trace and minor elements in galena a reconnaissance la icp ms study minor and trace elements can substitute into the crystal lattice of galena at various concentrations in situ la icp ms analysis and trace element mapping of a range of galena specimens from different deposit types are used to obtain minor trace element data aimed at achieving insight into factors that control minor trace element partitioning the previously recognized coupled substitution ag bi sb 3 2pb2 is confirmed however the poorer correlation between ag and bi sb when the latter elements are present at high concentrations 2000 ppm suggests that site vacancies may come into play 2 bi sb 3 3pb2 galena is the primary host of tl in all mapped mineral assemblages along with cu tl is likely incorporated into galena via the coupled substitution ag cu tl bi sb 3 2pb2 tin can reach significant concentrations in galena 500 ppm cd and minor hg can be incorporated into galena the simple isovalent substitution cd hg 2 pb2 is inferred this paper shows for the first time oscillatory and sector compositional zoning of minor trace elements ag sb bi se te tl in galena from two epithermal ores zoning is attributed to slow crystal growth into open spaces within the vein at relatively low temperatures the present data show that galena can host a broader range of elements than previously recognized for many measured elements the data sets generated display predictable partitioning patterns between galena and coexisting minerals which may be dependent on temperature or other factors trace element concentrations in galena and their grain scale distributions may also have potential in the identification of spatial and or temporal trends within individual metallogenic belts and as markers of ore formation processes in deposits that have undergone superimposed metamorphism and deformation galena trace element geochemistry may also display potential to be used as a trace minor element vector approach in mineral exploration notably for recognition of proximal to distal trends within a given ore system

textural control on gold distribution in as free pyrite from the dongping huangtuliang and hougou gold deposits north china craton hebei province china article i nfo pyrite from the dongping huangtuliang and hougou gold deposits hebei province china was investigated using a combination of ore microscopy including back scattered imaging and in situ laser ablation inductively coupled plasma mass spectroscopy la icp ms a range of elements including au te ag pb bi cu co ni and as was analyzed with the aim to constrain the textural controls and influence of superimposed deformation on the distribution of invisible gold in as free pyrite thedatasetshowsexcellentcorrespondence betweenmeasuredhighgoldvaluesandthreekeytexturalcriteria i areasofclusteredtellurideinclusions especiallyindongping ii microshearingandfracturing brecciation dongping and huangtuliang and iii pyrite recrystallization huangtuliang invisible gold is only at trace levels in the hougou and gold bearing telluride minerals are not observed this is considered to result from larger scale remobilization of gold during advanced brecciation and recrystallization of pyrite pyrite grains containing clustered inclusions have by far the highest gold concentrations up to 1 wt with consistent values of thousands of ppm au interpretation of textures and la icp ms data infers that in these areas the distribution of telluride inclusions extends pervasively from micron to nanoscale i e as fields of nanoparticles local employment of coupled dissolution reprecipitation reaction between pyrite and fluids driving the k metasomatic alteration dated at 150 ma is invoked to explain such patterns syn deformational grain scale mobilization of gold and other elements took place leading to a portion of the gold being recrystallized within fractures and microshears the deformational event leads to gold enrichment in the huangtuliang pyrite where brittle fracturing brecciation has been followed by a resorption and recrystallization in the latter case foam textured pyrites again without as can contain up to hundreds of ppm gold theinterpreted sequenceof pyritepost depositional eventsis inaccordancewith the protracted magmaticevolution of the area starting with variscan alkaline intrusions 390 ma and reactivated during the yanshanian orogeny 150 ma thestudyshows i thatas freepyritecanreadilycontainsignificantamountsofinvisiblegold bothasnanoparticles

focused ion beam fib combined with sem and tem advanced analytical tools for studies of chemical composition microstructure and crystal structure in geomaterials on a nanometre scale abstract in order to make meaningful interpretations of trace element and isotopic information from geomaterials prior characterization of the material of interest with respect to structural and chemical homogeneity radiation damage and microstructure is often required transmission electron microscopy tem is a powerful analytical tool that may be used to fully characterise a wide range of synthetic and natural materials the focused ion beam technique fib is an ideal tool for tem sample preparation that allows for the fabrication of electron transparent foils with typical dimensions of 15 10 0 150 m from any region of interest i e site specific and in virtually any material fib sample preparation consumes only a small volume of material approximately 2300 m 3 for a standard foil with the dimensions 15 10 0 150 m leaving most of the material essentially unaffected by the sampling process modern tem facilitates the measurement of chemical composition with unsurpassed spatial resolution e g nanometer scale high resolution imaging and electron diffraction provide important complimentary structural information it is the combination of crystal structure information and chemical composition that allows for the complete characterization of the volume of interest high resolution elemental mapping or line scans may be used to acquire complete energy dispersive x ray analysis edx spectra of a material pixel by pixel subsequent evaluation of the data allows for the correlation of the edx spectrum with the respective elemental map or line scan with an image thus illustrating spatially resolved chemical composition variations at the 0 5 1 0 wt level frequently minerals enclose sub micrometer or even nanometre sized inclusions of minerals fluids or silicate melt which are of great interest to geoscientists nanoinclusions e g in diamond or olivine are of particular interest because they may have preserved their original crystal structure thus providing a geobarometer recording the pressure conditions at the time of formation of the inclusion fib tem are appropriate techniques to sample and subsequently define the chemical composition and the structural state of mineral inclusion on the nanometre scale the combination of fib with an sem allows for 3d information to be obtained from samples including 3d imaging e g phase distribution and volume of the individual phases in symplectites 3d distribution of elements in a specific volume 3d elemental maps and three dimensional texture analysis using electron backscatter diffraction ebsd

an overview of the platinum group element nanoparticles in mantle hosted chromite deposits abstract this paper reviews the occurrence of platinum group elements nanoparticles pge nps in mantle hosted chromite deposits showing that pge nps are more frequently found in these deposits than previously thought a comparison of published experimental data with observations in natural samples reveal that pge nps might form at the pressure 1 0 5 gpa temperature 1200 c and f o 2 fmq 1 conditions in which chromite deposits form in the upper mantle the crystallization of pge nps may take place earlier or simultaneously to the segregation of chromite and or sulfide liquids from silicate melts if the pges are dissolved in the silicate melt the segregation of pge nps could be linked to local changes in f o 2 and f s 2 during the early crystallization of chromite and or olivine mobile crystals of chromite and droplets of sulfide melts entrained in the basaltic parent melt may also play an additional role as physical collectors of pge nps providing a complementary or even an alternative mechanism for the fractionation of pges in high temperature silicate melts furthermore hydrothermal alteration of the chromite deposits during seafloor metamorphism or exhumation i e retrograde metamorphism of upper mantle rocks has also a significant effect on the internal structure of the oxides and sulfides that host the pge nps frequently pge nps are found along the replacement contacts between primary and secondary minerals suggesting that pge nps can also form during low temperature alteration events 200 600 c finally heating events overimposed on chromite deposits previously affected by hydrous metamorphism may enhance fluid infiltration subsequently triggering chemical mineralogical or textural responses in the oxide or sulfide matrices hosting the pge nps promoting coarsening of metal nanoparticles the interplay between these processes can explain the wide spectrum of particle sizes of pge inclusions that are observed in many altered chromite deposits which can vary from a few nanometers to larger than a micron these studies provide evidence that pge nps can eventually form under a wide spectrum of thermal and pressure conditions and show that aqueous fluids may play a relevant role in producing pge nps during metamorphism and metasomatism of mantle hosted chromite deposits

feldspar evolution in the roxby downs granite host to fe oxide cu au u mineralisation at olympic dam south australia abstract the textural relationships and geochemistry of feldspars from least altered to sericite hematite altered and mineralised 1 595 ga roxby downs granite rdg at olympic dam south australia were examined the sample suite is representative of rdg both distal 5 km and proximal 27 34 is recognised along with a more abundant less calcic plagioclase an 12 20 both displaying rapakivi and anti rapakivi textures with alkali feldspar alkali feldspars or 55 ab 43 an 2 record post magmatic evolution from cryptoperthite to patch perthite subsequent patch perthite is overprinted by highly porous near end member albite and k feldspar while plagioclase undergoes replacement by albite sericite ba rich k feldspar in sericite hematite altered and mineralised rdg along the margin of the odbc sericite replaces all plagioclase whereas red stained fe rich k feldspar persists sulphide uranium rare earth element mineralisation is observed in association with hydrothermal feldspars and increases in abundance with proximity to the orebody petrographic observations and whole rock geochemistry illustrate the transformation of plagioclase and alkali feldspar from igneous to hydrothermal processes and indicate that hydrothermal albite and k feldspar formed within the rdg without the need for an external source of alkalis feldspar geothermometry indicates a minimum crystallisation temperature of 765 c at 2 2 kbar for alkali feldspar pressure estimate obtained using plagioclase amphibole geobarometry followed by a range of lower temperature transformations late stage magma mixing contamination is postulated from supportive temperature and pressure estimates along with feldspar and mafic mineral relationships

