzerland before and after the tunnel excavation based on numerical flow modeling the models include faults and the hydrostratigraphic layering in the subsurface to assess the role of the hydrogeological setting the results of this study indicate effects on groundwater flow caused by the tunneling which may trigger rock swelling by favoring anhydrite dissolution and gypsum precipitation including 1 increase of flow rates around the tunnel 2 broadened shifted and more distributed capture zones leading to a change in origin and age of groundwater 3 access of groundwater from preferential flow paths e g faults due to the drainage effect of the tunnel and 4 change in geochemical equilibrium conditions because of decreased pore water pressures in the tunnel area

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

rock salt dilatancy boundary from combined acoustic emission and triaxial compression tests abstract this paper presents an experimental investigation of rock salt dilatancy boundary based on combined acoustic emission and triaxial compression tests carried out on the rock salt samples from the asse salt mine germany the experimental results were evaluated to determine the dilatancy boundary under specified stress stress loading rate and pore pressure pore volume changes caused by deviatoric stresses were measured during triaxial compression tests the dilatancy boundary was then determined from the maximum compression on a stress strain curve which separates the compression and dilatancy regions variations in acoustic emissions that occur during microcrack development under triaxial compression were recorded with ten sensors mounted on the outer surface of the cylindrical samples a spontaneous increase observed in the cumulative number of acoustic events is consistent with the dilatancy boundary determined from the minimum pore volume it is confirmed that the dilatancy boundary depends on both stress loading rate and pore pressure the dilatancy boundary slightly decreases with increasing the loading rate but increases with increasing the minor normal stress high pore pressures accelerate the dilatancy a biot coefficient of 0 25 for asse rock salt was determined from the dilatancy boundary an analysis of two dimensional 2d fractal dimensions determined for several samples shows that the samples with smaller dimensions have slightly higher dilatancy boundaries the dilatancy boundary values of asse rock salt are lower than those reported for crystalline rocks although both rock types show similar dilatancy behaviour

textural development in sulfide matrix ore breccias in the voisey s bay ni cu co deposit labrador canada abstract magmatic ni cu sulfide ores at voisey s bay contain complex assemblages of extremely heterogeneous rocks these range from polymict breccias with rock fragments in sulfide rich and or sulfide poor matrices to heterogeneous vari textured gabbros with rapid short range variations in grain size and content of hydrous phases rock fragment populations in the breccias include endogenous olivine gabbros cumulate and non cumulate and cumulate peridotites along with extensively depleted plagioclase hercynite gneisses interpreted as restites from extensive partial melting of country rock quartzo feldspathic paragneisses using a combination of desk top microbeam xrf mapping at cm scale and 3d x ray tomography we show that both sulfide poor and sulfide rich breccias comprise heterolithic assemblages of clasts within a matrix of olivine gabbro this matrix is characterised by an interconnected 3d framework of plagioclase crystals highly variable in grain size at mm to cm scale with interstitial olivine and poikilitic clinopyroxene and is texturally indistinguishable from clast free olivine gabbro sulfide forms interconnected networks at cm to dm scale and possibly larger much of the plagioclase developed by outgrowth from the margins of paragneiss xenoliths when the porosity was occupied by silicate melt the observed range of textures is explained by a model of percolation of molten sulfide through variably crystalline inter clast matrix displacing the silicate melt to leave the refractory plagioclase olivine or in some cases plagioclase only component now entirely within a sulfide matrix the process is analogous to that believed to have formed interspinifex ore in komatiite hosted deposits biotite rims on plagioclase enclosed in sulfide are interpreted as the result of reaction between plagioclase olivine and a hydrous component derived from the sulfide melt itself with a possible component of migrating residual silicate melt wicking along sulfide silicate contacts this sulfide infiltration model offers an alternative to the current model for upward emplacement of a slurry of silicate melt sulfide melt and breccia fragments as a late stage injection into the dyke sill complex the preserved range of textures is interpreted as being due to gravity driven percolation of sulfide liquid through a pre existing partially molten intrusion breccia in this model the breccia serves as a physical trap site accumulating downward migrating sulfide liquid however the invariable close mutual association of sulfide and rock fragments at voisey s bay implies a common derivation

effects of tunneling on groundwater flow and swelling of clay sulfate rocks 1 swelling of clay sulfate rocks is a major threat in tunneling it is triggered by the transformation of the sulfate mineral anhydrite into gypsum as a result of water inflow in anhydrite containing layers after tunnel excavation the present study investigates the hydraulic effects of tunneling on groundwater flow and analyzes how hydraulic changes caused by excavation lead to water inflow into anhydrite containing layers in the tunnel area numerical groundwater models are used to conduct scenario simulations that allow one to relate hydrogeological conditions to rock swelling the influence of the topographic setting the excavation damaged zone around the tunnel the sealing effect of the tunnel liner and the geological configuration are analyzed separately the analysis is performed for synthetic situations and is complemented by a case study from a tunnel in switzerland the results illustrate the importance of geological and hydraulic information when assessing the risk of swelling at an actual site

the enigmatic ascent of ca sulphate rocks from a deep dense source layer evidences of hydration diapirism in the lesina marina area apulia southern italy in the lesina marina village area the cropping out gypsum rocks that rose up from the deep and thick upper trias burano fm anhydrite layer have been analyzed to investigate the trigger mechanism for their ascent in this regard we focus on the anhydrite to gypsum transformation starting from the deep source layer indeed petrographic observations of the widespread corroded anhydrite crystals embedded in these gypsum rocks revealed unequivocal evidences of the anhydrite to gypsum transformation in addition and referring to gypsum microstructural features indicate that ductile deformation mechanisms initially operated under higher temperature conditions this temperature should be close to 107 c namely the value of the upper temperature limit of stability of gypsum from lesina marina above which it starts to transform and dehydrate as revealed by microthermometry heating dehydration experiments combined with micro raman analyses all these evidences are in favor of the dramatic density decrease and volume increase due to anhydrite to gypsum transformation by hydration in the deep source layer these variations of physical conditions triggered by hydration promoted diapirism of the gypsum mass in other words hydration diapirism as revealed by seismic lines interpretation the diapirism which gave rise to the lesina diapir occurred during plio pleistocene and was genetically related to the lesina graben type structure hydration at depth was favored by the downward circulation of water rich fluids channeled in faults and the gypsum mass used the weakened zone of the southern fault to pierce the overlying mesozoic and tertiary sediments

the distribution of pge and the role of arsenic as a collector of pge in the spotted quoll nickel ore deposit in the forrestania greenstone belt western australia the spotted quoll pge bearing ni deposit in the forrestania greenstone belt in the archean yilgarn block in western australia is a komatiite associated massive sulfide orebody tectonically displaced from its original host the brecciated ore contains clasts of quartz and garnet schist and is located along a shear zone overlain by banded iron formation bif and underlain by bif and quartz biotite metasediments the deformation of the ore has destroyed its magmatic textures and it has been sheared and recrystallized at amphibolite facies then the deformed ore has been subjected to a hydrothermal event that concentrated the pge with au and as often at the edge of the ni ore the pge are distributed between pgm and in solid solution in ni sulfarsenides and pd also occurs in pentlandite the pgm include sudburyite pdsb sperrylite ptas2 and irarsite irass all six pge and minor au are hosted in gersdorffite niass two generations of gersdorffite have been recognized a higher temperature magmatic euhedral co rich gersdorffite encloses ir pt and rh bearing pgm surrounded by halos of rh ir and os rich gersdorffite a lower temperature ni rich gersdorffite forms anhedral grains and rims on grains of nickeline nias in this low temperature gersdorffite pge are concentrated toward the mineral edges sudburyite and gold occur associated predominantly with nickeline the pge and gold are now predominantly associated with sulfarsenides that are the controlling factor for their distribution

