non parametric seismic hazard in mines seismic hazard analysis methods in mines are reviewed for the purpose of selecting the best technique to achieve this goal the most often used hazard analysis procedure which is based on the classical frequency magnitude gutenberg richter relation as well as alternative procedures are investigated since the maximum regional seismic event magnitude m max is of paramount importance in seismic hazard analysis this work provides a generic formula for the evaluation of this important parameter the formula is capable of generating solutions in different forms depending on the assumptions of the model of the magnitude distribution and or the available information regarding past seismicity it includes the cases i in which seismic event magnitudes are distributed according to the truncated frequency magnitude gutenberg richter relation and ii in which no specific model of the magnitude distribution is assumed both synthetic monte carlo simulated seismic event catalogues and actual data from the copper mine in poland and gold mine in south africa are used to demonstrate the discussed hazard analysis techniques our studies show that the non parametric technique which is independent of the assumed model of the distribution of magnitude provides an appropriate tool for seismic hazard assessment in mines where the magnitude distribution can be very complex

late proterozoic granitoid magmatism in the state of sao paulo southeastern brazil abstract the precambrian basement in the state of sao paulo is made up of a series of metamorphic units exposed at various erosional levels and in part separated by large faults a strong overprint of the brasiliano cycle 700 500 ma is evident from isotopic data over most of the region nevertheless a large part of the metamorphic belts belong to older archaean to middle proterozoic reworked sequences about 30 of the total basement area consists of intrusive granitoids of late proterozoic age these can be grouped into six major groups on the basis of petrography geochemistry rock association associated manifestations and whenever possible age relationships gneissic mangerite charnockite hastingsite granite associations appear as folded tabular bodies within high grade regions the sao jose do rio pardo suite is chemically comparable to the aluminous a type granitoid series and its emplacement possibly signals a period of extensional tectonics prior to the onset of the brasiliano cycle 1000 ma a series of elongated batholiths 650 ma with predominant porphyritic hornblende biotite granitoids is present mainly in high grade areas the compositions are generally granitic to granodioritic but intermediate e g monzodioritic rocks are locally common these high k calc alkaline suites are in some aspects comparable to the cordilleran i type granitoids and their origin might be related to a subductional environment migmatitic granitoids constitute a peculiar association occurring as a series of small bodies within high grade allochthonous domains these polyphase heterogeneous often nebulitic granitoids are source related products of crustal anatexis syn to late orogenic brasiliano granitoids in the low to medium grade domains are dominantly porphyritic calc alkaline biotite granites and granodiorites reminiscent of caledonian i types in contrast a peraluminous association porphyritic biotite granitoid to equigranular two mica granite predominates in high grade domains which possibly reflects a different tectonic evolution for the two regions late to post orogenic brasiliano granitoids intruded after the major orogenic development of the region 610 590 ma i type calc alkaline and aluminous a type granitoids are geographically associated in the itu belt and appear to show some temporal and geochemical overlapping wiborgitic facies and some sn w mineralization are locally present in the a type suites a post orogenic extensional period is marked in the south of the area by the emplacement of shallow a type granitoids in the serra do mar belt

key strata characteristics controlling the integrity of deep wells in longwall mining areas abstract the damage of vertical oil gas wells in longwall mining areas is mainly a result of strata movement induced by coal extraction strata with contrasting lithology vary dramatically in their movement and potential for well damage with some special combinations of strata in particular having the greatest potential for damage this study investigates the effects of specific combinations of strata transition structures i topsoil bedrock ii a thin weak interlayer sandwiched above and below by two stiff beds and iii the key stratum sandwiched above and below by two soft beds on the magnitude severity and distribution of various anticipated well deformations and explores the optimal drilling path for wells to maximize well integrity results indicate that 1 effects of various combinations of strata on well deformation lie essentially in the mismatch in the mechanical properties of the strata and weak interfaces with the stratum thickness and vertical distance from the coal seam to the stratum interface also exerting a significant influence 2 wells in the upper part of the topsoil are subject to horizontal tension while the lower part is laterally compressed following the extraction of either one panel or both panels large lateral tensile strains normally arise at the upper part of the hard strata which directly underlie the soft strata large lateral compressive strains are concentrated in the strata within 5 m above and below the coal seam and peak in the seam longitudinal well deformation is dominated by compression in soft strata especially in the upper part of the layer and is dominated by tension in stiff strata within the lower portion in particular vertical compression at the interface is larger below the key stratum and peaks at the interface between the coal seam and its immediate roof well distortions in soft strata are 3 to 5 times those of ones in stiff strata 3 well deformations developing both at interfaces and within layers significantly intensify in the vicinity of the seam an integrated consideration of various deformations of five candidate well paths indicates that the optimal position for well stability is the one that deviates from the pillar centerline and is close to the second mined panel

test ban treaty verification with regional data a review this paper summarizes the use of regional 30 seismic data in a test ban context for detecting locating identifying and determining the yield of underground nuclear explosions in many areas of the world eastern north america africa eastern ussr lg is the largest amplitude wave recorded on standard seismograph systems and thus is the most appropriate phase for monitoring small magnitude events excellent location capability for near regional events has been demonstrated at the norwegian small aperture array noress using lg and p waves lg and other regional phases may contain information on source depth but such information has not been exploited to date fifteen classes of regional discriminants have been identified including 1 1 first motion 2 2 ms mb 3 3 p2 p1 ratio 4 4 excitation of short period sh waves 5 5 lg rg amplitude ratios 6 6 pn lg pg lg and pmax lg amplitude ratios 7 7 lg group velocity and energy ratios in lg 8 8 excitation of sn 9 9 third moment of frequency 10 10 generation of higher mode surface waves 11 11 peak amplitudes of love and rayleigh waves and long period surface wave energy density 12 12 prevailing period of long period love waves 13 13 spectral ratio long period s waves to rayleigh waves 14 14 spectral ratio long period love waves to rayleigh waves 15 15 frequency of the peak spectral amplitudes and spectral ratios in pn pg s and lg each of these proposed discriminants has with differing degrees of success separated some explosions from some earthquakes however most have been tested only on limited data usually from one geographic region and only one or two recording stations no systematic analyses have been done to determine the best individual discriminant or combination of them preliminary evaluation of the use of lg for yield determination suggests that regional waves hold promise in this application theoretical studies have contributed significantly to the understanding of propagation characteristics of regional waves but further studies are required emphasizing modeling for realistic anisotropic sources the major conclusion of this study is that a systematic and comparative evaluation of all the proposed regional discriminants is now required utilizing a common data base derived from all present day test sites this evaluation would suggest the optimal discrimination procedure using regional waves and would also define areas of needed research without such an integrated evaluation it is still possible to speculate using existing results on the most promising regional discriminants

extraction algorithm of mining subsidence information on water area based on support vector machine information on subsidence in a water area caused by mining has a great value on the research of the mining subsidence law of a mining area with a high groundwater level in eastern china based on the measured data of the subsidence area without water the data extraction of subsidence in a water area is studied in this paper with a support vector machine as subsidence in such an area is difficult to measure research shows that the training sample number and dimension should be strengthened by increasing the measuring times or using the interpolation method to obtain ideal prediction accuracy the e support vector regression model with three parameters optimized by the genetic algorithm or the particle swarm optimization algorithm is suitable to extract subsidence information in a water area caused by mining and the algorithm is accomplished on matlab data analysis showed that when the water is deeper than 1 8 m and the distance is over 60 m from the measured points the prediction error of test samples will exceed 10 out of all measured results meaning that practicability is relatively poor while water depth is 0 8 m or the distance is lower than 60 m from the measured points the prediction error of test samples will be calculated to 5 of the measured results the prediction results can be used

chromium isotopes in carbonates a tracer for climate change and for reconstructing the redox state of ancient seawater abstract strontium and carbon isotopes of marine carbonates are routinely applied for chemostratigraphic cross correlations of time equivalent sedimentary sequences and for calibration of the compositional evolution of seawater throughout earth s history mainly for the purpose of reconstructing ancient climatic changes we here present results of a new isotopic tracer system stable chromium isotopes applied to a late ediacaran marine carbonate sequence exposed in the calera de recalde syncline arroyo del soldado group uruguay the aim was to compare cr isotope signatures directly to 13 c 87 sr 86 sr and 143 nd 144 nd fluctuations in a well defined stratigraphic profile comprising sediments that were deposited during cold warm periods accompanied by sea level changes in response to glaciation deglaciation at higher latitudes the studied section is characterized by a pronounced negative down to 3 3 13 c excursion in carbonates paralleled by a decrease of 87 sr 86 sr values chromium isotope signatures over this section also show a correlated decrease in 53 cr 53 cr 53 cr 52 cr sample 53 cr 52 cr srm979 1 1000 values from 0 29 to 0 17 which mirrors a decrease in positively fractioned seawater signatures to slightly negative values characteristic of high temperature magmatic sources linear correlations between 53 cr and end 570 ma 87 sr 86 sr and cr concentrations can be explained by mixing between two major input sources of cr nd and sr into the shallow seawater 1 a source characterized by negative 53 cr values of 0 2 low 87 sr 86 sr values of 0 707 and elevated 147 sm 144 nd values of 0 13 recognized as a subaqueous hydrothermal dominated input source and 2 a source characterized by positively fractionated 53 cr values of 0 2 higher 87 sr 86 sr values of 0 708 and lower 147 sm 144 nd values of 0 11 a source which is strongly affected by continentally derived input chromium isotopes provide a powerful tool for reconstructing the redox state of ancient seawater since positive values indicate that at least locally neoproterozoic shallow ocean waters were sufficiently oxidized to fractionate chromium and or that oxygen levels of the atmosphere were sufficient to transform cr iii into the more mobile hexavalent cr vi formed during weathering processes on land the fact that 87 sr 86 sr values despite 13 c fluctuations remain low indicative of a strong hydrothermal input into the basin at his time implies that co 2 limitation was the cause of negative 13 c and 53 cr excursions in otherwise nutrient rich late neoproterozoic basins and that glaciation is only one more consequence of a tectonically driven biologically mediated system in such a scenario glaciation acts as an amplifier of 53 cr signals these signals in marine carbonates are a sensitive tracer for redox processes in the ocean and or on land and have the potential to contribute significantly in combination with the other commonly used isotopic tracers to the reconstruction of climatic changes particularly those that are associated with major glaciation periods in earth s history

residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

elemental and sr nd isotope geochemistry of two neoproterozoic mangerite suites in se brazil implications for the origin of the mangerite charnockite granite series abstract neoproterozoic 625 ma mangerites are the dominant rock type in a 100 km long belt of deformed tabular bodies in the socorro guaxupe nappe sgn a high grade terrane southwest of the sao francisco craton southeastern brazil the mangerites form two suites sao pedro de caldas shows a wide compositional variation and abundant felsic rocks mangerite hornblende granite leucogranite initial 87 sr 86 sr of 0 707 and initial e nd of 4 to 5 divinol ndia is dominated by more mafic mangerites with minor charnockite granite and diorite and has initial 87 sr 86 sr of 0 710 and initial e nd of 10 to 12 the probable sources of the sao pedro de caldas mangerites were granulites depleted by previous melting events in radiogenic elements and the light rare earth element primary melts of sao pedro de caldas were generated at 950 c p 10 kbar from a biotite free and k feldspar bearing source with plagioclase as an important residual phase the amount of melting was low as required by low mg enrichment in nb and ta relative to potential sources and high nb ta and was probably controlled by exhaustion of k feldspar in the source contribution from infracrustal mafic melts cannot be ruled out and would help explain the weakly negative e nd and high nb but is not essential the divinol ndia rocks depart from typical within plate mangerites towards more mafic rocks with orogenic signatures e g higher mg sr ca lower zr radiogenic isotope data require sources with greater crustal residence time than those envisioned for sao pedro de caldas elemental data require that these sources were more depleted e g higher k rb granulites with these characteristics are exposed in the northern portion of the sgn these were probably melted at slightly higher temperatures than the sao pedro de caldas suite 970 c before a sufficient amount of melt was generated and the magmas could leave their sources in this case k feldspar was exhausted and plagioclase in amounts exceeding those of the granite minimum was dissolved