plastic deformation of metamorphic pyrite new evidence from electron backscatter diffraction and forescatter orientation contrast imaging application of new scanning electron microscope techniques to the study of deformed metamorphic pyrite reveals evidence for plastic deformation not readily recognised by more traditional methods specifically use of forescatter solid state detectors in conjunction with tilted polished specimens of pyritic ore produces high quality crystallographic orientation contrast images which map the distribution of deformation domains within grains use of electron backscatter diffraction allows quantification of the crystallographic misorientations shown by the orientation contrast images combination of these techniques shows that the pyrite studied deforms by slip on 100 and more rarely 110 systems slip is often associated with distributed rotation of up to 20 about and more rarely axes pyrites may have simple histories involving rotation about a single axis or more complex histories involving rotation about different axes and more rarely in different domains of the same pyrite grain or sequential rotations about quite different systems typically distributed rotation about followed by discrete rotation about a non crystallographic axis

nano mineralogy and geochemistry of high grade diasporic karst type bauxite from parnassos ghiona mines greece abstract in the present work a combination of various techniques is utilized for the study of nano mineralogy and geochemistry of high grade karst type bauxite al rich and fe depleted samples al2o3 ca 80 wt from the parnassos ghiona mines located in greece initial characterization using pxrd and electron microscopy in microscale and mesoscale sem eds including stem mode proved the presence of fe cr ti containing diaspore anatase and minor rutile the study by means of 57fe mossbauer spectroscopy in correlation with magnetic susceptibility measurements and complemented with synchrotron based spectroscopies at the microscale sr micro xrf and micro xanes exafs indicated that fe3 in contrast to 6 cr3 is not exclusively a component of the diaspore structure while cr3 substitutes al3 in octahedral sites of diaspore 6 cr3 6 al3 the electron microscopy in nanoscale tem eds eels revealed that fe exists in the form of peculiar fe3 bearing nanominerals most likely maghemite type phases between 25 and 45 nm in size in addition to the fe3 ions substituting al3 in the diaspore structure moreover it was proven that tio2 polymorph mineral nanoparticles particularly rounded anatase mesocrystals and nanocrystals and individual needle shaped rutiles are dispersed into the diaspore matrix thus diaspore in the studied bauxite concerns in fact a distinct fe3 cr3 alooh low t authigenic phase demonstrated for the first time in literature on the other hand the observed tio2 mineral nanoparticles formed together with diaspore during diagenesis and fe nanominerals formed during epigenesis were hitherto unknown not only for the allochthonous karst type bauxite deposits of greece but also for the overall bauxite deposits worldwide

pyrite deformation textures in the massive sulfide ore deposits of the norwegian caledonides abstract the norwegian caledonides represent a belt of late precambrian to early palaeozoic rocks emplaced as a series of nappes onto the fennoscandian basement massive sulfide orebodies occur along virtually the whole length of the orogenic belt making it possible to study deposits of a similar origin chemistry and mineralogy but variably deformed at different metamorphic conditions samples from seven pyrite rich ore deposits deformed at temperatures from 320 c to 610 c have been investigated using reflected light petrographic observation orientation contrast oc imaging and electron backscatter diffraction ebsd while a range of brittle annealment and growth textures are preserved in the deposits all preserve evidence for lattice misorientation and low angle 2 sub grain boundary development indicative of dislocation creep these results are at odds with those implied from the published pyrite deformation mechanism map which suggest that pyrite does not deform by plastic mechanisms at natural geological strain rates and that the brittle ductile transition is at 425 c our results imply that pyrite is more ductile than generally inferred and the current deformation mechanism map needs to be revised with plastic deformation mechanisms operating at a much wider range of temperature and strain rate conditions

ore minerals down to the nanoscale cu fe sulphides from the iron oxide copper gold deposit at olympic dam south australia abstract cu fe sulphide mineral assemblages from the olympic dam od fe oxide cu u au ag deposit south australia are studied down to the nanoscale to explore the potential these minerals have for understanding genetic processes such as primary deposit zonation cu fe sulphide pairs brown bornite associated with chalcopyrite bornite chalcopyrite zone and symplectites of purple bornite with species from the chalcocite group cu2 xs bornite chalcocite zone co define an upwards and inwards deposit scale zonation at od in the bornite chalcocite zone there is also an increase in the proportion of chalcocite relative to bornite within the symplectites towards upper levels in this case two phase cu2 xs assemblages are also present as anisotropic hexagonal chalcocite cch with lamellar exsolutions of digenite distinguishable at the m scale using compositional data electron microprobe combined with transmission electron microscopy tem study of foils prepared in situ via focused ion beam fib sem we show that cu fe sulphides from different ore zones feature nanoscale intergrowths lattice defects superstructure domains na and antiphase boundary domains apbs that can be interpreted as due to exsolution coarsening and phase transformation during cooling from high t solid solutions in the system cu fe s and sub systems according to published phase diagrams brown bornite cu fe s 5 contains pervasive lamellae of chalcopyrite which extend down to the nanoscale such specimens appear homogeneous at the m scale purple bornite cu fe s 300 c high t phases cu poor digenite followed by cooling along distinct paths down to

comparison of snow mass estimates from a prototype passive microwave snow algorithm a revised algorithm and a snow depth climatology abstract while it is recognized that no single snow algorithm is capable of producing accurate global estimates of snow depth for research purposes it is useful to test an algorithrn s performance in different climatic areas in order to see how it responds to a variety of snow conditions this study is one of the first to develop separate passive microwave snow algorithms for north america and eurasia by including parameters that consider the effects of variations in forest cover and crystal size on microwave brightness temperature a new algorithm gsfc 1996 is compared to a prototype algorithm chang et al 1987 and to a snow depth climatology sdc which for this study is considered to be a standard reference or baseline it is shown that the gsfc 1996 algorithm compares much more favorably to the sdc than does the chang et al 1987 algorithm for example in north america in february there is a 15 difference between the gsfc 1996 algorithm and the sdc but with the chang et al 1987 algorithm the difference is greater than 50 in eurasia also in february there is only a 1 3 difference between the gsfc 1996 algorith rn and the sdc whereas with the chang et al 1987 algorithm the difference is about 20 as expected differences tend to be less when the snow cover extent is greater particularly for eurasia the gsfc 1996 algorithln performs better in north america in each month than does the chang et al 1987 algorithm this is also the case in eurasia except in april and may when the chang et al 1987 algorithm is in closer accord to the sdc than is the gsfc 1996 algorithm

trace element substitution and grain scale compositional heterogeneity in enargite abstract enargite cu3ass4 is a relatively common sulphide mineral and is considered diagnostic for deposits of intermediate to high sulphidation type analysis of enargite bearing samples from deposits in the zijinshan porphyry high sulphidation epithermal cu au orefield southeastern china provides evidence for the diversity of trace elements that may be hosted within enargite and their range of concentrations enargite is shown to host sb te sn zn and ge at concentrations up to several thousand ppm the mineral also incorporates measurable concentrations of mo cd bi pb fe se ag au w ga and in element mapping electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry provides evidence for grain scale heterogeneity in enargite in the form of oscillatory grain scale compositional zonation with respect to sb sn te and several other trace elements element mapping also clearly shows an inverse correlation between the concentrations of as and te and between as and sn incorporation of sn and te into the enargite structure is achieved by substitution of sn4 and te4 for as5 charge balance is maintained by incorporation of fe2 zn2 and other divalent cations potentially including cu2 into the cu site the complex intra grain zoning results from evolving fluids multiple phases of growth in turn leading to an overprinting of primary distribution patterns observed patterns are also influenced by equilibrium partitioning between enargite and co existing minerals nevertheless trace element signatures in enargite from different parts of the zijinshan ore system show notable differences enargite from the high sulphidation stage typically shows a marked enrichment in te and sn whereas enargite from intermediate sulphidation stage is relatively depleted in te and sn and comparatively enriched in sb and se these differences represent a potential vector for exploration within porphyry high sulphidation epithermal systems furthermore the presence of te rich enargite may be a prospective guide to high au grade mineralization the notable concentrations of precious metals au ag and critical elements notably te and ge within enargite make this mineral of particular interest from the perspective of potential recovery of these economically important elements the observed grain scale zoning and inherent variability within any given sample emphasize that spot analysis of trace elements alone without consideration of such heterogeneity may provide quantitative data of limited use and potentially lead to misleading interpretations

natural gold nanoparticles abstract the nanoparticulate gold component in ore deposits and exploration samples is yet to be fully realised but new methods of characterisation and analysis access to high grade gold samples and a strong focus on au nanoparticles in the manufacturing sector provide a new impetus to quantify its significance in geology nanoparticles are increasingly recognised as a fundamental step in geochemical reactions a critical component in weathering processes in biomineralisation and metal migration in ore systems the nanoparticulate population of au is a significant factor in the formation of economic deposits as a refractory component locked up in sulphides in secondary supergene enrichments the formation of surface geochemical anomalies and in the formation of high grade accumulations a better understanding and characterisation of this nanoparticulate gold could unlock hidden resources in known deposits through easier beneficiation and processing but also assist in the discovery of new deposits through advanced exploration methods

