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

simulation of water resource loss in short distance coal seams disturbed by repeated mining physical simulations and field measurements were performed to study the movement of overlying strata and water conductive fractures wcf under conditions of repeated mining in short distance coal seams in addition the feasibility of water resource conservation mining wrcm was analyzed in areas disturbed by repeated mining the results of the simulation showed that the aquiclude remained intact after the mining of coal seam 11 the 1st main seam in shigetai coal mine in northwest china according to the findings wrcm can be conducted in this area after the mining of coal seam 12 the 2nd main seam the wcf in overlying strata above the central section of the mined out area will gradually compress and close however due to the impact of repeated mining in short distance coal seams wcf in overlying strata at the edge of the mined out area are connected to the quaternary loose aquifer and are not likely to close resulting in the loss of the water resource thus wrcm in this area would be difficult to conduct moreover field observations showed that the aquifer can likely remain intact after coal seam 11 is mined but the aquifer s water level will probably not fully recover if coal seam 12 is mined this is consistent with the simulation results therefore appropriate technical mining measures must be taken to conduct wrcm at the 2nd main seam in the shallow buried short distance coal seams these research results can be used as a reference for future wrcm endeavors in the arid and semi arid regions of northwest china

reassessment of continental growth during the accretionary history of the central asian orogenic belt we argue that the production of mantle derived or juvenile continental crust during the accretionary history of the central asian orogenic belt caob has been grossly overestimated this is because previous assessments only considered the palaeozoic evolution of the belt whereas its accretionary history already began in the latest mesoproterozoic furthermore much of the juvenile growth in central asia occurred in late permian and mesozoic times after completion of caob evolution and perhaps related to major plume activity we demonstrate from zircon ages and nd hf isotopic systematics from selected terranes within the caob that many neoproterozoic to palaeozoic granitoids in the accreted terranes of the belt are derived from melting of heterogeneous precambrian crust or through mixing of old continental crust with juvenile or short lived material most likely in continental arc settings at the same time juvenile growth in the caob occurred during the latest neoproterozoic to palaeozoic in oceanic island arc settings and during accretion of oceanic island arc and precambrian terranes however taking together our data do not support unusually high crust production rates during evolution of the caob significant variations in zircon ehf values at a given magmatic age suggest that granitoid magmas were assembled from small batches of melt that seem to mirror the isotopic characteristics of compositionally and chronologically heterogeneous crustal sources we reiterate that the chemical characteristics of crustally derived granitoids are inherited from their source s and cannot be used to reconstruct tectonic settings and thus many tectonic models solely based on chemical data may need re evaluation crustal evolution in the caob involved both juvenile material and abundant reworking of older crust with varying proportions throughout its accretionary history and we see many similarities with the evolution of the sw pacific and the tasmanides of eastern australia

aquifer protection during longwall mining of shallow coal seams a case study in the shendong coalfield of china large scale underground mining of shallow coal seams can have significant impacts on ground surface and potentially leads to incidental damage to the overlying aquifer with subsequent environmental hazards in order to deal with the apparent conflict between water protection and high production in underground mining an aquifer protection mining technique was trialed in panel 51201 in the shangwan colliery the shendong coalfield china overburden failure water level of the unconsolidated aquifer surface cracks and ground subsidence were monitored in a series of boreholes using borescope and also by observations in a nearby water well and by surface surveys monitoring results indicate that the aquifer protection mining technique can be successfully applied by modifying a few mining parameters such as mining height or advance rate under some suitable geological conditions the critical zone in the stratigraphy appears to be the weathered bedrock located immediately below the aquifer the weathered bedrock will remain impermeable after mining as long as its thickness is greater than the mining height the development of the mining induced overburden failure is affected by the key strata but ultimately controlled by the soft aquiclude such as the weathered zone it was observed respectively that the height of the caved zone was observed to be 5 to 6 times the mining height whilst the height of the fractured zone is about 10 to 11 times the mining height

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

age and petrogenesis of the neoproterozoic chon ashu alkaline complex and a new discovery of chalcopyrite mineralization in the eastern kyrgyz tien shan abstract neoproterozoic volcanics and granitoids formed at rodinia margins within a time span of 880 ma 700 ma are well documented in many terranes of the southern central asian orogenic belt caob ages younger than 550 ma corresponding to the opening of the terskey ocean are also common however so far there were very few published ages in the range 700 ma 550 ma from the kyrgyz tien shan in this paper we present new data for the alkaline chon ashu complex emplaced at the end of the cryogenian period of the neoproterozoic 850 635 ma gradstein et al 2012 the alkaline complex intrudes the precambrian metamorphic rocks north of the nikolaev line which separates the northern and middle tien shan terranes in the eastern kyrgyzstan the undeformed shallow level alkaline rocks range from olivine gabbro to nepheline and cancrinite syenites and leucosyenites the differentiated rock assemblage can be explained by fractional crystallization of high silica mineral phases which drives nepheline normative melts away from the silica saturation boundary the alkaline rocks of chon ashu are enriched in lile and hfse indicative of their origin from lithospheric mantle an age of 678 9 ma u pb shrimp was obtained for a protolith of country gneiss and an age of 656 4 ma was obtained for the crosscutting alkaline rocks of the chon ashu complex seven zircon grains recovered from gneiss and alkaline rocks had bright overgrown rims which yielded a cumulative age of 400 8 ma a metamorphic event followed by uplift and emplacement of shallow level alkaline complex constrains the geodynamic setting alkaline rocks usually form in an extensional setting and originate from lithospheric mantle the 690 ma xenoliths of mafic granulite from the nw tarim have been interpreted to originate by mafic underplating this mafic underplating may have been responsible for metamorphism in the middle crust prior to emplacement of the chon ashu complex the 670 ma 630 ma period of extension and emplacement of enriched alkaline rocks can be also traced on a regional scale through southern kazakhstan and the northern tarim we tentatively interpret these events as a result of mafic underplating and subsequent rifting related to the break up of rodinia during field work at chon ashu rich chalcopyrite mineralization has been discovered in carbonate veinlets in leucosyenite alkaline dikes and has also been found in the adjacent cambrian gabbro and granites shown on the map as undivided devonian silurian stockwork mineralization predominates though disseminated mineralization is also present the cu content reaches 16 184 ppm and is associated with elevated concentrations of pb zn and ag the polyphase structural evolution of the area suggests that mineralization could have formed in several genetically unrelated stages based on structural and mineralogical evidence we tentatively relate the earliest stage of chalcopyrite mineralization to the late magmatic co2 rich fluids emanating from the cryogenian alkaline complex the early devonian thermal event registered by growth of new zircon at 400 ma has important metallogenic implications on a regional scale however the origin of two zones of alteration in the undivided silurian devonian granites is ambiguous because their age was not determined geochronologically the 522 4 ma cambrian gabbro of the tashtambektor formation is strongly foliated along the splays of the nikolaev line indicating a hercynian origin of the fabric superimposed mineralized stockwork postdates the foliation and suggests a late hercynian age of mineralization in gabbro the new data enable a reassessment of the metallogenic potential of the eastern kyrgyz tien shan presence of not eroded high level mineralized neoproterozoic alkaline intrusions points to a previously underestimated metallogenic potential of pre hercynian granitoids which may host preserved porphyry systems skarns and shear related mineralization finally the devonian magmato metamorphic event which caused formation of a number of ore deposits in central kyrgyzstan and kazakhstan could also create potential exploration targets in eastern kyrgyzstan

