the stabilization of self organised leucogranite networks implications for melt segregation and far field melt transfer in the continental crust abstract net structured leucocratic vein systems are ubiquitous in high grade and migmatite terrains and are interpreted to represent interconnected former magma bearing structures that accommodated the migration of granitic magmas out of their anatectic source regions net structured leucogranite vein systems in high grade gneisses from the damara belt in namibia describe a size based hierarchy and spatial distribution that indicates self organisation of the magma transfer system the internal geometry and connectivity of the net structured leucogranites are controlled by variations in melt pressure whereas regional strains control the orientation of the leucogranites foliation parallel stromatic and shear band hosted granite veins accommodate transport at relatively low melt volumes and account for the metre scale segregation of melt close to the anatectic source during times of higher melt supply the formation of extensional fractures that cross cut stromatic and shear band hosted melt sheets at high angles is promoted extensional fracturing and associated dilatancy create gradients in magmastatic head that cause melt to be drained from pervasive stromatic and shear band hosted vein networks into spaced dilatant fractures this has the potential to initiate buoyancy driven far field melt transfer along suitably orientated extensional fractures as vertical dykes or self propagating hydrofractures our results suggest that melt transfer systems are able to adjust to variations in melt supply by forming conduits that accommodate varying melt volumes and will tend to develop towards a state of self organisation

low melt fraction connectivity of granitic and tonalitic melts in a mafic crustal rock at 800 c and 1 gpa in the absence of an externally applied stress the segregation of small amounts of granitic or tonalitic melts from their residual mafic crystals is possible only if the melt forms an interconnected network phase accordingly this research focuses on melt connectivity at low melt fraction 4 wt or 5 vol connectivity of granitic and tonalitic melts in amphibole rich rock was assessed by performing two types of piston cylinder experiments at 1 gpa and 800 c the first involved annealing samples that consisted of either alternating layers or homogeneous mixtures of calcic amphibole and metaluminous obsidian powder the second type of experiment involved creating diffusion couples here an upper cylinder of amphibole saturated granitic or tonalitic melt was placed against a lower cylinder consisting of an amphibole rich rock containing zero or a small melt granitic or tonalitic fraction the upper part of the diffusion couple was doped with emitter 151sm or 14c and functioned as an infinite melt reservoir the lower part of the diffusion couple was considered to be the host rock the experiments approached textural equilibrium which allowed us to characterize the wetting behaviour of the calcic amphibole by the hydrous silicic melt granitic or tonalitic these particular experiments also provided information concerning diffusive transport because the emitter could diffuse through the connected melt liquid in the amphibole rich rock the dihedral angle measurements show that melt connectivity was achieved this conclusion is based on the fact that the dihedral angles consistently yielded median apparent values of 53 58 for an amphibole rich rock granitic melt system and 46 48 for an amphibole rich rock tonalitic melt system however the frequency distribution of angles is found to be relatively broad the results of the diffusion couple experiments assessed using the radiographic technique complement the dihedral wetting angle measurements by showing that melt connectivity is achieved at a melt fraction less than 4wt 5 vol

age of amphibolitic metamorphism in the ophiolitic unit of the morais allochthon portugal implications for early hercynian orogenesis in the iberian massif structurally lower portions of the allochthonous morais complex are comprised of an ophiolitic unit exposed in two contrasting structural units separated by a ductile thrust fault the lower unit is dominated by variably foliated amphibolite whereas the upper unit is largely comprised of metaperidotite and metagabbro most of the ophiolitic unit has recrystallized synkinematically under amphibolite facies metamorphic conditions c 500 c and 5 kbar amphiboles formed during this metamorphism are typically magnesio hornblende an amphibole concentrate from the lower structural unit records a 39 ar 40 ar plateau age of 397 3 4 ma an amphibole concentrate from the upper structural unit displays an internally discordant 39 ar 40 ar age spectrum corresponding to a total gas age of 431 1 27 3 ma gas fractions evolved from each amphibole concentrate at intermediate and high experimental temperatures are characterized by similar apparent k ca ratios and yield well defined 36 ar 40 ar v 39 ar 40 ar isotope correlations which result in similar ages of 384 2 5 2 and 392 4 7 3 ma these are considered to be more reliable than the plateau ages and are interpreted as dating the last cooling through those temperatures required for intracrystalline retention of argon within constituent amphibole grains the associated tectonothermal event represented a first stage of hercynian orogenesis in the iberian massif it was probably related to oceanic closure and associated obduction of granulitic eclogitic massifs which at present structurally overlie the ophiolitic unit

petrology and ion microprobe u pb chronology applied to a metabasic intrusion in southern sweden a study on zircon formation during metamorphism and deformation the aker metabasite occupies a key position in a major tectonic lineament in southernmost sweden the protogine zone which coincides closely with the eastern boundary of the late mesoproterozoic sveconorwegian orogen of southwest scandinavia metamorphic reactions associated with the transformation from isotropic gabbro to foliated garnet amphibolite were identified from disequilibrium textures of which some involved release of zirconium zr and growth of metamorphic zircon ion microprobe dating of igneous zircon gave 1562 6 ma whereas metamorphic zircons yielded ages of 1437 21 1217 75 and 1006 68 ma the presence of baddeleyite pseudomorphs made up of saccharoidal zircon and a higher abundance of older rather than younger metamorphic zircons suggest redistribution of zr into new zircon first by the breakdown of baddeleyite zro2 and later by the consumption of igneous phases containing trace amounts of zr several generations of metamorphic zircon and the presence of 1 56 and 1 22 ga mafic intrusions along the protogine zone call for a complex tectonic history probably reaching back to at least similar to1 56 ga growth of metamorphic zircon at similar to1 44 ga may relate to a regional compressional event the wnw trending deformational structures on both sides of the protogine zone may possibly relate to that event the similar to1 22 ga metamorphic zircons are coeval with the emplacement of numerous granitic syenitic and mafic intrusions along and parallel to the protogine zone the age around 1 0 ga finally marks sveconorwegian metamorphism for which thermobarometry of the aker garnet amphibolite suggests 1000 1200 mpa at 600degreesc 630degreesc thereafter significant relative uplift of the rocks to the west of the protogine zone occurred on nearly vertical north south trending deformation zones less

partial melting of metagreywackes part ii compositions of minerals and melts a series of experiments on the fluid absent melting of a quartz rich aluminous metagreywacke has been carried out in this paper we report the chemical composition of the phases present in the experimental charges as determined by electron microprobe this analytical work includes biotite plagioclase orthopyroxene garnet cordierite hercynite staurolite gedrite oxide and glass over the range 100 1000 mpa 780 1025 c biotites are na and mg rich with ti contents increasing with temperature the compositions of plagioclase range from an17 to an35 with a significant orthoclase component and are always different from the starting minerals at high temperature plagioclase crystals correspond to ternary feldspars with or contents in the range 11 20 mol garnets are almandine pyrope grossular spessartine solid solutions with a regular and significant increase of the grossular content with pressure all glasses are silicic sio2 67 6 74 4 wt peraluminous and leucocratic feo mgo 0 9 2 9 wt with a bulk composition close to that of peraluminous leucogranites even for degrees of melting as high as 60 vol with increasing pressure sio2 contents decrease while k2o increases at any pressure the melt compositions are more potassic than the water saturated granitic minima the h2o contents estimated by mass balance are in the range 2 5 5 6 wt these values are higher than those predicted by thermodynamic models modal compositions were estimated by mass balance calculations and by image processing of the sem photographs the positions of the 20 to 70 isotects curves of equal proportion of melt have been located in the pressure temperature space between 100 mpa and 1000 mpa with increasing pressure the isotects shift toward lower temperature between 100 and 200 mpa then bend back toward higher temperature the melting interval increases with pressure the difference in temperature between the 20 and the 70 isotects is 40 c at 100 mpa and 150 c at 800 mpa the position of the isotects is interpreted in terms of both the solubility of water in the melt and the nature of the reactions involved in the melting process a comparison with other partial melting experiments suggests that pelites are the most fertile source rocks above 800 mpa the difference in fertility between pelites and greywackes decreases with decreasing pressure a review of the glass compositions obtained in experimental studies demonstrates that partial melting of fertile rock types in the crust greywackes pelites or orthogneisses produces only peraluminous leucogranites more mafic granitic compositions such as the various types of calk alkaline rocks or mafic s type rocks have never been obtained during partial melting experiments thus only peraluminous leucogranites may correspond to liquids directly formed by partial melting of metasediments other types of granites involve other components or processes such as restite unmixing from the source region and or interaction with mafic mantle derived materials

geomechanical behaviour of laminated weak coal mine roof strata and the implications for a ground reinforcement strategy this paper describes a component of the results from an arc spirt funded collaborative research project between unsw powercoal pty ltd and springvale coal pty ltd the research project was aimed at identifying strategies for appropriate ground control in particularly weak and soft roof strata in underground coal mining a field investigation was undertaken at angus place colliery in the western coalfield of new south wales the investigation incorporated a range of geotechnical instrumentation and was conducted over a period of time from the development face until the site was lost into the goaf of a retreating longwall panel this paper describes the outcomes from the field investigation together with a selection of supporting laboratory studies the paper also presents a number of alternative presentation modes for extensometry data the results clearly demonstrate the time and face proximity related influences on roof integrity and particularly demonstrated the distribution of deformation bed separation and strata failure into the roof and across the full span of the roadway together with reflection of this behaviour within the fully encapsulated roof bolt reinforcement system installed