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

micron to nanoscale characterisation and u pb geochronology of zircon from granites of the samphire pluton south australia abstract zircons from three distinct granites within the samphire pluton south australia are characterised at the micron to nanoscale sensitive high resolution ion microprobe shrimp u pb zircon dating generated 207pb 206pb weighted average ages of 1586 9 3 ma 1583 2 8 5 ma and 1578 9 5 ma respectively although zircons from all three granites display evidence of hydrothermal overprinting this is most strongly expressed in a distinct red colored granite referred to here as granite c alteration is expressed as variation in the concentrations of hree y th and pb whereby grain margins are relatively enriched in these elements and both zr and si are depleted altered zircon cores have high u contents relative to grain margins which are appreciably poorer in this element whereas th is strongly enriched within crosscutting microfractures coupled with the relative enrichment in non formula elements and marked disturbance of u th pb isotope ratios the nanoscale observations of pb bearing nanoparticles galena implying mobility of pb and other elements nanofractures and structural defects demonstrate that zircon in granite c has undergone multi stage alteration impacting upon accurate dating importantly and with implications for analogous systems elsewhere our results confirm nanoscale open system u pb behaviour in hiltaba suite zircon shrimp u pb zircon geochronology cannot confidently resolve any statistical differences in the age of the three granites despite their distinct appearance suggesting they might represent temporally distinct phases of a larger magmatic system zircons within the most altered granite c directly underlying the blackbush uranium prospect contain convincing micron to nanoscale evidence for an alteration event that triggered a remobilisation of uranium from granite into the cover sequence

uraninite from the olympic dam iocg u ag deposit linking textural and compositional variation to temporal evolution the olympic dam iocg u ag deposit south australia the world s largest known uranium u resource contains three main u minerals uraninite coffinite and brannerite four main classes of uraninite have been identified uraninite occurring as single grains is characterized by high pb and ree y rey but based on textures can be classified into three of these classes typically present in the same sample primary uraninite class 1 is smallest 10 50 m displays a cubic euhedral habit and both oscillatory and sectorial zoning zoned uraninite class 2 is coarser sub euhedral and combines different styles of zonation in the same grain cobweb uraninite class 3 is coarser still up to several hundred micrometers has variable hexagonal octagonal morphologies varying degrees of rounding and features rhythmic intergrowths with sulfide minerals in contrast the highest grade u in the deposit is found as micrometer sized grains to aphanitic varieties of uraninite that form larger aggregates up to millimeter and vein fillings massive class 4 and have lower pb and rey but higher ca nanoscale characterization of primary and cobweb uraninite shows these have defect free fluorite structure both contain lattice bound pb rey which for primary uraninite is concentrated within zones and for cobweb uraninite is within high pb rey domains micro fractured low pb rey domains sometimes with different crystal orientation to the high pb rey domains in the same cobweb grain contain nanoscale inclusions of galena cu fe sulfides and rey minerals the observed pb zonation and presence of inclusions indicates solid state trace element mobility during the healing of radiogenic damage and subsequent inclusion nucleation recrystallization during formula 1 driven percolation of cu bearing fluid tetravalent lattice bound radiogenic pb is proposed based on analogous evidence for u bearing zircon calculating the crystal chemical formula to uo2 stoichiometry the sum of cations m is 1 for most classes but the presence of mono di and trivalent elements rey ca etc drive stoichiometry toward hypostoichiometric m o2 x in the absence of measured o and constraints of hypostoichiometric fluorite structure charge balance calculations showing o deficit in the range 0 15 0 36 apfu is compensated by assumption of mixed u oxidation states crystal structural formulas show up to 0 20 apfu pb and 0 25 apfu rey in classes 1 3 while for class 4 these are an order of magnitude less low pb and rey subcategories of classes 2 and 3 are similar to massive uraninite with 0 2 apfu ca other elements si na mn as nb etc show two distinct geochemical trends 1 across classes 1 3 and 2 class 4 whereby low pb rey sub populations of classes 2 and 3 are part of trend 2 for certain elements plots of alteration factor cao sio2 fe2o3 vs pb u suggest two uraninite generations early high pb rey classes 1 3 and late massive class 4 there is evidence of pb loss from diffusion leaching and or recrystallization for classes 2 3 low pb rey domains micro analytical data and petrographic observations reported here including nanoscale characterization of individual uraninite grains support the hypothesis for at least two main uraninite mineralizing events at olympic dam and multiple stages of u dissolution and reprecipitation early crystalline uraninite is only sparsely preserved with the majority of uraninite represented by the massive aphanitic products of post 1590 ma dissolution reprecipitation and possibly addition of uranium into the system coupled dissolution reprecipitation reactions are suggested for early uraninite evolution across classes 1 to 3 the calculated oxidation state u6 u4 u6 of the early and late populations point to different conditions at the time of formation charge compensation for rey rich early fluids rather than auto oxidation of uraninite late uraninites may have formed hydrothermally at lower temperatures t 250 c 1 embed mml math 1 gif

thermal behavior of metal nanoparticles in geologic materials although significant progress has been made in understanding the behavior of natural nanoparticles in earth s critical zone i e surface and near surface environment little is known about nanoparticle stability in higher temperature environments where they are increasingly being found here we report the first direct observations of the thermal behavior of natural nanoparticles at near atomic scale revealing that their thermal stability is dependent on particle size and on the surrounding host mineral native au nanoparticles mean diameter 4 nm incorporated in arsenian pyrite from refractory au ores were observed under the transmission electron microscope during in situ heating to 650 c while isolated au nanoparticles melt with the melting point being a function of size we show that when incorporated in arsenian pyrite au nanoparticles become unstable unless the nanoparticle size distribution coarsens by diffusion driven solid state ostwald ripening this change in nanoparticle stability starts above 370 c setting an upper temperature and size limit for the occurrence of nanoparticulate au in refractory sulfides these findings not only provide new insights into the behavior of nanoparticulate au and other metals during geological processes and throughout their metallurgical recovery from refractory ores but also provide a new tool to define the thermal history of nanoparticle bearing geologic and planetary materials

nanogeoscience in ore systems research principles methods and applications introduction and preface to the special issue martin reich robert m hough artur deditius satoshi utsunomiya cristiana l ciobanu and nigel j cook

uranium bearing hematite from the olympic dam cu u au deposit south australia a geochemical tracer and reconnaissance pb pb geochronometer abstract uranium bearing hematite containing up to several wt u also containing al mo w and radiogenic pb is described from olympic dam south australia these elements are present in grains that display both oscillatory zonation and porous structures laser ablation inductively coupled mass spectrometry la icp ms element mapping confirms oscillatory and sectorial zoned domains in hematite grains are enriched in 238u and 206pb and are distinct from those of w and mo the crystal structure and absence of inclusions within zoned hematite was assessed by transmission electron microscopy on foils obtained by in situ slicing across zonation patterns using the scanning electron microscope focused ion beam technique satellite reflections on the electron diffraction patterns obtained from banded zones in hematite are attributable to long range superstructure ordering that is inferred to assist metal incorporation via the substitution 2fe3 me6 vacancy where me u w mo the suitability of u bearing hematite for pb pb geochronology as a first pass was tested on both zoned and porous hematite grains via la icp ms using the gj 1 zircon as the primary external standard only pb pb ages were considered and resulted in 207pb 206pb ages of 1590 8 ma and 1577 5 ma for oscillatory and sector zoned hematite from two samples although reconnaissance in nature these ages potentially support the supposition that mineralization is coeval with emplacement of the gawler range volcanics and associated hiltaba intrusive suite the geochronological application utilizing an abundant refractory mineral represents a new tool for dating iron bearing ores

nanogeochemistry of hydrothermal magnetite magnetite from hydrothermal ore deposits can contain up to tens of thousands of parts per million ppm of elements such as ti si v al ca mg na which tend to either structurally incorporate into growth and sector zones or form mineral micro to nano sized particles here we report micro to nano structural and chemical data of hydrothermal magnetite from the los colorados iron oxide apatite deposit in chile where magnetite displays both types of trace element incorporation three generations of magnetites x z were identified with concentrations of minor and trace elements that vary significantly sio2 from below detection limit bdl to 3 1 wt al2o3 0 3 2 3 wt cao bdl 0 9 wt mgo 0 02 2 5 wt tio2 0 1 0 4 wt mno 0 04 0 2 wt na2o bdl 0 4 wt and k2o bdl 0 4 wt an exception is v2o3 which is remarkably constant ranging from 0 3 to 0 4 wt six types of crystalline nanoparticles nps were identified by means of transmission electron microscopy in the trace element rich zones which are each a few micrometres wide 1 diopside 2 clinoenstatite 3 amphibole 4 mica 5 ulvospinel and 6 ti rich magnetite in addition al rich nanodomains which contain 2 3 wt of al occur within a single crystal of magnetite the accumulation of nps in the trace element rich zones suggest that they form owing to supersaturation from a hydrothermal fluid followed by entrapment during continuous growth of the magnetite surface it is also concluded that mineral nps promote exsolution of new phases from the mineral host otherwise preserved as structurally bound trace elements the presence of abundant mineral nps in magnetite points to a complex incorporation of trace elements during growth and provides a cautionary note on the interpretation of micron scale chemical data of magnetite

