the fazenda nova gold deposit goias magmatic arc late neoproterozoic intrusion related auriferous mineralization controlled by intracontinental strike slip faulting abstract the fazenda nova gold deposit with an inferred resource of 650 koz at 4 0 g t au cut off grade of 2 0 g t au consists of stockwork au as mineralization hosted in late neoproterozoic dikes in the goias magmatic arc central brazil the dikes which host the mineralization consist of a set of post collisional ilmenite bearing gabbros dolerites trachyandesite porphyry trachyandesite and trachyte porphyry known as the bacil ndia intrusions u pb dating indicates at least two pulses of dike intrusions the first pulse consists of small volume dikes with ages varying from 593 5 to 590 5 ma and the second pulse comprises a large volume of dikes with ages from 574 7 to 572 5 ma three veining or hydrothermal alteration stages are identified in the fazenda nova deposit the first is the early or main stage which comprises the pervasive biotitization of mafic minerals and a stockwork of quartz associated with a disseminated sulfide assemblage of arsenopyrite pyrrhotite stibnite in addition to hydrothermal siderite scheelite rutile and apatite the most common sulfide in this stage is a fine grained acicular arsenopyrite hosting inclusions of gold galena and pyrite grains the temperature estimated for acicular arsenopyrite pyrrhotite and gold is 340 c based on the arsenopyrite geothermometry the intermediate stage is represented by a stockwork of calcite quartz veins associated with hydrothermal sericite chlorite tourmaline epidote and titanite and a sulfide assemblage of pyrrhotite arsenopyrite pyrite the arsenopyrite at this stage displays a tabular texture with no inclusions of sulfides or gold the crystallization temperature of the tabular arsenopyrite pyrite was estimated to be 305 c the c o isotope data from the calcite veins of the second stage provided 13c values ranging from 9 68 to 11 57 and 18o values range from 12 87 to 13 84 these values are equivalent to those of hydrothermal mantle magmatic carbonates the late stage is represented by veining and brecciation infilled by monotonous calcite ankerite with cockade and colloform vein textures and no gold mineralization the dikes and gold mineralization present a strong relationship with the crustal scale strike slip bacil ndia fault this is a second order crustal scale fault that branches out of the major crustal scale moipora novo brazil shear zone mnbsz along a nnw direction the bacil ndia fault played an important role in channeling melts and mineralizing hydrothermal fluids to the upper crust the major activity of this fault occurred at 572 ma with the emplacement of the second pulse of dikes and most likely the development of hydrothermal stages in the fazenda nova deposit the collectively evidence allows fazenda nova to be classified as an epizonal reduced intrusion related deposit following that i the mineralization developed in a post collisional tectonic setting above previously metasomatized subcontinental lithospheric mantle ii the dikes crystallized from metaluminous magmas with a primary oxidation state which formed the ilmenite series intrusions iii the ore deposition had relatively high temperatures 340 300 c and vein textures formed only at shallow depths

undersea longwall mining subsidence with special reference to geological and water occurrence criteria in the north east of england coalfield abstract to date the use of classical statistical techniques for the identification and analysis of parameters which control the occurrence of water on longwall panels has proved inconclusive an alternative and potentially more meaningful approach is to examine the interaction between the tensile strain induced by mining and the geological and hydrogeological environment surrounding the workings after a brief description of the geology and hydrogeology of the north east of england coalfield the paper examines in detail the water yield predicted tensile strain and geological strain water relationship occurring at four collieries with extensive undersea workings blackhall horden dawdon and westoe in each case water occurrences can be correlated with either faces worked in the vicinity of a major fault where aquifer horizons are displaced against coal measures strata overlying the working horizon or areas where the amount of cover to the base of the major aquifer horizon thins appreciably or a well developed potentially water bearing sandstone horizon exists within the intervening coal measures strata

