self destructive sulfide segregation systems and the formation of high grade magmatic ore deposits the metal concentrations of sulfide liquids depend upon the mass of silicate magma that they are able to process for metals some high grade magmatic ni cu pge deposits and many magmatic platinum group element pge ni cu deposits demand very high magma sulfide ratios that seem improbable in the light of physical and kinetic constraints recent models for some high grade deposits invoke multistage upgrading processes in which an early formed sulfide liquid reacts with multiple later batches of silicate magma quantitative models of this open system process demonstrate that it is indeed more efficient than a closed system however it is likely that most later magmas in such a system will be sulfur undersaturated and will thus partly redissolve preexisting sulfide liquids further increasing metal concentrations in the remaining sulfide liquids this combined process is termed multistage dissolution upgrading and quantitative models show that it could reduce the mass of silicate magma that must be processed by as much as two orders of magnitude furthermore if sulfide liquids are extensively dissolved during enrichment their base metal concentrations will generally stabilize at a limiting value whereas their pge concentrations will generally increase without limit this divergence could account for unusually high pge concentrations and high pge base metal ratios in many pge dominated deposits the multistage dissolution upgrading model is tested using reasonable degrees of dissolution in the context of natural deposits in the noril sk area and the bushveld intrusion the models reproduce the observed sulfide compositions significantly better than previous models and are also consistent with other aspects of the geology of these deposits thus dynamic sulfide forming magmatic systems may be intrinsically self destructive but this apparently undesirable attribute could play an important role in forming high grade deposits however dissolution could lead to the complete destruction of sulfide liquids and the return of all metals to later magma batches in this case no sulfide deposit would remain but metal depletion signatures indicating sulfide liquid segregation would be preserved in rocks that crystallized from early magmas caution is therefore advised in the use of magmatic depletion signatures to infer overall mineral potential or to estimate the possible sizes of undiscovered magmatic sulfide deposits

geochemical and fluid dynamic modeling of compositional variations in archean komatiite hosted nickel sulfide ores in western australia stratigraphic volcanological petrological and fluid dynamic studies suggest that archean komatiite associated nickel sulfide deposits in western australia formed by thermal erosion of unconsolidated sulfidic sediments beneath channelized lava flows geochemical and nd isotope data for the type area at kambalda suggest that mineralized lava channels are less contaminated than barren flanking segments of the flow owing to high discharge rates and continuous replenishment within the channel this interpretation has several implications for the mode of emplacement of sulfides their degree of equilibration with the host komatiite and the compositions of sulfide ores 1 the solubility of sulfur in komatiite is relatively low so most of the sulfide in eroded sediments will be melted and remain as a dense layer at the base of the flow or be incorporated into the turbulently flowing komatiite as immiscible sulfide droplets 2 sulfide ores will not necessarily be in equilibrium with overlying komatiites but will record equilibration with variably contaminated lavas during initial stages of emplacement and crystallization and 3 ore compositions will vary from channel to channel shoot to shoot depending on i the composition of the hybridized komatiite ii the fluid dynamics of the system and the effective magma sulfide ratio r factor and iii the sulfide silicate partition coefficients under the prevailing conditions of temperature and f sub o 2 f sub s 2 the size of immiscible droplets and the interface between two immiscible layers are affected by inertial forces during turbulent flow turbulence causes coalescence of small droplets and breakup of large droplets leading to an equilibrium droplet size if the average size of the droplets is small and or the flowage rate is high they may be carried in suspension in the flowing komatiite droplets have a large surface area to volume ratio and will be effective in scavenging chalcophile elements since they are carried by the turbulent motion of the flowing komatiite if the average size of the droplets is large or if the flowage rate is low they will settle and collect at the base of the komatiite komatiite and sulfide liquids may continue to flow but the sulfide layer will have a low surface area to volume ratio and will be ineffective in extracting chalcophile elements from the overlying komatiite layer thus the initial stages of emplacement when sulfides are initially melted and are most likely to be in suspension if at all control the effective r factor and therefore the tenor of the sulfide ores numerical modeling of the observed variations in ore compositions constrained by known komatiite compositions and experimentally or empirically determined distribution constants indicates that the observed range of ore compositions in western australian komatiite associated nickel sulfide deposits can be accounted for primarily by variations in the effective sulfide silicate ratio 500 r 100 although required variations in the partition coefficient for ni 200 d ni 100 suggest that f sub o 2 f sub s 2 may also have varied systematically assimilation of h 2 o fes rich sediments should increase f sub o 2 f sub s 2 because of the relative abundances of the two components in the magma and unconsolidated sediments if low tenor ores represent equilibration at lower r and higher f sub o 2 f sub s 2 and high tenor ores represent equilibration at higher r and lower f sub o 2 f sub s 2 as suggested by the modeling then d ni appears to decrease with increasing f sub o 2 f sub s 2 as suggested by doyle and naldrett 1987 the range of calculated r values is relatively low suggesting that low tenor sulfides were not entrained into the komatiite lava but remained as a segregated layer at the base of the flow and that high tenor sulfides were not transported long distances in suspension but settled rapidly to the base of the flow magma compositions vary only slightly from an inferred parental komatiite low tenor ores appear to have equilibrated with only slightly more evolved contaminated and fractionated lavas

sulfur isotope exchange and metal enrichment in the formation of magmatic cu ni pge deposits sulfur isotope measurements provide a useful means of evaluating the source of sulfur in magmatic cu ni pge deposits although low sulfur pge rich deposits e g j m reef of the stillwater complex merensky reef of the bushveld complex show little or no isotopic evidence for the involvement of crustally derived sulfur several high sulfur deposits e g noril sk duluth complex show strong evidence for contamination of mafic magmas by sulfur of crustal origin processes such as magma degassing or redox changes accompanying crystallization are ineffective in significantly modifying sulfur isotope signatures of sulfides that crystallize from immiscible liquids that exsolve from the mafic magmas for this reason 34s values are primarily dependent on sulfur source characteristics and variations can often be treated using a two component mixing approach however deposits such as those at noril sk and voisey s bay that appear to have formed in magma conduit systems present another possibility for modification of sulfur isotope signatures these deposits are thought to have been upgraded in metal tenor by reaction with uncontaminated mantle derived melts that traversed the accumulated sulfide on their way to the surface our calculations illustrate the efficiency of reactions that involve the exchange of fe for cu ni or pge in producing increases in the metal tenor of the accumulated sulfide sulfur isotope exchange between the crustally contaminated sulfide ore accumulation and sulfur of mantle origin may accompany chalcophile element exchange and is capable of masking or limiting the degree of isotopic evidence for the initial stage of ore genesis that involved crustal sulfur sulfur isotope exchange is distinct from the addition of sulfur in the form of immiscible sulfide droplets from a sulfide saturated magma to the accumulated sulfide although both additive mixing and exchange can lead to similar isotopic effects stable isotopic exchange provides a mechanism in addition to additive mixing that may lead to decoupling of different isotopic systems

experimental investigation of morphological characteristics of rill evolution on loess slope abstract the development of rill is the result of a complex interaction of soil properties with high spatial and temporal variability the rill morphology may act as a determinant as well as a stochastically driven process the description of their complex morphology requires geostatistics and nonlinear theories a study of the morphological characteristics of rill evolution was performed via indoor soil pan rainfall simulations experiments were run with loessial soil bulk density of 1 25 g cm 3 under a rainfall intensity of 90 mm h with a 20 slope gradient a detailed scan of the slope topographic analysis and statistical analyses were the main methods utilized in the study statistical analyses showed that characteristic parameters exhibited differences in the expression of the dynamic change of soil loss according to the comparison of quantitative methods we found that the fractal dimension can reflect the complexity of rill network but it is not able to reflect the dynamic changes of the erosion process perfectly in contrast geomorphologic comentropy is sensitive to the dynamic changes of soil erosion intensity and its variation can reflect the dynamic changes of erosion perfectly the topological parameters can reflect the degree of stability in the rill network structure but it is not suitable for reflecting the dynamic changes of erosion intensity the geomorphologic comentropy was evaluated as the most appropriate characterization parameter for the rill morphology description