multistage sedimentary and metamorphic origin of pyrite and gold in the giant sukhoi log deposit lena gold province russia gold mineralization at sukhoi log in eastern siberia is hosted in a deformed neoproterozoic organic bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline the deposit contains about 30 million ounces of gold at an average grade of 2 0 g t au and is one of the largest known undeveloped gold resources the high grade gold zone forms a gently dipping tabular body in the core of the anticline the best gold grades occur in narrow bedding parallel pyrite quartz veinlets that have been folded during the main deformation event lower grade gold is associated with disseminated pyrite developed in and around the high grade core of the deposit detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments the two earliest forms of pyrite termed py1 and py2 are commonly developed in stratiform layers of micron sized crystals framboids and fine euhedra which are interpreted as synsedimentary to early diagenetic in origin coarser grained bedding parallel aggregates of inclusion rich pyrite termed py3 contain inclusions of arsenopyrite native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation coarse euhedral pyrite py4 overgrows the earlier pyrite py1 py2 and py3 and the slaty cleavage developed in the host rocks indicating a syndeformation timing late stage inclusion free pyrite py5 overgrows and replaces earlier sulfides and is considered to be syn to late deformation laser ablation inductively coupled plasma mass spectrometry la icpms analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold varying from 0 4 to 12 1 ppm with a mean of 3 22 ppm au and 1 900 ppm as py1 is also enriched in a suite of trace elements mo sb ni co se te ag cu pb zn mn ba cr u v which are similar to those concentrated by organic processes in euxinic sedimentary environments later generations of pyrite from py2 to py5 including pyrite in bedding parallel pyrite quartz veinlets contain progressively lower contents of invisible gold and most other trace elements however this metamorphic and postmetamorphic pyrite contains microinclusions of free gold arsenopyrite pyrrhotite sphalerite and chalcopyrite the paragenetic textural and chemical relationships at sukhoi log suggest that gold was clearly initially introduced prior to cleavage development accompanying sedimentation of the organic rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite subsequently accompanying deformation gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding parallel pyrite quartz veinlets two key processes are considered vital to the formation of the sukhoi log deposit original synsedimentary and early diagenetic concentration of gold dissolved within arsenian pyrite in organic rich black shales and metamorphic processes that liberated gold from the early forms of arsenian pyrite to be concentrated as free gold and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite quartz veinlets in the core of an overturned anticline these ore forming processes are unlikely to be unique to sukhoi log other black shale and turbidite hosted deposits that occur in rifted continental margin environments which have undergone collision and basin inversion may form by similar processes

characterization of mineral surfaces using fib and tem a case study of naturally weathered alkali feldspars using a focused ion beam fib instrument electron transparent samples termed foils have been cut from the naturally weathered surfaces of perthitic alkali feldspars recovered from soils overlying the shap granite northwest england characterization of these foils by transmission electron microscopy tem has enabled determination of the crystallinity and chemical composition of near surface regions of the feldspar and an assessment of the influence of intragranular microtextures on the microtopography of grain surfaces and development of etch pits damage accompanying implantation of the 30 kv ga ions used for imaging and deposition of protective platinum prior to ion milling creates amorphous layers beneath outer grain surfaces but can be overcome by coating grains with 85 nm of gold before fib work the sidewalls of the foil and feldspar surrounding original voids are also partially amorphized during later stages of ion milling no evidence was found for the presence of amorphous or crystalline weathering products or amorphous leached layers immediately beneath outer grain surfaces the absence of a leached layer indicates that chemical weathering of feldspar in the shap soils is stoichiometric or if non stoichiometric either the layer is too thin to resolve by the tem techniques used i e similar to 2 5 nm or an insufficient proportion of ions have been leached from near surface regions so that feldspar crystallinity is maintained no evidence was found for any difference in the mechanisms of weathering where a microbial filament rests on the feldspar surface sub micrometer sized steps on the grain surface have formed where subgrains and exsolution lamellae have influenced the propagation of fractures during physical weathering whereas finer scale corrugations form due to compositional or strain related differences in dissolution rates of albite platelets and enclosing tweed orthoclase with progressive weathering etch pits that initiated at the grain surface extend into grain interiors as etch tubes by exploiting preexisting networks of nanopores that formed during the igneous history of the grain the combination of fib and tem techniques is an especially powerful way of exploring mechanisms of weathering within the internal zone beneath outer grain surfaces but results must be interpreted with caution owing to the ease with which artifacts can be created by the high energy ion and electron beams used in the preparation and characterization of the foils

arsenopyrite pyrite association in an orogenic gold ore tracing mineralization history from textures and trace elements laser ablation inductively coupled plasma mass spectrometry la icp ms spot analysis and element mapping coupled with high resolution focused ion beam scanning electron microscopy fib sem imaging has been performed on au hosting sulfides from a proterozoic orogenic gold deposit tanami gold province north central australia gold distribution patterns in the arsenopyrite pyrite assemblage which probably crystallized toward the end of the au forming event suggest a process of initial scavenging of au into arsenopyrite and subsequent remobilization of that au following brittle fracture gold expelled from the sulfide lattice during the remobilization event is reconcentrated around the margins of the same arsenopyrite grains and within swarms of crosscutting microfractures the distribution of pb bi and ag closely mimic au indicating that these elements were also reconcentrated preservation of oscillatory zonation patterns for co ni sb se and te in arsenopyrite imply however that no significant degree of sulfide recrystallization took place residual concentrations of invisible gold in grain centers are 5 ppm in arsenopyrite and 1 ppm in coexisting pyrite the presence of submicron sized pores is suggestive of a fluid driven process rather than solid state diffusion micron scale 2 10 m remobilized gold is accompanied by fine particles 200 nm 2 m and nanoparticles 200 nm of gold the extensive variation of au concentrations within single arsenopyrite grains underlines the significance of textures when using trace element data to understand how gold ores evolved

trace and minor elements in sphalerite from base metal deposits in south china a la icpms study laser ablation icp mass spectroscopy has been used to investigate the geochemistry of sphalerite in a range of nine zn pb deposits in south china the deposits which are of different ages and belong to different metallogenic provinces have been assigned to the following genetic types skarn hetaoping luziyuan syngenetic massive sulphide dabaoshan laochang and bainiuchang and mississippi valley type huize mengxing niujiaotang based on the features of the ore even though their origin is heavily debated based on other criteria the giant jinding deposit is considered separately sphalerite from each genetic class of deposit shows a distinct chemical signature sphalerite from the skarn deposits is characterised by elevated lattice bound concentrations of co and mn the distal character of these skarn systems is reflected by the low in content of sphalerite the three syngenetic massive sulphide deposits feature sphalerite strongly enriched in in sn and ga whereas the deposits of mvt type are typically enriched in ge cd tl and as these divergent characters are reflected in absolute element abundances as well as in element ratios time resolved depth profiles for sphalerite from the chinese deposits confirm the presence of elements such as co in ge ga and cd in solid solution but the dataset expands the understanding of sphalerite mineral chemistry by also indicating that other elements whose ability to enter the crystal structure of sphalerite has been previously debated ag sn tl sb may also be in solid solution sphalerite is a refractory mineral and trace element analysis of sphalerite shows promise as a tracer of ore genesis even in overprinted ores systematic work on larger sample suites may help define the geochemical signature of different metallogenic epochs in regions as geologically complex as south china and help resolve the mechanism by which many of the debated ore deposits were formed

on the growth of colloform textures a case study of sphalerite from the galmoy ore body ireland abstract colloform textures have been described from many of the world9s sulphide ore deposits and involve formation of distinct microcrystalline layers these textures provide information related to sequential stages of ore formation yet their mechanism of growth is poorly understood this study has analysed a series of colloform samples from the galmoy zn pb mine ireland results indicate that the growth sequence is not always intuitive and layers that appear stratigraphic upon cursory observation may not be the crystal preferred orientation cpo of discrete colloform layers abruptly switches between different orientation axes examination of the same layers using in situ laser sulphur isotope analysis reveals equally striking changes in 34 s signature between end member bacteriogenic 25 and hydrothermal 10 sources although these results combined with petrographic observation allow the determination of a probable growth history there is no correlation between shifting cpo and 34 s signature trace element analysis reveals changes in trace element sequestration between colloform layers cadmium and chlorine rich layers correspond to a hydrothermal sulphur source whereas iron rich layers correspond to a bacteriogenic sulphur source in the absence of alternative mechanisms we suggest that the most likely factors influencing cpo changes are temperature and degree of supersaturation during two fluid mixing

