magma types and the tectonic evolution of the swedish proterozoic information on tectonic evolution can be obtained from the succession of magmatic types represented i type and s type granitoids and volcanics basic dykes and alkali complexes the earliest proterozoic magmatic activity resulted in the formation of greenstone belts within the karelian continent area probably in the age range 2500 2100 ma this was followed by an event similar to andinotype orogeny at around 1900 ma with i type granitoids and calc alkaline volcanics this progressed to an event of hercynotype which was concluded by about 1750 ma subsequent magmatic activity i type granitoids and volcanics suggests a new phase of andino type orogeny until about 1630 ma s and c sweden or 1500 ma n sweden tension related magmatism at around 1550 ma basic dykes alkaline complexes and gabbro may relate to rifting prior to the independant evolution of sw sweden which includes intrusion of i s type granitoids metamorphism followed by continental rotation and collision with n america at about 1050 ma basic dykes and s type granites are related to subsequent uplift 950 850 ma ago

structural characterization of natural loess and remolded loess under triaxial tests this paper characterizes the microstructural evolution of saturated natural loess from a site in jingyang china during triaxial test along two stress paths for comparison the same soil in remolded state is also characterized mercury intrusion porosimetry mip scanning electron microscopy sem and environmental scanning electron microscopy esem were used for the microstructure investigation results show that the microstructure of natural loess is similar to that of remolded loess before the consolidated undrained cu triaxial tests including conventional triaxial compression ctc test and reduced triaxial compression rtc test on the contrary their microstructures are different after the tests deeper examination shows that loading led to a significant change of inter aggregate pores without modifying the intra aggregate pores in addition the volume of inter aggregate pores after the rtc test is greater than that after the ctc test under the same consolidation stress the microstructure features of natural and remolded loess after the tests are further used to analyze the macro mechanical behavior for better understanding the relationship between them the results show that it is the cementation bonds of which breakage is influenced by stress path and confining pressure that play important roles in the strength and deformation behavior

u pb zircon ages of basement gneisses and discordant felsic dykes from vestranden westernmost baltic shield and central norwegian caledonides four new u pb zircon ages are reported from northern vestranden the northernmost part of the western gneiss region of norway scandinavian caledonides the age of a basement tonalite 1819 6 ma together with earlier datings on granites indicates that the dominantly granitoid basement in vestranden began to form more than 1800 ma years ago the minimum age of a subsequent precambrian migmatization event is given by a u pb age of 1630 80 ma found a granite dyke which cuts migmatitic veining in the basement gneisses while age and lithology suggest general similarity and thereby favour a correlation between the basement granites of the northern part of vestranden and svecofennian granites farther to the east no detailed chronological information is at present available that support such a correlation

influence of structure on the behavior of a saturated clayey loess an intensive experimental investigation by means of triaxial and oedometer tests was performed on a clayey loess that was retrieved from two depths at a location on the southern chinese loess plate

the mechanics of subglacial sediment an example of new transitional behaviour a series of isotropic compression tests and drained and undrained triaxial compression tests have been performed on glacial sediment from iceland langjokull sediment which is well graded is thou

three dimensional geological structures and sliding factors and modes of loess landslides loess environments such as the chinese loess plateau are geologically fragile because of their great thickness loose structure crisscrossing ravines and gullies broken terrain dry climate severe erosion and unevenly distributed rainfall as a consequence loess areas are highly prone to environmental problems and geological hazards the geological structure of the loess is one of the main factors that controls occurrence of these geohazards this study investigated the mechanism of loess landslides and their sliding control mode from the perspective of their geological structure using this mechanism a three dimensional geological model of loess landslides was established the study shows that the structural planes in loess divide a complete slope into separate blocks which enables the fast and deep infiltration of surface water via seepage channels and reduces the shear strength of the soil mass inducing landslides the development and formation of loess landslides are primarily controlled by structural planes and influenced by infiltrated water softening the structural plains various types of structural planes may combine and form structural bodies of different types and scales which control the type depth and scale of loess landslides

geological hazards in loess terrain with particular reference to the loess regions of china abstract the considerable morphodynamic energy provided by the continuing tectonic evolution of asia is expressed in high erosional potentials and very high rates of sediment production that make this continent unequalled as a terrestrial source of primary silt many of these environments are hazardous threatening human occupation health and livelihood especially in regions of dense population such as the loess lands of north china dry loess can sustain nearly vertical slopes being perennially under saturated however when locally saturated it disaggregates instantaneously such hydrocompaction is a key process in many slope failures made worse by an underlying mountainous terrain of low porosity rocks gully erosion of loess may yield very high sediment concentrations 60 by weight characteristic vertical jointing in loess influences the hydrology enlarged joints develop into natural sub surface piping systems which on collapse produce a loess karst terrain collapsible loess up to 20 m thick is common on the western loess plateau foundation collapse and cracked walls are common many rapid events following periods of unusually heavy monsoonal rain slope failure is a major engineering problem in thick loess terrain flow slide and spread types being common the results are often devastating in both urban and rural areas an associated hazard is the damming of streams by landslides the human population increases the landslide risk in china notably through imprudent land use practices including careless water management a number of environmentally related endemic diseases arise from the geochemistry of loess and its groundwaters including fluorosis cretinism kaschin beck disease keshan disease and goitre the chinese desert margins also have a major atmospheric dust problem the effect of such dust upon human health in these extensive regions including many large cities has yet to be evaluated but pneumoconiosis is thought to affect several million people in north and west china

