horizontal structures in granulite terrains a record of mountain building or mountain collapse in many high temperature 800 c granulite terrains the development of characteristic horizontal structures occurred during the metamorphic culmination and was followed by isobaric cooling the absolute magnitude of isobaric cooling commonly 300 c implies cooling intervals of the order of the thermal time constant of the continental lithosphere 100 m y such prolonged isobaric cooling implies that no significant erosional denudation followed the development of the horizontal structures and thus precludes the prograde deformation being responsible for significant crustal thickening rather the prograde deformation more probably records bulk crustal thinning during extensional collapse of a previously thickened crust possibly triggered by detachment of a thickened thermal boundary layer at the base of the lithosphere

relationship between deep diagenetic quartz cementation and sedimentary facies in a late ordovician glacial environment sbaa basin algeria abstract production of hydrocarbons from sandstone reservoirs is complicated by their diagenetic history although many aspects of sandstone diagenesis are well studied the character and processes of glacial associated diagenesis remain unknown to address this problem the origin conditions and timing of quartz cementation in glacial ordovician sandstones of the sbaa basin algeria were constrained on the basis of fluid inclusion microthermometry electron microprobe data and quantification by image analysis combined with optical and cathodoluminescence microscopic studies samples of the cambro ordovician formations in the sbaa basin were investigated from four wells at burial depths between 2 0 and 2 5 km and at ambient temperatures between 110 and 130 c quartz cements range in abundance from 1 to 27 of bulk rock volume in all wells three separate phases of quartz cementation are readily distinguished by cathodoluminescence microscopy the main silica sources are interpreted to be dissolution of feldspar grains intergranular quartz dissolution stylolitization and illitization of smectite fluid inclusion data depths indicate that quartz overgrowths precipitated between 100 to 160 c this range of temperature corresponds to the visean namurian burial phase according to the basin thermal history image analysis demonstrates intergranular quartz dissolution also called pressure dissolution in the presence of thin illite coatings around detrital quartz grains these clay coatings were mechanically emplaced below the ordovician ice sheet by pressurized meltwater circulation and subsequent fluid expulsion within sandy subglacial soft bedrock that was initially porous and permeable therefore the subglacial bedrock lithology directly influenced quartz diagenesis because an increase in the content of clay matrix or the presence of an argillaceous layer can block the circulation of fluids flowing below the ice sheet which prevents the formation of clay coatings quartz cements in this environment are favored in less compacted areas without clay coatings and with high porosity the results of this study clearly illustrate the relationships among sedimentary facies ice dynamics and diagenetic architecture of the formation these types of processes may control the porosity permeability distribution in other glacial sandstone successions through quartz cementation and chemical compaction

halogen bearing minerals in syenites and high grade marbles of dronning maud land antarctica monitors of fluid compositional changes during late magmatic fluid rock interaction processes meta sedimentary rocks including marbles and calcsilicates in central dronning maud land cdml in east antarctica experienced a pan african granulite facies metamorphism with peak metamorphic conditions around 830 20 c at 6 8 0 5 kbar which was accompanied by the post kinematic intrusion of huge amounts of syenitic charnockitic magmas at 4 5 0 7 kbar the marbles and calcsilicates may represent meta evaporites as indicated by the occurrence of metamorphic gypsum anhydrite and cl rich scapolite that formed in the presence of saline fluids with x nacl in the range 0 15 0 27 the marbles and calcsilicates bear biotite tremolite and or hornblende and humite group minerals clinohumite chondrodite and humite which are inferred to have crystallized at about 650 c and 4 5 kbar the syenitic intrusives contain late magmatic biotite and amphibole formed between 750 and 800 c as well as relictic magmatic fayalite orthopyroxene and clinopyroxene two syenite and two calcsilicate samples contain fluorite corona textures in the marbles and calcsilicates suggest very low fluid rock ratios during the formation of the retrograde 650 c assemblages biotite in all but two syenite samples crystallized at log f h 2 o f hf ratios of 2 9 0 4 while in the calcsilicates both biotite and humite group minerals indicate generally higher log f h 2 o f hf values of up to 5 2 a few samples though overlap with the syenite values log f h 2 o f hcl derived from biotite covers the range 0 5 2 6 in all rock types within a single sample the calculated values for both parameters vary typically by 0 1 to 0 8 log units water and halogen acid fugacities calculated from biotite olivine orthopyroxene feldspar quartz equilibria and the above fugacity ratios are 1510 2790 bars for h2o 1 3 5 3 bars for hf and 7 600 bars for hcl the results are interpreted to reflect the reaction of relatively homogeneous magmatic fluids in terms of log f h 2 o f hf derived from the late magmatic stages of the syenites with both earlier crystallized still hotter parts of the syenites and with adjacent country rocks during down temperature fluid flow fluorine is successively removed from the fluid and incorporated into f bearing minerals close to the syenite into metamorphic fluorite in the course of this process log f h 2 o f hf increases significantly chlorine preferably partitions into the fluid and hence log f h 2 o f hcl does not change markedly during fluid rock interaction

u pb geochronology of zircon and polygenetic titanite from the glastonbury complex connecticut usa an integrated sem empa tims and shrimp study abstract u pb ages for zircon and titanite from a granodioritic gneiss in the glastonbury complex connecticut have been determined using both isotope dilution thermal ionization mass spectrometry tims and the sensitive high resolution ion microprobe shrimp zircons occur in three morphologic populations 1 equant to stubby multifaceted colorless 2 prismatic dark brown with numerous cracks and 3 elongate prismatic light tan to colorless cathodoluminescence cl imaging of the three populations shows simple concentric oscillatory zoning the zircon tims age weighted average of 207pb 206pb ages from group 3 grains 450 5 1 6 ma mswd 1 11 and shrimp age composite of 206pb 238 u age data from all three groups 448 2 2 7 ma mswd 1 3 are interpreted to suggest a relatively simple crystallization history titanite from the granodioritic gneiss occurs as both brown and colorless varieties scanning electron microscope backscatter bse images of brown grains show multiple cross cutting oscillatory zones of variable brightness and dark overgrowths colorless grains are unzoned or contain subtle wispy or very faint oscillatory zoning electron microprobe analysis empa clearly distinguishes the two populations brown grains contain relatively high concentrations of fe2o3 ce2o3 up to 1 5 wt nb2o5 and zr cerium concentration is positively correlated with total ree y concentration which together can exceed 3 5 wt oscillatory zoning in brown titanite is correlated with variations in ree concentrations in contrast colorless titanite both as discrete grains and overgrowths on brown titanite contains lower concentrations of y ree fe2o3 and zr but somewhat higher al2o3 and nb2o5 uranium concentrations and th u discriminate between brown grains typically 200 400 ppm u all analyses but one have th u between about 0 8 and 2 and colorless grains 10 60 ppm u th u of 0 0 17 in contrast to the zircon u pb age results shrimp u pb data from titanite indicate multiple growth episodes in brown grains oscillatory zoned cores formed at 443 6 ma whereas white in bse cross cutting zones are 425 9 ma colorless grains and overgrowths on brown grains yield an age of 265 8 ma using the total pb method or 265 5 ma using the weighted average of the 206pb 238u ages however empa chemical data identify zoning that suggests that this colorless titanite may preserve three growth events oscillatory zoned portions of brown titanite grains are igneous in origin white cross cutting zones probably formed during a previously unrecognized event that caused partial dissolution of earlier titanite and reprecipitation of a slightly younger generation of brown titanite colorless titanite replaced and grew over the magmatic titanite during the permian alleghanian orogeny these isotopic data indicate that titanite like zircon can contain multiple age components coupling shrimp microanalysis with empa and sem results on dated zones as presented in this study is an efficient and effective technique to extract additional chronologic data to reveal the complexities of igneous crystallization and metamorphic growth

microseismic and precursor analysis of high stress hazards in tunnels a case comparison of rockburst and fall of ground abstract in rock engineering microseismic monitoring technology has been extensively applied for the interpretation and forecast of rockburst hazards however highly stressed hard rocks could suffer dynamic geological hazards rockburst and gravity driven geological hazards fall of ground both of which have distinct developmental processes and precursory features that await comprehensive exploration hence in this study we adopted microseismic monitoring and an advanced method based on the source parameters of seismic energy seismic moment and apparent stress the ems method the source parameter space was constructed to ascertain microseismic events as stress adjusting deformation driven or energy releasing type the evolution of the event type and the microseismic path precisely revealed the characteristics of the hazard development in a case study of a deeply buried tunnel we analyzed the process by which high stress hazards occur using the proposed method and distinguished between the respective microseismic characteristics of the rockburst and fall of ground in the development and occurrence stages finally we proposed the key precursory of rockburst and fall of ground in high stress rock masses while deformation driven events increase notably in rockburst stress adjusting events are dominant in fall of ground overall this study could facilitate precise interpretation and warning about different high stress hazards and provide effective measures to curb the development of hazards

origin and petrogenetic implications of tourmaline rich rocks in the sierra nevada betic cordillera southeastern spain tourmaline rich rocks up to 60 tourmaline associated with low medium grade metamorphic assemblages occur in the sierra nevada area betic cordillera southeastern spain tourmaline appears in a variety of forms 1 stratiform tourmalinites 2 quartz tourmaline nodules 3 porphyroclasts in felsic orthogneisses and 4 disseminations in psammopelitic metasediments and gneisses tourmaline within these lithologic groups exhibits textural and chemical variations that reflect complex premetamorphic growth under open system conditions and subsequent changes due to alpine regional metamorphism microprobe analyses of the tourmalines reveal a wide compositional variation between schorl and dravite end members with variable contents of x site vacancies av 0 084 0 225 apfu ca av 0 095 0 269 apfu and excess of al up to 6 588 apfu compared with the theoretical value of 6 in ideal schorl and dravite the amount of ca may be significant in porphyroclasts from the gneisses fe fe mg ratios for tourmalines in tourmalinites metasediments and gneisses range from 0 34 to 0 95 0 16 to 0 92 and 0 28 to 0 97 respectively na na ca ratios are also variable mostly ranging from 0 5 to 0 9 many of the tourmalines have complex chemical and colour zoning patterns including significant fluctuations in al fe mg na ca ti and f based on petrographic and chemical data three generations of tourmaline have been established the first generation corresponds to magmatic postmagmatic tourmaline that is represented by tourmaline porphyroclasts within the orthogneisses the second generation of tourmaline formed during tourmalinization of psammopelitic rocks giving rise to tourmalinites the third generation of tourmaline is represented by cellular textures pale reaction rims and overgrowths developed during the alpine regional metamorphic overprint d 2002 elsevier science b v all rights reserved

