direct evidence for an ekman balance in the california current moored acoustic doppler current profiler velocity estimates and buoy wind observations made during a period of moderate southward winds were used to test the ekman balance at a site in the california current as in prior studies the wind driven flow was separated from the total flow by subtraction of a deep reference current the wind driven flow was shown to be in an ekman balance on daily timescales over a period of several months the mean observed transport was to the right of the wind and agreed to within 3 in magnitude and 4 in phase with the predicted ekman transport although the error bar was about 20 the mean velocity profile was a smooth spiral qualitatively similar although flatter than the theoretical ekman spiral prom the observed mean momentum balance profiles of the turbulent stress and eddy viscosity were inferred eddy viscosity estimates within the wind mixed layer were o 100 cm2 s 1

changes in sulfides and platinum group minerals with the degree of alteration in the roby twilight and high grade zones of the lac des iles complex ontario canada the lac des iles complex hosts pd deposits with unusually high pd pt and pd ir ratios these high ratios have been attributed to the introduction of pd by late magmatic hydrothermal fluids the presence of hydrous silicates and low temperature sulfide mineral assemblages has been advanced as evidence for fluid overprint this idea has been investigated by documenting the change in silicate sulfide and platinum group mineralogy and texture in samples from the deposit ranging from fresh gabbronorite to extensively altered chlorite actinolite schist in addition whole rock analysis combined with laser ablation analysis of the sulfides was used to determine which phase controlled each of the pge in fresh gabbronorite the sulfide assemblage is igneous pyrrhotite pentlandite chalcopyrite and pd is present mainly in pentlandite and kotulskite pdte inclusions associated with the sulfide minerals all other pge except pt are present in solid solution in pyrrhotite and pentlandite platinum is present as sperrylite ptas2 and montcheite ptte2 inclusions associated with the sulfide minerals these observations suggest that the pge in the fresh gabbronorite were all collected by magmatic sulfide liquid in the chlorite actinolite schist the sulfide assemblage is a low temperature assemblage consisting of chalcopyrite pyrite millerite a minor amount of palladium is present in millerite but most is present as bismuth rich kotulskite and pd arsenides both of which are associated with hydrous silicate all other pge except pt are hosted by pyrite a minor amount of pt is present in pyrite but most is found as sperrylite and montcheite associated with hydrous silicate minerals the pyrite could have formed by fe loss from pyrrhotite resulting in the pyrite inheriting os ir ru and rh and fe loss from pentlandite to form millerite resulting in the millerite inheriting some pd the pge concentrations of the whole rock show there is no direct correlation between the sulfide assemblage the degree of alteration of the silicate minerals and ore grade thus although fluids have clearly altered the sulfide silicate and platinum group mineralogy and their textures it is not clear that these fluids have changed the pge content of the rocks

chalcophile and platinum group element pge concentrations in the sulfide minerals from the mccreedy east deposit sudbury canada and the origin of pge in pyrite magmatic sulfide deposits consist of pyrrhotite pentlandite chalcopyrite pyrite and platinum group minerals pgm understanding the distribution of the chalcophile and platinum group element pge concentrations among the base metal sulfide phases and pgm is important both for the petrogenetic models of the ores and for the efficient extraction of the pge typically pyrrhotite and pentlandite host much of the pge except pt which forms pt minerals chalcopyrite does not host pge and the role of pyrite has not been closely investigated the ni cu pge ores from the south range of sudbury are unusual in that sulfarsenide pgm rather than pyrrhotite and pentlandite are the main carrier of pge probably as the result of arsenic contribution to the sulfide liquid by the as bearing metasedimentary footwall rocks in comparison the north range deposits of sudbury such as the mccreedy east deposit have as poor granites in the footwall and the ores commonly contain pyrite our results show that in the pyrrhotite rich ores of the mccreedy east deposit os ir ru rh ipge and re are concentrated in pyrrhotite pentlandite and surprisingly in pyrite this indicates that sulfarsenides which are not present in the ores were not important in concentrating pge in the north range of sudbury palladium is present in pentlandite and together with pt form pgm such as ptpd tebi 2 platinum is also found in pyrite two generations of pyrite are present one pyrite is primary and locally exsolved from monosulfide solid solution mss in small amounts 2 wt together with pyrrhotite and pentlandite this pyrite is unexpectedly enriched in ipge as pt and the concentrations of these elements are oscillatory zoned the other pyrite is secondary and formed by alteration of the mss cumulates by late magmatic hydrothermal fluids this pyrite is unzoned and has inherited the low concentrations of ipge and re from the pyrrhotite and pentlandite that it has replaced