geochemical discrimination of metabasalt rocks of the fan karategin transitional blueschist greenschist belt south tianshan tajikistan seamount volcanism and accretionary tectonics the fan karategin metamorphic belt south tianshan tajikistan is regarded to be an ancient subduction accretionary complex and is composed of three tectonostratigraphic units which display lithologies consistent with different tectonic settings the mafic schists which make up the major part of the older unit of the belt contain both alkali and tholeiitic metabasalts on the basis of rare earth and other immobile element characteristics the alkali metabasalts are akin to within plate ocean island basalts whereas the tholeiitic metabasalts resemble e type morb the association is interpreted to have been formed on seamount like structures under a within plate plume bedded cherts and marbles in the unit are regarded as ancient pelagic sediments and carbonate caps developed upon basaltic seamounts respectively dismemberment of the seamount related basalts and pelagic sediments and the high p low t prograde metamorphism of the unit rocks up to transitional blueschist greenschist facies was the result of paleoseamount submergence into a subduction zone this unit is tectonically overlain by arc derived metavolcanic unit and a disrupted mainly clastic unit of upper ordovician lower silurian age metavolcanic and metasedimentary rocks of the two upper units have geochemical characteristics compatible with subduction related origin the lithological assemblages of the individual units and their juxtaposition suggest an origin involving collision accretionary processes the fan karategin belt is a subduction accretionary complex which formed during subduction of oceanic crust under a volcanic arc and was subjected to tectonic juxtaposition and imbrication of seamount deep sea trench and volcanic arc sequences

height of water conducting fractured zone in a coal seam overlain by thin bedrock and thick clay layer a case study from the sanyuan coal mine in north china the accurate determination of the height of the water conducting fractured zone hwcfz in a coal seam covered by thin bedrock and thick clay layer is crucial for aquifer protection mine safety and eco environmental conservation using the sanyuan coal mine in north china as a case study theoretical analysis numerical simulation and field measurements were used to analyze the regularity of the hwcfz in this area per mechanical theory a geometrical model for calculating rock bending and subsidence was established two arcs of equal curvature and lengths and opposite curvature direction were used to fit the curve section of intermediate rock layer after bending the theoretical method for solving the hwcfz was given by calculating the rock layer s tensile ratio in addition rock failure process analysis rfpa software was used to simulate the development of the water conducting fractured zone wcfz during the mining process and the hwcfz was measured by the drilling fluid loss measurement both which verified the feasibility of the theoretical calculation to determine the primary controlling factors affecting the hwcfz the seepage characteristics and plastic properties of the quaternary clay layer were also analyzed using laboratory tests results show that the quaternary clay with a depth greater than 130 m has a permeability coefficient of e 10 m s a liquidity index less than 0 25 and a plasticity index more than 17 indicating the clay layer is impermeable and of great importance to inhibiting the development of wcfz the research can provide significant theoretical insights for effectively preventing water hazards on mine roofs

characteristics of stratum movement induced by downward longwall mining activities in middle distance multi seam abstract with the development of mining depth multi seam mining activities is becoming more and more frequent correspondingly the study on stratum movement characteristics induced by multi seam mining activities is of great significance for preventing water inrush disaster and forecasting support pressure surface deformation gas drainage and other mining problems according to the interaction among the caved zone the fractured zone and the continuous deformed zone caused by the multi seam downward mining activities multi seam can be divided into three types i e the short distance middle distance and long distance multi seam this paper carries out a case study on the middle distance multi seam mining activities in a coal mine in china to investigate the characteristics of stratum movement caused by downward longwall coal mining activities in the multi seam by means of borehole water level observation digital borehole camera test microseismic monitoring surface crack observation of the surface cracks and distinct element modelling by analyzing the in site monitoring results and the numerical simulation results it can be found that the failure of the key stratum between the lower and upper seams resulting in the connection between the failed zone in floor induced by the upper seam and the fractured zone induced by the lower seam after the failure of the key stratum the mining activities of the lower seam has a great influence on the secondary stratum movement in the overburden these effects are mainly reflected in the rapid increase of horizontal displacement and vertical displacement which caused the caved and fractured zones extend upward in the overburden and then surface cracks increase significantly the above research results are of great significance for the prevention and control of disasters induced by downward longwall mining activities in middle distance multi seam

upward slicing longwall roadway cemented backfilling technology for mining an extra thick coal seam located under aquifers a case study many water inrush disasters have occurred in mines that were attempting to recover extra thick coal seams located under aquifers this paper presents a technology known as upward slicing longwall roadway cemented backfilling uslcb which can provide a safe and effective solution to extract these seams the fundamentals of the technology are to divide a coal seam into several slices and extract each slice sequentially from bottom to top using longwall roadway mining technology gobs are filled with cemented backfill which then act as a new floor allowing the overlying slices to be mined similar to the overhand cut and fill method this paper also presents the compressive properties of cemented backfill material with various mixing ratios and curing times moreover a physical simulation was conducted to verify the effects of uslcb the results of the simulation indicate that uslcb can be used to control strata movement as well as the height of the water conducting zone hwcz the uslcb was applied at gonggeyingzi coal mine in inner mongolia china the results indicate that the recovery ratio has increased from 39 2 to 95 the backfill ratio reached 95 water inflow decreased from 245 to 120 m3 h and the maximum hwcz was 39 2 m after extracting the entire 21 m of the coal seam the conclusions of this research show that implementing uslcb can significantly improve productivity and safety when extra thick coal seams are mined which are located under aquifers