progressive mitigation method of rock bursts under complicated geological conditions abstract jingxi coalfield which is called china s geological encyclopedia has a complicated geological condition as one its representative mines muchengjian mine has witnessed nearly thirty rock bursts in the past decade considering geological structures the in situ stress state and the burst proneness of coal one typical mining area in muchengjian mine is selected for analysis where nearly one third of rock bursts occurred this analysis lays the foundation for selecting mitigation strategies results indicate that the blasting disturbance plays an important role in the intensity and the scale of these rock bursts jingxi coalfield has three types of rock burst mechanisms i high in situ stress rock burst ii high mining induced stress rock burst and iii high in situ stress plus high mining induced stress rock burst therefore we follow two guidelines for rock burst control one is to mitigate the high stress concentration and the second is to control the disturbance stress on the basis of these two guidelines we designed a progressive mitigation method of rock bursts pmmrb first the weak disturbance destress techniques e g large diameter drilling water infusion are applied to weaken the strength and the burst proneness of coal and to expand crack zones to reduce the stress concentration and second the strong disturbance destress blasting is applied if the release of stress concentration is not sufficient pmmrb is adopted in a similar mining area with a higher in situ stress which indicates that pmmrb is applicable to the control of rock bursts and the reduction of rock burst intensity

geophysical evaluation of effectiveness of blasting for roof caving during longwall mining of coal seam deep longwall mining of coal seams is made in the upper silesian coal basin uscb under complicated and mostly unfavourable geological and mining conditions usually it is correlated with rockburst hazard mostly at a high level one of the geological factors affecting the state of rockburst hazard is the presence of competent rocks in the roof of extracted coal seams so rock falling behind the longwall face does not occur and hanging up of roof rocks remains the long lasting absence of caving may lead to an occurrence of high energy tremor in the vicinity of the longwall face roof caving behind the longwall face may be forced by blasting the column of explosives is then located in blastholes drilled in layers of roof rocks e g sandstones behind the longwall face in this article a characterization of tremors initiated by blasts for roof caving during underground extraction of coal seam no 507 in one of the collieries in the uscb has been made using three independent methods by the basic seismic effect method the effectiveness of blasting is evaluated according to the seismic energy of incited tremors and mass of explosives used according to this method selected blasts gave extremely good or excellent effect an inversion of the seismic moment tensor enables determining the processes happening in the source of tremors in the foci of provoked tremors the slip mechanism dominated or was clearly distinguished the expected explosion had lesser significance or was not present by the seismic source parameters analysis among other things an estimation of the stress drop in the focus or its size may be determined the stress drop in the foci of provoked tremors was in the order of 105 pa and the source radius according to the brune s model varied from 44 3 to 64 5 m the results of the three mentioned methods were compared with each other and observations in situ in all cases the roof falling was forced

the seismic source parameters of tremors provoked by long hole destress blasting executed during the longwall mining of a coal seam under variable stress conditions the underground mining of coal seams in the upper silesian coal basin is carried out at great depths and mostly in the presence of remnants or edges of other surrounding coal seams i e under the condition of high stress level in the rock mass therefore this mining is accompanied by rockburst hazard and suitable preventive action is required long hole destress blasting plays an important role and is commonly applied in rockburst prevention in underground hard coal mines estimated blasting effectiveness is important when designing rockburst prevention it is commonly estimated on the basis of the seismic energy of a provoked tremor the seismic source parameters have already been considered for this purpose additional information about the effects of long hole destress blasting could be contemplated in the planning of active rockburst prevention the seismic source parameters of tremors provoked by long hole destress blasting have been calculated and are presented in this article destress blasts were performed during the longwall mining of coal seam no 506 in one of the hard coal mines in the upper silesian coal basin they were executed from the longwall face in order to destress the rock mass ahead of it parameters of the blasts were variable and they were modified according to geological and mining conditions and the observed level of rockburst hazard the seismic source parameters have been determined for tremors provoked directly after firing explosives and for tremors occurring in the waiting time and they have been compared with each other

numerical investigation of load shedding and rockburst reduction effects of top coal caving mining in thick coal seams abstract by comparing the overburden structure characteristics and the distribution of stresses around roadways and coalfaces in slice mining and top coal caving mining in thick coal seams this study analysed the effects of the two mining methods on rockburst prevention furthermore by using flac3d numerical simulation this research studied the distribution of surrounding rock stress in the first mining panels subsequent panels solid coal roadways and gob side roadways and the influence of parameters including mining height bottom coal and coal seam thickness on stresses in the surrounding rocks on this basis the effects of load shedding and rockburst reduction of top coal caving mining of thick coal seams were summarised and verified through field investigation the results show that compared with slice mining overburden structures in top coal caving mining of thick coal seams weakened the stress concentration in surrounding rocks resulting in lower peak values but wider ranges of advanced abutment stress and side abutment stress in panels the point of peak stress was observed deeper into the coal masses with the increase of mining height and the decrease of bottom coal thickness the stress concentration around roadways and coalfaces decreased rapidly and then tended to be stable therefore top coal caving mining can reduce the stress concentration around roadways and coalfaces to decrease rockburst risk while mining thick coal seams top coal caving mining needs to be conducted preferentially over a reasonable range of mining heights field practice in xing an and junde mines revealed that the top coal caving mining induced a lower rockburst frequency over a smaller range and with lower intensity which validated the effects of load shedding and rockburst reduction of the proposed mining method

formation of al rich titanite catisio4o caalsio4oh reaction rims on ilmenite in metamorphic rocks as a function of fh2o and fo2 abstract reaction rims of titanite on ilmenite are described in samples from four terranes of amphibolite facies metapelites and amphibolites namely the tamil nadu area southern india the val strona area of the ivrea verbano zone northern italy the bamble sector southern norway and the northwestern austroalpine otztal complex the titanite rims and hence the stability of titanite catisio4o and al oh titanite i e vuaganatite hypothetical end member caalsio4oh are discussed in the light of fh2o and fo2 buffered equilibria involving clinopyroxene amphibole biotite ilmenite magnetite and quartz in the systems cao feo fe2o3 tio2 sio2 h2o o2 cftsh and cao feo fe2o3 al2o3 sio2 h2o o2 cfash present in each of the examples textural evidence suggests that titanite reaction rims on ilmenite in rocks from tamil nadu val strona and the bamble sector originated most likely due to hydration reactions such as clinopyroxene ilmenite quartz h2o amphibole titanite and oxidation reactions such as amphibole ilmenite o2 titanite magnetite quartz h2o during amphibolite facies metamorphism or as in the case of the otztal complex during a subsequent greenschist facies overprint overstepping of these reactions requires fh2o and fo2 to be high for titanite formation which is also in accordance with equilibria involving al oh titanite this study shows that in addition to p t bulk rock composition and composition of the coexisting fluid fo2 and fh2o also play an important role in the formation of al bearing titanite during amphibolite and greenschist facies metamorphism

particle velocity generated by rockburst during exploitation of the longwall and its impact on the workings as a consequence of geomechanical and geotechnical conditions and also anthropogenic activities in mines of the ostrava karvina coal basin czech republic rockbursts have been recognized to be a serious seismic risk therefore local as well as regional monitoring arrays were deployed there in order to investigate the actual seismic activity continually one of the essential parameters which was observed at the seismic stations situated in situ was the particle velocity of p and s waves the aim of this paper is to derive some empirical dependences by determining the decrease of seismic wave amplitudes with distance from rockburst foci seismic energy local magnitude co ordinates of seismic stations rockburst foci and positions where damage to workings occurred were employed as additional imput moreover the degree of this damage was tested based on the values of particle velocity and simultaneously stress due to the loading of the workings by the stress wave was also calculated

large volume loss during cleavage formation hamburg sequence pennsylvania green reduction spots in red slate of the hamburg sequence exposed near shartlesville pennsylvania have axial ratios of 1 42 1 0 0 28 on the limbs of near isoclinal folds and 1 0 0 79 0 41 in fold hinge zones conodont cusps and denticles within the reduction spots have been brittlely pulled apart and give independent measures of extension in various directions comparison of conodont extensions with reduction spot shapes on limbs and hinges indicates that sedimentary compaction of 44 preceded the tectonic strain associated with cleavage formation this strain having identical maximum extensions but greater shortening in fold hinges as compared to limbs was characterized by 41 extension in x no change in y 50 to 59 shortening in z and 29 to 42 tectonic volume loss the general lack of directed overgrowths on grains reflects the large volume loss and contrasts with other slates where deformation was an almost constant volume process and extension in x compensated for shortening in z

stability of high al titanite from low pressure calcsilicates in light of fluid and host rock composition titanite of variable al and f content was found in granulite to amphibolite facies calcsilicates in central dronning maud land antarctica the highest observed al content corresponds to an xal 5 al al 1 ti of 0 53 previously such high values of xal were reported from high pressure rocks but the titanite of this study is from a lowpressure terrain the compositional variations in titanite can be described for all samples by a set of three linearly independent exchange vectors added to the catisio5 endmember titanite in most rocks these vectors are al 1f1ti21o21 t i 20 25m0 25o21oh1 and oh1f21 in one sample the ti20 25m0 25o21oh1 vector is replaced by a si20 25m0 25o21oh1 vector the actual amount of exchange along these vectors and therefore the amount of al in titanite depends on p and t on the composition of the coexisting fluid phase in terms of its h2o hf fugacity ratio and on host rock composition in terms of al2o3 tio2 activity ratio it is inferred that in suitable chemical environments high al titanite is stable over a wide p t range therefore the al content of titanite should not be used in geothermobarometry even qualitatively additionally because of the coupled substitutions al1f1ti21o21 and al1oh1ti21o21 the concentration of f in titanite is strongly dependent on the host rock chemistry this rules out the easy use of titanite as a monitor of fluid composition