research on loess flow slides induced by rainfall in july 2013 in yan an nw china the yan an area located on the loess plateau in northern shaanxi province china experienced heavy and prolonged rainfall in july 2013 which induced 8 135 slope failures loess landslides and loess flow slides destroying approximately 10 000 cave dwellings and killing 45 people field investigations have indicated that the occurrence of loess flow slides is closely related to infiltration depth slope angle slope morphology rainfall intensity and loess strength the results from this study showed that a most of the loess flow slides in yan an were small scale ranging in volume from tens of cubic meters to hundreds of cubic meters b the loess flow slides only occurred at a depth of 2 m and can effectively prevent loess flow slides

the late archaean to early proterozoic lead isotopic evolution of the northern baltic shield of norway sweden and finland abstract the late archaean rocks of the northern baltic shield comprise high grade gneiss terrains and granite greenstone terrains the high grade gneiss terrains consist mainly of older upper crustal material which became metamorphosed during the lopian orogeny ca 2 9 2 6 ga in contrast the 2 7 ga old granite greenstone terrains comprise mainly mantle derived materials at the southern and western edge the archaean craton became partially remobilized during the svecofennian orogeny 2 0 1 75 ga this orogeny represents a major crust forming event in the baltic shield during which mantle material was added to the crust and older material was remobilized whole rock galena and sulfide trace lead are used to outline lead provinces on the northern baltic shield the archaean lead from the baltic shield defines three secondary lead isochrons at 2 65 ga with different initial lead compositions which reflect average pre 2 65 ga 1 ratios of 8 0 8 1 and 8 3 respectively the variation of the initial lead composition of the high grade gneisses and tonalites lofoten and koitelainen area probably indicates 1 variable crustal residence time and or 2 different degrees of crustal contamination assimilation before the 2 65 ga metamorphic event and the lead from the eastern finland greenstone belts indicates a heterogeneous mantle with respect to u pb before 2 65 ga lead in proterozoic rocks of the different lead provinces defines sets of subparallel mixing fields which can be modelled by a 2 65 ga lead component and a 1 8 ga lead component the parallel offset of these fields reflects the pre 2 65 ga 1 ratio of these terrains i e it reveals the pre 2 65 ga 1 of the involved archaean rocks proterozoic terrains with involvement of archaean lower crustal lead show a poor correlation in the 206 pb 204 pb 208 pb 204 pb diagram whereas the other proterozoic terrains show a good correlation in the 206 pb 204 pb 208 pb 204 pb diagram

influence of grading on the mechanical behaviour of stava tailings tailings dams can be fragile structures and too often they are subject to liquefaction the material they are composed of is rather peculiar having a man made origin and their behaviour is still not very well understood the soil from the stava tailings dams structures that were subject to liquefaction in 1985 causing extensive destruction was investigated in this study as an example of tailings two main aspects of their behaviour have been examined the influence of the percentage of silt and sand that compose the soil on its mechanical behaviour and the susceptibility to liquefaction analysing the behaviour within a critical state framework in this paper it is shown that as the quantity of silt increases the slope and intercept of the normal compression line and critical state line at higher pressures decrease until an inversion of behaviour is observed while at lower stress levels the critical state line changes its position but not its slope this means that the effect of adding silt on the

hydroconsolidation and subsidence of loess studies from china russia north america and europe abstract various approaches to the widespread problem of the hydroconsolidation and subsidence of loess have been suggested these include considerations of rheology thermodynamics phase movements particle packing interparticle bonding pore structure and distribution catastrophe theory topology and simple structural frameworks chinese north american and most european investigators tend to concentrate on mechanisms of loess collapse the russian literature however retains an extra dimension two approaches the syngenetic and the epigenetic approach to the formation of subsiding loess have been defined in the literature most investigators follow a syngenetic approach which appears to be a consequence of the aeolian idea of loess deposition some russian writers in contrast promote an epigenetic approach in which collapsibility can develop in an originally noncollapsible material which can then suffer from hydroconsolidation and subsidence the basis of the phenomenon is a change in the packing structure of the major loess particles and this can be modelled using simple monte carlo methods to develop appropriate structures this paper aims to review the work done on this important subject serious investigation of hydroconsolidation and subsidence of loess began in the early nineteen forties fifty years ago and this has been reported in a piecemeal manner a detailed critical review of this diverse work is now overdue and this is presented herein in the light of recent work in the united kingdom an attempt is made to describe the process in a phenomenological and a structural sense inherent in this the role of n ya denisov as subsidence pioneer is considered

new lead isotope determination from five proterozoic sulfide deposits skellefte district sweden lead isotope analyses of 25 sulfide samples galenas iron sulfides and sulfosalts from five different mines of the skellefte district northern sweden demonstrate that the pb isotopic composition of galenas and other sulfides rich in lead varies between individual deposits within the district this contrasts with many other base metal districts where ore lead is isotopically homogeneous on a regional basis although all of the skellefte leads are depleted in 207pb relative to average global lead evolution models thus suggesting a large mantle derived component in their sources the nasliden deposit lying at the contact of the host volcanic rocks and the overlying metasediments contains a significant component of crustal lead it is concluded that while the pb isotope data are consistent with a volcanic exhalative origin of the ores of the skellefte district they also demonstrate that older crustal lead was incorporated into the sulfides during their emplacement and the subsequent period of magmatic and metamorphic activity which followed their deposition

interaction between landsliding materials and the underlying erodible bed in a loess flowslide abstract loess landslides exhibit strong interactions with the terrace sediments of the jing river on the south jingyang platform jingyang xi an china analysis of past landslide events revealed that the sand layer of this terrace was thrust up to the surface accompanied by other terrace sediments of carrying this led to the formation of a thrust nappe structure over a long distance we performed ring shear tests to examine the shear behavior of this sand layer with the finding that saturated sand was highly susceptible to liquefaction induced failure the groundwater level of the study area is high resulting in near saturation of the sand layer therefore topographic interferences contributed additional variables and increased interaction complexities simulations indicated that the liquefied sand layer was compressed and forced due to the absence of constraints the sand layer near the bottom of the slope was sheared out over a relatively short distance on the other hand particle interia and constraints of the stable layer resulted in the sand layer near the distal part of the deposits being sheared upward to the ground finally an initiation movement model of loess flowslides is proposed it describes static liquefaction of the loess layer of the slope resulted in occurrence of flowslides collisions between the deposits from the platform edge slope and terrace sediments resulted in the shear liquefaction of sands the landslide experienced four stages as they moved scraping collisions floating scrapes folded thrusts and nappe accumulation