mathematical modeling of thermomechanical erosion beneath proterozoic komatiitic basaltic sinuous rilles in the cape smith belt new quebec canada virtually all of the economic ni cu platinum group element pge mineralization in the central part of the cape smith belt of new quebec is hosted by thick olivine cumulate units in the katinniq member of the raglan formation at the base of the 1 9 ga chukotat group these units transgress underlying gabbros and pelitic metasediments forming 50 200 m deep and 300 1 000 m wide v shaped embayments and have been interpreted on the basis of surface geology deep diamond core drilling and magnetic inversion models to represent the remnants of one or more large long at least 20 km possibly 50 km sinuous komatiitic basalt lava channels that formed by thermomechanical erosion of their substrates we have used a mathematical model to test these hypotheses regarding komatiitic lava emplacement and erosion by lava our modeling predicts that an initially 10 m thick komatiitic basalt flow should have flowed turbulently near the vent and should have thermomechanically eroded unconsolidated pelitic sediment during emplacement to reach the observed degree of contamination of 10 at distances of 30 60 km downstream from the source furthermore our models predict that at these distances downstream a fully inflated 100 m thick komatiitic basalt flow would have had thermal erosion rates over consolidated gabbroic substrate of 0 7 1 5 m day requiring 70 140 days to incise a 100 m deep channel depending on the initial temperature of the lava the paleoslope and the initial temperature and solidus temperature of the gabbro these erosion rates would have been associated with volumetric flow rates of 105 106 m3 s and eruption volumes of 103 104 km3 although these flow rates are orders of magnitude larger than those of most modern terrestrial basaltic flows they are of the same order as those estimated for the largest terrestrial flood basalt flows and with those inferred for some of the largest extraterrestrial flows our predicted flow volumes are also of the same order as those of the largest terrestrial flood basalt units consistent with the great thickness and widespread distribution of the chukotat group our modeling of thermomechanical erosion of gabbro by komatiitic basalt results in negligible contamination middle ree heavy ree nb ta ti represent contamination by underlying povungnituk semipelites this result is consistent with present models for the genesis of the ni cu pge mineralization in the raglan formation that involve thermomechanical erosion of unconsolidated sulfidic semipelitic sediments and decoupling of the miscible silicate and immiscible sulfide components

relationship between microstructures and grain scale trace element distribution in komatiite hosted magmatic sulphide ores komatiite hosted nickel sulphides from the yilgarn craton australia consist of two main sulphide phases pyrrhotite fe7s8 and pentlandite fe ni 9s8 two minor sulphide phases chalcopyrite cufes2 and pyrite fes2 and trace arsenides samples of massive sulphides from three deposits with diverse deformation and metamorphic histories the silver swan perseverance and flying fox deposits have been studied by electron backscatter diffraction and laser ablation inductively coupled plasma mass spectrometry and nano scale secondary ion mass spectrometry these ore bodies were selected to investigate the relationship between microstructures and mineral trace element chemistry in three dominant sulphide species in each deposit in all three samples pyrrhotite preserves a strong evidence of crystal plasticity relative to both pentlandite and pyrite the trace element composition of pyrrhotite shows significant variation in specific elements pb bi and ag this variation correlates spatially with intragrain pyrrhotite microstructures such as low angle and twin boundaries minor signatures of crystal plasticity in pyrite and pentlandite occur in the form of rare low angle boundaries pentlandite and mild lattice misorientation pyrite trace element compositions of pentlandite and pyrite show no correlation with microstructures variations in pyrrhotite are interpreted as a result of intragrain diffusion during the syn and post deformation history of the deposit intragrain diffusion can occur either due to bulk diffusion dislocation impurity pair diffusion or by pipe diffusion i e along fast diffusion pathways at high and low angle and twin boundaries this contribution examines three different diffusion models and suggests that dislocation impurity pair diffusion and pipe diffusion are the most likely processes behind increased trace element concentration along the microstructures in pyrrhotite the same phenomenon is observed in samples from three different deposits that experienced widely different metamorphic conditions implying that the final disposition of these elements reflects a post peak metamorphic stage of the geological history of all three deposits

seven year history of vertical hydraulic diffusivity related to excavation around an underground facility abstract significant amounts of groundwater drain induced by the excavation of an underground facility will influence various site formation parameters such as permeability in this study a spectral analysis was applied to long term records of pore pressure responses to atmospheric loading in order to clarify the history of rock permeability changes at the horonobe underground research laboratory url in japan this study revealed that excavation of the url influenced nearby aquifers and reduced their vertical hydraulic diffusivity at a point approximately 130 m distant from the url it was found that hydraulic diffusivity has decreased by approximately 7 to 55 in the five years since the excavation started at a point approximately 860 m distant from the url the vertical hydraulic diffusivity was found to have decreased by approximately 26 even though pore pressure had not changed significantly this study confirmed that long term permeability changes could be monitored via pore and atmospheric pressure records more specifically during the development of a geological disposal system which can take several tens of years the vertical permeability of the site can be continuously monitored from the period before the start of the excavation through to the repository s post closure period

influence of tectonic shears on tunnel induced fracturing abstract the opalinus clay is currently under investigation as a potential host rock for deep geological disposal of nuclear waste at the mont terri rock laboratory in switzerland bedding in the opalinus clay at mont terri is ubiquitous and highly persistent leading to mechanical transverse isotropy adding to the complexity at the rock laboratory is the frequent occurrence of small scale tectonic shears this paper explores the influences of millimetre thick tectonic shears and bedding on the development of induced fractures mapped in the ez b field experiment at the research facility a series of numerical analyses were carried out by increasing the geological complexity of the host rock and comparing the redistributed stress field with geological maps of the induced fractures the analyses show that if tectonic shears are not kinematically constrained mobilisation of the shears can play a key role in the development of the induced fracture network and therefore be a primary factor in the development of the excavation damaged zone this illustrates that under certain conditions rock mass heterogeneity in this case resulting from the tectonic shears may dominate over rock matrix anisotropy in this case resulting from bedding and must be considered when predicting the induced fracture network of the excavation damaged zone