from permo triassic lithospheric thinning to jurassic rifting at the adriatic margin petrological and geochronological record in valtournenche western italian alps abstract slices of polycyclic metasediments marbles and meta cherts are tectonically amalgamated with the polydeformed basement of the dent blanche tectonic system along a major alpine shear zone in the western alps becca di sale area valtournenche valley a combination of techniques structural analysis at various scales metamorphic petrology geochronology and trace element geochemistry was applied to determine the age and composition of accessory phases titanite allanite and zircon and their relation to major minerals the results are used to reconstruct the polyphase structural and metamorphic histories comprising both pre alpine and alpine cycles the pre alpine evolution is associated with low pressure high temperature metamorphism related to permo triassic lithospheric thinning in meta cherts microtextural relations indicate coeval growth of allanite and garnet during this stage at 300 ma textures of zircon also indicate crystallisation at ht conditions ages scatter from 263 to 294 ma with a major cluster of data at 276 ma in impure marble u pb analyses of titanite domains with variable al and f contents yield apparent 206pb 238u dates range from permian to jurassic chemical and isotopic data suggest that titanite formed at permian times and was then affected by extension related fluid circulation during the triassic and jurassic which redistributed major elements al and f and partially opened the u pb system the alpine cycle lead to early blueschist facies assemblages which were partly overprinted under greenschist facies conditions the strong alpine compressional overprint disrupted the pre alpine structural imprint and or reactivated earlier structures the pre alpine metamorphic record preserved in these slices of metasediments reflects the onset of the permo triassic lithospheric extension to jurassic rifting

late proterozoic to early palaeozoic tectonism in dronning maud land antarctica supercontinental fragmentation and amalgamation the mid proterozoic early palaeozoic tectonic development of western dronning maud land is examined in the light of recent proposals that suggest geological continuity between laurentia and gondwana during the middle proterozoic the sweat hypothesis gondwana amalgamation from the remaining constituents followed fragmentation and rifting of laurentia from this supercontinent culminating in a late cambrian orogeny at c 500 ma the mid proterozoic early palaeozoic tectonic development of western dronning maud land was significantly different to that observed in the transantarctic mountains and the c 500 ma event in particular is characterized by 1 a regional isotopic resetting event at c 470 ma 2 scarce coeval magmatism comprising only one major intrusion of alkaline affinity and volumetrically small s type granitic sheets derived from local anatexis of gneisses 3 structural deformation considerably less intense than during the preceding kibaran 1100 ma orogeny comprising relatively open to gentle folding 4 reactivation of thrusting initiated during the kibaran orogeny with associated metasomatism it is concluded that the effects of the late cambrian c 500 ma event are consistent with crustal thickening through large scale underplating rather than subduction related processes as seen in the ross orogeny of the transantarctic mountains it is also concluded that gondwana amalgamation occurred along suture lines not currently exposed in outcrop in dronning maud land these data neither contradict nor support the sweat hypothesis as currently argued

shales at all scales exploring coupled processes in mudrocks abstract fine grained sedimentary rocks namely mudrocks including their laminated fissile variety shales make up about two thirds of all sedimentary rocks in the earth s crust and a quarter of the continental land mass organic rich shales and mudstones are the source rocks and reservoirs for conventional and unconventional hydrocarbon resources mudrocks are relied upon as natural barriers for geological carbon storage and nuclear waste disposal consideration of mudrock multi scale physics and multi scale spatial and temporal behavior is vital to address emergent phenomena in shale formations perturbed by engineering activities unique physical characteristics of shales arise as a result of their layered and highly heterogeneous and anisotropic nature low permeability fabric compositional complexity and nano scale confined chemical environments barriers of lexicon among geoscientists and engineers impede the development and use of conceptual models for the coupled thermal hydraulic mechanical chemical biological thmcb processes in mudrock formations this manuscript reviews the thmcb process couplings resulting emergent behavior and key modeling approaches we identify future research priorities in particular fundamental knowledge gaps in understanding the phase behavior under nano scale confinement coupled chemo mechanical effects on fractures the interplay between physical and chemical processes and their rates and issues of non linearity and heterogeneity we develop recommendations for future research and integrating multi disciplinary conceptual models for the coupled multi scale multi physics behavior of mudrocks consistent conceptual models across disciplines are essential for predicting emergent processes in the subsurface such as self focusing of flow time dependent deformation creep fracture network development and wellbore stability

combined apatite fission track and single grain apatite u th he ages from basement rocks of central dronning maud land east antarctica possible identification of thermally overprinted crustal segments abstract apatite fission track ft and single grain u th he ages from four vertical profiles in central dronning maud land east antarctica range from 312 20 ma to 135 11 ma and 304 28 ma to 104 8 ma respectively the combined age data allows to discriminate between undisturbed cooled due to exhumation and thermally overprinted crustal blocks profiles at the zwieselhohe and the conradgebirge revealed unusual apatite ft vs elevation relationships and u th he ages older than the corresponding central apatite ft ages possibly providing evidence for a jurassic thermal overprint most probably jurassic magmatism and associated advective heating led to total annealing of the apatite fission tracks but helium only partially diffused the model developed in this paper suggests that the u th he ages from the zwieselhohe and conradgebirge profiles are in part relicts of the pre jurassic cooling history two thermally undisturbed vertical profiles are used to record the long term cooling history of central dronning maud land time temperature paths derived from modelled apatite ft data of these profiles revealed two phases of accelerated cooling during the late carboniferous and the early jurassic both phases are followed by slow cooling which is also documented by the spread in apatite u th he single grain ages the cooling at the end of the carboniferous is most probably related to far field effects associated to the prevailing convergent tectonics during the initial separation between east antarctica and mozambique erosion along an evolving rift shoulder caused the jurassic cooling denudation of the basement was simultaneous with volcanism with both pre dating c 20 10 ma sea floor spreading in the riser larsen sea c 155 ma post jurassic cooling was restricted to the lowest temperature sensitivity of both methods combined inverse modelled apatite ft data and forward modelled u th he data suggest an eocene oligocene cooling step possibly related to the flexural isostatic response to the development of ice sheets

calculation of co 2 activities using scapolite equilibria constraints on the presence and composition of a fluid phase during high grade metamorphism thermodynamic and phase equilibrium data for scapolite have been used to calculate co2 activities aco2 and to evaluate the presence or absence of a fluid phase in high grade scapolite bearing meta anorthosite granulites calc silicates and mafix xenoliths the assemblage scapolite plagioclase garnet quartz may be used to calculate or limit aco2 by the reaction meionite quartz grossular anorthite co2 granulites from four high grade terranes grenville province canada sargut belt india furua complex tanzania bergen arcs norway yield aco2 0 4 1 with most 0 7 for scapolite bearing granulites from the furua complex in which aco2 0 9 calculated h2o activities ah2o based on phlogopite dehydration equilibria are uniformly low 0 1 0 2 the aco2 calculated for meta anorthosite from the grenville province ontario ranges from 0 2 to 0 8 for grenville meta anorthosite also containing epidote the ah2o calculated from clinozoisite dehydration ranges from 0 2 to 0 6 calc silicates from the grenville sargur and furua terranes mostly yield aco2 1 the calculated fluid activities are consistent with metamorphism 1 in the presence of a mixed co2 h2o fluid phase in which co2 is the dominant fluid species but other c o h s species are minor 2 in the absence of a bulk fluid phase fluid absent metamorphism or 3 in the presence of a fluid bearing melt phase the results for many granulites and grenville meta anorthosite are consistent with the presence of a co2 rich mixed co2 h2o fluid phase in contrast the relatively restricted and low values of aco2 for calc silicates require an h2o rich fluid or absence of a fluid phase during metamorphism the range of values for xenoliths are most consistent with absence of a fluid phase the primary implication of these results is that a co2 rich fluid accounts for the reduced ah2o in scapolite bearing granulites however scapolite may be stable with a wide range of fluid compositions or in the absence of a fluid phase and the presence of scapolite is not a priori evidence of a co2 rich fluid phase in addition close association of scapolite free mafic granulites with scapolite bearing granulites having identical mineral compositions in the furua complex and the absence of scapolite from most granulite terranes implies that a co2 rich fluid phase is not pervasive on an outcrop scale or common to all granulite terranes

reduction and prediction of sandstone reservoir potential jurassic north sea porosity permeability mineralogical and depth data for two north sea jurassic sandstone sequences were analysed both sequences show statistically significant negative correlations between present burial depth and porosity the influence of secondary porosity creation is subordinate to that of the general decline in porosity for a given burial depth sequence a is on average a little more porous about 3 than b however for a given porosity sequence a displays a permeability 1 3 orders of magnitude greater than b the large permeability difference between a and b is a function of authigenic mineralogy the only significant cement within the reservoir intervals of sequence a is quartz sequence b contains authigenic clays quartz and subordinate carbonate the abundant authigenic clay in b severely reduced permeability in both instances the cements are products of burial and were precipitated from pore waters expelled from shales during compaction the expelled pore waters were both acidic and rich in solutes a product of reactions between maturing organic matter clays and iron oxides the difference in authigenic mineralogy between the sequences was caused by the reaction between pore waters and sandstones with different detrital mineral compositions thus the present reservoir quality is a product of burial and of the reactions between evolving pore fluids and minerals in the sandstone

diagenetic patterns in eolian coastal sabkha reservoirs of the solimoes basin northern brazil abstract the jurua formation carboniferous solimoes basin is the largest gas reservoir in brazil a petrologic study of the jurua sandstones from the urucu area revealed the diagenetic evolution and controls on the quality of the main reservoirs as well as the relationships among diagenetic patterns depositional facies and stratigraphic unit boundaries the sandstones mudrocks evaporites and dolostones were deposited within a coastal sabkha environment with pervasive eolian reworking under increasing marine influence and a hot and dry climate eolian dune and sandsheet sandstones are the best reservoirs four stacked drying wetting upward cycles were identified with sabkha facies at the base overlain by eolian sandsheet and dune deposits which in turn are overlain again by sabkha deposits commonly eroded by the next cycle the sandstones are mostly subarkoses and arkoses blocky dolomite is the most abundant diagenetic constituent in the non eolian sandstones its distribution shows no relationship with depositional cycle limits microcrystalline pore filling and pore lining dolomite is more abundant in the eolian sandstones stable o and c dolomite isotope values presented by these dolomite cements indicate initial precipitation from a dominantly marine fluid at low temperatures 18ovpdb values mostly between 1 and 5 13cvpdb values from 3 to 2 with increasing contribution of organic matter decarboxylation at higher temperatures during burial 18ovpdb values between 12 and 6 13cvpdb from 3 5 to 8 9 chemical compaction through intergranular and stylolitic pressure dissolution and cementation by quartz overgrowths are more intense in the non eolian sandstones poikilotopic patchy post compactional anhydrite cementation is more abundant in the eolian sandstones but pervasive only close to the contacts with interbedded sabkha evaporites abundant anhydrite and quartz cementation along the base of depositional cycles contributed to the strong compartmentalization among the reservoir sub units but not to introduce internal heterogeneity to the reservoirs conversely dolomite cementation substantially affected the internal porosity and permeability heterogeneity by generating laterally extensive barriers to fluid flow