failure mechanisms in loess and the effects of moisture content changes on remoulded strength abstract investigations into the failure mechanisms of loess slopes in the loess region of north central china have shown that a majority of mass movements are associated with shallow slab slides predominantly moving under tension the effects of soil moisture content are of paramount importance when dry vertical slopes in loess may exceed 15 m in height but under conditions close to saturation the structural strength of loess rapidly decreases causing failure of the slopes mass failure of loess occurs as collapse due to hydroconsolidation and disintegration of the loess fabric as a result of liquefaction or fluidization and can be associated with progressive failure processes local destruction of the openwork fabric of the loess can lead to small plastic movements within the loess deposits this is as close as loess can come to creep

centrifuge model testing of a loess landslide induced by rising groundwater in northwest china abstract considerable artificial irrigation in the heifangtai area has caused the continued rise of groundwater levels which has resulted in several large scale landslides in the loess platform area considering the no 13 landslide of jiaojia in the heifangtai area as a geological archetype a series of centrifuge tests was conducted to study the deformation and failure characteristics of the slope due to the continuous rise in the groundwater level meanwhile the pore water pressure earth pressure deformation and evolution characteristics of the slope were monitored and recorded in real time furthermore isotropically consolidated undrained triaxial testing icu was conducted to investigate the static liquefaction of loess specimens which was related to the slope instability the centrifuge test results showed that a series of parallel and steep tension cracks at the top of the slope were present before the landslide which was caused by the rising groundwater the icu experimental results showed that as the pore water pressure increased strong strain softening and static liquefaction of saturated loess soils were found which was related to the sudden destruction of the slope

the post yield behaviour of four eocene to jurassic uk stiff clays a detailed study is described of the post yield behaviour of four medium plasticity heavily overconsolidated uk stiff clays sub layers of the stiff to hard gault kimmeridge and oxford clays were identified sampled and tested these along with facies investigated in an earlier london clay study had broadly similar depositional histories the intention in considering a spread of similar sediments from the jurassic to the eocene was to allow any strong effects of geological age or burial depth to be identified a strongly fissured meso structure was present in three of the four clays which had a controlling influence on their effective shear strengths considering that the representative element volume is of paramount importance in measuring the strengths of such soils all four soils were brittle in shear and when sheared to sufficient displacements developed low residual shear strengths the stiff clays were investigated further through comparisons between natural and reconstituted behaviour usi

influence of structure on shear characteristics of the unsaturated loess in lanzhou china abstract loess is typically a kind of soil with metastable structure which makes loess sensitive to collapse and sliding upon wetting such structure has thus profound influence on loess s mechanical behavior however there have been arguments about how the metastable structure influences on loess s mechanical behavior and what the mechanism behind is in this study the influence of structure on shear characteristics of the unsaturated loess in lanzhou city of china was investigated with comparison of variation of shear strength and its parameters between six pairs of the undisturbed and remolded samples it is found that the peak shear strength and strength parameters of the loess significantly reduced once its structure was destroyed while shear behavior of the loess showed little change strength parameter c was much more sensitive to structure of the loess than shear strength reduction of the loess due to change of structure should be largely attributed to breaking up of cementation bonds between particles evidenced by the difference in pore size distribution and microstructure of soil fabrics between the undisturbed and remolded samples the bonds provided by clays and carbonates contributed the most to structure of the loess with minor by soluble salts while matric suction played little role in structure of the loess

the mechanics of a saturated silty loess with a transitional mode problems of identifying unique normal compression and critical state lines have been found in gap graded soils and also some silty soils a mode of behaviour sometimes known as transitional loess is a typical silty soil that covers up to 631 000 km2 in china and is of great significance as a result of the large number of engineering projects under construction to examine the potential transitional behaviour in loess an extensive series of carefully controlled oedometer tests and triaxial tests on intact and reconstituted specimens were carried out loess specimens with a wide range of initial void ratios were reconstituted using different preparation methods intact specimens were taken from two depths but their natural variabilities were not significant and could be neglected apart from their difference in the initial void ratios the results have highlighted the features of transitional behaviour in this loess not only in reconstituted but also intact states and in particular that there is an i

liquefaction of crushable soils crushable soils when sheared in a dense state have stress paths which are similar to those for loose hard grained sands however because of their angular nature they do not liquefy as easily under cyclic loading in the hyogo ken nambu 1995 earthquake there was widespread liquefaction of land areas reclaimed from the sea using a crushable highly angular decomposed granite soil masado which was previously regarded as a high quality fill material with little risk of liquefaction in earthquakes results are presented from monotonic and cyclic triaxial tests on three types of crushable soil namely masado shirasu volcanic sand and dogs bay carbonate sand together with standard silica toyoura sand to establish liquefaction criteria which can be applied not only to hard grained silica sands but also to more angular crushable sands in monotonic triaxial testing the stress paths passed through a point of phase transformation with each material exhibiting large strains after this point normalization