assimilation of sulfate and carbonaceous rocks experimental study thermodynamic modeling and application to the noril sk talnakh region russia most of the intrusions in the noril sk talnakh region siberia are hosted in thick sedimentary sequences including abundant evaporitic and terrigenous sedimentary rocks three mafic ultramafic intrusions in this region contain unusually thick massive sulfide deposits which represent one of the world s largest economic concentrations of ni cu and pge the interaction of siberian magmas with sulfate and organic matter rich sedimentary rocks has been proposed as a possible mechanism for the origin of these exceptional sulfide deposits but the interaction process and the reaction paths have never been fully investigated here we clarify by both experimental petrology and thermodynamic modeling how sulfate and organic matter assimilation occur in mafic ultramafic magmas affecting magma composition crystallization and sulfide saturation interaction experiments were conducted at conditions relevant to the emplacement of noril sk type intrusions 1200 c 80 mpa to simulate the assimilation of sulfate and or organic compounds by ultramafic magmas we used a picrite from noril sk1 intrusion and coal and anhydrite from the area as starting materials the experimental results show that the incorporation of anhydrite into the magma occurs by chemical dissolution in the melt which increases the magma s sulfur content but suppresses sulfide saturation and reduces olivine crystallization extreme assimilation leads to sulfate saturation in the magma and high dissolved sulfur contents of 0 9 0 1 wt s conversely coal assimilation promotes sulfide segregation and magma crystallization while decreasing the dissolved h2o content of the melt and increasing the amount of coexisting fluid phase we also employed gas melt thermodynamic calculations to quantify the effect of these assimilations on the redox conditions and the s content of the magma and investigate the role of temperature pressure and initial gas content of the magma in the assimilation process we quantify how sulfate assimilation strongly oxidizes the magma and increases its s content both effects are intensified by increasing pressure from 50 to 100 mpa in this study decreasing temperature from 1350 to 1200 c in this study and decreasing amounts of fluid phase initially coexisting with the magma from 2 to 0 wt the interaction with organic matter ch in this study induces a strong reduction of the magma even for extremely low degrees of assimilation few tenths of wt and the dehydration of the melt we therefore suggest that in the noril sk talnakh district 1 additional s was supplied to mantle derived magmas by the assimilation of evaporitic rocks and was transported during magma ascent in the form of dissolved oxidized s 2 a substantial reduction of the magma inducing sulfide segregation and important crystallization then occurred due to the interaction with carbonaceous sediments this mechanism can potentially produce massive sulfide deposits by important sulfate assimilation locally higher than 3 wt caso4 and minor organic matter assimilation few tenths of wt ch however if one of the two steps does not occur or the assimilation in 1 is not large enough disseminated sub economic or no sulfide deposits are produced we conclude that exceptional conditions favoring substantial assimilation of sediments are needed to generate exceptional ore deposits like those of the noril sk talnakh district

paleoecology of seabirds at nandao xisha islands south china sea sub fossil evidence for ashmole s halo during the little ice age abstract tropical seabirds play a key role in coral island ecosystems but there are still many uncertainties regarding their paleoecology seabird paleoecology was investigated on nandao island xisha islands south china sea from sub fossil remains spanning the past 800 years ornithogenic sediments were collected beneath seabird inhabited shrubs where a large number of seabird fish sub fossils were recovered we used reflectance spectroscopy to show that seabird population size was overall higher during the little ice age lia compared to periods before and after this event nonetheless the number of seabirds also fluctuated during the lia seabird populations on nandao reached their highest points at 1480 1550 and 1650 1800 ce respectively but the population remained low from 1550 to 1650 ce a large migration of seabirds from nandao island to the adjacent beidao island where the population size surged at that time is hypothesized to explain the corresponding decrease in the seabirds at nandao stable isotope 15n and 13c analyses also suggest a change in foraging behavior by seabirds at nandao during the period 1550 1650 ce seabirds at low population size foraged near the island and preyed upon smaller flying fish as inferred from low 15n and high 13c values in fish scales but fed upon larger flying fish farther from the island during times of high population this shift in foraging behavior is in accordance with predictions for ashmole s halo in that islands with high densities of birds will cause a depletion of resources near the colonies and force more distant foraging away from the colony

laboratory characterization and discrete element modeling of shrinkage and cracking in clay layer the performance of a variety of geostructures such as compacted clay liners earth dams and pavement embankments is compromised by soil cracking experiments are set up to monitor the drying pro

siderophile and chalcophile metals as tracers of the evolution of the siberian trap in the noril sk region russia abstract in this study cu ni and platinum group elements pge were determined in a sequence of basaltic and picritic lavas from the siberian trap in the noril sk area of russia to constrain genetic relationships between the basalts and the petrogenesis of ni cu pge sulfide deposits associated with the talnakh and noril sk intrusions in the most primitive basalts 8 19 wt mgo of the tuklonsky tk suite pt and pd concentrations range from 4 13 ppb increasing with decreasing mgo content whereas ir contents decrease with mgo from 0 8 0 05 ppb the contrasting behavior of these elements which all have very high sulfide silicate partition coefficients as well as the primitive mantle like ratios of cu y and pd y suggests that these magmas were not sulfide saturated the high pge abundances imply that their parental magmas were also not sulfide saturated during partial melting in the mantle due to sulfide segregation the overlying basalts of the nadezhdinsky nd series are low in cu and ni 52 and 38 ppm respectively highly depleted in all pge and have very low cu y pd y and pd cu ratios however in stratigraphically higher levels cu ni and pge concentrations increase systematically through the morongovsky mr suite to reach a concentration plateau in the uppermost mokulaevsky mk suite pt 8 ppb pd 9 ppb ir 0 12 ppb rh 0 4 ppb at the same time ratios such as cu y increase and approach primitive mantle values however ratios involving pge such as pd y remain low suggesting the removal of small amounts of sulfide 0 01 0 03 the compositional variations in the basalts and the sulfide liquids can be quantitatively described by fractional segregation of a sulfide liquid in an open or closed system magma chamber the latter model suggests that the basalts represent the eruption products of a zoned magma chamber in which light magma with crustal components contaminated overlies less contaminated denser magma crustal contamination caused sulfide saturation and the resulting sulfide liquids settled through a magma column and accumulated at the bottom of the chamber in this model the sulfide liquid is not in equilibrium with the whole magma mass and sulfide segregation is compared with the zone refining process of metallurgy the sulfides become more enriched as they move through the magma and although the magma left behind is depleted in pge cu and ni their concentrations also increase with depth eventually the magma chamber is emptied from the top to the bottom producing the flood basalt sequence and the associated intrusions and ore deposits in the open system model sulfide saturation was initially caused by assimilation of crustal material by the tuklonsky magma continuous and simultaneous replenishment assimilation and crystallization processes formed the lower nd lavas the concurrent removal of 0 5 1 sulfide strongly depleted these magmas in chalcophile and siderophile metals due to the continuous replenishment of the magma chamber with uncontaminated pge rich magma succeeding lavas mr mk show diminishing signs of crustal contamination and become less sulfide saturated as indicated by the increasing ni cu and pge abundances during the evolution of the chamber the magma remained sulfur saturated and sulfides accumulated at the base the composition of the sulfide ores could be regarded as a mixture consisting of low ni cu and pge sulfides derived with a low silicate sulfide ratio 100 from the tk nd magma and high ni cu and pge sulfides formed with a high ratio 10 000 from the mr mk magma

desiccation of a sensitive clay field experimental observations an excavation with three different levels was exposed to continuous evaporation during 35 days in order to observe and document the formation of shrinkage cracks in an intact and weathered sensitive marine clay desiccation of the intact saint alban clay under restrained conditions at an average evaporation rate of 0 018 cm h and an initial moisture content of 103 produced visible primary cracks after 17 h with an average spacing of 20 to 24 cm secondary cracks within each original polygon appeared after about 70 h of evaporation subhorizontal cracks at a depth of 6 to 8 cm were also created owing to differential strains induced by differential shrinkage of the soil polygons further evaporation resulted in the formation of a new set of vertical cracks after about 150 h of evaporation in the soil below the subhorizontal shear plane the shrinkage induced volume change associated with these different sets of cracks produced polygons with a protuberance at their bottom part indicating that the depth of crack propagation below the subhorizontal shear plane was about 3 to 4 cm in weathered clay at an initial moisture content of about 50 the average spacing was 10 to 12 cm indicating that spacing between primary cracks is related to soil type in the cohesionless topsoil no cracks were observed

kinetic controls on the partitioning of trace elements between silicate and sulfide liquids mass transfer between sulfide and silicate liquids is often discussed elements pge has resulted from liquation immiscible by reference to a mass ratio between hypothetical liquid reservoirs liquid phase separation of sulfide liquid from mafic or at equilibrium defined as r in an open system not at equilibrium ultramafic silicate magma a central assumption of modthe mass of silicate melt from which a growing sulfide droplet els of magmatic sulfide deposit formation is that the base appears to have scavenged chalcophile elements will depend on metals and pge are strongly partitioned into the sulfide diffusivities di and dfes of the element and of the fes component melt previous discussions of the process by which sulfide in the silicate melt respectively on the degree of supersaturation of liquids become enriched in chalcophile metals have fothe melt with fes c o on the radius a of the droplet and on the cused almost exclusively on models in which coexisting velocity v with which the droplet is advected through the melt so bodies of sulfide and silicate melt are considered to be that in equilibrium at all times the intent of this paper is to demonstrate that natural sulfide deposits preserved in igneous rocks will in many r 1 c fes o di 1 2 adiv dfes 1 2 adfesv instances record metal distributions that never attained equilibrium as a result of the kinetic constraints on metal chalcophile elements are expected to show inter element variations partitioning between phases the consequences are that in d spanning several orders of magnitude in some melts leading different elements will seem to show evidence for equito large inter element variations in effective r in a given sulfide libration at different silicate sulfide mass ratios within body these variations in effective r will lead to spatial separations single sulfide bodies i describe the time dependent evolubetween zones of maximum enrichment of chalcophile elements tion of metal distributions in silicate sulfide melt systems produced during fractional segregation of sulfide in layered intrusions starting with analytical solutions for simple boundary whereas it has proven impossible to model the generation of spatially conditions and then adapting them to more complex offset stratiform horizons in the australian munni munni layered systems as numerical models intrusion using equilibrium partition coefficients the present kinetic model reproduces the observed patterns with great fidelity

