anisotropy of gas permeability associated with cleat pattern in a coal seam of the kushiro coalfield in japan an underground investigation has been performed in a subbituminous coal seam exhibiting a particular cleat pattern in the kushiro coalfield japan the coal cleat pattern shows some analogy to isolated straight joints and is believed to have been formed during the late tertiary period by a compressive tectonic stress roughly in the east west direction three cylindrical coal specimens representing the three orthogonal axes of the coal seam with respect to the bedding plane and its associated cleat were cored from a large block of coal gas permeabilities of the three coal specimens were measured under the same hydrostatic pressure conditions results clearly revealed anisotropy in permeability of the coal seam under relatively low confining pressures of less than about 12 mpa the specimen cored parallel to both the bedding plane and cleat strike showed the highest permeability even though the cleats were partly filled with calcite and clay minerals the permeability in this direction was 2 5 times higher than perpendicular to the bedding plane and 3 times higher than in the direction parallel to the bedding plane but perpendicular to the cleat strike this suggests that the cleats play a greater role than bedding planes in controlling fluid flow in the coal seam the permeability in the three orientations however converged to the same value at confining pressures above about 16 mpa this may suggest that both cleats and bedding planes in a coal seam can close due to earth pressure if the coal seam is located below a certain depth it further indicates that the traditional view that gas permeability is always greater parallel to the coal bedding than perpendicular to it should be reconsidered

gold speciation and transport in geological fluids insights from experiments and physical chemical modelling this contribution provides an overview of available experimental thermodynamic and molecular data on au aqueous speciation solubility and partitioning in major types of geological fluids in the earth s crust from low temperature aqueous solution to supercritical hydrothermal magmatic fluids vapours and silicate melts critical revisions of these data allow generation of a set of thermodynamic properties of the auoh aucl 2 auhs and au hs 2 complexes dominant in aqueous hydrothermal solutions however other complexes involving different sulphur forms chloride and alkali metals may operate in high temperature sulphur rich fluids vapours and melts the large affinity of au for reduced sulphur is responsible for au enrichment in s rich vapours and sulphide melts which are important gold sources for hydrothermal deposits thermo dynamic speciation and partitioning data and their comparison with au and s contents in natural fluid inclusions from magmatic hydrothermal gold deposits provide new constraints on the major physical chemical parameters temperature pressure salinity acidity redox and ubiquitous fluid components sulphur carbon dioxide arsenic affecting au concentration transport precipitation and fractionation from other metals in the crust the availability and speciation of sulphur and their changes with the fluid and melt evolution are the key factors controlling gold behaviour in most geological situations

mafic magmas as sources for gold in middle miocene epithermal deposits of the northern great basin united states evidence from pb isotope compositions of native gold we measured the pb isotope compositions of traces of lead alloyed by gold electrum and naumannite and gangue vein minerals in bonanza epithermal gold deposits of the northern great basin and compared them to possible sources of lead in the region gangue minerals have pb isotope compositions consistent with hydrothermal leaching of lead from local host rocks lead isotope ratios of gold ores however have signatures that are distinct from the gangue minerals and common host rocks in the area such as metasediments and miocene rhyolites the gold ores are isotopically similar to local mafic rocks of the middle miocene bimodal volcanic assemblage indicating that the latter are the likely source of the precious metals the local mafic rocks are also similar to the middle miocene columbia river basalts suggesting that both were derived from a mantle source with similar pb isotope composition our preliminary results indicate that the precious metals were derived from mafic magmas likely related to northern nevada rifting processes and or to the arrival of the columbia river basalt plume and the emergence of the yellowstone hot spot exsolving volatiles from the mafic magmas most likely transported gold upward to the shallow meteoric water dominated epithermal systems where the precious metals precipitated together with quartz and adularia to form bonanza ores that typify these deposits

permeability distribution characteristics of protected coal seams during unloading of the coal body abstract based on the engineering practices used in mining the protective coal seam at huainan coalfield in china this study investigates the temporal evolution of three dimensional stress of the protected coal seam by numerical simulation the coal body of the protected coal seam should first be loaded and then unloaded with the three dimensional stress being reduced simultaneously in accordance with the forcing process around the coal body of the protected coal seam permeability experiments were performed under fixed axial displacement with unloading confining pressure faducp and fixed deviatoric stress with unloading confining pressure fdsucp stress paths during the loading stage before the unloading point the permeability and axial strain have a negative exponential relationship however during the unloading stage after the unloading point the permeability and axial strain have a positive exponential relationship using the relationship between permeability and axial strain along with the swelling and deformation of the protected coal seam the permeability distribution characteristics for the protected coal seam was obtained according to the permeability distribution characteristics of the protected coal seam drilling designs for gas drainage can be optimized finally the rationality of the drilling design was verified using gas data measured during mining of the protected coal seam

a physical and numerical model based research on the subsidence features of overlying strata caused by coal mining in henan china the major environmental consequence of coal mining is anthropogenic land subsidence in particular mine subsidence can cause damage to public and private infrastructure such as railroads roads pipelines and buildings what is more it is an engineering problem which troubles engineering construction and safety ground surface deformation is related to the measure of mining and the deformation mechanism of overlying strata above the gob in this paper a physical and numerical model on the subsidence of longwall mining within a geotechnical setting is presented the physical model is developed within the framework of physical similar law and geological model in henan province china the numerical solution is developed within continuum poromechanics and finite element setting the law of overlying strata deformation is obtained according to physical model experiment and numerical simulation