mineralogy of the hse in the subcontinental lithospheric mantle an interpretive review abstract the highly siderophile elements hse os ir ru rh pt pd re au exist in solid solution in accessory base metal sulfides bms as well as nano to micron scale minerals in rocks of the subcontinental lithospheric mantle sclm the latter include platinum group minerals pgm and gold minerals which may vary widely in morphology composition and distribution the pgm form isolated grains often associated with larger bms hosted in residual olivine located at interstices in between peridotite forming minerals or more commonly in association with metasomatic minerals pyroxenes carbonates phosphates and silicate glasses in some peridotite xenoliths the pgm found inside residual olivine are mainly os ir and ru rich sulfides and alloys in contrast those associated with metasomatic minerals or silicate glasses of peridotite xenoliths consist of pt pd and rh bonded with semimetals like as te bi and sn nanoscale observations on natural samples along with the results of recent experiments indicate that nucleation of pgm is mainly related with the uptake of hse by nanoparticles nanominerals or nanomelts at high temperature 900 c in both silicate and or sulfide melts regardless of the residual or metasomatic origin of their host minerals a similar interpretation can be assumed for gold minerals our observations highlight that nanoscale processes play an important role on the ore forming potential of primitive mantle derived magmas parental to magmatic hydrothermal deposits enriched in noble metals the metal inventory in these magmas could be related with the physical incorporation of hse bearing nanoparticles or nanomelts during processes of partial melting of mantle peridotite and melt migration from the mantle to overlying continental crust

gold telluride nanoparticles revealed in arsenic free pyrite pyrite the most abundant sulfide on earth and a common component of gold deposits can be a significant host for refractory gold this is the first documentation of pore attached composite au telluride nanoparticles in arsenic free pyrite trace elements mapping in pyrite from an intrusion hosted au deposit with orogenic overprint dongping china shows trails of tellurides overlapping co ni zonation intragranular microfracturing anomalous anisotropy and high porosity are all features consistent with devolatilization attributable to the orogenic event the pyrite hosted nanoparticles are likely the frozen solid expression of te rich au ag pb bearing vapors discharged at this stage nanoparticle formation as presented here provides the smallest scale tool to fingerprint au trapping during crustal metamorphism

focussed ion beam transmission electron microscopy applications in ore mineralogy bridging micro and nanoscale observations abstract focussed ion beam scanning electron microscopy fib sem is a relatively new analytical tool that has been little applied to problems of ore genesis the technique enables high resolution cross section imaging and can be used to prepare thinned foils for study by transmission electron microscopy tem fib sem methods applied to sulphides and related compounds represent an in situ approach for sample characterisation and thus provides for crystal chemical data that can be placed into the geological context of a given ore deposit we present four study cases these deal with minor element incorporation and release in zns intergrowths and replacement among cu fe sulphides fabrics in au bearing as free pyrite and symplectites of bi sulphosalts within galena the data is discussed in the context of polytypism and planar defects for minor element incorporation and release superstructure ordering and formation of fine particles 100 2500 nm or nanoparticles

microstructural characterization and in situ sulfur isotopic analysis of silver bearing sphalerite from the edmond hydrothermal field central indian ridge abstract a close zn ag association has been noted recently in several polymetallic sulfide ore deposits from the indian ocean however the role of nanotextural controls on invisible silver distribution within sphalerite a significant ag carrier is still not well understood in this study typical zn sulfide samples from the edmond vent field central indian ridge can be roughly classified into three different groups based on their chemical compositions and mineral textures among them sulfosalt bearing fe poor zinc sulfides in sulfate dominant outer chimney walls usually contain higher contents of ag cu and pb up to wt levels than fe rich massive to disseminated sphalerite in zn fe rich chimney fragments coated by silicified crusts such sphalerite is represented by colloform botryoidal aggregates of optically anisotropic zns with a strongly disordered structure or hexagonal habit which are actually formed by coalescence and agglomeration of colloidal nanocrystalline particles using high resolution transmission electron microscopy hrtem and in situ micro xrd techniques we have investigated the ultrastructure and crystal chemistry of the 1 1 1 twin boundaries and wurtzite type stacking faults that occur in ag rich colloform or porous dendritic sphalerite submicroscopic electrum and ag nanoparticles appear to nucleate on the micro nano pore walls as cavity fillings or occur along grain boundaries between chalcopyrite tennantite inclusions and the host sphalerite interestingly the inhomogeneous distribution of precious metals and other chalcophile elements is generally concordant with the extent of recrystallization intragranular porosity as well as various degrees of structural disordering imperfectness i e bulk defect density in zns domains lattice defects and interfaces may play a limited role in promoting the simultaneous introduction of exotic impurities into colloform sphalerite during rapid growth even though certain morphological traits and aggregation state at the nanoscale seem to support a biogenic origin of these zns particles characterized by admixed polytypic intergrowth structures the mineralogical and geochemical features of highly defective sphalerite crystals in addition to their microscale s isotope signatures with relatively high 34 s values exhibit signs of abiologically mediated rapid precipitation caused by extensive mixing and cooling at edmond the physicochemical conditions and seafloor disequilibrium processes indicated by zns formation mechanism might facilitate the incorporation and enrichment of ag or other trace elements in hydrothermal sphalerite

new advances in trace element geochemistry of ore minerals and accessory phases the trace element composition of ore minerals is of fundamental importance to the understanding of mineralizing processes in situ analyses of ore minerals by empa sims and la icp ms have become essential approaches to many geochemical studies progress in micro beam techniques allows the examination at any location in the sample with unprecedented detail

geological and geochemical characteristics and formation mechanisms of the zhaishang carlin like type gold deposit western qinling mountains china abstract located in the western part of the min li metallogenic belt within the western qinling mountains the zhaishang gold deposit is a giant carlin like disseminated gold deposit discovered recently the ore deposit is present both in rocks of low grade metamorphic middle devonian and lower permian clastic formation which is composed of quartz sandstone siltstone calcareous slate and argillaceous limestone gold mineralization is strictly controlled by a fault zone minerals in ores are quite complex and consist of sulfides sulfosalt oxides sulfate carbonate tungstate telluride native metals and polymetallic alloys the diversity of mineral in the ores and the existence of microscopic visible native gold constitute the outstanding features of the gold deposit we believe that the mineral source of the ore deposit has a close connection with the host rocks because all samples show the light of the ree distribution patterns the s c pb h and o isotopic compositions show that the ore forming elements were mainly derived from the country rocks the underlying rocks and partially deep sources data obtained suggest that the ore forming fluids were derived predominantly from an active meteoric groundwater system mineralization and related alteration have features of a low water rock ratio ore forming temperatures are estimated to have been in the range from 120 to 240 c the dissolution of ferruginous limestone in the host rocks and the sulfidation of the dissolved iron by h2s introduced by ore fluids constituted not only the most important depositional mechanisms for the existence of microscopic visible gold grains but also favorable conditions for gold enrichment in the zhaishang gold deposit

trace elements of indium bearing sphalerite from tin polymetallic deposits in bolivia china and japan a femto second la icpms study abstract indium bearing tin polymetallic base metal deposits in japan toyoha ashio and akenobe china dulong and dachang and bolivia potosi huari huari bolivar and porco were studied using femto second laser ablation icpms fsla icpms and epma analyses for major and minor elements in sphalerite paying special attention to in concentrations sphalerite is a principal mineral in these tin polymetallic deposits and a broad range of in concentration is measured in the ores there are distinct differences in mode of occurrence of the sphalerite and the distribution of in the highest in concentration up to 18 wt occur as a zn in mineral within black sphalerite zones in an oscillatory zoned sphalerite from the huari huari deposits additionally jamesonite from the huari huari deposit also contains anomalous in values ranging from several hundreds to thousands g g sphalerite from the toyoha and the other bolivian deposits are characterized by oscillatory and chemical zoning whereas those from akenobe and the chinese deposits are represented by homogeneous distribution of in the 1000in zn values of sphalerite are in good agreement with those of the ore grade for each of the selected tin polymetallic deposits indicating that sphalerite is the principal host of in the in bearing sphalerite principally involves the combined coupled substitutions 2zn2 cu in3 3zn2 cu ag sn4 and 3zn2 2cu sn4 the first of these is apparent in sphalerite from huari huari and bolivar whereas the second is prominent in sphalerite from toyoha ashio potosi porco and dachang akenobe and dulong sphalerite features the dominant coupled substitution of 2zn2 cu or ag in3 owing to their poor sn content occasionally sub micron inclusions of minerals such as stannite and pb sb bearing sulfides can occur in sphalerite contributing to high cu sn and high ag contents respectively the observed correlations of each element in the in cu ag sn bearing sphalerite can be proposed as a fundamental reason for the indium enrichment related to sulfur rich oxidized magmatism in addition the ag content in sphalerite is considered a possible indicator of formation depth which ranges from plutonic to subvolcanic environments