syneresis cracks subaqueous shrinkage in argillaceous sediments caused by earthquake induced dewatering abstract syneresis cracks often confused with subaerial desiccation phenomena are traditionally ascribed to subaqueous shrinkage whereby salinity changes caused deflocculation of clay this and other previously proposed mechanisms fail to account for their occurrence in low energy typically non evaporitic facies stratigraphically sporadic distribution intrastratal formation under shallow burial depths variation in morphology degree of contraction generation of sedimentary dikelets as crack fills and deformation of dikelets and enclosing layers instead it is suggested that ground motion from strong synsedimentary earthquakes caused argillaceous sediments to dewater interbedded sands and silts to be almost simultaneously liquefied and injected into the resulting fissures and then these dikelets to be distorted comparative rarity of syneresis cracks in phanerozoic versus precambrian marine strata is considered to be primarily an evolutionary consequence of theological changes caused by increased organic binding of clay flocs in the water column greater input of organic matter into the sediment and the diversification of sediment dwelling bacteria and meiofauna in phanerozoic deposits

separation of sulfide melt droplets in sulfur saturated silicate liquids this experimental study explores the controls of run duration oxygen fugacity silicate melt structure and sulfide melt composition on the size of sulfide melt droplets that generate in sulfur saturated silicate liquids the sizes of the formed sulfide melt droplets influence the physical behavior of the separate sulfide phases during magma evolution within the earth s mantle and crust the relative enrichments of rh pt and pd in the primitive mantle melts and of os ir and ru in mantle residue mirror the physical and geochemical behavior of sulfide droplets that are finely dispersed in silicate melts and get entrained by ascending primitive mantle melts hypotheses that are based on kinetic constraints to model the formation of the magmatic sulfide deposits of kambalda and sudbury can be reinforced by the expected physical behavior of separate sulfide phases within the parental magmas of the magmatic deposits while formation scenarios of the deposits of bushveld and skaergaard remain ambiguous when combining kinetic constraints with expected physical behavior of separate sulfide phases within the parental magmas

fractal analysis of cracking in a clayey soil under freeze thaw cycles abstract under extreme climate conditions clayey soils experience not only seasonal drying and wetting but also frequent freezing and thawing cracking would also occur in clayey soils under freeze thaw cycles but now less academic attention has been paid on this issue in this study a series of laboratory tests were conducted on a clayey soil to investigate the cracking behaviors under freeze thaw cycles water loss surface crack initiation and propagation processes were monitored after each freeze thaw cycle by using the image processing technique the crack patterns were described and then quantitatively analyzed on the basis of the fractal dimension concept it was found that for the tested clayey soil subjected to freeze thaw cycles the surface crack pattern slowly evolves from an irregularly rectilinear pattern towards a polygonal or quasi hexagonal one and the water loss closely related to the sample thickness plays a significant role in the process of the clay cracking upon cyclic freezing thawing the fractal dimension is well correlated to the surface crack ratio in a logarithmic equation fractal dimension concept can offer a new perspective on the quantitative understanding of cracking initiation and propagation in clayey soils under freeze thaw cycles

field relations and strontium isotope systematics of the marginal rocks of the eastern bushveld complex the well exposed basal contact of the eastern bushveld complex was mapped at scales of 1 10 000 and 1 20 000 along 130 km of strike and through a 9 km vertical section field relations petrography and geochemistry of the marginal rocks and associated sills have aided their subdivision into two main groups a broadly pyroxenitic group rims the complex from its base to the top of the pyroxenitic subzone of the critical zone a gabbroic group occurs above this level each group consists of a number of closely related rock types most of which have sill analogs rocks of the first group b1 include pyroxenites norites and peridotites all of which may have quench textures all contain orthopyroxene en 78 plagioclase an 65 and chromite with subordinate clinopyroxene and biotite rare earth element patterns are mostly strongly fractionated ce n yb n approximately 10 and have 40x chondritic abundances at ce their initial strontium isotope ratios at 2 05 b y fall in the range 0 7032 to 0 7057 and rb sr ratios approximate 0 2 the gabbroic group consists of microcrystalline two pyroxene gabbros b2n and b3n and their coarser grained equivalents b2 and b3 that border the upper critical and main zones respectively mineral assemblages are dominated by plagioclase approximately an 55 clinopyroxene and orthopyroxene approximately en 63 with abundant magnetite and traces of ilmenite and biotite their rare earth element patterns are less fractionated than b1 rocks the b2n and b2 family have ce n yb n approximately 6 and 30x chondritic abundances at ce the b3n and b3 rocks have ce n yb n approximately 3 6x chondritic abundances at ce and pronounced positive eu anomalies strontium isotope initial ratios at 2 05 b y fall in the range 0 706 to 0 708 and the rb sr ratios are approximately 0 02 whole rock and sr isotope compositions of the peridotitc sills can be successfully simulated by a model involving olivine fractionation from a liquid with an initial sr isotope ratio r 0 similar to that of the transition zone 0 7056 a fraction of such liquid enriched in cumulus olivine crystals when mixed with up to 30 percent of a pyroxenitic liquid with low r 0 0 7034 yields a product having the isotopic and compositional characteristics of the peridotite sills a continuum exists in the initial sr ratios through the pyroxenitic and gabbroic marginal rocks suggesting that these represent mixtures of at least two sources with distinct initial sr isotope ratio characteristics it is argued that neither magma aging nor crustal contamination adequately accounts for the sr isotope characteristics of the marginal rocks or their derived cumulates the unusual chemistry of the pyroxenitic early liquids sio 2 approximately 55 mgo approximately 13 coupled with high concentrations of incompatible elements should be considered primary

an experimental study of the influence of oxygen fugacity on fe ti oxide stability phase relations and mineral melt equilibria in ferro basaltic systems

image analysis and fractal geometry to characterize soil desiccation cracks the rapid transport of water and solute through desiccation soil cracks can lead to crop water and nutrient stress as well as ground and surface water contamination the objectives of this research were to determine 1 soil surface crack area 2 fractal dimension of crack edges d1 and 3 mass fractal dimension d2 and lacunarity of soil surface cracks photographs were used to record in situ soil cracking in a mexico silt loam fine smectitic mesic vertic epiaqualf at two locations for three sampling dates photographs of the cracks were digitized and an algorithm was developed to determine crack area and the fractal dimension and lacunarity of the digitized images location 1 produced 7 crack area a mass fractal dimension d2 of 1 44 and a crack edge fractal dimension d1 of 1 08 location 2 produced 25 crack area a mass fractal dimension d2 of 1 64 and a crack edge fractal dimension of 1 08 d1 lacunarity curves as a function of box size for crack boundary fractal dimension were more variable at location 2 soil profile moisture content and texture analysis indicated the presence of an argillic horizon at the 20 cm depth at location 1 while at location 2 the argillic horizon was exposed to the soil surface photographic image analysis techniques and fractal analysis appear to distinguish differences in crack area and patterns which may be useful in characterizing soil cracking

horizontal and vertical variations in noble metal distribution in the great dyke of zimbabwe a model for the origin of the pge mineralization by fractional segregation of sulfide abstract a study based largely on diamond drilling undertaken specifically for research purposes has shown that in the darwendale subchamber of the great dyke of zimbabwe there are three principal sulfide zones that are located in subunits 1a and 1b of cyclic unit 1 sulfide zone 1 the main sulfide zone msz is subdivided into three subzones the base of the msz occurs at the top of the main bronzitite layer of cyclic unit 1 extending into the overlying websterite the noble metals are concentrated at the bases of each sulfide zone and subzone and decrease in concentration rapidly upwards whereas variations in the concentrations of base metals such as cu correlate well with variations in the amounts of sulfide across each zone when calculated in terms of their concentration in 100 sulfides it is found that pd decreases upwards most rapidly followed by pt and then au with the cu concentration remaining essentially constant the decrease of the noble metals is interpreted in terms of simple rayleigh fractionation as the consequence of the removal of sulfide the observed correlation between the tops and bottoms of sulfide zones with small variations in the mg number of bronzite is taken to indicate that in zones 2 and 3 sulfide segregation started as a result of crystallization increasing the s content of the resident magma in the chamber until it reached that of sulfide saturation coupled with fresh inputs of sulfide unsaturated more primitive magma causing the resident magma to become unsaturated again this recharge by primitive magma also raised the pge content of the sulfides segregating from the trapped intercumulus liquid indicating that the resident magma was becoming recharged in pge in this way subunits i and ii of sulfide zone 1 are thought to contain too much sulfide to be explicable in this way and it is suggested that mixing with a plagioclase saturated magma possibly generated around the flanks of the intrusion was responsible for these subunits the sulfides of each of the sulfide zones are more concentrated at the margin than at the axis of the great dyke but have a lower tenor of noble metals it is proposed that the axially located sulfides were the consequence of magma sulfide equilibration at a higher r factor magma sulfide ratio than those at the margin the magma sulfide partition coefficients required to explain the percentage difference in the tenors of the different noble metals between axis and margin in this way are the same as those required to explain the vertical variations in noble metal tenor in terms of the fractional segregation model