geochemical and geochronological studies of granitoid rocks from the western tianshan orogen implications for continental growth in the southwestern central asian orogenic belt abstract the western tianshan orogen in northwestern china is part of the southwestern margin of the central asian orogenic belt caob which represents the largest tectonic assembly of accretionary complexes and the most significant area of phanerozoic continental growth in the world granitoid rocks have a widespread occurrence and occupy about 30 of the whole exposure of the orogen ages obtained for the granitoids vary from 896 ma to 247 ma while initial 87 sr 86 sr ratios vary from 0 70329 to 0 72070 and e nd values from 14 1 to 7 3 the occurrence of neoproterozoic granitic gneisses implies the presence of precambrian basement in this area during oceanic subduction continental growth occurred as a result of several combined processes i e by addition of oceanic crustal melts adakites the intrusion of basaltic magmas derived by partial melting of the metasomatized depleted mantle wedge and the upwelling of granitic magma derived from a mixed source of basaltic magmas and old continental basement however during the post collisional period vertical accretion of underplated juvenile mantle material may have been accomplished during slab breakoff delamination this study suggests a two stage model of continental growth of syn subduction lateral accretion of arc complexes and post collisional vertical accretion of underplated mantle material which may also be relevant for the western segment of the caob in the phanerozoic the reworking and involvement of old crust are more obvious in the western tianshan orogen compared to other parts of the caob comprising the western junggar eastern junggar alataw and altay terranes

heat and mass transport in sublacustrine vents in yellowstone lake wyoming in situ chemical and temperature data documenting a dynamic hydrothermal system abstract recent advances in the development of in situ chemical and temperature sensors have shown great promise as a means to investigate time series changes in marine and terrestrial hydrothermal systems here we apply this technology to assess chemical and physical controls on sublacustrine vent fluids in yellowstone lake wy autonomous sensor systems were deployed in august 2017 using rov assets to position instruments at two sites in the deep hole region of the lake off shore from stevenson island earlier studies have documented that fissure related depressions 120 m water depth in this region host numerous vents issuing high enthalpy co2 saturated and h2s bearing vapor at temperatures in excess of 150 c the ysz ceramic based in situ chemical sensors deployed here were designed to measure ph and redox at 60 s intervals for up to one year two titanium sheathed thermocouples one coupled directly to the electrochemical sensor and another independently powered and positioned slightly deeper in vents at deployment sites provided insight on maximum temperature in the near surface region in addition to in situ chemical and temperature data vent fluid samples were acquired at the outset and during recovery with a novel isobaric system that maintains lake bottom pressure precluding fluid sample de gassing at the same time push cores of vents and in the near vent region were also acquired the mineralized cores provide evidence of long term mass transfer processes while also facilitating insertion and stabilization of the sensor units on the lake floor recovery of the sensors documented similar chemical controls at both sites suggesting compositionally invariant vapor influx characterized by moderately low ph 4 5 and reducing conditions buffered by co2 and h2s respectively accordingly the diatomaceous sediment was extensively altered to kaolinite and pyrite temperature variability at the two sites was especially significant one site site b situated on the slope of what might be a hydrothermal domal structure demonstrated noteworthy cooling and heating episodes that may be associated with hydrothermally or seismically triggered sediment slumping events upon instrument recovery in 2018 the vent site was largely sediment covered and the sensor insert showed evidence of dis location and melting by conductive heating under the hot sediment overburden the initially active and high temperature vent fluid 148 c had largely ceased and replaced by diffuse flow venting at the margin of the previous up flow zone the time series in situ chemical and physical data obtained in the course of the study document the existence of a dynamic hydrothermal system in time and space while underscoring the challenges of research of this type in such environments

numerical analysis of the dynamic evolution of mining induced stresses and fractures in multilayered rock strata using continuum based discrete element methods abstract in this study the continuum based discrete element method cdem was adopted to simulate the evolution of mining induced stress and fracturing during roadway tunnelling and mining in multilayered heterogeneous rock strata the cdem integrates the finite element method fem and the discrete element method dem to characterize the mining induced stress evolution the discontinuous fractures separations and caving that occur in the interfaces between multilayered rock strata the maximum tensile stress criterion and the mohr coulomb strength criterion were used to evaluate the tensile and shear failure of the material elements the cdem model for rock strata was constructed by employing image processing and reconstruction approaches using the geometrical and physical parameters that were measured from a real coal mining site the stress evolution and compression deformation of the roof and floor strata were computed to evaluate the criticality of mining induced disasters the constructed model was employed to simulate and analyse the immediate roof collapse immediate floor bulges and the compaction of the collapse blocks as well as the large deformation separation and collapse between the immediate roof and the main roof during coal seam mining it was shown that the proposed method could predict ranges for the caving zone and fracture zone in the rock roofs that were in good agreement with the observation results from the real coal mining site

three dimensional mineral grade distribution modelling and longwall mining of an underground bauxite seam abstract a multi step interpolation approach was proposed to model the three dimensional grade distribution and to demarcate orebody in a thin and anfractuous bauxite seam a pre mining demonstration procedure was established to virtually perform fully mechanized longwall mining in the modelled bauxite seam meanwhile a comprehensive evaluation function expressed by the sum of dilution and loss rates of bauxite was utilized to determine the optimal cutting heights 1 71 2 69 m and a suitable diameter 1 5 m for the cutting drums mounted on a double drum shearer to achieve no waste and high recovery mining of the demarcated 106 026 m3 bauxite orebody in addition a numerical model of strata containing geological defects a karst cave and fault discontinuities joints and stratifications and a mountain was established to simulate the discontinuous motion and overburden fracturing disturbed by the longwall mining in the modelled bauxite seam the results indicated that the overburden presented reliable stability and impermeability in which no large scale caving in goaf no water influx no cave collapse no fault slip and no mountain slope landslide occurred this was due to arched roofs above the karst cave and the mining induced fractured zone the subcritical condition of the longwall panel in the dip section and support from the protective pillar between two adjacent panels