permeability variations within mining induced fractured rock mass and its influence on groundwater inrush this paper is concerned with the evaluation of permeability of fractured rock mass due to the cover stress re establishment which is a major factor in controlling water and gas flow rate induced by mining operations in fractured rock the case study considered in this paper is based on the results of observations of groundwater inrush and a decrease in water inflow from the fractured roof strata due to mining advancing in the taiping coalmine shandong province china a conceptual model of an effective porous media was used to assess the permeability distribution in the fractured zone induced by coal mining the cover stress re establishment in gob fractured rock mass was evaluated using an empirical formula based on the surface subsidence a simplified conceptual model of the fractured zone was used to evaluate the deformation of fractured zone along with the evaluation of changes in the rock permeability above the gob due to the cover stress re establishment these data were then used to calculate the water inflow rate into the panel predicted water inflow rates have been found to be in good agreement with those from monitoring data this study improved the understanding of the mechanisms of the post mining cover stress re establishment on permeability change of the overburden fracture rock strata these results can then be applied for numerical simulations of the process of overburden failure and consequent groundwater inrush due to coal mining

crystallization conditions and controls on trace element residence in the main minerals from the pedra branca syenite brazil an electron microprobe and la icpms study abstract major and trace element microanalyses of the main minerals from the 610 ma pedra branca syenite southeast brazil allow inferences on intensive parameters of magmatic crystallization and on the partition of trace elements among these minerals with important implications for the petrogenetic evolution of the pluton two main syenite types make up the pluton a quartz free syenite with tabular alkali feldspar laminated silica saturated syenite lss with na rich augite phlogopite hematite magnetite titanite apatite and a quartz bearing syenite laminated silica oversaturated syenite lso with scarce corroded plagioclase plus diopside biotite hornblende ilmenite magnetite titanite apatite both types share a remarkable enrichment in incompatible elements as k ba sr p and lree apatite saturation temperatures of 1060 1090 c are the best estimates of liquidus whereas the pressure of emplacement based on al in hornblende barometry is estimated as 3 3 to 4 8 kbar although both units crystallized under oxidizing conditions oxygen fugacity was probably higher in lss as shown by higher mg of the mafic minerals and higher hematite contents in hem ilmss in contrast with the ca bearing alkali feldspar from lso which hosts most of the whole rock sr and pb virtually ca free alkali feldspar from lss hosts 50 of whole rock sr and 80 of pb the remainder of these elements being shared by apatite pyroxene and titanite this contrast reflects a strong crystal chemical control whereby a higher proportion of an element with similar ratio and charge ca2 enhances the residence of sr and pb in the m site of alkali feldspar the more alkaline character of the lss magma is inferred to have inhibited zircon saturation zr hf remained in solution until late in the crystallization and were mostly accommodated in the structure of ca na pyroxene and titanite which are one order of magnitude richer in these elements compared to the same minerals in lso where most of zr and hf are inferred to reside in zircon the ree th and u reside mostly in titanite and apatite d ree tit ap raises steadily from 1 to 6 from la to tb then remains constant up to lu in the lso sample these values are about half as much in the lss sample where lower contents of incompatible elements in titanite are attributed to its greater modal abundance and earlier crystallization

microbial origin of early animal trace fossils abstract elongate surface trails that abound in late ediacaran and early paleozoic sandstone and siltstone are often attributed to early animals these trails commonly exist on the same beds as wrinkle structures millimeter to centimeter size ridges and pits that are interpreted as evidence of the former presence of microbial mats here we show that interactions between oscillatory flow and centimetric microbial aggregates produce elongate trails on the surface of a sediment bed trails left by moving microbial aggregates share a number of characteristics with some presumed trace fossils of the earliest animals elevated edges zig zag patterns smooth curves reversals intersections with other trails series of pits and paths that terminate abruptly and restart nearby under the same flow conditions millimetric microbial aggregates generate wrinkle structures thus the interaction between flow and microbial aggregates on a sediment bed can produce a number of structures that are commonly interpreted as evidence of early animal locomotion

the origin of anorthosites and related rocks from the lofoten islands northern norway i field relations and estimation of intrinsic variables these calculations indicate that the calcic flakstadoy anorthosite introduction and geological fbc cpx ol opx mtss ilmss plag an57 47 setting crystallized under polybaric conditions at pressures between 4 and 9 kbar and at temperatures between 1140 and 1185 c the sodic the commonly observed association of proterozoic maseidsfjord complex cpx opx mtss ilmss plag sif type anorthosites see ashwal 1993 and references an48 44 crystallized at 1100 1135 c at a maximum pressure therein with jotunitic and mangeritic or charnockitic of 7 3 kbar this technique may provide a means to estimate rocks is still not satisfactorily explained some models crystallization pressure and asio2 in many types of intrusive and consider them to be comagmatic and relate these rocks extrusive rocks coeval mangerites and charnockites intruded subby processes of liquid immiscibility philpotts 1981 or a sequently at 4 kbar and temperatures between greater than 925 c specific fractionation trend owens et al 1993 others and 800 c respectively indicated by the succession of the mafic describe them as coeval but not comagmatic duchesne phase assemblages cpx opx cpx opx ol cpx et al 1989 duchesne 1990 a typical proterozoic pig ol cpx ol that reflect continuous fractionation to anorthosite mangerite charnockite association is exhigher fe mg ratios the evidence for polybaric crystallization of posed in the lofoten islands off the nw coast of norway the fbc quantitatively supports the common model that generation which is dominated by mangerites and charnockites in of proterozoic anorthosites involves initial crystallization at depth this paper the first of a series on these rocks we present crust mantle boundary and intrusion as a crystal rich mush the field observations and phase petrology and determine the conditions under which the intrusions were emplaced detailed estimation of intrinsic parameters p t fo2 asio2 fhcl

the new three dimensional subsidence influence function denoted by n k g abstract this study presents a three dimensional development of the n k g influence function with the aim of predicting subsidence phenomena and characterizing the shape and dimensions of the corresponding trough the parameters n and k characterize the ground and g is related to the gravity this function depends on two physical concepts the first is gravity which characterizes the forces acting on the ground and the second the convergence of the roof and floor of the mine workings due to the stress state of the ground caving in of the roof generates direct subsidence and the swelling of the floor indirect subsidence which allow us to establish the shape of the trough the physical concepts introduced are fundamental in the mathematical implementation of the n k g influence function allowing a more intuitive interpretation of the subsidence trough and notably facilitating the work of calibration validation and sensitivity analysis these concepts likewise allow the scope of application of influence functions to be extended to non horizontal seams also taking into account the quality of the rock mass and the presence of preferential sliding directions in both the roof and the floor of the seam in the development of this paper we shall first see the physical concepts considered to then present the three dimensional implementation of our n k g influence function we shall see the results obtained when calibrating the proposed numerical model with real data obtained from subsidence measurements in a coalmine in the coal basin of asturias situated in the north of spain

characterization and origin of aluminous a type granites from the lachlan fold belt southeastern australia the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are a distinctive group of igneous rocks on the basis of chemical and mineralogical criteria those granites that contain 65 72 sio2 can be distinguished from other types on the basis of higher abundances of fetotal fetotal mg high field strength elements trivalent rare earth elements ga and zn mineralogically they contain fe rich hydrous mafic minerals and primary ilmenite and hence are reduced relative to the ni nio buffer however the extremely felsic a type granites sio2 72 have the same chemical and mineralogical characteristics as felsic fractionated i type granites recent analyses indicate that the lachlan fold belt a type granites have sc f alkali element trace transition element and h2o contents similar to those of other unfractionated i type granites rb sr and nd sm isotopic compositions are highly variable probably reflecting source region heterogeneity the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are distinct from peralkaline rocks in terms of chemical composition petrography and field associations although these rocks have been grouped together as a single type in current classification schemes we propose that the metaluminous to weakly peraluminous a type granites such as those of the lachlan fold belt should be defined as aluminous a type granites and should not be grouped with peralkaline granites the lachlan fold belt aluminous a type granites have relatively high calculated zircon saturation temperatures we suggest that these granites were produced by high temperature partial melting of a felsic infracrustal source

probabilistic modeling using bivariate normal distributions for identification of flow and displacement intervals in longwall overburden abstract gob gas ventholes ggv are used to control methane emissions in longwall mines by capturing it within the overlying fractured strata before it enters the work environment in order for ggvs to effectively capture more methane and less mine air the length of the slotted sections and their proximity to top of the coal bed should be designed based on the potential gas sources and their locations as well as the displacements in the overburden that will create potential flow paths for the gas in this paper an approach to determine the conditional probabilities of depth displacement depth flow percentage depth formation and depth gas content of the formations was developed using bivariate normal distributions the flow percentage displacement and formation data as a function of distance from coal bed used in this study were obtained from a series of borehole experiments contracted by the former us bureau of mines as part of a research project each of these parameters was tested for normality and was modeled using bivariate normal distributions to determine all tail probabilities in addition the probability of coal bed gas content as a function of depth was determined using the same techniques the tail probabilities at various depths were used to calculate conditional probabilities for each of the parameters the conditional probabilities predicted for various values of the critical parameters can be used with the measurements of flow and methane percentage at gob gas ventholes to optimize their performance

an extension of the insar based probability integral method and its application for predicting 3 d mining induced displacements under different extraction conditions underground extraction can be roughly classified into three types i e subcritical critical and supercritical extraction in accordance with the geological conditions in the overburden and the geometry of mined out areas in 2016 we proposed an approach based on the interferometric synthetic aperture radar insar technique and the probability integral method pim for the cost effective prediction of 3 d mining induced displacements abbreviated as insar pim due to the inherent assumption of critical extraction in the pim the insar pim method performs well in predicting the 3 d displacements caused by critical and or supercritical extraction but poorly for subcritical extraction in this paper we first propose a generalized pim gpim by modifying the traditional pim with a simplified boltzmann function we then replace the pim of the insar pim with the proposed gpim to develop an extension of insar pim referred as to insar gpim the insar gpim was tested in the qianyingzi coal mining area china the results show that the insar gpim predicted horizontal and vertical displacements caused by subcritical critical and supercritical extraction agree well with the in situ observations with average root mean square errors of about 0 032 and 0 050 m respectively these accuracies represent improvements of 60 9 and 59 when compared with the accuracies predicted by the insar pim in the horizontal and vertical directions the results indicate that the insar gpim is capable of accurately predicting 3 d mining induced displacements under different extraction conditions i e subcritical critical and supercritical extraction and it performs much better than the insar pim in the case of subcritical extraction it is therefore believed that insar gpim will have a wider scope of applications than the previous insar pim

analysis of gob gas venthole production performances for strata gas control in longwall mining longwall mining of coal seams affects a large area of overburden by deforming it and creating stress relief fractures as well as bedding plane separations as the mining face progresses stress relief fractures and bedding plane separations are recognized as major pathways for gas migration from gas bearing strata into sealed and active areas of the mines in order for strata gas not to enter and inundate the ventilation system of a mine gob gas ventholes ggvs can be used as a methane control measure the aim of this paper is to analyze production performances of ggvs drilled over a longwall panel these boreholes were drilled to control methane emissions from the pratt group of coals due to stress relief fracturing and bedding plane separations into a longwall mine operating in the mary lee blue creek coal seam of the upper pottsville formation in the black warrior basin alabama during the course of the study pratt coal s reservoir properties were integrated with production data of the ggvs these data were analyzed by using material balance techniques to estimate radius of influence of ggvs gas in place and coal pressures as well as their variations during mining the results show that the ggvs drilled to extract gas from the stress relief zone of the pratt coal interval is highly effective in removing gas from the upper pottsville formation the radii of influence of the ggvs were in the order of 330 380 m exceeding the widths of the panels due to bedding plane separations and stress relieved by fracturing material balance analyses indicated that the initial pressure of the pratt coals which was around 648 kpa when longwall mining started decreased to approximately 150 kpa as the result of strata fracturing and production of released gas approximately 70 of the initial gas in place within the area of influence of the ggvs was captured during a period of one year