a study of hardness and fracture propagation in coal the surface hardness of coal was estimated using a shore scleroscope rebound hardness ssrh tester ssrh can be related to fracture toughness and strength and was trialled as a quick field test to illustrate variability in these properties for coal seam gas reservoirs therefore samples were selected to include different coal ranks and lithotypes from a suite of boreholes that intersect permian coal seams within the bowen basin in queensland australia the tests were conducted unconfined on slabbed coal core and confined on epoxy encased coal blocks used for coal petrographic examination the test results of the unconfined samples show that the hardness varies with lithotype it increases with decreasing amount of bright bands moreso than coal rank or thermal maturity the test results of the confined samples show little variation with lithotype but show a parabolic correlation of hardness with rank similar to the behaviour found with hardgrove grindability tests the resulting fractures of the ssrh test were analysed under the microscope to understand the fracture pattern which can be scaled up to understand fracture propagation in natural systems and when induced in gas reservoirs

la icpms and epma studies of pyrite arsenopyrite and loellingite from the bhukia jagpura gold prospect southern rajasthan india implications for ore genesis and gold remobilization abstract the bhukia jagpura gold prospect is hosted by a paleoproterozoic metasedimentary rock sequence that constitutes the lowermost part of the aravalli supergroup lying in close proximity to the basement cover contact a combined ore petrographic la icpms and epma studies of iron sulfides and sulfarsenides from the prospect has revealed four varieties of pyrite and two varieties of arsenopyrite with different trace element compositions the data indicates a sedimentary diagenetic origin for the earliest pyrites py i and ii which are devoid of any gold in contrast to hydrothermal py iii and iv with a minor but significant content of invisible gold 0 3 1 6 ppm associated loellingite 35 51 ppm and arsenopyrite aspy i 0 28 10 ppm contain the maximum concentration of invisible gold while it is substantially lower in aspy ii 0 06 1 5 ppm the compositions of the gold bearing pyrites low ni co ratios arsenopyrites and loellingite rich in co and the presence of au bi te mineral phases within arsenopyrite support a magmatic hydrothermal model for the origin of gold sulfide mineralization which appears to have taken place during the peak of regional metamorphism or at an earlier stage the different stages of deformation and metamorphism released and remobilized gold in invisible and discrete forms from the sulfarsenides during prograde metamorphism of aspy i gold was partially incorporated and relatively enriched within the structure of loellingite later during retrograde metamorphism gold was exsolved as visible grains at the interface of loellingite and aspy ii and or within loellingite

geology of the bousquet 2 mine an example of a deformed gold bearing polymetallic sulfide deposit the bousquet 2 mine is a deformed pyritic polymetallic archean gold deposit located within a zone of intense ductile brittle deformation composed of highly sheared and altered metamorphic tectonites of contrasting rheological properties the ore occurs in a metamorphosed zone of aluminous alteration and is composed of foliation parallel massive and semimassive pyritic lenses overprinted by late en echelon extensional veinlets containing au ag cu mineralization structural and textural analyses show that the gold bearing sulfide bodies and enclosing host rocks contain discrete tectono metamorphic features resulting from two principal episodes of metamorphism m 1 and m 2 the earlier prograde event m 1 and coeval regional deformation d 1 were accompanied by overall ductile deformation of sulfides and by recrystallization and remobilization of the mineralization parallel to foliation m 1 caused development of a pervasive east west trending metamorphic layering of the pyritic mineralization transposition and elongation of the pyritic bodies parallel to mineral stretching l 1 lineations meter scale folding of sulfides sulfide brecciation coarsening and annealing recrystallization of pyrite and ductile remobilization of incompetent sulfides and gold into interstices and triple point junctions of juxtaposed pyrite grains extensive differential remobilization of ductile sulfides mainly sphalerite pyrrhotite galena chalcopyrite chalcocite and bornite and gold took place during m 1 and gave rise to planar zones enriched in au ag cu mineralization along the interfaces of pyritic lenses and their adjacent silicate rocks m 2 metamorphism is chronologically related to a late brittle incremental stage of the progressive deformation and is characterized by high fluid influx pervasive retrogression of peak metamorphic minerals and remobilization of sulfides and gold into transgressive structures the retrograde mineralization displays a wide range of small scale structures resulting from fluid assisted remobilization of ductile sulfides including piercement and injection structures as well as foliation oblique extensional veinlets metamorphic remobilization of ore constituents took place mainly at ore wall rock interfaces fe pb zn and au ag cu bearing extensional veinlets generally occur in foliation parallel protores of similar mineralogical composition and are interpreted as having resulted from in situ metamorphic remobilization gold and copper show a corelationship throughout the deposit the highest gold and copper values occur within extensional veins overprinting previously au cu enriched planar zones mineralogical zoning in the sulfide masses is structurally controlled and can be related directly to abundant au cu bearing veinlets that represent mineralized segments of a systematic joint system structural and textural evidence suggests that gold mineralization with its present textural relations formed during m 1 and m 2 but that a large proportion of the structurally controlled vein mineralization resulted from in situ remobilization rather than from additions from an external source