a coupled flow stress damage model for groundwater outbursts from an underlying aquifer into mining excavations abstract uncontrolled groundwater outbursts from underlying limestone aquifers into mining excavations present a significant safety challenge for underground coal mining in china although these mining hazards have been known for decades the mechanism for groundwater outbursts remains elusive a fully coupled flow stress damage model is presented to simulate the progressive development of fractures and the associated groundwater flow under incremental loading conditions resulting from mining processes the model is based on classical theories of porous media flow and damage mechanics and importantly links changes in permeability with the accumulation of damage in following the complete stress strain process this coupled flow stress damage model is applied to examine the influence of mining advance on the initiation extension and evolution of an outburst conduit as it develops adjacent to the mine panel fractures are shown to initiate both from the wings of the excavation in shear and from the center of the floor span in extension the growth of the extensile fractures is stunted by the presence of a high stress abutment but the wing fractures extend with one fracture becoming dominant as the dominant fracture develops into the underlying over pressured zone water pressures transmitted along the now open conduit reduce effective stresses and develop rapid heave displacements within the floor the result is a groundwater outburst the modeling is tuned to the results of laboratory experiments and follows the evolution of a viable outburst path observations corroborate with field measurements of permeability pre and post mining and are strong indicators of the veracity of the approach

investigation on the characteristics of overlying strata caving in the chengchao iron mine china in this study a comprehensive assessment of the overlying strata caving characteristics of mental mines is conducted for the non pillar sublevel caving method especially considering the geological features and rock mass characteristics in general the overlying strata caving process can be divided into four stages the intermittent roof caving stage the crack extension and surface subsidence stage the karst collapse stage and the mining induced collapse stage roof caving is an intermittent process with higher caving occurring in stronger rock masses and occurs more easily in weaker rock masses due to gaps generated in the overlying rock mass the bulking coefficient of the overlying strata is much greater than the laboratory measured value it also varies with the mining advance lines during the crack extension and surface subsidence stage the surface deformation is less extensive when the rock strength is greater and the gradient of surface deformation is lower when the rock mass integrity is lower thus higher mining height and lower rock mass quality result in greater surface deformation furthermore weak planes such as faults and joints can help to generate fissures in weathered rock masses these fissures create passageways for groundwater flow which accelerates crack extension and connection in reverse in addition surface collapses can be divided into karst collapses and mining induced collapses because a large number of fissures and a high karst rate create favorable conditions for karst collapse significant variations in groundwater levels can induce karst collapse at the surface with high negative pressure forming in the karst caves mining induced collapses are mainly related to the mining depth mining height and the properties of the overlying rock mass underground mining is a major factor in surface collapse and heavy rainfall can induce a delayed but sudden collapse

stress effects on permeability in a fractured rock mass with correlated fracture length and aperture the effect of stress on permeability and fluid flow patterns in fractured rock masses is studied when distributed fracture aperture is correlated with fracture trace length using a discrete elemen

a continuum approach for estimating permeability in naturally fractured rocks abstract many models for predicting permeability in rock masses have been proposed however most of these models do not relate the conductivity closure behavior to fracture geometry parameters and geostati stresses in this study an attempt is made to estimate the permeability tensor as well as the relation between permeability and depth on naturally jointed rocks the new model includes effects of hydromechanical coupling normal closure and fracture geometry the fracture tensor related only to the fracture geometry aperture size and orientation is introduced to formulate a permeability tensor fracture aperture estimated by a simple field investigations is defined as a function of joint roughness coefficient jrc joint wall compression strength jcs and geostatic stress an actual rock mass of jointed andesite rock on the lan yu site taiwan was studied to predict the permeability and conducting aperture with depth through a comparison of the presented model with three existing models 1 the simple one parallel fracture set model 2 the three orthogonal fracture set model and 3 the random disc fracture model it was shown that permeability depth relations for the three orthogonal fracture set model and the new model are almost the same

exhumation of the sanbagawa blueschist belt sw japan by lateral flow and extrusion evidence from structural kinematics and retrograde p t t paths

