tectonic setting of synorogenic gold deposits of the pacific rim abstract more than 420 million oz of gold were concentrated in circum pacific synorogenic quartz lodes mainly during two periods of continental growth one along the gondwanan margin in the palaeozoic and the other in the northern pacific basin between 170 and 50 ma these ores have many features in common and can be grouped into a single type of lode gold deposit widespread throughout clastic sedimentary rock dominant terranes the auriferous veins contain only a few percent sulphide minerals have gold silver ratios typically greater than 1 1 show a distinct association with medium grade metamorphic rocks and may be associated with large scale fault zones ore fluids are consistently of low salinity and are co2 rich in the early and middle palaeozoic in the southern pacific basin a single immense turbidite sequence was added to the eastern margin of gondwanaland deformation of these rocks in southeastern australia was accompanied by deposition of at least 80 million oz of gold in the victorian sector of the lachlan fold belt mainly during the middle and late devonian lesser devonian gold accumulations characterized the more northerly parts of the gondwanan margin within the hodgkinson broken river and thomson fold belts additional lodes were emplaced in this flyschoid sequence in devonian or earlier palaeozoic times in what is now the buller terrane westland new zealand minor post devonian growth of gondwanaland included terrane collision and formation of gold bearing veins in the permian in australia s new england fold belt and in the jurassic early cretaceous in new zealand s otago schists collision and accretion of dozens of terranes for a 100 m y long period against the western margin of north america and eastern margin of eurasia led to widespread latest jurassic to eocene gold veining in the northern pacific basin in the former location late jurassic and early cretaceous veins and related placer deposits along the western margin of the sierra nevada batholith have yielded more than 100 million oz of gold additional significant ore forming events during the development of north america s cordilleran orogen included those in the klamath mountains region california in the late jurassic and early cretaceous the klondike district yukon by the early cretaceous the nome and fairbanks districts alaska and the bridge river district british columbia in the middle cretaceous and the juneau gold belt alaska in the eocene gold bearing veins deposited during the late jurassic and early cretaceous terrane collision that formed the present day russian far east have been the source for more than 130 million oz of placer gold the abundance of gold bearing quartz carbonate veins throughout the gondwanan north american and eurasian continental margins suggests the migration and concentration of large fluid volumes during continental growth such volumes could be released during orogenic heating of hydrous silicate mineral phases within accreted marine strata the common temporal association between gold veining and magmatism around the pacific rim reflects these thermal episodes melting of the lower thickened crust during arc formation slab rollback and extensional tectonism and subduction of a slab window beneath the seaward part of the forearc region can all provide the required heat for initiation of the ore forming processes

the vendian system of siberia and a standard stratigraphic scale in siberia vendian is equated with a yudoma complex or yudomian yudomian deposits of the siberian platform and adjacent geosynclines differ greatly in facies and thickness according to the composition and structure of yudomian deposits four facies provinces may be recognized on the platform local stratigraphic charts for each province are presented and their correlation and possibility to subdivide the vendian system in siberia into three horizons or stages are substantiated the upper stage nemakit daldyn on the basis of palaeontological evidence is in its turn subdivided into two zones anabarites trisulcatus and purella antiqua the most important early baikalian rearrangement is proved to take place around 800 50 ma the pre vendian late baikalian movements though less intensive make the determination of the yudomian lower boundary easier the specific character of vendian biostratigraphy is discussed involving all groups of the organic remains that causes the necessity of recognition subdivision and correlation on the basis of the whole complex of data the boundary between the vendian system and the lower cambrian tommotian stage in type section is proved to conform to the base of the pestrozvet formation which divides the a sunnaginicus and p antiqua zones

toward an understanding of the metallogeny of the tasman fold belt system the tasman fold belt system which makes up the eastern third of the australian continent is a composite of five paleozoic orogenic belts the major mineral provinces of the tasman fold belt system include provinces of volcanic hosted massive sulfide deposits porphyry granitoid associated cu au and au deposits and granitoid associated sn and w deposits as well as provinces of structurally controlled au and cu pb zn deposits the localization of these provinces is discussed in terms of the nature of the magmatism which is a source of heat and in many cases of fluids and metals the fracture systems which facilitate the transfer of heat magmas and or aqueous fluids through the crust and the timing and nature of the stress regimes that permit these fracture systems to be open to fluid flow the available data indicate that the magmatism of the cu au province of central west new south wales originated in the mantle magma systems linked with the deposits of the volcanic hosted massive sulfide province of western tasmania the sn w provinces of the tasman fold belt system and the porphyry associated au deposits of north queensland had their roots in crust mantle interactions crystal fractionation was an important process in the magma systems related to the development of these provinces a feature of the tasman fold belt system is the prevalence of major north south trending fault systems more subtle west northwest structural trends can be appreciated at the continent scale and these proterozoic structural trends appear to have exerted a significant control on the distribution of major mineral provinces within the tasman fold belt system extension reactivation of basement structures late in tectonic cycles was a major mechanism for creating permeable domains in the upper crust and focusing fluid flow and hydrothermal mineralization it is suggested that the permo carboniferous au and sn provinces of north queensland developed

predictive mapping of prospectivity and quantitative estimation of undiscovered vms deposits in skellefte district sweden mapping of mineral prospectivity and assessment of undiscovered mineral deposits both aim to delineate prospective ground for mineral exploration but the latter is usually carried out exclusive of the former we propose that the spatial distribution of known mineral deposits of the type sought is the key to link mapping of mineral prospectivity and assessment of undiscovered deposits we demonstrate this proposition in regional scale mapping of prospectivity for volcanogenic massive sulphides vms deposits and estimation of undiscovered vms endowment in the skellefte district sweden the results of analyses of the spatial distribution of known vms deposits and their spatial associations with geological features are consistent with existing knowledge of geological controls on vms mineralization in the district and we used them to define spatial recognition criteria of regional scale vms prospectivity integration of layers of evidence representing spatial recognition criteria of vms prospectivity via application of data driven evidential belief functions results in a regional scale map of prospective areas occupying 15 of the district and having fitting and prediction rates of 100 we used the map of prospective areas and proxy measures for degrees of exploration based on the spatial distribution of known vms deposits in one level prediction of undiscovered mineral endowment we obtained estimates of 709 kt undiscovered cu endowment 3190 kt undiscovered zn endowment 95 mt undiscovered ore tonnage and 48 undiscovered vms deposits these estimates are slightly ca 5 on average lower than and thus corroborated by estimates obtained via radial density fractal analysis of the spatial distribution of known vms deposits therefore mineral prospectivity mapping can be a part of mineral resource assessment if the spatial distribution of discovered deposits of the type sought is considered in both predictive modeling processes

stable isotopic calibration of the earliest skeletal fossil assemblages in eastern siberia precambrian cambrian boundary sections from the eastern margin of the siberian platform provide important reference sections for stable isotopic correlation of the newly defined precambrian cambrian boundary level since they contain some of the earliest pre tommotian shelly fossil assemblages known and are amenable to 13 c stratigraphy stable isotopes are examined from the dvortsy and ulakhan sulugur sections river aldan where sparse pre tommotian assemblages occur and from the uchur river region where the putative anabarites trisulcatus and purella antiqua zones of the nemakit daldynian stage are well developed diagenetic resetting of 18 o and 13 c must be taken into account when comparing such sections simple corrections allow for stable isotopic correlation of basal nemakit daldynian and tommotian strata across eastern siberia

fractal dimension and its translation into a model of gold spatial proxy abstract unraveling the spatial distribution of mineral deposits is an essential part of exploration and important for developing a better understanding of ore forming processes in this study gold assay results in g t of twelve boreholes completed from mysore block and eleven boreholes completed from nabhapur north block central lode system gadag gold field ggf india were analyzed using fractal analysis both the fractal correlation integral and rescaled range analysis were used to measure the fractal dimension from the gold concentration values the fractal dimension values obtained from the fractal correlation integral were used to better constrain the possible auriferous fluid flow pathways whilst results obtained from the rescaled range analysis were used to describe the behavior of auriferous veins across the boreholes the fractal dimension values were found to vary from 0 014 to 3 0 with the higher values taken to indicate the presence of well developed interconnected fault fracture networks representing steep permeable fluid flow pathways the lower fractal dimension values were taken to indicate unfavorable fluid flow pathways in other words higher grade gold ores were deposited along the structures represented by steep fractal gradients hurst exponent h values obtained from the rescaled range analysis were found to vary from 0 50 to 0 96 satisfying the condition 0 5

early cambrian chronostratigraphy and geochronology of south australia abstract the most successful chronostratigraphic correlation methods enlist multiple proxies such as biostratigraphy and chemostratigraphy to constrain the timing of globally important bio and geo events here we present the first regional high resolution shelly fossil biostratigraphy integrated with 13c chemostratigraphy and corresponding 18o data from the traditional lower cambrian terreneuvian and provisional cambrian series 2 of south australia the global zhuce shice positive excursions ii and iii and the care are captured in lower cambrian successions from the arrowie and stansbury basins the south australian shelly fossil biostratigraphy has a consistent relationship with the 13c results bolstering interpretation identification and correlation of the excursions positive excursion ii straddles the boundary between the kulparina rostrata and micrina etheridgei zones and the care straddles the boundary between the m etheridgei and dailyatia odyssei zones peaking in the lower parts of the latter zone new ca tims zircon dates from the upper hawker group and billy creek formation provide geochronologic calibration points for the upper d odyssei zone and corresponding chemostratigraphic curve embedding the lower cambrian successions from south australia into a global chronostratigraphic context this multi proxy investigation demonstrates the power of integrated methods for developing regional biostratigraphic schemes and facilitating robust global correlation of lower cambrian successions from south australia part of east gondwana with coeval terranes on other cambrian palaeocontinents including south and north china siberia laurentia avalonia and west gondwana

the significance of e w structural trends for the alice springs orogeny in the charters towers province north queensland e w structural and igneous trends in the charters towers province are highly anomalous within the overall n s trending tasman orogen of eastern australia and resulted from a sequence of n s shortening events a succession of e w trending fias foliation intersection inflexion axis preserved within porphyroblasts dated at 474 7 7 2 413 13 and 381 1 8 1 ma correspond with adjacent granite crystallization ages and e w trending fia ages in the greenvale province to the nw the magnetic anomaly map of australia reveals that this e w trending portion of the tasman orogen links with and truncates several earlier formed orogens the e w trend of the charters towers province resulted from overprinting of early palaeozoic n s trending structures in the tasman orogen by younger e w ones during the alice springs orogeny 450 300 ma resolving the e w pluton shape and distribution of cambrian to devonian magmatic activity plus the truncational nature of aeromagnetic data from central australia to the east coast

ore controls in the charters towers goldfield ne australia constraints from geological geophysical and numerical analyses the approach taken in this paper namely synthesising a wealth of previous information with new data and a genetic model in combination with integrated numerical analyses led to new insights into the geological controls on the localisation of auriferous veins and residual prospectivity of the charters towers goldfield ne australia the method also has implications for the assessment of other mature goldfields worldwide despite a number of different ore controls having operated within the charters towers goldfield the controlling factors can be linked to a single genetic model for orogenic granitoid hosted lode gold mineralisation in a brittle deformation regime d4 of ne sw to nne ssw shortening under conditions of supralithostatic fluid pressure and low stress difference spatial autocorrelation results suggest district scale alignment of the auriferous veins parallel to and overlapping with the ese wnw to e w striking charters towers ravenswood lineament a major crustal boundary in the basement to the ravenswood batholith at the camp scale auriferous veins have abundance and proximity relationships with nw se nnw sse ne sw and ene wsw oriented lineaments suggesting that structures that controlled gold deposition in one camp did not necessarily control mineralisation in other camps fractal dimensions obtained with the box counting method range from 1 02 to 1 10 whereas veins in the charters towers city camp are characterised by a significantly higher fractal dimension of 1 28 this discrepancy may be taken to imply that most or all outcropping and near surface deposits within the charters towers city camp have been found and that new discoveries are more likely to occur at greater levels of depth or outside the boundaries of this camp the new understanding has implications for the assessment of the residual prospectivity of the charters towers goldfield where large areas of prospective rock types and structures e g approximately 40 of the charters towers ravenswood lineament are hidden under cover this parameter space was inaccessible to the historic prospectors and has received relatively little attention from recent explorers the following steps are suggested for the development of a targeting strategy for lode gold exploration in areas of the goldfield under cover 1 identify from geological and geophysical data the ene wsw 15 and nnw sse 15 striking structures and geological boundaries within a 20 km wide corridor parallel to and centred upon the charters towers ravenswood lineament the potential control on gold deposit distribution at the regional to district scale 2 interpret from geological and geophysical data the distribution of pre middle devonian granitoids within these areas that are the preferred host rocks of the payable gold deposits 3 deduce from geophysical data the ene wsw 15 and nnw sse 15 striking structures that cut or bound the intrusions identified in step 2 4 locate segments along the structures identified in step 3 that deviate most from the geometry of a straight line e g potential bends or splays and or intersect other structures or geological contacts or both and 5 define and rank potential targets within the prospective areas identified in step 4 and systematically test the best ones