geochronology of the midas low sulfidation epithermal gold silver deposit elko county nevada the midas deposit is the largest known high grade au ag vein deposit located along the northern nevada rift it belongs to a suite of middle miocene low sulfidation epithermal systems associated with magmatism and faulting along the rift interpretation of new 40ar 39ar dates for volcanic rocks and hydrothermal minerals related to gold mineralization and additional isotopic dates throughout the midas region constrain the timing of volcanic tectonic and hydrothermal activity the midas hydrothermal system developed following a change from mafic dominated bimodal volcanism and basin formation to felsic volcanism folding and faulting at about 15 6 ma from 15 6 to 15 2 ma sediments and tuffs were deposited on a relatively impermeable rhyolite flow during this period faulting and tilting of the volcanic edifice created pathways for hydrothermal fluids that flowed to the surface forming sinters and hydrothermal breccias approximately 200 kyr after the change in volcano tectonic regime oblique slip faulting took place along zones of preexisting weakness creating dilational zones and additional channelways for mineralizing fluids at 15 4 ma high grade veins formed in fault zones throughout the region depositing at least 4 million ounces moz of gold and 40 moz of silver the timing of high grade au ag mineralization is identical to the age of rhyolite intrusions whose source magma chamber likely provided the heat necessary to drive the hydrothermal system the age of an unaltered tuff that unconformably overlies opalized sediments establishes that tilting of the units and the hydrothermal system had ceased by 15 2 ma the temporal and spatial coincidence of rhyolite volcanism faulting and high grade mineralization may reflect the importance of contributions from deeper fluid reservoirs containing magmatic components or highly exchanged meteoric waters

platinum group minerals in the santo tomas ii philex porphyry copper gold deposit luzon island philippines mineralized quartz diorites of the santo tomas ii porphyry copper gold deposit carry high au contents average 1 8 ppm as well as 160 ppb pd and 38 ppb pt values of other platinum group elements pge and rhenium are below the analytical detection limits there is a significant positive correlation between au and cu the highest pd values were detected in the most au and cu rich rocks platinum group minerals pgm occur exclusively as inclusions in chalcopyrite and bornite potential pd and pt contents in sulphide concentrates are estimated at 1 5 g t and 0 4 g t respectively the precious metal assemblages consist of merenskyite main pgm kotulskite moncheite native gold electrum hessite and petzite polyphase fluid inclusions in quartz veinlets associated with a pgm bearing bornite chalcopyrite magnetite assemblage are characterized by high salinity 35 to 60 eq wt nacl and high trapping temperatures between 380 and 520 c they may represent primary magmatic hydrothermal fluids which have been responsible for the transport of pd pt and au as chloride complexes

permeability evolution during progressive deformation of intact coal and implications for instability in underground coal seams abstract we report measurements of deformation strength and permeability evolution during triaxial compression of initially intact coals permeability is continuously measured by the constant pressure differential method together with axial and volumetric strains for both water h2o and strongly adsorbing carbon dioxide co2 gas strength and young s modulus increase with increasing confining stress and permeability is hysteretic in the initial reversible deformation regime as deviatoric stress and strain increase permeability first decreases as pre existing cleats close and then increases as new vertical dilatant microcracks are generated post peak strength the permeability suddenly increases by 3 4 orders of magnitude during loading the inflection point where permeability begins to increase occurs earlier than the turning point of volumetric strain which may be explained by the competing processes of axial crack opening and closure of oblique and transverse cracks the generation of these vertical microcracks does not enhance gas migration in the horizontal direction but will accelerate the rate of gas desorption and weaken the coal based on this mechanistic observation we propose a process based model for bursting in underground coal seams horizontal and vertical stresses redistribute ahead of the mining face immediately after the excavation and influence pore pressure permeability and desorption rate due to this redistribution the zone closest to the mining face may experience tensile failure interior to this zone a region may develop with gas overpressures induced by desorption and this may contribute to the occurrence of coal and gas outbursts beyond this an overstressed zone may initiate shear failure driven by gas pressures if the desorption rate outstrips the rate of drainage we discuss the implications of this on the instability of coal seams to co2 injection and the potential for induced fault slip

bismuth and cobalt minerals as indicators of stringer zones to massive sulphide deposits iberian pyrite belt the stringer zones and commonly the interaction zone at the base of the massive sulphide mounds in the iberian pyrite belt contain bismuth and cobalt minerals that are not found in the overlying massive sulphides these are fairly rare cobalt sulphoarsenides cobaltite alloclasite galucodot that were formed at the beginning of the massive sulphide genesis and fairly common bismuth sulphides bismuthinite hammarite wittichenite cosalite kobellite joseite etc including species rare at world scale nuffieldite giessenite jaskolskiite that were deposited from last stage high temperature 300 c copper bearing fluids containing bi te se the last stage fluids precipitated chalcopyrite containing cu bi te se sulphosalts at the base of the sulphide mound to form a high cupriferous zone their interaction with the massive sulphides is reflected by the formation of an exchange zone a few metres thick showing chalcopyrite disease textures at the base of the mound this zone forms the upper limit of potentially economic copper enrichment and of bismuth minerals gold is undoubtedly in part if not totally related to this last phase the bismuth concentrations being equivalent in the massive sulphides and the stringers the presence of bismuth minerals in the stringer zones results from high temperature conditions combined with a rarity of galena which impedes absorption of available bi the distribution of these bismuth minerals provides a basic mineralogical zoning in the stringer zone with a deep low as2 zone containing native bismuth and tellurides and a shallow higher as2 zone in contact with the massive ore sensu stricto and containing complex bismuth sulphides these results make it possible to distinguish between sulphide veinlets belonging to stockwork zones of massive orebodies and veinlets of an ambiguous nature and provide mineralogical criteria for the proximity of copper rich zones they enrich the very complex mineralogy of the iberian pyrite belt