crustal development of the hida belt japan evidence from nd sr isotopic and chemical characteristics of igneous and metamorphic rocks abstract chemical and sr nd isotopic investigations were performed on the igneous and metamorphic rocks in the hida belt central japan to clarify their ages and possible sources and to provide constraints on the crustal evolution of the eastern margin of the asian continent igneous rocks of three main stages in the hida belt represented by the late silurian amphibolites first stage the middle carboniferous mafic dikes second stage and the late triassic to early jurassic granite gabbro plutons third stage show alkaline to calc alkaline chemical affinity major and trace element characteristics show that the three stages of igneous rocks were emplaced in a continental margin or continental arc environment the mafic igneous rock suites have relatively high e nd 0 5 to 5 5 and low 87 sr 86 sr 0 7049 to 0 7061 values indicating their origin from upper mantle sources though the third stage granitoids contain recycled crustal components the hida gneisses of clastic origin show two groups of model ages t dm middle proterozoic 1 4 2 2 ga and late proterozoic to early paleozoic 0 55 0 74 ga consistent with geological geochemical and radiometric age data are that the sedimentation and basaltic volcanism occurred in early to middle paleozoic and the protoliths with middle proterozoic model ages are detritals from the proterozoic continental provenances a synthesis of available geological and geochemical data for the basement metamorphic and igneous rocks in eastern asia suggests two possibilities for the paleozoic to early mesozoic history of the hida belt 1 the hida belt was formed at the eastern margin of the north china block with later evolution as a suture zone between the north and south china blocks or 2 it evolved as a part of the east central asian orogenic belt ecaob to the north

enriched sr nd isotopic characteristics of amphibolites in the oki dogo island japan evidence for crust mantle interaction by deeply subducted continental crust

relationship between hydrogeological parameters for data scarce regions the case of the araripe sedimentary basin brazil this paper applies and validates a method for generating spatially distributed hydraulic conductivity k based on the specific capacity qs for data scarce regions this method has been applied to the araripe sedimentary basin brazil and consists of four steps 1 selection of 32 wells for which both k and qs data are available 2 estimation of k as a function of qs for the 128 wells for which only specific capacity data are available 3 spatial distribution of k using the kriging geostatistical tool 4 validation of the method using 17 representative wells with k measured data the equation relating k and qs showed a statistically significant linear relationship r 0 93 from which a database has been generated using kriging with the spherical model the results showed a calibration coefficient of nash and sutcliffe ns of 0 54 and moderate spatial dependence ratio of 69 the validation process provided only a moderate efficiency ns 0 22 possibly due to the geological complexity of the focus system despite its limitations the method indicates the possibility of application of ordinary kriging to generate reliable data from auxiliary variables especially for the water management of data scarce areas

evaluation of rock mass permeability tensor and prediction of tunnel inflows by means of geostructural surveys and finite element seepage analysis abstract in this paper a new practical technical approach for the evaluation of hydraulic conductivity and tunnel water inflow in complex fractured rock masses is presented this study was performed in order to evaluate water flow into tunnels planned along the new highway project from firenze nord gate to barberino di mugello tuscany the results are based on detailed and comprehensive geostructural characterization of rock masses by means of field surveys geological and hydrogeological studies starting from discontinuities properties surveyed in the field the permeability k tensor was calculated using the kiraly equation integrated with the introduction of the effective hydraulic opening of fissures e principal directions of tensor k were calculated for each geostructural survey station using an automated software script especially developed for this purpose available k data from lugeon tests were also collected and analyzed with results that do not fully represent the rock mass due to its structural hydraulic variability in order to evaluate water flow into tunnels planned for excavation under the water table for a total number of eight a finite elements seepage analysis was performed on 38 representative geological sections transverse to tunnel paths planes each section referred to the nearest and geologically most compatible geostructural station principal directions of k tensors were projected on the planes by means of trigonometric transformations unitary water inflows were then evaluated for long term steady state as well as for initial state immediately after tunnel excavation inflow values calculated for each unitary section were extended to geologically homogeneous lengths of the tunnel according to the variability of the water head above excavation and then summed up for the whole length of each tunnel inflow values obtained with fe seepage analysis were also compared to other inflow evaluation methods