the transpressional connection between dom feliciano and kaoko belts at 580 550 ma a new u pb shrimp age of 551 4 ma on a mylonitic porphyry that intruded into the sierra ballena shear zone southernmost dom feliciano belt uruguay and a review of relevant published data make possible a more refined correlation and reconstruction of brasiliano pan african transpressional events paleogeographic reconstruction kinematics and timing of events indicate a connection between the shear systems of the dom feliciano and kaoko belts at 580 550 ma sinistral transpression recorded in shear zones accommodates deformation subsequent to collision between the congo and rio de la plata cratons the correlation is strengthened by the similarity of magmatic and metamorphic ages in the coastal terrane of the kaoko belt and the punta del este terrane of the dom feliciano belt this post collisional sinistral transpression brought these units near to their final position in gondwana and explains the different evolution at 550 530 ma while in the kaoko belt an extensional episode resulted in exhumation as a consequence of collision in the damara belt in the dom feliciano belt sinistral transpression occurred associated with the closure of the southern adamastor ocean due to kalahari rio de la plata collision

terrane accretion and upward extrusion of high pressure granulites in the neoproterozoic nappes of southeast brazil petrologic and structural constraints the high grade crystalline nappes exposed southeast of the sao francisco craton comprise two distinct units of mainly granulite facies rocks that represent a composite section of neoproterozoic deep continental crust the socorro guaxupe nappe above derived from an arc terrane and the tres pontas varginha nappe below metamorphism in the tres pontas varginha nappe is characterized by the exceptional preservation of kyanite granulites 700 750 c 15 kbar and followed by limited retrogression maximum temperatures around 900 950 c were reached toward the base of the overlying socorro guaxupe nappe during the intrusion of charnockitic mangeritic magmas lower pressure metamorphism accompanied by anatexis prevailed at shallower crustal levels our petrological results document an inverted thermal structure with isobaric heating of the top of the high pressure granulite nappe both granulite nappes were transported more than 200 km eastward above lower nappes involving reworked basement and passive margin units both metamorphosed to high pressure but lower temperature conditions significant thinning and cooling of the two granulite nappes may have occurred before their emplacement onto the lower nappes the proposed geodynamic scenario considers that continental subduction took place westward underneath neoproterozoic oceanic lithosphere the two granulite units crystallised at 45 km depths under distinct paleogeotherms within this subduction zone around 630 ma the kyanite granulites were rapidely exhumed through the mechanism of low angle forced extrusion whereas syncollisional collapse affected the soft anatectic middle crust of the overlying arc terrane the final emplacement of the thinned nappe pile onto the cold sao francisco craton and its platform cover with at most anchizonal to greenschist facies metamorphism occurred around 600 ma

mapping ground movements caused by mining induced earthquakes applying satellite radar interferometry abstract anthropogenic activity related to the extraction of gas and oil raw materials or water pumping leads to slow or rapid ground deformation the ground motion rate is related to the type of the mined material geological conditions mining methods and other factors ground subsidence resulting from the collapse of underground post mining voids occurs gradually mining induced earthquakes and seismic earthquakes are largely unpredictable and have an adverse impact on the local inhabitants and buildings for this reason monitoring of this phenomenon is a challenge the application of interferometric sar for the evaluation of ground movement has brought satisfactory results over the past twenty years mainly in the regions where no other measurements were conducted during ground subsidence in this paper we have examined a mining induced earthquake with a magnitude 4 5 which occurred in an underground copper ore mine in poland on 29th november 2016 and caused eight fatalities it also had an impact on ground surface deformation in the vicinity of the mine tailings an assessment of the earthquake related impact on surface movement was carried out by sentinel 1 tops time series interferometry the velocity of ground movement and the scale of the phenomenon were investigated in addition the impact of the mining induced earthquake on zelazny most mine tailings site was analyzed moreover the process of dynamic ground compaction was also investigated in detail ground movement following the mine earthquake was explored two time phases of the movements were determined the first phase of dynamic ground displacement was rapid and 90 of total ground deformation appeared on the surface within 7 days the second phase of displacement was a vanishing one it lasted for approx 3 weeks and 10 of ground deformation appeared on the surface the study revealed that the maximum observed ground subsidence did not exceed 9 cm the presented results contribute to a better understanding of post earthquake ground deformations in the light of their spatial distribution in time

yardea dacite large volume high temperature felsic volcanism from the middle proterozoic of south australia the yardea dacite is a large volume felsic volcanic unit from the middle proterozoic gawler range volcanics of south australia it has been previously described as an ignimbrite however some samples contain no petrographic evidence for a pyroclastic origin but have characteristics compatible with final crystallization from a nonfragmented magma these samples may have erupted as lavas but others are likely to be extremely densely welded ignimbrites suggesting a compound nature for the unit geothermometry and phase equilibria indicate that the yardea dacite originated from a high temperature 1000 c felsic magma with a low water content 2 the yardea dacite is not associated with a known caldera of the valles type and shares many characteristics of recently described cenozoic felsic volcanic rocks from the western united states interpreted as rheoignimbrites or as unusually extensive lavas

earthquake signals in tree ring data from the new madrid seismic zone and implications for paleoseismicity severe ground shaking and the formation of reelfoot lake during the great new madrid earthquakes of a d 1811 1812 had a profound effect on baldcypress trees that still survive in reelfoot lake of northwestern tennessee inundation greatly increased baldcypress radial growth from 1812 to 1819 and permanently decreased wood density after 1811 ground shaking fractured the baldcypress stems that were present during the 1811 1812 event but fractures are absent in the post 1811 growth in contrast the growth of old baldcypress trees in the st francis sunkland of northeastern arkansas was severely suppressed for almost 50 yr following the 1811 1812 new madrid earthquakes thus there are two opposite but profound growth responses to the same earthquake events preserved in baldcypress trees of the new madrid seismic zone the tree ring chronology at reelfoot lake extends from a d 1682 to 1990 but the 1812 1819 growth surge was the only extreme growth anomaly in this 309 yr period the st francis sunkland chronology extends from a d 1321 to 1990 and the 1812 1857 growth suppression is the most severe and prolonged growth anomaly of this entire 670 year period thus the tree ring record indicates that there was not a great earthquake during the 129 yr prior to 1811 in the reelfoot lake basin nor during the 490 yr prior to 1811 in the st francis sunkland

the stability of methane capture boreholes around a long wall coal panel this paper describes the application of computational modelling to the prediction of the stability of methane drainage boreholes during the extraction life of an active long wall coal panel within a united kingdom coal mine the modelling was undertaken to investigate the affects that changes in the roof geology and roadway support system may have on the deformation and closure of the gas drainage boreholes drilled from the tailgate across the goaf of an active long wall panel the paper also outlines the development of an analytical model to estimate the bending deformation axial strain and the rupture of borehole casing due to rock shear this model was used in conjunction with the geomechanical strata models to predict the distance behind the face line at which excessive borehole deformation and closure would occur this method was used to evaluate the optimum roadway support system and spacing between boreholes to maintain effective borehole drainage subject to the range of geological conditions encountered during the panel retreat a good correlation was obtained between the model predictions and the geomechanical and gas drainage data measured at a uk colliery

three dimensional effects of hydraulic conductivity enhancement and desaturation around mined panels changes in the three dimensional hydraulic conductivity field that accompany undermining by a longwall panel are evaluated to define the potential for changes in flow patterns and desaturation relations linking changes in conductivity with the mining induced strain field that develops around the advancing face are defined through the assumption of an equivalent porous medium with the strain partition between fractures and matrix apportioned relative to respective deformation constants model results are validated against behavior recorded at a well instrumented field site replicating the complex steady flow pattern that develops around an advancing longwall face significant hydraulic conductivity increases are restricted to strata at shallow depth ahead of the advancing face and to deep zones behind the face particularly in the caving zone and abutment shear zones these very large increases in conductivity at depth that include the out of section conductivity enhancement that develops along the panel rib exercise primary control on induced water level changes and the potential for saturation zones of desaturation are readily defined with these enabling locations of well vulnerability to water loss to be identified these zones of vulnerability are directly above the panel with their extent potentially modulated by the presence and the location of flatlying layers of low conductivity the complex response recorded in the near face region mandates use of three dimensional models to adequately represent observed behavior

mangerite magmatism associated with a probable late permian to triassic hongseong odesan collision belt in south korea abstract the odesan area in the eastern gyeonggi massif south korea consists principally of migmatitic and porphyroblastic gneisses intruded by mangerite mafic mangerites with sio 2 contents from 52 40 to 54 20 wt have higher feo mgo 14 98 18 28 wt and cao contents 5 80 7 84 wt but lower total alkali contents 4 74 2 o k 2 o 2 2 o k 2 o

a formalism to compute permeability changes in anisotropic fractured rocks due to arbitrary deformations abstract the liu elsworth 1997 formalism that predicts permeability in deformed fractured rock has been highly useful and successful in numerous engineering situations involving mining coal bed methane and shale gas extraction the formalism assumes the rock s fractures are aligned with three orthogonal axes and that the rock is subjected to strains along these three directions only here we relax these assumptions our proposed formula yields the permeability tensor for an anisotropic arbitrarily fractured rock subjected to arbitrary deformations unlike the original liu elsworth approach our formula may therefore be used confidently in situations involving any stress and strain states including those that are non diagonal and with rocks with any distribution of fracture orientations including those that are non orthogonal this is advantageous in numerical simulation and in mining situations that frequently involve such situations our formula adds no discernible computational load to numerical simulations our proposal agrees with lab and in situ direct and indirect tests of permeability

chemostratigraphy of the lower arroyo del soldado group vendian uruguay and palaeoclimatic implications abstract new c and o isotopic determinations from the vendian lower arroyo del soldado group are reported and combined with sedimentologic and biostratigraphic data on the basis of different geochemical and petrographic criteria the primary nature of the c and sr isotopic signature is shown positive d 13 c values characterize the mainly siliciclastic upper yerbal formation which contains oxide facies bif and a diverse assemblage of skeletal fossils including cloudina riemkeae a series of positive and negative d 13 c excursions occur up section in the overlying polanco formation mainly composed of limestones and limestone dolostone rhythmites the transition to the overlying barriga negra and cerro espuelitas formation which consists of conglomerates and shales cherts bif respectively is marked by a further negative excursion on the basis of sedimentary structures a correlation of d 13 c with palaeobathymetry is established positive d 13 c peaks are associated with high sea level stand high organic carbon burial and relatively higher microfossil diversity while negative d 13 c excursions occur in carbonates with less organic matter less microfossil diversity and are always associated to regressions these observations can be readily explained by palaeoclimatic models which postulate that enhanced bioproductivity due to higher availability of nutrients p n fe was the key factor controlling neoproterozoic glaciations the mentioned models are discussed in view of the new data the occurrence of at least four cold periods in the upper vendian is envisaged these cold periods led to sea level fall and possibly glaciation at higher latitudes the absence of glacigenic rocks associated to negative d 13 c excursions in the arroyo del soldado group is probably due to the tropical setting of the basin finally the upper vendian age of the lower arroyo del soldado group is confirmed on the basis of c and sr isotopes the onset of carbonate deposition at the base of the polanco formation is estimated at 580 ma by comparison with existing global isotopic curves