the nickeliferous late archean reliance komatiitic event in the zimbabwe craton magmatic architecture physical volcanology and ore genesis the widespread komatiitic reliance lithostratigraphic unit of the late archean bulawayan supergroup consists of many submarine flow fields directly or indirectly overlying the sedimentary manjeri unit which varies from a generally carbonaceous sulfide rich deep water basinal facies in the north and west parts of the zimbabwe craton to a generally sulfide poor shallow water platformal facies in the south and east the flow fields are associated with high level subvolcanic feeder sills intruded into pre manjeri basement made up of the conformable sulfide bearing felsic koodoovale unit and older barren granitoid greenstone crust in the north and west and south and east respectively the sills and flow fields together constitute largely discrete sill flow complexes very approximately 100 km in diameter of which five are well preserved in the north and west and three in the south and east parts of the craton the reliance sills up to 40 km in diameter and 2 000 m thick some composite and locally overlapping to slightly discordant mostly comprise a thick lower dunite peridotite and a relatively thin to intermittent upper pyroxenite gabbro other larger probably related sills intruded at greater structural depths link adjacent complexes and form midcrustal magma chambers the reliance sills are interpreted as an interconnected system of flow through feeders at different crustal levels the reliance flow fields are 33 to 85 km in diameter and up to 2 500 m thick dominantly of komatiitic basalt composition of very low height breadth aspect ratio locally linked to the sills via structures interpreted as fissure vents and partly extrusive cryptodomes and thin out toward their lateral margins most display a simple coherent volcanological growth sequence from sheet and or channelized sheet flows and lava channel complexes in lower and proximal positions to marginal lava lobes in upper and distal positions comparable in general organization and probable emplacement processes to those of hawaiian and flood basalt flow fields flow field development was influenced by episodic eruption preexisting topographies and penecontemporaneous sedimentation and felsic and mafic volcanism and some flow fields in the south and east were partly emergent sills in the north and west are weakly mineralized but those in the south and east are barren the principal reliance nickel sulfide deposits are confined to flow fields in the north and west occur within lava channel complexes trojan and shangani mines damba silwane and hunters road prospects and a fissure vent epoch mine and include type 1 basal sequences of massive to matrix to disseminated sulfides lowermost flows trojan shangani and type 2 central accumulations of weakly disseminated sulfides hunters road upper flows trojan shangani epoch and shangani occupy central flow field positions whereas hunters road and damba silwane are proximal trojan may be either distal or proximal field evidence does not directly support the origin of the reliance deposits solely by magmatic erosion of sulfidic substrate during flow emplacement as proposed for komatiite hosted nickel deposits elsewhere instead the deposits origin and asymmetric distribution across the craton may be mainly due to assimilation of sulfidic felsic wall rocks during magma passage through the subvolcanic sills in the north and west possibly combined with sulfur degassing due to very shallow water lava emplacement in the south and east

geohydromechanical processes in the excavation damaged zone in crystalline rock rock salt and indurated and plastic clays in the context of radioactive waste disposal abstract the creation of an excavation disturbed zone edz or excavation damaged zone edz is expected around all man made openings in geologic formations macro and micro fracturing and in general a redistribution of in situ stresses and rearrangement of rock structures will occur in this zone resulting in drastic changes of permeability to flow mainly through the fractures and cracks induced by excavation the edz may have significant implications for the operation and long term performance of an underground nuclear waste repository various issues of concern need to be evaluated such as processes creating fractures in the edz the degree of permeability increase and the potential for sealing or healing with permeability reduction in the zone in recent years efforts along these lines have been made for a potential repository in four rock types crystalline rock salt indurated clay and plastic clay and these efforts have involved field laboratory and theoretical studies the present work involves a synthesis of the ideas and issues that emerged from presentations and discussions on edz in these four rock types at a cluster conference and workshop held in luxembourg in november 2003 first definitions of excavation disturbed and edzs that may be applicable to all four rock types are proposed then an approach is suggested for the synthesis and intercomparison of geohydromechanical processes in the edz for crystalline rock salt indurated clay and plastic clay comparison tables of relevant processes associated factors and modelling and testing techniques are developed a discussion of the general state of the art and outstanding issues is also presented a substantial bibliography of relevant papers on the subject is supplied at the end of the paper

oxidation front and oxygen transfer in the fractured zone surrounding the meuse haute marne url drifts in the callovian oxfordian argillaceous rock

the agnew nickel deposit western australia part i structure and stratigraphy the agnew formerly perseverance nickel deposit in the agnew wiluna greenstone belt of the yilgarn block has previously been assigned to the category of intrusive dunite associated deposits on the basis of detailed reinterpretation of the geology of the deposit we conclude that the nickel sulfide mineralization is hosted by komatiite flows which predate the associated dunite body which is itself extrusive nickel sulfide mineralization is hosted by a suite of metamorphosed olivine rich ultramafic rocks containing widely varying proportions of tremolite and chlorite chemical analyses of these rocks show them to be metamorphosed komatiites in which original asymmetric differentiation profiles can be recognized these provide facing directions which form the basis for structural and stratigraphic interpretation much of the massive sulfide has been structurally remobilized into fold noses and planar fractures but some retains primary igneous contacts with underlying flow tops primary contacts are characterized by a zone of skeletal chromite developed across the interface between massive sulfide and flow top the primary massive ore postdates a thick komatiite flow which hosts the matrix ore the dunite body shows a discordant lower contact which truncates stratigraphic marker units in the country rock at the northern limit of the mine area the base of the dunite is separated from the top of the main mineralized flow by more than 150 m of felsic volcanic rocks at the southern limit of mine development the dunite directly overlies the matrix ore zone of the mineralized flow this discordant contact is interpreted as the base of a thermal erosion channel formed by an extensive komatiite lava river the geometry of this contact and the competence contrast between the dunite body and the country rocks exerted a dominant influence on subsequent deformation and sulfide remobilization

improving precision in regional scale numerical simulations of groundwater flow into underground openings abstract dewatering is a common engineering practice to secure the accessibility during the construction and operational phases of tunnels it is thus important to accurately estimate the amount of groundwater flow into underground openings for the design and safe operation of tunnels numerical models need to be used to estimate groundwater flow into openings for given heterogeneity and regional hydrologic boundary conditions typically by assuming that the atmospheric pressure is maintained along open wall faces as the scale of openings can be small as tens of centimeters while models need to incorporate the regional hydrologic conditions it is often practically impossible to explicitly represent the three dimensional 3d geometry of openings within numerical models for the safety assessment of deep geological repositories of spent nuclear fuels for example complex configurations and geometry of various tunnels such as construction access ventilation and deposition tunnels often need to be approximated as one dimensional 1d lines in 3d models the application of a simple dirichlet boundary condition along a set of tunnel nodes may yield inaccurate solutions due to geometric simplifications and coarse discretization this study derives an appropriate boundary condition that can be applied to 1d tunnel segments to improve the accuracy when simulating inflow into openings a third type tunnel boundary condition is suggested to correct the difference between known wall pressure and the pressure simulated at tunnel nodes improvement in the precision of the solutions is demonstrated by comparing the numerical solutions using the new boundary condition with analytic solutions and with numerical solutions when the 3d tunnel geometry is explicitly simulated it is also shown that the formulation can be easily extended to incorporate the high permeability excavation damaged zone and the low permeability grouted zone in the tunnel vicinity the applicability of the tunnel boundary condition is demonstrated using an example of a hypothetical deep geologic repository system consisting of various types of tunnels located in a hypothetical crystalline coastal aquifer

core disking and its relationship with stress magnitude for lac du bonnet granite abstract core disking is an indicator of elevated stress magnitudes disked cores from boreholes drilled from underground excavations in massive unfractured granite where the stress magnitudes are known with confidence were used to establish a relationship between core disk thickness and the stress magnitude relationships were established for three disk thickness categories 1 thin t d 0 2 2 medium 0 2 t d 0 4 and 3 thick 0 4 t d 2 2 and partial disking the data suggests that core disking initiates when the maximum principal stress normalized to the tensile strength is 6 5