mechanical behavior and fracture spatial propagation of coal injected with liquid nitrogen under triaxial stress applied for coalbed methane recovery abstract fracturing technology through liquid nitrogen ln2 injection alters the physical properties of coal and rock masses because of the thermal and pressure effects in order to investigate heat transfer and fracture propagation behaviors under in situ geological condition with ln2 injections experimental work was conducted to study the ln2 induced rock coal failures under true triaxial stress conditions during the experiments the temperature ultrasonic waves and acoustic emission location detection were monitored to determine the intensity and complexity of specimen failure under singular or cyclic ln2 injections the results show that a single ln2 injection mainly transfers heat through the solid skeleton and only damages areas adjacent to the injection tube however cyclic injections formed a propagated fracture network and the heat can sequentially transfer further along the induced fractures moreover plastic deformation occurred in the entire volume of the sample and the main fractures coalesced until the sample failed based on the spatial locations of the acoustic emission sources the dynamic fracturing within the sample progressed after ln2 injection was clarified the experimental results can provide evidences for the proposed crack propagation model for the coal masses the research revealed that high pressure nitrogen gas transferring liquid water to the tips of new fractures is essential for cyclic ln2 injection to form effective frost heaving forces and fracturing therefore the fracturing efficiency of the cyclic ln2 injection is far higher than that of singular ln2 injections

platinum group element and nickel sulphide ore tenors of the mount keith nickel deposit yilgarn craton australia a set of platinum group element pge analyses of about 120 samples from a 250 m continuous drill core through the mount keith komatiite hosted nickel orebody combined with ni cu co s and major elements reveals a complex trend of covariance between the original cumulus components of a thick sequence of nearly pure olivine sulphide liquid adcumulates the intersection is divided into informal chemostratigraphic zones defined primarily by combinations of fine scale cyclicity in original olivine composition defined by mg and sulphide composition defined by pt s and ni s contents of ni and pge in 100 sulphides tenors were determined from linear regressions of the ni s and pge s covariance for each zone inferred olivine compositions range from about fo92 to fo94 6 and show a broad decrease from bottom to top of the sequence complicated by numerous reversals revealing crystallisation in an open conduit system ni and pge tenors of mount keith sulphide ores have typical values similar to the type i deposits of the kambalda dome mobility of s at least on the scale of 2 m sample composites is evidently relatively minor tenors for the various zones range 12 22 ni 370 1540 ppb pt 970 3670 ppb pd 100 460 ppb ir 170 460 ppb rh and 710 1260 ppb ru pt pd and rh tenors are very strongly correlated but the iridium group of platinum group elements ipges ir and ru less so tenor variations are predominantly controlled by variations in magma sulphide ratio r 100 350 with a minor component of variance from equilibrium crystallisation trends in the parent magma pge depletion in the silicate melt due to sulphide liquid extraction is limited by entrainment of sulphide liquid droplets and continuous equilibration with the transporting silicate magma ratios of the pges to one another are similar to those in the host komatiite magma with the exception of pt which is systematically depleted in ores relative to rh and pd and relative to host magma by a consistent factor of about 2 to 2 5 this anomalous pt depletion relative to pge element ratios in unmineralized komatiitic rocks matches that observed in bulk compositions of many komatiite hosted orebodies the highly consistent nature of this depletion and particularly the very strong correlation between pt pd and rh in the mount keith deposit argue that this depletion is a primary magmatic signal and not an artefact of alteration differential diffusion rates between pt and the other pges giving rise to a low effective partition coefficient for pt into sulphide liquid is advanced as a possible but not definitive explanation

compositional variations within and between five sudbury ore deposits recent work on the platinum group element pge content in ni sulfide ores has shown that those associated with komatiite magmas generally have low pt pd ru ir os ratios 13 the levack west and little stobie 1 and 2 deposits conform with this generalization having ratios of 18 6 19 2 and 13 2 respectively hoffman et al 1979 pt and pd are present in roughly equal proportions in these deposits ranging between 1 000 and 3 000 ppm in massive sulfides new data from the strathcona deposit indicate values of close to 400 ppm for both pt and pd approximately one third of the levels at the nearby levack west deposit both strathcona and levack west are strongly zoned with respect to platinum group elements au and base metals cu ni zn pt pd and au increase away from the irruptive hanging wall into the footwall and co rh ru ir and os increase in the reverse direction at strathcona this zoning results in a decrease of the pt pd ru ir os ratio from 132 in the footwall to 2 2 in the hanging wall ore relevant phase equilibria data indicate that cu ni zn pt and pd are likely to become enriched in the residual liquid of a fractionating sulfide melt whereas co rh and ru will concentrate in the early crystallizing monosulfide solid solution the correspondence between the experimental data and natural observations is strong evidence that the zoning is the consequence of the fractionation of a sulfide melt with the residual liquid being expelled progressively into the footwall average data obtained for the falconbridge depost resemble those of the hanging wall at strathcona both in the low pt pd ru ir os ratio of 2 3 and in a low cu ni ratio suggesting that the ore sampled represents an early crystallizing fraction and that a late crystallizing pt rich fraction equivalent to the footwall ore at strathcona and amounting to perhaps twice the present volume of ore was not included in the sampling and may well not be within the present orebody the deposit is located largely within a vertical fault zone it is possible that the sulfide melt was introduced up the fault crystallizing as it moved upward and that the pt rich portion crystallized farthest up the fault and has been removed by erosion however sampling over a 1 600 m vertical interval of the ore zone has failed to reveal any progressive variation in the pt pd ru ir os ratio within the fault zone an alternative and preferred hypothesis is that the deposit was originally zoned as at strathcona with the pt rich portion forming away from the irruptive within the footwall this portion may have been faulted off leaving the early crystallizing portion behind to become remobilized into the fault zone if true the present location of the pt rich portion is intriguing in addition to having lower concentrations of platinum group elements than levack west the strathcona deposit also has lower concentrations of ni and cu these compositional differences can be modeled in terms of a larger amount of sulfide equilibrating with a given amount of the host silicate magma at the former deposit than at the latter sequences of similar magmatic events coupled with a proposed fractionation of olivine can account for many of the compositional variations between different sudbury deposits

late stage sulfide liquid mobility in the main mass of the sudbury igneous complex examples from the victor deep mccreedy east and trillabelle deposits massive sulfide in the contact sublayer in three different deposits of the sudbury igneous complex is overlain by substantial thicknesses of norite hosted disseminated sulfide mineralization with anomalous compositions in the trill embayment the levack trough mccreedy east and the victor nickel rim embayment victor deep disseminated sulfides are present at concentrations of 1 to 5 percent over a vertical thickness locally exceeding 100 m within the main mass i e texturally homogeneous inclusion free norites above massive contact ores of the sublayer where primary textures are preserved they show that sulfide liquid remained present as an interstitial liquid during the entire crystallization history of the enclosing silicate cumulate rocks the disseminated sulfides show remarkably constant compositions over a large stratigraphic interval they cannot have formed due to fractional segregation of sulfide liquid from the main mass magma accompanying the deposition of the enclosing silicate cumulus phases because this would lead to extreme depletion in all platimun group elements within a stratigraphic interval much shorter than the hundreds of meters in which their compositions are observed to remain approximately constant geochemical modeling of sulfide liquation and fractional crystallization shows that the massive sulfides are cumulates rich in monosulfide solid solution mss the overlying disseminated sulfides represent mss left behind by an upward migrating fractionated sulfide liquid residual to the formation of the massive cumulates at the base these results show that cu rich sulfide liquids are capable of migrating distances greater than 100 m through almost completely solidified cumulate rocks at volume fractions of sulfide as low as one percent the presence of a halo of disseminated sulfide mineralization with a distinctly fractionated geochemical character up to several hundred meters wide above zones of massive sulfide mineralization could be used to detect deeply buried massive sulfide orebodies at sudbury and elsewhere

layering and precious metals mineralization in the rincon del tigre complex eastern bolivia geologic investigations supporting recent technically successful platinum exploration of the rincon del tigre complex a ca 4 6 km thick layered sill have provided significant new understandings of the layering development and precious metals mineralization of one of south america s largest mafic ultramafic intrusions three macrocyclic units are recognized from the base up basal unit unit 1 and unit 2 each most likely the product of a major replenishment with mafic magma of one compositional type the ultramafic rocks of all three macrocyclic units largely comprise repeated minor cyclic units of poikilitic harzburgite granular harzburgite olivine bronzitite each a few meters thick with occasional development of bronzitite at the top mafic rocks absent from unit 1 and present only locally in the basal unit form a well developed norite gabbro magnetite gabbro sequence in the upper half of unit 2 associated with the base of the magnetite gabbro is the precious metals zone a persistent zone of low grade subeconomic sulfide and precious metals mineralization 80 to 185 m thick the precious metals zone comprises an upper cu sulfide rich portion its base the sulfide phase boundary about 23 to 70 m above the magnetite phase boundary and a lower precious metals rich portion the lower part straddling the magnetite phase boundary the individual precious metals are concentrated in separate sulfide poor subzones each up to many tens of meters thick in the stratigraphic order rh pt pd au with peak offsets at the same scale modal layering of silicates and magnetite is well developed in the mafic rocks as is modal and cryptic precious metals layering of the sulfides in the precious metals zone all at three different superimposed scales from about 3 m to several tens of meters a possible interpretive framework for the cryptic layering and perhaps for much of the other layering including the meter scale layering of the ultramafic rocks is provided by the likely compositional stratification of the resident magma initiated by the fluid dynamics of the replenishment and mixing processes and in the magnetite gabbro by repeated convective overturns caused by the onset of magnetite precipitation the characteristics of the precious metals zone fit an orthomagmatic model the composition stratigraphic relations and modal correlation with magnetite of the sulfides all imply that s saturation was induced by loss of feo to magnetite precipitation this took place after prolonged closed system fractionation following the last major magma injection at the base of unit 2 during which crystallization of olivine pyroxene plagioclase and finally magnetite precipitation led to overall s cu and precious metals enrichment and ni and finally fe depletion of the magma the development of the mineralization and its complex layering was controlled by sulfide segregation rayleigh fractionation the different but generally very high partition coefficients dsilicate sulfide for each precious metal and repeated convective overturns at three different superimposed scales the decoupled metals distribution is analogous and similar in origin to that of the main sulfide zone of the great dyke zimbabwe and of the main sulfide layer offset portion of the munni munni complex western australia but the stratigraphic order of metal enrichment peaks is different pt pd au vs pd pt au this suggests a reversal in the relative magnitudes of the partition coefficients dpt and dpd that was possibly brought about by changes in the temperature and o s and fe activities of the magmas between the middle and late stages of crystallization constancy of d values during fractionation of mafic magma should not be assumed the precious metals zone is one of several skaergaard type strata bound precious metals zones associated with magnetite gabbros in the upper levels of many layered intrusions and the origin of the skaergaard mineralized zone itself including the potentially economic platinova reefs can be explained in terms of the precious metals zone model presented here the very low grade great thickness and wide separation of individual metal subzones in the precious metals zone are similar to those of the subeconomic axial facies of the main sulfide zone in the wider parts of the great dyke cf the economic more compact marginal facies on the basis of the lateral and vertical thermal model of the great dyke magma chamber the subeconomic status of the precious metals zone may be in large part a function of the specific fluid dynamics of the rincon del tigre magma chamber