hydrochemical characteristics of groundwater movement and evolution in the xinli deposit of the sanshandao gold mine using fcm and pca methods the objective of this study is to characterize the physicochemical properties of groundwater in the sanshandao gold deposit analyze the laws of motion and evolution of the groundwater system and provide evidence for the design of undersea mining and safety warnings using combined fuzzy c means fcm and principal component analysis pca methods thirteen physicochemical indicators and two isotopic indicators were surveyed from 100 fissure water samples and 13 typical water samples from xinli a deposit of the sanshandao gold mine in china first pca was used to extract four pcs with explained variances 48 25 10 and 7 and the characteristics of the hydrochemistry indicators of each pc were examined the four pcs are identified as the processes of concentration and dilution sericite rock orientation and carbonatization potash feldspathization and dissolution of carbon dioxide next using the four pcs developed from pca 100 fissure water samples were grouped into four spatially continuous clusters using the fcm cluster method with the aid of graphic technology the four fuzzy clusters were determined as deep saline water shallow saline water bedrock brine and mixed wastewater following careful analysis of the hydrochemical characteristics of each cluster combined with a related hydrogeological report finally further analysis of the pca and fcm results determined factors constituting the groundwater system including sources of water flow path mixing zone local fissure zone and impact of mining on the groundwater system this study shows that the combination of pca and fcm is important for understanding hydrochemical characteristics of a groundwater system

interpretations of a middle miocene and late quaternary steady dextral transpression in sw japan and the opening tectonics for the japan sea abstract an internal rotation hypothesis for the deformation of sw japan for middle miocene and recent times is studied rotations are known to have occurred from paleomagnetic data for the earlier case two geodetic flow field estimates as well as another tectonic study suggest that the rotations are also taking place at present a further examination of the geodetic flow models suggests that the rotations contained in these flow models are intrinsic to the deformation of sw japan which occurs in an e w dextral transpressive simultaneous pure and simple shear tectonic regime maps of rotation rates one half of vorticity and shear gradients the n s variation of the e w velocity field constructed from the geodetic flow models resemble one another in pattern the estimates of the directions of the principal strain rates from the geodetic models are on the whole n s contractional and or e w extensional which match the geodetic reference coordinate system used in the adjustment of the geodetic data these observations suggest that the vortical flow contained in the geodetic flow models is a frame independent shear induced vorticity as the material is rotating with respect to the principal directions of the strain rates and that the oblique motion of the philippine sea plate is partitioned between shear and arc normal convergence components the rotation rate is 10 12 ma furthermore the kinematical vorticity number estimates from the geodetic data correlate well with the first order tectonic fabric patterns in sw japan super simple shear deformation for large parts of sw japan where the median tectonic line and other large strike slip faults are found is also indicated in the internal kinematical vorticity number estimates a new model for the formation of the japan sea is proposed extrusion of japan due to the okhotsk eurasia collision this model agrees with the fundamental observations of the early middle miocene deformation in the region the application of an indentation extrusion model to the okhotsk eurasia collision results in a better agreement between the predicted and observed structures and leads to simpler more reasonable and coherent interpretations for the origin and development of the structures compared with the achievements of the previous models the nne trending early middle miocene rifts lying along the continental margin of western hokkaido formed as pull apart basins along a sinistral fault related to the collision of the okhotsk plate which segmented in a left handed sense because the collision was oblique the n s trending rifts and the normal faults found in the back arc domain of the ne honshu arc formed by eastward extrusion under the influence of the mariana type subduction in the japan trench these rift basins were subsequently left laterally displaced by movement along nw trending sinistral strike slip faults the shikoku basin opened from the east toward the west and dextral shear was imparted to the sw margin from the nankai trough leading to clockwise rotations in the middle miocene in sw japan the paleomagnetic rotations are accommodated as fully internal structural rotations in the new model for the origin of the japan sea the current episode of deformation in sw japan began 1 5 million years ago after a hiatus during a 15 5 ma interval and is likely a continuation of the middle miocene style of tectonics