volcanological and structural controls on mineralization at the mount keith and cliffs komatiite associated nickel sulfide deposits agnew wiluna belt western australia implications for ore genesis and targeting the mount keith region of the agnew wiluna belt in western australia is perhaps best known for hosting the giant komatiite associated disseminated ni sulfide deposit known as mkd5 it also hosts the sizeable cliffs massive ni sulfide deposit which is the eighth largest in the archean yilgarn block a concerted program of regional scale three dimensional model construction has integrated a plethora of geological geochemical and geophysical data and led to a much better understanding of the tectonic and volcanic architecture of this ancient greenstone belt the disseminated mkd5 orebody occupies a curvilinear thickening in the olivine adcumulate core of the host mount keith ultramafic unit the orebody plunges shallowly to the south from surface over a distance of 3 5 km before bending sharply to plunge steeply to the north northwest at depth the thickest part of the orebody and the best ni grades are associated with the bend in the overall ore trend this also marks the approximate intersection point of two growth faults that appear to control the thickness variations in the adcumulate core and the plunge variations in the ore trend the olivine adcumulate core is mantled by olivine orthocumulate rocks which are best developed above and below the flanks of the orebody and a fractionated sequence of pyroxenitic and gabbroic rocks occurs at the top of the mount keith ultramafic unit above the inside of the bend in the ore trend these observations suggest a strong volcanological control on the position of the mkd5 orebody and the local curvilinear thickening in the adcumulate core is interpreted as a fluid pathway the locus of which was in turn controlled by the intersection of two broadly orthogonal growth faults the cliffs ultramafic unit consists of a lower olivine ortho to mesocumulate unit which varies in thickness along strike overlain by a sequence of thin spinifex textured komatiite flow units intercalated with variably sulfidic tuffaceous shales the cliffs massive ni sulfide deposit occurs at the base of a relative thickening to 100 m in the lower olivine ortho to mesocumulate unit the orebody is typically less than 6 m thick 500 m wide and plunges gently south from surface over a distance of 1 5 km terminating in a structurally complex zone across which there are marked differences in the internal stratigraphy and thickness of the cliffs ultramafic unit the orebody has relatively low tenor maximum 8 ni typically 5 ni and the tenor is strongly zoned with extremely low tenors 1 3 ni developed on the flanks a barren exhalative massive fe sulfide unit is typically present at the base of the cliffs ultramafic unit on the flanks of the orebody and probably acted as a source of sulfur the tenor zonation pattern suggests that the melting and entrainment of the underlying exhalative sulfide horizon occurred more vigorously in the center of the lava pathway the structurally complex zone at the southern end of the cliffs orebody is interpreted as a possible vent location this would explain the relatively low tenor of the orebody and the tenor zonation through limited mixing and entrainment of melted exhalative iron sulfide melt with the komatiite lava the poorly incised nature of the lava pathway and the abrupt change in internal komatiite stratigraphy across this zone there is good evidence that the southern terminations of both the mkd5 and the cliffs orebodies are marked by growth faults at a belt scale these points correspond roughly with the intersection of nne and nw trending lineaments these lineaments are on the order of 5 to 10 km in strike length and are visible in regional geophysical datasets both gravity and magnetics they are likely to mark the position of accretionary structures that were active at the time of volcanism and that probably controlled the volcanic architecture of the komatiite flow field and the location of ni sulfide accumulations within komatiite lava pathways repeated reactivation of these early crustal scale structures during subsequent orogenesis resulted in their upward propagation as sets of late brittle structures of broader significance to the understanding of the generation of komatiite associated nickel sulfide deposits is the conclusion that many such deposits may be developed proximal to vent rather than in a distal setting as has been proposed for the kambalda camp

stages of evolution of a toarcian compacted claystone around galleries excavated between 1 and 124 years ago by the study of noble gases dissolved in pore water at the tournemire underground research laboratory france abstract the purpose of this work is to study the diffusion properties in an argillaceous formation and how these properties change after the excavation of galleries over a long period the tournemire underground research laboratory url located in aveyron france offers the unique opportunity to investigate different stages of the evolution of the so called excavation damaged zone edz over a period of about 124 a four horizontal boreholes parallel to the bedding and one vertical borehole were drilled in order to study diffusion transport in the edz in both directions in galleries excavated 124 13 6 and 1 a ago respectively noble gases dissolved in the pore water of 47 core samples were extracted in order to establish precise depth profiles mainly produced in situ by decay of u and th radiogenic he accumulates in the pore water of rocks and escapes toward the gallery allowing a characterization of the diffusive transport in the edz and its evolution with time for the oldest gallery 1882 1888 core mapping reveals an edz well developed with fractures up to a depth of 1 8 m in this zone all radiogenic he has been lost and at the same time heavy noble gases are trapped in the rock with an enrichment of xe relative to kr and of kr relative to ar from 1 8 m he concentration increases with depth to reach a plateau at about 3 5 m corresponding to a concentration normally found in the unaltered zone considering diffusive transport of the radiogenic he to the edz model calculations allowed proposing transport properties in the unfractured and undisturbed zone uz with a pore diffusion coefficient dp of 1 10 10 m 2 s deduced from the best fit curve to experimental data and a mean porosity of 0 1 obtained form petrophysical measurements the most recent gallery 2008 did not show any evidence of edz at depths greater than 7 5 cm a fracture located around 0 75 m possibly of tectonic origin induced large advection and diffusion losses of he on both sides in the next 50 cm excesses of ar kr and xe are found suggesting diffusion of air from the gallery associated with he losses the 6 a old gallery is clearly influenced by fractures of tectonic origin increasing the edz thickness of 0 7 m up to a damaged zone of 1 8 m based on the he concentration profile the 13 a old gallery 1996 has a net edz of 1 2 m larger than the 0 7 m deduced from the structural analysis by core mapping followed by a disturbed zone of up to 3 5 m that could represent an intermediate stage before the development of fractures in the edz the vertical borehole drilled in the same gallery shows a less extensive damaged zone 1 4 m and allows the determination of a dp of 3 10 11 m 2 s taking into account the anisotropy relative to the stratification plane the rare gas analysis has therefore enabled confirmation and better description of the net time dependent evolution of the edz around drifts in the argillaceous tournemire site no obvious edz for the 1 a gallery 2008 1 2 m width for the 13 a old gallery 1996 and 2 m width for the century old tunnel the occurrence of a disturbed and unfractured zone dz around the 13 a old gallery undetected by structural studies and geophysical methods clearly demonstrates the power of radiogenic he in assessing the transport properties around drifts excavated at different ages in compacted clay rocks

a thermomechanical model for saturated clays a thermomechanical model for saturated clays is proposed within the framework of recent extensions of the cam clay model the results of some tests found in the literature are analyzed and the main features of the thermomechanical behaviour of clays are identified the effect of the overconsolidation ratio ocr on the volume change of a soil expansion contraction submitted to heating is well established using experimental data obtained for selected soils by various authors however existing models need to be modified to correctly model this feature for this reason a new volumetric thermal plastic mechanism is developed that allows for the prediction of plastic strains at higher ocr values the overconsolidation effect observed when heating a normally consolidated soil is also modelled particular attention is paid to the coupling and hardening phenomena related to the combined effects of stress and temperature a qualitative validation is made by examining the response of the model under a given th