nature age and tectonic setting of granitoid hosted orogenic gold deposits of the jiaodong peninsula eastern north china craton china the jiaodong gold province along the southeastern margin of the north china craton has combined production and resources of 900 tonnes of gold more than 95 of the gold in this province is hosted in mesozoic granitoids which intruded late archean metamorphic basement rocks episodically at ca 160 150 and 130 126 ma the deposits of the jiaodong peninsula form one of the largest provinces of granitoid hosted lode gold deposits in the world the jiaodong gold deposits occur as massive auriferous quartz veins hosted in subsidiary second or third order faults and as disseminated and stockwork style mineralization hosted in alteration zones along major regional scale faults mineralization took place during brittle reactivation d3 of pre existing d2 ductile shear zones wall rock alteration is dominated by k feldspar and sericite with also sulfide minerals and extensive silicification closest to the orebodies the alteration was accompanied by the introduction of volatiles fe mg k rb ag as au bi and sb enrichment of base metals in the gold lodes is generally low although locally significant gold deposition took place at temperatures of 250 to 350 c for most gold deposits and the ore fluids are co2 bearing and have calculated salinities of 6 13 wt nacl equiv deposits from the zhao ye xixia and muping rushan belts have similar if not identical structural controls alteration patterns ore mineral assemblages and stable isotope signatures lead isotope data indicate that the ore stage leads were buffered by their host rocks the granitoid hosted gold deposits in the zhao ye belt are most radiogenic the greenstone hosted deposits in the xixia belt is the least radiogenic and the granitoid hosted deposits in the muping rushan belt have intermediate compositions gold mineralization in the zhao ye xixia and muping rushan belts in the jiaodong gold province appears to be broadly contemporaneously at ca 130 120 ma as constrained by shrimp u pb zircon dating on host rocks and a post gold dike as well as by ar ar rb sr and k ar dating of hydrothermal alteration minerals and ores this early cretaceous age is about 100 million years younger than the peak of ultra high pressure metamorphism in the qinling dabie sulu orogen between the north china and yangtze cratons and about 500 km south of the gold province however it overlaps with the extension and exhumation stage of the collisional orogeny and the subduction of the pacific plate beneath the eurasian continental crust whereas the majority of the jiaodong gold deposits occur on the margin of the north china craton some also occur in the suture zone between the two cratons they are significantly landward relative to the subduction zone of the pacific plate compared with typical orogenic lode gold deposits globally lode gold deposits of ca 130 120 ma occurred on both sides of the tan lu fault zone available data favor a temporal link of gold mineralization with pacific plate subduction

oxygen and carbon isotope stratigraphy of the palaeogene and cretaceous limestones in the bottaccione gorge and the contessa highway sections umbria italy we have made oxygen and carbon isotope measurements on limestone samples of albian to eocene age recovered from the bottaccione gorge section in the umbrian apennines central italy additional measurements have been made on topmost maastrichtian and palaeocene sediments from the adjacent contessa highway section our data from the bottaccione gorge show 13c maxima at the cenomanian turonian boundary and during the palaeocene as well as a pronounced 13c minimum 7 metres above the clay layer at the k t boundary our data from the contessa highway show a 13c minimum 9 metres above the k t boundary clay these minima are probably diagenetic artifacts in the bottaccione gorge there is evidence for a hiatus in the early middle eocene the palaeocene of the bottaccione gorge appears to have been affected by slumping or faulting in addition to the diagenetic overprinting giving a spurious 13c recovery after the k t boundary the contessa highway section appears to be more complete the coniacian maastrictian is characterized by relatively stable 13c values our data indicate an increase in 18o and therefore possible cooling across the cretaceous tertiary boundary in both the bottaccione and contessa highway sections

terrane processes at the margins of gondwana the process of terrane accretion is vital to the understanding of the formation of continental crust accretionary orogens affect over half of the globe and have a distinctively different evolution to wilson type orogens it is increasingly evident that accretionary orogenesis has played a significant role in the formation of the continents the pacific margin of gondwana preserves a major orogenic belt termed here the australides which was an active site of terrane accretion from neoproterozoic to late mesozoic times and comparable in scale to the rockies from mexico to alaska or the variscan appalachian orogeny the new zealand sector of this orogenic belt was one of the birthplaces of terrane theory and the australide orogeny overall continues to be an important testing ground for terrane studies this volume summarizes the history and principles of terrane theory and presents 16 new works that review and synthesize the current state of knowledge for the gondwana margin from australia through new zealand and antarctica to south america examining the evolution of the whole gondwana margin through time

crustal lineament control on magmatism and mineralization in northwestern argentina geological geophysical and remote sensing evidence abstract the relationship between long lived deep crustal lineaments and the locations of magmatic centers and associated mineral deposits has been investigated in the puna region of northwestern argentina through the analysis of regional aeromagnetic surveys landsat images and geological information the good exposure and excellent preservation of basement and supracrustal geology in this region makes it particularly suitable for such a study at a regional scale several contrasting magnetic domains are recognized which correlate with crustal geology two basement domains are separated by a nne trending boundary which is believed to correlate with a paleozoic suture zone between the pampia to the southeast and arequipa antofalla terranes to the northwest locally overlying these basement terranes is the cenozoic magmatic domain which is best developed in the n s trending volcanic arc at the western edge of the puna the cordillera occidental in addition four southeast trending volcanic zones extend for several hundred kilometers across the puna many important mineral deposits and areas of hydrothermal alteration are associated with these volcanic breakouts and we have selected three such areas for more detailed study bajo de la alumbrera argentina s largest porphyry copper deposit cerro galan the largest ignimbrite caldera in argentina with associated hydrothermal alteration zones and el queva a historic polymetallic district located within a major volcanic range a comparison of lineament maps generated from aeromagnetic and landsat tm images reveals broad correlation between these different remote sensing techniques which respectively highlight subsurface magnetic and surface geological features in addition the locations of magmatic and hydrothermal centers can be related to the interpreted structural framework and are seen to occur near the intersections of major lineament zones it is suggested that in three dimensions such intersection zones form trans lithospheric columns of low strength and high permeability during transpressional or transtensional tectonic strain and may thereby serve as conduits for magma ascent to the shallow crust pooling of large volumes of deeply derived magma in shallow crustal magma chambers may then result in voluminous devolatilization and the formation of hydrothermal mineral deposits it is important to note that in this model structural intersections serve as facilitators for magma ascent and volatile exsolution but do not in themselves cause this process other factors such as magma supply rate and tectonic stress are essential primary ingredients and local magmatic and volcanic processes affect the ultimate potential for ore formation nevertheless we suggest that lineament analysis provides a valuable framework for guiding the early stages of mineral exploration other regional and local geological considerations must then be applied to identify priority targets within this framework

geophysical investigations of the geology and structure of the pangushan tieshanlong tungsten ore field south jiangxi china evidence for site selection of the 2000 m nanling scientific drilling project sp nlsd 2 abstract the pangushan tieshanlong tungsten ore field located in the center of southern jiangxi province eastern nanling region contains many granitic plutons both exposed and concealed and hosts numerous tungsten polymetallic ore deposits despite many previous geological studies the deep geology and structure of the field are poorly known because few geophysical measurements have been undertaken in this study we carried out a variety of geophysical measurements including gravity magnetic field detection magnetotelluric sounding mt and high resolution seismic reflection to better outline the nature of the ore field and to aid in site selection for the 2000 m nanling scientific drilling project sp nlsd 2 to be carried out by the chinese sinoprobe program four granitic intrusives the tangcun pangushan huangsha and bai e plutons crop out independently at the surface but were found to be parts of a large batholith at depth the tangcun composite pluton which at the surface consists chiefly of caledonian granite and minor early yanshanian intrusive material was found to be chiefly early yanshanian granite concealed beneath the lower part of the caledonian granite the bai e pluton initially decreases in size with depth and then expands as it merges with the major batholith the pangushan and huangsha plutons are domes on the inferred batholith four granitic magma channels and a considerable number of faults have been identified due to its favorable geological conditions the top of the pangushan pluton is predicted to be the best candidate for ore prospecting it is basically a granite cupola with many cross cutting and parallel faults in addition it is characterized by a high gravity anomaly a high magnetic anomaly and locally a low electrical resistivity anomaly

chronology of early cambrian biomineralization data on the first appearances of major animal groups with mineralized skeletons on the siberian platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the cambrian radiation popularly known as the cambrian explosion with a higher precision and provide a basis for the definition of cambrian stages 2 to 4 the lophotrochozoa and probably chaetognatha were first among protostomians to achieve biomineralization during the terreneuvian epoch mainly the fortunian age fast evolutionary radiation within the lophotrochozoa was followed by radiation of the sclerotized and biomineralized ecdysozoa during stage 3 the first mineralized skeletons of the deuterostomia represented by echinoderms appeared in the middle of cambrian stage 3 the fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late neoproterozoic but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians the distribution of calcium carbonate skeletal mineralogies from the upper ediacaran to lower cambrian reflects fluctuations in the global ocean chemistry and shows that the cambrian radiation occurred mainly during a time of aragonite and high magnesium calcite seas

how to resolve the controls on mesothermal vein systems in a goldfield characterized by sparse kinematic information and fault reactivation a structural and graphical approach current mine exposures of auriferous veins in the charters towers goldfield ctgf are characterized by a scarcity of kinematic indicators furthermore the dip direction of exposed and historically mined orebodies largely coincides with the orientation of pre existing discontinuities consequently the reactivation of earlier structures during gold deposition is strongly indicated both factors complicate the structural analysis of the auriferous vein systems as slip on earlier faults likely occurred before new rock failure and evolution of fault networks reflecting the stress field present at the time of gold deposition despite access to drillcore open pits and underground workings extracted data were limited to ten occurrences of wear groove striations and three reverse separations of dykes and a pegmatite cut by sulphide bearing quartz veins because of the scarcity of kinematic information the structural analysis focused on the geometry of veins and ore shoots also applying basic graphical and kinematic methods

sponge spicules from the lower cambrian in the yanjiahe formation south china the earliest biomineralizing sponge record abstract sponges are the earliest metazoans and according to molecular clocks have a deep history back into the cryogenian however the record of their biomineralized elements below the ediacaran cambrian boundary has been controversial here we present the first and earliest indisputable record of hexactinellid spicules in the lowest cambrian terreneuvian below the small shelly fossil anabarites trisulcatus protohertzina anabarica assemblage zone zone i spicules recovered from cherts of the lowest yanjiahe formation in the yichang hubei province south china include monaxons diaxons triaxons and that are all siliceous in composition this earliest record of silica biomineralization by filter feeding metazoan suggests sponges have contributed to the cycling of silica in the oceanic system as early as the beginning of the phanerozoic these results along with a review of previously reported sponge occurrences suggest a two step evolution on sponges of the early cambrian