petrogenetic significance of au bi te s associations the example of maldon central victorian gold province australia abstract mineralization at maldon victorian goldfields australia is part of the western lachlan foldbelt and is hosted by deformed lower ordovician metasediments intruded by the late devonian harcourt granite gold bi te s associations in the deposit include four gold bearing minerals maldonite native gold jonassonite and aurostibite and a range of sulphotellurides from the tetradymite group all of which are paragenetically tied to native bismuth the simpler phase associations involving bismuth maldonite and one or the other bi sulpho tellurides resemble the equivalents of eutectics in the system au bi te and hint at crystallisation from melts the complex associations include symplectites of gold and bismuth resulting from replacement of maldonite and are dominated by co existing sulphur bearing species joseite a joseite b an unnamed phase with bulk composition approximating to bi 3 te s 2 and jonassonite the complexity of such assemblages is also underpinned by chemical structural inhomogeneity within the unnamed phase i e nanoscale domains of bi 14 te s 9 and bi 5 te s 3 as documented from electron diffractions obtained from a fib tem foil although such lattice scale intergrowths reveal polysomatic disorder that can be associated with replacement of one telluride by another the structural modules in the overall stacking sequence indicate formation under local equilibrium conditions the mineralogical complexity of all au bi te s associations can be modelled in terms of interaction between simpler assemblages and sulphur bearing fluids three stages all involving gold minerals are recognised 1 bismuth maldonite hedleyite 2 bi sulphotellurides jonassonite and decomposition of maldonite gold bismuth and 3 bismuthinite gold from decomposition of maldonite or jonassonite the last stage is coincident with chloritisation and occurs during or following granite emplacement thermodynamic modelling of maldonite replacement by bismuthinite and gold indicates conditions to overlap with the pyrite hematite buffer at 258 c if neutral fluids are involved the general replacement model for the deposit shows that local scale reworking of maldonite and resultant gold remobilisation contributed to the apparent abundance of native gold this interpretation is consistent with the protracted geological history at maldon where granite intrusion post dates an orogenic event initial sulphur poor assemblages crystallised from melts predating granite emplacement the latest sulphidation event is attributed to retrograde fluids in the contact aureole whereas the earlier one could also have been produced during the multi stage deformation although observed assemblages and textures are the product of a complex sequence of overprinting there is no need to invoke input of gold from more than a single fluid generation

phase relations among tellurides sulfides and oxides pt ii applications to telluride bearing ore deposits data on telluride bearing mineral assemblages from various types of ore deposits are compiled and interpreted in terms of the prevailing fugacities of te 2 s 2 and the temperature during deposition in the majority of hydrothermal deposits the appearance of tellurides after initial deposition of sulfides reflects an increase in the f sub te 2 f sub s 2 ratio most likely due to input of h 2 te from a magmatic source in some vein deposits such as boulder county colorado initial deposition of native tellurium is followed by deposition of minerals with progressively lower tellurium content indicating a decrease in f sub te 2 over the course of telluride deposition this trend may reflect local isolation of early formed minerals from the hydrothermal fluids and or progressive depletion of tellurium at the source ore minerals in other deposits such as mahd adh dhahab saudi arabia reveal systematic temporal or spatial variations in mineralogy that are attributed to introduction of a tellurium rich fluid into a preexisting sulfide assemblage and subsequent buffering of f sub te 2 and f sub s 2 by reactions such as 2pbs te 2 2pbte s 2 this buffering may exert considerable control on vein minerals such as the presence and relative abundance of gold and calaverite and the presence or absence of native tellurium

mineralogy of bi sulfosalts and tellurides from the yaoan gold deposit southwest china metallogenic implications abstract bismuth sulfosalts and tellurides are commonly present in many hydrothermal gold deposits and can provide important genetic and physicochemical constraints on the metallogenesis the abundant auriferous specular hematite veins in the yaoan gold deposit of the jinshajiang red river alkaline porphyry metallogenic belt southwest china contain an assemblage of bi sulfosalts and tellurides together with hematite pyrite and chalcopyrite bismuth sulfosalts are characterized by replacement textures resulting from changes of fluid composition e g pb bi cu and ag and mainly include bismuthinite derivatives e g bismuthinite paarite krupkaite lindstromite and friedrichite aikinite pad raite cuprobismutite homologues probably submicroscopic intergrowths of hodrushite and cuprobismutite and emplectite tellurides are tiny comprising tsumoite melonite hessite and calaverite which coexist with bismuthinite derivatives these bi sulfosalts and tellurides have direct contact with gold indicating that the yaoan gold metallogenesis was likely linked to the syenite porphyry magmatism that was originally sourced from a regional lithospheric mantle probably metasomatized by subduction of te rich sediments the telluride assemblage also reveals that the gold was precipitated under oxidizing conditions that has a high tellurium fugacity at the beginning fte2 10 7 9 and fs2 10 8 5 at 300 c