aluminous titanite sphene from the eclogite zone south central tauern window austria abstract highly aluminous titanite with al 2 o 3 contents up to 14 wt 50 of the caalsio 4 f oh end member occurs in siliceous dolomites from the eclogite zone south central tauern window austria 140 chemical analyses of titanites from 13 samples from the eclogite zone and adjacent tectonic units reveal that al is incorporated into titanite primarily by the mechanism ti o al f oh there is also a strong positive correlation between al and f content of these titanites indicating that the combined substitution is enhanced by the presence of f al contents of titanite vary between tectonic units with the most aluminous varieties occurring in the high pressure eclogite zone variations also occur from sample to sample within a single tectonic unit and both between and within individual grains in a single sample complex zoning with sharp chemical and optical discontinuities is observed with al 2 o 3 variations of up to 6 wt within a single sample individual grains generally have low al cores mantled by high al zones and rimmed by low al edges it is suggested that the incorporation of al into titanite is favoured by high p low t and high f activity

accessory titanite an important carrier of zirconium in lamprophyres the chemical composition of minerals from a suite of variscan lamprophyres kersantite minette spessartite and vogesite from the saxothuringian zone of the variscan orogen germany were investigated by electron microprobe these lamprophyres usually contain small grains 50 m of zr bearing titanite as the only primary mineral containing traceable zirconium a late stage residual alkaline melt within the lamprophyric magma is considered to have crystallized the zr rich titanite the titanite typically has euhedral zr rich cores mantled by zr poor overgrowths this compositional change is explained by rapid decrease of temperature during magma uprise and emplacement relatively high zr contents and compositional and textural heterogeneities e g syenitic schlieren veins and globules within the lamprophyric host rocks are evidence of magma mixing incorporation of zr into titanite apparently takes place as a coupled substitution ti4 al3 zr4 fe3 rather than as a simple 1 1 replacement of ti by zr a zro2 content of about 6 wt equivalent to 0 10 atoms per formula unit zr is implied as the upper concentration limit in titanite locally occurring higher values are attributed to tiny inclusions of secondary zr phases in carbonate rich portions of lamprophyres titanite is transformed into an unindentified tio2 phase high al f titanite xal up to 0 54 restricted in occurrence to the contact between tonalite porphyry and kersantite formed under the conditions of high fluorine activity connected with the rhyolitic magmatism the results show that the zr budget of lamprophyres and possibly of other mafic igneous rocks lacking zircon is strongly governed by titanite element distribution patterns in titanite are a key to the better understanding of magmatic evolution and petrogenesis of lamprophyres

thermal and baric evolution of garnet granulites from sri lanka abstract garnet granulites from sri lanka preserve textural and chemical evidence for prograde equilibration at temperatures of at least 700 750 c and pressures in the vicinity of 6 8 kbar associated strain patterns suggest prograde metamorphism occurred during and immediately following an episode of crustal thickening with the prograde p t conditions probably reflecting a combination of the conductive and advective transport of heat at the mid levels of tectonically thickened crust the occurrence of prograde wollastonite provides evidence for internally buffered fluid compositions or fluid absent conditions during peak metamorphism and precludes pervasive advection of a co2 rich fluid the advective heat component is therefore likely to have been provided by the transport of silicate melt intricate symplectitic textures record partial re equilibration of the garnet granulites to lower pressures 4 6 kbar at high temperatures 600 750 c and testify either to the erosional denudation of the overthick crust prior to significant cooling i e quasi isothermal decompression or to a subsequent static heating possibly of early palaeozoic age pan african the metamorphic history of the sri lankan granulites is compared with high grade terrains in the neighbouring fragments of gondwana with the emphasis on similarities with proterozoic granulites of the east antarctic craton

an attempt to determine the seismic moment tensor of tremors induced by destress blasting in a coal seam to achieve knowledge about processes occurring in provoked tremors a share of shear component in full smt solution indicate effectiveness of blastings smt inversion could be valuable to blasting effectiveness designation

comparison of rockburst occurrence during extraction of thick coal seams using top coal caving versus slicing mining methods in recent years rockbursts have occurred frequently during the mining of thick coal seams in china use of the top coal caving or slicing mining method to extract these thick seams may result in d

energy components in rock blasting abstract ten production blasts and one single hole confined blast have been monitored in two quarries in order to assess the measurable forms of energy in which the energy delivered by the explosive is transformed in rock blasting the seismic field from seismographs readings the initial velocity of the blasted rock face obtained from high speed video camera records and the fragment size distributions from image analysis of the muckpile material are used to determine the seismic wave energy the kinetic energy and the fracture energy respectively transferred in the blasting process the blasting data and the methods of calculation of the energy terms from those are described in detail heat of explosion and useful work to 100 mpa have been used as descriptions of the energy of explosives the maximum total energy measured accounts for not more than 26 of the available explosive energy if this is rated as the heat of explosion though lower figures are usually obtained the values measured for each of the energy components range from 2 to 6 of the total energy available for the fragmentation energy 1 3 for the seismic energy and 3 21 for the kinetic energy for the confined shothole the seismic energy was 9 of the heat of explosion the uncertainty of the calculated energies is analyzed from the variability of the measured data particularly important influential parameters are the treatment of the fines tail of the fragment size distribution in the determination of the fragmentation energy and the use of p or s wave velocity values and whether these are determined from in situ or from laboratory measurements in the calculation of the seismic energy

dating deposition and low grade metamorphism by in situ upb geochronology of titanite in the paleoproterozoic timeball hill formation southern africa abstract titanite coexists with zircon in a felsic tuff in the paleoproterozoic timeball hill formation southern africa two generations of titanite are preserved euhedral brown crystals with apatite inclusions and colorless matrix filling cement the brown titanite has elevated u th and fe and low al consistent with a magmatic origin whereas the colorless titanite has higher al and f contents suggestive of a metamorphic paragenesis in situ shrimp geochronology of zircons extracted from a polished thin section of the tuff bed suffer from inheritance and pb loss and yield an imprecise date 2259 35 ma whereas coexisting brown titanites give a weighted mean 207pb 206pb age of 2278 7 ma this date is consistent with u pb zircon ages for tuffs in the same stratigraphic unit from a nearby drill hole the brown titanite is interpreted to be magmatic and to provide a reliable estimate for the age of deposition in situ u pb dating of matrix filling titanite cement from the same stratigraphic interval yields an age of 2145 12 ma which corresponds with previous estimates for a low grade tectonothermal event in southern africa our results demonstrate that titanite is a versatile chronometer that can be used to constrain depositional ages and those of low grade metamorphism thus increasing the number of sedimentary rocks that can be dated and elucidating the low temperature geological history of depositional basins

redistribution of hfse elements during rutile replacement by titanite titanite growth at the expense of rutile during retrograde hydration of eclogite into amphibolite is a common phenomenon we investigated an amphibolite sample from the tromso eclogite facies terrain in northern norway to gain insight into the trace element distribution between rutile and titanite during incomplete resorption of the rutile by titanite patchy compositional zoning of al ti and f in titanite relates to the presence of a fluid with variable ti al and or f during its growth laser ablation icp ms and electron microprobe data for high field strength elements hfse nb zr ta and hf of rutile resorbed by titanite indicate a pronounced enrichment of these elements in the rim of a large single rutile crystal 8 mm and a systematic decrease towards uniform hfse contents in the large core hfse contents of smaller rutile grains 0 5 mm and rutile inclusions 100 m in the titanite overgrowth are similar or higher than in the rims of large rutile crystals element profiles from the rim inward demonstrate that hfse enrichment in rutile is controlled by diffusion hfse ratios in diffusion altered rutile show systematic variations compared with the uniform core composition of the large rutile modelling of zr and nb diffusion in rutile indicates that diffusion coefficients in rutile in fluid dominated natural systems must be considerably higher than those determined experimentally at 1 bar in dry systems variations of hfse contents in the newly formed titanite show no systematic spatial distribution hfse ratios in titanite and the rims of rutile are different indicating different solid fluid distribution coefficients in these minerals element fractionation by diffusion into the relict rutile and during fluid mediated growth of new titanite could substantially change the hfse budget of these minerals and could affect their use for geochemical tracing and other applications such as zr based geothermobarometry

high temperature metamorphic imprint on calc silicate granulites of rayagada eastern ghats india implication for the isobaric cooling path calc silicate granulites from rayagada north central sector of eastern ghats granulite belt show a wide range of mineral assemblages and chemical compositions which can be grouped as gr i grossular rich garnet wollastonite scapolite calcite clinopyroxene gr ii andradite rich garnet scapolite calcite clinopyr oxene and gr iii scapolite calcite clinopyroxene plagioclase assemblages petrographic features suggest the following several reactions in the cao al2o3 sio2 vapor system mei 4wo cal 3grs qtz 2co2 mei 3wo 2cal 3grs co2 mei 3an cal wo co2 cal qtz mei 5wo 3grs 2qtz co2 an wo grs qtz mei 5cal 3qtz 3grs 6co2 and the following reactions in the cao feo mgo al2o3 sio2 vapor system cpxss scp wo grtss qtz co2 4hd 2cal o2 2adr 2qtz 2co2 cpxss scp grtss cal qtz these reactions have been used to estimate peak t xco2 condition for these granulites a maximum temperature of 920 c has been calculated at an estimated pressure of 9 kbar a t xco2 diagram shows an isobaric cooling from 920 c to 815 c a range of xco2 0 50 at 920 c to 0 25 at 815 c has been observed for gr i calc silicate granulites based on the reaction sequences including coronal garnet forming reactions this sequence is suggestive of internal fluid buffering rather than external fluid influx and the differences in xco2 conditions has been thought to be due to local buffering of fluid phases group ii and gr iii calc silicate granulites on the other hand exhibit relatively lower temperature conditions