preliminary study on the feasibility of co exploitation of coal and uranium abstract both coal and uranium resources are found in the dongsheng area which is located in the northern part of ordos basin china with the coal seam below the uranium deposit in this paper we attempt to study the feasibility of co exploitation of the coal seam and the uranium deposit the permeability evolution in strata around the coal seam are selected as the key parameter indexing the separate and safe concurrent recovery of two deposits and a novel strain dependent permeability model is proposed covering the full deformation range of rock the proposed model is first verified with experimental data with good fitting of the results then an upscaled numerical model is established considering the geology conditions of dongsheng area this is implemented using comsol multiphysics and the interface of comsol with matlab is used to study the damage to the rock mass we show that a compared with the stress dependent permeability model the strain dependent permeability model proposed in this work has the advantage that each strain value is associated with a unique permeability value b the feasibility of co exploitation of the coal seam and the uranium deposit depends on the relative distance between two resources when the caved and fractured zone encroaches on the uranium deposit the coal seam should be abandoned conversely when the uranium deposit lays in the constrained zone the recovery of the coal seam would benefit recovery of the uranium deposit c the feasibility of the co recovery of the two resources can be optimized by the choice of mining approach the top caving mining approach and room and pillar mining approach can reduce the height of the caved and fractured zones and make the co exploitation of the uranium and coal feasible this work provides a new approach to investigate the feasibility of co exploitation of uranium and coal

field and numerical investigations of gateroad system failure induced by hard roofs in a longwall top coal caving face abstract in longwall mining hard roofs located immediately above the coal seam should not cave and cause ground control problems around the working longwall face in this paper comprehensive field observations and numerical simulations were used to investigate the chain pillar and adjoining gateroad failure during a longwall top coal caving ltcc face retreat at the majialiang coalmine located in shanxi china the results show that hard roof strata did not cave behind the longwall face but overhung to form a cantilever beam above the chain pillar the roof beam concentrated high stress in the chain pillar and caused the pillar failure the concentrated stress moved close to the headgate and the solid side of the next panel causing gateroad damage and rib collapse numerical simulations found that hard roof treatment could fill the space near the goaf edge and deliver support pressure to the roof as well as alleviate the stress concentration in the pillar and the solid side of the next longwall panel simulations suggested that a pillar size of 50 m or larger was feasible without consideration of hard roof treatment a 40 m chain pillar with hard roof treatment could also satisfy the demand on the pillar and supply gateroad safety during the service period field practices verified the numerical results and suggested that hard roof treatment by hydraulic fracturing is a feasible method for overcoming ground control problems in a situation such as that presented in this paper

hydrothermal and tectonic activity in northern yellowstone lake wyoming yellowstone national park is the site of one of the world9s largest calderas the abundance of geothermal and tectonic activity in and around the caldera including historic uplift and subsidence makes it necessary to understand active geologic processes and their associated hazards to that end we here use an extensive grid of high resolution seismic reflection profiles 450 km to document hydrothermal and tectonic features and deposits in northern yellowstone lake sublacustrine geothermal features in northern yellowstone lake include two of the largest known hydrothermal explosion craters mary bay and elliott9s mary bay explosion breccia is distributed uniformly around the crater whereas elliott9s crater breccia has an asymmetric distribution and forms a distinctive 2 km long hummocky lobe on the lake floor hydrothermal vents and low relief domes are abundant on the lake floor their greatest abundance is in and near explosion craters and along linear fissures domed areas on the lake floor that are relatively unbreached by vents are considered the most likely sites of future large hydrothermal explosions four submerged shoreline terraces along the margins of northern yellowstone lake add to the holocene record of postglacial lake level fluctuations attributed to heavy breathing of the yellowstone magma reservoir and associated geothermal system the lake hotel fault cuts through northwestern yellowstone lake and represents part of a 25 km long distributed extensional deformation zone three postglacial ruptures indicate a slip rate of 0 27 to 0 34 mm yr the largest 3 0 m slip and most recent event occurred in the past 2100 yr although high heat flow in the crust limits the rupture area of this fault zone future earthquakes of magnitude 5 3 to 6 5 are possible earthquakes and hydrothermal explosions have probably triggered landslides common features around the lake margins few high resolution seismic reflection surveys have been conducted in lakes in active volcanic areas our data reveal active geothermal features with unprecedented resolution and provide important analogues for recognition of comparable features and potential hazards in other subaqueous geothermal environments

tectonic evolution of the south tianshan orogen and adjacent regions nw china geochemical and age constraints of granitoid rocks geochemical and geochronological evidence was obtained from granitoids of the south tianshan orogen and adjacent regions which consist of three individual tectonic domains the kazakhstan yili plate the central tianshan terrane and the tarim plate from north to south the central tianshan terrane is structurally bounded by the early paleozoic nikolaev line north nalati fault and late paleozoic atbashy inyl chek south nalati qawabulak fault zones against the kazakhstan yili and tarim plates respectively the meta aluminous to weakly peraluminous granitic rocks which are exposed along the kekesu river and the bikai river across the central tianshan terrane have a tholeiitic calc alkaline or high potassium calc alkaline composition i type geochemical trace element characteristics and the y versus rb nb or y versus nb discrimination diagrams favor a continental arc setting for these granitoid rocks shrimp u pb and la icp ms u pb zircon age data indicate that the magmatism started at about 480 ma continued from 460 to 330 ma and ended at about 275 ma the earlier magmatism 470 ma is considered to be the result of a simultaneous southward and northward subduction of the terskey ocean beneath the northern margin of the tarim plate and the kazakhstan yili plate respectively the later magmatism 460 330 ma is related to the northward subduction of the south tianshan ocean beneath the southern margin of the kazakhstan yili central tianshan plate the dataset presented here in conjunction with previously published data support a late paleozoic tectonic evolution of the south tianshan orogen not a triassic one as recently suggested by shrimp u pb zircon dating for eclogites

early paleozoic magmatic record from the northern margin of the tarim craton further insights on the evolution of the central asian orogenic belt abstract the southern tianshan orogenic belt stob is an important region to understand the prolonged evolution of the central asian orogenic belt caob a comprehensive study of zircon u pb ages and lu hf isotopes whole rock elements and sr nd isotopes was carried out for two intermediate mafic intrusions in the baicheng and heiyingshan areas of southwest tianshan la icp ms zircon u pb dating yielded crystallization ages of 431 3 ma mswd 0 073 n 31 and 430 3 ma mswd 0 104 n 30 for the baicheng diorites and 423 9 2 1 ma mswd 0 5 n 12 for the heiyingshan gabbros these data in combination with other late silurian ages previously reported for the intrusive suites from the stob indicate an early paleozoic magmatic event in the region in situ zircon hf isotope data on two samples from the baicheng diorites show ehf t values of 2 4 to 4 9 and 0 2 to 6 and the heiyingshan gabbros exhibit similar ehf t values from 1 to 1 8 the dioritic pluton exhibits na rich arc type geochemical and calc alkaline affinity and shows trace element patterns characterized by enrichment in large ion lithophile elements rb ba k and sr and depletion in high strength field elements nb ta ti zr and hf these features resemble those of arc type igneous rocks combined with initial 87sr 86sr ratios of 0 7047 to 0 7064 and end t of 1 6 to 5 06 we infer that the magma from which the baicheng dioritic pluton formed was sourced from a mantle wedge which was subjected to metasomatism by fluids and melts related to subducted oceanic slab and the overlying sediments the heiyingshan gabbro shows a na rich nature and tholeiitic affinity they not only display supra subduction zone affinity but also are geochemically similar to e morb possible implying a back arc basin setting the initial 87sr 86sr ratios of the heiyingshan samples range from 0 7046 to 0 7051 and end t values vary from 1 76 to 5 19 we speculate that the upwelling of the asthenospheric mantle to the supra subduction wedge facilitated by subduction roll back provided the source for the heiyingshan gabbroic rocks together with other geologic evidence we correlate the generation of the baicheng diorite with the southward subduction of the south tianshan ocean during the early paleozoic the heiyingshan gabbroic plutons were probably formed in a back arc basin in response to the southward subduction of the paleo tianshan ocean in combination with coeval arc type magmatic rocks widely exposed in the southern margin of the central tianshan block a double sided subduction model is proposed to explain the evolution of the south tianshan ocean in the silurian