experimental deformation of partially molten westerly granite under fluid absent conditions with implications for the extraction of granitic magmas the mechanical behavior of partially molten westerly granite was investigated in the temperature range 800 1100 c 250 mpa confining pressure by means of constant strain rate creep and stress relaxation tests the only water in the samples came from the breakdown of hydrous phases biotite minor chlorite and muscovite and alteration products of feldspars thus the amount of melt was controlled by the test temperature and ranged from 3 at 800 c to 50 at 1100 c over that temperature range strength decreased from 500 mpa to less than 1 mpa and a preliminary constitutive flow law for the partially molten rock was obtained to allow extrapolation to low strain rates the comparative viscosity of the melt alone was estimated at 950 and 1000 c from the distance it could be made to penetrate into a porous sand under a known pressure gradient under all conditions deformation of the matrix of solid grains was by brittle fracture only samples containing up to 10 vol melt failed with the formation of a shear fault zone at higher melt fractions melt filled pores collapsed by shear enhanced compaction squeezing the melt into axial cracks above 40 vol melt unfractured solid grains were carried about passively in the flowing liquid there was no evidence of a rheologically critical melt percentage in this system by analogy with the uniaxial compaction of water saturated soils a simple model is erected to describe a two stage process for the extraction of granitic melts from their protoliths with the aid of nonhydrostatic stress shear enhanced compaction is inferred to drive melt into a network of melt filled veins whereupon porous flow through the high permeability vein network allows rapid drainage of melt to higher crustal levels

engineering geology and ground collapse mechanism in the chengchao iron ore mine in china abstract the engineering geological and hydrogeological conditions in the eastern mining area of the chengchao iron mine are analyzed in detail the results are combined with the results of site investigations and in situ monitoring data allowing the characteristics of the ground surface collapse events to be summarized the mechanism by which ground surface collapse is induced by underground orebody extraction or de watering activity was then investigated the results show that the ground surface in the mining areas experienced three collapse processes karst collapse mixed collapse and mining induced collapse karst collapse sinkholes were found during the construction stage of the mine and are generally formed in the marble part of the marble granite contact zone these sinkholes show a bead on a string distribution and lines connecting their centers are consistent with the strike of the marble such sinkholes are mainly formed due to changes in the dynamic conditions of groundwater caused by de watering activity furthermore the development level of the collapse mainly depends on the location and scale of the karst caves within the marble mixed collapse occurs in the initial mining stage and mainly results from the combined effect of underground orebody excavation and de watering activity mining induced ground surface collapse pits mostly develop in the diorite and hornstone and generally show a zonal distribution along the strike of the orebodies from east to west mining induced collapse occurs in the form of chimney caving first a caved pipe is formed where the rock masses above the caved zone are highly fractured then the rock masses around the caved pipe gradually cave and finally a large caved zone is formed above the mined out area mixed collapse is of particular interest as it is a peculiar type of subsidence involving the superposition of collapse processes related to both mining and karst cavities and it can provide some instructive insight into the collapsing behavior of the ground surface

a study of strontium diffusion in k feldspar na k feldspar and anorthite using rutherford backscattering spectroscopy abstract sr chemical diffusion has been measured in orthoclase anorthoclase and anorthite under dry 1 atm conditions a strontium oxide aluminosilicate powder mixture was used as the source material with rutherford backscattering spectroscopy rbs used to measure diffusion profiles over the temperature range 725 1075 c the following arrhenius relations were obtained orthoclase normal to 001 d 5 97 10 0 0060 0 0030exp 67900 1600rtcm 2 s 1 measurements of diffusion perpendicular to 010 and 100 indicate little diffusional anisotropy in orthoclase anorthoclase normal to 010 d 4 51 10 1 358 5 6exp 89100 4800rt cm 2 s 1 normal to 001 d 2 25 10 2 1615 31exp 89300 4600rt cm 2 s 1 anorthite normal to 010 d 3 85 10 2 0 380 0 0039 exp 78800 5400rt cm 2 s 1 the correlation of sr uptake with a reduction of k and ca in orthoclase and anorthite respectively indicates that sr is exchanging with these species nuclear reaction analysis nra measurements of al in orthoclase suggests that the coupled exchange sr 2 al 3 k 1 si 4 is taking place as expected sr closure temperatures for feldspars calculated with the above parameters are relatively high compared to those of some other minerals e g biotite muscovite apatite however closure temperatures of feldspars may be significantly depressed if they are exsolved or twinned leading to small effective diffusion lengths feldspar crystals of millimeter size should retain 87 sr 86 sr ratios except when subjected to thermal events of extreme temperature or duration

melt segregation and magma interactions during crustal melting breaking out of the matrix abstract differentiation of the continental crust begins with its partial melting the products of crustal melting are silicic hydrous h2o undersaturated granitic liquids that are generated within matrices of residual crystals crustal differentiation requires that felsic magmas form and escape from these solid residua an important question is whether granitic magmas collect into large batches within or near their sources which then give rise to ascent or alternatively bleed out of the sources in smaller streams or pulses we demonstrate that the physical reality is closer to the second alternative and thus question the validity of the concepts of magma segregation and source fertility as they are sometimes visualised granitic plutons contain chemically distinct sub populations formed by source level entrainment of the peritectic assemblages into the melts rapid evacuation at source levels and high ascent rates protect the magmas from wall rock interactions during their tenure at source depths and during their ascent through cool upper crust the existence of different types of granites and hence of clearly defined chemically different magmas within plutons dictates that felsic magmas must separate efficiently from their anatectic sources and must ascend to the sites of their emplacement with minimal chemical interaction with crust through which the magma must move exposed deep crustal sections are typically lithologically diverse with the more fertile rocks commonly forming discrete layers surrounded by rocks with contrasting compositions if the melts were required to segregate and accumulate into large volumes within their hot sources especially by slow gravity driven melt percolation it is very likely that they would be substantially modified by reaction with diverse source rocks thus the processes mooted to occur in melting assimilation storage and homogenisation mash or deep crustal hot dch zones would act to erase original compositional heterogeneities and produce larger batches of more homogeneous magma perhaps carrying evidence of extensive magma mixing from various lines of evidence we conclude that mash and dch zones may not exist and even if they do they cannot form the sources of most granitic magmas the intrinsic heterogeneity in crustal source rocks the likely occurrence of peritectic assemblage entrainment and the inefficiency of magma mixing decree that granitic rocks will retain source inherited chemical and isotopic heterogeneities rapid semi continuous and disequilibrium withdrawal of small magma batches from source rocks means that elements of whole rock trace element chemistry and accessory mineral chemistry will be decoupled from major element variations this also means that a large source with low nominal fertility due to low hydrous mineral content for example could still produce a substantial granitic pluton by additions of individually small increments of magma

selective entrainment of peritectic garnet into s type granitic magmas evidence from archaean mid crustal anatectites entrainment of restite is commonly invoked to explain both the origin of relatively mafic granites and granodiorites as well as the chemical connection between granite magmas and their sources this concept has become linked to models for magma migration out of the source as restite entrainment is considered to take place when diatexitic sources mobilise en masse this is at odds with the common occurrence of relatively mafic granites as high level intrusions in the crust or their eruptive equivalents that must have formed from markedly water undersaturated magmas that ascended through narrow conduits we investigate pelitic migmatites from the mkhondo valley metamorphic suite mvms in swaziland where a mid crustal heating event produced metatexitic migmatites with minimal post anatectic recrystallisation in these rocks all the garnet is peritectic having arisen through biotite fluid absent melting which produced garnet poikiloblasts characterised by inclusions of melt quartz and biotite leucosomes that represent sites of melt transfer carry similar smaller typically 1 mm entrained garnet poikiloblasts which were capable of amalgamating to form larger composite grains in anatectic structures where melt was present for longer entrained garnet was extensively recrystallised via a dissolution precipitation process to adopt a more magmatic character the peritectic garnet in the pelitic source appears to have grown out of equilibrium with feldspar and hree rich accessory phases while the recrystallised garnet in the larger melt filled structures became progressively better equilibrated with these minerals thus peritectic garnet in the source grew sufficiently rapidly to prevent trace element equilibrium with the bulk rock composition and concurrent rapid magma segregation prevented the development of diatexitic source conditions the segregated magma consisted of melt the peritectic assemblage principally garnet and the accessory minerals monazite and zircon these rocks illustrate that mafic granites may arise purely as mixtures of melt and the peritectic assemblage produced by the incongruent melting reaction importantly under the circumstances which produced the mvms anatectites peritectic garnet is entrained as 1 mm poikiloblasts demonstrating how mafic granitic magmas can migrate out of the source without the source becoming diatexitic