seawater inrush assessment based on hydrochemical analysis enhanced by hierarchy clustering in an undersea goldmine pit china seawater inrush is deadly to undersea mine and it is very important to accurately assess the connectivity between seawater and the mine pit with xinli gold mine area as a case study following the analysis of geological setting a detailed hydrogeological survey and sampling were conducted and conservative ions test of mine water samples was carried out in the laboratory furthermore the physical significances of ion concentration and ion ratios such as cl so42 cl and na cl were checked the test data analysis enhanced by the physical significance check and hierarchy clustering analysis was used to assess the overlying seawater inrush into the mine pit it was determined that the undersea rock masses in the xinli mine area bear high mineralization brine water the ore controlling fault gouge and a thin layer of clay in quaternary block the seepage of overlying seawater into the undersea mine pit to a great extent the mine water from surrounding rock of the northeast gopher drift is closer to seawater in hydrogeochemical features which indicates that the connectivity between the northeast of footwall of the ore controlling fault and seawater is relatively good and should be closely monitored in future production the mine water from the southwest gopher drift and crosscuts is similar to the brine salty water in chemical features drains the net reserves of brine salty water in bedrock fissures and will impose few impacts on production in the near future this approach is feasible and cost effective

middle precambrian detrital monazite and zircon from the hida gneiss on oki dogo island japan their origin and implications for the correlation of basement gneiss of southwest japan and korea abstract monazite and zircon from seven paragneiss samples of the upper amphibolite facies grade from oki dogo island in the hida terrane western japan were analyzed for th u and pb on an electron microprobe most monazite grains are chronologically unzoned and give unequivocal chime chemical th u total pb isochron ages of 250 ma but some grains show a distinct core overgrowth relationship the cores retain evidence of pre 250 ma ages and are interpreted to be of detrital origin suggesting that monazite can be more immune to diagenetic and low grade metamorphic decompositions than had been thought previously zircon grains rounded to nearly euhedral give chime ages ranging from 3000 to 350 ma of particular interest are several rounded 3000 ma recycled zircons which perhaps originated from an archean terrain in the sino korean craton the youngest age of detrital zircons constrains that the gneiss protolith deposited after the 350 ma event the chime monazite and zircon ages for the paragneisses from oki dogo island and from the main part of the hida terrane reveal that the gneisses formed from permo carboniferous clastic sediments during a single metamorphism at ca 250 ma the results are in marked contrast to the current view that 1 the hida gneiss is a polymetamorphosed precambrian complex 2 the central part hida gneiss region and the eastern marginal part unazuki schist region of the hida terrane are correlative with the precambrian kyonggi massif and the paleozoic okchon zone in the korean peninsula respectively instead we consider that the okchon zone alone can be correlatable with the paleozoic hida terrane

numerical experiments on permeability tensor and its application to jointed granite at stripa mine sweden rock masses containing a large number of geological discontinuities called joints are treated as homogeneous anisotropic porous media a permeability tensor hydraulically equivalent to a flow network formed by joints is formulated in terms of two tensors and a nondimensional scalar both depending only on the geometrical aspects of joints such as the spacing size orientation and aperture two dimensional numerical analyses on seepage flow through the networks support the validity of the present theory the information about the geometry of joints which is obtained from the ventilation drift at stripa mine sweden is interpreted to give the corresponding permeability tensor the permeability tensor is compared with the result of the large scale hydraulic conductivity test with the conclusion that it provides a reasonable prediction for the hydraulic properties of stripa jointed granite

mining subsidence and its effect on the environment some differing examples the impact of mining subsidence on the environment can occasionally be very catastrophic destroying property and even leading to the loss of life usually however such subsidence gives rise to varying degrees of structural damage that can range from slight to very severe different types of mineral deposits have been mined in different ways and this determines the nature of the associated subsidence some mining methods result in contemporaneous subsidence whereas with others subsidence may occur long after the mine workings have been abandoned in the latter instance it is more or less impossible to predict the effects or timing of subsidence a number of different mineral deposits have been chosen to illustrate the different types of associated subsidence that result and the problems that arise the examples provided are gold mining in the johannesburg area bord and pillar mining of coal in the witbank coalfield south africa longwall mining of coal in the ruhr district mining of chalk and limestone in suffolk and the west midlands respectively and solution mining of salt in cheshire these mineral deposits have often been worked for more than 100 years and therefore a major problem results from abandoned mines especially those at shallow depth the presence of which is unrecorded abandoned mines at shallow depth can represent a serious problem in areas that are being developed or redeveloped abstraction of natural brine has given rise to subsidence with its own particular problems and cannot be predicted although such abstraction is now inconsequential in cheshire dereliction associated with past subsidence still remains