hercynian post collisional magmatism in the context of paleozoic magmatic evolution of the tien shan orogenic belt abstract the hercynian tien shan tianshan orogen formed during late palaeozoic collision between the karakum tarim and the kazakhstan paleo continents in order to constrain timing of hercynian post collisional magmatism 27 intrusions were sampled for u pb zircon dating along a ca 2000 km long profile in uzbekistan and kyrgyzstan the samples were dated utilizing sensitive high resolution ion microprobe shrimp ii the obtained ages together with previously published age data allowed the timing of hercynian post collisional magmatism to be constrained and interpreted in the context of the paleozoic magmatic evolution of the region apart from hercynian post collisional magmatism two older magmatic episodes have been recognized and the following sequence of events has been established 1 approximately 10 ma after cessation of continuous caledonian magmatism a number of late silurian early devonian intrusions were emplaced in the middle and northern tien shan terranes between 420 and 390 ma the intrusions probably formed in an extensional back arc setting during coeval subduction under the margins of caledonian paleo kazakhstan continent 2 the next relatively short late carboniferous episode of subduction under paleo kazakhstan was registered in the kurama range of the middle tien shan calc alkaline volcanics and granitoids with ages 315 300 ma have distinct metallogenic affinities typical for subduction related rocks and are not found anywhere outside the middle tien shan terrane west of the talas farghona fault 3 the early permian hercynian post collisional magmatism culminated after the closure of the paleo turkestan ocean and affected the whole region across terrane boundaries the post collisional intrusions formed within a relatively short time span between 295 and 280 ma the model for hercynian post collisional evolution suggests that after collision the tien shan was affected by trans crustal strike slip motions which provided suitable conduits for ascending asthenospheric material and heat influx in the crust this produced both granitoid magmas and hydrothermal fluid flow as a result post collisional intrusions and orogenic au deposits known in the region formed coevally and were tectonically controlled 4 between 240 and 220 ma a triassic thermal event affected the region resulting in resetting and growth of new zircon grains which is detected on a regional scale probably the influx of heat into the crust during the triassic was tectonically focused and varied significantly in different terranes in the region under investigation the triassic thermal event was not accompanied by any significant magmatic activity thus after cessation of hercynian post collisional magmatism ca 280 ma ago there was a long magmatically quiet period in the tien shan

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

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

soil and water conservation in mining area based on ground surface subsidence control development of a high water swelling material and its application in backfilling mining it has always been a crucial issue in the mining industry that the surface subsidence induced by underground coal mining can lead to the severe deterioration or loss of soil and water resources in mining area backfilling has become one of the most frequently used mining method to solve this puzzle as it can effectively control the movement of overlying strata and therefore soil and water resources will not be destroyed by mining activities a new type of high water swelling material hwsm was developed to address the key issues of current backfilling materials used in collieries such as the high cost inadequate strength and low expansion rate based on the principle that the strength of backfilling body satisfies the requirement a critical ratio of water to solid material a mixture of fly ash which was used as an aggregate lime anhydrite cement and additive ingredients was determined which varied from 0 8 1 to 0 9 1 meanwhile the mass ratio of fly ash anhydrite lime cement and additives was determined to be 24 6 0 8 5 1 1 8 1 laboratory tests showed that strength of samples that met the required setting time for practical use could reach 5 39 5 52 mpa after 63 days the expansion rate after 3 h varied between 9 9 and 10 8 and the bleeding rate ranged from 0 3 to 0 33 industrial application has been conducted in wangtaipu colliery and results showed that the proposed hwsm had an outstanding mechanical performance with good expansion rates and fluidity these properties indicate that the developed material is suitable for use as a good backfilling material in mining so as to effectively reduce the ground surface subsidence and to conserve the soil and water

finite element modeling of stress distributions and problems for multi slice longwall mining in bangladesh with special reference to the barapukuria coal mine abstract this paper deals with current coal mining operations under a mega aquifer in nw bangladesh and presents a case study of underground mining in barapukuria the study uses numerical analyses to evaluate stress redistribution strata failure and water inflow enhancements that result from these coal extraction operations a total of three models a b and c are presented in this study two dimensional numerical modeling was performed to analyze the deformation and failure behavior of rock elements for two different models a and b for model a we used an elastic finite element software package considering a mohr coulomb failure criterion for model b we used boundary element method bem the first two models were applied to determine the stress patterns model a provides the tectonic stress pattern of the basin whereas model b represents the mining induced stress field the third model is a schematic model the results of model a show that tensional failure of rock elements is concentrated in the gondwana coal sequences as well as within the eastern boundary fault ebf and its surroundings failure occurs in the middle to lower part of the model and the magnitude of tensional stress in the shallow part is much greater than in the deeper part contours of max magnitudes are attributed to up bending of the overburden which would create numerous upward propagating fissures fractures the results of model b show that fracture propagation would be about 240 m upward for single slice height 3 m mining extraction from the contours of mean stress magnitudes it is observed that the high range of fracture propagation increased upward for multi slice extraction of coal it is apparent from the fracture heights that large amounts of caving would occur towards the roof due to the multi slice extraction of coal and finally would be linked with the water bearing dupi tila formation if this happened it would ultimately cause a major water inflow hazard in the mine