kinematics of a major fan like structure in the eastern part of the sveconorwegian orogen baltic shield south central sweden abstract the n s trending so called protogine zone in the baltic shield of south central sweden is usually considered to mark a tectonic boundary between the rocks of the transscandinavian igneous belt tib in the east and the sveconorwegian orogen in the west detailed structural mapping in the karlskoga kristinehamn area has shown that an anastomosing network of ductile deformation zones with generally n s strike extends ca 40 km east of the traditional protogine zone furthermore the western boundary of this ductile deformation and the tib is not constrained in the kristinehamn area reconnaissance studies indicate that they both extend westwards towards the so called mylonite zone it is suggested that the eastern limit of the sveconorwegian orogen is located some 40 km east of the present boundary and that the protogine zone concept is obsolete the term sveconorwegian frontal deformation zone sfdz is proposed as a more appropriate alternative in southern sweden south of lake vattern and to correspond to a younger set of oblique ductile deformation zones with reverse and right lateral components of movement in the easternmost part of the orogen farther to the north ductile deformation zones older than the sfdz in the karlskoga kristinehamn area display a fan like geometry in an e w cross section with steep westerly dips in the eastern part of the section vertical dips farther west and moderate easterly dips in the western part of the section kinematic analysis indicates that dip slip movements predominate with a consistent top to the east sense of movement across the entire fan like structure in their present orientation deformation zones are characterized by reverse movements in the eastern part and normal movements in the western part of the structure between kristinehamn and the mylonite zone the main foliation is gently dipping to subhorizontal indicating that the regional structure is strongly asymmetric and that the fan like structure occurs close to the foreland of the orogen deformation zones are spaced to semi penetrative in the eastern part of the fan like structure whereas the deformation is more or less penetrative and the tib rocks are transformed to orthogneisses west of kristinehamn this east to west increase in bulk strain is in accordance with an increase in syn deformational metamorphic grade across the structure younger ductile deformation zones belonging to the sfdz are responsible for a major change in orientation of the older deformation zones in the easternmost part of the structure the fan like structure is best explained by models involving the interference of two separate tectonic events deformation occurred after 1 57 ga and prior to deposition of neoproterozoic and younger cover sedimentary rocks it is not yet clear whether the initial phase of deformation early sveconorwegian or older was related to the build up of an imbricate thrust stack in a compressional regime as favoured here or to regional e w extension the younger deformation phase was related to rotation of these older structures into the compressional late sveconorwegian sfdz

hangingwall surface subsidence at the kiirunavaara mine sweden large scale surface subsidence has been experienced at the kiirunavaara mine since sublevel caving was implemented as a mining method surface disturbances are affecting part of the city of kiruna the railway and the power station continuous and discontinuous subsidences characterize the hangingwall deformation which is periodically monitored using surveying techniques and mapping of surface cracks a historic review of subsidence prognoses has been carried out and the results compared with the actual condition of the hangingwall the review showed discrepancies between different prognoses in addition limit equilibrium analyses indicated that break angles flatten while the mining depth increases however this tendency is not clear in the field where break angles show a large dispersion of values by using surveying data two different analyses have been performed the time dependent movements of the hangingwall have been described using time displacement curves and strain analysis has been performed for different sections of the hangingwall three different stages of the time displacement behavior have been identified and described it has been concluded that extension strain can reach values which may damage civil structures before surface crack can be observed

linking deformation migmatite formation and zircon u pb geochronology in polymetamorphic orthogneisses sveconorwegian province sweden absolute ages of migmatization in the polymetamorphic parautochthonous basement of the sveconorwegian province sweden have been determined using u pb ion probe analysis of zircon domains that formed in leucosome of migmatitic orthogneisses migmatite zircon was formed by recrystallization whereas dissolution reprecipitation and neocrystallization were subordinate the recrystallized migmatite zircon was identified by comparison of zircon in mesosomes and leucosomes it is backscatter electron bright u rich 800 4400 ppm with low th u ratios generally 0 01 0 1 unzoned or oscillatory ghost zoned and occurs as up to 100 m thick rims with transitional contacts to cores of protolith zircon protolith ages of 1686 12 and 1668 11 ma were obtained from moderately resorbed igneous zircon crystals generally th u 0 5 1 5 u 300 ppm in mesosomes protolith zircon is also present as resorbed cores in the leucosomes linkage of folding synchronous migmatization and formation of recrystallized zircon rims allowed direct dating of south vergent folding at 976 7 ma at a second locality similar recrystallized zircon rims in leucosome date pre sveconorwegian migmatization at 1425 7 ma an upper age bracket of 1394 12 ma for two overprinting phases of deformation upright folding along gently ssw plunging axes and stretching in ese was set by zircon in a folded metagranitic dyke lower age brackets for these events were set at 952 7 and 946 8 ma by zircon in two crosscutting and undeformed granite pegmatite dykes together with previously published data the present results demonstrate i tectonometamorphic reworking during the hallandian orogenesis at 1 44 1 42 ga resulting in migmatization and formation of a coarse gneissic layering ii sveconorwegian continent continent collision at 0 98 0 96 ga involving a emplacement of an eclogite unit b regional high pressure granulite facies metamorphism c southvergent folding subhorizontal east west stretching and migmatization all of which caused overprint or transposition of older mesoproterozoic and sveconorwegian structures the sveconorwegian migmatization and folding took place during or shortly after the emplacement of sveconorwegian eclogite and is interpreted as a result of north south shortening synchronous with east west extension and unroofing during late stages of the continent continent collision

in situ monitoring and analysis of the mining induced deep ground movement in a metal mine abstract an extra deep multiple point borehole extensometer applicable up to 300 m depth of cover is introduced for the deformation monitoring of the deep rock masses i e the rock mass below the ground surface in the eastern area of jinshandian iron ore mine and the in situ monitoring results collected over eight years are analysed combined with the deformation monitoring results on the ground surface collected by using a global positioning system gps level monitoring technique and a three dimensional laser scanning system leica hds 880 the ground movement mechanism of the deep rock masses induced by underground mining is investigated results show that the extra deep multiple point borehole extensometer can capture the deformation information pertaining to deep rock masses in metal mines with complex geological conditions such as jinshandian iron ore mine the moment that the deformation of the monitoring point starts to increase significantly can be used to determine whether the major deformation has transferred to the deep rock mass at the monitoring points or not the monitoring results from such critical moments indicate that the major deformation of the overburden strata gradually develops from the lower part to the upper part consistent with the results from a physical modelling experiment in jingshandian iron ore mine the second caving of the deep rock masses reaches the ground surface above the centre of the mined out area and then causes the ground collapse under the combined effect of the underground mining in jinshandian iron ore mine and the remaining private mined out areas large scale ground surface collapses and cracks can be observed in mining affected areas the deep rock masses surrounding the mined out areas are in a state of global deformation and the boundary line of the deep break zone is a fold line currently the rock masses in the major deformation zone move downwards under gravity on the shear surfaces in jingshandian iron ore mine

the deformation history of the eastern part of the southwest swedish gneiss belt abstract the deformation history of the eastern part of the sw swedish gneiss belt has been investigated regional events more than c 1700 ma are identified as d1 d2 more than c 1400 ma as d3 less than c 1130 ma as d4 and more than c 900 ma as d5 d7 thus the d4 d7 events are considered to be sveconorwegian a common deformation history is suggested for southwestern sweden gradational changes in lithology from west to east are apparently associated with different tectonic styles and intensity of strain the principle deformation of the protogine zone of central sweden is suggested to be d4 the mylonite zone of western sweden appears to have been initiated before d3 the smaland varmland granitoid belt c 1700 ma is geneally considered as early postorogenic in respect to the svecokarelian orogeny because it has been influenced by the d3 event it represents a link between svecokarelian rocks and the sw swedish gneisses

tectonothermal evolution of high alumina rocks within the protogine zone southern sweden the protogine zone comprises a system of anastomosing deformation zones which approximately parallel the eastern boundary of the sveconorwegian 1200 900 ma province in south west sweden ages of granulite facies metamorphism in the sveconorwegian province require exhumation from c 30 to 35 km crustal depths after 920 880 ma 40ar 39 ar cooling ages are presented for muscovite from high alumina rocks formed by hydrothermal leaching associated with the protogine zone growth of fabric defining minerals was associated with a ductile deformational event muscovite from these rocks cooled below argon retention temperatures c 375 25 c at c 965 955 ma muscovite from granofels in zones of intense alteration indicates that temperatures 375 25 c were maintained until c 940 ma textural relations of al2sio5 polymorphs and chloritoid suggest that dated fabrics formed during exhumation the process of exhumation brittle overprint on ductile structures and hydrothermal activity along faults within the protogine zone tentatively are interpreted as the peripheral effects of initial neoproterozoic exhumation of the granulite region of south western sweden muscovite in phyllonites associated with the sveconorwegian thrust system cooled below argon retention temperatures at c 927 ma exhumation associated with this cooling could have been related to extension and onset of brittle ductile deformation superimposed on sveconorwegian contraction