a new method for spatial centrographic analysis of mineral deposit clusters abstract a centrographic method for analysing mineral deposit clusters is illustrated using the komatiite hosted kambalda nickel sulphide deposit cluster yilgarn craton western australia in this method the standard distance circle divides the cluster into a more endowed inner part and a less endowed peripheral part the standard deviational ellipse another centrographic object depicts the preferred northwest southeast trend of nickel orebodies at kambalda weighted centrography shows that nickel endowment is greater in the eastern than western part of the cluster the spatio geometric interaction of the circle and ellipse splits the cluster into several partitions the relative concentration of nickel orebodies or endowment within a partition in relation to their concentration within the entire cluster is termed capture efficiency komatiite areal trace exhibits higher nickel orebody capture efficiency than spatio geometric partitions however some spatio geometric partitions exhibit nickel endowment capture efficiencies comparable to that of komatiite furthermore nickel orebody and endowment capture efficiencies of komatiite are elevated only within the standard distance circle these results suggest that at kambalda i the standard distance circle is a prime window for understanding the komatiite hosted nickel system and ii spatio geometric partitions are plausible locales for spatial analysis of nickel orebodies and endowment the proposed centrographic method is potentially useful in mineral resource estimations and mineral exploration targeting

carboniferous orogenic gold deposits at pataz eastern andeancordillera peru geological and structural framework paragenesis alteration and 40ar 39ar geochronology the pataz province forms the central part of a 160 km long orogenic gold belt extending along the eastern andean cordillera in northern peru and has produced a total of 6 million ounces moz gold from vein type deposits during the last 100 yr the deposits present several recurrent and typical field characteristics including 1 at a regional scale location of the mineralization in low order structures within a 1 to 5 km wide structural corridor east of a major north northwest striking lineament and in spatial association with the northnorthwest striking margins of the 330 to 327 ma pataz batholith 2 at the mine scale strong lithological controls of the vein geometries and styles the lodes occurring as fairly continuous 5 km long quartz veins inside or along the margins of the batholith or as branching and bedding concordant narrow ore shoots within adjacent folded ordovician turbidite sequences 3 consistent orientations of veins in particular within the batholith where more than 80 percent of the quartz veins are emplaced in north to northwest striking eastdipping brittle ductile deformation zones 4 a consistent au ag as fe pb zn cu sb bi te w metal association and a sulfide rich paragenetic sequence with a first stage composed of milky quartz pyrite arsenopyrite and ankerite and a second stage of blue gray microgranular quartz galena sphalerite chalcopyrite sb sulfosalts electrum and native gold followed by barren calcite dolomite quartz veinlets and 5 hydrothermal alteration of the vein wall rocks consisting of pervasive muscovite alteration with minor chlorite carbonate minerals and pyrite associated with strong bleaching in plutonic rocks and of weak muscovite and chlorite alteration in sedimentary rocks structural analysis of the deposits outlines four synchronous sets of mineralized fractures in the pataz district the predominant north to northwest striking east to northeast dipping system which is generally located in reactivated reverse faults accounts for more than 80 percent of the gold resource of the district three subordinate systems include in decreasing order of economic importance 1 east west striking flat extensional veins 2 bedding concordant veinlets in east west striking and north dipping to north south striking and east dipping limbs of long wavelength folds in ordovician sedimentary rocks and 3 weakly mineralized roughly east west striking sinistral vertical faults the vein orientations of the four structural sets are compatible with a triaxial strain model with the main shortening axis p oriented at 080 15 an intermediate axis oriented at 165 00 and a subvertical extensional t axis oriented at 255 80 under these conditions the richest ore shoots are preferentially sited in sinistral pull aparts which occur at the intersection of either north south striking lodes or extensional lodes with roughly east west striking vertical faults 40ar 39ar dating of the granodiorite monzogranite bodies of the pataz batholith provides good plateau ages at 329 2 1 4 and 328 1 1 2 ma for biotite separates which are similar to a published 329 ma u pb age for the granodiorite a muscovite and a biotite sample from an aplite dike yielded plateau ages at 322 1 2 8 and 325 4 1 4 ma respectively muscovite samples from alteration intimately associated with the gold mineralization yielded three 40ar 39ar spectra with low temperature staircase shaped patterns followed by plateau segments at 314 to 312 ma these ages analytically indistinguishable at the 2 level are considered to be the most probable ages for the mineralization event three other plateaulike ages between 305 and 288 ma have been obtained and are interpreted to reflect partial argon loss during late fluid circulation associated with the intrusion of late cretaceous monzonite porphyries the age determinations are inconsistent with a genetic link between the 314 to 312 ma pataz gold deposits and the 330 to 327 ma calc alkaline pataz batholith or with the 327 to 319 ma aplite dikes or the late cretaceous porphyry magmatism instead the overall homogeneity of the structural mineralogical and geochemical characteristics of the deposits over the 160 km long mineralized belt and the geotectonic evolution suggest that gold mineralization is linked to a large scale thermal event that occurred in a thickened collisional belt undergoing uplift tectonics

tectonic constraints on the timing relationships of metamorphism fluid production and gold bearing quartz vein emplacement abstract there is an ongoing discussion about the genetic significance of the postmetamorphic emplacement of many gold mineralizations as a contribution to this discussion this paper reviews the timing relationships between metamorphic devolatilization and metamorphism at different crustal levels for different tectonic processes for example denudation accompanying or following thickening causes metamorphism to occur later at depth than at shallow levels thus many internally heated terrains e g barrovian terrains are of deep later type that is peak metamorphism and devolatilization at deeper levels occurs at later times metamorphic processes of the deep later type may produce and release metamorphic fluids during prograde metamorphism at depth and precipitate them in the form of postmetamorphic quartz veins at shallow levels magmatic heating from below on the other hand is a deep earlier process causing inverse timing relationships in many metamorphic terrains deep later and deep earlier processes may compete for example if denudation at the surface accompanies heating from below if denudation and heating from below are of similar duration deep later characteristics prevail and a strongly bi modal age distribution of peak metamorphism in different crustal levels may arise the upper crust will experience metamorphism early but largely contemporaneously and the lower crust will experience metamorphism much later this process is particularly favourable for substantial simultaneous devolatilization of large sections of the lower crust to postdate metamorphism at shallow levels thus such processes may result in late infiltration events in cooling rocks of low metamorphic grade the common observation of postmetamorphic fluid infiltration and mineralization may therefore indicate but does not require that the mineralising fluids are related to the same metamorphic event

combining fractal analysis of mineral deposit clustering with weights of evidence to evaluate patterns of mineralization application to copper deposits of the mount isa inlier nw queensland australia the clustering of mineral occurrences and their spatial associations with particular geological features are critical aspects of mineral distributions for exploration and understanding ore genesis variations in the degree of clustering of mineral occurrences or geological features can be measured by fractal dimensions obtained from a shifting box counting method spatial associations between mineral occurrences and geological features can be quantified by the weights of evidence wofe method using the contrast value which increases with the strength of the spatial relationship a new method is proposed to evaluate mineral occurrence distributions by combining the power of fractal analysis of clustering with the wofe approach the method compares the correlation between the variation in degree of clustering of mineral occurrences and a geological feature in a study area with the contrast value of the same feature the possible outcomes can be simplified into four scenarios depending on whether the correlation in variation of clustering and the contrast are high or low respectively each outcome has specific exploration implications if either a high correlation in variation of clustering or a high contrast value is obtained the geological feature can be used for exploration targeting the integrated fractal and wofe approach is applied to copper occurrences in the proterozoic mount isa inlier nw queensland australia which hosts large numbers of copper deposits 1 869 occurrences including the world class mount isa copper deposit variation in clustering of copper occurrences has a positive correlation with variation in clustering of fault bends r 0 823 fault intersections r 0 862 and mafic rocks r 0 885 wofe results indicate that the copper occurrences are spatially associated with fault intersections and bends and with mafic rocks analyses were carried out separately for the two major lithostratigraphic sequences in the inlier the eastern and western successions the western succession copper occurrences are apparently more clustered than those of the eastern succession which may reflect a lower degree of exploration and or geological factors the association of copper occurrences with mafic rocks compared with fault bends and intersections is greater in the eastern succession which may reflect genetic factors correlations in the variation of clustering of mineral occurrences and geological features have a linear relationship with the contrast values and the spatial association between all geological features and copper occurrences constitute high correlation high contrast cases the linear relationship suggests that the geological features that control the clustering of the copper occurrences could be the same features that control their localization

mine tailings dams characteristics failure environmental impacts and remediation on a global scale demand for the products of the extractive industries is ever increasing extraction of the targeted resource results in the concurrent production of a significant volume of waste material including tailings which are mixtures of crushed rock and processing fluids from mills washeries or concentrators that remain after the extraction of economic metals minerals mineral fuels or coal the volume of tailings is normally far in excess of the liberated resource and the tailings often contain potentially hazardous contaminants a priority for a reasonable and responsible mining organization must be to proactively isolate the tailings so as to forestall them from entering groundwaters rivers lakes and the wind there is ample evidence that should such tailings enter these environments they may contaminate food chains and drinking water furthermore the tailings undergo physical and chemical change after they have been deposited the chemical changes are most often a function of exposure to atmospheric oxidation and tends to make previously perhaps safely held contaminants mobile and available if the tailings are stored under water contact with the atmosphere is substantially reduced thereby forestalling oxygen mediated chemical change it is therefore accepted practice for tailings to be stored in isolated impoundments under water and behind dams however these dams frequently fail releasing enormous quantities of tailings into river catchments these accidents pose a serious threat to animal and human health and are of concern for extractive industries and the wider community it is therefore of importance to understand the nature of the material held within these dams what best safety practice is for these structures and should the worst happen what adverse effects such accidents might have on the wider environment and how these might be mitigated this paper reviews these factors covering the characteristics types and magnitudes environmental impacts and remediation of mine tailings dam failures

microfossils from the neoproterozoic gangolihat formation kumaun lesser himalaya their stratigraphic and evolutionary significance abstract a well preserved microbial assemblage from the gangolihat dolomite kumaun lesser himalaya is described in the present paper the present assemblage contains both filamentous septate and non septate and coccoidal microfossils besides acritarchs and sponge spicules the assemblage includes 23 species belonging to 12 genera siphonophycus typicum is the most common species in the entire assemblage the assemblage shows an abundance of filaments over coccoids and acritarchs the assemblage includes siphonophycus septatum siphonophyscus typicum siphonophycus robustum siphonophycus capitaneum siphonophycus kestron and siphonophycus punctatum gunflintia minuta gunflintia grandis gunflintia barghoornii oscillatoriopsis media oscillatoriopsis obtusa oscillatoriopsis cuboides oscillatoriopsis sp nostocomorpha chlorogloeaopsis contexta obruchevella parvissima sphaerophycus parvum myxococcoides minor leiosphaeridia crassa trachyhystrichosphaera vidalii trachyhystrichosphaera sp micrhystridium pallidum cymatiosphaera minuta and sponge spicules of monaxons and hexactinellid affinity the assemblage suggests a neoproterozoic age for gangolihat dolomite

quo vadis tommotian the concept of the tommotian regional stage of the siberian platform has been closely linked to the idea of the cambrian explosion of animals and protists when the entire earth system shifted rapidly into phanerozoic mode we conducted a multidisciplinary study of an informal synstratotype of the lower tommotian boundary in the upper mattaia formation kessyusa group in the olenek uplift ne of the siberian platform the mattaia formation characterizes an upper shoreface to inner shelf depositional setting and provides important faunal ties and correlation with carbonate dominated and aliminosiliciclastic open shelf areas a section of the upper mattaia formation at boroulakh olenek river is suggested here as a model for the global boundary stratotype section and point for the base of the cambrian stage 2 this level contains the lowermost occurrence of the cosmopolitan fossil helcionelloid mollusc aldanella attleborensis section global markers near the base of the stage include a positive excursion of 13 c values reaching 5 4 a u pb zircon date of 529 7 0 3 ma massive appearance of diverse small skeletal fossils including watsonella crosbyi a sudden increase in diversity and abundance of trace fossils as well as a conspicuous increase in depth and intensity of bioturbation coincidently it is this level that has always been regarded as the lower tommotian boundary on the olenek uplift