mechanical behaviour of heavily compacted bentonite under high suction changes the paper reports the results of an experimental study carried out on a bentonite compacted to a dry density of up to 1 7 mg m3 a high value for this type of soil the soil fabric has been studied using a variety of techniques revealing a clear bimodal pore distribution that corresponds to two distinct structural levels a microstructural one and a macrostructural one the main testing programme has been performed using oedometers especially designed to apply a very large range of suctions by applying the axis translation technique using nitrogen as the gas fluid it has been possible to reach suctions up to 15 mpa the higher suction range has been achieved by applying a controlled atmosphere where the relative humidity has been fixed by a solution of sulphuric acid or salts in this way suctions up to 550 mpa could be reached the maximum vertical stress that could be applied in the apparatus was 10 mpa two types of test have been carried out a tests in which a combination of loading paths at constant suction and drying wetting paths at constant load were applied b swelling tests under constant volume conditions in order to determine the swelling pressure and the stress path followed during wetting the results of the experimental programme are examined taking into account the role of the soil fabric in controlling observed mechanical behaviour in addition the results of the laboratory tests are reproduced and interpreted using a generalised plasticity model that considers explicitly the interaction between macrostructure and microstructure in this way it is possible to achieve a more complete understanding of the mechanisms that underlie observed behaviour and in particular the interplay between the two structural levels

the volcanology of komatiites as deduced from field relationships in the norseman wiluna greenstone belt western australia abstract komatiites in the western part of the norseman wiluna greenstone belt in the yilgarn block of western australia display a wide variety of volcanic facies ranging from very thin differentiated munro township type flow units through to very thick olivine rich cumulate flow units containing high proportions of adcumulate dunite cumulate flow units have been mapped in detail in the agnew wiluna segment of the norseman wiluna greenstone belt in the yakabindie and mt keith areas thick lenticular bodies of olivine adcumulate are flanked and overlain by thinner sheet like sequences of finer grained olivine orthocumulates they show fine scale internal layering broad scale cryptic layering and upper fractionated sequences containing harrisites pyroxene bearing cumulates and in some cases gabbroic derivatives low grade disseminated sulphide mineralisation occurs within the dunite lenses in the stratigraphically equivalent kathleen east area adcumulate dunite grades laterally into olivine orthocumulates and spinifex textured flows a similar relationship is also seen further south where the perseverance ultramafic complex consists of a thick central dunite lens flanked on one side by thin fine grained orthocumulate sequences and on the other by intercalated orthocumulates and spinifex textured flows these field relationships indicate an extrusive origin for the adcumulate dunite bodies the walter williams formation in the west central part of the norseman wiluna belt is a very large cumulate flow unit 150 km long and 30 km wide in presently exposed extent it consists of a central sheet like body of adcumulate dunite underlain and overlain by olivine orthocumulates the adcumulate sheet is everywhere capped by a distinctive thin layer of olivine harrisite at its northernmost extent the flow unit consists of cyclically layered olivine and pyroxene bearing cumulates capped by gabbros dolerites and pyroxene spinifex textured material interpreted as a periodically replenished lava lake sequence both the lenticular dunite bodies of the agnew wiluna belt and the sheet like dunite body of the walter williams formation are interpreted as crystallisation products of very large submarine komatiite lava flows which erupted and flowed at very high rates the adcumulate dunites are interpreted as the products of in situ crystallisation at low degrees of supercooling at the top of upward and inward accreting crystal piles at the bases of the flows flanking and overlying olivine orthocumulates reflect higher rates of heat loss at the site of crystallisation due to lower lava flow rates field evidence from perseverance and the general geometry of the dunite lenses suggest that the lenses formed within large thermal erosion channels developed by turbulent lava rivers flowing over low melting felsic volcanic substrates the textural range exhibited by komatiites can be integrated into a comprehensive model for the geometry of large komatiite flow fields formed by rapid extrusion dunite sheets form close to the eruption sites and dunite lenses as a result of channellisation further away from the vent or close to the vent in the situation where the substrate is non refractory and thermal erosion can take place readily kambalda type volcanic facies develop in more distal environments where lava emplacement is channellised and episodic and munro type flow units represent small scale lava tubes formed at low flow rates on the distal flanks of major eruptions or close to the vent of very small ones waning eruption rates leads to proximal facies being overridden by distal ones a common observation in komatiite sequences the size of thermal erosion channels requires very rapid eruption rates comparable to those in phanerozoic flood basalt terrains

the geology of the kambalda nickel field western australia the kambalda nickel field contains the major concentration of volcanic peridotitc associated nickel ores in the archean of australia it occupies an area of 400 km 2 underlain by two sequences of ultramafic mafic and felsic volcanics and sedimentary rocks which can be broadly correlated with previously erected regional stratigraphic sections most ores occur in the lower kambalda sequence at the base of the kambalda ultramafic rocks the ultramafic rocks of the upper bluebush sequence contain only minor mineralization four phases of deformation occurred over an interval of more than 300 m y resulting in a dominant north northwest structural trend faulting was active during original volcanism and continued intermittently until after mafic felsic dike intrusion the ultramafic rocks have been serpentinized and all rocks have exerienced low strain upper greenschist to lower amphibolite facies metamorphism and variable carbonation and potash metasomatism the kambalda ultramafic rocks are of variable thickness and in places exceed 1 000 m the lower member of the ultramafic rocks occupying approximately one third of the sequence comprises thicker high magnesium flows i e generally 36 volatile free mgo commonly separated by sulfidic quartz albite sediments thinner lower magnesium flow units characterize much of the upper member the ores occur in 24 shoot complexes each containing multiple ore surfaces caused by structural dislocation of a few grouped ribbonlike original orebodies eighty percent is contact ore occurring at the base of the lowermost ultramafic flow and generally occupying elongate troughs in the footwall basalt ultramafic contact these troughs are thought to be original volcanic depressions which focused later deformation the remainder is hanging wall ore usually occurring directly above contact ore at the base of the second or third ultramafic flow hanging wall orebodies occasionally grade into stratigraphically equivalent interflow sediments the ores contain varying proportions of massive matrix and disseminated sulfides the hypogene mineral assemblage is pyrrhotite pentlandite pyrite chalcopyrite but millerite is locally significant the massive ores in particular are commonly severely deformed and some have been remobilized tens of meters from their original contact position metamorphism has caused recrystallization of the ores and some redistribution of elements there is commonly marked variation of mineralogy and s ni ratios between contact and overlying hanging wall ores and within and between original ore surfaces within shoots but the relative contributions of primary composition and metamorphism to this variation are uncertain in ore environments the footwall basalt ultramafic contact is more deformed than in non ore environments the basal ultramafic flows are thicker and richer in magnesium the trend toward lower magnesium flows upward through the ultramafic formation is less well developed and there is better textural development and compositional differentiation within flows non ore environments usually contain interflow sediments whereas there is generally a sediment free prism of ultramafic rocks above ore environments most ores are interpreted to have originated by either simultaneous or sequential extrusion of sulfide melts and ultramafic lavas rich in olivine phenocrysts along active linear fissures in a basaltic ocean floor volcanic exhalations probably contributed to minor ore in sulfidic sediments

considerations and observations of stress induced and construction induced excavation damage zone in crystalline rock abstract bsed on the recent observations from two underground laboratories the construction induced excavation damage zone edz ci caused by explosion or by mechanical excavation and stress induced excavation damage zone edz si are distinguished the key location for in situ testing of edz and method development has been the tbm tunnel in aspo hard rock laboratory in sweden since the 1990s the research and development has been continued between 2010 and 2012 with in situ stress measurement campaign and in 2013 with ground penetrating radar investigations with new gpr edz method the new gpr edz method based on frequency analysis of the reflected signal indicates mean depth for edz ci of 120 mm the same zone is indicated also by various other geophysical and laboratory methods and is distinguished as construction induced and continuous around the tunnel perimeter fracture mechanics modelling suggests a lowered hydraulic conductivity of 1 8 10 13 m s in edz si and 4 0 10 11 m s in edz ci biaxial testing suggests a zone in which young s modulus values are lowered and which is not continuous around the tunnel this zone is distinguished as an observable part of stress induced edz si