geology geochemistry age and geotectonic evolution of the dala granitoids central sweden abstract the dala granitoids and their associated volcanic products are part of a major palaeoproterozoic igneous complex the 1 85 1 67 ga transscandinavian igneous belt tib in the fennoscandian shield tib constitutes the south western border of the svecofennian domain which was formed by an orogenic episode at 1 93 1 83 ga earlier plate tectonic models proposed that tib is a postorogenic batholith complex which was formed in a compressional tectonic regime representing an andino type environment whereas an extensional tectonic regime has been proposed for the anorogenic 1 65 1 51 ga rapakivi granites in the svecofennian domain in this paper a key segment of tib the dala granitoids is discussed in order to focus attention on the post to anorogenic magmatic evolution in the svecofennian domain three types of granitoids jarna siljan and garberg can be distinguished within the dala granitoid complex the jarna granitoids are the most primitive and were emplaced at a significant depth in the crust at ca 1 79 ga the 1 70 1 68 ga siljan and garberg granites are more evolved and were emplaced at a shallow level in the crust closely associated in space time and origin with the volcanic dala porphyries field relationships as well as geochemical and geochronological data indicate magma genesis within a compressional tectonic regime for the 1 79 ga jarna granitoids however most of the dala granitoids appear to have formed in an extensional tectonic regime which was initiated during the last phase of tib magmatism this extensional igneous component is represented by the 1 70 1 68 ga high level siljan and garberg granites and their closely associated volcanic products the dala porphyries an improved model for the formation of the post to anorogenic magmatism in the svecofennian domain suggests that the dala granitoids represent a post to anorogenic igneous key complex which reflects the transition from a compressional to an extensional tectonic environment along a plate boundary

steady state concepts and static liquefaction of silty sands the results from an experimental study on silty sands are presented and evaluated in view of the framework of critical state or steady state soil mechanics drained and undrained compression tests were performed on nevada sand containing nonplastic silt the drained and undrained steady state lines diverged this divergence was caused by the tendency for static liquefaction at low pressures results from undrained tests with different initial void ratios produced different steady state lines unique steady state lines may therefore not always exist for silty sands denser specimens liquefied at low confining pressures while looser specimens at higher confining pressures showed stable behavior thus a unique relation between void ratio and confining pressure namely the steady state line may not represent the behavior of loose silty sands this occurs because silty sands exhibit reverse behavior characteristics more dilative behavior is observed with increasing confining pressure under undrained shearing load and deformation control testing was performed to evaluate the effect of strain rate compressibility was examined as an alternative measure of liquefaction potential

summary of collapsible behaviour of artificially structured loess in oedometer and triaxial wetting tests this paper summarizes experimental studies on wetting induced collapsibility in loess using single oedometer double oedometer and triaxial wetting tests artificially structural loess samples with interparticle bonding calcite caco3 and a large void ratio were tested in the laboratory to avoid sampling disturbance of natural loess the comparison between the single and double oedometer tests confirms that the wetting induced deformation is independent of the sequence of wetting and loading the conventional triaxial apparatus was enhanced for investigating the collapse deformation in response to different water content increments when subjected to different stress levels the wetting induced strain subjected to high confining pressure develops in two steps it increases with increasing water content and reaches a relatively stable plateau and then increases rapidly again until a final stable state is reached the initial collapse surface was found by plotting the wetting induced strain vectors obser

geotechnical thresholds in the lanzhou loess of china abstract failure of cementation bonds leading to soil structure collapse and slope failure is a major problem encountered in loess slopes in the lanzhou region of china typical physical properties low plasticity indices short range bonds decrease in shear strength upon saturation show little variation throughout the loess strata however important variations in the modes of failure and collapse potential exist which are related to varying thresholds of cementation bond failure and packing transformations when geotechnical thresholds are exceeded metastable loess can rapidly transform from an open to close particle packing a phenomenon enhanced by leaching processes and degradation of cementation bonds geotechnical parameters from laboratory and in situ tests provide an insight into the variation of cementation bond condition which in turn provides enhanced understanding of processes underlying slope instability development and the triggering of catastrophic mass movements in loess

changes in tensile strength and microstructure of loess due to vibration abstract loess soils typically have an open and metastable structure humidification and vibration can modify their microstructure and thus influence their mechanical behavior in the present study to investigate the influence of train vibration on the tensile strength behavior of loess the tensile tests were performed on loess specimens that had been vibrated at a low amplitude for a long period using a modified horizontal extensograph in addition the microstructures of vibrated and non vibrated loess specimens before and after the tensile tests were characterized changes in the loess microstructure due to vibration and that in the tensile test were analyzed the results show that the relationship between uniaxial tensile strength and water content in soil specimen could be represented using a power function the axial displacement at failure varies at the same manner as tensile strength with respect to water content in comparison to intact loess occurrence of less clay bridges and clay buttresses between aggregates or coarse particles is identified in the disturbed specimens while aggregates are seen to be a very little more loose in vibrated specimens after the tensile tests than that before the tensile tests this indicates that vibration reduces the tension resistance and ductility of loess soil structure which could be attributed to loss of bonding strength as a result of breakage of clay cementations and disintegration of aggregates in the tensile test the soil structure goes through two distinct phases of change i e stretching phase and cracking phase in the stretching phase the tensile deformations take place throughout the specimen without altering the contacts between soil particles significantly in the cracking phase weak cementations fail to resist tensile deformation and suffer from breakage once a through crack is developed the specimen breaks in two leading to a catastrophic drop of tensile stress

collapsibility and deformation characteristics of deep seated loess in china abstract lin z g and wang s j 1988 collapsibility and deformation characteristics of deep seated loess in china eng geol 25 271 282 as part of a comprehensive research program laboratory tests were conducted on samples of deep seated loess from different locations of the loessial regions of northern china including shaanxi gansu shanxi and honan provinces the information thus acquired on some aspects of the engineering properties of the samples such as the unit collapse pressure relationships the initial collapse pressure versus the preconsolidation pressure and deformation pressure characteristics is interesting and may prove useful to geotechnical engineers who work on projects on water poor plateaux or high river terraces in loessial regions throughout the world