geometrical and fractal analysis of a three dimensional hydrothermal vein network in a fractured granite abstract a three dimensional study of a fracture network has been performed on a 0 66 m 3 block of fine grained granite from la peyratte deux sevres france the block was sawn in nine parallel plates the fractures associated with altered haloes were mapped for each plate using a photographic method the nine fracture sets were subjected to an analysis of the percolated network based on a measurement of the width of altered haloes developed around fractures hydrothermal alteration is created by circulation of a certain amount of fluid flow in the rock we assume that the alteration zone width is proportional to fluid mass flow the width of alteration zones will give a good idea of the path preferentially followed by fluids the relation between fracture length and width of the alteration zone shows that the total fracture network consists in fact of two sorts the largest fractures surface 0 1 m 2 create a loose and poorly interconnected pattern in the block however they have developed wide alteration zones 3 mm and have then had a great role in fluid conduction they represent only 10 of the fractures but are responsible for 47 of alteration in volume approximately 80 of these fractures with wide alteration zones are oriented in the same direction this main network is linked to a more dense highly interconnected system made of shorter fractures with narrower altered zones fractal analysis has also been performed on pictures of the fracture patterns using the linear cantor s dust method fractal dimension values d indicate an anisotropy of fracture distribution on each plane moreover when the planes are compared to one another in succession variations of d values can be noticed indicating an inhomogeneity in the third dimension the study of such a three dimensional fracture set shows that fluids follow preferential paths within a fracture network and helps the understanding of fracture distribution

fractionation of fe and cu isotopes in acid mine tailings modification and application of a sequential extraction method abstract sulfidic mine tailings have a high potential for contamination of the environment by triggering acid mine drainage hence it is crucial to understand metal mobilization processes and to develop monitoring tools metal isotope fingerprinting as a potential monitoring tool for metal sulfide oxidation processes was in the focus of this study by using stable isotope signatures of cu and fe for fe a six step sequential extraction method was applied in order to separate potential fe bearing minerals water soluble exchangeable fraction fe iii oxyhydr oxides fe oxides sulfides and organic compounds and residual silicates for cu this method was modified into a four step extraction method water soluble exchangeable fraction oxalate fraction bound to fe oxides and sulfides residual to verify accuracy and precision of the sequential extraction method for metal isotope analysis isotope fractionation during the extraction procedure was investigated employing minerals for which the mineral composition and the isotopic composition was known the developed procedure is suitable to separate target minerals with only a small loss in the elemental budget no significant isotope fractionation was observed during the extraction procedure application of this method on two sites of porphyry copper mine tailings in the atacama desert in chile chanaral bay revealed several implications about the mobilization of fe and cu in an environmental setting iron contents and fe isotope compositions are homogeneous with depth 0 61 cm 56fe 0 2 0 3 for the bulk and the fe hyr oxide fraction and only the deepest samples at 60 cm exhibited lower 56fe values 0 which are likely related to the occurrence of an alluvium at this depth the fe silicate fraction shows higher 56fe values 0 6 0 9 most likely because of preferential leaching of the light fe isotopes this consequently indicates a more pronounced fe isotope fractionation with depth as is expected from longer weathering the fe sulfide fraction is isotopically lighter compared to the fe hydr oxide fraction because during sulfide oxidation the heavy fe isotopes prefer the oxidized forms and oxidative precipitation results in an enriched fe isotopic signature for fe hydr oxides the cu isotope compositions of all bulk samples and individual fractions except the cu sulfides of one site ch1 exhibited a decrease of the 65cu values from the depth towards the surface which is potentially related to cu mobilization during capillary water rise in the arid climate a correlation of 65cu with ph indicates preferential adsorption of 65cu on fe oxy hydroxides at site ch1 which is evident by a change of 65cu from 0 5 to 0 7 in the water soluble fraction at another site ch12 where ph at depths was potentially not high enough for the formation of fe minerals that could adsorb cu only minor cu isotope fractionation was observed in the water soluble fraction the cu sulfide fraction at site ch1 exhibits higher 65cu values with an increase from the bottom 0 42 to the surface 0 92 which might be related to preferential leaching of the light isotopes e g by microorganisms

paleozoic terranes of eastern australia and the drift history of gondwana abstract critical assessment of paleozoic paleomagnetic results from australia shows that paleopoles from locations on the main craton and in the various terranes of the tasman fold belt of eastern australia follow the same path since 400 ma for the lachlan and thomson superterranes but not until 250 ma or younger for the new england superterrane most of the paleopoles from the tasman fold belt are derived from the lolworth ravenswood terrane of the thomson superterrane and the molong monaro terrane of the lachlan superterrane consideration of the paleomagnetic data and geological constraints suggests that these terranes were amalgamated with cratonic australia by the late early devonian the lolworth ravenswood terrane is interpreted to have undergone a 90 clockwise rotation between 425 and 380 ma although the tamworth terrane of the western new england superterrane is thought to have amalgamated with the lachlan superterrane by the late carboniferous geological syntheses suggest that movements between these regions may have persisted until the middle triassic this view is supported by the available paleomagnetic data with these constraints an apparent polar wander path for gondwana during the paleozoic has been constructed after review of the gondwana paleomagnetic data the drift history of gondwana with respect to laurentia and baltica during the paleozoic is shown in a series of paleogeographic maps

an integrated approach to the search for gold in a mature data rich brownfields environment a case study from sigma lamaque quebec abstract the greater than 1300 participants in the 2015 integra gold rush challenge the biggest gold exploration crowdsourcing competition to date were given access to six terabytes of historic data collected at the c 12 moz au sigma lamaque gold deposits val d or district quebec and asked to identify targets with the highest potential for the next big gold discovery at the property this paper describes our approach to exploration targeting at sigma lamaque with particular emphasis on i integrating and interrogating the available data ii identifying mappable expressions key ingredients of ore forming processes using spatial data modelling in particular inversion modelling and advanced filtering of the available geophysical data iii developing a conceptual model in the framework of a mineral systems approach and iv translating the conceptual model into an effective tool for targeting gold in the val d or district

the relations between mean rock stress and fluid flow in the crust with reference to vein and lode style gold deposits abstract fluid movement in the crust at the typical depths of formation of vein and lode style gold deposits will be dominated by upward flow focussing of upward flow into discrete channelways as required to form gold deposits is due to lateral gradients in fluid pressure fluid channelways should have lower fluid pressures than surrounding rock if lateral gradients are induced by variations in permeability this is however at variance with inferences from quartz vein structures of high relative fluid pressures during the formation of gold deposits focussing into zones of low mean rock stress will in contrast be associated with high relative fluid pressures in the zone of focussed fluid flow variations in mean rock stress are a direct consequence of a regional deviatoric stress acting on an inhomogeneous rock sequence analysis of stress fields shows a wide variety of potential sites of low mean stress dependent on the geometry of rock units and on patterns of faults fractures or shear zones a model of fluid focussing in the crust due to variations in mean stress is thus consistent with the large variety of structural setting of vein and lode gold deposits observed in nature use of the model through the technology of stress mapping has the potential to generate viable exploration targets

fluid evolution in the kolar gold field evidence from fluid inclusion studies gold mineralization in the kolar schist belt of the dharwar craton occurs dominantly in the form of a sulfide poor au quartz lode the champion lode exposed in the mysore and other mines and sulfide rich auriferous lodes from the nundydroog mine fluid inclusion microthermometric experiments were conducted on primary inclusions in quartz intimately associated with au mineralization homogenization studies on aqueous biphase l v aqueous polyphase l v halite and aqueous carbonic lco2 vco2 laq inclusions from the champion lode furnish a temperature range of 120 to 420 c freezing of aqueous biphase inclusions and dissolution of halite in the aqueous polyphase inclusions provide salinity of 5 to 50 wt nacl equivalent fluid inclusion thermobarometry from the total homogenization of aqueous carbonic inclusions and from intersecting isochores of coeval pure carbonic lco2 vco2 and pure aqueous inclusions constrain the p t path of evolution of the fluid in the champion lode gold precipitation was likely to have been brought about in response to a sharp fall in pressure with attendant unmixing of liquid co2 from the parent h2o co2 fluid of possible metamorphic origin this would imply transportation of gold by some pressure sensitive complex such as the au carbonyl fluid characteristics are different in the sulfide rich auriferous lodes as indicated by the virtual absence of the co2 bearing and the halite bearing inclusions the fluid evolution path as evident from the crude positive colinearity of temperature and salinity is due to mixing of a low 200 c temperature low saline 7 wt nacl equivalent fluid with a high temperature 400 c high saline 50 wt nacl equivalent fluid the lack of co2 and association of au with sulfides indicate a different mode of gold transport as chloride or bisulfide complexing deposition of which was possibly brought about by fluid mixing

the fractal geometry of some stylolites from the calcare massiccio formation italy stylolites are serrated surfaces that form by stress enhanced dissolution though their geometry and morphology reflects their formation and evolution only a few studies have attempted to quantify them here we present results indicating that stylolites in limestone of the calcare massiccio formation jurassic italy are fractal over 4 5 orders of magnitude in spatial bandwidth with an average fractal dimension obtained by spectral and scaled windowed variance analyses clustering at 1 47 some stylolites from the skene cambrian usa and tamar cenomanian israel formations are fractal over 3 orders of magnitude with fractal dimensions of 1 26 and 1 43 these values are high relative to other natural surfaces and reflect the jagged topography of the stylolites preliminary results indicate that the fractal dimension and power are constant throughout the stylolite surface and are not orientation dependent furthermore we show that stylolite contours are fractal too the grain size does not register in our analyses implying that the grain is not a cutoff between processes rather stylolite generating processes operate similarly below and above the grain size our results suggest that the geometry of these stylolites especially at long wavelengths may not be sensitive to the immediate fabric surrounding them

detrital zircon age and biostratigraphic and chemostratigraphic constraints on the ediacaran cambrian transitional interval in the irkutsk cis sayans uplift southwestern siberian platform

spatial data analysis of mineral deposit point patterns applications to exploration targeting abstract systematic spatial analysis of mineral deposit point patterns can reveal significant spatial properties of mineral systems with major implications for regional mineral prospectivity modelling for valid results a study area needs to be clearly defined taking into account permissiveness of the geological units for a particular mineral system and effects of cover standard statistical tests assuming an isometric contiguous study area with regionally homogeneous distribution of deposits are likely to produce invalid results analysis of regional uniformity of spatial deposit density is required for adequate design and interpretation of tests for clustering spatial distribution of orogenic gold deposits in the hodgkinson province in queensland and the western lachlan orogen in victoria australia indicates the presence of significant regional linear metallogenic zones probably controlled by deep crustal domain boundaries oblique and not related to any recognised major faults within the metallogenic zones in both regions individual gold occurrences are strongly clustered into ore fields but the distribution of ore fields is random

intrusion hosted mineralization in the charters towers goldfield north queensland new isotopic and fluid inclusion constraints on the timing and origin of the auriferous veins auriferous quartz sulfide veins of the charters towers goldfield are mainly hosted in oxidized i type granitoids of the ravenswood batholith k ar and ar ar isotope age data of hydrothermal muscovite from alteration envelopes of veins at charters towers and the hadleigh castle mine 40 km east of charters towers are indistinguishable within error suggesting broadly synchronous gold deposition between 410 and 404 ma and across a significant segment of the ravenswood batholith published geochronological data indicate that several granitoid bodies were emplaced into the ravenswood batholith at the time of gold mineralization despite their association in space and time with igneous rocks the gold deposits lack an obvious causative intrusion moreover published lead isotope studies indicate that the lead in the ore was not acquired from any of the exposed intrusions a distal origin of the ore forming fluids also may be inferred from nitrogen isotope values of hydrothermal sericite suggesting wall rock interaction with metamorphic fluids or fluids that were in equilibrium with metamorphic rocks during the paragenetic stage of pyrite and arsenopyrite deposition stage ii veins of the charters towers goldfield contain three different types of fluid inclusions which are distinguishable by petrography and microthermometry this study is the first to report saline fluid inclusions in sphalerite 18 9 28 3 wt nacl equiv and vein quartz 20 9 24 7 wt nacl equiv trapped during the stage of gold deposition stage iii the range of temperatures and salinities particularly of the saline inclusions in sphalerite could indicate mixing between hotter more saline fluids e g deep seated magmatic and cooler more dilute solutions e g modified meteoric as the cause of gold deposition the geological and geochemical data are not compatible with derivation of fluids metals and ligands from individual plutons similarity of host rocks ore element associations alteration assemblages structural controls and tectonic settings strongly suggest that the auriferous veins of the charters towers goldfield belong to a group of granitoid hosted lode gold deposits that are generally classified as orogenic