investigation of longwall goaf gas flows and borehole drainage performance by cfd simulation abstract to reduce methane emissions into the workings of a longwall panel the mechanisms of gas emissions and migration within the longwall goaf must first be understood additionally high performance drainage boreholes must be designed many variables affect the goaf gas flow and borehole drainage efficiency namely the gas release characteristics of gas sources the heights of caved and fractured zones of the goaf the location of the drainage borehole and the position of the effective drainage section the portion of the perforated case and the uncased open hole this paper illustrates how these variables influence the goaf gas flow patterns and borehole performances through cfd simulations a permeability model and a gas release curve which reflect observations from experiments geomechanical modellings mine site monitoring and borehole drainage data were constructed for the mining disturbed strata and incorporated into the cfd model the cfd model was calibrated with the actual drainage data from the surface boreholes at a coal mine simulation results show that the gas drainage velocities around the perimeter of the panel goaf are higher than in the central goaf which is consistent with the overlying annular fracture zone model established from csiro previous research boreholes located within the annular area drew methane at a higher flow rate than those located in the central area leading to a significant reduction of methane emissions to the ventilation system goaf geometry with higher caved and fractured zones has lower pressure and methane concentration but higher gas flow velocity the location of the effective drainage section of the borehole has significant influence on drainage performance boreholes with the bottom end located in the lower region of the fractured zone 20 m above the roof can draw more methane than those located in the upper region of the fractured zone 70 m above the roof and those located in the caved zone 2 m above the roof

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

generation and evolution of hydrothermal fluids at yellowstone insights from the heart lake geyser basin 1 we sampled fumaroles and hot springs from the heart lake geyser basin hlgb measured water and gas discharge and estimated heat and mass flux from this geothermal area in 2009 the combined data set reveals that diverse fluids share an origin by mixing of deep solute rich parent water with dilute heated meteoric water accompanied by subsequent boiling a variety of chemical and isotopic geothermometers are consistent with a parent water that equilibrates with rocks at 205 c 10 c and then undergoes 21 2 adiabatic boiling measured diffuse co2 flux and fumarole compositions are consistent with an initial dissolved co2 concentration of 21 7 mmol upon arrival at the caldera boundary and prior to southeast flow boiling and discharge along the witch creek drainage the calculated advective flow from the basin is 78 16 l s 1of parent thermal water corresponding to 68 14 mw or 1 of the estimated thermal flux from yellowstone helium and carbon isotopes reveal minor addition of locally derived crustal biogenic and meteoric gases as this fluid boils and degasses reducing the he isotope ratio rc ra from 2 91 to 1 09 the hlgb is one of the few thermal areas at yellowstone that approaches a closed system where a series of progressively boiled waters can be sampled along with related steam and noncondensable gas at other yellowstone locations steam and gas are found without associated neutral cl waters e g hot spring basin or cl rich waters emerge without significant associated steam and gas upper geyser basin

geodynamics of the yellowstone hotspot and mantle plume seismic and gps imaging kinematics and mantle flow abstract integration of geophysical and geological data show that the yellowstone hotspot resulted from a mantle plume interacting with the overriding north america plate a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16 17 ma 700 km long yellowstone snake river plain ysrp silicic volcanic system accessibility of the ysrp allowed large scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements seismic tomography reveals a crustal magma reservoir of 8 to 15 melt 6 km to 16 km deep beneath the yellowstone caldera an upper mantle low p wave velocity body extends vertically from 80 km to 250 km beneath yellowstone but the anomalous body tilts 60 wnw and extends to 660 km depth into the mantle transition zone we interpret this conduit shaped low velocity body as a plume of up to 3 5 vp and 5 5 vs perturbation that corresponds to a 1 2 partial melt models of whole mantle convection reveal eastward upper mantle flow beneath yellowstone at relatively high rates of 5 cm yr that deflects the ascending plume into its west tilted geometry a geodynamic model of the yellowstone plume constrained by vp and vs velocities and attenuation parameters suggests low excess temperatures of up to 120 k corresponding to a maximum 2 5 melt and a small buoyancy flux of 0 25 mg s i e properties of a cool weak plume the buoyancy flux is many times smaller than for oceanic plumes nonetheless plume buoyancy has produced a 400 km wide 500 m high topographic swell centered on the yellowstone plateau contemporary deformation derived from gps measurements reveals sw extension of 2 3 mm yr across the yellowstone plateau one fourth of the total basin range opening rate which we consider to be part of basin range intraplate extension locally decadal episodes of subsidence and uplift averaging 2 cm yr characterize the 80 year yellowstone caldera monitored history and are modeled as hydrothermal magmatic sources moreover a recent episode 2004 2009 of accelerated uplift of the yellowstone caldera at rates up to 7 cm yr has been modeled as resulting from magmatic recharge of a 10 km deep sill at the top of the crustal magma reservoir regionally gravitational potential energy of the yellowstone swell drives the lithosphere southwest and downhill from the yellowstone plateau 400 km where it coalesces with basin range province wide westward extension based on the geometry and its assumed 660 km depth we extrapolate the plume source southwest to its original location at 17 ma and 600 km southwest and 200 km north of the ysrp importantly this location is beneath the southern part of the columbia plateau flood basalt field of the same age and implies that the yellowstone mantle plume may be the common source for both of these large volcanic fields our time progression model suggests that the original plume head rose vertically behind the juan de fuca plate but at 12 ma it lost the protection of the subducting plate from eastward mantle flow and encountered cooler thicker continental lithosphere becoming entrained in eastward upper mantle flow these results reveal that yellowstone plume plate processes have had a profound effect on late cenozoic geologic evolution and topography of a large part of the western u s

separation and fracturing in overlying strata disturbed by longwall mining in a mineral deposit seam abstract mining induced fractures influence the stability of overburden and may provide pathways for transferring heat and mass in underground environment a novel approach was proposed to quantify the separation and fracture evolution in the undermined overburden consisting of 1 theoretical distribution models of the void ratios of fractures vrfs based on analytical evaluation of key strata subsidence and 2 numerical modeling using the universal distinct element code and a sequence of image post processing procedures for a longwall mining panel both theoretical calculations and numerical simulations indicated that vrf first increased rapidly then gradually decreased and finally stabilized to a minimum from the surrounding edges of disturbed strata to their centers and gradually decreased from deep to shallow strata the fractures exhibited a fracture rich arch distribution type along a vertical section numerous fractures occurred around the arch feet near the perimeters of mined out area and or arch crown near the center of disturbed strata the distributions of vrfs show the heights shapes and damage intensities of fractured zones and can also be used as porosity parameters to determine the permeabilities of mining disturbed overburdens therefore the vrf models can be used as a quantitative parameter to assess the extent of possible risk zones e g for water inflow into the mine or escape of hazardous fluids to the surface