engineering geology ground surface movement and fissures induced by underground mining in the jinchuan nickel mine the jinchuan nickel mine is the largest underground mine with cut and fill mining in china in 1999 there appeared evident ground surface movement and many ground fissures in jinchuan no 2 mine following an introduction to the engineering geology and mechanical properties of the rock mass in the jinchuan mine areas this paper reveals the features of the measured in situ stresses and puts emphasis on an analysis of the mechanism of surface movement and ground fissures induced by the underground mining with backfill it is indicated that both the fault structures and the alteration contact zones are well developed as the dominant engineering geological characteristics in the jinchuan mine areas the stress redistribution in surrounding rocks resulting from the mining the low stiffness of the filling body the existence of the void space and the influence of on going mining activities is the main reason for the occurrence of surface movement and ground fissures

estimation of rev size and three dimensional hydraulic conductivity tensor for a fractured rock mass through a single well packer test and discrete fracture fluid flow modeling abstract a new methodology is presented to determine the representative elementary volume rev size and three dimensional 3 d hydraulic conductivity tensor for a fractured rock mass first a 3 d stochastic fracture network model was built and validated for a gneissic rock mass based on the fracture data mapped from scanline surveys at the site this validated fracture network model was combined with the fracture data observed on a borehole to generate a stochastic deterministic fracture network system in a cubic block around each packer test conducted at a different depth region in the same borehole each packer test was simulated numerically applying a developed discrete fracture fluid flow model to estimate the influenced region or effective range for the packer test a cubic block of size 18 m with the packer test interval of length about 6 5 m located at the centre of this block was found to be suitable to represent the influenced region using this block size the average flow rate per unit hydraulic gradient defined as the transmissivity multiplied by mean width of flow paths field for fractures was calibrated at different depth regions around the borehole by numerically simulating the packer tests conducted at different depth regions the average flow rate per unit hydraulic gradient of the fractures that intersect the borehole was considered to be quite different to the average flow rate per unit hydraulic gradient of the fractures that do not intersect the borehole a relation was developed to quantify the ratio between these two parameters by studying the directional hydraulic conductivity behaviour of different cubic block sizes having the validated stochastic fracture network and calibrated hydraulic parameters a rev for the hydraulic behaviour of the rock mass was estimated to be a block size of 15 m the hydraulic conductivity tensor in 3 d computed through regression analysis using the calculated directional hydraulic conductivity values in many directions was found to be significantly anisotropic the principal directions of the hydraulic conductivity tensor were found to be agreeable with the existing fracture system of the site further the geometric hydraulic conductivity calculated was found to be comparable to the hydraulic conductivity estimated through the radial flow assumption in continuum porous media

study of the hydrogeological characteristics and permeability of the xinli seabed gold mine in laizhou bay jiaodong peninsula china this paper presents a case study investigation into the hydrogeological characteristics and permeability of rock mass in a seabed mine following an introduction to the geology and hydrogeological conditions in the xinli mine area we reveal the features of the preferred structural planes dynamic characteristics of mine water seepage and the permeability of the fractured rock mass in the pit the permeability of the pit rock mass shows varied characteristics at different geotectonic locations because of the different degrees to which the structural planes developed the fractured rock mass generally shows low permeability and the main composition of water seepage is high salinity brine future large scale undersea mining may induce rock mass movement destroy water resistant layers and enhance water transmissibility and the probability of water gushing into the pit thus strengthening the quality of the filling mass protecting the stope roof and the water resistant layers as well as regular monitoring of water seepage discharge and identification of water sources are critical to work safety and the prevention of seawater gushing in the mine

hydraulic properties of fractured rock masses with correlated fracture length and aperture permeability of fractured rocks is investigated considering the correlation between distributed fracture aperture and trace length based on a newly developed correlation equation the influence of