yakabindie revisited volcanological and structural controls on the komatiite hosted six mile well and goliath north deposits and implications for the architecture of the 2 7 ga rift event in the agnew wiluna belt yilgarn craton western australia the yakabindie area hosts significant deposits of disseminated fe ni cu sulfide in the six mile well 2 0 mt contained ni and goliath north 0 6 mt contained ni dunite lenses these dunite lenses form part of the same komatiitic ultramafic unit that hosts the giant mount keith mkd5 deposit 2 6 mt contained ni to the north but the morphology and internal stratigraphy of the host unit differs significantly three dimensional modeling of the yakabindie region reveals that each dunite lens is located at the intersection between steeply dipping nnw and nne trending synvolcanic faults which appear to have acted as conduits from which komatiitic lava vented onto the seafloor the igneous contacts dip more shallowly to the west and describe a w facing wedge of olivine cumulate rock probably less than 1 km in plunge extent and cored by adcumulate rock the mineralization at both six mile well and goliath north consists of multiple stacked lenses of disseminated fe ni cu sulfide associated with the olivine adcumulate core this core is interpreted as the pathway position that focused the flow of komatiite lava away from the vent rather than being linked by sheeted bodies of orthocumulate rocks as is typically the case along strike to the north the dunite lenses at yakabindie appear to be capped by a strike continuous sequence of thin komatiite flow units there is no evidence of the fractionated sequences of pyroxenite and dolerite which occur in pathway positions within the mount keith ultramafic unit to the north and which reflect late stage ponding and in situ fractionation of komatiite lava three sets of synvolcanic structures are recognized in the broader agnew wiluna belt and a model of oblique extension at ca 2 7 ga is proposed a nnw trending set of structures marks the overall rift orientation at ca 2 7 ga but is probably inherited from an earlier ca 2 81 ga phase of rifting a nw trending set is thought to represent ca 2 7 ga transfer faults but may also have much older roots these structures produce marked sinistral offsets in both the greenstone stratigraphy and the gravity response and can be used to divide the agnew wiluna belt into rift segments the third set of early structures trends nne subparallel with the volcanic grain of the greenstones as inferred from the orientation of komatiite lava pathways these are thought to have originated as extension orthogonal normal faults at ca 2 7 ga at the regional scale there is a strong spatial association between the larger fe ni cu sulfide deposits of the agnew wiluna belt and the locus of postulated nw trending transfer zones whereas at the deposit scale intersecting nw and nne trending synvolcanic faults exert a control on the location and best development in terms of thickness and or grade of fe ni cu sulfide mineralization in some deposits these spatial associations have major implications for exploration targeting at both regional and deposit scale

the role of fluids in the metamorphism of komatiites agnew nickel deposit western australia the agnew nickel sulfide deposit is spatially associated with a lenticular body of ultramafic rocks which shows a concentric zonation in metamorphic mineralogy olivine tremolite chlorite cummingtonite enstatite assemblages occur at the margin of the ultramafic lens giving way to olivine anthophyllite olivine talc and olivine antigorite assemblages successively inwards these rocks are interpreted as having crystallized from komatiitic lavas and exhibit a spectrum of compositions from those of original flow tops to pure olivine adcumulates the relative modal abundances of metamorphic olivine tremolite and chlorite reflect original proportions of cumulus olivine and komatiite liquid in the protolith peak metamorphic conditions are estimated at 550 c based on garnet biotite thermometry at a maximum pressure of 3 kb this temperature falls within the narrow range over which metamorphic olivine may co exist with enstatite anthophyllite talc or antigorite depending upon the fugacity of water in the metamorphic fluid the observed mineralogical zonation is therefore attributed to infiltration by co2 rich fluids generated by decarbonation of talc carbonate rocks formed during pre metamorphic marginal alteration of the ultramafic lens metamorphic fluids were essentially binary mixtures of water and co2 with minor h2s having a maximum partial pressure less than 1 percent of total pressure enstatite bearing assemblages formed in the presence of co2 rich fluids at fluid rock volume ratios close to one while anthophyllite talc and antigorite bearing assemblages formed in the presence of progressively more water rich fluids at progressively lower fluid rock ratios

effects of joint surface roughness and orientational anisotropy on characteristics of excavation damage zone in jointed rocks abstract investigating the mechanical behavior of the excavation damage zone edz in jointed rocks is essential for underground openings in this numerical study the effects of joint surface roughness and orientational anisotropy on the size and shape of edz in jointed rocks were examined based on a diversion tunnel excavated in columnar jointed rocks at the baihetan hydropower station the results showed that failure zones are usually at the two ends of the tunnel roof both open and shear zones are dependent on the jrc joint roughness coefficient averages and standard deviations with increasing standard deviations of jrc the depths and areas of both open and shear zones generally increase as the jointed rocks changing from anisotropic to isotropic the shapes of edz are similar but rotate in jointed rocks under effects of water pressures larger open zones appear in the lateral tunnel walls and the depths of shear zones increase

geochemistry and petrology of komatiites of the pioneer ultramafic complex of the 3 3 ga weltevreden formation barberton greenstone belt south africa abstract the 3 3 ga weltevreden formation located in the northern part of the barberton greenstone belt contains multiple complexes that are composed largely of well preserved partially serpentinized komatiitic rock the pioneer ultramafic complex is a 1 km thick section of massive and differentiated komatiites and spinifex textured komatiitic basalts that are interbedded with current structured komatiitic tuffs most komatiites were emplaced subaqueously as large sheet flows that would on occasion pond cool slowly and internally differentiate between effusive eruptions explosive komatiitic volcanism resulted in the deposition of up to 60 m thick sections of fine grained ash massive komatiites preserve primitive olivines with a maximum mg of 92 9 supporting the eruption of a high temperature high magnesian liquid al2o3 tio2 19 34 and gd ybn 0 84 1 15 ratios indicate that the komatiites and komatiitic basalts originated from al undepleted to slightly al enriched magma fresh pigeonite found in the cores of zoned pyroxenes suggests that crystallization occurred under anhydrous conditions similar to komatiitic augites analyzed in other areas of the barberton greenstone belt those in the pioneer complex possess both high wo contents 0 31 0 46 and high mg s 75 90 2 but these features are not attributed to high dissolved water contents in the melt

up down or sideways emplacement of magmatic fe ni cu pge sulfide melts in large igneous provinces the preferential localization of fe ni cu pge sulfides within the horizontal components of dike sill lava flow complexes in large igneous provinces lips indicates that they were fluid dynamic tra

investigating the use of 3 d full waveform inversion to characterize the host rock at a geological disposal site the u k government has a policy to dispose of higher activity radioactive waste in a geological disposal facility gdf which will have multiple protective barriers to keep the waste isolated and to ensure no harmful quantities of radioactivity are able to reach the surface currently no specific gdf site in the united kingdom has been chosen but once it has the site is likely to be investigated using seismic methods in this study we explore whether 3 d full waveform inversion fwi of seismic data can be used to map changes in physical properties caused by the construction of the site specifically tunnel induced fracturing we have built a synthetic model for a gdf located in granite at 1000 m depth below the surface since granite is one of the candidate host rocks due to its high strength and low permeability and the gdf could be located at such a depth we use an effective medium model to predict changes in p wave velocity associated with tunnel induced fracturing within the spatial limits of an excavated disturbed zone edz modelled here as an increase in fracture density around the tunnel we then generate synthetic seismic data using a number of different experimental geometries to investigate how they affect the performance of fwi in recovering subsurface p wave velocity structure we find that the location and velocity of the edz are recovered well especially when data recorded on tunnel receivers are included in the inversion our findings show that 3 d fwi could be a useful tool for characterizing the subsurface and changes in fracture properties caused during construction and make a suite of suggestions on how to proceed once a potential gdf site has been identified and the geological setting is known