granites and early proterozoic crustal evolution in sweden evidence from smnd upb and o isotope systematics abstract u pb zircon and whole rock rb sr sm nd and o isotope results are reported for granitoids from three proterozoic provinces in sweden that represent different crustal environments the radiometric ages span the period 1 89 1 65 ga and record events ranging from original igneous crystallisation to late metamorphic resetting these events occurred at different times in the crustal segments the o isotope ratios identify different crustal source materials for the granitoids the sm nd results indicate that the major crustal source components common to most of the granitoids formed shortly before 1 9 ga close in time to the formation of the earliest granitoids contributions from recycled archaean basement are minimal the geographically widespread occurrence of such crustal sources indicates that the period around 2 ga was of great importance for the growth of new continental crust in sweden

microstructure and soil water retention behavior of compacted and intact silt loess abstract there are an increasing number of mega engineering projects of removing the top of hills to fill in the valley for new land creation in the loess plateau of china which significantly changes the hydrological and geological equilibrium state of the site the formation of a new hydrological equilibrium state is associated with the water movement in the compacted and intact loess layers most disasters occurring in the loess area are related to water the soil water retention curve swrc is the key to the implementation of unsaturated soil mechanics in engineering practice and is required to numerically model the movement of water in the soil in this study the swrcs and microstructure of intact and compacted specimens from lanzhou and yan an two typical cities that have new land creation projects are investigated the swrc is obtained using the filter paper method the mercury intrusion porosimetry mip and scanning electron microscope sem techniques are used to explore the microstructure the results highlight that the intact loess has a higher air occlusion value aov and a similar slope of swrc in the transition zone compared with the remolded specimens that compacted at the natural water content the normalized swrc i e degree of saturation versus suction avo of the intact specimen is approximately the same as the remolded specimens compacted as the natural water content the difference in the microstructure between intact and compacted specimens originates from different existing states of the clay particles and further contributes to the variation of the swrc

the geochemistry of early proterozoic metavolcanic rocks hosting massive sulphide deposits in the skellefte district northern sweden the skellefte district an early proterozoic massive sulphide ore province in northern sweden contains a well preserved volcano sedimentary rock association referred to as the skellefte group metamorphosed predominantly under low grade conditions the volcanic rocks in the lower part of the succession host the massive sulphide deposits and comprise a bimodal sequence composed of a calc alkaline group of felsic rocks and a tholeiitic group of mafic rocks displaying a basaltic to andesitic composition derivation of the felsic rocks by fractional crystallization from the mafic rocks is not supported by the geochemical data application of tectonic environment discriminant diagrams involving the elements ti zr y and cr suggests that these rocks were deposited in a volcanic arc setting stratigraphically above the volcanic rocks hosting the massive sulphide deposits there follows a sequence of metamorphosed greywackes and pelitic sediments with intercalation of primitive basaltic to ultrabasic volcanic and high level intrusive rocks the volcanic rocks show geochemical similarities to both archaean basaltic komatiites and phanerozoic boninites the primitive nature of these rocks present difficulties in assessing their palaeotectonic setting a volcanic arc or transition to an inter or back arc rift situation is suggested

origin of continental crust of 1 9 1 7 ga age nd isotopes in the svecofennian orogenic terrains of sweden initial nd isotopic ratios are reported for 57 samples representing all crustal components in the central and southern parts of the 1 9 1 7 ga old svecofennian orogenic terrains of sweden and the 1 8 1 7 ga old transscandinavian granite porphyry belt transscandinavian igneous belt u pb zircon ages are determined where the magmatic ages were not sufficiently constrained the nd isotopic results show that there are no archaean crustal blocks within the studied 1 9 1 7 ga old crustal segment this is consistent with results from finland the main input of recycled archaean crust to the svecofennian was in the form of sediments which are concentrated in the central svecofennian subprovince of north central sweden this is consistent with the vicinity of this subprovince to the archaean craton of the baltic shield these turbidite sediments contain up to 40 archaean material but s type granitoids associated with them have a smaller archaean component around 20 most of the quantitatively predominant i type granitoids and volcanics as well as all the basaltic rocks studied have nd from 1 to 3 and consist of 90 material newly derived from the mantle 1 9 1 7 ga ago we argue that the archaean material was introduced in the form of sediments but we cannot distinguish between pelagic sediments delivered on subducting oceanic crust and turbidite accumulations like the ones seen in north central sweden in either case an overall 15 archaean contribution for the swedish svecofennian was reasonably well homogenized with mantle derived magmatic products for this to occur an active near surface tectonic environment such as a complex of subduction zones must have been necessary

geotechnical characterization and collapsibility of a natural dispersive loess abstract during preliminary investigation phase of the national chabahar zahedan railway line serious geotechnical problems including non uniform settlements tensile cracks and local collapse were reported in parts of the path near the coastline a follow up field investigation revealed that the in situ soil at construction site has a metastable structure being sensitive to saturation and loading therefore a comprehensive series of physical chemical electro chemical and geotechnical tests were conducted to classify and characterize the soil properties and behavior in its natural state the natural soil was classified as a clayey loess with moderately dispersive to dispersive characteristics given its significant collapse potential the soil was assigned into the category with severe trouble for construction purposes importantly our tests revealed that a threefold reduction in pore water salinity results in 4 rise in collapse potential of similar specimens reduction in salt concentration increases the thickness of diffuse double layer and hence collapsibility in addition strain softening shear behavior was observed for elevated confining stresses under undrained triaxial stress state in fact this brittle type failure mechanism associated with continuous generation of pore water pressure is undesirable as catastrophic failures could happen with no advance warning