organic walled microfossils from the chert phosphorite member tal formation precambrian cambrian boundary india the chert member also designated chert phosphorite member of the tal formation in the lesser himalaya contains well preserved organic walled microfossil assemblage the assemblage includes small 25 m acanthomorphic acritarchs sphaeromorphic acritarchs cyanobacterial filaments sponge spicules and thallophytic remains identified as micrhystridium lanceolatum m dissimilare m tornatum m lanatum cf lophosphaeridium sp paracymatiosphaera irregularis cymatiosphaera sp estiastra minima leiosphaeridia sp siphonophycus robustum thalloidal fragments and hexactinellid sponge spicules the present assemblage rich in small acanthomorphs appears to be best developed in upper nemakit daldynian beds based on acritarch biostratigraphy the present work suggests a nemakit daldynian to early tommotian age for the chert member which is in agreement with the formerly proposed age based mainly on small shelly fossils the assemblage is correlatable to the precambrian cambrian boundary microbiotic assemblage from china central asia and east european platform the assemblage shows low diversity of species the characteristic of inshore biota

a candidate stratotype for the precambrian cambrian boundary fortune head burin peninsula southeastern newfoundland the burin peninsula exhibits an exceptionally thick and essentially continuous succession of marine strata through the precambrian cambrian transition fossils are abundant and include trace fossils small shelly fossils vendotaenid algae soft bodied megafossils and microfossils the burin peninsula is readily accessible and has long been considered a potential area for a precambrian cambrian boundary stratotype a continuous section through the upper part of member 1 and all of member 2 of the chapel island formation is exposed at fortune head and this section is herein proposed as a global stratotype for the precambrian cambrian boundary the boundary horizon is located 2 4 m above the base of member 2 of the chapel island formation this horizon marks the base of the basal cambrian phycodes pedum ichnofossil zone and immediately overlies the top of the late precambrian harlaniella podolica ichnofossil zone shelly fossils sabelliditids first appear a few metres below the proposed boundary sof

spatial distribution of ore deposits conventional spatial distributions such as the negative binomial and neyman scott have been proposed as models for the clustered distribution of ore deposits b b mandelbrot has proposed that ore deposits are clustered at many different scales and that fractal distributions are appropriate the apparent fractal characteristics of geologic controls on the locations of hydrothermal deposits self similar systems of fractures circulation cells and magmatic intrusions support his proposal examination of the spatial distribution of 4775 hydrothermal precious metal deposits in the basin and range western united states reveals fractal distributions acting within two scale ranges together covering the entire range from 1 to 1000 km this result gives additional credibility to concepts of regional controls on mineralization such as metallogenic provinces and tectonostratigraphic terranes the distribution of these ore deposits about a known occurrence follows a regular radial density law within a range of radii r of 1 to 15 km the probability density function of these deposits is given by d 0 46 r 1 17 and within a range of radii of 15 to 1000 km by d 0 08 r 0 83 where d is deposits per square kilometre

stratified oceans and oxygenation of the late precambrian environment a post glacial geochemical record from the neoproterozoic of w mongolia the late neoproterozoic 750 545 ma was a time of revolutionary environmental change recurrent glaciation and tectonic upheaval which culminated in the evolution of metazoans and animal biomineralization geochemical data are presented for a post glacial 700 ma limestone succession from w mongolia 87 sr 86 sr is used to constrain the timing of early diagenetic exchange stratigraphic trends to high d 13 c carb and d 13 c org mirror sea level fluctuations which we argue is consistent with the hypothesis that late precambrian ocean chemistry was controlled by vertical stratification repeated establishment of stratification 700 545 ma would have led to greater oxygen availability in the surface environment a causal link between this oxygenation and the further evolution of animals is proposed

the formation of auriferous quartz sulfide veins in the pataz region northern peru a synthesis of geological mineralogical and geochemical data the pataz region in the eastern part of the north peruvian department la libertad hosts a number of important gold mining districts like la lima el tingo pataz parcoy and buldibuyo economic gold mineralization occurs in quartz sulfide veins at the margin of the calc alkaline pataz batholith that mainly consists of granites granodiorites and monzodiorites the batholith is of paleozoic age and cuts the precambrian to early paleozoic low grade metamorphic basement series its intrusion was controlled by a nnw trending fault of regional importance the gold bearing veins are characterized by a two stage sulfide mineralization bodies of massive pyrite and some arsenopyrite were formed in stage 1 and after subsequent fracturing they served as sites for deposition of gold electrum galena sphalerite and chalcopyrite it is concluded that gold was transported as a aucl 2 complex by oxidizing chloride solutions and deposited near older pyrite by micro scale redox changes and a slight temperature decrease mineralogical textural geochemical and microthermometric features are interpreted as a consequence of mineralization at considerable depth produced by a hydrothermal system linked with the emplacement of the pataz batholith acteristics in order to outline a general physicochemical model of the hydrothermal ore forming processes

pre tommotian age of the lower pestrotsvet formation in the selinde section on the siberian platform carbon isotopic evidence carbon isotopic data from the selinde section in the southeastern part of the siberian platform area are correlated with the reference isotopic profile from the lower cambrian stratotype sections of the lena aldan region but also show additional 13 c excursions unrecognized there the chemostratigraphic correlation suggests that the geological and fossil record of the lower pestrotsvet formation in the selinde section has a deeper history than the stratotype region this conclusion is important for both constraining the age of the earliest cambrian marine transgression on the siberian platform and providing a clearer understanding of the pace and order of early cambrian geochemical and biological events

modelling gold potential in the granites tanami orogen nt australia a comparative study using continuous and data driven techniques abstract the granites tanami orogen gto a poorly exposed component of the north australian craton is host to significant paleoproterozoic orogenic gold mineralization amounting to a total endowment of greater 20 moz au this study adopted a multi technique approach to mineral potential modelling mpm of orogenic gold deposits in the gto using four different techniques continuous fuzzy gamma geometric average and data driven index overlay and data driven random forest methods the predictive models generated in this study delivered the first public domain gold prospectivity maps for the northern territory nt portion of the gto the predictor maps at the core of these models represent mappable proxies of mineralizing processes believed to have been critical in the formation of the orogenic gold deposits and were generated in the framework of a mineral systems approach normalized density prediction area and area under the receiver operating characteristic curve methods were used to test the robustness of these predictors and determine the most effective the performance of the gold potential models generated in this study was assessed using the improved prediction area plot procedure with the data driven random forest approach having delivered the best performing model the multi technique approach taken in this study in which multiple mineral potential models are generated for the same study area and using the same predictor maps is a relatively new and as of yet underutilized approach to mpm that in contrast to the standard procedure i e generation of a single data or knowledge driven model ensures optimal utilization of the available conceptual and empirical information helps to better understand and minimize stochastic and systemic uncertainties facilitates cross validation of the resulting prospectivity models and allows the resulting models to be compared and contrasted from a practical exploration point of view the models served as decision support tools that helped to improve confidence in targeting underexplored gold prospective areas in the gto more effectively and identify new search areas previously not recognized as areas of high gold potential

controls on and prospectivity mapping of volcanic type uranium mineralization in the pucheng district nw fujian china abstract a number of volcanic type uranium deposits occur in pucheng district fujian province china structural controls and volcanic rocks clearly explain the uranium mineralization in this area to explore the subtle spatial associations of uranium occurrences with certain geological features these uranium deposits were subjected to l function fry and fractal analyses the results reveal that 1 these deposits are clustered have a bifractal distribution and are spatially parallel to the ne striking faults 2 the regional scale ne striking and prospect scale ne and nw striking faults exhibit significant spatial associations with uranium deposits as illustrated by the fry models 3 intersections of the faults with larger permeability and connectivity promote the mineralization process and 4 the spatial complexities of structures and lithological contacts quantified by the fractal dimension form strong and positive correlations with uranium occurrences and sizes finally by integrating nine spatial evidential layers representing the controlling factors for the occurrence of mineralization the artificial neural network model was applied to map mineral prospectivity for the uranium mineralization the receiver operating characteristics roc curve and the under the roc curve auc were utilized to measure the performance of the prospectivity models the model is highly capable of mapping uranium prospectivity because the auc is greater than 0 5 and close to 1 the prospectivity mapping confirmed that there is significant potential for uranium mineralization in the study area which opens up new avenues for further explorations on uranium deposits in pucheng district

structural characteristics of granitic plutons emplaced during weak regional deformation examples from late carboniferous plutons morocco abstract strain patterns have been investigated around shallow crustal granitic plutons emplaced during weak regional deformation in the western moroccan hercynian belt the plutons are distributed along reactivated deep faults and display elliptical shapes which are consistently oriented with respect to the regional strain field pluton age orientation and ellipticity can be correlated with strain history ductile deformation and contact metamorphism are mainly located in the thermally softened aureoles finite strain gradients towards plutons are accompanied by the development of superimposed microstructures finite strain trajectories and variations of strain ellipsoid shapes exhibit perturbations of the regional strain field around plutons structures internal to the plutons are continuous with regional structures foliation development in granitoids records a decrease in temperature during syntectonic pluton cooling geometry and kinematics of deformation reflect the influence of both regional deformation and pluton intrusion

nomenclature concepts and classification of oreshoots in vein deposits abstract oreshoots are discrete hypogene masses usually hosted within a planar channel surface lode or conduit which may be either a shear zone fissure fault zone or lithologic bed or unit such as a contact oreshoots are characterized by breadth strike 1000 m and dip and plunge 100 500 m lengths and have higher metal contents than the adjacent parts of the host conduit the mass of most oreshoots ranges between 1 10 6 and 2 10 4 tonnes there is a tendency for oreshoots to be thicker and richer in the center rather than to have uniform grade distributions the thickness of the oreshoots may be between 0 25 and 1 75 m in shear zone hosted deposits to up to 60 m in replacement deposits several conduits may connect to form vein systems vein systems have common fluid sources which result in general homogeneity of alteration mineralization types and oreshoot control and therefore commonly share the same plumbing system the internal constituents usually reflect unique episodes relating to ore formation the main intern constituents in oreshoots are mineralization gangue and alteration these constituents usually mix with each other in complex patterns the relationships between which may be used to interpret the processes of oreshoot formation the term ground preparation represents the effect of various events in the geologic history of an ore district or oreshoot area that have assisted in enhancing the rocks so that oreshoots can preferentially form in certain areas or geometries several types of ground preparation can be recognized 1 sequential deformation that produces a grain in the rock 2 severe faulting and jointing which augments permeability and areas where ore minerals can precipitate and 3 interplay between ore fluid and deformation to produce an oreshoot controls of oreshoot location and shape are usually due to dilatant zones caused by changes in attitude splays lithologic contacts and intersections in addition conceptual parameters such as district fabric magic distances and stacking are also used to describe the geometry of oreshoots controls in vein systems and the location and geometry of oreshoots within vein systems can be predicted by a number of qualitative concepts such as internal and external plunges district plunge district stacking conduit classification gradients and warps these concepts have a practical and empirical application in most districts where they are useful in the exploration for ore but are of such broad and general application that they can rarely be explained definitively

changes in lead and zinc lability during weathering induced acidification of desert mine tailings coupling chemical and micro scale analyses desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through flux rates along with other constraints metal toxicity precludes natural plant colonization even over decadal time scales since unconsolidated particles can be subjected to transport by wind and water erosion potentially resulting in direct human and ecosystem exposure there is a need to know how the lability and form of metals change in the tailings weathering environment a combination of chemical extractions x ray diffraction micro x ray fluorescence spectroscopy and micro raman spectroscopy were employed to study pb and zn contamination in surficial arid mine tailings from the arizona klondyke state superfund site initial site characterization indicated a wide range in ph 2 5 to 8 0 in the surficial tailings pile ligand promoted dtpa extractions used to assess plant available metal pools showed decreasing available zn and mn with progressive tailings acidification aluminum shows the inverse trend and pb and fe show more complex ph dependence since the tailings derive from a common source and parent mineralogy it is presumed that variations in ph and bioavailable metal concentrations result from associated variation in particle scale geochemistry four sub samples ranging in ph from 2 6 to 5 4 were subjected to further characterization to elucidate micro scale controls on metal mobility with acidification total pb ranging from 5 13 g kg 1 was increasingly associated with fe and s in plumbojarosite aggregates for zn both total 0 4 6 g kg 1 and labile fractions decreased with decreasing ph zinc was found to be primarily associated with the secondary mn phases manjiroite and chalcophanite the results suggest that progressive tailings acidification diminishes the overall lability of the total pb and zn pools