characterising and modelling the excavation damaged zone in crystalline rock in the context of radioactive waste disposal this paper describes current knowledge about the nature of and potential for thermo hydro mechanical chemical modelling of the excavation damaged zone edz around the excavations for an underground radioactive waste repository in the first part of the paper the disturbances associated with excavation are explained together with reviews of workshops that have been held on the subject in the second part of the paper the results of a decovalex demonstration of coupled models and their validation against experiment research funded by an international consortium of radioactive waste regulators and implementers http www decovalex com research programme on modelling the edz are presented four research teams used four different models to simulate the complete stress strain curve for avro granite from the swedish aspo hard rock laboratory subsequent research extended the work to computer simulation of the evolution of the repository using a wall block model and a near field model this included assessing the evolution of stress failure and permeability and time dependent effects during repository evolution as discussed all the computer models are well suited to sensitivity studies for evaluating the influence of their respective supporting parameters on the complete stress strain curve for rock and for modelling the edz

measurement of in situ stress in weak rocks at mont terri rock laboratory switzerland in situ stress measurements in weak rocks such as clay shales that respond strongly to environmental changes are particularly difficult an extensive in situ stress measurement program has been conducted at the mont terri rock laboratory in northwestern switzerland hydraulic fracturing undercoring around a 600 mm diameter borehole using csiro triaxial strain cells and the borehole slotter were used to establish the state of stress for the opalinus clay at this location conflicting orientations and magnitudes resulted from the measurement programs three dimensional elastic modelling was used in conjunction with tunnel and borehole observations to establish the most likely stress tensor a stress measurement program using a borehole deformation gauge is currently underway to check the stress tensor resulting from the observational modelling

theoretical analyses of stress field in surrounding rocks of weakly consolidated tunnel in a high humidity deep environment abstract the present research aims to mitigate the hazard induced by the expansive deformation of tunnel surrounding rocks during deep coal mining in a high humidity environment firstly based on the theory of humidity stress field and elastoplastic theory the governing differential equation of the mechanical response of surrounding rocks of a circular tunnel is established secondly the present study takes the exponential function based humidity distribution as an example to derive the radius of the plastic zone of surrounding rocks and the theoretical formula for calculating the associated stress field also a detailed analysis is conducted concerning the tunnel humidity humidity affected area effect of support resistance on plastic zone of surrounding rocks and the evolution of stress field of surrounding rocks for various relative locations between the humidity affected area and the area disturbed by the excavation stress finally the accuracy of the humidity distribution function and the calculation method of radius of the plastic zone were verified by field tests results indicate that under the interaction between humidity and excavation induced disturbance the plastic zone of surrounding rocks is expanded compared to that of the case without the influence of humidity the evolution law of stress field is related to the distribution of humidity field and the relative position of the excavation stress disturbance zone the quantitative relationship between plastic zone stress field and humidity given in this paper has certain engineering reference value

a reassessment of the emplacement and erosional potential of turbulent low viscosity lavas on the moon we have reevaluated the role of thermal erosion by low viscosity lunar lavas as a mechanism for the formation of the lunar sinuous rules we have adapted the model of williams et al 1998 and used the compositions of an apollo 12 basalt and a terrestrial komatiitic basalt to investigate the compositional and environmental effects on the flow behavior of low viscosity lavas on the moon and the earth our model predicts that lunar lavas could have erupted as turbulent flows that were capable of flowing hundreds of kilometers on a sufficiently flat unobstructed substrate these results are consistent with previous studies modeling of lavas over a substrate of the same composition shows that thermal erosion rates would have been low 10 cm d 1 as a result long duration eruptions approximately months to years would have been required to incise deep tens to hundreds of meters channels partial melting and mechanical removal of the substrate a mechanism suggested by hulme 1973 to enhance erosion only slightly increases thermal erosion rates other factors such as higher flow rates or lava superheating could have produced deep rules by thermal erosion during shorter duration eruptions a superheated lunar lava not only would have had a higher erosion rate 40 cm d 1 but also would have remained uncrusted for tens of kilometers which is consistent with the open channel morphology of most sinuous rules for lunar lavas with large volatile i e vesicle contents the presence of vesicles would have tended to increase viscosity at low strain rates resulting in shorter turbulent flow distances lower thermal erosion rates and thus shallower erosion channel depths for given eruption durations

emplacement and erosion by archean komatiite lava flows at kambalda revisited we have developed a mathematical model to evaluate the flow and erosional potential of submarine channelized komatiite lavas at kambalda western australia field data from kambalda were used to constrain the choice of important input parameters and model results were compared with data from field studies and geochemical analyses our results suggest that thermal erosion is strongly dependent upon the nature and behavior of the substrate if the substrate is treated as an unconsolidated hydrous sediment that can be fluidized by vaporized seawater then our model predicts that an initially 10 m thick basal kambalda komatiite lava could have produced very high thermo mechanical erosion rates 23 10 m day crustal thicknesses of 5 20 cm at distances of 5 35 km from the source and a high degree of lava contamination 3 12 in contrast if the substrate is treated as a more consolidated anhydrous sediment that could not be fluidized then our model predicts that a kambalda komatiite flow would have had much lower thermal erosion rates 1 2 0 4 m day and degrees of contamination 1 3 and would have had crustal thicknesses of 5 20 cm at longer flow distances of 30 165 km field constraints are generally consistent with our predictions for a non fluidized substrate the reentrant embayments at kambalda are thought to form from either erosion of deep channels in a flat basaltic seafioor huppert et al 1984 or erosion of a thin 5 m sediment with minor undercutting of basalt in pre existing topography lesher et al 1984 our modeling indicates that the former was possible for long eruption durations months whereas the latter was possible for short eruption durations 2 weeks as the latter hypothesis is more consistent with the existing field evidence for thermal erosion at kambalda we believe it is the preferred interpretation

postmagmatic variability in ore composition and mineralogy in the t4 and t5 ore shoots at the high grade flying fox ni cu pge deposit yilgarn craton western australia the high grade flying fox komatiite hosted ni sulfide deposit located in the forrestania greenstone belt of the archean yilgarn craton western australia is hosted in a deformed and metamorphosed volcano metasedimentary succession postmineralization events have sheared and modified the texture and composition of the original massive sulfide ore creating up to 11 distinct ore shoots including massive stringer vein and breccia sulfides composed of pyrrhotite pentlandite chalcopyrite and variable abundances of pyrite ranging up to 40 vol nickel and platinum group elements pge tenor variations were investigated in two ore shoots t4 and t5 all mineralization styles show considerable variability in ni tenor pges show strong linear correlations between ir os ru and rh but poor correlation between pt pd and cu the normalized molar proportions of fe ni and s projected into the fe ni s ternary system show a distinct linear trend of pyrite addition to a typical primary magmatic composition and no correlation with mineralization style the high pyrite content present throughout the flying fox ore is also associated with elevated cu and as contents and is interpreted to be primarily due to the addition of pyrite from circulating fe s cu and as enriched fluids creating pyrite pentlandite intergrowths localized mechanical segregation of pyrite sulfidation of pyrrhotite to pyrite and oxidation of pyrrhotite to pyrite magnetite has also contributed to these increased pyrite contents although to a lesser extent the addition and segregation of pyrite has diluted the ni tenor with no evidence to suggest chemical mobilization of ni