granitic magma transport by fracture propagation granitic magmas commonly ascend tens of kilometres from their source terranes to upper crustal emplacement levels or to the earth s surface apart from its obvious bearing on the interpretation of the geology and geochemistry of felsic igneous rocks the magma ascent mechanism critically affects any modelling of the metamorphic evolution of the upper lithosphere as well as its rheology we propose that in general granitic magmas ascend via propagating fractures as dykes in extremely short time periods long distance diapiric transport of granitoid magmas through crustal sections is not viable on thermal or mechanical grounds and there is an apparent total absence of field evidence for diapiric rise of such magmas even in supposed type localities neither the shapes nor internal or external characteristics of granitic plutons necessarily reveal anything about the transport of their precursor magmas these are purely arrival phenomena dictated by local structure kinematics and stress states based on existing numerical treatments of the problem we show that granitic magmas are apparently sufficiently inviscid to travel through fractures to high crustal levels without suffering thermal death by freezing for example a 2000 km3 granitic batholith can be inflated by a 1 km 3m 20 km deep dyke system in less than 900 years the model proposed has numerous far reaching petrological and rheological consequences some of which are outlined

stability of underground mine development intersections during the life of a mine plan abstract the stability of mine developments is of utmost importance during the planned period of production or the life of a mine plan many canadian underground mines use transverse stoping with delayed backfill to extract tabular ore deposits these methods require access to the orebody through a number of sill drives and cross cuts which link the orezone to the haulage drift hence creating intersections on multiple levels this paper presents the results of a study on the stability of mine development intersections at garson mine of vale in sudbury on canada multi point borehole extensometers mpbx are used to monitor the rock deformations of an intersection as mining activities progress the monitoring results are used to calibrate a multi level flac3d numerical model which has been developed to assess the stability of the intersection it is shown that stope extraction causes a lateral shift to the intersection accompanied by high shear stress in the roof it is also shown that same level mining has stronger influence on the stability of the intersection than lower level mining

late orogenic extension in mountain belts insights from the basin and range and the late paleozoic variscan belt from two examples of orogenic domains some general mechanisms significant of late orogenic tectonic processes in mountain belts are characterized the basin and range province and the variscan belt in the french massif central have both suffered important compressional orogenic crustal thickening and the results of late orogenic processes can be observed in the field both areas are covered by deep seismic profiling providing constraints on the geometry of a crust which has been restored to a normal thickness late orogenic features from the two domains are compared at different scales and their tectonic significance for extension mechanisms is discussed at the scale of the orogenic domains the most prominent tectonic features are the metamorphic core complexes mcc which expose deformed rocks from the middle crust generally affected by high temperature low to medium pressure metamorphism partial melting and widespread granite emplacement in these mcc large scale extensional shear zones present an intense mylonitic deformation characterized by low dipping foliations and pervasive stretching lineations they show a complete evolution from early deep seated ductile deformation generally achieved under high temperature low to medium pressure metamorphism to a late shallow brittle stage characterized by cataclastic deformation the late detachment stage generally controls the development of asymmetrical extensional sedimentary basins filled by continental deposits two main geometries of mcc are defined that are characterized by differing geometry and kinematics of low angle shear zones in the first case two low angle shear zones with opposite vergence develop along the flanks of a roughly symmetrical mcc often one system is dominant over the other the second geometry characterizes asymmetrical mcc bounded by a single normal shear zone which is upwarped during uplift and doming of the core caused by tectonic denudation detailed strain analysis performed in several extensional shear zones shows that the deformation regime is heterogeneous and results from general noncoaxial flow deformation along the shear zones evolves progressively from slight homogeneous pure shear strain to intense heterogeneous noncoaxial shear strain strain distribution within the lower crust is less well constrained by field observation however analogies between cocorp and ecors deep seismic reflection profiles give important constraints on crustal structure wide zones of highly subhorizontally layered lower crust and a flat high amplitude reflection moho characterize both evolved orogenic domains suggesting that major deformations and flow occur within the lower crust during extension a kinematic model involving heterogeneous crustal deformation and regional scale flow fits relatively well with late orogenic structures observed in continental domains a weak hot upper mantle allows large scale flow of lower crust material from zones of deep ductile extension to uplifted domains of upper crustal denudation heterogeneous strain is accommodated by low angle extensional shear zones from localized zones of extension in the brittle crust to ductile lower crust combined pure and simple shear occurs along localized shear zones whereas at the scale of the whole lithosphere deformation nearly corresponds to a vertical pure shear such deformation processes which affect a thick and hot crust seem to be common in both compared domains suggesting that late orogenic extensional processes are slightly dependent of the type of contractional tectonics thus as much in the andean type west american cordilleran belt as in the collision type variscan belt late orogenic processes produced similar extensional features

transcurrent shearing granite sheeting and the incremental construction of the tabular 3 1 ga mpuluzi batholith barberton granite greenstone terrane south africa structural petrographic and geochronological studies show that the tabular 3 1 ga mpuluzi batholith in the barberton granite gneiss terrane in south africa was emplaced via a combination of external and internal processes external structural controls are indicated by systematic variations in intrusive relationships and strain along the margins of the mpuluzi batholith and are consistent with an emplacement of the granite in a dilational jog within a ne ene trending system of dextral transcurrent synmagmatic shear zones internally the mpuluzi batholith is essentially made up of granite sheets the structurally higher parts of the granite are made up of shallowly dipping sheets that are underlain by an anastomosing network of steeply dipping variably deformed dykes and sheets these granite sheets at lower structural levels intruded either into the actively deforming shear zones or into extensional sectors between and along the bounding shear zones multiple intrusive relationships and geochronological evidence suggests that granite sheeting and the assembly of the pluton occurred over a period of 3 13 ma the spatial and temporal relationship between deformation and magma emplacement reflects episodes of incremental dilation related to deformation along the bounding shear zones and granite sheeting the transition to the mainly subhorizontal granite sheets at higher structural levels of the tabular mpuluzi batholith indicates the intrusion of the granites during subhorizontal regional shortening where the reorientation of the minimum normal stress to vertical attitudes at the shallow levels of emplacement allowed for vertical dilation and subhorizontal emplacement of the granite sheets

hornblende 40ar 39ar geochronology across terrane boundaries in the sveconorwegian province of s norway abstract hornblende incremental heating 40 ar 39 ar data were obtained from augen gneiss and amphibolite of the sveconorwegian province of s norway in the rogaland vest agder and telemark terranes four pyroxene rich samples located close 10 km to the anorthosite charnockite rogaland igneous complex define an age group at 916 12 14 ma and six samples distributed in the two terranes yield another group at 871 8 10 ma the first age group is close to the reported zircon u pb intrusion age of the igneous complex 931 2 ma and the regional titanite u pb age 918 2 ma whereas the second group overlaps reported regional mineral rb sr ages 895 853 ma as well as biotite k ar ages 878 853 ma in the first group the comparatively dry parageneses of low p thermal metamorphism m2 associated with the intrusion of the igneous complex are well developed and hornblende 40 ar 39 ar ages probably record a drop in temperature shortly after this phase in other hornblende biotite rich samples with presumably a higher fluid content the hornblende ages are probably a response to hornblende fluid interaction during a late sveconorwegian metamorphic or hydrothermal event a ca 220 m y diachronism in hornblende 40 ar 39 ar ages is documented between s telemark ca 870 ma and bamble ca 1090 ma differential uplift between these terranes was mostly accommodated by shearing along the kristiansand porsgrunn shear zone the final stage of extension along this zone occurred after intrusion of the herefoss post kinematic granite at 926 8 ma on the contrary the southern part of the rogaland vest agder and telemark terranes share a common cooling evolution as mineral ages are similar on both sides of the mandal ustaoset line the tectonic zone between them the succession within 20 m y of a voluminous pulse of post tectonic magmatism at 0 93 ga a phase of high t low p metamorphism at 0 93 0 92 ga and fast cooling at a regional scale ca 0 92 ga suggests that the southern parts of rogaland vest agder and telemark were affected by an event of post thickening extension collapse at that time this event is not recorded in bamble

s type granites and their probable absence in southwestern north america criteria that have been and still are used to characterize s type granites of the lachlan fold belt lfb of southeastern australia are reviewed and comparisons are made with various peraluminous granites of southwestern north america some of which have been classified as s types on the basis of insufficient data virtually all of the vast volume of s type granites in the lfb are near surface batholithic granites that are commonly associated with s type volcanics and are not associated with regional metamorphic rocks and migmatites they are strongly peraluminous as shown by the presence of cordierite granites with primary muscovite are rare all are low in na ca and sr as a result of chemical weathering during formation of the sedimentary sources peraluminous granites of various ages in southwestern north america are distinctly different they rarely contain cordierite a mineral characteristic of lfb s types but some are highly evolved such that fe mn rich garnet has crystallized they are dominantly two mica granites indicating crystallization at higher water fugacities and greater depths than most peraluminous granites of the lfb cordierite bearing volcanics s types have not been reported sodium is generally high in the peraluminous granites of southwestern north america some of these rocks have trondhjemitic affinities the parent magmas seem more likely to have been produced by partial melting of altered basaltic rocks locally some peraluminous rocks marginal to metaluminous types may owe their compositions to high level contamination of i types these are not s type rocks no compelling evidence has been presented that any of the peraluminous granites of southwestern north america are s types