quartz types in the upper pennsylvanian organic rich cline shale wolfcamp d midland basin texas implications for silica diagenesis porosity evolution and rock mechanical properties

the origins of granulites a metamorphic perspective although many recent reviews emphasize a uniformity in granulite pressure temperature p t conditions and paths granulites in reality preserve a spectrum of important petrogenetic features which indicate diversity in their modes of formation a thorough survey of over 90 granulite terranes or occurrences reveals that over 50 of them record p t conditions outside the 7 5 1 kbar and 800 50 c average granulite regime preferred by many authors in particular an increasing number of very high temperature 900 1000 c terranes are being recognized both on the basis of distinctive mineral assemblages and geothermobarometry petrogenetic grid and geothermobarometric approaches to the determination and interpretation of p t histories are both evaluated within the context of reaction textures to demonstrate that the large range in p t conditions is indeed real and that both near isothermal decompression itd and near isobaric cooling ibc p t paths are important amphibolite granulite transitions promoted by the passage of co 2 rich fluids as observed in southern india and sri lanka are exceptional and not representative of fluid related processes in the majority of terranes it is considered on the contrary that fluid absent conditions are typical of most granulites at or near the time of their recorded thermal maxima itd granulites are interpreted to have formed in crust thickened by collision with magmatic additions being an important extra heat source erosion alone is not however considered to be the dominant post collisional thinning process instead the itd paths are generated during more rapid thinning 1 2 mm yr exposure related to tectonic exhumation during moderate rate or waning extension ibc granulites may have formed in a variety of settings those which show anticlockwise p t histories are interpreted to have formed in and beneath areas of voluminous magmatic accretion with or without additional crustal extension ibc granulites at shallow levels very rapid 5 mm yr extensional thinning subsequent to collision it is suggested that the preservation of ibc paths rather than itd paths in many granulites is primarily related to the rate and timescale of extensional thinning of thickened crust and that hybrid itd to ibc paths should also be observed most ibc granulites and probably many itd granulites have not been exposed at the earth s surface as a result of the tectonic episodes which produced them but have resided in the middle and lower crust for long periods of time 100 2000 ma following these events the eventual exhumation of most granulite terranes only occur through their incorporation in later tectonic and magmatic events unrelated to their formation

ultrahigh pressure uhp low al titanites from carbonate bearing rocks in dabieshan sulu uhp terrane eastern china titanites previously reported from high pressure rocks commonly contain high al and f contents this finding has led previous workers to conclude that high al and f in titanite can expand its stability field to high pressure and ultrahigh pressure uhp conditions in this study a coesite inclusion was identified in titanite of aragonite and jadeite bearing gneiss from the dabieshan uhp metamorphic terrane of eastern china we also found uhp titanite in carbonate bearing garnet clinopyroxenite from the sulu uhp terrane interestingly both types of the uhp titanite mentioned above contain low al and f contents therefore our data indicate that the high al and f contents are not necessary criteria for stabilizing titanite to uhp conditions it is inferred that the uhp titanite formed via the reaction tio 2 caco 3 sio 2 catisio 5 co 2 and that the presence of the uhp assemblage aragonite rutile clinopyroxene coesite in the host rock and a very low x co 2 value in the coexisting fluid are crucial conditions for the formation of these uhp titanites

identification and tectonic implications of nano particle quartz 50 nm by synchrotron x ray diffraction in the chelungpu fault gouge taiwan abstract to determine the ultrafine nano scale grains in a fault gouge the chelungpu fault gouge was sampled and analyzed it was separated into different particle size ranges and was analyzed by synchrotron x ray diffraction and transmission electron microscopy the minerals of gouge are predominantly composed of quartz plagioclase smectite illite chlorite and kaolinite the mineral association of

a new protective destressing technique in underground hard coal mining abstract mining induced stress accumulates in the immediate excavation borders to propose a risk of sudden and violent failure in the form of high velocity ejection of rock fragments rockburst has become a major stability problem in hard rock mining as underground operations progress deeper down the earth likewise coalburst exhibits a similar failure mechanism in relatively lower depths due to its low strength but high brittle characteristics commonly stress manipulation techniques have been used to mitigate the risk of coalburst destress blasting offers a fast and significant decrease in stress concentration within the coal seam compared to the alternative destressing techniques stress accumulation shifts away from the excavation face and the fractured zone performs as a cushion between the overstressed region and the working panel this study evaluates the conventional destressing techniques and proposes a novel method based on the simulations of an underground longwall mine located in new south wales australia discontinuous rock media motivated the use of 3 dimensional distinct element method dem for modeling discrete fracture networks dfn were tested in terms of their capability to degrade the rock strength both on lab and field scale simulations later an alternative method was developed to implement the fractured rock mass by eliminating the computational difficulties of dfn destress blasting was evaluated in terms of the location and roof stability measures despite its significance blasting creates a violent and sudden impact on the rock mass which is hard to control coalface undercutting was proposed as a new destressing technique undercut dimensions required for an effective stress free cushion were studied in terms of numerical simulations later a practical tool was developed by adaptive neuro fuzzy inference system anfis in order to predict the effective undercut dimensions finally some practical application guidelines were established for the new method

humite and scapolite bearing assemblages in marbles and calcsilicates of dronning maud land antarctica new data for gondwana reconstructions this study investigates marbles and calcsilicates in central dronning maud land cdml east antarctica the paleogeographic positioning of cdml as part of gondwana is still unclear however rock types mineral assemblages textures and p t conditions observed in this study are remarkably similar to the kerala khondalite belt in india the cdml marbles and calcsilicates experienced a pan african granulite facies metamorphism at c 570 ma and an amphibolite facies retrogression at c 520 ma the highest grade assemblage in marbles is forsterite spinel calcite dolomite in calcsilicates the assemblages are diopside spinel diopside garnet scapolite wollastonite clinopyroxene quartz scapolite anorthite calcite clinopyroxene wollastonite these assemblages constrain the peak metamorphic conditions to 830 20 c 6 8 0 5 kbar and xco2 0 46 during retrogression highly fluoric humite group minerals humite clinohumite chondrodite replaced forsterite and garnet rims formed at the expense of scapolite during reactions with wollastonite calcite or clinopyroxene but without involvement of anorthite metamorphic conditions were about 650 c 4 5 0 7 kbar 0 2 xco2fluid 0 36 and the co existence of garnet clinopyroxene wollastonite and quartz constrains fo2 to fmq 1 5 log units mineral textures indicate a very limited influx of h2o rich fluid during amphibolite facies retrogression and point to significant variations of fluid composition in mm sized areas of the rock gypsum was observed in two samples it probably replaced metamorphic anhydrite which appears to have formed under amphibolite facies conditions the observed extensive anorogenic magmatism anorthosites a type granitoids and the character of metamorphism between 610 and 510 ma suggest that the crustal thermal structure was characterized by a long lived 50 100 ma rise of the crustal geotherm probably caused by magmatic underplating

the pan african event in east antarctica a view from sri lanka and the mozambique belt abstract late pan african 580 550 ma high grade deformation of the sri lankan basement gave rise to a fold and thrust belt the resulting axial planes to upright folds and earlier stretching lineations define a large scale syntaxial bend this syntaxis is attributed to e w shortening and simultaneous sinistral strike slip along a n s trending transcurrent zone located west of sri lanka prior to gondwana break up the resulting geometry is consistent with a corner effect brun and burg 1982 produced by westward indenting of the basement underneath eastern sri lanka during collision in gondwana reconstructions the sinistral strike slip zone fits into the late kinematics of the mozambique belt shackleton 1986 these new structural data constrain the position of sri lanka in gondwana and favour reconstructions in which sri lanka is located near the lutzow holm bay in east antarctica a review of data from adjacent gondwana fragments suggests that the tectonometamorphic evolution of the sri lankan basement is closely related to the interplay between two orogenic belts the mozambique belt and the lutzow rayner belt it is argued that a late event of n s shortening gondwana coordinates in the lutzow rayner belt can be attributed to a pan african tectonometamorphic event in this interpretation the lutzow rayner belt developed in part simultaneously with the mozambique belt reworking an older granulitic basement in the rayner complex

long hole destress blasting for rockburst control during deep underground coal mining abstract the lazy colliery in the ostrava karvina coalfield of the upper silesian coal basin adopted modern longwall technology for an underground extraction of coal seam no 504 this coal seam is located at a cover depth of around 700 m the seam thickness varied from 3 1 m to 5 0 m in the selected longwall panel two overlying coal seams nos 512 and 530 experienced mining at average heights of 58 m and 75 m respectively from the planned working horizon of the seam no 504 the proposed longwall panel was adversely situated below goaf edges of the workings in these two overlying extracted seams an analysis of the inter burden rock mass among these coal seams showed the presence of strong massive strata of sandstones and conglomerates with uniaxial compressive strength values between 70 mpa and 120 mpa the stress is measured at different mining stages by compact conical ended borehole monitoring ccbm a simple laboratory test of the coal sample found a high value of the ratio of the elastic deformation to the total deformation 0 8 indicating the energy storing characteristic prone to burst bump of the coal seam under the existing geo mining conditions of the site a suitable destress blasting long hole drilling and blasting design is adopted to pre fracture the identified competent strata from both gate roads in advance the total length of the panel could be extracted without any bump rockburst after the destress blasting the efficiency of the adopted destress blasting at the different mining stages is evaluated in terms seismic effect se which is calculated through the available seismic monitoring data and weight of the charged explosive a systematic adoption of the destress rock blasting led the 300 m long longwall panel to be smoothly extracted without any further rockbursts