komatiites and nickel sulfide ores of the black swan area yilgarn craton western australia 4 platinum group element distribution in the ores and genetic implications the black swan komatiite sequence in the eastern goldfields province of the archaean yilgarn craton in western australia is a body of dominantly olivine rich cumulates with lesser volumes of spinifex textured rocks interpreted as a section through an extensive komatiite lava flow field the sequence hosts a number of nickel sulfide orebodies including the silver swan massive shoot and the cygnet and black swan disseminated orebodies the massive sulfide orebodies of the black swan succession are pervasively depleted in all platinum group elements pges particularly pt and pd despite very high ni contents this depletion cannot be explained by r factor variations which would also require relatively low ni tenors the pge depletion could be explained in part if the ores are enriched in a monosulfide solid solution mss cumulate component but requires some additional fractional segregation of sulfide melt upstream from the site of deposition the silver swan orebody shows a remarkably consistent vertical zonation in pge contents particularly in ir ru rh os which increase systematically from very low levels at the stratigraphic base of the sulfide body to maxima corresponding roughly with the top of a lower layer of the orebody rich in silicate inclusions platinum shows the opposite trend but is somewhat modified by remobilisation during talc carbonate alteration a similar pattern is also observed in the adjacent white swan orebody this zonation is interpreted and modelled as the result of fractional crystallisation of mss from the molten sulfide pool the strong ipge depletion towards the base of the orebody may be a consequence of sulfide liquid crystallisation in an inverted thermal gradient between a thin rapidly cooling upper rind of komatiite lava and a hot substrate

fractal analysis of temperature induced cracking in clays and rocks because of their low hydraulic conductivity clays have been used as a hydraulic barrier to the flow of rainwater into landfills similarly rocks have been used as depository sites for nuclear waste high temperatures resulting from climatic fluctuations for clays or from heat generated by nuclear waste for rocks can have detrimental effects on their hydro mechanical properties causing cracking in clays this is the result of desiccation in rocks it is the result of varying expansion between mineral grains the present study deals with the evolution and interconnectivity of cracks in clays and rocks as a result of high temperatures evaluated using the fractal dimension concept

cracks bifurcation and shear bands propagation in saturated clays discontinuities in the form of cracks or fissures and inclusions are often present in natural clays they serve as stress concentrators when loads are applied to the material such concentrations result in cracks advancing often surrounded by and preceded by a propagating damage zone as cracks propagate the damage may be in the form of one or more shear bands which may play the part of new stress concentrators and blunt the action of the original crack this paper examines some of the phenomena associated with cracks in over consolidated clays and normally consolidated clays differences between isotropic and anisotropic materials and the level at which serious modifications take place in the fabric of the material are noted the influence of the cracks and the shear bands on the kinematics and strength of the test specimens is discussed des discontinuites sont souvent presentes sous forme de fractures fissures et inclusions dans les argiles naturelles elles jouent le role de concentrateurs de c

resurfacing time of terrestrial surfaces by the formation and maturation of polygonal patterned ground 1 to help interpret the polygonal patterned ground on mars we present recent findings about a similar form of patterned ground in a particularly cold and arid region on earth the dry valleys of antarctica in this region distinct arrays of interconnected polygons which we refer to herein simply as patterned ground characterize many surfaces reflecting a subsurface network of interconnected subvertical wedges of sand that grow incrementally as sand progressively fills soil fractures the fractures form initially as thermoelastic stresses arise during periods of rapid cooling of frozen ground and they continue to open and close in response to thermal cycles we describe the initiation and maturation of the patterned ground using data for the growth of sand wedges and for the evolution of crack patterns and microrelief over time scales ranging up to 106 years

cracking and vertical preferential flow through landfill clay liners abstract cracking is a major concern in the long term performance of landfill clay liners cracking of clay liners is affected by the roots of the vegetation planted to control erosion while vegetation roots may restrict cracking they may introduce preferential flow through the liners the impact of vegetation roots on the hydraulic properties of clay liners remains unclear this study investigates the effect of vegetation roots on crack formation and preferential flow through clay liners three experimental soil columns were used to observe crack formation by exposure to the weather and to measure the flow through them caused by artificial rainfall the clay in each column was compacted to 90 relative compaction the first column was not vegetated and no crack developed in it the second column was vegetated and underwent drying wetting cycles outdoor the third column did not have vegetation but underwent drying wetting cycles outdoor cracks developed in the second and third columns due to the exposure to the weather image analysis in the experimental soil columns revealed that vegetation roots restricted crack formation especially in the early stages of drying wetting cycles infiltration tests performed on the experimental soil columns showed that the unsaturated hydraulic conductivity of the vegetated soil in the second column was respectively about two orders and one order of magnitude larger than those of the soils in the first and third columns the experimental results imply that the effect of vegetation roots on the preferential flow through landfill clay liners should be considered in practical designs

simplifying drill hole domains for 3d geochemical modelling an example from the kevitsa ni cu pge deposit abstract a 3d geology model is a simplified version of the true geology designed to give a visual summary of the geometry and distribution of major geological elements in a specified region drill holes provide detailed data of the subsurface that can be classified into geological units that are the fundamental elements of the 3d model due to software limitations upscaling lumping is usually required to reduce the number of geological units in the drill holes prior to model building upscaling is a subjective process which means that different geologists will group in different ways and will typically not record the rationale behind their decision this means the experiment is not reproducible in our study we use a method of upscaling geological units in this case based on assay data using the continuous wavelet transform cwt and tessellation methods this method reduces subjectivity and can easily be repeated e g on an updated or new drill hole by using the same parameters ensuring that the upscaling process is consistent over all drill hole data we apply this technique to a large assay database 90 000 samples from the kevitsa nickel copper platinum group element pge deposit in finland the kevitsa ni cu pge disseminated sulfide orebody is hosted in a proterozoic layered intrusion in northern finland internal geological subdivision and correlation within the intrusion is very difficult to do consistently using lithological observations owing to general homogeneity of rock types and an overprint of alteration but distinct variability is evident in ni and pge sulfide tenors in its raw form the tenor variation dataset appears noisy and unsystematic we have applied the tessellation method to classifying ore types based on tenor variations consistently and objectively reducing the number of units in each drill hole to create a simplified 3d model of the orebody our results reveal shallow inward dipping cryptic layering defined by sulfide composition which are interpreted as reflecting an increase in ni and pge tenor with time during emplacement of the sulfide bearing cumulates we interpret this as a progressive increase in silicate sulfide mixing efficiency r factor as the intrusion developed from an interconnected sill sediment complex choked with country rock inclusions into a freely convecting magma chamber based on this case study we show that the tessellation method can add considerable value by distinguishing the wood from the trees in large 3d geochemical databases the method may be widely applicable in other ni cu pge deposits where tenor variations appear at first sight to be chaotic and uninterpretable