successive midcrustal high grade metamorphic events provide insight into mid archean mountain building along the se margin of the proto kaapvaal craton in this study we investigate the evolution of continental crust at the paleoarchean to mesoarchean boundary by documenting the deposition deep burial and partial melting of metasedimentary gneisses along the se margin of the proto kaapvaal craton successive high grade metamorphic events recorded by the gneisses between ca 3 23 and 3 07 ga not only coincided with the timing of subduction accretion in the adjacent barberton greenstone belt at ca 3 23 3 22 ga but also with discrete pulses of potassic granitic magmatism during differentiation and consolidation of the newly assembled lithosphere mineral equilibria modeling demonstrates that the granulites evolved along pressure temperature p t paths similar to those documented for metamorphism in modern collisional orogens high temperature deformation at ca 3 11 3 07 ga during uplift of the terrane was coaxial with the main ne sw trending structural grain of the barberton greenstone belt and reflects the regional nw se shortening and ne sw orogen parallel extension exhibited by the younger potassic granites we reconcile these features with mesoarchean terrane assembly in barberton via two nw dipping subduction zones the trace of the first is represented by the main terrane boundary within the barberton greenstone belt the second resulted in accretion burial and high temperature metamorphism along the se margin of the kaapvaal craton with the granulites providing valuable insight into the mid to lower crustal response to what appears to have been a protracted accretionary orogenic event

ultrahigh temperature granulite metamorphism 1050 c 12 kbar and decompression in garnet mg70 orthopyroxene sillimanite gneisses from the rauer group east antarctica highly magnesian and aluminous migmatitic gneisses from mather peninsula in the rauer group eastern antarctica preserve ultrahigh temperature uht metamorphic assemblages that include orthopyroxene sillimanite quartz garnet sillimanite quartz and garnet orthopyroxene sillimanite garnet that ranges up to xmg of 71 5 coexists with aluminous orthopyroxene that shows zoning from cores with 7 5 8 5 wt al2o3 to rims with up to 10 6 wt al2o3 adjacent to garnet peak p t conditions of 1050 c and 12 kbar are retrieved from fe mg al thermobarometry involving garnet and orthopyroxene in very good agreement with independent constraints from petrogenetic grids in feo mgo al2o3 sio2 and related chemical systems sapphirine orthopyroxene and cordierite form extensive symplectites and coronas on the early phases the specific reaction textures and assemblages involving these secondary phases correlate with initial garnet xmg with apparent higher pressure reaction products occurring on the more magnesian garnet and are interpreted to result from an initial phase of ultrahigh temperature near isothermal decompression uht itd from 12 to 8 kbar at temperatures in excess of 950 c later textures that involved biotite formation and then partial breakdown along with garnet relics to symplectites of orthopyroxene cordierite or cordierite spinel may reflect hydration through back reaction with crystallizing melts on cooling below 900 850 c followed by itd from 7 to 8 kbar to c 5 kbar at temperatures of 750 850 c the tectonic significance of this p t history is ambiguous as the rauer group records the effects of archean tectonothermal events as well as high grade events at 1000 and 530 ma late stage biotite formation and subsequent itd can be correlated with the p t history preserved in the proterozoic components of the rauer group and hence with either 1000 or 530 ma collisional orogenesis however whether the preceding uht itd history reflects a temporally unrelated event e g archean or is simply an early stage of either the late proterozoic or pan african tectonism as recently deduced for similar uht rocks from other areas of the east antarctica remains uncertain

water contents of silicic to intermediate magmas silicic to intermediate magmas have water contents that range from 1 wt to around 7 wt depending on the character and depth of the magma source type of melting reaction and the degree of differentiation the condition of water saturation is rare implying that crustal magma genesis generally takes place under fluid absent conditions or that any fluid present must contain volatile species other than h2o the source and quantity of water present during partial melting profoundly affect the types of melting reactions residues and magmas as well as subsequent magma evolution for s type granitic magmas melting reactions involving muscovite breakdown in pelites yield low temperature wet melts that form veins pockets and small plutons in regional metamorphic terranes biotite breakdown in pelites near the amphibolite granulite facies transition yields hotter magmas with variable water contents these are emplaced at medium to high levels under granulite facies conditions biotite breakdown in quartzofeld spathic rocks yields high temperature dry magmas emplaced as subvolcanic batholiths and volcanics

model experimental research on deformation and subsidence characteristics of ground and wall rock due to mining under thick overlying terrane abstract based on the prototype of a mine a physical simulation test is conducted the characteristics of the deformation and failure of the ground surface and the wall rock around a goaf as well as the creep behavior of the wall rock deformation and the failure mechanism are analyzed the simulation test has greatly improved our understanding on the wall rock s deformation and failure characteristics for the first time digital close range photogrammetry was used to measure the displacements in a sectional model test the measurements by this technique agreed very well with those obtained by other methods such as using dial gauges

a zoning model for coal mining induced strata movement based on microseismic monitoring a microseismic monitoring technique is adopted to investigate the distribution regularity of microseismic events released by the coal mining induced roof rock mass along the vertical and horizontal directions in combination with mine geological data on the basis of the quantity and energy distributions of the microseismic events recorded using the microseismic monitoring technique a zoning method is first established for the roof strata movement in the vertical and horizontal directions the vertically zoning method is then applied to analyze the microseismic monitoring results obtained in the dongjiahe coal mine which divides rock mass into six zones along the vertical direction i e the caved zone the block zone the vertical fracture through going zone the vertical fracture zone the separation zone and the continuous zone the horizontally zoning model divides the roof strata movement into three zones i e the calm zone the generation zone impacted by working face and the historical generation zone after that based on the horizontally zoning model a method is developed to determine the displacement angle using the microseismic monitoring data which has been verified in the dongjiahe coal mine

experimental and theoretical constraints on melt distribution in crustal sources the effect of crystalline anisotropy on melt interconnectivity in partially molten systems the equilibrium distribution of melt at the grain scale is governed by the principle of interfacial energy minimization in ideal sources i e partially molten rocks that are monomineralic have single valued solid liquid and solid solid interfacial energies and are subject to hydrostatic stress the wetting angle is known to be a unique characteristic which specifies the melt configuration for a given melt fraction crustal rocks cannot be modelled as ideal sources because of their polymineralic nature the moderate to high anisotropy of interfacial energies which characterizes common refractory minerals and the possible presence of a crystallographic preferred orientation that partially molten crustal rocks depart from ideal sources is documented by a series of high p high t experiments illustrating the textural relationships of biotite and amphibole with silicic melts the melt distributions observed in these experiments differ significantly from those expected in ideal sources 1 crystal melt interfaces are commonly planar rational faces rather than smoothly curved irrational surfaces and 2 the concept of a unique wetting angle does not hold as shown in the biotite silicic melt system these textural features demonstrate that anisotropy of crystal melt interfacial energy is a factor of primary importance in modelling the grain scale distribution of partial melts the petrological implications of our study are the following 1 1 at high degrees of anisotropy and low melt fractions melt is predicted to form isolated plane faced pockets at grain corners the overall shape of these pockets and therefore the value of the connectivity threshold c are expected to be very sensitive to the ratio of solid solid to solid liquid interfacial energies ss sl c is the melt fraction at which melt interconnectivity is established melt pockets with low volume to surface ratio and low but non constant wetting angles should prevail at high ss sl resulting in very low values of c 1 to a few vol higher values of c a high volume to surface ratio of melt pockets and high wetting angles are expected at low ss sl 2 2 the wetting angle at hornblende hornblende melt junctions at 1200 mpa 975 c is 25 a review of existing data indicates that quartz melt and feldspar melt wetting angles are also low to moderate 12 60 a very low value of c should therefore be the general rule during crustal anatexis in particular a connectivity threshold lower than 3 4 vol is predicted for partially molten amphibolite 3 3 in biotite rich rock types such as melanosomes in migmatites the combination of a pronounced crystalline anisotropy and a marked preferred orientation of mica flakes leads to a very low permeability normal to layering biotite rich melanosomes should therefore impede chemical interactions between neighbouring leucosomes and mesosomes

block geometry and rockmass characterization for prediction of dilution potential into sub level cave mine voids when sub level caving is used as an underground mining method for the exploitation of diamondiferous kimberlite pipes a deep steep sided pipe is created that is susceptible to sloughage pipe wall sloughage allows waste rock to mix with and dilute the caved kimberlite ore using the koala kimberlite pipe at ekati diamond mine as a case study a method has been developed using rockmass and rock structure characterization integrated with discrete block dem simulation for comparative assessment of dilution potential and the classification and mapping of dilution source zones around the kimberlite pipe the assessment process involves the development of a geomechanical model to delineate the structural fabric within the host rockmass and characterize the size and shape distributions of discrete rock blocks defined by intersecting discontinuities combining the slope geometry with the structural geology model allows for a zone by zone numerical analysis of pipe wall stability under gravitational loading a final dilution map is developed in order to target problem areas where the highest levels of slope instability are anticipated

polyphase late paleozoic tectonothermal evolution of the southwestern meguma terrane nova scotia evidence from 40ar 39ar mineral ages 40ar 39ar incremental release ages of hornblende muscovite and biotite from a variety of granitic stocks and host metamorphic rocks suggest a complex late paleozoic tectonothermal evolution for the southwestern meguma terrane regional d1 folding with cleavage formation under greenschist lower amphibolite facies m1 metamorphic conditions occurred at ca 400 410 ma and was followed by emplacement of a series of granitic stocks ranging in age between ca 375 and 315 ma these were emplaced at relatively shallow crustal levels and developed contact metamorphic aureoles of variable grade these are locally superposed on m1 regional metamorphic assemblages and result in a complex isograd pattern 40ar 39ar mineral ages suggest episodes of contact metamorphism occurred at 1 360 375 ma possibly related to emplacement of the south mountain batholith or temporal equivalents 2 350 356 ma around the port mouton pluton and northeastern shelburne pluton 3 ca 315 325 ma near the wedgeport pluton and in