swelling potential of clay sulfate rocks in tunneling in complex geological settings and impact of hydraulic measures assessed by 3d groundwater modeling abstract swelling of clay sulfate rocks is a feared problem in tunneling in such rock causing heave of the tunnel invert and leading to swelling pressures that seriously damage the tunnel lining prediction of the swelling potential of rocks in different tunnel sections and tools to evaluate measures that aim at reducing the swelling risk would be a major aid for designers of tunneling projects and rehabilitation works in order to respond adequately to the swelling problem the study presents a hydrogeological approach to assess the swelling potential of clay sulfate rocks in tunneling using the belchen tunnel in switzerland as a case study it shows that this approach can be applied to complex geological settings using structurally consistent 3d numerical models to simulate groundwater flow influenced by tunneling the models are in particular used to evaluate hydraulic measures that aim at preventing or minimizing water inflow into clay sulfate rocks after tunneling analyzed hydraulic measures include pumping shafts connected to the tunnel drainage sealing structures applied to the rock zone around the tunnel damaged by the excavation process excavation damaged zone as well as groundwater level drawdown in aquifers crossing the tunnel a sensitivity study addresses model uncertainties and evaluates the impact of model parameters on the swelling potential promising measures include the installation of pumping shafts in tunnel sections of clay sulfate rocks at the border to aquifers and permeable fault zones the study shows that monitoring of hydraulic heads as well as of groundwater volumes drained by the tunnel would increase the predictive capability of the models presented results are site specific however the approach to assess the swelling potential of clay sulfate rocks in tunneling and to assess hydraulic measures to respond to the swelling problem can be transferred to other tunneling projects

geochemistry of komatiites from forrestania southern cross province western australia evidence for crustal contamination the 2 9 ga old forrestania greenstone belt is intermediate in character between typical 3 0 ga and 2 7 ga belts in containing both al depleted and al undepleted komatiites the extensive nickel exploration database on the belt provides a unique opportunity to examine geochemical variations in the context of volcanological evolution within each of the six komatiitic units in the greenstone belt there is a transition from komatiites 18 28 wt mgo in the liquid to high and low magnesium komatiitic basalts 5 18 wt mgo with stratigraphic height and much of the chemical variance within the komatiitic suite can be explained in terms of the addition or fractionation of olivine there are however aspects of the incompatible element signatures which must be attributed to other factors the more primitive komatiites from the lower ultramafic units are al depleted al2o3 tio2 10 5 13 0 and depleted in both light and heavy ree lasmn 0 5 gdybn 1 5 komatiites from the uppermost ultramafic units are variably less depleted in al al2o3tio2 16 5 20 5 this is interpreted to reflect decreasing retention of garnet in the source region of the forrestania komatiites over time and possibly a decrease in the depth of melting within the al depleted suite there are also anomalous enrichments in sio2 feo tio2 and zr which correlate with regional variations in the composition of substrate metasedimentary rocks banded iron formation versus felsic tuff coupled with field evidence for trough structures at the base of lava channel sequences these chemical anomalies provide strong evidence for supracrustal thermal erosion by komatiite lavas the forrestania data indicate that 2 9 ga old komatiites were generated over a range of melting conditions spanning those typical of older and younger archaean sequences and that contamination by supracrustal thermal erosion can influence komatiite chemistry on a regional scale

use of tree rings as indicator for groundwater level drawdown caused by tunnel excavation in zhongliang mountains chongqing southwest china tunnel excavation causes geological hydrological environmental and social changes the effects of groundwater level changes caused by tunnelling on tree growth have been poorly understood dendrochronology was used to evaluate the impact of groundwater level drawdown on tree growth tree cores of masson pines were collected from the areas affected by tunnel construction in the zhongliang mountains of chongqing in south western china to study the effects of tunnel excavation on the growth rate of trees by comparing with tree cores collected from unaffected areas excavation and early operation of the first tunnel in the zhongliang mountains from 1968 to 1984 caused a groundwater table drawdown in both karst aquifer and non karst aquifer the lowered groundwater table significantly reduced the growth rate of pine trees and the low growth rate remained for 15 years the effect was experienced up to at least 1 km from the tunnel axis the decline in tree growth was higher in karst than in non karst areas though the effects on the trees of the karst areas were lagging the high precipitation in 1998 contributed to groundwater recovery after which the tree growth recovered moderately but not to the original level groundwater leakage of the recently excavated tunnels did not affect pine trees heavily probably because the pines had adapted to the new hydrogeological conditions and new strategies in tunnel inflow management were adopted in the recently excavated tunnels the use of tree growth rate as an indicator of groundwater table change in tunnelling areas offers a new option to study environmental impacts and the extent of tunnelling effects

quantitative characterization of the excavation damaged zone fracture network in the meuse haute marne underground research laboratory in situ experiment and numerical interpretation of helium injection test

the summer 1997 eruption at pillan patera on io implications for ultrabasic lava flow emplacement galileo data and numerical modeling were used to investigate the summer 1997 eruption at pillan patera on io this event now defined as pillanian eruption style keszthelyi et al this issue included a high temperature 1600 c possibly ultrabasic 140 km high plume eruption that deposited dark orthopyroxene rich pyroclastic material over 125 000 km2 followed by emplacement of dark flow like material over 3100 km2 to the north of the caldera we estimate that the high temperature energetic episode of this eruption had a duration of 52 167 days between may and september 1997 with peak eruption temperatures around june 28 1997 galileo 20 m pixel 1 images of part of the pillan flow field show a widespread rough pitted surface that is unlike any flow surface we have seen before we suggest that this surface may have resulted from 1 a fractured lava crust formed during rapid low viscosity lava surging perhaps including turbulent flow emplacement 2 disruption of the lava flow by explosive interaction with a volatile rich substrate or 3 a combination of 1 and 2 with or without accumulation of pyroclastic materials on the surface well developed flow lobes are observed suggesting that this is a relatively distal part of the flow field shadow measurements at flow margins indicate a thickness of 8 10 m we have modeled the emplacement of putative ultrabasic flows from the summer 1997 pillan eruption using constraints from new galileo data results suggest that either laminar sheet flows or turbulent channelized flows could have traveled 50 150 km on a flat unobstructed surface which is consistent with the estimated length of the pillan flow field 60 km our modeling suggests low thermal erosion rates 20 m erosion channels was unlikely especially distal to the source we calculate a volumetric flow rate of 2 7 103 m3 s 1 which is greater than those for typical mauna loa kilauea flows but comparable to those for the 1783 laki eruption and the inferred flow rates of the roza flows in the columbia river flood basalts the differences in ultrabasic eruption styles on earth and io appear to be controlled by the different eruption environments plumes at sites of ultrabasic eruptions on io suggest strong magma volatile interactions on a low gravity body lacking an atmosphere whereas the geology at sites of komatiite eruptions on earth suggest mostly submarine emplacement of thick flows with a pronounced lack of subaerial explosive activity