initial gold contents of silicic volcanic rocks bearing on the behavior of gold in magmatic systems many fresh silicic volcanic rocks have markedly lower initial gold contents than previously recognized of 129 carefully selected glassy silicic volcanic rocks analyzed 113 contain f o 2 more readily accommodate gold the mean of 23 relatively silicic intermediate rocks is 0 54 ppb au with tholeiitic andesites icelandites generally higher in gold than calc alkalic types there is little evidence that particular geologic regions are intrinsically richer in gold than others bulk composition melt structure and the amount and timing of separation of vapor mineral and sulfide and or metal melt phases would appear to largely determine the gold contents of silicic magmas the various lines of evidence for the removal of gold from magma by the separation of vapor crystalline and immiscible melt phases indicate that fresh volcanic rocks provide only minimum limits on magmatic gold concentrations in most cases magmatic values will be much higher elevated gold contents 0 3 to 1 0 ppm of some porphyry deposits suggest the existence of salic magmas containing gold in concentrations appreciably greater than the 1 2 ppb concentrations of basalts

genesis of middle miocene yellowstone hotspot related bonanza epithermal au ag deposits northern great basin usa epithermal deposits with bonanza au ag veins in the northern great basin ngb are spatially and temporally associated with middle miocene bimodal volcanism that was related to a mantle plume that has now migrated to the yellowstone national park area the au ag deposits formed between 16 5 and 14 ma but exhibit different mineralogical compositions the latter due to the nature of the country rocks hosting the deposits where host rocks were primarily of meta sedimentary or granitic origin adularia rich gold mineralization formed where glassy rhyolitic country rocks host veins colloidal silica textures and precious metal colloid aggregation textures resulted where basalts are the country rocks clay rich mineralization with silica minerals adularia and carbonate developed oxygen isotope data from quartz originally amorphous silica and gels from super high grade banded ores from the sleeper deposit show that ore forming solutions had 18o values up to 10 heavier than mid miocene meteoric water the geochemical signature of the ores including their se rich nature is interpreted here to reflect a mantle source for the epithermal suite elements au ag se te as sb hg and that signature is preserved to shallow crustal levels because of the similar volatility and aqueous geochemical behavior of the epithermal suite elements a mantle source for the gold in the deposits is further supported by the pb isotopic signature of the gold ores apparently the host rocks control the mineralization style and gangue mineralogy of ores however all deposits are considered to have derived precious metals and metalloids from mafic magmas related to the initial emergence of the yellowstone hotspot basalt derived volatiles and metal loid s are inferred to have been absorbed by meteoric water dominated geothermal systems heated by shallow rhyolitic magma chambers episodic discharge of volatiles and metal loid s from deep basaltic magmas mixed with heated meteoric water to create precious metal ore forming fluids colloidal nanoparticles of au ag alloy electrum naumannite ag2se silica and adularia likely nucleated at depth traveled upward and deposited where they grew large enough to aggregate along vein walls silica and gold colloids have been reported in hot springs from yellowstone national park suggesting that such processes may continue to some extent to the present however it is possible that the initial development of the mantle plume led to a major but short lived distillation process which led to the mid miocene bonanza ore forming event

the evolution of a porphyry cu au deposit based on la icp ms analysis of fluid inclusions bajo de la alumbrera argentina the chemical and physical evolution of magmatic to hydrothermal processes in the porphyry cu au deposit of bajo de la alumbrera northwestern argentina has been reconstructed with a quantitative fluid inclusion study fluid inclusion petrography microthermometry and single inclusion microanalysis by excimer laser ablation inductively coupled plasma mass spectrometry la icp ms are combined to determine the evolution of pressure temperature and ore metal concentrations including cu and au in the fluids complementary hydrogen and oxygen isotope analyses are used to further constrain the water sources in the evolving system the combined data provide a new level of insight into the mechanisms of metal sourcing and ore mineral precipitation in a porphyry style magmatic hydrothermal system based on previously reported observations of the igneous geology alteration geochemistry and veining history of the subvolcanic porphyries at alumbrera the distribution of fluid inclusion types in space and time is documented six major inclusion types are distinguished the highest temperature brine inclusions up to 750 c p 1 kbar are mainly recorded in barren quartz magnetite veins in the core of the alteration system these polyphase brine inclusions halite sylvite multiple opaque and transparent daughter crystals are interpreted as the most primitive magmatic fluid recorded at the level of the deposit they are of moderately high salinity 50 60 wt nacl equiv dominated by nacl kcl and fecl 2 and contain on average 0 33 wt percent cu and 0 55 ppm au upon cooling and decompression these saline liquids exsolve a vapor phase which is preferentially enriched in cu relative to its main salt components but probably plays a minor role in the formation of this particular deposit because of the inferred small mass fraction of vapor cooling and decompression from the highest initial p t conditions down to about 450 c causes magnetite k silicate alteration but no saturation in au or cu sulfides as recorded by continually high ore metal concentrations in the fluid inclusions coprecipitation of cu and au as chalcopyrite and native gold some early bornite occurs over a narrow range of decreasing fluid temperature with cooling from 400 to 305 c the cu concentration in the brine drops by about one order of magnitude to less than 0 07 wt percent without a proportional decrease in major salt components ore mineral precipitation extracts 85 percent of the cu and au from the fluid it is associated with potassic alteration as shown by a concomitant decrease in the k na ratio of the cooling magmatic brine and by an increase in its ba and sr concentrations elements which are probably liberated in the destruction of calcic igneous minerals the fluid chemical data demonstrate that the metal ratios in this and probably many other porphyry style ore deposits are primarily controlled by the magmatic source of the ore brines on the other hand the final hypogene ore grade of the deposit is controlled by the efficiency of ore mineral precipitation at alumbrera metal extraction is governed by the efficiency of cooling a high flux of magmatic fluid within a small rock volume dilution of residual magmatic fluids as recorded by aqueous fluid inclusions of decreasing salinities and temperatures below 295 c follows after the main stage of copper introduction and is associated with feldspar destructive phyllic alteration geometric relationships fluid analyses and stable isotope data together indicate that phyllic alteration results from postmineralization hydrothermal activity involving minor mixing between meteoric water residual brine and a waning input of magmatic vapor