large scale melt depletion in granulite terranes an example from the archean ashuanipi subprovince of quebec this study uses field petrographic and geochemical methods to estimate how much granitic melt was formed and extracted from a granulite facies terrane and to determine what the grain and outcrop scale melt flow paths were during the melt segregation process the ashuanipi subprovince located in the north eastern superior province of quebec is a large 90 000 km2 metasedimentary terrane in which 85 of the metasediments are of metagreywacke composition that was metamorphosed at mid crustal conditions 820 900 c and 6 7 kbar in a late archean dextral transpressive orogen decrease in modal biotite and quartz as orthopyroxene and plagioclase contents increase together with preserved former melt textures indicate that anatexis was by the biotite dehydration reaction biotite quartz plagioclase melt orthopyroxene oxides using melt orthopyroxene ratios for this reaction derived from experimental studies the modal orthopyroxene contents indicate that the metagreywacke rocks underwent an average of 31 vol partial melting the metagreywackes are enriched in mgo cao and feot and depleted in sio2 k2o rb cs and u have lower rb sr higher rb cs and th u ratios and positive eu anomalies compared to their likely protolith these compositions are modelled by the extraction of between 20 and 40 wt granitic melt from typical archean low grade metagreywackes a simple mass balance indicates that about 640 000 km3 of granitic melt was extracted from the depleted granulites the distribution of relict melt at thin section and outcrop scales indicates that in layers without leucosomes melt extraction occurred by a pervasive grain boundary porous flow from the site of melting across the layers and into bedding planes between adjacent layers in other rocks pervasive grain boundary flow of melt occurred along the layers for a few to tens of centimetres followed by channelled flow of melt in a network of short interconnected and structurally controlled conduits visible as the net like array of leucosomes in some outcrops the leucosomes contain very little residual material 5 biotite orthopyroxene indicating that the melt fraction was well separated from the residuum left in situ as melt depleted granulite only 1 3 vol percentage melt remained in the melt depleted granulites hence the extraction of melt generated by biotite dehydration melting in these granulites was virtually complete under conditions of natural melting and strain rates in a contractional orogen

an experimental study of grain scale melt segregation mechanisms in two common crustal rock types creation of pathways for melt to migrate from its source is the necessary first step for transport of magma to the upper crust to test the role of different dehydration melting reactions in the development of permeability during partial melting and deformation in the crust we experimentally deformed two common crustal rock types a muscovite biotite metapelite and a biotite gneiss were deformed at conditions below at and above their fluid absent solidus for the metapelite temperatures ranged between 650 and 800 c at pc 700 mpa to investigate the muscovite dehydration melting reaction for the biotite gneiss temperatures ranged between 850 and 950 c at pc 1000 mpa to explore biotite dehydration melting under lower crustal conditions deformation for both sets of experiments was performed at the same strain rate e 1 37 10 5 s 1 in the presence of deformation the positive v and associated high dilational strain of the muscovite dehydration melting reaction produces an increase in melt pore pressure with partial melting of the metapelite in contrast the biotite dehydration melting reaction is not associated with a large dilational strain and during deformation and partial melting of the biotite gneiss melt pore pressure builds more gradually due to the different rates in pore pressure increase melt enhanced deformation microstructures reflect the different dehydration melting reactions themselves permeability development in the two rocks differs because grain boundaries control melt distribution to a greater extent in the gneiss muscovite dehydration melting may develop melt pathways at low melt fractions due to a larger volume of melt in comparison with biotite dehydration melting generated at the solidus this may be a viable physical mechanism in which rapid melt segregation from a metapelitic source rock can occur alternatively the results from the gneiss experiments suggest continual draining of biotite derived magma from the lower crust with melt migration paths controlled by structural anisotropies in the protolith

on the rheologically critical melt fraction abstract with increasing melt fraction the strength of partially molten granite decreases from a value characteristic of solid competent rock to a value nearly equal to that of the melt previously published mechanical and microstructural data indicate that deformation in partially molten rocks often involves brittle processes thus the pressure in the melt is expected to be important in determining strength when the volume changes during deformation strength and fluid flow will be coupled by such parameters as permeability k storage capacity per unit volume or storativity s melt compressibility f grain size d fluid viscosity and strain rate experiments on brittle rock at low temperatures show that the strain rate at which the internal fluid pressure can be maintained constant is approximately proportional to k s an evaluation of published experimental data suggests that this relation also holds for partially molten granites indicating that the strength of these rocks depends on their transport properties since the permeability is related to below a critical melt fraction rcmf the melt pressure will change if deformation is not iso volumetric by assuming a power law relationship between k and we estimate that rcmf f d m 1 n 1 where m and n relate permeability to grain size and respectively

fluids p t paths and the fates of anatectic melts in the earth s crust this paper presents a model for the longevity and physical behaviour of anatectic melts in the earth s crust it is assumed that a thermal anomaly has caused partial fusion of biotite plagioclase quartz rocks to produce a granitic melt and restitic solids the focus is on the potential chemical and physical outcomes as a function of the various p t fluid conditions rocks undergoing fluid present melting will sustain an increase in bulk density and will become more gravitationally stable diapiric up welling of such material should not occur in fluid absent melting the bulk density will decrease and foster gravitational instability stresses in the surrounding rocks could however lead to fracture and rapid evacuation of the melt with excess fluid and without melt segregation isobaric cooling will cause immediate freezing if t rises above the biotite quartz melting reaction freezing will still occur at the original reaction t diapiric up welling should not occur biotite bearing diatexites might be formed by large degrees of fusion but magma ascent is unlikely in isothermal decompression immediate freezing will ensue and the migmatite should contain orthopyroxene rather than biotite with excess fluid and melt segregation cooling will induce freezing at the fluid saturated granite solidus magma ascent could however occur even for xflh2o 1 in isothermal decompression melt will persist to the granite solidus for the imposed xflh2o limited magma ascent could occur all granites should contain primary igneous biotite for fluid deficient rocks without melt segregation freezing will occur at the t of the original melting if the reaction is overstepped solidification will occur at the original xflh2o magma formation is unlikely migmatites should contain either pyroxene retrogressed to biotite or biotite alone on decompression immediate freezing is likely if t remains at the biotite quartz reaction for higher t melt will survive decompression and freeze at the fluid saturated solidus for some increased xflh2o magma ascent is possible and the melt will freeze very close to the wet granite solidus in fluid deficient rocks with melt segregation cooling and crystallization will cause fluid saturation in situ segregated melt will freeze at the original xflh2o melt ascent will however cause exsolution of a co2 rich fluid with fluid escape melt will freeze close to the wet granite solidus an increase in melt proportion may accompany magma ascent or source up welling any low p granite intrusion should be charnockitic for fluid absent rocks without melt segregation freezing will occur on cooling to the t of the original reaction only transitory migmatites could be formed but melt will survive decompression almost to the h2o saturated granite solidus the rocks will reveal former melt presence only in the existence of veins of coarse retrograde biotite with isothermal decompression further melting may occur forming an orthopyroxene bearing granulite facies migmatite in fluid absent situations with melt segregation magma could be efficiently transported to higher crustal levels if the melt proportion were insufficient for magma formation granulite facies migmatites would result ascending melt would progressively dissolve any entrained restite the granites produced should be charnockitic to aid in interpretation of the modelling results we suggest that it may be slightly more common for the highest grade metamorphic terranes to exhibit isobaric cooling paths that fluid present anatexis is normally limited to the shallower parts of the crust and that fluid absent reactions are more likely at greater depths we conclude that the best models for natural fluid present anatexis are those dealing with essentially pure h2o fluid and that fluid deficient conditions will dominate over fluid excess we also believe that it is common for melts to be physically segregated on scales larger than the diffusion paths of many elements

mining induced ground deformation in tectonic stress metal mines a case study abstract in situ monitoring data of ground deformation in the western area of chenchao iron mine were collected over eight years results were analysed to conduct a preliminary investigation into the ground movement induced by underground mining 1 in the northeastern area the ratios of horizontal to vertical displacement increase gradually and the horizontal displacement may be as much as an order of magnitude larger than the vertical displacement at a large distance which induces regional horizontal movement curves of the ratio of horizontal to vertical displacement with respect to time can be categorised as fluctuation fallback convergence and increase types 2 in the mine road stack site and southern area around the high voltage tower ground deformation can be divided into two stages stable deformation and rapid deformation while in the southeastern area of the transport tunnel service shaft and road tunnel it can be divided into three stages stable deformation rapid deformation and subsequent stable deformation three categories are found in the time displacement curves folding s and linear types 3 the ground deformation of the footwall underwent a significant change in january 2010 because the large horizontal tectonic stress in the mine was released at that time surrounding rock masses were subjected to toppling deformation along the major structural plane in the northeastern area while tensile deformation occurred perpendicular to the major structural plane in the northern area