granulites and garnet cordierite gneisses from dronning maud land antarctica abstract the central sector of muhlig hofmannfjellet 3 e 71 s in western dronning maud land east antarctic shield is dominated by large intrusive bodies of predominantly orthopyroxene bearing quartz syenites charnockites metasedimentary rocks are rare however two distinct areas with banded gneiss marble quartzite sequences of sedimentary origin were found during the norwegian antarctic research expedition nare 1989 90 cordierite bearing metapelitic gneisses from two different localities contain the characteristic mineral assemblage cordierite garnet biotite k feldspar plagioclase quartz sillimanite spinel thermobarometry indicates equilibration conditions of about 650 c and 4 kbar associated orthopyroxene garnet granulites on the other hand revealed pressures of about 8 kbar and temperatures of 750 c the earlier granulite facies metamorphism is not well preserved in the cordierite gneisses as a result of excess k feldspar combined with interaction with an h2o rich fluid phase probably released by the cooling intrusives these two features allowed the original high grade k feldspar garnet assemblages to recrystallize as cordierite biotite sillimanite gneisses completely re equilibrating them phase relationships indicate that the younger metamorphic event occurred in the presence of a fluid phase that varied in composition between the lithologies

the current status of titanite rutile thermobarometry in ultrahigh pressure metamorphic rocks the influence of titanite activity models on phase equilibrium calculations abstract titanite an important accessory mineral in ultrahigh pressure uhp rocks commonly deviates significantly from its ideal composition catisio 4 o by the substitution of al and f oh for ti for o this compositional variability of titanite could be used in phase equilibrium calculations if the activity composition relations in al f bearing titanites were sufficiently known experimental investigations by troitzsch and ellis troitzsch u and ellis d j 2002 thermodynamic properties and stability of alf bearing titanite catiosio 4 caalfsio 4 contributions to mineralogy and petrology 142 543 563 and tropper et al tropper p manning c essene e j 2002 the substitution of al and f in titanite at high pressure and temperature experimental constraints on phase relations and solid solution properties journal of petrology 43 1787 1814 derived non ideal mixing models for solid solutions along the join catisio 4 o caalsio 4 f tropper et al troitzsch u and ellis d j 2002 thermodynamic properties and stability of alf bearing titanite catiosio 4 caalfsio 4 contributions to mineralogy and petrology 142 543 563 derived a preliminary regular model in the t range 900 1100 c in which the t dependent interaction parameter w g was negative in contrast troitzsch and ellis troitzsch u and ellis d j 2002 thermodynamic properties and stability of alf bearing titanite catiosio 4 caalfsio 4 contributions to mineralogy and petrology 142 543 563 favored a regular activity model with positive w g the different signs of the interaction parameter strongly influence calculated non ideal titanite activities comparing available simple ideal ionic coupled ionic non coupled ionic activity models with the non ideal models shows that a catisio 4 o calculated with the ideal ionic models is substantially lower at almost all t calculation of two suitable titanite rutile involving equilibria for thermobarometry applied to literature data from rocks from four uhp terranes shows that ideal ionic models yield the best convergence with independently established p estimates although the literature data have to be treated with caution e g retrogression compositional disequilibrium etc the calculations nonetheless indicate that in terms of t estimates high al x al 0 5 titanites yield a large variation of up to 300 c in t and low al x al t estimates this study shows that p and t estimates derived from ideal models and experimentally constrained non ideal models for titanite activity may show large deviations at uhp conditions ranging from 0 05 to 3 0 gpa and up to 300 c therefore the current status of titanite rutile involving thermobarometry allows it only to be applied to al rich x al 0 2 titanites from uhp rocks if independent more robust p t estimates are available until better activity constraints are available it is recommended that the user employ either the ideal coupled ionic model for titanite solid solutions involving mixing on the ti and the o1 site and compare the results to an experimentally derived activity model or adopt a range of different activity models ionic and regular to obtain a range of p t conditions

coal pillar extraction at deep cover with special reference to indian coalfields majority of the developed indian coal seams are lying under strong and massive overlying strata depth of cover of these coal seams standing on pillars varies from 50 to 500 m present pillar extraction depillaring practises of the country have predominantly adopted intermediate mechanisation along with few fully mechanised depillaring faces most of these faces are operating at shallow cover but the existing techno economical conditions of the industry are attracting a fully mechanised depillaring system for deep seated coal pillars which is likely to grow in near future here the circumstances of bord and pillar mining are to face difficult surroundings mainly due to rock mass characteristics and stress conditions of the deep horizon although these two parameters are difficult to be pre assessed accurately a couple of recent experiences of depillaring at deep cover have shown their influence over efficiency and safety of the depillaring a review of pillar extraction practises of other coal producing countries under varying geo mining conditions showed importance of these parameters for the depillaring providing a brief review of underground coal pillar extraction scenario this paper presents geo technical challenges encountered during caving of massive roof strata at two deep indian depillaring faces these two trials experienced problems of a roof instability b barrier pillar instability and c pillar spalling floor heaving in absence of an effective hard roof management approach these problems could simply be dealt up to some extent by improvement in competency of the natural support

precambrian tectonics and crustal evolution in south india about 3 4 ga ago voluminous calc alkaline magmas represented by the granitoid gneisses of southern india were emplaced into a now poorly preserved non continental crust unstable ensialic basins initiated at about 3 0 ga were filled with volcanic and sedimentary rocks up to about 2 6 ga this basement cover sequence was deformed at the close of the archaean first by northward accretion and thickening of several crustal slabs formerly separated by prisms of stable shelf sediments structures produced by this episode were refolded and dislocated by large n s strike slip shear belts to impart intense steep planar fabrics to large volumes of the crust fluids rich in co possibly derived from sedimentary material driven beneath the crustal slabs by the thickening mechanism purged the deep crust of h o to form granulites upward migration of hot h o rich fluids encouraged partial melting at intermediate crustal levels these late archaean tectonic and thermal events began soon after the close of basin f

nature and evolution of metamorphic fluids in the precambrian khondalites of kerala south india abstract the precambrian charnockite khondalite groups of rocks in the kerala region constitute a significant part of the granulite facies terrain of south india the khondalites comprise interlayered garnet biotite and garnet sillimanite gneisses analyses of coexisting mineral pairs from these rocks give temperatures of 869 50 c garnet biotite and 862 75 c garnet cordierite a garnet orthopyroxene thermometer records 644 c for charnockite intercalated with the khondalites fluid inclusion studies show that the early fluids were high density co 2 rich type 0 97 g cm 3 the graphite bearing garnet sillimanite gneisses show traces of ch 4 also the early high density regime was followed by moderate density co 2 0 73 0 75 g cm 3 and mixed co 2 h 2 o 0 70 g cm 3 fluids a dominant aqueous regime with h 2 o densities in the range 0 79 0 57 g cm 3 manifested during the waning stage a combination of data from solid and fluid phases denote that the high density co 2 rich inclusions entrapped at a pressure of 6 1 kbar represent the fluid phase present at or near the peak of metamorphism the delineated fluid evolution path corresponds to the piezothermic array of khondalites and is similar in form to that of the charnockites the array is characterised by high convexity towards the temperature axis which depicts a fast rate of uplift that exceeds the rate of heat transfer

garnet coronas in scapolite wollastonite calc silicates from east antarctica the application and limitations of activity corrected grids calc silicate boudins within proterozoic granulite facies gneisses of the northern prince charles mountains east antarctica preserve a number of reaction textures including garnet coronas between calcite and scapolite garnet quartz coronas between scapolite and wollastonite and between plagioclase and wollastonite calcite quartz intergrowths in wollastonite and calcite plagioclase symplectites in scapolite these textures have been modelled using petrogenetic grids for reactions in the cao al2 o3 sio2 co2 system but with reduced mineral activities to account for additional components in real mineral compositions such fixed composition reduced activity grids are strictly valid only at the point in p t aco2 space where an assemblage last equilibrated and do not show the true positions of reactions away from this point because mineral compositions change with reaction progress in this case however mineral compositions close to end member values and low extents of reaction progress mean that compositional change was limited and the grids are good approximations to true pseudosections over the entire p t aco2 range of interest the grids show that the textures are consistent with near isobaric cooling from about 850 to 700d c at 7 kbar a p t path compatible with thermobarometric studies of other lithologies from the area phase relationships indicate that co2 activities were buffered by the local mineral assemblage during peak and retrograde metamorphism either under fluid absent conditions or within a non pervasive fluid phase previous studies of garnet coronas in scapolite wollastonite calc silicates have used qualitative grids based on limited experimental data to invoke garnet growth during water infiltration at high temperature but the grids used here show that garnet coronas can form on cooling without any need for water influx

reaction textures in calc silicate granulites from the bolingen islands prydz bay east antarctica implications for the retrograde p t path calc silicate granulites from the bolingen islands prydz bay east antarctica exhibit a sequence of reaction textures that have been used to elucidate their retrograde p t path the highest temperature recorded in the calc silicates is represented by the wollastonite and scapolite bearing assemblages which yield at least 760 c at 6 kbar based on experimental results the calc silicates have partially re equilibrated at lower temperatures down to 450 c as evidenced by the successive reactions 1 wollastonite scapolite calcite garnet co2 2 wollastonite co2 calcite quartz 3 wollastonite plagioclase garnet quartz 4 scapolite plagioclase calcite quartz 5 garnet co2 h2o epidote calcite quartz and 6 clinopyroxene co2 h2o tremolite calcite quartz the reaction sequence observed indicates that aco2 was relatively low in the wollastonite bearing rocks during peak metamorphic conditions and may have been further lowered by local infiltration of h2o from the surrounding migmatitic gneisses on cooling fluid activities in the bolingen calc silicates were probably locally variable during the granulite facies metamorphism and large scale co2 advection did not occur a retrograde p t path from the sillimanite stability field c 760 c at 6 kbar into the andalusite stability field c 450 c at 3 kbar is suggested by the occurrence of secondary andalusite in an adjacent cordierite sillimanite gneiss in which sillimanite occurs as inclusions in cordierite