characteristics of coal mining microseismic and blasting signals at qianqiu coal mine the signal waveforms caused by blasting events which are similar to the microseismic ms signal waveforms caused by mining activities are very common during the ms monitoring at coal mines however these blasting signals are not useful for monitoring and early warning of the coal or rock dynamic disasters by ms monitoring technique to distinguish between the coal mining ms signals and the blasting signals we studied the differences between these waveforms by analyzing the dominant frequency signal duration following peak attenuation and multifractal parameters and f the main results are the coal mining ms signals have lower dominant frequency below 80 hz and longer vibration duration more than 2 s than the blasting signals dominant frequency above 80 hz and duration less than 2 s the following peak envelope curves of the two types of signals fit a power function moreover the power exponent and fitting accuracy were obtained to describe the attenuated speed and stabilities of the ms signals the coal mining ms signals attenuate slower and the coda waves are more complex than the blasting signals the dividing line of the power exponent between the mining ms and the blasting signals is 8 according to the multifractal theory the mining ms signals have smaller spectral width below 1 2 and f below 0 3 than the blasting signals above 1 2 and f above 0 3 the research results lay a foundation for the automatic identification of mining ms signals and blasting signals recorded in coal mines

different bedding loaded coal mechanics properties and acoustic emission using taw 2000kn electro hydraulic servo rock press machines and the american physical acoustics company s sh ii acoustic emission systems experimental studies began to address the mechanical properties in different beddings of loaded coal and the related acoustic emission characteristics established based on the acoustic emission damage model and verify the model the results show that the mechanical properties of different coal sample beddings are distinctive with maximum uniaxial compressive strength and elastic modulus of vertical stratification of coal samples and the minimum poisson s ratio thus the minimum uniaxial compressive strength and elastic modulus of oblique bedding coal samples along with the maximum poisson s ratio in the processes of loading result in different bedding coal samples having different stress strain curves especially when different bedding coal samples experience the stages of fissure compression elastic deformation plastic deformation and instability and destruction in addition the displacement proportions of each stage of the loading process have relatively obvious differences the loading times of vertical parallel and oblique bedding coal are 495 382 and 331 s respectively and their acoustic emission mutation points of peak stress are approximately 60 41 and 33 respectively thus we can use the mutation point as precursor information to estimate the damage intensity in different bedding seams the theoretical and experimental stress strain curves obtained by the coal damage model are basically identical verifying the reliability of the model and reflecting the feasibility of acoustic emission technology in the study of coal damage the results can effectively forecast coal and gas outburst hazard in coal mines especially highly gassy and outburst mines it can also make comprehensive predictions for flooding accidents roof fall accidents and other disasters and provide valuable evacuation time for underground coal mine workers the results are of great scientific significance in safeguarding the safety of coal mines

mineralogy and mineral chemistry of the metamorphosed and precious metal bearing ming deposit canada abstract the ming deposit in the northwestern canadian appalachians is a metamorphosed bimodal mafic precious metal au ag bearing and cu rich volcanogenic massive sulfide vms deposit consisting of several spatially proximal lenses in a sericite to chlorite altered rhyodacitic footwall the various lenses 1807 zone 1806 zone ming south up plunge ming south down plunge and the lower footwall zone have variations in cu au ag and zn grades that reflect varying physico chemical conditions of ore formation this study describes the complex ore mineralogy of the orebodies and constrains the genesis of the deposit using field methods mineralogy whole rock sulfide geochemistry and micro analytical methods the orebodies are predominantly pyrite chalcopyrite with lesser sphalerite pyrrhotite and trace galena and arsenopyrite with the exception of the lower footwall zone which consists of a high temperature 320 c chalcopyrite pyrrhotite pyrite cubanite assemblage the other orebodies 1806 1807 ming south up plunge and down plunge contain trace amounts of tellurides hessite altaite tsumoite unnamed bismuthtelluride sulfosalts ag poor and ag rich tennantite tetrahedrite meneghinite agsb phases stannite and precious metal phases electrum aghg au alloys the 1807 zone is enriched in te bi and se whereas the 1806 zone is telluride free and contains as sb hg au and ag mineral chemistry of sphalerite shows strong variations in fe content 1 12 11 04 wt intermediate fe 4 33 6 33 wt fe and fe rich 7 327 11 04 wt fe sphalerite are common in all orebodies whereas fe poor sphalerite 1 12 3 57 wt fe occurs exclusively in the 1807 and 1806 zones tennantite tetrahedrite is typically ag poor 0 25 2 19 wt in the 1807 zone but is significantly enriched in ag up to 29 3 wt in the 1806 zone galena in the 1807 zone and ming south orebodies is commonly myrmekitically intergrown with tellurides and has high concentrations of te bi se and ag in contrast galena in the 1806 zone is less enriched in te bi and se but high in ag variations in mineralogy epithermal elements as bi hg sb se sn te and precious metal ag au content and mineral chemistry between the different orebodies indicate that they were formed from predominantly reduced acidic hydrothermal fluids with varying te2 s2 se2 s2 and mbi msb ratios as temperatures steadily decreased from 300 c to