progressive failure of hanging wall and footwall kiirunavaara mine sweden abstract this paper presents an evaluation of the progressive failure of the hanging wall and the footwall at the kiirunavaara mine in northern sweden the failure of the hanging wall and footwall is a direct result of sublevel caving operations and has caused significant surface and subsurface disturbances on the hanging wall these disturbances include large scale subsidence surface cracking and shear displacements the footwall has experienced shear displacements and failure of underground openings using mine data failure mechanisms describing the progressive failure of the hanging wall and footwall were developed these data indicate that the primary failure mechanism is shear failure with toppling and wedge failures being present as secondary mechanisms shear failure occurs along pre existing geologic structures as well as through intact rock the data also showed that the hanging wall and footwall rock mass failure is closely linked to mining activity movements of caved waste rock and the presence of geologic structures an analytical model is presented to provide a simple tool for evaluating the extent of rock mass failure in the hanging wall and footwall while also accounting for interactions of caved waste rock the analytical model is unique in that it combines a limit equilibrium approach for the hanging wall and footwall with a coulomb type surface traction force to represent the caved rock the developments presented in this paper can be used to further the understanding of large scale rock mass behavior related to underground mining the failure mechanisms presented may also be applicable to open pit slope stability

high purity quartz mineralisation in kyanite quartzites norway this study presents an evaluation of norwegian kyanite quartzites from gullsteinberget knosberget kjeks berget sormbrua tverradalen juovvacorru and nasafjellet as potential deposits of high purity quartz hpq for use as raw material for special applications in high technology industries fine grained quartz which forms 70 to 85 vol of these rocks generally contains less than 50 gg 1 total sum of the structurally incorporated trace elements b li al ge ti fe mn k and p the concentrations are in the same range as those found in hpq products which are being mined and produced in norway and elsewhere quartz analyses were performed using laser ablation inductively coupled plasma mass spectrometry compli mentary whole rock analyses and cathodoluminescence studies of quartz were carried out to reveal processes which have led to the low trace element concentrations in quartz this discovery together with a better knowledge of the processes leading to the formation of hpq in kyanite quartzites could lead to the recognition of a new global type of hpq resource applicable for industrial use however the processing technology necessary to separate hpq from kyanite quartzite economically has not been developed so far

partial melting and the origin of metapelitic granulites in the southern marginal zone of the limpopo belt south africa abstract two potentially realistic models exist to explain the origin of the granulite facies rocks of the southern marginal zone i co2 fluxing inducing the necessary high temperature dehydration reactions and ii melting of hydrous minerals to yield an h2o undersaturated granitic melt in equilibrium with a dehydrated granulitic assemblage petrographic and field evidence from the bandelierkop quarry in the southern marginal zone indicate a sequence of melting reactions involving muscovite and biotite relict textural evidence indicates that the reaction responsible for the generation of most of the melt bi sil qz plag melt ga ksp was fluid absent the melting reactions can be shown to have occurred during the prograde metamorphic path with the highest temperature reaction bi qz plag hy cord melt occurring at approximately peak metamorphic conditions 850 c and less than 9 5 kbar this suggests a fluid absent mode of granulite formation a subsequent retrograde reaction cord ksp h2o ky qz related to a rise in h2o during in situ crystallisation of the melt did not destroy the granulite assemblages and hypersthene remains stable in areas of the southern marginal zone that record pressures of greater than 6 5 kbar during retrogression

deep crustal seismic reflection profiling across two major tectonic zones in southern sweden abstract a seismic reflection profile has been shot in varmland southwestern sweden across two major tectonic zones the protogine zone and the mylonite zone the crustal bedrock units separated by the tectonic zones are clearly distinguished in the seismic profile by changes in the reflection character in the upper 5 6 km the protogine zone is represented by a 15 20 km wide band of dipping structures the mylonite zone dips too steeply to be seen directly and a lack of clear reflectors at depth makes a continuation down through the crust hypothetical in the uppermost 5 6 km between the two tectonic zones stronger and more continuous reflections can be seen and are interpreted as being connected with hyperite intrusions which have been mapped at the surface the lower crust shows generally little reflectivity with only short and weak reflectors an exception occurs at mid crustal depths where a number of clearly recognizable bands of reflected energy are suggested to be major shear zones formed during sveconorwegian grenvillian thrusting towards the east a slight increase in reflectivity in the depth range 42 48 km correlates well with the moho depth determined from refraction seismic studies the possible relationships between data acquisition parameters and the observed scarcity and low strength of reflections from the deeper crust have been considered in some detail it is shown that the use of 28 hz single geophones instead of 10 hz geophone strings along a major part of the profile did not reduce the signal to noise ratio for deep reflections however the varying source characteristics in combination with the different quality of the recordings made computation of the residual static corrections difficult which may have resulted in a partly destructive stacking of seismic traces in this way the low reflectivity of the deeper crust in this area is further brought out in the stacked seismic sections

h type hybrid granitoids a proposed revision of the granite type classification and nomenclature abstract recent studies on calc alkaline plutonic rocks reveal field and petrographic relationships with strong implications for the processes involved in their genesis the presence of magmatic inclusions and magma mingling zones in these rocks supports an origin by magma mixing compositional variations and isotopic anomalies are a good test for such petrogenetic models most of these calc alkaline plutonic rocks which characterize both collision related and active plate margin environments have been classically identified as i igneous type granitoids following chappell and white s 1974 classification and then interpreted as derived from partial melting of older igneous rocks restite model if the magma mixing origin of a type of granitoids can be demonstrated from field and petrographic evidence and supported by chemical and isotopic variations the nomenclature must be changed in this sense the new category of h hybrid type is tentatively introduced it includes most of the so called i type granitoids and some of the s type as deduced from field relationships of magma mingling zones a mixing model is suggested that can operate on a large scale to explain the petrogenesis of the hercynian calc alkaline granodiorites of iberia finally a modified classification of common plutonic rocks in orogenic environments is proposed

comment and reply on s type granites and their probable absence in southwestern north america the problem of muscovite in granites is also raised by dickson muscovite is common in felsic s type granites as stated by chappell and white 1974 but how much is primary and how much is secondary are debatable we currently think that very little is primary above the solidus we are not arguing that muscovite whether primary or secondary garnet and andalusite are not found in s types we are arguing that these minerals may also be found in some i types dickson is quite correct in saying that replacement of cordierite by micas results from hydration which may also affect the alkali aluminum ratio of the rock however he is not necessarily correct in his assertion that water must be introduced into the system it may be magmatic water released from the magma near the solidus during cooling and crystallization more systematic goechemical and isotopic work is required on petrographically well documented granite suites before this question is resolved

melt production during granulite facies anatexis experimental data from primitive metasedimentary protoliths we conducted fluid absent partial melting experiments at 0 5 and 1 0 gpa in the temperature range 750 to 1000 c to investigate the influence of bulk rock mg 100mg mg fe and the effects of additional tio2 on the granulite grade anatectic evolution of relatively magnesian metapelites and metagreywackes in these experiments melting began between 780 and 830 c by the incongruent breakdown of biotite to produce quartz saturated granulite facies residual mineral assemblages in equilibrium with h2o undersaturated granitic melt the glass quenched melt compositions produced in this study vary little generally the glasses have compositions similar to those of many natural strongly peraluminous leucogranites the solidus temperatures in both rock types increase with increasing mg but are unaffected by the presence or absence of a tio2 component at 0 5 gpa the metapelites melted at temperatures up to 50 c lower than the equivalent metagreywackes but at 1 gpa there was no discernible difference this study suggests that the fluid absent solidus has a steep positive dp dt slope in metapelites and steep negative dp dt slope in metagreywackes the pattern of melt production with increasing temperature is strongly controlled by the upper limit of biotite stability in tio2 free compositions this was found to increase by 15 to 20 c in the metapelites and by 30 to 40 c in the metagreywackes as a function of increasing mg from 49 to 81 the presence of a tio2 component increases the upper limit of biotite stability by 50 c in the metapelites and by 80 c in the metagreywackes over that observed in the equivalent tio2 free compositions in consequence in the tio2 free samples large pulses of melt up to 35 wt are produced over narrow temperature ranges as little as 15 c in these experiments between 830 and 875 c in the tio2 bearing samples the major pulse of melt production occurs more gradually between 830 and 900 c

exhumation of high pressure metamorphic rocks during crustal extension in the d entrecasteaux region papua new guinea the d entrecasteaux islands of eastern papua new guinea consist of a number of active metamorphic core complexes formed under an extensional tectonic setting related to sea floor spreading in the west woodlark basin the complexes are defined by mountainous domes 2500 m high of fault bounded high grade metamorphic rocks including eclogite facies intruded by 2 4 ma granodiorite plutons garnet clinopyroxene exchange thermometers indicate that the temperature of equilibration of the eclogites was 730 900 c the jadeite component of omphacite indicates minimum pressure of 21 kbar suggesting depths of 70 km the metamorphic rocks have undergone widespread retrogression to amphibolite facies retrogression of the metamorphic basement is associated with shearing and formation of the metamorphic core complexes p t conditions in the early stages of shear zone activity determined using the garnet biotite exchange thermometer and the gasp and grips barometers were 570 730 c and 7 11 kbar a second phase of re equilibration at much lower pressures appears to be related to the widespread intrusion of granodiorite plutons one re equilibrated gneiss indicated maximum temperature of 730 c at estimated pressures of approximately 4 kbar this late high temperature metamorphism is also indicated by reactions involving the production of hercynite and corundum in aluminous gneisses and formation of sillimanite at the expense of kyanite two major episodes of granodiorite intrusion occurred during uplift and exhumation of the core complexes both closely coincide spatially with high temperature metamorphic rocks the onset of deformation in extensional shear zones and subsequent uplift of the metamorphic basement these observations indicate a fundamental link between uplift and granodiorite intrusion during continental extension and the formation of the d entrecasteaux islands metamorphic core complexes