the solubility of fluorite in h2o and h2o nacl at high pressure and temperature abstract the solubility of fluorite in h2o and h2o nacl has been measured at 600 1000 c 0 5 2 0 gpa in a piston cylinder apparatus fluorite dissolves congruently at all conditions investigated the data indicate that the concentration of fluorite dissolved in h2o is low at 600 c and 0 5 gpa 0 0014 mol kg h2o but increases strongly with temperature t and pressure p to 0 247 mol kg h2o at 1000 c 2 gpa the data were fit with the equation log mcaf2 6 587 2 774p1 2 2 266 10 3 4 699 10 4p t where mcaf2 is molality of caf2 t is in kelvin and p is in gpa fluorite solubility was also measured in h2o nacl fluids at 800 c and 1 0 gpa results indicate a strong increase in dissolved fluorite concentration with increasing nacl content from 0 028 mol kg h2o at xnacl 0 to 1 673 mol kg h2o at xnacl 0 486 where xnacl is the mole fraction of nacl in the fluid the data were fit to mcaf2 0 01035 1 141xnacl 4 694xnacl2 the results indicate that f mobility will be further enhanced by saline brines in high p t igneous and metamorphic environments high f solubility in h2o and h2o nacl in the deep crust and upper mantle can promote mobilization of high field strength elements rare earth elements u and th through transport as f bearing complexes

source analysis of post blasting events recorded in deep copper mine poland seismic and rock burst hazard is a very important factor that has to be considered in seismically active mining areas several different methods are used to decrease seismic activity in mines among others an active prevention method known as destress blasting is considered the most effective technique the aim of this work is to find possible influences of such active prevention on observed seismic activity recorded in the established waiting time after blasts using technological knowledge and seismic data recorded by an underground seismic network we estimated several parameters that characterize sources provoked by blasting works and compared them with the parameters obtained for spontaneous non provoked mining tremors according to our studies the source mechanisms of post blasting seismicity are characterized by the similar non dc part of the full moment tensor whereas the source mechanisms of spontaneous events are not characterized by any specific features on the other hand non provoked seismicity presents lowest values of apparent stress also es to ep ratio suggest some differences between events occurred immediately after blasting up to 30 s and the rest dataset we believe that these parameters could be considered valuable tools supporting established safety time limitations after active prevention

assemblages with titanite catiosio4 ca mg fe olivine and pyroxenes fe mg ti oxides and quartz part ii application in the system cao mgo feo fe2o3 tio2 sio2 equilibria among titanite pyroxene s olivine spinel phase ilmenite and quartz constrain f o2 t a sio2 a tio2 a fe and the compositional variables tife2 fe 23 c a mg fe 1 and consequently mg fe 1 among the silicate and oxide phases these equilibria can provide the framework for a better understanding of relevant titanite bearing natural assemblages in addition such equilibria can constrain the variables that operate during crystallization of igneous and metamorphic rocks titanite bearing assemblages with pyroxene s fe mg ti ilmenite and spinel olivine and quartz are rare in metamorphic rocks but are common in igneous rocks where they are more commonly reported in plutonic than in volcanic rocks probably because at high temperatures titanite cannot coexist with the relative common in volcanic rocks sub assemblage augite orthopyroxene olivine spinel phase ilmenite moreover decreasing pressure and temperature conditions appear to favor titanite thus it is not surprising that titanite is commonly observed in slowly cooled rocks albeit most typically in association with amphibole we argue that the titanite amphibole association is favored by high a h2o and because a h2o typically increases during crystallization of a pluton titanite amphibole and consequently titanite is more common in plutonic than in volcanic rocks we have used a modified version of the program quilf that includes our thermodynamic data for titanite and appropriate titanite bearing assemblages to estimate the equilibrium crystallization conditions of samples from 1 a tonalite from the myoken zan granitic complex in japan 2 the sandwich horizon in the skaergaard intrusion in greenland 3 rhyodacites dacites and andesites from the sajama porquesa and parinacota volcanoes in the andes 4 the fish canyon tuff in colorado and 5 a quartz rich calc silicate gneiss adjacent to the horse creek anorthosite complex in wyoming the calculations suggest that 1 these titanite bearing assemblages crystallized at values of f o2 that ranged from slightly below fmq to more than 3 log f o2 units above fmq at 500 800 c and 2 the stability of titanite is controlled by t f o2 a sio2 and the compositions of the coexisting oxides and silicates

timing of high grade metamorphism early palaeozoic u pb formation ages of titanite indicate long standing high t conditions at the western margin of gondwana argentina 26 29 s concordant u pb ages of c 530 510 ma and c 470 420 ma on titanite from calcsilicate orthogneiss and amphibolite rocks constrain the age of high t metamorphism in the early palaeozoic mobile belt at the western margin of proterozoic gondwana argentina 26 29 s the u pb ages document the time of titanite formation at high t conditions according to the stable mineral paragenesis and occurrence of titanite in the metamorphic fabric the presence of migmatite at all sample sites indicates temperatures were c 650 c titanite formed at similar metamorphic conditions at different times on the regional and on the outcrop scale the titanite crystals preserved their u pb isotopic signatures and chemical composition under ongoing upper amphibolite to granulite facies temperatures different thermal peaks or deformations are only detected by the different u pb ages and not by changes in the mineral paragenesis or metamorphic fabric of the samples the range of u pb ages e g in the ordovician and silurian c 470 460 440 430 420 ma is interpreted as the effect polyphase deformation with deformation enhanced recrystallization of titanite and or different thermal peaks during a long standing geographically fixed high t regime in the mid crust of a continental magmatic arc a clear correlation of the different ages with distinct tectonic events e g collision of terranes is not possible based on the present knowledge of the region

acoustic emission and thermal infrared precursors associated with bump prone coal failure abstract coal bump is sudden catastrophic failure of coal and usually causes serious problems to underground coal mining the acoustic and thermal infrared radiation tir characteristics of bump prone coal under uniaxial compression and cyclic loading conditions are investigated in this study the monitoring system consists of a tir observation system a stress and strain measurement system and an acoustic emission monitoring system precursory information for impending failure of coal samples is collected including tir acoustic emission and strain precursors moreover the response speed and the sensitivity of different monitoring systems during the cracking events in the samples are studied under different loading conditions the microstructure of coal sample is analyzed by x ray computerized tomography ct and scanning electron microscope sem the experiment results show that 0 9 c c is the compressive strength and 0 82 c can be regarded as the stress caution points for the failure of bump prone coal under uniaxial compression and under uniaxial cyclic compression respectively they are much higher than 0 79 c as the stress caution point for the normal coal samples it is also indicated that the temperature at coal surface or in the coal mass should be monitored at the perimeter of the site with anticipated collapses it can be a valuable tool to obtain the precursors for mine disaster control such as coal bumps gas outburst and water inrush

origin of gem corundum in calcite marble the revelstoke occurrence in the canadian cordillera of british columbia abstract the calcite marble hosted gem corundum ruby sapphire occurrence near revelstoke british columbia canada occurs in the monashee complex of the omineca belt of the canadian cordillera corundum occurs in thin folded and stretched layers with green muscovite ba bearing k feldspar anorthite an0 85 1 phlogopite na poor scapolite other silicate layers within the marble are composed of 1 diopside tremolite quartz and 2 garnet alm0 7 0 5grs0 2 0 4 na rich scapolite diopside tremolite na k amphiboles non silicate layers in the marble are either magnetite or graphite bearing predominantly pink locally red or purple opaque to transparent corundum crystals have elevated cr2o3 0 21 wt and variable amounts of tio2 rare blue rims on the corundum crystals contain higher amounts of tio2 0 53 wt and fe2o3 0 07 wt the associated micas have elevated cr v ti and ba contents petrography of the silicate layers show that corundum formed from muscovite at the peak of metamorphism 650 700 c at 8 5 9 kbar because the marble is almost pure calcite dolomite is very rare the corundum was preserved because it did not react with dolomite to spinel calcite during decompression the scapolite bearing assemblages formed during or after decompression of the rock at 650 c and 4 6 kbar gem quality corundum crystals formed especially on borders of the mica feldspar layers in an assemblage with calcite whole rock geochemistry data show that the corundum bearing silicate mica feldspar layers formed by mechanical mixing of carbonate with the host gneiss protolith the bulk composition of the silicate layers was modified by si and fe depletion during prograde metamorphism high element mobility is supported by the homogenization of 18o and 13c values in carbonates and silicates for the marble and silicate layers the silicate layers and the gneiss contain elevated contents of cr and v due to the volcanoclastic component of their protolith

origin of titanite in metarodingite from the zagros thrust zone iraq three types of metamorphic titanite have been noted in a metarodingite pod within the tectonized and serpentinized peridotite portion of the penjwin ophiolite sequence within the iraqi zagros thrust zone iztz northeastern iraq type i metamorphic titanite occurs as subhedral to anhedral fine grained disseminated crystals within chlorite that was formed during chloritization of biotite as a result of low temperature t 330 340 c ocean floor metamorphism or rodingitization of plagiogranite under a reducing environment it is characterized by intermediate al2o3 avg 3 61 wt high feot avg 0 89 wt and intermediate tio2 avg 34 7 wt type ii metamorphic titanite occurs as a thin rim around ilmenite and has high al2o3 avg 4 8 wt intermediate feot avg 0 6 wt and low tio2 avg 33 7 wt it represents a reaction product between grossular and ilmenite which resulted from an oxidizing high pressure high temperature p 1 4 1 6 gpa and t 750 c metamorphic event involving plagiogranite type iii metamorphic titanite occurs as very coarse highly fractured grains up to 0 5 mm with inclusions of ilmenite and surrounded by albitic plagioclase analcime and chlorite this titanite is characterized by low al2o3 avg 1 23 wt low feot avg 0 30 wt and high tio2 avg 36 98 wt it formed during extensive titanitization of ilmenite by a reaction with ca plagioclase during moderate pressure and temperature p 1 6 gpa and t 750 c conditions as a result of albitization of ca plagioclase in plagiogranite

ilmenite breakdown and rutile titanite stability in metagranitoids natural observations and experimental results rutile and titanite commonly form by replacement of ilmenite in metamorphic rocks exhumed orthogneiss from the western alps show that titanite is mostly stable below 1 gpa while rutile seems to dominate within rocks recrystallized under higher pressures we herein investigate phase relationships for four granitic compositions with variable cao content at medium to high pressure conditions 0 7 1 6 gpa 450 650 c with a focus on ilmenite breakdown and ti bearing species formation our piston cylinder experiments show that in the investigated p t range ilmenite reacts during metamorphism above 1 2 1 4 gpa to form rutile below this pressure titanite is the dominant ti bearing species for most granitoid compositions we also show that the position of this reaction curve is strongly influenced by the whole rock ca activity for low ca activities rutile may be stable down to 0 7 gpa and below within ilmenite pseudomorphs while the titanite stability field may extend to pressures 1 3 gpa for ca richer compositions both species may be stable in one single sample depending on the local ca activity gradients the finding of metamorphic rutile within metagranitoids with cao contents 2 wt can be considered under certain conditions as a reliable indicator of high pressure metamorphism this study also highlights the importance of improving our knowledge of the phase relationships between rutile and titanite as a function of p t x to better interpret the textural and tectonic history in natural samples as well as the meaning of age values yielded by rutile and titanite geochronometers