geology and geochemistry of intrusions and flood basalts of the noril sk region ussr with implications for the origin of the ni cu ores geochemical studies indicate that five principal magma types characterize the 3 8 km vertical thickness of flood basalt of the noril9sk region from base to top these are 1 a fractionated type with alkalic affiliations ivakinsky and syverminsky 2 an ni rich suite including picritic basalt gudchichinsky 3 a primitive but ni depleted suite with fiat rare earth element ree profiles and also including picritic basalts tuklonsky 4 a light ree enriched crustally contaminated suite lower nadezhdinsky nd 1 above 4 there is a transitional suite upper nadezhdinsky nd 2 and morongovsky mr 1 and mr 2 which is overlain by the fifth type a second primitive suite without picrites mokulaevsky similar but not identical in its chemistry to the tuklonsky type this is followed by tuffs and basalts of the kharayelakhsky kumginsky and samoyedsky suites which are largely composed of similar uncontaminated tholeiitic magma the latter three suites have not been studied by us intrusions of the region fall into five main groups 1 alkalic intrusions 2 ti rich dolerite dikes 3 dolerite sills and dikes 4 differentiated bodies not related to ore junctions and 5 differentiated bodies related to ore junctions the ni cu ores are associated with ni and cr rich type 5 olivine rich intrusions with flat ree profiles that are geochemicaly similar to the mokulaevsky magma light ree enriched ni and cr poor olivine rich type 5 intrusions with uneconomic mineralization occur closely associated with the strongly mineralized variants and resemble geochemically the basalts transitional between the lower nadezhdinsky and upper morongovsky they are cut by the strongly mineralized bodies indicating that the latter are of late morongovsky to mokulaevsky age the mineralized intrusions are associated with about 1 5 to 1 10 of their mass in sulfides this is a factor of 25 to 50 more than could have been carried in solution and deposited by in situ liquation from the magma of these intrusions the platinum group element pge concentrations in the ores require that the sulfides giving rise to them equilibrated with 15 to 200 times more magma than is represented by the intrusions much of the ore is very massive and crosscuts the host intrusions the sequence of igneous activity and mineralization in the immediate vicinity of noril9sk and talnakh from the base of the nadezhdinsky upward is thus interpreted to be 1 extrusion of highly crustally contaminated ni and cu poor basalt 2 extrusion of a series of basalt flows each progressively less contaminated and less ni and cu depleted than the preceding one accompanied by intrusion of contaminated ni depleted magma with weak mineralization 3 extrusion of uncontaminated ni and cu rich basalt accompanied by intrusion of uncontaminated ni rich magma with strong mineralization followed very closely by introduction of associated massive ore and 4 continued extrusion of ni and cu rich basalt it is proposed that crustal contamination of the original ni and cu rich magma occurred at the top of a vertically extensive fault controlled magma chamber and caused segregation of immiscible sulfides with a low r factor these depleted this magma in chalcophile elements and settled deeper in the chamber as they settled they reacted with less contaminated magma scavenging additional chalcophile elements they finally came to rest near the base of the chamber to form a zone of sulfide and thus chalcophile element enriched magma eruption and in some instances intrusion of progressively stratigraphically lower less contaminated and thus less depleted layers in the chamber gave rise to the observed sequence of basalts and intrusions the answer to the strong enrichment in ni cu and pge associated with the ore bearing intrusions is that these metals came from the magma that is now represented by the depleted basalts

magmatic sulfide formation by reduction of oxidized arc basalt the hidaka metamorphic belt in southeastern hokkaido japan provides insights into how magmatic sulfide deposits may form through magma mixing deep within arcs here a near complete cross section of arc crust is exposed with large mafic igneous complexes preserved at deeper levels magmatic sulfide mineralization occurs within the opirarukaomappu gabbroic complex ogc which preserves a record of crustal contamination of mafic magmas via assimilation and magma mixing involving introduction of crust derived tonalite assimilation fractional crystallization modelling suggests that the gabbro evolved through a combination of approximately 10 wt mixing and 14 wt fractional crystallization magmatic sulfides and associated gabbros diorites and tonalites at this locality contain graphite with carbon isotope signatures consistent with derivation from the surrounding partially melted carbonaceous shales this indicates that crust derived carbon was added to the mafic magma through the magma mixing and assimilation process sulfur isotope data suggest that sulfur was also added from crustal sources during assimilation and magma mixing the relationships observed in the ogc suggest that intrusion of basalt into a segment of deep arc crust drove partial melting of carbonaceous metamorphic rocks producing graphite bearing felsic magmas with high reducing potential redox budget modelling shows that mixing of only small proportions of these magmas is sufficient to lower the oxidation state of oxidized basaltic magmas enough to induce sulfide saturation and consequent exsolution of immiscible sulfide melt magmatic sulfide deposits are likely to form by this reduction induced sulfide saturation mechanism deep within other arcs where magma mixing is thought to be common

iridium ruthenium and rhodium in komatiites evidence for iridium alloy saturation abstract a large body of new data over 400 samples on platinum group element pge concentrations in yilgarn craton komatiites is combined with all available high quality literature data to reveal trends in a spectrum of komatiite lithologies ranging from spinifex textured rocks to pure olivine and olivine chromite adcumulates the data set is restricted to carius tube isotope dilution analyses and high precision nickel sulfide fire assay icp ms analyses and we demonstrate good agreement between the two methods only s poor samples are considered and the data set is filtered to eliminate the effects of addition of cumulus chromite and addition or segregation of magmatic sulfide liquid the residual trends indicate that ir ru and rh are decoupled from one another and from pt and pd rhodium behaves more like pt and pd whereas ru is intermediate between ir and rh rhodium and ru both show indications of olivine control with partition coefficients less than unity the maximum ir whole rock content is a roughly linear positive function of mgo but the minimum is constant sub 1 ppb and independent of mgo ruthenium shows some evidence for limited control by chromite but anomalous ru enrichment is also found in some olivine cumulate samples with no evidence for accumulated chromite or sulfide neither rh nor ir shows evidence for any detectable control by chromite the distribution of ir and to a lesser degree ru and rh cannot be adequately explained by olivine control and a major influence of an ir rich phase is strongly indicated the pattern of ir variance in relation to mgo bears some important similarities to that of cr this similarity arises from the fact that both elements are controlled by a temperature dependent solubility limit the chromite saturation surface in the case of cr and saturation in ir or ir os alloy in the case of ir combining this effect with moderate compatibility in olivine allows us to successfully model the entire range of ir data the upper limit of ir concentration in olivine cumulates in an exact analogy to that for cr is interpreted as the cotectic ratio of olivine to alloy as determined by the average slope of the tangent to the alloy solubility curve sulfide undersaturated mantle melts of a wide range of compositions are likely to be ir alloy saturated experimental predictions of very low ir solubilities in magmas are borne out with the further implication that true thermodynamic sulfide silicate liquid partition coefficients at least for ir and by inference for the other pges are of the order of 107 or even higher

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

physical constraints on the migration of immiscible fluids through partially molten silicates with special reference to magmatic sulfide ores the migration of dense fe rich immiscible liquids through partially molten silicates is of critical importance to several issues including the formation of magmatic sulfide ore deposits and the formation of metallic cores in terrestrial planets the migration of immiscible dense liquids can be considered to occur in three distinct regimes dictated by the relative sizes of the dense liquid droplets and the crystals making up the silicate crystal mush or partially melted silicate rock if dense microdroplets are smaller than the diameter of the narrowest portions of pore throats between silicate crystals then downward motion is possible the maximum rate of downward settling in loosely packed crystal mushes occurs when the droplet size is approximately one tenth the crystal size as long as the silicate melt between crystals remains microdroplets are capable of migrating distances of hundreds to thousands of meters vertically through crystal mushes contained in cooling dikes with typical grain sizes stranding of larger droplets similar in size to the crystals results from capillary forces preventing droplet deformation as they attempt to pass into pore throats narrower than themselves only in very coarse grained mushes with grain sizes greater than about 2 cm can droplets the size of intergranular pores migrate downwards on the other hand coalescence of many microdroplets into pre existing stranded droplets may generate connected net textured domains of the dense liquid that are many times larger than the grain size of the mush when the vertical height of the connected domain is great enough the pressure gradient inside the dense phase exceeds the capillary force impeding downward motion through narrow pore throats and the immiscible phase is able to move down along vertically oriented networks these networks should not suffer stranding until they reach a solid layer or the base of the intrusion we suggest that in most cases sulfide droplets formed by fractional segregation in large magma bodies should come to rest at the top of the crystal pile whereas sulfides introduced to magmas by assimilation of fine grained sulfidic sediments should be capable of passing downward through crystal mushes to form massive or net textured accumulations at the bottom of the partially molten zone

the triple group and the platinova gold and palladium reefs in the skaergaard intrusion stratigraphic and petrographic relations this paper describes the setting structure and textural relations of the platinova reefs in the skaergaard intrusion the reefs comprise a strata bound occurrence of au pge estimated at 91 million tons of rock with 1 8 ppm au and similar amounts of pd the precious metals occur in two major zones a lower major pd reef which is concordant with the modal layering and followed by at least ten minor pd reefs also concordant and an au concentration which fringes the pd reefs outward and upward through the triple group units the major pd concentration and the au concentration are separated in a systematic way across the intrusion near the center of the intrusion the au concentration occurs some 60 m higher in the stratigraphy than the main pd reef but the separation decreases gradually outward being only a few meters near the margins the dominant precious metal minerals are small grains of cu fe au pd pt alloys which typically are included in interstitial sulfides bornite digenite and smaller amounts of chalcopyrite the textural relations suggest a close genetic association between the sulfides and au pge minerals an association which is confirmed by whole rock compositional data our observations demonstrate that the platinova reefs formed after significant concentration of the au pge and s in the residual magma during fractional crystallization before it became saturated with respect to a sulfide fe cu s o liquid this sulfide liquid acted as a collector of au pge and settled into the layered series cumulates we propose that the structure of the deposit evolved through fractional crystallization of the au pge bearing sulfide liquid as it was filter pressed along with the interstitial silicate melt upward into the overlying unconsolidated cumulates the fractional crystallization resulted in an evolution of the au pge bearing phases with progressive fractionation from pd rich alloys at the base of the deposit to au rich alloys at the top we argue that the sulfides evolved to their present extreme cu rich fe poor composition during oxidation desulfurization reactions in the same event which oxidized the iron titanium oxides of the intrusion this oxidation desulfurization probably had no overall effect on the distribution of au and pge