geologic setting paragenesis and physicochemistry of gold quartz veins hosted by plutonic rocks in the pataz region the pataz region is comprised of different low grade metamorphic proterozoic to early paleozoic basement series overlain by folded late paleozoic to early tertiary sediments and almost undeformed volcaniclastic rocks of late tertiary age the basement is intruded by the pataz batholith along a north northwest trending fracture zone this is the most important intrusive body of the region and consists of a geochemically varied calc alkaline magma suite the pataz batholith hosts numerous auriferous quartz veins with a simple two stage sulfide paragenesis microthermometric measurements indicate that stage i is characterized by medium chlorine k rich fluids probably related to magmatic dewatering stage ii displays medium to high chlorine solutions with significant amounts of na k ca and or mg this fluid composition is consistent with the strong interaction with the host rock as evidenced by the observed alteration features the initial chloride contents of stage ii are similar to those of stage i fluid inclusions further show a wide range of homogenization temperatures that probably reflect tectonically induced changes of pressure native gold with bimodal au ag ratios was found to be related chronologically to the second stage and spatially to pyrite that formed in the first stage as did most of the quartz and some arsenopyrite fractured pyrite was an important control on gold deposition frequently accompanied by galena sphalerite and chalcopyrite there is much evidence that vein formation occurs at considerable depth and is geometrically as well as temporally and genetically linked with the cooling stage of the pataz batholith local physicochemical factors account for quantitative mineralogic differences and for the deposition of either electrum or fine gold with less than 15 wt percent ag the early k bearing chloride solutions appear to be essentially magmatogenic fluids of the gold stage represent either new magmatogenic pulses or solutions recycled in a convective circulation system that included the nearby basement series gold leaching from precambrian to paleozoic country rocks appears appropriate in order to explain the regional distribution of the metal

structural controls and origin of gold silver mineralization in the grampian terrane of scotland and ireland gold bearing mineral deposits occur over a strike distance of 300 km within the grampian terrane of scotland and ireland this terrane consists of neoproterozoic lower ordovician rocks of the dalradian supergroup that were polyphase deformed and metamorphosed during the c 470 ma grampian orogeny sulphide rich au ag deposits occur in scotland at calliachar urlar burn tombuie tyndrum and cononish and in ireland at curraghinalt omagh cavanacaw croagh patrick cregganbaun and bohaun they are hosted by 0 1 6 m thick quartz veins and have a similar overall mineralogy including native gold as cu fe pb and sn sulphides with hessite tetrahedrite and electrum present in the first six localities above the mineralized quartz veins which are characterized by open space textures crystallized at c 3 5 km depth in the crust all of the deposits were structurally controlled and apart from curraghinalt occur within second order riedel r r and t fractures resulting from a regional n s trending maximum principal stress these deposits are of upper silurian to lower devonian post scandian age and are inferred to have crystallized from hot silica rich metamorphic fluids derived from dehydration reactions at the greenschist amphibolite facies boundary curraghinalt is an older grampian thrust related deposit plutonic igneous rocks mainly granitoid contributed in part to the fluids which were channelled into major orogen parallel strike slip faults to be injected by fault valve pumping into the damage zones and fault breccias of newly formed riedel fractures any residual fluid probably percolated to the ground surface to form rhynie chert type hot springs

distribution of trace elements in soils surrounding the el teniente porphyry copper deposit chile the influence of smelter emissions and a tailings deposit in the area surrounding the el teniente giant porphyry copper deposit eight soil sites were sampled at three depth levels in the summer 2004 the sites were selected for their theoretical potential of being influenced by past so2 emissions from the smelter and or seepage from a now idle tailings impoundment the soil mineralogy grain size distribution total organic matter contents major element composition cation exchange capacity and cu mo pb zn as and so4 2 concentrations were determined for all samples after nitric acid extraction and separate leaches by ammonium acetate ph 7 and sodium acetate ph 5 for water rinses only cu could be determined with the analytical set up used cu and so4 2 enrichment in topsoils was found at six sites either downwind from the smelter or within the combined influence of the smelter and the tailings impoundment both elements were released partially by ammonium and sodium acetate extractions due to the scarce background trace element concentrations of soil and rock outside the immediate mine area assessment of trace element mobility for mo zn pb and as was difficult arsenic was found to be concentrated in soil horizons with high smectite and or organic matter contents mo appears to be linked to the presence of windblown tailings sediment in the soils mobilization of mo zn and as for the acetate extractions was minimal or below the detection limits for the aas technique used the presence of windblown tailings is considered to be an additional impact on the soils in the foothills of the el teniente compound together with the potential of acidity surges and cu mobilization in topsoils after rainfalls two sites located at the western limit of the former so2 saturated zone with strongly zeolitized soils and underlying rock did not show any cu or so4 2 enrichment in the topsoils and remaining total trace element concentrations were below the known regional background levels

challenges in defining the base of cambrian series 2 and stage 3 formal subdivision of the cambrian system into four series and ten stages is in progress the base of cambrian stage 3 provisional which is conterminous with the base of cambrian series 2 provisional is expected to be placed at a horizon close to the first appearance of trilobites which marks the onset of the largest phase of the cambrian explosion conceptually an ideal boundary position would be marked by a significant and globally recognizable bioevent that divides the lower part of the cambrian system into a sub trilobitic terreneuvian series and a trilobite dominated series 2 if the level is to be identified principally through biostratigraphic means its position also needs to be recognizable using non biostratigraphic means and its correlation potential should be tested through detailed investigation of several continuous successions embracing the critical interval major difficulties in identifying a suitable horizon include strong biotic provincialism a plethora of regional unconformities and facies changes on different paleocontinents in the cambrian terreneuvian series 2 boundary interval levels that provide potential for intercontinental correlation include the first appearance position of trilobites and the approximately equivalent first appearance positions of certain small shelly fossil and acritarch species in addition a non biostratigraphic marker such as a stable carbon isotopic excursion may be useful as a correlation level cambrian series 2 and stage 3 are provisional stratigraphic units and their conterminous base was previously suggested to coincide to the appearance of trilobites compared to other potential chronostratigraphic indicators the first appearance of trilobites still has advantages for recognizing and correlating the base of stage 3 and should remain as the provisional primary marker for the boundary position

textures paragenesis and wall rock alteration of lode gold deposits in the charters towers district north queensland implications for the conditions of ore formation ore deposits of the charters towers goldfield ctgf are mainly hosted by fault fill veins extensional 8 of all veins and stockwork like 3 veins are less common and of little economic significance crosscutting relationships and published structural and geochronological data indicate a late silurian to early devonian timing of gold mineralization coincident with regional shortening d4 and i type magmatism paragenetic relationships which are uniform in veins everywhere within the ctgf suggest that vein formation commenced with the deposition of large volumes of buck quartz stage i followed by buck and comb quartz and significant pyrite and arsenopyrite precipitation stage ii gold was introduced during stage iii after earlier sphalerite and coincident with galena and chalcopyrite narrow discontinuous calcite veins of stage iv mark the waning of gold related hydrothermal activity or a later unrelated episode ore zones within the veins are everywhere composed of comb and or gray quartz calcite and or ankerite and bands or clusters of fractured pyrite that are spatially associated with galena sphalerite or chalcopyrite low grade or barren vein sections on the other hand are mainly composed of milky buck quartz with little evidence for modification overprinting or interaction with later fluids gold related hydrothermal wall rock alteration is symmetrically zoned displaying proximal sericite ankerite and distal epidote chlorite hematite assemblages that may be taken to imply wall rock interaction with near neutral fluids ph 5 6 isocon plots assuming immobile al p ti y and zr consistently indicate as k pb s and zn enrichment and na si and sr depletion in altered wall rock specimens relative to the least altered rocks alteration assemblages quartz textures fault rocks and published fluid inclusion and stable isotope data imply that the veins were formed under conditions of episodic fluid overpressuring 0 9 3 8 kbar at a depth of 7 km and a temperature of 310 c the published fluid inclusion data also imply that gold precipitation may have been brought about by fluid mixing however physi and chemisorption of gold complexes onto sulfide surfaces may have been important depositional processes and controls on gold enrichment at the millimeter to centimeter scale given that most gold particles are attached to the surfaces of pyrite crystals of stage ii or to etch pits and fracture surfaces within the earlier pyrite

high precision iron isotope measurements of terrestrial and lunar materials we present the analytical methods that have been developed for the first high precision fe isotope analyses that clearly identify naturally occurring mass dependent isotope fractionation a double spike approach is used which allows rigorous correction of instrumental mass fractionation based on 21 analyses of an ultra pure fe standard the external precision 1 sd for measuring the isotopic composition of fe is 0 14 mass for demonstrated reproducibility on samples this precision exceeds by at least an order of magnitude that of previous attempts to empirically control instrumentally produced mass fractionation dixon et al 1993 using the double spike method 15 terrestrial igneous rocks that range in composition from peridotite to rhyolite 5 high ti lunar basalts 5 fe mn nodules and a banded iron formation have been analyzed for their iron isotopic composition the terrestrial and lunar igneous rocks have the same isotopic compositions as the ultra pure fe standard providing a reference fe isotope composition for the earth and moon in contrast fe mn nodules and a sample of a banded iron formation have iron isotope compositions that vary over a relatively wide range from 56fe 0 9 to 1 2 this range is 15 times the analytical errors of our technique these natural isotopic fractionations are interpreted to reflect biological vital effects and illustrate the great potential fe isotope studies have for studying modern and ancient biological processes

carbon isotope geochemistry and palaeontology of neoproterozoic to early cambrian siliciclastic successions in the east european platform poland a well preserved stratigraphic record of the organic carbon isotopic composition across the precambrian cambrian transition has been obtained from a sequence of entirely detrital rocks underlying the lublin slope east european platform poland the observed 13 c pattern for organic carbon is comparable to isotope data determined for coeval carbonate platform sequences elsewhere these results underline the truly global nature of these secular variations within the carbon cycle during the terminal proterozoic and early cambrian largely independent of host lithology and facies the direct combination of micropalaeontological and geochemical results from sedimentary organic matter allows a detailed interpretation of the isotope record as probably caused by secular changes in the net balance of burial and erosion rates of repositories of organic carbon furthermore these variations appear to be directly correlatable with changes in the diversity and abundance of the biota and radiation extinction events

exploration information systems a proposal for the future use of gis in mineral exploration targeting abstract the advent of modern data collection and storage technologies has brought about a huge increase in data volumes with both traditional and machine learning tools struggling to effectively handle manage and analyse the very large data quantities that are now available the mineral exploration industry is by no means immune to this big data issue exploration decision making has become much more complex in the wake of big data in particular with respect to questions about how to best manage and use the data to obtain information generate knowledge and gain insight one of the ways in which the mineral exploration industry works with big data is by using a geographic information system gis for example gis platforms are often used for integration interrogation and interpretation of diverse geoscience and mineral exploration data with the goal of refining and prioritising known and identifying new targets here we i briefly discuss the importance of carefully translating conceptual ore deposit models into effective exploration targeting maps ii propose and describe what we term exploration information systems eis a new idea for an information system designed to better integrate the conceptual mineral deposit model i e the critical and constituent processes of the targeted mineral system with data available to support exploration targeting and iii discuss how best to categorise mineral systems in an eis as scale dependent subsystems to form mineral deposits our vision for the future use of eis in exploration targeting is one whereby the mappable ingredients of a targeted mineral system are translated and combined into a set of weighted evidence or proxy maps automatically resulting in an auto generated mineral prospectivity map and a series of ranked exploration targets we do not envisage the eis replacing human input and ingenuity rather we envisage the eis as an additional tool in the exploration toolbox and as an intelligence amplifying system in which humans are making use of machines to achieve the best possible results