redistribution of rare earth elements thorium and uranium over accessory minerals in the course of amphibolite to granulite facies metamorphism the role of apatite and monazite in orthogneisses from southwestern norway the amphibolite to granulite facies transition has been studied in a high k calc alkaline hornblende biotite k feldspar megacrystic augen gneiss series from the rogaland vest agder rog va sector of the sveconorwegian province southwest norway hornblende begins to break down mainly to clinopyroxene at the cpx in isograd and biotite mainly to orthopyroxene at the opx in isograd abbreviations for minerals following kretz 1983 the magmatic accessory mineral association comprises titanite and allanite which begin to break down before the cpx in isograd titanite is preserved as relict inclusions in other minerals at higher grade monazite and thorite formed in the breakdown of allanite monazite abundance reaches a maximum between the cpx in and opx in isograds the middle and heavy rare earth element m hrees except eu content of apatite steeply increases with increasing metamorphic grade and is directly correlated to the decrease of the modal abundances of titanite hornblende and biotite the u contents of apatite are low and do not increase with metamorphic grade the light rare earth elements lrees and th content of apatite are not correlated to the breakdown of allanite around the cpx in isograd but increase around the opx in isograd a simplified equation is proposed for monazite crystallisation in the vicinity of the cpx in isograd that accounts for the allanite titanite and hornblende breakdowns and the m hree substitution in apatite 3 m hree 2o3in hornblende and litanite 3 lree 2in allaniteo3 2ca5 po4 3apatite f oh 6sio2quartz 6 lree pmonaziteo4 2ca2 m hree 3 sio4 3 f oh lessingite in apatite 6caoin plagioclase at the opx in isograd the increase of lrees and th content of apatite results either from the breakdown of some monazite 3 lree po4monazite 3sio2quartz 4caoin plagioclase f2 h2o fluid ca5 po4 3 f oh apatiteca2 lree 3 sio4 3 f oh less ingite in apatite or the breakdown of the remaining allanite 3 lree 2o3in allanite 6sio2quartz 4caoin plagioclase f2 h2o fluid 2ca2 lree 3 sio4 3 f oh lessingite in apatite the release of fluorine from the breakdown of biotite at the opx in isograd may increase apatite stability relatively to monazite in the granulite facies when compared to amphibolite facies the granulite facies augen gneisses do not show any u or th depletion this means that changes in the accessory mineral associations and the simultaneous breakdown of hydrous minerals at the amphibolite granulite facies transition do not inevitably result in depleted granulite facies rocks but rather to an isochemical element redistribution the coexistence of small amounts of metamorphic monazite and of relict inclusions of titanite in upper amphibolite facies augen gneisses suggests that high k calc alkaline orthogneisses are a suitable material to date with the u pb method prograde path of amphibolite facies regional metamorphism on monazite and the cooling path on titanite

petrogenesis of a mid proterozoic anorthosite mangerite charnockite granite amcg complex isotopic and chemical evidence from the nain plutonic suite the nain plutonic suite nps about 1 30 ga underlies some 19 000 km intruding the boundary between middle to late archean rocks in the east nain province and late archean and early proterozoic rocks in the west churchill province nd isotopic compositions in most igneous units of the nps reflect their geographic position relative to the inferred boundary between the nain and churchill provinces rare exceptions are local intrusions of olivine bearing basic rocks with highest epsilon nd 1 3 ga near 3 0 present in both eastern and western sectors of the nps anorthositic rocks have variable and significant contributions of crustal nd but notably lower i sr than granitoid rocks ferrodiorites are similar isotopically to the anorthositic group and have chemical and mineral compositions more akin to the anorthositic group than the granitoids aluminous orthopyroxene megacrysts in nps anorthositic rocks indicate crystallization pressures of 6 2 to 11 0 kbar consistent with lower cru

mineralogy geochemistry and petrology of neoarchean ferroan to magnesian granites of carajas province amazonian craton the origin of hydrated granites associated with charnockites abstract 2 75 to 2 73 ga old granitic intrusions associated with coeval charnockitic rocks were emplaced in the northern domains of the carajas province the vila jussara suite was recognized recently and its geologic mineralogical and geochemical characteristics are presented in this paper and compared with the data available in the literature on the estrela complex serra do rabo and igarape gelado granites and planalto suite monzogranites and syenogranites are dominant in most units but in the igarape gelado granite and vila jussara suite granodiorites and tonalites are also relatively abundant the main mafic phases in all these granitoids are amphibole potassian hastingsite with subordinate magnesiohastingsite 0 95 fe fe mg 0 47 and biotite 0 88 fe fe mg 0 52 with rare occurrence of clinopyroxene relict crystals magmatic epidote of pistacite component from 26 to 31 occurs only in the vila jussara suite the rocks of estrela serra do rabo and planalto units contain only ilmenite generally with coronas of titanite or ilmenite associated with magnetite and are essentially reduced ferroan granites whole rock feot feot mgo 0 89 that evolved at low f o 2 fmq 0 5 the igarape gelado granite needs additional studies but it is formed apparently by reduced ferroan and oxidized ferroan granites the vila jussara suite is also composed of reduced ferroan granites that are similar to those of the other granite units however it has additionally oxidized ferroan and magnesian granitoids which contain magnetite ilmenite as the main fe ti oxide phase and evolved respectively at moderate f o 2 nno 0 5 and at comparatively higher f o 2 nno to nno 1 the magmas of these granites were formed at temperatures 900 c and derived from a heterogeneous dominantly reduced and tholeiitic granulitic crust locally varying to oxidized and calc alkaline in composition plagioclase orthopyroxene clinopyroxene and fe ti oxides were the main phases in the melt residues and the liquids were enriched in ba zr y and ree except for eu but not in sr compared to their sources the magmas should have relatively high water content 4 wt the magmatic evolution was strongly influenced by partial melting processes the different varieties of the vila jussara suite are not linked by fractional crystallization and derived from distinct magmas the neoarchean granites of the carajas province were emplaced in a collisional tectonic setting they are syntectonic granites that were deformed and sometimes intensely recrystallized during their emplacement and subsequent subsolidus cooling the magmas were generated in the crust at pressures of 800 to 1000 mpa and emplaced at pressures of 200 to 500 mpa the studied granitoids are similar geochemically to the ferroan and magnesian groups of charnockites the magnesian variety of the vila jussara suite is similar to the pyroxene free granitoids of the neoarchean matok pluton of the collisional limpopo belt the neoarchean granites of carajas are hydrated granites emplaced at comparatively higher crustal levels when compared with the matok pluton

late paleoproterozoic tectonic setting of the northern margin of the north china craton constraints from the geochronology and geochemistry of the mangerites in the longhua and jianping areas abstract the tectonic setting of the late paleoproterozoic suite of anorthosite mangerite charnockite and alkali feldspar granite amcg on the northern margin of the north china craton ncc is controversial this paper reports on the petrology geochronology and geochemistry of the beibaiqi beipuzi and shibalitai mangerites in the longhua area and the shinao mangerite in the jianping area zircon u pb dating reveals that these mangerites formed 1768 1725 ma similar to the other lithologies 1753 1673 ma of the amcg suite on the northern margin of the ncc the mangerites have intermediate sio2 contents 57 2 66 8 wt and high k2o 4 04 7 05 wt and na2o 3 75 5 50 wt contents which belong to alkaline series rocks they are enriched in light rare earth elements rees and large ion lithophile elements liles of rb ba and k and they are depleted in heavy rees and the high field strength elements hfses of th u nb ta ti and p the zircon hf t values of these mangerites are negative 8 3 to 1 7 with depleted mantle model ages tdm and average crustal two stage modal ages t2dm from 2250 ma to 2533 ma and 2573 ma to 2959 ma respectively these geochemical characteristics suggest that these mangerites originated from the early precambrian lower crust of the ncc compared with the mangerites the other lithologies of the amcg suite display different evolutionary trends of their major elements and different distribution patterns of their rees and trace elements indicating that those lithologies were not formed through fractional crystallization by the same primary magma the anorthosites share similar distribution patterns of rees and trace elements and zircon hf isotopic composition with associated norites the data suggest that the anorthosites were formed by noritic magmas through fractional crystallization at the base of the lower crust the alkali granites and rapakivi granites display the geochemical features of a type granites and might have originated from partial melting of the mid upper crust combined with regional geological data these findings suggest that the amcg suite occurred in a post collisional post orogenic extensional setting rather than an anorogenic continental rift setting

a model for monazite melt equilibrium and application to the generation of granitic magmas abstract in order to model the behaviour of zr hf ti p u th y and the rare earth elements ree in the continental crust the parameters which control the equilibria between accessory minerals and granitic melts must be determined this paper proposes equations for the equilibrium between monazite and ca poor felsic melts in a first step all the light ree are considered as a single component and an equation describing monazite solubility is deduced from the available experimental data in a second step the fractionation of ree by monazite is investigated on the basis of a natural example of coexisting monazite and obsidian from macusani peru the solubility of monazite can be used as a thermometer based on the total ree content of natural magmatic rocks application of ree thermometry to various peraluminous rock series suggests that it is a reliable tool for determining temperatures of magmatic processes the equation governing ree fractionation by monazite is used to discuss genetic relationships between a melt and a presumed parental rock using the composition of the monazite in the parental rocks and the ree pattern of the daughter rock this method has been applied successfully to high himalayan manaslu and tibetan slab granites it is suggested that detailed petrographical work on monazite including electron microprobe analyses and sem imaging of its internal structures combined with the model presented here can be a useful tool for deciphering the genesis and the differentiation of peraluminous granitic magmas in the continental crust

igneous charnockites and related rocks from the bjerkreim sokndal layered intrusion southwest norway a jotunite hypersthene monzodiorite derived a type granitoid suite the upper part of the bjerkreim sokndal layered intrusion bksk introduction comprises a suite of charnockitic granitoids mangerite quartz charnockitic granitoids are a major component of mangerite and charnockite with some jotunites the petrology and anorthosite mangerite charnockite rapakivi granite geochemistry major and trace elements of eight main rock types amcg complexes and therefore play a crucial role in 88 samples are considered the rocks form a suite of k2o rich the formation and evolution of the proterozoic crust alkali calcic granitoids of a type deriving from jotunitic magma their origin has been long debated though intimately two trends of inferred liquids are distinguished the main liquid associated with massif anorthosites they are generally line of descent which passes from jotunites through two pyroxene considered to be derived from distinct parental magmas quartz mangerites to amphibole charnockites the second one which generated in different sources emslie 1978 1991 morse encompasses olivine bearing quartz mangerites and charnockites and 1982 duchesne 1984 wiebe 1992 ashwal 1993 it is rooted into mangeritic liquids comparison with the tellnes rock has however been recognized that some charnockitic series reveals that contamination by leucogranitic material has taken rocks could also be derived from an intermediate monplace simultaneously with fractional crystallization in both bksk zodioritic to ferrodioritic jotunitic magma duchesne trends zr rb cs and th are particularly sensitive to assimilation et al 1989 wilmart et al 1989 owens et al 1993 and the higher water content in bksk zircon and apatite have whose origin is also controversial the jotunitic magma saturated at the liquidus of quartz mangerite around 900 c close could either be derived from a crustal source by the to the fayalite magnetite quartz fmq buffer the two pyroxene partial melting of basic rocks duchesne et al 1989 quartz mangerites cannot have been equilibrated with the mangerite duchesne 1990 or be residual magmas after the forcumulates on which they rest a major influx of magma took place mation of massif anorthosites which have been conwhen mangeritic cumulates were being deposited it mingled and partly mixed with the resident contaminated magma taminated to various degrees by crustal material emslie et al 1994 the latter hypothesis seems to explain a large number of amcg complexes in the grenville and nain provinces and elsewhere accepting that some charnockites are derived from jotunites there is a logical