new constraints on the origin of the skaergaard intrusion cu pd au mineralization insights from high resolution x ray computed tomography abstract this contribution presents the first detailed three dimensional 3d in situ analysis of samples from the platinova reef using high resolution x ray computed tomography hrxct and 3d image processing and quantification coupled with microscopic and mineralogical investigations our hrxct analyses reveal the complex textural relationships between cu rich sulfides bulk composition close to bornite skaergaardite pdcu au rich phases silicates and fe ti oxides and provide unequivocal textural evidences not observed previously the association in 3d between cu rich sulfide globules pdcu alloy and ilmenite is inconsistent with a hydrothermal origin of the cu pd mineralization in contrast our results combined with phase diagrams strongly support a primary magmatic origin for the cu pd mineralization where cu and pd rich fe poor sulfide liquid represents a cumulus phase that forms by in situ nucleation these sulfide droplets and attached skaergaardite grains were trapped during the formation and crystallization of the fe ti oxides subsequent post cumulus processes led to the partial to total dissolution of the sulfide not entirely enclosed by the fe ti oxides i e not protected from reaction leading to the observed variability in cu and pd composition at the aggregate sulfide pdcu scale and to the occurrence of free pdcu alloys in contrast to the pdcu alloy gold bearing minerals are never observed entirely enclosed within the fe ti oxide two hypotheses can be envisaged for the formation of the gold enriched layer in the upper part of the section gold may have either precipitated from high temperature late magmatic cl rich fluids alternatively gold may have been enriched during fractional crystallization after sulfide had been suppressed from the liquidus after the pd layer crystallized and then deposited along redox barriers

lateral and vertical distribution of platinum group elements and petrogenetic controls on the sulfide mineralization in the p1 pyroxenite layer of the darwendale subchamber of the great dyke zimbabwe the great dyke of zimbabwe is a major resource of platinum group elements pge and represents the world9s second largest deposit after the bushveld complex the darwendale subchamber contains more than 75 percent of all the pge mineralization in the great dyke and is the subject of this investigation the mineralization is closely associated with sulfide bearing zones located in pyroxenites toward the top of the ultramafic sequence this environment contrasts with many other mineralized layered intrusions in that substantial plagioclase crystallization did not occur prior to the formation of the pge enriched sulfide layers several sulfide layers occur within the bronzitites of the topmost cyclic unit rather than at the base suggesting that a major mixing event of residual magma with a new influx of primitive liquid was not the primary control of the mineralization the lower sulfide zones are disseminated over 10 to 20 m and contrast with the uppermost sulfide zone s1 which is highly mineralized and generally less than 1 5 m in thickness in the s1 zone values for pt are as high as 8 ppm over a narrow interval with pt pd close to 2 the maximum enrichment of pge occurs at the first appearance of sulfide as a result of the high partitioning of these elements into sulfide liquid the order of enrichment in the sulfide is ir pd pt raquo au cu ni and as the abundance of sulfide increases this phase becomes highly depleted in these elements the enrichment pattern is consistent with fractional segregation of sulfide repetition of the mineralization results from periodic disturbance of the magma system which is related to relatively small pulses of new magma and overturns within the stratified magma column the stratified magma was sustained by the repeated influxes of new magma entering as fountains a series of peaks for pt pd and the base metals occurs in the s1 zone contrasting patterns in the vertical profile for pt and pd are attributed to the differences in the effective partition coefficients of these two elements in an environment of rapidly changing sulfide proportions marked lateral variations in the degree and style of mineralization are observed from axis to margin of the subchamber whole rock concentrations of pt are highest nearest to the margin in the very narrow and highly mineralized sulfide zone s1 but these fall to low values in the axis where the zone is more disseminated in any given vertical section the maximum concentration of pge in sulfide is similar in each of the sulfide zones the total amount of pt for the entire mineralized zone and the concentration of pt in sulfide are however significantly higher in the axial facies compared to the margin there are also major lateral variations in maximum values of cu ni and ni cu ni these lateral variations are attributed to a difference in the thermal regimes arising from the flared shape of the great dyke in cross section and its influence on the fluid dynamics of the magma chamber extensive borehole drilling has permitted detailed two dimensional contour patterns to be deduced for the distribution of pt and pd and the base metals in the s1 suboutcrop over a large area of the darwendale subchamber

noble metal enrichment processes in the merensky reef bushveld complex we have analysed sulphides silicates and chromites of the merensky introduction reef for platinum group elements pges re and au using laser the enrichment of noble metals in layered gabbroic ablation inductively coupled plasma mass spectrometry and synthetic intrusions to form stratiform merensky type ore horizons pyrrhotite standards annealed with known quantities of noble metals is an extremely efficient yet poorly understood process os ir and ru reside in solid solution in pyrrhotite and pentlandite metal enrichment must be related to the formation of rh and part of the reef s pd in pentlandite whereas pt au re magmatic layering as the ore horizons form an integral and some pd form discrete phases olivine and chromite often part of the magmatic stratigraphies of their host insuspected to carry os ir and ru are pge free all phases analysed trusions metal concentration is also related to the prescontain noble metals as discrete micro inclusions with diameters ence of magmatic sulphides because the noble metals are either dissolved in base metal sulphides or occur as typically 100 nm inclusions in sulphides commonly have the discrete noble mineral phases intergrown with sulphides element combinations os ir pt and pt pd au inclusions in vermaak hendriks 1976 ballhaus ryan 1995 olivine and chromite are dominated by pt au pd few inclusion ballhaus ulmer 1995 spectra can be related to discrete noble metal phases and few there is considerable controversy as to where the inclusions have formed by sub solidus exsolution rather some metals came from and how metal enrichment worked pge inclusions notably those in olivine and chromite are earlyfor a stratiform platinum group element pge deposit magmatic nuggets trapped when their host phases crystallized we inside the magmatic stratigraphy of a layered intrusion suggest that the silicate melt layer that preceded the merensky reef there are two possibilities either the metals were derived was pge oversaturated at early cumulus times experiments from the melt column above the ore horizon or they came combined with available sulphide silicate partition coefficients sugfrom the magma equivalent to the cumulate package gest that a silicate melt in equilibrium with a sulphide melt underlying the ore owing to the large density contrast containing the pge spectrum of the merensky ore would indeed be between silicate and sulphide melt a popular view is that oversaturated with respect to the least soluble noble metals sulphide the metals were enriched by gravitational settling of melt apparently played little role in enriching the noble metals in sulphide melt i e out of the magma column above the the merensky reef rather its role was to immobilize a pre existing ore campbell et al 1983 barnes naldrett 1985 in situ stratiform pge anomaly in the liquid stratified magma naldrett et al 1987 on the other hand it is well chamber established that gravitational crystal settling plays little role in producing magmatic layering and magmatic stratigraphies mcbirney noyes 1979 morse 1986 campbell 1987 and this cannot remain without consequence for stratiform noble metal deposits a third alternative is noble metal enrichment by late

structure and porosity of smectitic mudrocks as affected by experimental wetting drying cycles and freezing thawing cycles abstract the erosion rates in the vallcebre basin pyrenees are controlled predominantly by the physical weathering rate of bare regolith i e mudrocks to obtain information on the influence of thermic and moisture regimes on the weathering dynamics laboratory experiments were carried out to investigate how freezing thawing or wetting drying cycles under controlled conditions affect structure and porosity three different clayey mudrocks were selected to represent materials more susceptible to erosion in the studied area the three lithologies identified as ca1r ca2r carr differed mainly in mineral constituents type and quantity of the clay minerals and cation exchange capacity an automated non contact laser profile meter was used to analyse surface microtopography in order to monitor random roughness variations and to calculate bulk density porosity and pore size distribution were carried out with image analysis freezing thawing cycles were the most active in modifying soil surface and bulk structure roughness of ca1r and ca2r was more than doubled at the end of freezing thawing cycles this variation was mostly associated with the whole surface elevation related to the bulk volume increase roughness variations in carr were less pronounced and related to a modification of the microtopography micromorphological observations revealed a platy structure formation induced by repeated ice lensing also porosity was increased by freezing thawing cycles with the formation of a large number of irregular and rounded pores wetting drying cycles did not affect surface roughness and modified bulk density very little in all samples they increased porosity by the formation of large cracks and fissures overall data from wetting drying cycles showed that changes in water content alone did not produce deep structural modifications a mechanism of alteration of soil structure during freezing thawing cycles is proposed

the platinum group element and gold contents of the marginal rocks and sills of the bushveld complex previous work has defined three suites of sills and marginal rocks adjacent to and below the rustenburg layered suite of the bushveld complex namely an ultramafic mgo approximately 30 a magnesian basaltic mgo approximately 12 and a tholeiitic suite mgo approximately 7 these three suites are thought to represent magmas which have intruded and been incorporated into the rustenburg layered suite at various times during its formation the elements ir ru rh pd pt and au have been analyzed in 17 samples representative of the three suites the ultramafic sills have the highest total noble metal content 46 ppb followed by the magnesian basaltic suite 37 ppb and the tholeiitic suite 21 ppb the ultramafic sills are characterized by a relatively fiat chondrite normalized platinum group element pattern with an average pt ir ratio of 3 52 and a pronounced rh anomaly the magnesian basaltic and tholeiitic suites both have steep positive chondrite normalized patterns with average pt ir ratios of 16 14 and 40 5 respectively and no rh anomaly modeling done using incompatible trace elements and petrographic mixing suggests the ultramafic sills represent crystal mushes of cumulate olivine and chromite that were intruded into the floor during the crystallization of the lower portion of the rustenburg layered suite the enrichment of ir ru and rh in the ultramafic sills appears to be associated with the cumulate enrichment of olivine or chromite in these sills the chondrite normalized patterns found for the merensky reef and the platreef are similar to those of the magnesian basaltic magma the pattern found for the ug 2 is much flatter and in some respects very similar to that found for the ultramafic sills on a worldwide basis the platinum group element contents of the magnesian basaltic and tholeiitic magmas generally fall in the range of basalts and chill zones of other layered suites the magnesian basaltic magma does have one of the highest pt contents measured for a magma