post svecokarelian andinotype evolution in central sweden granitoids and associated volcanics postorogenic in relation to the svecokarelian orogeny constitute a belt in central sweden evidence presented in this paper suggest that the belt originated in an andinotype orogenic environment the inferred development of the belt was characterized by fracture controlled high level emplacement of batholiths in an ensialic setting voluminous venting of ignimbrites and formation of grabens through cauldron subsidence accompanied the recurrent intrusive activity block movements and episodes of burial metamorphism appear to have been prominent features throughout the history of the post svecokarelian belt

on the mechanics of structured sands to date the effect of structure on the behaviour of natural sands has focused almost exclusively on the component of bonding and the effect of fabric has been largely overlooked the paper describes a detailed investigation of the behaviour of two natural sands by means of triaxial testing over a wide range of pressures one material had bonding as the principal element of its structure and the other fabric following on from a paper of cuccovillo and coop which examined the influence of the two structural elements on the small strain stiffness the current paper develops a new framework for the yielding and large strain behaviour it is suggested that structure should be considered as an element of the nature of a sand in addition to properties such as mineralogy particle shape and grading the resulting framework is then capable of encompassing the patterns of behaviour seen for both bonding and fabric dominated sands while bonding results in a cohesive mode of shearing it is demonstrated that when

the mechanics of a saturated silty loess and implications for landslides the results from an intensive experimental investigation on a loess that was retrieved from a typical silty loess zone in the north western chinese loess plateau are presented and interpreted triaxial and oedometer tests were performed on intact and reconstituted samples in a saturated condition the soil behavior was found to be strongly affected by structure the compression paths of the intact samples crossed the intrinsic compression line of the reconstituted soil and reached well defined gross yield points after which the compression paths converged towards the intrinsic compression lines two critical state lines were defined for the intact and reconstituted soils in the volumetric plane as a result of a robust element of natural structure comparisons were made with a structured clayey loess retrieved from the south eastern loess plateau it was found that the effects of structure on the behavior of the two loess soils are similar though they are very different in natural properties this indicates that their natural structures might have experienced similar forming processes perhaps related to their common origin catastrophic flowslides commonly occur in the study area and the patterns of behavior observed in the laboratory tests may create some new insights into mechanisms of landslide initiation and subsequent movement as discussed in the study

influence of early diagenesis on geotechnical properties of clay sediments romania black sea abstract the geotechnical properties of clay sediments were investigated using laboratory and in situ measurements as part of the geohazard assessment in the romanian sector of the black sea affected by landslides and seafloor deformation features the sediments were characterized as predominantly high plastic silty clay of high compressibility low undrained shear strength low cohesion and moderate sensitivity a shallow increase in shear strength exceeding the general trend could have been reconciled with evidence for the precipitation of iron sulfides and calcium carbonates related to early diagenetic reactions of sulfate reduction e g cryptic sulfur cycle and anaerobic oxidation of methane comparison of the compression behaviour of natural and reconstituted samples indicated that precipitation of these materials at particle contacts produced cementation the analysis of deeper sediments sharing similar geochemical properties illustrated that the early precipitation of even low quantity of sulfur and carbonate cements allowed clays to develop sufficient strength to preserve an abnormal high water content even under tens of meters burial depth because this cementation process was observed to be associated with an enhanced sensitivity and a strain softening response to undrained shearing it was concluded that such early diagenesis should be considered as a key environmental factor leading to weak layer formation that may influence the susceptibility of seafloor to failure

development and evolution of loess vertical joints on the chinese loess plateau at different spatiotemporal scales abstract the vertical joints of aeolian loess are ubiquitous on the chinese loess plateau clp the distribution variability of which mainly depends on the differences in structural characteristics of loess water drivers e g rainfall or irrigation loess strata e g sedimentary depth and microtopography this study conducted extensive field investigation and experiments to enhance the understanding of morphologies cross scale transformation mechanism and structural bases of loess vertical joints lvjs moreover the development and evolution processes of lvjs were refined by considering loess sedimentary dynamics results show that 1 lvjs are the product of diagenesis in loess strata during loess historical sedimentary process 2 the pore concentration zones and vertical tubular channels in loess are the structural bases of forming original vertical joints ovjs at the micro mesoscale which is supported by the results from the three dimensional computing tomography ct scanning and scanning electron microscopy sem tests and 3 the morphologies of lvjs vary with the microtopography at different spatiotemporal scales and is characterized by the cross scale transformation mechanism i e that they could transform up i e an expansion behavior or down i e a degradation behavior at the micro meso and sub macro scales under the influences of dry wet cycles loess pile thickening and exogenic forces besides we also propose the development and evolution mechanism of ovjs in loess from the viewpoint of unsaturated loess which would help understand the loess anisotropic genesis structural evolution preferential flow and the occurrence of geohazards such as landslides and soil erosion

laboratory study on soil behavior in loess slope subjected to infiltration abstract in recent years heifangtai plateau in gansu province china has received significant attention as a loess region in which landslides frequently occur this study aims to examine the soil behavior and failure mechanism s of loess slopes subjected to water infiltration high quality samples were retrieved behind the failure plane of a landslide in heifangtai three sets of stress path tests were conducted to mimic the process of loess slope failures these tests include undrained compression on anisotropically consolidated saturated samples drained shear by decreasing mean effective stress at constant axial load on saturated samples and wetting by decreasing matric suction at constant axial load on unsaturated samples loess behavior was evaluated in terms of shear strength deformation upon shearing critical state state parameter and soil water characteristic curve three major observations were drawn from the test results first the anisotropically consolidated saturated loess exhibits a noticeable strain softening behavior upon undrained compression the peak shear strength is mobilized at less than 1 axial strain the ultimate shear strength is only 20 30 of the peak value second when subjected to shear by decreasing mean effective stress at constant axial load the saturated loess exhibits sudden failure when the confining stress is low at higher stresses the soil exhibits progressive failure third unsaturated loess deforms progressively when subjected to a reduction in matric suction i e wetting at constant axial load the failure mechanisms of the loess slopes are discussed based on the experimental findings