early yellowstone hotspot magmatism and gold metallogeny abstract high grade epithermal gold deposits in the northern great basin have long been associated with regional miocene basaltic to rhyolitic volcanism previous models for the low sulfidation epithermal gold ores in this region have generally portrayed the bimodal magmas as a source of heat to drive large scale convection of meteoritic water that leached gold from crustal sources and deposited it in hydrothermal vein systems or required that the gold evolve from fractionated silicic magmas new data of the present study indicate a more direct genetic link to the plume related basaltic magmas of the region laser 40ar 39ar incremental heating plateau ages for single crystals of adularia from several of these low sulfidation epithermal gold deposits range from 16 6 ma to 15 5 ma adularia from the jumbo deposit yields three concordant plateau ages with a combined statistical result of 16 54 0 04 ma 95 confidence level mswd 0 23 plateau ages for adularia from other deposits in the region and from gold bearing veins in the owyhee mountains of southwestern idaho yield similar ages up to 16 5 ma however some veins are as young as ca 15 5 ma and the grain to grain ages for a given sample can vary by up to ca 0 5 ma observed variations in age among the adularia crystals of a given rock sample indicate varying amounts of extraneous argon and also loss of radiogenic 40ar among the population of grains for a particular sample the single crystal results are interpreted to indicate a 16 5 15 5 ma interval for formation of gold bearing adularia veins in the region the initiation and duration of this gold forming event appears contemporaneous within uncertainties with the basaltic volcanism at the steens mountain section and an ensuing one million year episode of basaltic volcanism from multiple centers in the region brueseke et al 2007 trace amounts of lead are alloyed with gold in the deposits studied the isotopic compositions of this lead are not compatible with regional crustal units that host the gold ores or the silicic igneous lithologies of the region but have the same lead isotopic composition as basalts of the earliest yellowstone plume represented by the earliest lavas of the columbia river basalt province the steens basalts and stonyford volcanic complex hanan et al 2008 we propose that the gold studied and its traces of alloyed lead were derived together from the mantle released from basaltic magma chambers of the province and carried by low density fluids into shallow geothermal systems during the earliest stages of yellowstone hotspot magmatism

early cretaceous bimodal magmatism related epithermal mineralization a case study of the gaosongshan gold deposit in the northern lesser xing an range ne china abstract low sulfidation ls gold mineralization is partially associated with bimodal volcanism in origin sources of ore mineralized fluids and relevant dynamic processes remain poorly understood to better understand these issues a study including deposit geology petrology zircon u pb dating and element and sr nd hf isotope geochemistry of bimodal volcanic rocks at gaosongshan was conducted the bimodal volcanic rocks are composed of andesitic rocks basalt andesite andesite trachyandesite andesitic pyroclastic of the meifeng formation and overlying rhyolite lava of the fuminhe formation cut by equivalent porphyry stocks which contain pyrite bearing granular textured quartz cavity with a sugary appearance with trapped single phase magmatic fluids the andesitic suite formed at approximately 106 108 ma prior to eruption of the younger rhyolitic magmas 105 6 1 7 ma n 13 mswd 1 2 the andesites show calc alkaline affinities which is a subduction related characteristic and show moderate la ybn 7 91 11 36 and weakly negative europium anomalies 0 80 1 02 indicating a source in the asthenospheric mantle with varying contamination by both subduction and continental materials a type rhyolitic rocks are geochemically comparable to the andesitic suite and their higher la ybn 13 01 30 05 and lower eu eu 0 66 0 73 indicate evolved products of andesitic magmas the estimated oxygen fugacity of dry 1 2 water rhyolite lava is fmq 1 87 whereas rhyolite porphyry is more oxidized fmq 0 12 and water rich 2 5 2 8 with probably being water saturated at 2 0 2 4 km depths therefore it is assumed that the essential constraints of bimodal magmatism on epithermal gold mineralization are sequential processes from ascending and gradual differentiation of crustal level mantle derived basaltic magmas to releases of hydrothermal solutions from the silica rich magma reservoir at shallower levels most importantly the oxygen fugacity of and the fluid fluxes from dry rhyolitic melts are critical restricting parameters for the limited reserves at gaosongshan thus this research contributes objective evidence for investigations of deposit genesis and prospecting targets

ore mineralogy of the applachian caledonian stratabound sulfide deposits abstract the diverse ore mineralogies of more than 100 stratabound sulfide deposits that occur along the length of the appalachian caledonian orogen have been tabulated the minerals reflect the varying cu zn pb ratios that have been used as a means to separate the ore deposits into six distinct types following the igcp project 60 guidelines the ore deposits each containing at least one million metric tons of ore are typical of massive sulfide deposits throughout the world and provide a basis for contrasting and comparing this orogen with others differing grades of metamorphism have significantly modified the ore mineral grain sizes and textures but do not seem to have effectively influenced the number or variety of mineral species present

fractural structure of thick hard roof stratum using long beam theory and numerical modeling the thick hard rock thr roof of the long wall mining face is prone to the large sized cantilever roof and its sudden fracture will cause serious rock dynamic disasters such as coal and gas outburst and rockburst in this study based on the long beam theory the initial fracture mechanical model for thr was established and the first weighting characteristics and extreme fracture step distance were calculated this study introduced a new technology called deep hole pre splitting blasting dpb which could break the thr by drilling holes with different depths and angles at different levels of roof rock and then blasting it field measurement analysis indicated that the immediate roof and lower thick hard strata were fully collapsed to fill the goaf and the upper thick hard stratum was effectively cut off the results showed that mechanical model and drilling holes method and dpb technique were so notably that would lead to a foundation for large scale popularization and application in a chinese mine