syn collisional lower continental crust anatexis in the neoproterozoic socorro guaxupe nappe system southern brasilia orogen brazil constraints from zircon u pb dating sr nd hf signatures and whole rock geochemistry abstract the southern brasilia orogen occurs along the southernmost border of the sao francisco craton this orogen is structured as a pile of ediacaran syn metamorphic thicked skinned nappes that diachronically migrate toward the cratonic margin a magmatic arc environment is represented by the socorro guaxupe nappe sgn which is a thick segment of partially molten lower to middle continental crust the sgn comprises three main units a lower granulitic an intermediate diatexitic and an upper metatexitic high temperature metamorphic peak was reached at 625 ma when large volumes of high k diatexitic rocks were formed charnockitic and mangeritic magmatic rocks sao jose do rio pardo suite and in situ leucosomes of mafic composition are inferred to have formed under hornblende dehydration melting conditions i e t 850 c granitic diatexites pinhal type were also formed and zircon thermometry indicates t 850 c elemental and isotopic geochemistry indicate that these diatexites and in situ leucosomes derived from melting of lower to middle continental crust tims zircon u pb ages are presented for the lower and middle units u pb dating coupled to lu hf analysis la mc icp ms was performed on charno enderbitic in situ leucosomes from metatexitic rocks that also resulted from hornblende dehydration melting two different zircon typologies were recognized the first comprises bipyramidal prismatic grains with oscillatory zoning and high luminescence sometimes preserving low luminescence 670 ma cores the high luminescence grains show 19 concordant ages at 621 16 ma the second typology comprises isometric or soccer ball type grains these grains show sector zoning and a concordia age of 608 4 ma th u ratios from soccer ball grains vary from 1 253 to 2 107 whereas prismatic grains vary from 0 118 to 1 774 initial hf signatures between 13 and 21 in both typologies provide evidence of a reworked crustal reservoir the older prismatic grains may be related to the onset of metamorphic peak 625 ma whereas the isometric ones provide evidence of long lived high t conditions until 610 ma

ichnological signatures of shallow freshwater lakes in the glacial itarare group mafra formation upper carboniferous lower permian of parana basin s brazil abstract the upper carboniferous lower permian glacigenic deposits of the itarare group parana basin are widely known and cover an extensive area in the southern brazil these deposits consist of different arrangements of massive shales diamictites rhythmites and fine to medium grained sandstones with trough cross stratification five genetically distinct thickening locally coarsening upward successions of regular rhythmites can be distinguished in the mafra rio negro region santa catarina and parana states southern brazil representing the landward portion of an incised valley filled during deglaciation a low diversity invertebrate ichnofauna composed of a freshwater shallow burrow dominated suite and trackway dominated suite occurs in these rhythmites the freshwater shallow burrow dominated suite is composed of cochlichnus anguineus cruziana cf problematica gordia arcuata gordia marina hormosiroidea meandrica rusophycus cf carbonarius and treptichnus pollardi as well as undichnia consulca and intermittent rusophiciform traces it represents a mermia ichnocoenosis and occurs in the rhythmites of the upper sets commonly overlapped by d gouldi and d biformis in palimpsest preservation d gouldi and d biformis compose the trackway dominated suite which occur in all ichnofossiliferous paired mudstone siltstone of the basal sets of the rhythmite succession and in almost all of the upper sets it represents an atypical scoyenia ichnocoenosis and is generally preserved over microbially induced wrinkle structures the rhythmic deposition suggests distal underwater gravity flow deposits filling shallow lakes or ponds in depressed areas the siltstones deposited by melting currents and the mudstones by sediment fall out after the flux ceased the abundant wrinkle structures suggest quiet waters the overlying deposits bearing a brackish water ichnofauna and marine fossils suggest a coastal setting connected with the sea although atypical the occurrence of a scoyenia ichnocoenosis in almost all ichnofossiliferous rhythmite couplets preserved over wrinkle structures or overlapping mermia ichnocoenosis suggests that these shallow lakes were episodically dried up at least partially the present data allow interpreting the regular ichnofossiliferous rhythmites of the mafra formation as deposited in shallow lakes or ponds developed in outwash plains at the landward side of a fjord embayment during deglaciation

geochemistry of the guaxupe granulites minas gerais brazil abstract geochemical data for granulite terrain are presented in the northernmost portion of the guaxupe massif at mantiqueira province se brazil several types of granulites are recognized in the area basic intermediate and acid granulite major and trace elements including ree point to only one magma source for these granulites generated at different times geochemical data point to plagioclase and apatite fractionation as the responsable by the ree behaviour in intermediate and more basic rocks overall composition of the guaxupe granulites is similar to average described worldwide in the literature to the lower crust

hydraulic conductivity changes and influencing factors in longwall overburden determined by slug tests in gob gas ventholes abstract this study presents the results of core log analyses from the exploration boreholes the analyses of face advance rates and the results of downhole monitoring studies performed in gob gas ventholes for calculation of changes in hydraulic properties in the longwall overburden at a mine site in southwestern sw pennsylvania section of northern appalachian basin in the first part of the study coal measure rocks in overburden strata were analyzed and the locations where possible fractures and bedding plane separations would occur were evaluated in the second part the hydraulic conductivities were computed by two different slug test analyses methods using the water level changes measured in gob gas ventholes as longwall face approached hydraulic conductivities were analyzed with respect to the changes in overburden depth the locations of the borehole and mine face advance rates these data were used to interpret the potential productivities of the gob gas ventholes as a result of fracturing and changes in hydraulic conductivities the general results showed that the probability of fracturing and bedding plane separations in the overburden increase between strong and weak rock interfaces also the probability of bedding plane separations increases as the interface is close to the extracted coal seam evaluation of slug tests showed that the hydraulic conductivity developments in the boreholes and their potential production performances are affected by the underground strata and the roof materials in situations where the roof material is stiff and thick the development of high permeability fractures around the borehole will be less results also indicated that borehole location with respect to face position affects the fracturing time and permeability evolution as well greater overburden depths generally cause earlier fracturing as longwall face approaches but eventually result in lower hydraulic conductivities and potentially less effective boreholes increasing mining rates also resulted in generally lower hydraulic conductivities in the overburden the results of this study were intended to improve the interpretation of gob gas venthole performance and to provide better siting of these boreholes

u pb age of detrital zircon from the embu sequence ribeira belt se brazil abstract the embu complex crops out in the southeastern part of sao paulo state in brazil and consists mainly of neoproterozoic metasedimentary rocks belonging to the interference zone between the brasilia and ribeira fold belts we present u pb ages la ipcms supported by cathodoluminescence images for detrital zircon from these rocks in order to constrain the formation and evolution of the source area of this complex in this paper we choose to individualize within the embu complex a paleoproterozoic basement a metasedimentary sequence the embu sequence and neoproterozoic intrusive bodies now largely orthogneisses six distinct rock types were recognized in the embu sequence biotite gneiss biotite schist quartzite amphibolite calc silicate rock and talc schist the sequence is strongly deformed by several deformation phases and metamorphosed into amphibolite facies an important shear zone the buquira shear zone separates the embu complex from the socorro guaxupe nappe to the north considered to be part of the upper plate of the southern brasilia belt collision however our mapping showed that the shear zone cuts obliquely into the embu complex diminishing considerably its regional importance three samples were separated for dating a schist north of the shear zone and two quartzites south of the shear zone the results show that the ages of detrital zircon of these samples are mainly paleoproterozoic with a minor archean component the youngest igneous zircon grain from the schist produced an age of about 1000 ma indicating the maximum sedimentation age for the sequence no significant difference appears between the samples north and south of the shear zone reforcing the interpretation that this zone is only of local importance important metamorphic overgrowth of zircon in the age range 670 640 is present in all three samples it is interpreted as related to the installment of a continental magmatic arc in the socorro guaxupe nappe and in the embu complex a second metamorphic pulse between 621 and 599 ma is only apparent in one sample according to the literature this was the period of continental collision between the paranapanema and sao francisco paleocontinents leading to the formation of the southern brasilia belt possibly the fact that the analyzed samples are localized some 30 km away from the suture in the upper plate explains that the increase in temperature during the collision in this area was insufficient to grow significant new zircon a third metamorphic pulse with ages of 576 574 ma possibly related to collision in the ribeira belt is only detected in three analyses of metamorphic rims in the schist sample earlier reported ages of about 790 ma both for igneous crystallization and metamorphism in a more westerly part of the embu complex are only recognized in one analysis of metamorphic overgrowth 794 24 ma from the schist sample and two probably hybrid analyses of 830 19 ma and 767 14 ma from the northern quartzite sample it is concluded that the results show that the detritic zircon is probably derived from the paranapanema paleocontinent

determination of actual limit angles to the surface and their comparison with the empirical values in the upper silesian basin czech republic abstract this study deals with the determination of the actual limit angles in the long term formed subsidence basin in the czech part of the upper silesian basin the remaining part lays in poland here there was the most extensive underground exploitation of black coal in the north east of the czech republic a limit angle is absolutely decisive in the determination of deep mining influences in relation to the current and future utilisation of this territory the two csm and paskov mine localities on the edge of the subsidence basin were selected for this study since they could not have been affected by mining in neighbouring mines on the grounds of the long term levelling monitoring of points on the surface which started prior to mining the horizontal distance between the mined out area and the undisturbed ground surface was identified the impact of limit angle on the surface was calculated by means of the horizontal distance and the established mining depth such identified actual limit angles reached the values of 36 at the csm mine and 25 for the paskov mine the calculated values are significantly lower when compared with the currently applied empirical values of 57 for the csm mine and 56 for the paskov mine this means that the extent of the undermining effects is unambiguously wider by 611 m at the csm mine and by 883 m at the paskov mine this study thus establishes the existence of a significantly vaster area influenced by coal deep mining than previously expected the identified facts lead to the conclusion that regular revisions and follow up updates of the empirically determined parameters are recommended

petrology and geochemistry of the neoproterozoic guaxupe granulite facies terrain southeastern brazil abstract geochemical and oxygen isotopic data on the neoproterozoic granulite facies rocks enderbites charnockite and charnokitic augen gneisses of guaxupe brazil are assembled geochemical discrimination function calculations show an igneous origin for majority of the rock types in the area major and trace element data especially ree are similar to tonalite and granodiorite oxygen isotope composition for charnockitic gneisses and mafic granulites yield 18o values in the range of 8 8 to 11 and fall in the range of quartzofeldspathic rocks of medium to high grade terrains elsewhere a small scale variation of 18o values compatible with the chemical data imply the preservation of pre metamorphic oxygen isotope compositions minimum peak pressure temperature conditions are 8 5 kbar and 850 c the high grade metamorphism did not appear to have altered significantly the geochemical and oxygen isotope compositions of the protoliths approximately 2 5 kbar of pressure decrease accompanied by 200 c cooling has been recorded for a portion of the cooling path the p t path is consistent with a single event namely the formation and uplift of the guaxupenappe in the neoproterozoic brasiliano cycle

seepage prevention of mining disturbed riverbed abstract coal mining under a body of water introduces a potential risk of water inrush to the mine based on the practice of coal mining near the jinsha river in gansu province china and focused on the seepage prevention of the mining disturbed riverbed the surface movement failure characteristics of the overburden strata and water percolation induced by mining underneath the river have been investigated by means of in situ monitoring physical modeling and discrete element numerical simulation a flexible anti seepage scheme four element structure fes is put forward to protect the riverbed from seepage and the structure can harmonize and buffer the mining induced deformation of the surface land upward from the bottom of the riverbed fes is composed respectively of reinforcement layer which plays the roles of strengthening the riverbed buffering the deformation and enhancing the integrity of the riverbed bedding course layer which prevents the anti seepage layer from folding damage due to dislocation and sharpness in the riverbed meanwhile it can absorb localized deformation anti seepage layer which is a major anti seepage texture made by geo membrane with the properties of water proof a high strength good flexibility and ductility protective layer which covers the geo membrane by a layer of precast reinforced concrete bricks to fix and protect the anti seepage layer in addition treatment principles are proposed for reshipping of the river path in plane the stream gradient along the longitude and the shape of cross section of the riverbed and a comprehensive seepage prevention system is established