the structure degradation of a silty loess induced by long term water seepage abstract loess is a typical silt sized aeolian soil that is widely deposited and possesses a fragile soil structure susceptible to collapse upon wetting the instability of shallow loess slopes is well documented but deeper failures triggered by rainfall and irrigation can also occur in the case of long term seepage clay particles and salts have been observed to leach out of the loess slopes this paper presents a systematic laboratory study of the effects of water conditions on the mechanical behaviour of silty loess with isotropic compression and bender element tests carried out on natural and reconstituted loess recovered at 10 m depth from a site in china the results show that saturation causes reduction in both the compression yield stress and small strain stiffness of the soil and that after being exposed to seepage they decrease further the possible mechanism of structure degradation is investigated by means of microscopic and chemical analyses and it is found that seepage will cause the pore ions concentration to reduce with a loss of clay mineral bonding strength resulting in the detachment of silt particles from aggregates this work highlights the importance of monitoring the water outflow in the field at the loess slope edge since it may causes large deformation in the long term

geochemical characteristics of granites associated with proterozoic molybdenite mineralization in northern sweden abstract proterozoic molybdenite occurrences in northern sweden are associated with small plutons of intrusive character located in supracrustal belts whereas large granite areas are barren in this study 152 samples of granites associated with molybdenite mineralization mineralized aplites granites not known to be associated with molybdenite occurrences but located in supracrustal belts and granites from the large granite areas have been analysed for major elements and the selected trace elements mo sn be ba rb sr cu zn zr v y nb f cl and s the study showed that major element geochemistry and modal composition are not useful for distinguishing between potentially molybdenite mineralizing and barren granites in northern sweden enriched contents of sn be y rb and f are most useful for identifying ore associated granites in the supracrustal belts the granites from the large granite areas have very low contents of sn mo be nb y f cl and s it is proposed that the granites associated with molybdenite occurrences were probably generated by partial melting of earlier igneous rocks or they may be of subcrustal origin the large granite bodies originated by partial melting of archean continental crust

geological geochemical and geochronological evidence for a new palaeoproterozoic terrane in southeastern sweden the geological and geochronological relationships between a rhyolite belonging to the transscandinavian igneous belt tib and an intrusive suite the backaby intrusion southeast sweden have been investigated by means of bedrock mapping geochemistry and radiometric age determinations u pb on zircons field relations suggest that the rhyolite rests unconformably on the backaby intrusion which previously has been correlated with 1 9 ga granitoids within the svecofennian domain the rhyolite yielded an age of 1800 8 ma and a tonalite belonging to the backaby intrusion basement yielded an age of 1834 3 ma the age of the rhyolite is slightly older 10 15 ma than adjacent granitoids belonging to the transscandinavian igneous belt and is considered as the earliest magmatic expression of tib in the area the age and the geochemical trends for the backaby intrusion is significantly different from that of the surrounding tib granitoids and indicate a rock forming event at about 1830 1840 ma in southeastern sweden represented by the oskarshamn jonkoping belt this event is significantly younger than the older svecofennian rocks within the svecofennian domain proper indicating a hitherto unidentified geological terrane in southeastern sweden

formation and development of the structure of collapsing loess in china abstract gao g 1988 formation and development of the structure of collapsing loess in china eng geol 25 235 245 it is well known that in china the regional variations in microstructure of loess are in phase with the overall tendency for collapsibility gradually decreasing from the northwest to the southeast these differences are consistent with variations in climatic conditions this indicates that the structure of collapsing loess is closely related to the climatic condition and geological environment based on the microstructure analyses it can be assumed that the formation and development of the structure of collapsing loess in china has undergone five stages the loessization stage the formation stage the development stage the degeneration stage and the clayization stage the five stages of loess regularly exist in different regions of the loess plateau this also shows that under the modern climatic condition the collapsing loess in the northwest of the loess plateau in china is still developing however the feature of collapsing loess is gradually disappearing in the southeast of the loess plateau

stochastic fracture geometry modeling in 3 d including validations for a part of arrowhead east tunnel california usa abstract eight hundred and fifty nine fractures of a gneissic rock mass were mapped using 16 scanlines placed on steep rock exposures that were within 300 m of a tunnel alignment before the tunnel excavation these data were analyzed using the software package fracntwk to find the number of fracture sets that exist in the rock mass 3 d fracture frequency for each set and the probability distributions of orientation trace length fracture size in three dimensions 3 d and spacing for each of the fracture sets in obtaining these distributions corrections were applied for sampling biases associated with orientation trace length size and spacing developed stochastic 3 d fracture network for the rock mass was validated by comparing statistical properties of observed fracture traces on the scanlines with the predicted fracture traces on similar scanlines the one dimensional 1 d fracture frequency of the rock mass in all directions in 3 d was calculated and is presented in terms of a stereographic plot the 1 d fracture frequency along the tunnel alignment direction was predicted to be about 6 5 fractures m before the tunnel excavation this prediction was found to be in excellent agreement with the observed values obtained about 1 year later during the tunnel excavation this was another validation conducted for the developed 3 d fracture network