gold behavior in intermediate sulfidation epithermal systems a case study from the zhengguang gold deposit heilongjiang province ne china abstract the zhengguang gold deposit a typical intermediate sulfidation epithermal deposit is located in the southeastern part of the duobaoshan orefield west of the hegenshan heihe suture zone in the eastern part of the central asian orogenic belt the deposit comprises five ore zones with total au reserves exceeding 35 tonnes with potential additional resources at depth all vein type orebodies are hosted by paleozoic volcanic rocks and comprise multiple vein sets 1 100 cm in thickness although gold generally occurs in native form or as electrum in epithermal deposits like zhengguang both pyrite and sphalerite are known to accommodate modest concentrations of invisible gold this study employs a combination of petrography and sulfide chemistry to determine the role of invisible gold in the zhengguang ores and the mechanisms of gold incorporation into epithermal sulfides three sulfide stages are identified an early quartz pyrite py1a py1b chalcopyrite ccp1 stage a subsequent quartz sphalerite sph2a sph2b pyrite py2a py2b py2c py2d chalcopyrite ccp2a ccp2b galena calcite stage and a late stage containing deformed quartz pyrite py3a py3b sphalerite petrography and sulfide chemistry allow three groups of pyrite au poor au rich and a distinct sb rich group to be distinguished alongside three groups of chalcopyrite bi rich intermediate bi and bi poor and two groups of sphalerite au poor au rich a potential porphyry system is indicated beneath the epithermal system by the appearance of au poor pyrite and bi poor chalcopyrite after precipitation of early au poor sulfides inflow of relatively low temperature epithermal fluids led to alteration and replacement of early porphyry related sulfides and to precipitation of au rich pyrite bi rich and intermediate bi chalcopyrite and sphalerite gold rich pyrite contains up to 140 ppm au interpreted as both as lattice scale substitution au1 and as included particles of native gold au0 epithermal chalcopyrite is an important silver carrier but although au is measurable it is a not a good carrier for gold a strong positive correlation between au and cu in pyrite from the first two stages indicate that gold and other metals were likely sourced from magma derived hydrothermal fluids the deposit was formed in the early paleozoic but some gold ores appear deformed and partially destroyed by a later metamorphic event during which a distinct sb rich pyrite crystallized this study should catalyze exploration in the orefield as it provides further support for an as yet undiscovered porphyry system close to the zhengguang deposit

fluid inclusion and noble gas studies of the dongping gold deposit hebei province china a mantle connection for mineralization the dongping gold deposit 100 t au occurs about 200 km inboard of the northern margin of the north china craton the deposit is mainly hosted by syenite of a middle paleozoic alkalic intrusive complex that was emplaced into late archean basement rocks both groups of rocks are intruded by late jurassic to early cretaceous crustal melt granite dikes and stocks some within a few kilometers of the deposit the gold ores were deposited during this latter magmatic period at about 150 ma a time that was characterized by widespread regional north south compression that formed the east west trending yanshan deformational belt the ores include both the telluride mineral bearing low sulfide quartz veins and the highly k feldspar altered syenite with most of the resource concentrated in two orebodies 1 and 70 fluid inclusion microthermometry indicates heterogeneous trapping of low salinity e g 5 7 wt nacl equiv fluids that varied from a few to 60 mole percent nonaqueous volatile species laser raman spectroscopy confirms that the vapor phase in these inclusions is dominated by co2 but may be comprised of as much as 9 mole percent h2s and 20 mole percent n2 methane concentrations in the vapor phase are consistently 1 mole percent the variable phase ratios are consistent with fluid immiscibility during ore formation fluid inclusion trapping conditions are estimated to be 250 to 375 c and 0 6 to 1 0 kbar helium isotope studies of fluid inclusions in ore stage pyrites indicate 3he 4he ratios of 2 1 to 5 2 ra ra 1 4 10 6 for air for orebody 1 and 0 3 to 0 8 ra for orebody 70 the former data suggest that at least 26 to 65 percent mantle helium occurs in the fluids that deposited the veins in orebody 1 the lower values for orebody 70 which is characterized by a more disseminated style of gold mineralization are interpreted to reflect an increased interaction of ore fluids with surrounding crustal rocks which may have contributed additional 4he to the fluids a mantle source for at least some of the components of the gold forming fluid is consistent with upwelling of hot asthenosphere and erosion of as much as 100 to 150 km of cool archean lithosphere beneath the craton during this time the dongping deposit is located along the 100 km wide north south gravity lineament which marks the western border of the thinned crust as both regional metamorphism of mesoproterozoic and younger cover rocks and widespread granite magmatism also occurred at ca 150 ma it is unclear as to whether one or both of these also contributed fluid and or metals to the hydrothermal system importantly these new data suggest that economically significant gold deposits of similar mineral style and fluid composition which are scattered along the margins of the craton may all be products of a fluid originally partly sourced within the mantle

invisible gold in arsenian pyrite and arsenopyrite from a multistage archaean gold deposit sunrise dam eastern goldfields province western australia the sunrise dam gold mine 11 1 moz au is the largest deposit in the archaean laverton greenstone belt eastern goldfields province yilgarn craton western australia the deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal scale structure the au content of arsenian pyrite and arsenopyrite from four mineralizing stages d1 d3 d4a and d4b and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry pyrite contains up to 3 067 ppm au n 224 whereas arsenopyrite contains up to 5 767 ppm n 19 gold in arsenopyrite d4a stage was coprecipitated and remained as invisible gold nanoparticles and or lattice bound during subsequent deformation events in contrast gold in pyrite is present not only as invisible gold but also as micrometer size inclusions of native gold electrum and au ag tellurides pristine d1 and d3 arsenian pyrite contains relatively low au concentrations 26 ppm the highest au concentrations occur in d4a arsenian rich pyrite that has recrystallized from d3 pyrite textures show that this recrystallization proceeded via a coupled dissolution reprecipitation process and this process may have contributed to upgrading au grades during d4a in contrast au in d4b pyrite shows grain scale redistribution of invisible gold resulting in the formation of micrometer scale inclusions of au minerals the speciation of au at sunrise dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple au precipitating mechanisms within a single plumbing system

blackening of fault gouge by comminution and pyrolysis of carbonaceous materials during earthquake slip abstract black fault gouges sometimes develop mainly in sedimentary rocks but the cause of the color transformation is not well understood here we demonstrated the blackening of synthetic mixtures of montmorillonite and bituminous coal and of montmorillonite and magnetite in milling heating and friction experiments mixed samples with a higher volume fraction of coal or magnetite before the experiments showed lower l values lightness index lower values indicate darker blacks because coal and magnetite are intrinsically black the milling and heating experiments showed that the l values of mixed samples of montmorillonite and coal drastically decreased with longer milling times and higher temperatures the l values of mixed samples of montmorillonite and magnetite also decreased with longer milling times but no notable change was observed in the samples after the heating experiments because comminution by milling induces granulation of the constituent materials blackening of the experimental samples was primarily caused by dispersal through the sample of fine black particles such as coal and magnetite but it could be strengthened by adsorption onto host particles of organic gases produced by pyrolysis of carbonaceous material at high temperature the friction experiment with mixed samples of montmorillonite and coal produced the remarkably low l values friction induces both comminution and heating of samples so the blackening could be greater than after either milling or heating alone therefore relatively black fault gouges compared with the surrounding host rocks might have experienced comminution and heating probably related to earthquake slip thus black coloration could be one of the important information on fieldwork

natural convection in the subarctic snow cover the purpose of this study was to determine if air convects in a natural snow cover to detect convection the temperature field in the subarctic snow cover in fairbanks alaska was measured hourly during three winters 1984 1987 using an array of thermistors which were suspended on threads and allowed to be buried by snowfall the results indicate that convection occurred sporadically in 1984 1985 and almost continuously in 1985 1986 and 1986 1987 the evidence was 1 simultaneous warming and cooling at different locations in a horizontal plane in the snow and 2 horizontal temperature gradients of up to 16 c m 1 during the winter warm and cold zones developed in the snow and remained relatively fixed in space we interpret these zones to be the result of a diffuse plumelike convection pattern linked to spatial variations in the temperature of the snow soil interface air flow was inferred to have been primarily horizontal near the base of the snow and vertical elsewhere calculated flow speeds were of the order of 0 2 mm s 1 with a maximum value of 2 mm s 1 the convective circulation was time dependent with perturbations such as high wind or rapid changes in air temperature triggering periods when horizontal temperature gradients were strongest suggesting that these were also periods when the air flow was fastest the coincidence of depth hoar crystals with horizontal c axes and the horizontal flow lines at the base of the snow suggests that convection may have affected crystal growth directions

naturally occurring gold nanoparticles and nanoplates during the weathering of gold deposits exceptionally pure 200 nm diameter nanoparticulate gold plates 6 nm thick are formed the particles display controlled growth of both size and shape and signs of assembly to form belts and sheets the gold is associated and intergrown with minerals formed by evaporation and is interpreted to have been deposited rapidly from saline groundwater during a drying event the size and morphology of the gold nanoparticles and nanoplates are identical to the products of experimentally manufactured gold colloids this represents the fi rst direct observation of colloidal nanoparticulate gold in nature confi rming this as an active mechanism of gold transport during the weathering of gold deposits