solubility of copper in a sulfur free mafic melt the solubility of cu in s free mafic melts has been measured at a series of o2 values and temperatures of 1245 and 1300 c at constant temperature cu solubility increases from 0 04 wt at log o2 11 9 to 1 10 wt at log o2 7 4 copper solubilities were in excess of 8 wt in two runs controlled at very high o2 conditions of 10 1 4 and 10 22 partitioning of cu between metal and glass shows a strong o2 dependence with dcumetgl ranging from 90 at log o2 7 4 to 2190 at log o2 11 9 slopes of cu solubility and dcumet gl vs log o2 suggest that cu dissolves predominantly in the 1 valence state copper solubility decreases with increasing temperature at constant o2 similar to experimental results for ni co and mo dingwell et al 1994 holzheid et al 1994 the data are consistent with cu dissolution as an oxide represented by cuo0 5 and suggest that changes in o2 fe2 fe3 variations and cu1 complexation with fe3 may have large effects on the distribution of cu between silicate and sulfide magmas results also suggest that the extraction of oxide bonded cu in mafic magmas by externally derived s may be an important mechanism in the generation of cu rich sulfide ores

platinum group elements in silicate rocks of the lower critical and main zones at union section western bushveld complex concentration patterns of platinum group elements pge in the lower critical and main zones of the bushveld complex are modelled by a process of metal collection by segregating sulphide melt followed by fractional crystallization of monosulphide solid solution mss separation of os ir ru rh enriched mss cumulate ore and pt pd enriched residual sulphide melt is inferred to have occurred by upward percolation of interstitial silicate melt entraining sulphide melt whereas mss crystals are entrapped by early crystallizing chromite this process resulted in os ir ru rh enrichment of the chromitites and an upward increasing trend of pt pd os ir ru crystallization of platinum group minerals pgm from s undersaturated sulphide melt or from coalescing noble metal clusters are alternative possibilities to explain the observed pge patterns but remain difficult to model at present remobilization of pt and pd by percolating late magmatic hydrous fluids could have resulted in metal enrichment of pre existing magmatic sulphides but this model is not supported by the metal budget of the reefs and the field data there is no evidence for solid substitution of pge into oxides and silicates

the association between ni cu pge sulfide and ni co lateritic ores and volcanic facies within the komatiites of the 2 7 ga east yilgarn craton large igneous province western australia abstract a critical factor in the generation of komatiite hosted ni cu pge sulfide deposits the addition of external sulfur via assimilation of s bearing substrate beneath channelised lava flows is a function of the komatiite flow field architecture this architecture is also critical in the development of magnesium rich bedrock lithologies that are prerequisites for the formation of komatiite hosted ni co laterite deposits to better understand the controls on the spatial distribution of both these deposit types a gis referenced map of komatiite flow regimes within the komatiitic component of the c 2 7 ga east yilgarn large igneous province and from parts of adjacent older greenstone belts in the yilgarn craton has been constructed using data from the field and the literature the regimes essentially divide komatiite sequences into those composed of thin 0 5 100 m laterally restricted 50 m 3 km cooling units and those composed dominantly of thick 100 m 1 km and laterally extensive 3 100 km cooling units the regimes are subdivided into six facies and five sub facies based on both stratigraphic and lateral variations in lithologies the facies define regional scale variations reflecting markedly different spatial and temporal crystallisation conditions within komatiite flow fields there is a marked spatial association between known magmatic nickel sulfides and particular komatiite facies facies favourable for hosting magmatic sulfides are those that contain early formed very magnesian cumulate sequences requiring high effusion rates of very hot turbulently flowing lava to form and thus have the potential to be contaminated by s bearing substrate rocks sulfide mineralised komatiites make up about 9 of the area of the current outcrop of the 2705 ma komatiite lip facies that have a low potential for nickel sulfide mineralisation are sheet like bodies in which basal rocks were emplaced under relatively quiescent conditions and where hot turbulently flowing lava and crystallisation of olivine rich cumulates developed only after the build up of a pile of high porosity olivine cumulates allowing no interaction with the substrate nickel cobalt laterite deposits are associated with thick originally laterally extensive high magnesian sequences some such sequences are also favourable for magmatic sulfide mineralisation but others occur in sheet like sequences

ni cu pge deposits in finland geology and exploration potential abstract several types of nickel sulphide deposits occur in finland some of them are also important sources of cu co and pge the main deposit types are related to archaean and palaeoproterozoic mafic to ultramafic rocks palaeoproterozoic metamorphosed black shales of the talvivaara type or the ultramafic and metasomatic calc silicate rocks of the ophiolitic outokumpu association several komatiite hosted ni cu pge deposits have been discovered in the archaean and paleoproterozoic greenstone belts in northern and eastern finland but only one has been briefly mined in 1989 many 2 44 ga palaeoproterozoic mafic ultramafic layered intrusions in finland host contact type pge ni cu deposits and significant reef type pge deposits typically the ni resources are of low grade but large tonnage the mafic ultramafic magmatism at ca 2 06 ga produced significant ni cu pge resources in the central lapland greenstone belt including the kevitsa and sakatti deposits the svecofennian domain in central and southern finland contains hundreds of small ca 1 88 ga mafic ultramafic orogenic intrusions many of these host nickel mineralization nickel exploration potential was evaluated in general based on identification of critical factors within a mineral system framework and a quantitative assessment of the potential occurrence of undiscovered nickel resources the mgo content of the parental magma was estimated for 28 deposits 6 komatiite hosted occurrences and 22 svecofennian orogenic intrusions the estimated mgo content of the parental magmas for the selected deposits varies from around 7 to 15 in basaltic to komatiitic basalt systems and up to 30 in more magnesian komatiitic systems the ni cu value varies mostly between 0 7 and 12 correlating in general positively with the mgo content of the magma exceptionally high or low ni cu values in some deposits may result from for example copper loss during post magmatic processes serpentinization and or metamorphism or part of the sulphide ore zoned by the ni cu value still being unknown recent advances in understanding of komatiites in finland indicates high exploration potential for nickel within the paleoproterozoic komatiitic formations which typically are also significantly enriched in cu and pge however the quantitative assessment of undiscovered nickel resources in finland suggests that the contact type ni cu pge deposits hosted by 2 44 ga mafic ultramafic layered intrusions in northern finland have the greatest potential for hosting undiscovered resources among the assessed nickel deposit types these occur within restricted areas resulting in a high deposit density finally considerable nickel resources might exist in undiscovered talvivaara kevitsa or sakatti type deposits these deposit types should be assessed as soon as more geological information becomes available

geology mineralogy and geochemistry of magnetite associated au mineralization of the ultramafic basalt greenstone hosted crusader complex agnew gold camp eastern yilgarn craton western australia a late archean intrusion related au deposit abstract the crusader complex part of the agnew gold camp of the lawlers anticline of the yilgarn craton western australia is located close to or along the contact between the lawlers basalt and agnew ultramafics units au mineralization within the four orebodies that form the crusader complex is dominated by very pure au containing less than 1 wt ag with au variably associated with scheelite bi tellurides and minor chalcopyrite within a magnetite and titanite gangue assemblage hydrothermal alteration associated with this style of mineralization is characterized by increasing concentrations of mo be li sn and fe and depletions in na cu ba pb mn zn si and k relative to protolith concentrations these enrichments are more typical in orebodies associated with felsic intrusive related mineralizing systems rather than the more well known orogenic au deposits found elsewhere within the lawlers anticline e g at waroonga and within the greater yilgarn craton we propose that flexures of the contact between the lawlers basalt and agnew ultramafic units acted as conduits for au bearing felsic intrusive derived fluids and generated structural traps that enhanced fluid flow the mineralizing fluids that formed the crusader deposits were derived from the lawlers granitoid pluton that intruded into the study area enhanced fluid flow promoted interaction between hydrothermal fluids and the reactive mafic ultramafic rock sequence augmenting the amount of au that was precipitated during formation of the orebodies at crusader the magnetite dominated quartz and sulfide poor intrusion related mineralization at crusader contrasts sharply with other late archean intrusion related deposits of the yilgarn craton that are usually sulfide and or quartz rich this may in turn suggest that the crusader deposit represents a new class of under explored intrusion derived deposits possibly opening new mineral exploration opportunities for the agnew region and potentially the wider eastern goldfields superterrane enrichments in mo and sn and significant depletions in cu suggest that other parts of the lawlers batholith may also be prospective for base metal mineralization integration of stratigraphic interpretation with the identification of key structural fluid pathways and the presence of felsic intrusive bodies as presented in this study enables the delineation of the key elements that underlie mineralization at the crusader complex we propose that these key elements provide vital information for future gold exploration models that can be used within other archean terranes and within the eastern yilgarn craton in particular