wetting behavior of partial melts during crustal anatexis the distribution of hydrous silicic melts in polycrystalline aggregates of quartz the equilibrium distribution of hydrous silicic melts in polycrystalline aggregates of quartz was characterized in a series of partial melting and melt distribution experiments in the systems quartz albite orthoclase h2o and quartz anorthite h2o at 650 to 1000 mpa and 800 to 900 c near equilibrium textures in these experiments are characterized by very low quartz quartz melt wetting angles and by a substantial number of thin melt films along grain boundaries wetting angles in the h2o saturated experiments are as follows 18 at 800 c 1000 mpa and 12 at 900 c 1000 mpa in the granitic system 18 at 850 c 650 mpa 15 at 900 c 650 mpa and 15 at 900 c 1000 mpa in the quartzanorthite system in the granitic system at 900 c 1000 mpa a decrease of h2o content in melt from 17 wt at saturation to 6 wt results in a slight increase of wetting angle from 12 to 16 these low wetting angles and the observation that many grain boundaries are wetted by melt films indicate that the ratio of quartz quartz to quartz melt interfacial energies ss s1 is high 2 secondary electron imaging of fracture surfaces of melt poor samples provided a three dimensional insight into the geometry of melt at low melt fraction melt forms an interconnected network of channels along grain edges as predicted for isotropic systems with wetting angles below 60 this high permeability geometry suggests that the segregation of granitic melts is not as sluggish as previously anticipated simple compaction calculations for a permeability range of 10 12 to 10 9 m2 indicate that segregation may operate at low to moderate melt fractions below 30 vol within relatively short time scales i e 105 to 106 years quartzmelt textures show significant deviations from the equilibrium geometries predicted for isotropic partially molten systems the most consistent deviation is the pervasive development of crystallographically controlled planar faces of quartz these faces provide definitive evidence for non isotropic quartz melt surface energy for most silicates other than quartz the grain scale distribution of partial melts deviates even more significantly from equilibrium distributions in isotropic systems accordingly in order to describe adequately melt distributions in most natural source regions the equilibrium model should be modified to account for anisotropy of solid liquid interfacial energy

geotectonic significance of mn fe ba and pb zn cu ag mineralizations along the sveconorwegian grenvillian front in scandinavia

melt extraction and accumulation from partially molten rocks current models for melt segregation and ascent are not adequate to accurately describe transport and accumulation in combination we propose that transport is discontinuous and in batches and that accumulation occurs by stepwise merging of batches a simple numerical model of jostling spheres that merge when they touch was used to represent stepwise accumulation and transport of batches by propagation of hydrofractures results of the numerical model indicate that such a system may quickly develop into a self organised critical soc state in this state the distribution of melt batch volumes can be described by a power law with an exponent m that lies between 2 3 and 1 once a self organised critical state is established the system is capable of discharging any additional melt without further change to itself deformation aids melt extraction efficiency as it increases the mobility of hydrofractures enhances accumulation and hence lowers the exponent m full connectivity of melt needs never to be reached in the system and melt transport and extraction can occur at very low melt fractions the chemical evolution of melt from source to emplacement level will be governed by the discontinuous mixing and mingling of batches each with different histories and possibly different sources if no subsequent homogenisation occurs in a magma chamber or the final emplacement structure the process can be identified by chemical heterogeneity of plutons and volcanic rocks

late sveconorwegian metamorphism and deformation in southwestern sweden abstract the precambrian of southwestern sweden is divided into eastern and western crustal segments separated by a major tectonic boundary the mylonite zone the southern part of the eastern segment is characterized by numerous occurrences of mafic granulites and charnockites the western segment comprising greenschist to amphibolite facies gneisses of supracrustal and plutonic origin sm nd mineral ages of the granulite facies metamorphism in the eastern segment range from 920 to 880 ma garnet pyroxene feldspar whole rock sm nd isochrons of the varberg charnockite and the traslovslage mafic granulite yield ages of 893 5 ma and 881 4 ma respectively this late sveconorwegian late grenvillian granulite facies metamorphism in southern sweden appears to be confined to the eastern segment while the last high grade metamorphic event in the western segment is contemporaneous with the 1100 ma old granulite facies metamorphism in the bamble area of se norway at least three phases of regionally important deformation postdate the late sveconorwegian metamorphism in southwestern sweden deformation related to movements within the mylonite zone was contemporaneous with or later than the granulite facies metamorphism in the varberg area and took place mainly under retrograde metamorphic conditions leading to almost complete replacement of garnet and pyroxene by amphibole biotite and plagioclase extensional tectonics were presumably important during the uplift of the granulite terrain east of the mylonite zone peak p t conditions during the late sveconorwegian metamorphic event were considerably higher than those required for the melting of granitoid rocks the sm nd ages of granulite facies parageneses within the eastern segment are approximately the same as those of numerous late sveconorwegian granite intrusions in southwestern scandinavia suggesting a genetic relationship between high grade metamorphism at depth and the emplacement of granites at higher crustal levels the nd model ages of the varberg charnockite agree reasonably well with the nd model ages of 1700 1600 ma old granites within the same crustal domain while the model age of the mafic granulite originally a mafic dyke corresponds roughly to the model ages of 930 ma old mafic dykes in se sweden

equity silver silver copper gold deposit alteration and fluid inclusion studies the two zones being mined occur along a continuous 1 500 m mineralized zone that is crudely parallel to cretaceous strata in the larger main zone ore minerals principally pyrite chalcopyrite and tetrahedrite are finely disseminated in the matrix of a volcanic breccia and are intimately associated with an aluminous and borosilicate alteration assemblage the smaller southern tail deposit contrasts with the main zone ore minerals principally pyrite arsenopyrite chalcopyrite and tetrahedrite with quartz and chlorite gangue are moderately coarse grained and fill open space in a crudely tabular brittle fractured zone whole rock k ar dates of southern tail wall rock and a highly tourmalinized breccia more than 1 km from the main zone both correspond closely to the older and more distant of the two eocene stocks a 59 4 m y old quartz monzonite suggested link between very weak sulfide development in the stock tourmaline breccia and the ore zones epithermal ore genesis model in which intrusive activity of quartz monzonite age heated acidic meteoric water to a high temperature and contributed a saline magmatic component to create an ore fluid movement of the ore fluid was controlled by structures and stratigraphy of the volcanic host rocks modified journal abstract

inferring a deep crustal source terrane from a high level granitic pluton the strathbogie batholith australia the strathbogie igneous complex is comprised of the ignimbritic rocks of the violet town volcanics and the granitic rocks of the strathbogie batholith it is late devonian in age and postorogenic extensional in tectonic setting the batholith was constructed from peraluminous metasediment derived magmas emplaced as several internally heterogeneous plutons chemical variation in the magmas was largely inherited from the protolith rather than having been produced by differentiation crystal liquid separation or magma mixing the strathbogie magmas formed during a granulite facies metamorphic event that caused partial melting of the rocks of the proterozoic selwyn block which forms the basement in this region the chemistry of the strathbogie batholith the violet town volcanics and various other felsic complexes of similar age implies that the selwyn block here originally consisted of andesite dacite greywacke and pelite probably deposited in a back arc extensional setting the sedimentary components of this protolith may have been deposited in a basin that was extending and deepening with time so that the sediments contained progressively higher ratios of clay to volcanic materials much later in the late devonian extensional tectonics allowed the emplacement of mantle magmas into the deep and middle crust causing the low pressure granulite facies metamorphic event that was responsible for the production of the crustal components in the granitic magmas of central victoria

self organisation and fracture connectivity in rapidly heated continental crust abstract volume expansion 1 5 volume strain with v melting positive and fluid absent partial melting in which v melting is positive of continental crust by intruding basaltic magma is a strongly irreversible process involving the dissipation of both thermal energy and matter partial melt using a simple random graph model we show by analogy how isolated fractures that form during rapid thermal perturbation in the source region can combine to form a single interconnected structure with high permeability once connected the fracture network may be thought of as a single structure or pattern that will remain stable so long as a strong temperature gradient is maintained in the source region estimates of fracture permeability that take into account changes in connectivity and fracture spacing range from approximately 10 10 to 10 5 m 2 many orders of magnitude greater than values considered typical during large scale crustal deformation and prograde regional metamorphism the ability of the isotropic fracture network to develop a top bottom directionality is crucial for buoyancy driven melt transport a physical model based on non linear evolution rules during thermal expansion is given that predicts the emergence of directionality vertical fracture alignment on a time scale of the order of 10 5 y the necessary ingredients are a deviatoric strain path a heterogeneous medium and a stiffness that evolves as a function of the local strain