the mineral chemistry of hydrothermally altered and metamorphosed wall rocks at the stollberg fe pb zn mn ag deposit bergslagen sweden the c 1 9 ga old stollberg sulphide and mnrich skarn iron ores and sulphide ores in bergslagen south central sweden are hosted by hydrothermally altered and metamorphosed felsic volcanic and volcaniclastic rocks the ores are underlain by comformable alteration zones characterized by albite gedrite quartz and biotite muscovite plagioclase k feldspar quartz garnet assemblages the present mineralogies are interpreted as medium grade metamorphic equivalents to the original alteration mineral assemblages pt conditions during prograde regional metamorphism are semiquantatively determined to be 510 to 560 c at approximately 3 kbar with increasing modal content of gedrite and biotite in the alteration zones the mg fe ratios and xmg s in octahedral positions of these minerals also increase in the gedrite bearing strata whole rock mg fe ratios remain constant whereas in the biotite rich unit the wholerock mg fe trend is parallel to that of the biotites

irrigation induced loess flow failure in heifangtai platform north west china because the construction of dams and hydro electric power stations of liujiaxia and yanguoxia across the yellow river in west gansu province north west china inhabitants in the reservoir areas were resettled in heifangtai loess platform irrigation thus started in 1968 perched water table was significantly raised and resulted in many loess flow failures in the past 30 years this type of landslide was often featured by long runout distance high speed and recurrence laboratory tests along icu and csd stress paths were performed it is shown that the loess has a strong strain softening behavior and instability can occur in drained condition before undrained liquefaction the failure mechanism of loess flow can be interpreted as the following process with increasing perched water table collapse in loess was first triggered in drained condition and led to undrained loading to adjacent soil in the lower saturated part of the loess platform under gravity loading applied by upper dry loess undrained flow failure mobilized eventually

jorn an early proterozoic intrusive complex in a volcanic arc environment north sweden abstract the jorn complex is an early svecokarelian granitoid suite intruded into a volcanic arc environment on the southern margin of a major proterozoic continental area both the complex and its country rocks have been affected by hydrothermal alteration and low grade regional metamorphism four phases can be distinguished on geological chemical and geophysical criteria in particular a heterogeneous calcic outer zone and a more evolved central diapir the rock types vary from granodiorite to granite and have major and trace element abundances similar to those phanerozoic subduction related granitoids from relatively immature volcanic arcs zircon populations from the different phases are rather heterogeneous but do not show significant differences in u distribution or u pb age between the phases while pooled u pb data 13 points give an upper intercept of 1890 7 8 ma a two stage model assuming an age difference between cores and rims gives a more probable crystallisation age of 1876 2 ma with significant lead loss at 1720 ma and 410 ma epsilon nd values range from 1 8 to 3 2 indicating that the source material for the jorn complex was derived from an lree depleted mantle with a small contribution of older crustal material and had a relatively short crustal residence period metaluminous compositions and oxygen isotope ratios suggest non pelitic sources the jorn complex probably originated as a series of subduction related melts of basic to intermediate composition which underwent varying degrees of subsequent differentiation and secondary alteration

undrained shear behavior of loess saturated with different concentrations of sodium chloride solution abstract a series of ring shear tests was conducted on saturated loess to investigate the effects of nacl concentration in pore water and desalinization on the shear behavior under undrained conditions the loess samples were taken from the ground surface of a frequently active landslide in china were saturated by de aired distilled water with different concentrations of nacl and then were sheared undrained after that the samples were retrieved remolded re set into the shear box and re saturated by passing through de aired distilled water such that the samples were desalinized and then were sheared undrained again through comparing the undrained shear behavior the effects of nacl in the pore water and desalinization on the undrained shear behavior of loess were examined the results showed that the variation of nacl concentration in pore water can strongly affect the shear behavior of saturated loess both the peak shear strength and steady state strength increased with increase of nacl concentration until a certain value after which they decreased with further increase of nacl concentration meanwhile the peak shear strength and steady state strength of the desalinized samples recovered to those of the original sample hence the effects of salinization are reversible these findings may be of practical importance to better understand the repeated occurrence of some irrigation induced loess landslides in china

liquefaction susceptibility criteria for silts and clays new liquefaction susceptibility criteria for saturated silts and clays are presented that are based on the mechanics of their stress strain behavior and which provide improved guidance for selecting engineering procedures for estimating potential strains and strength loss during seismic loading monotonic and cyclic undrained loading test data for silts and clays show that they transition over a fairly narrow range of plasticity indices pi from soils that behave more fundamentally like sands sand like behavior to soils that behave more fundamentally like clays clay like behavior with the distinction having a direct correspondence to the type of engineering procedures that are best suited to evaluating their seismic behavior it is recommended that the term liquefaction be reserved for describing the development of significant strains or strength loss in fine grained soils exhibiting sand like behavior whereas the term cyclic softening failure be used to describe similar phenomena in fine grained soils exhibiting clay like behavior for practical purposes clay like behavior can be expected for fine grained soils that have pi 7 although a slightly lower transition point for soils with a cl ml classification perhaps pi 5 or 6 would be equally consistent with the available data issues related to the practical application of these criteria are discussed

pore pressure generation and fluidization in a loess landslide triggered by the 1920 haiyuan earthquake china a case study abstract during the 1920 haiyuan earthquake numerous catastrophic landslides were triggered in the loess area in northwest china we investigated in detail a large example of these landslides referred to as dangjiacha landslide in this paper this landslide originated from a slope of about 20 and the displaced soil mass traveled about 3200 m damming a valley we performed a field survey and found that standing water existed in the landslide area and the loess had high porosity we infer that it was the liquefaction of the water saturated loess layer rather than the suspension of silt in the pore air in the loess that caused the great mobility of this landslide to test this inference we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water the test results showed that the water saturated loess soil was highly susceptible to flow liquefaction failure fast shear tests on naturally air dried loess samples revealed that the generated pore air pressure was small under the undrained condition and no significant reduction in the shear resistance was observed implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large scale landslide