tellurides associated with volcanogenic massive sulfide vms mineralization at yuinmery and austin western australia tellurides have been identified in vms mineralization at yuinmery and austin in the archean youanmi terrane yilgarn craton western australia tellurides identified at yuinmery include petzite stutzite hessite tellurobismuthite altaite rucklidgeite melonite mattagamite and a nickel cobalt telluride with chemical composition similar to cobaltian melonite which has previously only been reported once before tellurides and related minerals identified at austin include stutzite volynskite tellurobismuthite tetradymite tsumoite rucklidgeite altaite and a mineral with the formula bi pb 3 te se s 4 corresponding to the rare mineral poubaite the tellurides are interpreted to have been deposited with the base metals on and immediately below the sea floor by very hot fluids during a period of quiescence in the volcanism the mineral assemblage suggests that the fluids in both areas had high te2 and were oxidising but close to the pyrrhotite pyrite boundary the presence of ni and co tellurides at yuinmery but not at austin is probably due to the derivation of the fluids at yuinmery from mafic volcanism whereas at austin the succession is dominantly felsic the metamorphic grade at austin is higher than that at yuinmery and this may have resulted in some re crystallization of tellurides and tellurosulfides

gold recycling and enrichment beneath volcanoes a case study of tolbachik kamchatka magmas supply metals to hydrothermal ore deposits although typical arc basalts may be unable to produce a gold rich ore forming fluid as such basalts rarely exceed 5 ppb au consistent with this the occurrence of native gold of magmatic origin is extremely rare and only a few finds of micron sized gold particles in unaltered basalts have been documented surprisingly some lava flows and scoria cones of the historic basaltic eruptions of tolbachik volcano kamchatka are unusually gold rich tolbachik basalts contain up to 11 6 ppb au based on whole rock analyses nuggets of gold electrum up to 900 m in size and native gold droplets up to 200 m plus numerous vapor deposited gold crystals within fumarolic incrustations and directly on surfaces of basaltic lapilli our results demonstrate that the gold nuggets in tolbachik basalt are of hydrothermal origin and were physically scavenged from epithermal veins hosted by country rocks during intrusion of mafic magmas depending on the melt temperature and or time span of the melt rock interaction gold was ejected by the erupting volcano either in the form of abraded nuggets or liquid droplets or was fully assimilated dissolved into the shallow long lived magma chamber to provide a 4 fold increase in gold content over background concentration of 2 7 ppb au characteristic of mafic volcanic rocks in kamchatka upon the end of the eruption the continued discharge of volcanic vapors enriched in gold deposited abundant crystals of gold on cooling lava and scoria similar to tolbachik recycling of metals from prior accumulations ore deposits in the shallow crust may take place in other long lived magma reservoirs thus upgrading the gold and other metal contents and contributing to the ore forming potential of a magma

carbon dioxide as a proxy for orogenic gold source abstract despite many decades of study the genesis of orogenic gold deposits remains in debate one aspect of this debate concerns the origin of the mineralising fluids two important constraints are that the fluids are sulphur and co2 bearing and that high fluid fluxes are maintained in a spatially localised environment for a relatively short period of time whereas crustal metamorphism decarbonation operates over many millions of years the source is not localised and is of regional extent in this paper we explore the devolatilization of a subducting slab material using coupled petrological thermo mechanical numerical approach that takes into account dehydration and decarbonation processes recent phase equilibria calculations show that decarbonisation of the slab requires much higher temperatures that normally occurs within subduction zones and the devolatilization site in the slab is spatially and temporally localised during slab roll back or within a hot orogen when the slab material is incorporated into the overriding plate we also investigate the plausibility of large gold sources in the collisional and back arc environments

ion microprobe analysis of feti oxides optimization for the determination of invisible gold magnetite is a common mineral in a wide variety of hydrothermal au bearing ore deposit types feti oxides also occur as phenocrysts in some au bearing silicic volcanic rocks in oxidized plutons or reduced plutons that are undersaturated with respect to sulfide feti oxides likely are an important host of au to evaluate the volumetric importance of magnetite and ilmenite as hosts for au in igneous rocks and hydrothermal ore deposits it is necessary to quantify au in feti oxide minerals we used secondary ion mass spectrometry sims to analyze magnetite and ilmenite standards implanted with 197 au samples were sputtered with a cs primary beam and negative secondary ions were measured because of the small diameter of oxide phenocrysts in volcanic rocks small raster size and beam diameter are required we used a 10 m diam beam rastered over an area with 50 m sides to obtain sufficient background counts and optimum dynamic range 197 au counts were measured for up to 5 s per cycle we obtained measured detection limits mdl of 10 ppb au in magnetite and 240 ppb au in ilmenite operating in high mass resolution hmr mode m m 4 000 to 5 000 hmr mode was required to eliminate an interference with 133 cs 48 ti 16 o during analysis of ilmenite the high mdl for ilmenite was due to the high inherent au content of the unimplanted standard the siting of au has important implications for both ore genesis and ore extraction quantification of au in feti oxides may lead to more accurate mineralogical balances for hydrothermal au deposits as well as resolving questions regarding the partitioning of au in silicic magmas and the behavior of au in some magmatic hydrothermal ore forming systems