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

a combined chemical isotopic and microstructural study of pyrite from roll front uranium deposits lake eyre basin south australia abstract the common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at pepegoona pepegoona west and pannikan lake eyre basin south australia combined chemical isotopic and microstructural analysis of pyrite indicates variation in fluid composition sulfur source and precipitation conditions during a protracted mineralization event the results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low temperature hydrothermal systems in situ micrometer scale sulfur isotope analyses of pyrite demonstrated broad scale isotopic heterogeneity 34 s 43 9 to 32 4 vcdt indicative of complex multi faceted pyrite evolution and sulfur derived from more than a single source preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation authigenic pyrite underwent prolonged evolution and recrystallization evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra secondary hydrothermal pyrite commonly displays hyper enrichment of several trace elements mn co ni as se mo sb w and tl in ore bearing horizons hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types irregular variation in 34 s coupled with oscillatory trace element zonation in secondary pyrite is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization a late stage oxidizing fluid may have mobilized selenium from pre existing pyrite subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re crystallization and precipitation of selenium as native selenium these results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at beverley north insights into depositional conditions and sources of both sulfide and uranium mineralization and an improved understanding of pyrite geochemistry can also underpin an effective vector for uranium exploration at beverley north and other sedimentary systems of the lake eyre basin as well as in comparable geological environments elsewhere

the lepanto cu au deposit philippines a fossil hyperacidic volcanic lake complex abstract hyperacidic lakes and associated solfatara in active volcanoes are the expression of magmatic gas expansion from source to surface here we show for the first time that the vein system that comprises the 2 ma high sulfidation lepanto copper gold deposit in the mankayan district philippines was associated with a contemporary hyperacidic volcanic lake complex possibly the first such lake recognized in the geological record a 15 20 difference in sulfur isotopic composition between barite and sulfides and sulfosalts in the vent fumarole encrustations supports the interpretation that so 2 rich volcanic gas vented into the base of the lake and marginal to it and ties the mineralization directly to magmatic gas expansion fracture propagation and mineralization that occurred through a series of decompression steps within the feeder fracture network these data confirm that crater lake environments such as kawah ijen java indonesia provide modern day analogs of the lepanto and other high sulfidation cu au depositing environments we also provide extensive analysis of sulfosalt sulfide reactions during vein formation within the hyperacidic lake complex pyrite silica deposited first at high temperature followed by enargite that preserves the vapor solid diffusion of for example antimony tin and tellurium into the vapor from the crystallizing solid subsolidus intra crystalline diffusion continued as temperature declined pyrite and enargite are replaced by fe tennantite in the lodes which initially has low sb sb as atomic ratios around 13 5 close to the ideal tennantite formula but evolves to higher ratios as crystallization proceeds fumarole encrustation clasts and sulfosalts in the lake sediment are more highly evolved with a larger range of trace element substitutions including antimony substitution of especially zn te ag and sn into tennantite records metal and semi metal fractionation between the expanding magmatic gas and deposited sulfide sublimates provides a rare insight into the fate of metals and semi metals in the shallower parts of fracture arrays that feed modern hyperacidic lakes these data support a growing understanding of the formation of high sulfidation gold deposits as the consequence of single phase expansion of gas from magmatic gas reservoirs beneath the surface of active volcanoes without the intervention of a later aqueous fluid including groundwater aggressive sulfide sulfosalt reactions including pitting and the almost complete dissolution of earlier minerals are persistent characteristics of the vein assemblages and precious metals typically occur late in pits or along brittle fractures these characteristics support a hypothesis of mineral deposition at temperatures of the order of 600 c in contrast to available fluid inclusion data from enargite that record temperatures following phase transitions in the sulfosalt during the retrograde devolution of the deposit in the presence of groundwater

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

a statistical description of the microstructure of young sea ice in order to fully exploit microwave models of sea ice the standard ice characterization must be supplemented by a statistical description of the ice microstructure for the strong fluctuation theory this statistical description takes the form of the mean and variance of the permittivity plus correlation lengths we have computed these statistics for over 50 samples of young ice including both columnar congelation ice and desalinated bubbly ice samples were taken from different vertical depths and horizontal positions within the ice sheet and encompassed a comprehensive range of ice temperatures and brine volumes for each of these samples horizontal thin sections were photographed then digitized and analyzed on a personal computer based image processing system results indicate that correlation lengths correspond to the physical dimensions of the inclusions the brine pocket size typically tenths of a millimeter for saline ice and the air bubble size typically millimeters for desalinated ice for saline ice the shape of the correlation function was elliptical similar to the shape of the brine pockets in one case as the ice warmed from 20 to 1 c and the brine volume increased from 2 to 37 the correlation length increased from 0 14 to 0 22 mm

multi stage hydrothermal processes at the laozuoshan gold deposit in ne china insights from textures and compositions of sulfide assemblages abstract the laozuoshan gold deposit is a large gold deposit which experienced the early hydrothermal mineralization and the late hydrothermal mineralization in jiamusi massif northeast china the jiamusi massif hosts numerous gold deposits that are commonly considered as products of the metamorphic hydrothermal process during two oceanic subductions episodes in this study we report detailed textures observations identify the sulfides phases by the laser raman spectroscopy and obtain in situ composition data with electron probe micro analysis to further understand the formation and metasomatism of multi stage sulfides deposition in the laozuoshan gold deposit the paragenetic relationship between pyrite and marcasite at the nanoscale was also clarified by focused ion beam scanning electron microscopy and transmission electron microscopy according to the observed textural relationships among ore and gangue minerals the early hydrothermal mineralization period can be divided into three stages stage i to stage iii and the late hydrothermal mineralization period into four stages stage iv to stage vii the sulfides are mainly pyrrhotite po 1 in stage i with minor chalcopyrite arsenopyrite and pyrite the ag rich averaging 15 44 wt electrum au 1 is hosted in arsenopyrite which is also rich in cobalt averaging 2 69 wt pyrite py 2 is the main sulfide in stage ii with minor chalcedony and calcite the mineral stability relationships in both stage i and stage ii confirm that there was an increase in sulfur and oxygen fugacities and a decrease in temperature the sulfides are mainly arsenopyrite apy 2 in stage iii with minor native golds and tellurbismuth the native golds au 2 average 8 02 wt silver arsenopyrite geothermometers indicate precipitation temperatures between 420 and 390 c for stage iii the sulfur and oxygen fugacities of the ore related fluids were below the pyrite pyrrhotite buffer during stage iii revealing a reduced fluids system in the late hydrothermal mineralization period multiple magmatic activities caused multi stage hydrothermal fluids events in stage vi the pyrrhotite replaced by marcasite and pyrite through the dissolution reprecipitation mechanism indicating the increase in ph and oxygen fugacity of the fluids and alteration from weakly acidic and weakly reduced conditions to neutral and weakly oxidizing conditions the mineralogical and compositional evolution of the sulfides in the laozuoshan gold deposit constrain the physicochemical conditions of multi stage ore forming fluids which is of considerable significance in understanding the metamorphic hydrothermal superimposed gold bearing fluids evolved in the jiamusi massif

trace element heterogeneity in molybdenite fingerprints stages of mineralization abstract variations in molybdenite trace element chemistry represent a tool for discriminating discrete events in young magmatic hydrothermal systems and constrain the role of granites in older greenstone belt hosted gold systems we show that besides re and w typical lattice bound elements molybdenite also concentrates chalcophile elements with chalcogenide affinity such as bi pb and te ces elements from the latter group form nano to micron scale inclusions which also attract au and ag incorporation high concentration of all elements is attributable to lattice defects and coherent intergrowths between molybdenite and ce minerals rather than polytypism if both groups are used trace element patterns are useful for interpreting superimposed ore forming processes we test the validity of this hypothesis by carrying out laser ablation inductively coupled mass spectroscopy spot analysis and element mapping on high re molybdenite from the tertiary au deposit at hilltop nv usa and the archean boddington cu au deposit western australia whereas w and ces are affected by both deformation and interaction with subsequent fluids re is only affected by the latter an epithermal overprint at hilltop recorded in a grain with a ce rich halo surrounding a core with re w oscillatory zoning upgrades re content and is also traceable by measurable au at boddington granite derived fluids dilute re in precursor molybdenite but both granite and orogenic deformation assist ce mineral coarsening and au release

characterization of metal bearing particles in groundwater from the weilasituo zn cu ag deposit inner mongolia china implications for mineral exploration abstract nanoparticles in groundwater have important implications for facilitating the transportation of metals in groundwater and to a certain extent can reveal the geochemical conditions of the groundwater therefore there is an increasing interest in analytical techniques that allow for in depth characterization of nanoparticles in the groundwater and utilize these characteristics for geochemical prospecting metal bearing particles in groundwater samples from deep lying orebodies referred to as deep groundwater of the weilasituo zn cu ag deposit inner mongolia china and the groundwater from motor pumped wells of a catchment basin around weilasituo were chosen to study using high angle annular dark field scanning transmission electron microscopy haadf stem and transmission electron microscopy tem coupled with energy dispersive x ray spectrometer eds individual particles were characterized based on the tem compositional and structural investigation ag pb cu zn sn as and mo bearing particles were observed in the groundwater samples collected in the deep ore and the catchment basin these metal bearing particles are compositionally and structurally similar to the ore mineral metal bearing particles observed in the ore bodies and can directly reflect the ore forming elemental characteristics e g metallogenic element assemblage and mineralization type of the weilasituo deposit the result indicates that the metal bearing particles originating from the concealed ore bodies migrate via the groundwater flow and discharge to the catchment basin this finding implies that the metal bearing particle phases have great significances in facilitating the transportation of ore related species and forming the geochemical anomalies in the groundwater this field scale study demonstrates that by applying the analytical transmission electron microscopy the nanocharacteristics of metal particles can be utilized to improve the accuracy and sensitivity for geochemical mineral exploration