reservoir simulation based modeling for characterizing longwall methane emissions and gob gas venthole production abstract longwall mining alters the fluid flow related reservoir properties of the rocks overlying and underlying an extracted panel due to fracturing and relaxation of the strata these mining related disturbances create new pressure depletion zones and new flow paths for gas migration and may cause unexpected or uncontrolled migration of gas into the underground workplace one common technique to control methane emissions in longwall mines is to drill vertical gob gas ventholes into each longwall panel to capture the methane within the overlying fractured strata before it enters the work environment thus it is important to optimize the well parameters e g the borehole diameter and the length and position of the slotted casing interval relative to the fractured gas bearing zones this paper presents the development and results of a comprehensive dynamic three dimensional reservoir model of a typical multi panel pittsburgh coalbed longwall mine the alteration of permeability fields in and above the panels as a result of the mining induced disturbances has been estimated from mechanical modeling of the overlying rock mass model calibration was performed through history matching the gas production from gob gas ventholes in the study area results presented in this paper include a simulation of gas flow patterns from the gas bearing zones in the overlying strata to the mine environment as well as the influence of completion practices on optimizing gas production from gob gas ventholes

numerical analysis and prediction of ground surface movement induced by coal mining and subsequent groundwater flooding abstract ground surface movement shows different features during mining and post mining period if the mine goaf is dry surface subsidence is observed in both periods if the mine goaf is flooded by groundwater however ground surface uplift can be observed although much smaller in amplitude compared to the preceding subsidence a numerical modeling strategy is proposed to predict uplift during the flooding process of an excavated coal mining area under complex geological conditions the modeling approach considers three phases virgin state before mining stage immediately after mine closure flooding phase the model considers elasto plastic material behavior including faults represented by interfaces in situ measurements are used for calibration of the model the oelsnitz abandoned coal mine is used for model validation and prediction the measured subsidences up to 17 m were reproduced as well as the uplift within the last 10 years with values between 0 5 2 0 mm year spatial distribution of uplift areas is well reproduced predictions up to the year 2051 show an increase in uplift velocity between 0 5 3 0 mm year and additional total uplift of up to 300 mm

constraining timing and p t conditions of continental collision and late overprinting in the southern brasilia orogen se brazil u pb zircon ages and geothermobarometry of the andrelândia nappe system abstract the andrel ndia nappe system ans is an important component of the neoproterozoic southern brasilia orogen sbo in se brazil and its evolution is related to the convergence and subsequent collision between the passive margin of the sao francisco paleocontinent and paranapanema block during the brasiliano orogeny the ans is mainly composed of a pile of deformed meta sedimentary rocks that record an inverted metamorphic pattern ranging respectively from amphibolite facies at the bottom to high p granulite conditions at the top the ans is here simplified into the lower middle and upper nappes four samples from different tectonic settings within the ans were collected for zircon isotopic investigation in addition geothermobarometry modelling were performed on seven samples from the middle nappe retro eclogite slices associated to basement gneissic rocks occur along the contact between the upper and middle nappes and have zircon grains with metamorphic rims grown in high p conditions of 12 16 kbar with temperatures of 700 800 c during the continental subduction dated here by u pb shrimp in zircon at 625 6 ma a period of nappe emplacement accompanied by melting in the middle nappe is evidenced by a garnet muscovite staurolite kyanite schist with leucosome parallel to the main foliation dated by u pb shrimp in zircon at 618 5 ma re equilibrium at pressures of 4 7 kbar with temperatures of 500 700 c is ascribed to a second heat pulse under lower pressure conditions the period of melting associated to this event in the middle nappe occurred at 586 9 ma and is marked by an anatectic tourmaline garnet muscovite bearing s type granite this granite body is part of a ne sw belt of granites with ages between 605 and 563 ma and covering both the central ribeira orogen cro and the sbo the age and the alignment of this granite belt justify the interpretation that it is genetically related to the cro thus the new data provide evidence that tectonothermal events related to the collisional front of the cro extended up to 200 km overlapping the consolidated sbo at ca 580 ma

investigation of movement and damage of integral overburden during shallow coal seam mining abstract most prediction methods used to calculate mining induced subsidence are empirical which cannot explain the mechanism of fundamental rock strata movement in this paper based on key stratum theory and the mechanical analysis of overburden a new analytical solution the analogous hyperbola subsidence model ahsm was proposed to describe the movement and damage of inner burden mining induced rock strata movement was verified using the distinct element method udec to assess the performance of the theoretical model three subsidence parameters smax t sgoaf smax d h generally used to describe surface subsidence trough agree with statistical field measurements of the south coalfield in australia the surface subsidence and the movement boundary in the overburden are very close to the theoretical predictions additionally the primary key stratum damages the least in the overlying strata its broken length is the smallest the width of subsidence trough and maximum surface subsidence increase as the primary key stratum drops

the early paleozoic development of bioturbation evolutionary and geobiological consequences abstract bioturbation the physical and chemical mixing of sediments by burrowing animals is a critical engineering process in modern seafloor environments and exerts an important control on not only benthic ecology and sediment properties but also ocean wide biogeochemical cycling well mixed sediments have long been assumed to appear at the precambrian cambrian boundary with the first occurrence of the index fossil and three dimensional burrow treptichnus pedum however field based analyses synthesizing ichnological stratigraphic sedimentological and taphonomic data collected from lower paleozoic successions worldwide indicate that sediment mixing in marine shelf environments remained limited until at least the late silurian 120 million years after the precambrian cambrian transition in spite of early advances in complex modes of infaunalization mixed layer development had a much more gradual trajectory and did not occur in step with the first appearance of three dimensional burrows the delayed appearance of modern style intensities of sediment reworking postdating both the cambrian explosion and the great ordovician biodiversification event may be due to the late stage radiation of mobile infaunal deposit feeders biological bulldozers the organisms which are in modern marine settings the most efficient bioturbators the protracted development of the sediment mixed layer holds important implications for contemporaneous biogeochemical cycling and oxygenation of the ocean atmosphere system the delayed development of intensive sediment mixing may have also mediated exceptional preservation of both fossilized soft tissues and shallow tier trace fossils and may therefore have contributed to the anomalous preponderance of konservat lagerstatten and exceptionally preserved shallow tier trace fossils and bioglyphs characteristic of the lower paleozoic stratigraphic record

analysis of exceptionally large tremors in two gold mining districts of south africa an investigation of ground motion recorded using broad band wide dynamic range digital seismographs of large mine tremors from two south african mining districts with different geologic settings reveals some essential differences in both seismic source and ground motion parameters in the klerksdorp district where the strata are offset by major throughgoing normal faults the largest tremors with magnitudes ranging as high as 5 2 tend to be associated with slip on these pre existing faults moreover the seismic source and ground motion parameters are quite similar to those of natural crustal earthquakes in the carletonville district by contrast where substantial faults do not exist the large magnitude tremors appear to result from the failure of relatively intact rock and cause seismic stress drops and ground motion parameters higher than normally observed for natural shocks additionally there appears to be an upper magnitude limit of about 4 in the carletonville district detailed analyses of an exceptionally large event recorded locally from each of these districts serve to highlight these contrasts

beginning of melting and composition of first melts in the system qz ab or h 2 o co 2 solidus temperatures have been determined for minimum melt compositions in the system qz sio2 ab naalsi3o8 or kalsi3o8 at p fluid 2 5 and 10 kbar and at various water activities the dry solidus was investigated in a dry argon environment water activities ah2o between 0 0 and 1 0 were obtained by using h2o co2 mixtures the or ab or ratio of first melts increases considerably with decreasing water activity at 10 kbar it is 0 28 in the water saturated system and 0 56 at water activity 0 1 the qz content does not change with changing water activities the ab content of minimum melts formed at high pressures and low ah2o may remain almost constant in ascending magmas that are cooling and crystallizing qz content increases at the expense of the or component solidus temperatures decrease considerably when ah2o increases slightly from zero at 10 kbar the temperature difference between dry melting and the solidus for ah2o 0 1 is 120 c the influence of pure co2 on the solidus is very limited in the investigated p t range the solidus is approximatively 760 c at ah2o 0 5 between 2 and 10 kbar and approximatively 830 c at ah2o 0 3 this means that melting of quartz feldspar assemblages may induce dehydration reactions at p t conditions of the granulite facies

mechanism and risk assessment of overall instability induced rockbursts in deep island longwall panels abstract an increasing number of mines in china are being subjected to overall instability induced oii rockbursts in extracting deep remnant island longwall panels causing severe damage at far larger scale and intensity compared with common local rockbursts using the island longwall panel lw1305 at zhaolou coal mine as a case example this paper investigates the mechanism of the newly defined oii rockburst by means of stress and microseismic monitoring and then proposes a straightforward risk assessment method for oii rockbursts based on the actual bearing index in an attempt to provide guidelines for making engineering judgement the proposed risk assessment method was successfully applied to lw1305 and the assessment result is supported by the occurrence of an oii rockburst in lw1305 and further verified by numerical modeling and microseismic monitoring

assessment of rock mass characteristics and the excavation disturbed zone in the lingxin coal mine beneath the xitian river china safe production and induced hazard prevention in coal mines mainly concern problems in the excavation disturbed zone edz but coal mining can also make a significant impact on the environment comprehensive techniques using a borehole tv viewer system electrical logging and monitoring of drilling fluid leakage offer the ability to identify changing geological conditions and the location of any nearby abandoned mining workings the inner collapsed zone and the expanding height of the crack zone transmitting water plus their spatial distribution after excavating the superincumbent coal seam stratum are determined at no l3414 workings lingxin coal mine beneath the xitian river china an integrated system of gis based on a stochastic model which has been developed for the prediction of dynamic subsidence coupling the time function and probabilistic integral method is verified through practice at the lingxin coal mine this development has greatly expanded the ability of the mine operator to characterize previously inaccessible areas of the mine providing a reliable basis for safe mining and prevention of induced hazards to ensure high production mining underneath the river bed

residual liquid origin for a monzonitic intrusion in a mid proterozoic anorthosite complex the sybille intrusion laramie anorthosite complex wyoming the sybille intrusion 100 km 2 is one of three large monzonitic intrusions in the 1 43 ga laramie anorthosite complex of southeastern wyoming the petrographic geochemical isotopic and geophysical characteristics of sybille monzonitic rocks are consistent with an origin by extensive crystallization of liquids residual to nearby anorthositic cumulates ferrodiorites and contamination by archean wall rocks the exposed part of the intrusion is composed mainly of coarse grained monzosyenites with abundant alkali feldspar phenocrysts the monzosyenites preserve mineralogical evidence for high crystallization temperatures 1000 c mid crustal emplacement pressures 3 kbar relatively reduced crystallization conditions 2 log units below the fayalite magnetite quartz fmq oxygen buffer and they crystallized in the presence of a co2 rich fluid phase fuhrman et al 1988 frost and touret 1989 the eastern monzosyenites those adjacent to contemporaneous anorthosite are distinguished by an anhydrous mineral assemblage fo16 fo8 olivine high ca pyroxene lacking modal quartz silica contents of 60 wt and smaller eu anomalies eu eu 1 2 to 1 3 abundant xenoliths of archean wall rocks and anorthosite from the adjacent intrusions in all monzosyenites attest to a stoping emplacement mechanism near the roof of the chamber we propose that the monzosyenites represent a relatively thin 0 5 1 0 km thick roof to a magma chamber dominated by dense ferrodioritic cumulates at depth extensive open system fractionation of a ferrodioritic parent magma residual after crystallization of anorthosite produced fe enriched monzodioritic and or monzonitic magma in the upper part of the chamber and complementary fe and ti rich cumulates in the lower levels we have corroborated the production of monzonitic liquids from crystallization of ferrodiorite through a series of reconnaissance equilibrium crystallization experiments the presence of dense ferrodioritic cumulates at depth is consistent with the prominent positive gravity anomaly associated with the sybille intrusion hodge et al 1973 in the upper parts of the chamber the fractionated monzodioritic and or monzonitic magmas eventually became saturated in alkali feldspar owing to density contrasts the alkali feldspar phenocrysts floated to the roof of the chamber thus producing the exposed porphyritic monzosyenites in addition the roof of the chamber was the site of significant melting of archean gneiss and locally metapelite the sr and nd isotopic compositions of the monzosyenites with sr isotopic ratios becoming increasingly radiogenic from east i sr 0 7059 and initial nd 2 5 to west i sr 0 7092 and initial nd 2 6 are consistent with a 5 to 15 addition of archean orthogneiss to a ferrodioritic parent magma that had isotopic characteristics similar to adjacent anorthositic rocks the stratigraphic and compositional similarity of the sybille monzosyenites to mangerites in the bjerkreim sokndal intrusion of the rogaland anorthosite complex southern norway indicates that similar open system magmatic processes are capable of having produced high temperature k rich monzonitic rocks in other proterozoic anorthosite complexes