geochemistry of synsedimentary cements in early cambrian reefs abstract synsedimentary fibrous calcite cements in reefs representing different periods of early cambrian time from eastern siberia southern australia and eastern canada were analyzed to determine whether they retained information about the chemical and isotopic compositions of the seawater from which they precipitated although petrographically similar the sr o and c isotopic compositions as well as the sr and mg contents of the cements from the three areas are different such differences can be attributed to varying degrees of diagenesis of the cements that correlate with the tectonic history of each area cements from the siberian craton are the least altered cements from near the appalachian orogen are partially altered and cements from the flinders fold and thrust belt are extensively altered strontium contents of the fibrous cements generally increase with mg contents although the correlation among these two elements is more variable than that reported for devonian or holocene cements those cements with sr mg ratios near 0 04 which include clear fibrous calcite have the lowest 87 sr 86 sr ratios and have been least altered strontium isotopic ratios in the least altered cements are lower than whole rock ratios and probably approach the original values of early cambrian seawater 18o values in the cements are variable because of exchange with diagenetic fluids whereas 13c values exhibit local variations that do not match temporal curves constructed from whole rock data for the same regions thus most of the original chemical and isotopic compositions of these cements have been variably changed through diagenesis although limited information about the composition of early cambrian seawater such as sr and c isotopic compositions have been retained in some samples

the influence of aluminium industry and bedrock lithology on the oxide content in the urban soil of sibenik croatia the content of major element oxides al2o3 sio2 cao mgo fe2o3 p2o5 k2o tio2 and mno in soil surrounding the light metal factory tlm which was producing aluminium from 1937 till 1991 was investigated by edxrf and xrd the evaluation of a possible aluminium pollution linked to the industrial activity was studied by a comparison of soil around the tlm with control soil samples taking into account natural variations caused by bedrock lithology control samples were taken in the soil developed upon the upper cretaceous limestones and middle eocene flysch deposits while the tlm soil was sampled over the upper cretaceous and early to middle eocene limestones that way the samples constituted four groups each containing five to seven samples control soil overlying flysch deposits differed strikingly from the other three groups by its increased cao values and decreased content of al fe mn and ti oxides confirming the overall geochemical imprint of bedrock lithology on the analysed soils however a specific mineral composition presence of alumina of the tlm soil together with peculiar correlations among al2o3 and other oxides indicates a certain extent of aluminium pollution of the investigated area

spatial analysis of mineral deposit distribution a review of methods and implications for structural controls on iron oxide copper gold mineralization in carajas brazil abstract mineral deposits are formed by interaction of various geological processes and conditioned by controls that favor their formation and preservation the understanding of mineralization controls is critical for mineral exploration because it allows focusing exploration on regions where these controls are concentrated the analysis of the spatial distribution of mineral deposits particularly on a regional scale can provide information relevant to the understanding of regional scale processes involved during their formation here we present a review of fry and fractal methods for spatial analysis of mineral deposit distribution and an application using the iron oxide copper gold iocg deposits of the carajas mineral province brazil results show that different iocg mineralization structural controls acted in scales of 40 km the iocg deposits cluster at scales of

mapping of prospectivity and estimation of number of undiscovered prospects for lode gold southwestern ashanti belt ghana in the southwestern part of the ashanti belt the results of fractal and fry analyses of the spatial pattern of 51 known mines prospects of mostly lode gold deposits and the results of analysis of their spatial associations with faults and fault intersections suggest different predominant structural controls on lode gold mineralisation at local and district scales intersections of nne and nw trending faults were likely predominantly involved in local scale structural controls on lode gold mineralisation whilst nne trending faults were likely predominantly involved in district scale structural controls on lode gold mineralisation the results of the spatial analyses facilitate the conceptualisation and selection of spatial evidence layers for lode gold prospectivity mapping in the study area the applications of the derived map of lode gold prospectivity and a map of radial density of spatially coherent lode gold mines prospects results in a one level prediction of 37 undiscovered lode gold prospects the applications of quantified radial density fractal dimensions of the spatial pattern of spatially coherent lode gold mines prospects result in an estimate of 40 undiscovered lode gold prospects the study concludes finally that analysis of the spatial pattern of discovered mineral deposits is the key to a strong link between mineral prospectivity mapping and assessment of undiscovered mineral deposits

controls on mineral deposit occurrence inferred from analysis of their spatial pattern and spatial association with geological features in this paper point pattern analysis fractal analysis and fry analysis were employed to study the spatial pattern of known occurrences of mineral deposits of the type sought whereas distance distribution method was applied to study the spatial associations between various geological features and known occurrences of mineral deposits of the type sought in the aroroy district philippines the results of the applications of these spatial analytical techniques support a conceptual model of district scale mechanism of geologic controls on low sulphidation epithermal au mineralization which involves a more or less regular mesh of interlinked zones of extension faults fractures at and or around intersections of nnw and nw trending strike slip faults fractures integration of spatial evidential data layers representing these structural controls and surficial geochemical anomalies via knowledge guided application of data driven evidential belief functions results in delineation of prospective areas occupying about 25 of the district in which there is about 70 likelihood of undiscovered occurrences of low sulphidation epithermal au deposits

geochemistry of the mount windsor volcanics implications for the tectonic setting of cambro ordovician volcanic hosted massive sulfide mineralization in northeastern australia the mount windsor subprovince is an important relic of upper cambrian to lower ordovician sedimentation and volcanism in the northern part of the tasman orogenic zone volcanic hosted massive sulfide mineralization occurs at several stratigraphic horizons within the volcano sedimentary package and one major mine is operational within the belt major and trace element data and nd isotope ratios are presented for the least altered coherent units from the three major volcanic bearing formations in the mount windsor subprovince the data are used to discriminate four major phases of volcanism and related intrusive activity derived from three isotopically discrete sources and to assess the geodynamic setting in which the volcanism occurred the earliest phase of mafic volcanism has minor and trace element characteristics suggesting an alkaline intraplate or rift association and it was probably produced by partial melting of attenuated subcontinental lithospheric mantle the overlying mount windsor formation silicic volcanics have nd isotope characteristics epsilon sub nd 480 ma 4 7 to 12 8 that suggest they were produced by partial melting of underlying precambrian crustal rocks mafic volcanics of the overlying trooper creek formation include a low tio 2 suite and a high tio 2 suite with a range of distinguishing chemical characteristics but similar nd isotope ratios epsilon sub nd 480 ma 3 8 2 3 which indicate derivation from relatively depleted asthenospheric mantle variably modified by subduction processes the high tio 2 suite is also represented by abundant intrusions within the underlying volcanic package the more silicic volcanics in the trooper creek formation appear to be cogenetic with their mafic associates but have varying nd isotope ratios which suggest progressive crustal interaction with increasing sio 2 content comparisons with modern volcanic compositions and ore depositional environments suggest that the volcanic and sedimentary units within the mount windsor subprovince were deposited in a back arc basin developed by extension of continental lithosphere along the eastern australian margin in the late cambrian and early ordovician mineralization and volcanic deposits of similar age farther north in the tasman orogenic zone suggest that this basin may have had a north south orientation although there is no clear evidence remaining of the original arc front deposits

formation of oreshoots in mesothermal gold quartz vein deposits examples from queensland australia abstract mesothermal gold quartz vein deposits in granitoid hosted and melange sediment hosted goldfields contain oreshoots in areas of structural dilation the environment of formation is localized at depths of 2 5 km in brittle to brittle ductile shear zones which have stick slip seismic movement lithologic contacts and fissure intersections affect the shape and geometry of the oreshoots mineralizing fluids in these shear zones range between 3 and 10 wt nacl equiv with 18 o values of about 5 8 fluids are locally co 2 bearing with formation temperatures of between 220 and 350 c fluid source is either of deep magmatic or metamorphic origin and can rarely be correlated directly with nearby plutonism fluid transport is via single pass flow in high permeability conduits such as mylonites in granitoids or melange cleavage in sediments complex mixtures of mineralized quartz gouge fault rocks and altered wall rock reflect the environment of formation comb ribbon buck and breccia quartz and microscopic textures indicate different processes and stages of oreshoot formation quartz deposition is due to changes in silica solubility resulting from temperature and pressure fluctuations local pressure changes are due to reduced velocity of the fluid in dilated zones according to bernoulli s equation at restricted or dilated portions of the fissure throttling and adiabatic cooling are common and result in quartz deposition and channel choking which lead to pressure and temperature build ups and faulting the long dip lengths in many mesothermal oreshoots may also account for substantial pressure and temperature reductions in the fluid from bottom to top the venturi effect in connecting fissures may also affect quartz deposition microscopic textures indicate that multiple generations of quartz have been involved in cracking stress corrosion and dissolution due to porosity changes and dilation prior to and during faulting gouge and clay seams stabilize fault movement and may have acted as impermeable barriers and pressure seals which channelled fluid flow and if hydrated may have expelled concentrated brines when compressed by faulting hydrothermal alteration indicates early diffusive transport and chemical and ph gradients away from the oreshoots four main stages of oreshoot formation occur from the outside to the inside of oreshoots as 1 ground preparation and nucleation 2 reinjection and sheeting 3 major fault movement channeling of fluid flow local dissolution and cracking and 4 consolidation and oreshoot growth including fluid stagnation and ponding

carbonate carbon isotope evolution of seawater across the ediacaran cambrian transition evidence from the keping area tarim basin nw china sedimentary rocks from the ediacaran cambrian boundary record important biological climatic and geotectonic changes during this time to date only few geochemical investigations on the upper ediacaran upper cambrian rocks in the tarim basin have been carried out here we report high resolution 13 c carb records from the penglaiba the wushi phosphorite and the dongergou sections from ediacaran cambrian series 3 in the keping area of the tarim basin the sections display several obvious 13 c carb shifts 13 c carb values increased from 3 to 6 7 across the qigebulage formation moreover a negative 13 c carb shift across the ediacaran cambrian boundary is apparent 13 c carb values decreased to a minimum of 9 8 in the wushi phosphorite section 7 7 in dongergou section and 5 4 in penglaiba section followed by a positive carbonate carbon isotopic excursion across the yuertusi formation into the middle of the overlying xiaoerbulak formation furthermore more or less invariable positive 13 c carb values characterize the middle and upper xiaoerbulak formation the most negative 13 c carb value 14 3 occurred near the base of the shayilik formation which is the absolute minimum value among the studied sections of the cambrian series 2 to cambrian series 3 transition in the world the 13 c data from keping tarim basin are in good agreement with carbon isotope profiles recorded in south china and these events may reflect the perturbation of the carbon cycle in the tarim basin during the ediacaran cambrian and the cambrian series 2 cambrian series 3 transitions

some problems concerning the precambrian cambrian transition and the cambrian faunal radiation in siberia the so called khailakh and manykay stages of pre tommotian age are inferred to be partly coeval with the type tommotian and to be based on a misunderstanding about the control of facies on faunal distributions evolutionary patterns are being studied through this interval using a variety of approaches synoptic reviews are presented on diversity changes on changes in skeletal composition and on archaeocyathan morphology the latter group appear to have originated on the siberian platform just prior to the tommotian and migrated globally during the atdabanian and botomian to form secondary centres of diversification olenellid trilobites may have dispersed in a similar pattern but other groups such as volborthella and relatives appear to have had a separate siliciclastic centre of origin the decline in diversity of small shelly fossils after the tommotian and the coeval expansion in archaeocyathans and trilobites may be related to basinal changes connected with the break up of palaeopangea

iron isotope fractionation during leaching of granite and basalt by hydrochloric and oxalic acids abstract transport of iron fe within hydrothermal and soil environments involves the transferral into aqueous solutions by leaching of complex polyminerallic rocks understanding the isotope fractionation mechanisms during this process is key for any application of the fe isotope system to biogeochemical studies here we reacted biotite granite and tholeiite basalt with 0 5 m hydrochloric acid and 5 mm oxalic acid solutions at ambient temperature solution aliquots were recovered over a seven day period and analysed for major and trace element concentrations and fe isotopic compositions in all experiments fe initially released into solution was isotopically lighter with 56fesolution rock as low as 1 80 in the granite hydrochloric acid system the oxalic acid experiments showed similar patterns but smaller fractionation in all experiments the 56fesolution rock reduced over time which would be in line with the formation of a leached layer as proposed before brantley s l liermann l j guynn r l anbar a icopini g a and barling j 2004 fe isotopic fractionation during mineral dissolution with and without bacteria geochim cosmochim acta 68 15 3189 3204 granite and basalts reacting with hydrochloric acid reached apparent steady state values of 0 60 0 15 and 0 40 0 20 respectively whilst experimental values with oxalic acid were 1 0 0 15 and 0 50 0 15 during the granite experiments alteration of biotite to chlorite followed by dissolution of chlorite were likely the dominant processes whilst in the basalt experiments dissolution of pigeonite was likely the principal source of fe variations in ph during the hydrochloric acid experiments were minimal remaining below 0 5 at all times in oxalic acid solutions the ph increased to over 4 leading likely to precipitation of secondary minerals and adsorption co precipitation of fe onto mineral surfaces these processes could contribute to the greater fractionation observed in the final stages of the oxalic acid experiments our results highlight the importance of mineralogy and fluid composition on the fe isotope systematics during weathering the fractionation processes identified for granites and basalts are in line with those inferred from field observations in soils sediments groundwater and hydrothermal deposits and from laboratory studies of single mineral leaching