influence of physical characteristics of weak rock mass on height of caved zone over abandoned subsurface coal mines this is a study of the height of caved zones over abandoned subsurface coal mines in donetsk ukraine the heights of the caved zones in porous weak rock mass over shallow abandoned underground workings up to 80 m were detected by drilling and linked with laboratory measurements of the physical characteristics of the rock mass overlying the underground openings an empirical model is developed to determine the height of a caved zone in weak porous rock mass over shallow underground workings the model shows that the decrease in uniaxial compressive strength of the immediate roof and the increase in average porosity of rock layers over the immediate roof lead to an increase in the ratio between the height of caved zones and the height of underground coal workings it is suggested that the bulking of the weak immediate roof is insufficient to arrest caving over underground workings and therefore the significance of the rock mass overlying the immediate roof in formation of caved zones is increased it is argued that the caving height in weak porous rocks may reach 4 1 11 25 times the height of underground coal extraction

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

paleozoic accretionary orogenesis in the paleo asian ocean insights from detrital zircons from silurian to carboniferous strata at the northwestern margin of the tarim craton a detrital zircon u pb and lu hf isotopic study was carried out in the middle silurian to late carboniferous sedimentary strata of the northwestern tarim craton in order to understand accretionary processes in the southern part of the central asian orogenic belt detrital zircons from these strata yielded u pb ages clustering around 2 8 2 3 ga 2 0 1 7 ga 1 3 0 9 ga 880 600 ma and 500 400 ma with age populations and hf isotopic signatures matching those of magmatic rocks in the tarim craton and the central tianshan block abundant 500 400 ma detrital zircons most likely reflect deposition in a retroarc foreland basin inboard of an andean type magmatic arc to the north supporting the northern tarim central tianshan connection during early paleozoic time the absence of 380 310 ma zircon population in the carboniferous siliciclastic rocks suggests that the central tianshan block may have been separated from the tarim craton in the early devonian caused by the interarc back arc opening of the south tianshan ocean we propose an accretionary orogenic model switching from advancing to retreating mode during paleozoic time in the southwestern part of the paleo asian ocean this transition most likely occurred coevally with the rifting of southeast asian blocks from the northeastern margin of gondwana

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

ediacaran early ordovician and early silurian arcs in the south tianshan orogen of kyrgyzstan abstract the oldest magmatic rocks from the south tianshan orogen of kyrgyzstan sts are important for better understanding of the neoproterozoic and early palaeozoic evolution of the southwestern central asian orogenic belt bulk rock major and trace element and sm nd isotopic composition and zircon u pb ages of granitoids from melange blocks reveal two previously unknown episodes of arc magmatism in the sts orogen of kyrgyzstan namely the ediacaran ca 624 ma and early ordovician ca 472 ma episodes moderately positive nd t value of 5 8 of the ediacaran granodiorite indicates a mainly juvenile source for this rock negative nd t value of 9 1 for the early ordovician granodiorite indicates melting of the predominantly precambrian crustal material the latter is also supported by the inherited zircon cores with an age range of 1 04 2 7 ga the geochemical signature of the silurian late llandovery and wenlock basalts suggests formation in arc settings arc related origin of the ediacaran granodiorite suggests that mature oceanic basin with subduction system existed in the western sts since the late neoproterozoic the arc also evolved in the ordovician and silurian and was inactive in the middle cambrian to the earliest ordovician ediacaran granodiorite old zircon cores and negative nd t values of the ordovician granodiorite suggest the existence of precambrian microcontinents in the kyrgyz sts these crustal fragments were likely rifted off the tarim and or karakum tajik microcontinents where the rocks with similar ages occur in the palaeozoic they traveled north and were incorporated in the sts orogen in the late carboniferous

geochemical heterogeneity of sublacustrine hydrothermal vents in yellowstone lake wyoming abstract rov based submersible operations in yellowstone lake yellowstone national park wyoming usa have identified two locations with chemically and mineralogically distinct sublacustrine hydrothermal fluids and deposits the deep hole east of stevenson island si deep hole and the se west thumb deep vent field se wt field the si deep hole is the deepest part of yellowstone lake 120 m and hosts up to 174 c fluids heated by steam that condenses on contact with cold lake water the resulting hot fluids exit through a clay alteration cap that largely consists of kaolinite the si deep hole hydrothermal vents are analogous to steam heated hot springs elsewhere in yellowstone national park ynp e g the mud volcano area which are typified by fumaroles and acid sulfate fluids these deep sublacustrine vent fluids are more aptly termed carbonic acid sulfide owing to a lack substantial sulfate from h2s oxidation and acidity attributed to dissolved co2 at 53 m depth vent fluids at the se wt field achieve temperatures of up to 141 c these neutral chloride fluids are largely similar to those that produce siliceous deposits in many subaerial ynp geyser basins geothermometry calculations and binary mixing relationships indicate the se wt field fluids equilibrated at 207 to 224 c following mixing between oxygenated dilute cold groundwater and a fluid with t 345 to 364 c cl 400 ppm and d 149 vsmow broadly similar to the putative deep parent fluid that supplies most geyser basins in ynp the d values of se wt field fluids cannot be derived from lake water implying km scale lateral hydrothermal fluid flow from outside the boundary of yellowstone lake the fluid compositions and hydrothermal processes operating in the two sublacustrine vent systems are distinct but the overarching influence of magmatic heating complex degassing and alteration mineralization effects are broadly comparable to those that affect their subaerial counterparts the high temperatures and hydrostatic pressures of the sublacustrine vents however provide a window into the evolution of fluid chemistry in more deeply seated and less accessible regions of the subsurface ynp and similar volcanically active hydrothermal systems elsewhere

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

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

in situ identification of water permeable fractured zone in overlying composite strata abstract the height and boundary shape of a water permeable fractured zone wfz play an important role in mining safety under challenging conditions for example when the coal seam is subject to a confined aquifer or the roadway is designed in close range to the coal seam for the accurate estimation of the wfz height the theoretical prediction method was introduced based on the overlying composite strata structure and an empirical equation in situ detection of the wfz height and shape was performed in the zhaizhen coal mine china the field detection was executed by injecting water into boreholes based on the analysis results of the variation in water seepage along these boreholes the fracture intensity and the permeability of the overlying strata were studied and the height and boundary shape of the wfz were also confirmed the measured height was consistent with the theoretical estimation verifying that the wfz developed upwards through the strata group acting as a unit the final boundary of the wfz presented an irregular saddle shape and the boundary angle was approximately 75 78 according to the height and shape of the wfz induced by mining of the lower coal seam the fracture intensity and scope of the surrounding rock and the mining feasibility of the upper coal seam was evaluated in the zhaizhen mine a suitable roadway layout of the upper coal seam was also designed