formation of fractured zones in overburden due to longwall mining the fractured zones caused by mining were studied in the overburden of the torezko snezhnyanskaya area ukraine through the change in natural gas emission from these zones during longwall coal excavation zones of interconnected fractures and separate horizontal fractures were studied with vertical wells drilled from the ground surface down to active underground workings the maximum heights of the zone of interconnected fractures and separate horizontal fractures may reach 19 41 and 53 92 times the thickness of the coal seam respectively it was found that the ratio between the maximum height of the zone of interconnected fractures and the thickness of the extracted coal seam increases with the increasing number of rock layer interfaces and decreases with the increasing stiffness of immediate roof it is shown that the growth of the zone of interconnected fractures occurred during 17 39 days at an average rate of 0 94 1 97 m day 1 and it was accompanied by increasing methane emission from overburden observation shows that the formation of separate horizontal fractures began only 11 49 5 days after the height of the zone of interconnected fractures reached its maximum value formation of separate horizontal fractures in overburden over the longwall excavation occurred as a stepped process from lower to upper sandstone sandy shale layer interfaces in the direction of the ground surface

double flow behavior observed in well tests of an extremely heterogeneous mine spoil aquifer abstract a radial flow investigation was performed to examine hydraulic characteristics of a heterogeneous unconfined mine spoil aquifer formed by reclamation of surface mine overburden slug test estimates of hydraulic conductivity k range over four orders of magnitude from 10 6 to 10 2 m s and display two prominent statistical modes ascribed to fine matrix and coarse rubble zones respectively a large proportion of wells displayed either of two anomalous slug test response patterns attributable to zones of highk around or near the well slug test estimates of matrixk appear unbiased but those of high conductivity zones are thought to contain error induced by local heterogeneity and drainage of storage from near the water table numerical simulation of slug tests suggests that high k zones vertically continuous to the water table and either in the annulus of e g well skin or in close proximity to the well may produce response similar to that observed it is not possible to distinguish well skin from heterogeneity effects based on the nature of slug test response alone pumping yields however are generally higher for wells with anomalously rapid slug test response and suggest that in some cases the heterogeneity extends to large distance from the well despite their local region of influence slug tests in such extremely heterogeneous aquifers may encounter highly conductive zones that may reduce the reliability of their results if they permit water table drainage to the well

a system to mitigate deep mine tremor effects in the design of civil infrastructure deep mining may induce quakes reaching magnitude ml of 4 5 to 5 5 and leading to surface ground motion with modified mercalli intensities up to viii such strong ground motions may cause serious damages in civil infrastructure in the vicinity of mines however any adaptation of a classic seismic code in design faces an impending problem of differences in spectral content and duration between the surface records of the rockbursts and natural earthquakes as well as in their different risk definitions this paper presents a system to define design seismic load based on forecasted surface horizontal particle velocity from the rockbursts expected during the planned mining activities such forecasts are routinely prepared by the geophysical mine services respective seismic load may then be applied in the design of buildings and other structures to mitigate the rockburst induced seismic effects on them for this purpose the european seismic code eurocode 8 is adapted

deformation failure and permeability of coal bearing strata during longwall mining abstract to mitigate water shortage a few groundwater reservoirs are being built at the daliuta coal mine shaanxi province china it is essential to investigate the deformation failure and permeability of coal bearing strata during longwall mining and their influences on the construction of groundwater reservoirs in this paper the local geology was introduced briefly and the complete stress strain and permeability for different rock samples were investigated using laboratory experiments and then a three dimensional coupling model between stress and permeability was proposed after that a series of numerical simulation was performed to investigate the dynamics of stress permeability coefficient using flac3d it turns out that due to the relatively low mechanical strength of the coal bearing strata at the daliuta coal mine there are only two zones above the goaf that is caving zone and fracture zone and the fracture zone extends directly to the surface the rock mass permeability is closely related to the stress strain and the permeability decreases with the rise of stress in the stage of elastic deformation while it increases significantly in the stages of plastic deformation and failure the maximum value of permeability coefficient appears in the stage of strain softening and the value varies greatly with the rock lithology during the advancement of longwall face the redistribution range is much wider for permeability than for rock failure and the permeability is the largest on the periphery of goaf rock mass with increased permeability is horizontally oval shaped and vertically saddle shaped the permeability of coal seam roof and floor experiences three stages decrease increase and gradual recovery during coal mining the results are in good agreement with those of physical modeling and field observation the outcomes may contribute to the site selection and construction of the groundwater reservoir at the daliuta coal mine

reconciling longwall gob gas reservoirs and venthole production performances using multiple rate drawdown well test analysis abstract longwall mining is an underground mining method during which a mechanical shearer progressively mines a large block of coal called a panel in an extensive area during this operation the roof of the coal seam is supported only temporarily with hydraulic supports that protect the workers and the equipment on the coal face as the coal is extracted the supports automatically advance and the roof strata cave behind the supports caving results in fracturing and relaxation of the overlying strata which is called gob due its highly fractured nature gob contains many flow paths for gas migration thus if the overlying strata contain gassy sandstones or sandstone channels gas shales or thinner coal seams which are not suitable for mining then the mining induced changes can cause unexpected or uncontrolled gas migration into the underground workplace vertical gob gas ventholes ggv are drilled into each longwall panel to capture the methane within the overlying fractured strata before it enters the work environment thus it is important first to understand the properties of the gas reservoir created by mining disturbances and second to optimize the well parameters and placement accordingly in this paper the production rate pressure behaviors of six ggvs drilled over three adjacent panels were analyzed by using conventional multi rate drawdown analysis techniques the analyses were performed for infinite acting and pseudo steady state flow models which may be applicable during panel mining dm and after mining am production periods of ggvs these phases were analyzed separately since the reservoir properties due to dynamic subsidence boundary conditions and gas capacity of the gob reservoir may change between these two stages the results suggest that conventional well test analysis techniques can be applicable to highly complex gob reservoirs and ggvs to determine parameters such as skin permeability radius of investigation flow efficiency and damage ratio the insights obtained from well test analyses can be used for a better understanding of the gob and for designing more effective gob gas venthole systems

response of seismic activity in mines to the stress changes due to mining induced strong seismic events the influence of the static stress transfer due to two stronger seismic events from one mine section on subsequent seismicity linked to the same section is studied the first strong tremor was provoked by destressing blasting the static stress transfer caused by this tremor had apparently a triggering effect for the occurrence of the second strong event this second event occurred in less than three weeks after the first one and on the area of simultaneous enhancement of both shear and normal components of the coulomb stress change caused by the first event it appears also that in the next few months the cumulative stress change due to both the events influenced significantly the location and rate of smaller subsequent events interestingly contrary to the results of previous analyses the negative coulomb stress changes turn out to have a major role in this respect the coseismic stress change impact even seems to prevail over the influence of time varying stress alteration caused by advancement of the mining front

improvement of methane drainage in high gassy coal seam using waterjet technique traditional methane drainage methods including conventional ventilation and boreholes drilled in the coal seam are widely used in modern coal mining operation in china however it is often noted that the gas drainage presents low efficiency in most coal mines due to low permeability of the coal seam which not only affects the safety but also the productivity of the coal mine this paper describes the development and application of the waterjet cutting system which is used to create artificial fractures and increase the permeability of coal seam for the improvement of methane drainage in underground coal mines in china according to underground monitoring a significant improvement of methane drainage efficiency of up to 3 to 6 times over the traditional methods has been achieved

reduced rapakivi type granites the tholeiite connection reduced rapakivi type granites are the most iron enriched and reduced i e least oxidized of the anorogenic granite association the low oxygen fugacity and chemical composition of these granites severely limit their sources in this paper we argue that reduced rapakivi type granites and their eruptive equivalents high potassium fayalite rhyolites are derived from mafic sources because tholeiitic magmas and their derivatives have the required low oxygen fugacity reduced rapakivi type granites are produced either by extreme differentiation of basaltic melts or by partial melting of underplated basalts and their differentiated equivalents they form in extensional environments where the asthenosphere is present at shallow depths we envision three stages in the origin of these rocks 1 tholeiitic melts are emplaced at the base of the crust 2 continued introduction of heat partially remelts these tholeiitic rocks and 3 the hot dry melts so produced migrate into the middle crust to produce rapakivi batholiths or erupt as rhyolites partial melting of felsic continental crust may accompany the intrusion of rapakivi type magmas thereby producing the other metaluminous and peraluminous granite compositions of the anorogenic suite

field investigation of fractures evolution in overlying strata caused by extraction of the jurassic and carboniferous coal seams and its application case study abstract in multiple seam coal mining the fractures induced by the mining of the lower coal seam may propagate to the goaf of the upper coal seam that is mined earlier the fracture connection leads to the leakage of hazardous gas to fully understand the gas leakage due to fracture evolution the electromagnetic based measurement system and the borehole televiewer were adopted in the panel no 8100 in tongxin coal mine datong coalfield china the coal seam thickness is 15 m and it was mined by top coal caving method the resistivity and fracture pattern in distinct zones of rock stratum were detected and the correlation between them was explained clearly we found that the fracture evolves in two stages as the panel working face advances i e fracture propagation and fracture re closure the maximum height of fracture propagation is 150 m in which the height of the caved and the fractured zones are 80 m and 70 m respectively these fractures start to be compacted and are re closed at the distance of 80 m behind the working face the extraction of the panel no 8100 results in the formation of a gas bearing zone gbz with separations and shear fractures rather than connecting the goafs of the carboniferous coal seam ccs and the jurassic coal seam jcs the gbz is located in a region from 80 m to 150 m above the goaf and 80 m behind the working face based on the above findings effective gas drainage approach is proposed to reduce the concentrations of the hazardous gases consisted of ch4 and co after gas drainage the maximum concentrations of ch4 and co drop to 0 5 and 16 63 ppm with reductions of 53 7 and 33 9 respectively

prediction of the height of destressed zone above the mined panel roof in longwall coal mining abstract longwall mining is one of the most widely used underground mining methods most suitable in relatively flat lying thick and uniform coalbeds due to extraction of the coal seam the panel roof strata above the mined zone will be destressed and then the roof loads will be redistributed and transferred to the front abutment and neighboring solid sections with higher load bearing capacity where the adjacent access tunnels and the corresponding barrier pillars are located the height of destressed zone hdz in this paper is taken as equivalent to the combined height of the caving and fracturing zones above the mined panel roof induced due to longwall mining the height of destressed zone plays a vital role in accurate determination of the amount of loads being transferred towards front abutment and panel sides the paper describes the mechanism of development of the height of this zone finally five new simple yet conclusive mathematical approaches to estimate the height of destressed zone are presented the results of the methods proposed are compared with each other and with the comparable methods the methods proposed are further compared and verified with in situ measurements reported in the literatures the comparative results confirm the agreement that exist among the methods and those with the in situ measurements as well finally the methods have shown that in short term the height of destressed zone ranges from 6 5 to 24 times the extraction coal seam height while in long term the height of destressed zone ranges from 11 5 to 46 5 times the extraction coal seam height therefore beyond this height the overburden pressure will be transferred towards the front abutment the adjacent access tunnels the intervening barrier pillars as well as the panel rib sides