the spatial distribution of mineralization applications of fry analysis the spatial distribution of mineralization is a foremost concern in regional exploration research and mine resource assessment here we use fry analysis as a complement to structural geology and geostatistical methods fry analysis uses a geometrical method of spatial autocorrelation for point data for n points there are n 2 n spatial relationships and because of the square function the method yields interpretable results with small as well as large data sets fry analysis is an alternative to variography for directional studies at the regional scale fry analysis can assess distribution patterns of mineralization and potential controlling structures at the deposit scale the characteristics of zones of mineralization such as direction spacing high grade ore direction and grade distribution can all be deduced

oxygen and carbon isotope stratigraphy of early cambrian carbonates in southeastern newfoundland and england carbonate rocks have been sampled through predominantly siliciclastic sediments above the precambrian cambrian global stratotype level in southeastern newfoundland to assess their potential for oxygen and carbon isotope stratigraphy comparable successions were sampled at nuneaton and comley in england greatly depleted 18 o signals are attributed to widespread thermal alteration during deep burial and granitic intrusion including within the stratotype region carbon isotope ratios appear to have been less affected and these are described from nine sections a provisional composite 13 c curve is based on non ferroan pink nodular and bedded micrites several 13 c excursions occur in the fossiliferous bonavista group and allow the position of the tommotian atdabanian boundary to be identified chemostratigraphic correlation of the new precambrian cambrian boundary stratotype may however prove difficult because of the lack of suitable well preserved carbonates the search must begin for a comparable reference section allowing global correlation of the boundary level using chemostratigraphy as well as biostratigraphy

examining the controls on gold deposit distribution in the swayze greenstone belt ontario canada using multi scale methods of spatial data analysis abstract understanding the spatial controls on mineral deposits is crucial in mineral exploration targeting this paper uses a combination of spatial data analysis techniques such as the distance distribution method fry nearest neighbor index ripley s k function multi distance fractal and kernel density analysis to better define controls on the distribution of gold deposits in the swayze greenstone belt ontario canada according to results obtained with the distance distribution method d2 structures were critical in controlling the spatial distribution of the gold mineralization with 97 of the gold deposits occurring within 7 km of these structures and 65 within 4 km fry analysis confirmed this spatial relationship with a close agreement between the orientations of the d2 structures and gold deposit alignment the outcome of ripley s k function cluster analysis suggests that gold deposits occur within 4 km distances of other gold deposits these findings are consistent with the results from the fractal analysis showing that gold deposit distribution is bifractal and that different geological features occurred at local 8 km scales we conclude that higher order d2 structures and lower order faults connected to the d2 structures acted as pathways to focus gold bearing hydrothermal fluids thus leading to the observed concentration and distribution of gold deposits at the regional to local scales

timing and structural controls on gold mineralization at the bogoso gold mine ghana west africa the bogoso gold deposit comprises 20 open pits scattered along 18 km of a major fault zone which separates birimian supergroup turbiditic sedimentary rocks to the northwest from tarkwaian group rocks to the southeast individual pits are centered on 200 to 400 m long ore shoots which are located in three broad structural settings steeply pitching relatively high grade orebodies are commonly localized in left hand dilational jogs in the strike of the controlling faults these jogs often coincide with intersecting minor faults gold is largely confined to the graphitic mylonite which defines the fault and imbricated slices of carbonate altered rock gently dipping mineralized quartz vein stockworks and disseminated auriferous pyrite and arsenopyrite form broader zones between more steeply dipping bounding faults in the vicinity of right hand bends and splays in these faults smaller zones of disseminated sulfide mineralization coincide with areas where bedding and or foliation in the adjacent birimian sedimentary rocks is strongly discordant with the adjacent mineralized fault generally where the faults cut the short limbs of tight upright east trending folds approximately 75 percent of the gold extracted from the bogoso district has been mined from a cluster of pits that coincides with the densest and most highly connected concentration of larger faults in the bogoso concession the majority of ore shoots are located along the largest of these faults the narrower faults generally host smaller and less frequent ore shoots the fault network originated during an early episode of regional scale shortening involving thrusting and isoclinal folding the structural setting and geometry of the ore shoots implies that mineralization occurred during a later minor episode of sinistral strike slip movement on the controlling faults after development of the fault network the undeformed nature of the auriferous sulfides implies that this was the last phase of ductile brittle deformation on the host faults this conclusion is consistent with earlier work indicating that the giant ashanti deposit 150 km along strike from bogoso also developed during a period of small displacement sinistral offset late in the history of the host fault network

geology geodynamics and orogenic gold prospectivity modelling of the paleoproterozoic kumasi basin ghana west africa abstract this paper describes the geology and tectonics of the paleoproterozoic kumasi basin ghana west africa as applied to predictive mapping of prospectivity for orogenic gold mineral systems within the basin the main objective of the study was to identify the most prospective ground for orogenic gold deposits within the paleoproterozoic kumasi basin a knowledge driven two stage fuzzy inference system fis was used for prospectivity modelling the spatial proxies that served as input to the fis were derived based on a conceptual model of gold mineral systems in the kumasi basin as a first step key components of the mineral system were predictively modelled using a mamdani type fis the second step involved combining the individual fis outputs using a conjunction product operator to produce a continuous scale prospectivity map using a cumulative area fuzzy favourability caff curve approach this map was reclassified into a ternary prospectivity map divided into high prospectivity moderate prospectivity and low prospectivity areas respectively the spatial distribution of the known gold deposits within the study area relative to that of the prospective and non prospective areas served as a means for evaluating the capture efficiency of our model approximately 99 of the known gold deposits and occurrences fall within high and moderate prospectivity areas that occupy 31 of the total study area the high and moderate prospectivity areas illustrated by the prospectivity map are elongate features that are spatially coincident with areas of structural complexity along and reactivation during d4 of ne sw striking d2 thrust faults and subsidiary structures implying a strong structural control on gold mineralization in the kumasi basin in conclusion our fis approach to mapping gold prospectivity which was based entirely on the conceptual reasoning of expert geologists and ignored the spatial distribution of known gold deposits for prospectivity estimation effectively captured the main mineralized trends as such this study also demonstrates the effectiveness of fis in capturing the linguistic reasoning of expert knowledge by exploration geologists in spite of using a large number of variables the curse of dimensionality was precluded because no training data are required for parameter estimation

spatial analyses of exploration evidence data to model skarn type copper prospectivity in the varzaghan district nw iran abstract recognition of significant ore forming processes which control mineralization improves the efficiency of mineral prospectivity modeling in this study controlling processes of skarn copper mineralization in varzaghan district northwestern iran were distinguished by a series of spatial and numerical analyses comprising point pattern fractal fry and distance distribution methods the recognized processes were then translated to a set of exploration criteria of the deposits in the area based on the accomplished exploration criteria two data driven models of skarn copper prospectivity were generated using logistic regression and random forest techniques the comparison of two generated models demonstrated that the targets derived by the latter technique were more reliable for further exploration than those created by the former one

tasman orogenic system a model for its subdivision and growth history based on gravity and magnetic anomalies the basement of the tasman orogenic system can be subdivided using gravity and magnetic anomalies into 11 geophysical domains the unity of each domain is given by subparallel trends which show the direction of the dominant tectonic structure in the nonsedimentary part of the upper crust basement crosscutting trends at domain boundaries indicate the relative ages of the domain cratonization these relative ages are consistent with the dated ages of first deformation and they show that cratonization occurred in numerous episodes and resulted in an apparent growth of the tasman orogenic system from west to east between the cambrian and the carboniferous each domain can be subdivided into bands of different character in the main area of basement outcrop the southern part of the lachlan orogen the position of the boundaries of these domains and bands agree with boundaries based on the composition of granites structure and strontium isotope ratios over the larger part of the tasman orogenic system where basement is under cover these geophysically defined domains and bands are our best estimate of basement subdivision and history near domain boundaries there are characteristic associations of gravity and magnetic anomalies due to reworking of the margin of the older crust by deformation intrusion and metamorphism differences between domains in mean upper crustal density and magnetization and the common occurrence of volcanic bands ophiolite serpentinite and deep elongate sedimentary troughs caused by crustal extension the domains can be divided into a sedimentary basement type formed by crustal extension and sedimentation or by the addition of an accretionary wedge and a volcanic arc basement type added by the accretion

stratigraphy structure and volcanic hosted mineralization of the mount windsor subprovince north queensland australia the mount windsor subprovince contains a major belt of mineralized cambro ordovician subaqueous volcanogenic rocks at the northern end of the tasman orogenic belt the base of the stratigraphic sequence is a thick continent derived siliciclastic package intruded by alkali andesites typical of intraplate settings this is overlain by massive subaqueous rhyolitic units and then by a mixed association of basaltic andesitic dacitic and rhyolitic volcanics and volcaniclastics containing numerous small elongate pods of quartz hematite or magnetite exhalite the cessation in active volcanism is marked by a change to a sandstone siltstone unit dominated by volcanic sources the majority of volcanics form a coherent group of low to medium k calc alkaline lavas similar to those in modern island arc settings extensional growth faults produced local variation in the stratigraphic thickness the largest growth fault in the area is close to the reward highway and handcuff deposits the sequence has been multiply folded and faulted in the paleozoic but the large scale structure remains relatively simple volcanic hosted massive sulfide vhms deposits occur at the top of the massive rhyolite and in the mixed volcanic package above it with the exception of the reward pyrite pipe the mineralization occurs as blanketlike deposits with low thickness lateral extent ratios the thalanga reward and waterloo deposits are copper rich whereas agincourt magpie liontown handcuff and warrawee are zinc rich and copper poor with a significant barite component

the fractal nature of structural controls on ore formation the case of the iron oxide copper gold deposits in the carajas mineral province brazilian amazon the formation of ore minerals in hydrothermal deposits is the result of a complex interplay between physical and chemical processes that are conditioned by the geologic environment in which they occur in the last decades research has increasingly indicated that many of these processes display different forms of scale invariance i e they show fractal geometry this suggests that behind the apparent disorder and irregularity of the geometry of mineral deposits at different scales an underlying regular pattern is present if properly understood this regular geometrical pattern could be useful in a variety of theoretical and applied fields a great portion of this scale invariance is given by the structural framework during mineralization because structures are a dominant factor controlling fluid flow here we assess the geometry of iron oxide copper gold iocg mineralization in the world renowned carajas mineral province focusing on one of the largest and most economically important orebodies the sossego deposit the geometry of mineralization is evaluated at the microscale ore minerals in thin sections local scale orebodies in mine maps and regional scale deposit distribution on regional maps we show that the spatial distribution and shape of ore minerals at the microscale is largely nonrandom presents fractal geometry and displays defined trends in spatial distribution and anisotropy additionally the geometric trends observed at the microscale mimic those of the local scale geometry of orebodies as well as the regional scale distribution of mineralization the main property controlling the observed scale invariance is permeability which is intrinsically associated with structures at multiple scales these results contribute to further understanding the fractal nature of processes controlling mineral deposit formation and revealing new multiscale approaches to investigate structural controls on ore deposition

carbon isotope stratigraphy of the precambrian cambrian sukharikha river section northwestern siberian platform a high resolution carbon isotope profile through the uppermost neoproterozoic lower cambrian part of the sukharikha section at the northwestern margin of the siberian platform shows prominent secul