titanite major and trace element compositions as petrogenetic and metallogenic indicators of mo ore deposits examples from four granite plutons in the southern yidun arc sw china major minor and trace element abundances in titanite crystals from four granitic plutons in southern yidun arc sw china have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometry the selected plutons are the cretaceous xiuwacu cxwc pluton with quartz vein type mo mineralization economic mo the tongchanggou tcg pluton with porphyry type mo mineralization economic mo the triassic pulang pl pluton with porphyry type cu mineralization subeconomic mo and the triassic xiuwacu txwc pluton without any mo mineralization mo barren our study reveals that the chemical compositions of titanite crystals from these plutons such as ree sr ga delta eu delta ce fe2o3 al2o3 halogens and mo can be used to track magma compositions oxidation states metal fertility and crystallization history the data from this study also show that titanite crystals from these plutons with different potential of mo mineralization have similar mo contents and exhibit an irregular variation between mo and sr abundances indicating non mo enrichment in the residual melt during the progressive crystallization for some mo mineralized plutons our new observations support the recent hypothesis that high initial mo contents in magma and the enrichment of mo in residual melts formed by fractional crystallization are not the only requirements to form a granite related mo ore deposit efficient extraction of the residual melts possibly facilitated by high concentrations of magmatic f is also critical to the ore formation evidence for high f concentration in felsic magma which facilitates melt and fluid separation and economic mo mineralization during magma evolution may be traced by the presence of f rich titanite crystals in the two mo mineralized granite plutons cxwc and tcg these new findings from this study confirm that titanite is indeed a good petrogenetic and metallogenic indicator however in light of the limited contribution of metal fertility to mo mineralization we suggest that titanite mo concentrations should be used along with other crucial proxies such as titanite f contents and fe2o3 al2o3 ratios to better evaluate the mo mineralized potential of granites

application of backscattered electron microscopy in shale petrology a grey pyritic mudstone from central wales red vein unit of the dicellograptus anceps zone upper ordovician ashgill has been examined in thin section by scanning electron microscopy using backscattered electrons using backscatter it is possible to identify individual mineral constituents of the mudstone by virtue of their atomic number z contrast and differential hardness relief the amount of detail observable is far greater than that possible with optical microscopy valuable information can be obtained relating to particle form orientation texture and internal structure which aids in interpretation of the deformational and diagenetic history of the rock the adoption of electron microscopical methods in the study of thin sections and polished rock chip surfaces promises to revolutionize the field of shale petrology

quartz types authigenic and detrital in the upper cretaceous eagle ford formation south texas usa abstract lithologic heterogeneity of the eagle ford formation in south texas arises from mixing of extrabasinal grains of siliciclastic composition with intrabasinal grain assemblages composed dominantly of marine carbonate with a lesser component of biosiliceous debris detrital quartz in particular is derived from both extrabasinal and intrabasinal sources posing a challenge for the use of bulk compositional data for mudrock classification extrabasinal detrital quartz supplied along a major axis of siliciclastic influx the woodbine depositional system of east texas is reduced to a minor part of the grain assemblage in south texas petrographic evidence and point count results indicate that around 85 percent of total quartz in these rocks equal to about 12 6 volume percent is authigenic thus significant quantities of authigenic silica are not restricted to siliceous mudrocks but can be found in carbonate rich mudrocks as well formerly opaline skeletons of radiolaria the dominant source of silica for authigenic quartz precipitation are only poorly preserved by replacements including calcite dolomite pyrite and quartz dissolved silica released by dissolution of radiolarians and perhaps also by volcanic glass dissolution is re precipitated in a variety of forms including matrix dispersed microquartz cement fillings within primary intragranular pores and grain replacement of both calcareous and siliceous allochems the mass balance of dissolved silica mobilized from radiolarians and other reactive silicates and the precipitation of authigenic quartz is uncertain because the initial volumes of now dissolved detrital material versus the final volume of authigenic material quartz and other authigenic silicates cannot be determined with accuracy

element and sr isotope signatures of titanite as indicator of variable fluid composition in hydrated eclogite abstract the trace element signature sr common pb u th ree and hfse of titanite gives important information about the formation process of metamorphic titanite we investigated titanite from different textural positions of a strongly retrogressed eclogite from the tromso norway high p area it shows characteristic titanite rims around partially absorbed rutile interpreted as grown during retrogression and hydration of the high p assemblage the titanite rims around rutile are polycrystalline and in contact with the plagioclase amphibole matrix large idioblastic single crystal titanite grew in veins without relics of precursor rutile compositional zoning of al ti f in titanite of both textural positions is irregular and not related to core or rim position in the crystals there is no evidence for systematic growth sequences or diffusion reflecting changing p t conditions or systematic changes of fluid composition trace element patterns of titanite la icp ms data however show systematic variations in the coupling and decoupling behaviour of strongly fluid mobile sr u moderately fluid mobile ree and little fluid mobile nb ta zr hf elements the trace element signatures of titanite from the two different fabric positions reflect contrasting characteristic fluid compositions single crystal titanite equilibrated with fluid that was channelled in the vein polycrystalline titanite on rutile records the composition of a fluid that had migrated along grain boundaries in the amphibole plagioclase matrix fluid from the matrix also contributed to the geochemical signature of vein titanite whereas influence of fluid from the vein on the composition of polycrystalline titanite in the matrix is not evident 87sr 86sr isotope ratios of the different titanite types support the inference from trace elements of spatially and temporally variable fluid sources

ti al zoning of experimentally grown titanite in the system cao al2o3 tio2 sio2 nacl h2o f evidence for small scale fluid heterogeneity chemical zoning according to the substitution al oh f ti o is a common phenomenon in natural titanite and can be used to reconstruct its growth conditions we synthesized titanite which has a zoning pattern similar to that found in natural titanite that grew at the expense of rutile visible in element distribution maps as a patchy irregular pattern run conditions in the system cao al 2 o 3 tio 2 sio 2 nacl h 2 o caf 2 were 600 c 0 4 gpa 1 to 107 days duration natural rutile crystals were placed in a perforated pt tube within an outer au capsule containing wollastonite al 2 o 3 optionally powdered caf 2 and a nacl brine to simulate conditions where rutile is transformed into titanite by a hydrous ca si al f fluid driven by a chemical potential gradient between inner and outer capsule spontaneous nucleation of titanite is restricted to a small number of crystals on the rutile surface in the inner capsule growth proceeds from sparse isolated titanite crystals after 1 day to assemblages of several 100 m large crystals in a reaction rim in the long time runs titanite is strongly zoned in al ti and shows up to 0 5 al per formula unit pfu in experiments containing f without f substitution is limited to 0 25 al pfu the range of the ti al exchange is already large in short run times and the same heterogeneity is observed in long time runs the al ti distribution with and without f in compositional domains up to several tens of micrometers is patchy and irregular no relation of the zoning with time core rim or preferred growth directions was observed in the case of fluid mediated growth mineral growth zoning represents a disequilibrium at supersaturated conditions the concentration of ti in the fluid is likely the limiting factor for titanite growth considering the low solubility compared to that of al ca and si titanium is not transported in significant amounts into the outer capsule indicating low mobility in contrast to al ca and si which are transported into the inner capsule assuming buffered al concentration from dissolution of the al source we speculate that the ti al of the fluid at the precipitation site was controlled by the local ti concentration which varies over the distance from the rutile surface to the growing titanite crystal and produces the irregular patchy zoning

dynamic disaster control under a massive igneous sill by grouting from surface boreholes abstract an overlying 140 m thick massive igneous sill has adversely affected mining activities considerably in the haizi coal mine china a coal and gas outburst disaster occurred during the drivage for a subsequent longwall after the extraction of two faces in the ii102 mining area the massive sill was determined to be primarily responsible for this outburst owing to the bed separation that occurred below the sill due to the sill s large span this is because such separation meant the massive sill was not supported by the gob as in a general case but it was supported by the solid coal instead resulting in a long load transfer distance that caused the drivage gate to collapse unexpectedly into the abutment thus it was determined that the high abutment pressure primarily triggered the outburst such disaster risk would have remained had the drivage in the gate continued and a wide area and sudden roof fall could have occurred during the extraction of the next longwall had the igneous sill broken suddenly as the critical span was reached with these risks in mind a field trial of a method of grouting into the overburden of the abandoned faces from surface boreholes was conducted for dynamic disaster control this technique alleviates the abutment pressures and restrains the igneous sill deflection by eliminating fractures and voids in the overburden using grouting the adoption of this grouting method led to the subsequent drivage and mining of a further 510 m without occurrence of any further dynamic disasters

perspectives oxygen isotopes and the origin of quartz published data indicate that in igneous rocks the delta 18 o of quartz averages about 9 per thousand in metamorphic rocks 13 to 14 per thousand in sandstones 11 per thousand in shales 19 per thousand quartz overgrowths in sandstones 20 per thousand and cherts 28 per thousand either a very large proportion of the silt and clay size quartz in shales about 90 of the total quartz in shales is secondary or the isotopic data are incomplete it is concluded that the latter interpretation is correct because published isotopic analyses of metamorphic rocks consider only the coarser grained rocks phyllites and slates whose quartz is nearly all of silt and clay size and has more positive delta 18 o values than quartz from schists and gneisses probably supplies the bulk of quartz to mudrocks

updating the use of the ccbo cell in japan overcoring case studies abstract the compact conical ended borehole overcoring ccbo device for stress measurement was the subject of an isrm suggested method published in 1999 int j rock mech min sci 36 3 1999 307 in this paper recent case studies using the ccbo device are described the six case examples involve both natural and perturbed stress states near a fault within a mountain around a tunnel and cavern over a wide region and in a high stress field the use of the measurement results and the characteristics of the states of stress were clarified successfully from these measurements