ground subsidence observations and a modified influence function method for complete subsidence prediction abstract the results of surface subsidence investigations carried out in different coal fields in india are presented in this paper important differences are seen to exist between the subsidence norms given in the subsidence engineers handbook uk and those obtained in indian conditions differences also exist for extraction below unfractured or uncaved rock and below pre existing caved goaf s the subsidence is higher in the latter case and also in the slopes and strains consequently separate equations and guidelines have been given for these two conditions of mining since indian coal mining is mostly under shallow to moderate cover several cases of discontinuous subsidence have been observed a demarcation limit for discontinuous subsidence is given seeing that discontinuous subsidence causes severe surface damage since room and pillar mining is the principal underground method of extraction panels of irregular shapes often occur making complete subsidence prediction difficult the influence function method with a new function and additional functions for modelling subsidence asymmetry and the effect of extraction edges are given in this paper the method for extraction below goaf s is also examined four cases are given for the comparison of observed and predicted subsidence contours and two cases for comparison of the slopes and strains

titanite petrochronology of the southern brasilia orogen basement effects of retrograde net transfer reactions on titanite trace element compositions abstract combining u pb geochronology and trace element characteristics of accessory minerals more reactive during metamorphism and deformation than zircon such as titanite catisio5 is a powerful tool for elucidating pressure temperature time p t t evolution of orogenic basement complexes this study reports in situ titanite u pb and trace element data from upper amphibolite facies metatexitic orthogneisses of the pouso alegre complex in the basement of the neoproterozoic southern brasilia orogen se brazil the titanite data is combined with thermodynamic modeling major phase compositions and u pb zircon dating and used to constrain the p t t path of the complex during the neoproterozoic orogenesis the investigated garnet amphibole gneisses record peak metamorphic conditions of 750 775 c and 10 5 12 5 kbar associated with partial melting and dated at ca 630 620 ma based on u pb analyses of hree y depleted titanite cores inferred to have crystallized in the presence of garnet near the peak p t conditions extensive melt crystallization at ca 616 ma is constrained by u pb dating of leucosome zircons the exhumation of the complex and re equilibration to ca 550 625 c at 6 9 kbar led to widespread generation of biotite epidote clinozoisite partially replacing amphibole garnet along the main foliation trace element signatures of these retrograde net transfer reactions are recorded in the titanite rims which are hree y enriched strontium depleted and were dated at 605 7 6 2 ma the average zirconium contents of the titanite rims are higher than cores suggesting disequilibrium partitioning of zirconium into titanite during the retrograde path resulting in overestimated zr in titanite temperatures for the rims the exhumation of the complex was concomitant with the intrusion of folded and recrystallized leucogranite dykes dated at 607 0 5 7 ma attesting the persistence of deformation after their intrusion assuming that the pouso alegre complex is part of the sao francisco paleocontinent reworked during the brasilia orogeny the data constrain the minimum age for the collision between the sao francisco paleocontinent and the paranapanema block at ca 620 630 ma and agree with the idea of long lived metamorphism and deformation in the southern brasilia orogen

localization of mining induced horizontal fractures along rock layer interfaces in overburden field measurements and prediction the locations of mining induced horizontal fractures along rock interfaces in the overburden of donetsk coal basin were identified using an original experimental device the device traps methane from horizontal fracture zone 100 fold coal seam thickness over an active longwall mining excavation presence or absence of horizontal fractures along rock layer interfaces is correlated with physical characteristics of the overburden such as thickness uniaxial compressive strength of overburden rock layers location of rock layer interfaces and thickness of extracted coal seams as a result a combined criterion based on these physical characteristics is proposed to predict the presence of overburden horizontal fracturing in coal mine operations

monitoring the strata behavior in the destressed zone of a shallow indian longwall panel with hard sandstone cover using mine microseismicity and borehole televiewer data abstract massive coal extraction from the longwall panel results in the formation large void space goaf which is followed by elevation in the stress level of the overlying strata the increasing stress leads to rock displacements in form of deformation fracturing and caving of the roof behind the powered supports for regaining the equilibrium state these rock displacements divided the longwall roof into three zones known as caved zone cz fractured zone fz and continuous deformation zone cd previous studies have shown that the overlying strata in the destressed zone behaves violently in presence of hard rock such as compact sandstone shale etc which is a major problem faced in the indian underground mines therefore the present study intends to monitor the roof behavior of a shallow longwall mine working depth 68 74m mining height 2 3m of central india which is overlain by a thick sandstone bed average thickness 37 48m using six months oct 01 mar 02 mine induced microseismicity containing event coordinates in 3d plane and event parameters such as magnitude energy and apparent stress along with borehole televiewer bhtv data the paper discusses the results of some important studies which are very essential for enhancing the safety in the mining area such as a the height of destressed zone was calculated through multiple approaches empirical relations mining height and bulking factor and found to be around eighteen times the mining height hc hf 18h b microseismicity study of the longwall roof showed that events corresponding to fractured zone had the lowest b value b 0 3301 and highest occurrence frequency a 2 3178 c borehole televiewer bhtv data showed the presence of massive fractures and water seepage level in fractured zone at depth of about 40 50m d the integrated approach of b value energy magnitude e m and gutenberg richter frequency magnitude relation showed that events corresponding fractured zone had the highest magnitude 1 2 and energy 106 6j and e the behavior of microseismic event properties such as event counts energy apparent stress and magnitude was also studied with respect to mine geology and abnormal changes were seen when the roof strata was encountered with hard rock mainly coarse grained sandstone with rqd 60 and fault ff the study successfully helped towards obtaining several useful results related to dynamic roof displacement and failures which very much enhanced the safety in the longwall mines

neoproterozoic high pressure metamorphism and tectonic constraint from the nappe system south of the sao francisco craton southeast brazil abstract the neoproterozoic giant nappe system exposed south of the sao francisco craton underwent a minimum of 150 km of near horizontal northeastward displacement this nappe system comprises an uppermost unit derived from a plutonic magmatic arc terrane with high pressure high temperature intermediate to mafic granulites at its base socorro guaxupe nappe underlain in sequence by a high pressure kyanite granulite nappe an amphibolite facies metapelite nappe and finally by a quartzite nappe which forms the lowest part of the pile and rests on a parautochthonous unit related to the passive margin of the craton the kyanite granulites crystallized ca 13 kbar 750 c and have only at their top sillimanite related to t increase overprinting t 890 c a consequence of downward heat advection from the overlying socorro guaxupe granulites equilibrated at 900 c pressures of 13 14 kbar are documented in the underlying metapelite nappe with temperatures of 640 670 c in which lenses of eclogite indicate p max of ca 17 5 kbar phyllites of the parautochthonous unit are directly overlain by hp granulites in the north and record p 7 kbar and t 500 c the distribution of metamorphic facies is reminiscent of inverted metamorphism with eclogites from subduction related metamorphism and kyanite granulites from early extrusion of subducted continental crust the metamorphic conditions of the parautochthon may represent a stage achieved during late metamorphic thinning of the nappe pile the overall picture suggests that high pressure units recrystallized in a subduction zone located to the wsw the frontal thrusts of the nappe system show a late north northeastward transported thin skinned pattern

reply to comment on trace fossil evidence for ediacaran bilaterian animals with complex behaviors precambrian res 224 2013 690 701 state key laboratory of paleobiology and stratigraphy nanjing institute of geology and paleontology chinese academy of sciences nanjing 210008 china department of geosciences virginia polytechnic institute and state university blacksburg va 24061 usa hunan institute of geological survey changsha hunan 410116 china department of geological sciences university of missouri columbia mo 65211 usa

transient flow of water to a well in an unconfined aquifer applicability of some conceptual models currently available methods for interpreting data from unconfined aquifers are based on analytical solutions which restrict attention to flow in the saturated zone and account for drainage of water from the unsaturated zone through a source term the parameter specific yield sy is assumed to dictate the total quantity of water that is derivable through the desaturation process it is commonly assumed that flow in the unsaturated zone has little effect on flow in the saturated zone and therefore that all the drainable water is instantly delivered at the water table as it declines in response to pumping in a model proposed in 1954 boulton empirically assumed that the drainable water associated with sy is released gradually at the water table as an exponential function of time this concept of boulton is similar to the notion of first order kinetics frequently used to handle chemical transformations boulton s model is considered by some to have no physical basis numerical experiments performed on sand columns with reasonable properties suggest that vertical drainage of water at the water table due to a falling water table is a time dependent process which is mathematically more complex than a simple exponential relation although boulton did not provide a rational physical explanation his exponential assumption has some merit in that it implicitly provides for a time dependent drainage process which seems to occur in the unsaturated zone however the simple exponential approximation is not adequate to account for what is seemingly a complex process it appears that a physically comprehensive model of radial flow in an unconfined aquifer will combine time dependent drainage from above the water table with vertical components of flow in the saturated zone an additional assumption frequently made is that the well can be treated as a line source results from numerical experiments suggest that caution is in order before neglecting effects of well bore storage in interpreting data from tests on unconfined aquifers

temporal changes of hydraulic properties of overburden aquifer induced by longwall mining in ningtiaota coalfield northwest china abstract characterizing the mining induced temporal changes of hydraulic properties of the overburden aquifer is significant for groundwater resource protection conventional hydrogeological methods e g hydraulic test physical model test and numerical simulation of determining hydraulic properties of the overburden aquifer cannot quantitatively analyze the temporal changes of the hydraulic properties induced by mining disturbances this paper demonstrates a quantitative determination for the temporal changes of parameters compressibility porosity and specific storage in the overburden aquifer influenced by the mining processes based on in situ continuous measurements of groundwater level that was affected by earth tide atmospheric loading and mining disturbances the results showed that when working face reached a certain distance 127 m from borehole j6 in this study those parameters compressibility porosity and specific storage of overburden aquifer began to show gradual decrease with approximately up to two order of magnitudes after the working face passed by the observation borehole j6 those properties of overburden aquifer recovered in about 80 days which might reflect the characteristic of elastic deformation of the aquifer those findings of the mining induced parameters temporal changes could improve our understanding of the mining effects on aquifer system and could be meaningful in groundwater resource protection

an analysis of reservoir conditions and responses in longwall panel overburden during mining and its effect on gob gas well performance abstract niosh conducted a cooperative research study to provide direct measurements of changing reservoir conditions in longwall panel overburden the field measurements documented changes in permeabilities methane concentrations fluid pressures and the effects of adjacent gob gas ventholes ggvs on niosh boreholes drilled in the study panel three different stratigraphic horizons were monitored by the niosh boreholes results indicated that the gob gas venthole fracture network formed 24 to 46 m 80 to 150 ft ahead of the mining face overburden permeabilities within the same overburden test zones were 1 md prior to undermining increasing to hundreds or thousands of md during undermining permeabilities measured seven months after undermining showed additional increases the relationship between changing reservoir conditions longwall face position and surface movement is discussed recommendations are made to optimize ggv performance by evaluating changes in subsidence produced by mining resulting in rock stresses that substantially influence induced fracture permeability mechanisms to account for the observed changes in reservoir conditions are reported

comment on bilaterian burrows and grazing behavior at 585 million years ago pecoits et al reports 29 june 2012 p 1693 describe bilaterian trace fossils and assign them an ediacaran age based on the age of a granite interpreted as intrusive we argue that the granite is not intrusive but in fact represents the basement of the sedimentary succession moreover we show that identical trace fossils occur in nearby carboniferous permian glacigenic rocks

response to comment on bilaterian burrows and grazing behavior at 585 million years ago gaucher et al suggest that their field observations and petrographic analysis of one thin section do not support an ediacaran age for the trace fossils bearing strata of the tacuari formation we have strengthened our conclusion of an ediacaran age for the tacuari formation based on reassessment of new and previously presented field and petrographic evidence