minor and trace elements in bornite and associated cu fe sulfides a la icp ms studybornite mineral chemistry abstract in situ laser ablation inductively coupled mass spectroscopy la icp ms has been used to provide a baseline dataset on the minor element contents in hypogene bornite and accompanying cu sulfides from 12 deposits with emphasis on syn metamorphic cu vein systems in norway and skarn porphyry and epithermal systems in se europe bornite contains significant concentrations of both ag and bi especially in the vein and skarn deposits studied and has the potential to be a major ag carrier in such ores concentrations of up to 1 wt of both elements are documented measured concentrations appear to be independent of whether discrete ag and or bi minerals are present within the analyzed sulfide where bornite and chalcocite or mixtures of cu sulfides coexist ag is preferentially partitioned into chalcocite over co existing bornite and bi is partitioned into the bornite bornite is a relatively poor host for au which mimics ag by being typically richer in coexisting chalcocite most anomalous au concentrations in bornite can be readily tracked to micron and submicron scale inclusions but bornite and chalcocite containing up to 3 and 28 ppm au in solid solution can be documented selenium and te concentrations in bornite may be as high as several thousand ppm and correlate with the abundance of selenides and tellurides within the sample selenium distributions show some promise as a vector in exploration offering the possibility to track a fluid source bornite and chalcocite are poor hosts for a range of other elements such as co ni ga and ge etc which have been reported to be commonly substituted within sulfides hypogene bornite and chalcocite may have significantly different trace element geochemical signatures from secondary supergene bornite

a seasonal snow cover classification system for local to global applications abstract a new classification system for seasonal snow covers is proposed it has six classes tundra taiga alpine maritime prairie and ephemeral each class defined by a unique ensemble of textural and stratigraphic characteristics including the sequence of snow layers their thickness density and the crystal morphology and grain characteristics within each layer the classes can also be derived using a binary system of three climate variables wind precipitation and air temperature using this classification system the northern hemisphere distribution of the snow cover classes is mapped on a 0 5 lat 0 5 long grid these maps are compared to maps prepared from snow cover data collected in the former soviet union and alaska for these areas where both climatologically based and texturally based snow cover maps are available there is 62 and 90 agreement respectively five of the six snow classes are found in alaska from 1989 through 1992 hourly measurements consisting of 40 thermal and

microscale data to macroscale processes a review of microcharacterization applied to mineral systems microanalysis can provide rapid quantitative characterization of mineral systems that complements the field and core scale observations traditionally made in ore deposits we review recent innovations in microanalytical procedures and their application to studies of ore deposits case studies are presented examining how microanalysis can provide constraints on macroscopic processes within mineral systems synchrotron x ray fluorescence shows centimetre scale chemical variations associated with proximity to mineralization in samples from sunrise dam gold mine western australia pseudomorphs of igneous plagioclase and chemically driven recrystallization interpreted from electron backscatter diffraction suggest that the system was dominated by fluid driven brecciation with very little shearing both the fluid chemistry and fluid pressure evolved during a protracted sequence of vein formation and alteration accompanying gold mineralization a second case study of sulphide mineralogy at the mt keith nickel sulphide deposit western australia demonstrates how x ray computed tomography combined with trace element mapping can constrain the chemistry and dynamics of magmatic systems large scale interaction between silicate and sulphide melts shown by homogenous palladium enrichment in pentlandite leads to a large proportion of globular ores with a high nickel content increasing use of microanalysis in ore deposit geology is resulting in the constant reassessment of established models for ore genesis though a combination of micro and macroscale datasets

factor analysis characterization of minor element contents in sulfides from pb zn cu ag hydrothermal vein deposits in portugal abstract we studied minor element contents in galena sphalerite and chalcopyrite from pb zn cu ag hydrothermal vein deposits in portugal and applied factor analysis to describe the dispersion and modes of association of these elements in the host minerals for this purpose a large suite of minor elements was analyzed through electronic microprobe epma wds in the aforementioned minerals and then the data were processed and compiled through the use of appropriate statistical software factor analysis fa was conducted in an adequate way as described in the paper and then applied to the minor element data this allowed us to distinguish between deposits groups of deposits and deposit districts also clues about different mineral generations were obtained by this method namely different generations of galena in some deposits relating to earlier and later stages of crystal growth which are often not microscopically identifiable fa allowed us to characterize the deposit districts by principal factors describing the galenas the sphalerites and the chalcopyrites providing a new insight into the studied portuguese deposits our study shows that factor analysis applied to minor elements in sulfides is a powerful tool in discriminating deposits and metallogenic regions

mineralogical study of sediment hosted gold deposits in the yangshan ore field western qinling orogen central china abstract the yangshan gold ore field is located in the southern subzone of the western qinling orogen mineralization is confined by the east west striking anchanghe thrust fault zone these subparallel faults constitute a branch of the regional mianlue structural zone crosscutting middle devonian carbonaceous carbonate and clastic rock sequences an ore bearing unit locally named the sanhekou formation the metasedimentary clastic and carbonate rocks containing fine grained sulfides are the main host rocks of the deposit with minor mineralization occurring as coarse grained pyrite quartz veinlets in black shale and as dissemination in some plagiogranite dykes electron microprobe empa and laser ablation inductively coupled plasma mass spectrometry la icp ms analyses show that arsenian pyrite and arsenopyrite are the major hosts for gold with tens of ppm up to weight percent levels of au and the au contents in arsenopyrite are one order of magnitude higher than those in pyrite a negative correlation of as and s in arsenian pyrite is consistent with the substitution of as for s in the mineral both arsenian pyrite and arsenopyrite in the yangshan ore field show chemical zonations with middle parts mantle enriched in as and au relative to cores and the outermost rims reflecting the chemical evolution of ore forming fluids high resolution transmission electron microscopy hrtem analysis failed to identify any nanoparticle of native gold even in the highest au parts of arsenopyrite this observation combined with the relatively homogenous distribution of au a positive correlation of as and au and au as ratios below the solubility limit of gold in arsenian pyrite and arsenopyrite suggests that invisible gold is likely present as structurally bound au 1 in sulfides although our work cannot exclude the existence of au nanoparticles in arsenian pyrite as identified in american carlin type gold deposits submicron native gold may be much more easily found in arsenian pyrite than in arsenopyrite because the later has larger capacity of enrichment of au 1 than the former due to the substitution of as for s the mechanism for nanoparticle formation is likely exsolution of native gold from metastable arsenian pyrite caused by later hydrothermal event which was recorded by the outermost as au poor overgrowths both in arsenian pyrite and arsenopyrite in the yangshan gold ore field

origin of the triassic qilinchang pb zn deposit in the western yangtze block sw china insights from in situ trace elemental compositions of base metal sulphides abstract the qilinchang pb zn deposit 5mt of sulphide ore at mean grades of 2 3 9 2 pb and 2 7 22 5 zn is hosted in early carboniferous carbonate rocks and mainly controlled by ne ns and nw trending structural belts between the xiaojiang and zhaotong qujing buried faults ore minerals are sphalerite galena pyrite chalcopyrite and marmatite whereas gangue minerals are dolomite calcite and quartz three generations of pyrite are recognized these include fine grained anhedral pyrite py i medium grained anhedral to subhedral hydrothermal pyrite py ii and coarse grained subhedral to euhedral hydrothermal pyrite py iii while the sphalerite occurs in two forms as fine grained intergrown with galena and associated with py i and py ii laser ablation inductively coupled plasma mass spectrometry la icp ms analysis was performed to evaluate trace element compositions of pyrite and sphalerite from different generations of ores py i has relatively higher concentrations of mg mn co ni and tl py ii in cu as se mo and sb relative to pyrite of other generations the contents of trace elements in py iii are variable but significantly enriched in ti v bi ag and pb compared to py i and py ii this variation indicates that these elements occur as micro mineral inclusions of possible ag pb bearing phases sphalerite of stage i has higher concentrations of mn fe co ni cu ga ge as ag cd in sb hg and pb than stage ii these elements are homogeneously distributed in all samples analyzed the incorporation of these elements is primarily through simple substitution mechanisms e g 2zn2 cu in3 as indicated from binary plots principal component analyses pca applied to la icp ms dataset for pyrite reveal two main clusters py i enriched in ni co and as py ii and py iii high in with v mn cu zn se mo ag sb au and bi likewise the pca also confirms two clusters of elements for sphalerite ge cu as sb ag fe and cd corresponding to sph i and in sn and ga corresponding to sph ii py i has higher co ni ratio ranging from 0 04 to 1 6 compared to py ii and py iii having co ni ratios from 0 to 0 706 and 0 0 696 respectively we report that the pyrites from the qilinchang deposit have co ni ratios slightly lower than typical mississippi valley type mvt deposits 0 2 7 2 and different from iron oxide copper gold iocg and porphyry cu deposits considering these geochemical signatures it can be suggested that the qilinchang deposit was not related to magmatic activities we thus propose that the ore forming fluids responsible for the formation of the deposit were generated from a low temperature environment similar to typical mvt deposits

detection of the depth hoar layer in the snow pack of the arctic coastal plain of alaska u s a using satellite data interpretation de l epaisseur et de la localisation de la couche de givre dans le manteau neigeux a partir des donnees de la temperature de brillance de nimbus 7 37 ghz du smmr