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

hydrothermal changes related to earthquake activity at mud volcano yellowstone national park wyoming the mud volcano hydrothermal area in yellowstone national park is near the intersection of a 20 km long zone of northeast trending normal faults with the eastern resurgent dome within the 600 000 year old yellowstone caldera recent crustal uplift along the northeast trending axis of the caldera is at a maximum 700 mm since 1923 near the mud volcano area from 1973 through april 1978 less than 10 earthquakes largest m 2 4 were located within 3 km of the mud volcano area in may 1978 earthquakes began occurring beneath the hydrothermal area at depths of 1 to 5 km the seismic activity continued until the end of november with intense swarms 100 events per hour occurring on october 23 and november 7 the largest event m 3 1 occurred on november 14 and at least 8 events were m 2 5 or larger in december 1978 heat flux in the mud volcano hydrothermal features began increasing along a 2 km long northeast trending zone existing mud cauldrons became more active new mud cauldrons and fumeroles were formed and vegetation primarily lodgepole pine was killed by increased soil temperature the increase in heat flux continued through july 1979 then gradually declined reaching the early 1978 level by june 1980 the spatial and temporal association of earthquakes and increased hydrothermal activity at mud volcano suggests that the seismic activity expanded preexisting fracture systems premitting increased fluid flow from depths of several kilometers

tracking changes in the specific storage of overburden rock during longwall coal mining the hydraulic properties of geologic formations such as specific storage and hydraulic conductivity are known to vary spatially due to formation heterogeneity however they may also change temporally if the formation undergoes mechanical disturbance such as occurs during mining characterising changes in hydraulic properties is important for groundwater systems that are disturbed by mining conventional hydrogeological investigations rely on literature derived values or limited programs of field testing e g pumping test to define specific storage but these approaches do not consider the change in compressibility that may occur due to mechanical disturbance this paper presents for the first time direct in situ measurements of the changes in compressibility and consequently specific storage as a result of mechanical disturbance within geologic formations overlying underground mining operations the in situ measurements of compressibility are derived in this study from the pore pressure response to barometric loading or strains induced by earth tides even prior to disturbance the compressibility obtained from in situ measurements was found to be an order of magnitude lower than that measured on core samples by unconfined strength test in the laboratory the differences in compressibility for the intact formation are likely due to sample disturbance and the differences in strain level imposed by the field and laboratory methods the increase in compressibility of the overburden rock varied with the location of the monitoring site relative to longwall extraction and the level of strain the formation sustained the study found that quantifying the changes in compressibility and consequently specific storage as a result of mine induced disturbance is critical to our understanding of subsidence the extent of depressurization and the impact that mining may have on regional groundwater flow systems

bulking factors and extents of caved zones in weathered overburden of shallow abandoned underground workings abstract a comparison between the bulking factor and height of the caved zone for different weathered subsurface rocks over shallow abandoned mines and for strong rocks at intermediate and large depths of longwall mining is performed in this study vertical boreholes drilled from the ground surface have been used to detect the height of caving in weathered w and very weathered vw rock mass overlying abandoned underground workings at a shallow depth and then to calculate the bulking factor it is found that key parameters that control the bulking factor k and the ratio between the heights of caving and mining h h are different for w and vw rocks in w rocks such parameters are the rock strength of immediate roof and rock porosity whereas those for vw rocks are rock quality designation rqd and standard linear fracture intensity p10 it is argued that h h in vw rocks increases according to linear logarithmic law with an increasing ratio p10 rqd in the immediate roof and p10 in four rock layers over the immediate roof observations show that vw rocks exhibit smaller values of k 1 06 1 165 and larger h h 6 07 15 6 compared to w rocks having 1 09

a nd isotope investigation of sediments related to crustal development in the british isles the times of original fractionation of the sm and nd component of clastic sediments from a mantle source crustal residence age have been estimated from sm nd model ages calculated relative to a depleted mantle evolution in this way the provenance and evolution of selected precambrian and phanerozoic sediments and metasediments from the british isles have been examined whereas some archaean and early proterozoic sediments have sm nd model ages that are close to their stratigraphic age the phanerozoic sediments analysed have model ages as much as 2 0 ga in excess of their stratigraphic age a more detailed study of lower palaeozoic sediments deposited on the northern margin of the iapetus ocean provides evidence for a marked change of provenance in the ordovician after the deposition of the dalradian supergroup a component with comparatively high143nd 144nd and sm nd ratio presumably basaltic is present in the sediments throughout the accretionary prism crustal residence age estimates average about 1 5 ga for both these lower palaeozoic sediments and modern pelagic clays and collectively fail to provide any evidence for significant continental growth during the phanerozoic

high temperature hydrothermal vent fluids in yellowstone lake observations and insights from in situ ph and redox measurements abstract rov investigation of hydrothermal fluids issuing from vents on the floor of yellowstone lake revealed temperatures in excess of 170 c the highest temperature yet reported for vent fluids within yellowstone national park ynp the study site is east of stevenson island at depth of approximately 100 125 m in situ ph and redox measurements of vent fluids were made using solid state sensors designed to sustain the elevated temperatures and pressures ysz membrane electrode with ag ag 2 o internal element and internal pressure balanced ag agcl reference electrode were used to measure ph while a platinum electrode provided redox constraints lab verification of the ph sensor confirmed excellent agreement with nernst law predictions especially at temperatures in excess of 120 c in situ ph values of between 4 2 and 4 5 were measured for the vent fluids at temperatures of 120 to 150 c the slightly acidic vent fluids are likely caused by co 2 enrichment in association with magmatic degassing effects that occur throughout ynp this is consistent with results of simple model calculations and direct observation of co 2 bubbles in the immediate vicinity of the lake floor vents simultaneous redox measurements indicated moderate to highly reducing conditions 0 2 to 0 3 v as typical of measurements of this kind internal and external redox disequilibria likely preclude unambiguous determination of redox controlling reactions redox disequilibria however can be expected to drive microbial metabolism and diversity in the near vent environment thus the combination of in situ ph and redox sensor deployments may ultimately provide the requisite framework to better understand the microbiology of the newly discovered hot vents on yellowstone lake floor