a surface velocity spiral observed with adcp and hf radar in the tsushima strait 1 the structure of a wind driven flow in the tsushima strait is investigated with moored acoustic doppler current profiler adcp and hf radar two adcps of high and low acoustic frequencies are simultaneously used to measure velocities in both the surface boundary layer and the interior with high resolutions the velocity relative to an interior flow in the surface boundary layer is estimated by subtracting the reference velocity estimated from velocities at greater depths from a velocity in the surface layer and complex principal component analysis pca of the lagged wind stress and the relative velocity is performed despite a short 2 weeks observation period of relatively calm and variable wind a clockwise velocity spiral similar to a theoretical ekman spiral is detected as the first mode of pca ekman transport estimated from the relative velocities of the first mode agrees best with ekman transport expected from wind stress of the first mode with 11 13 hours time lag for which the explained variance of the first mode is also largest this indicates that a wind driven flow is balanced with wind stress after 11 13 hours half of the inertial period at this latitude eddy viscosity is also inferred from wind stress and the relative velocities of the first mode it is found to increase from o 10 3 m 2 s 1 at greater depth to o 10 2 m 2 s 1 near the sea surface

southward recirculation of the east china sea kuroshio west of okinawa island 1 the surface current of the kuroshio recirculation region in the east china sea is investigated the surface currents in the west of okinawa island observed by hf radars and the assimilation results of the japan coastal ocean predictability experiment jcope are analyzed it appeared that currents in the easternmost edge of the kuroshio bifurcate southward and flow into the west of okinawa island from jcope data the currents are called kuroshio southward recirculation currents the currents are controlled by the bottom topography the wind stress curl in the area where the bifurcated current can be seen in jcope data is negative while the curl is positive in the eastern portion of the kuroshio the kuroshio southward recirculation currents are sometimes enhanced and their enhancement coincides with that of the positive and negative wind stress curls

anisotropic response of surface currents to the wind in a coastal region analysis of coastal surface currents measured off the coast of san diego for two years suggests an anisotropic and asymmetric response to the wind probably as a result of bottom coastline boundary effects including pressure gradients in a linear regression the statistically estimated anisotropic response explains approximately 20 more surface current variance than an isotropic wind ocean response model after steady wind forcing for three days the isotropic surface current response veers 42 86 28 to the right of the wind regardless of wind direction whereas the anisotropic analysis suggests that the upcoast onshore wind stress generates surface currents with 10 86 48 71 86 38 to the right of the wind direction the anisotropic response thus reflects the dominance of alongshore currents in this coastal region both analyses yield winddriven currents with 3 5 of the wind speed as expected in addition nonlinear isotropic and anisotropic response functions are considered and the asymmetric current responses to the wind are examined these results provide a comprehensive statistical model of the wind driven currents in the coastal region which has not been well identified in previous field studies but is qualitatively consistent with descriptions of the current response in coastal ocean models

wind driven ocean currents and ekman transport oceanographic engineering of the woods hole oceanographic institution and the massachusetts institute of technology woods hole ma 02543 oceanographers have long sought to verify the theoretical ekman transport relation which predicts that a steady wind stress acting together with the coriolis force will produce a transport of water to the right of the wind in situ measurements of wind and ocean currents provide a detailed view of this phenomenon by separating the wind driven current from the measured total current and by averaging over a long record it is found that the observed transport is consistent with theoretical ekman transport to within about 10 percent in this case the wind driven transport is strongly surface trapped with 95 percent occurring in the upper 25 meters as a result of fair summer weather

forced ocean response during the frontal air sea interaction experiment a central hypothesis of the frontal air sea interaction experiment fasinex was that the strong gradients in the upper ocean associated with ocean fronts would spatially modulate the response of the ocean to local atmospheric forcing to test this hypothesis measurements of near surface meteorology and upper ocean variability were made for 5 months from an array of moorings and for one of those 5 months from two ships a number of fronts passed through the moored array and the moored meteorological and current meter data were used to examine the response of the upper ocean to atmospheric forcing at subinertial and near inertial frequencies at low frequencies an ekmanlike frictionally driven component in the mixed layer and a more deeply penetrating component thought to be forced by ekman pumping were found strong near inertial response was found in the mixed layer the near inertial motion showed considerable spatial variability in the seasonal thermocline here it was evident that the structure of the front influenced the downward propagating near inertial internal waves data were also obtained by profiling instruments deployed along cross frontal sections these data were used to examine the spatial and temporal variability of the internal waves microstructure and dissipation and the relation of that variability to oceanic fronts and atmospheric events the spectral densities of the components of the internal waves that rotated clockwise with increasing depth were higher in regions of negative relative vorticity than those predicted by garrett and munk munk 1981 and estimates of clockwise and total shear were highest in regions of negative relative vorticity in the strong shear of the ocean front significant anisotropy of the internal wave field was observed and kinetic energy dissipation levels relative to the rate of work by the wind were higher than previously reported

a view of the 1993 1994 california current based on surface drifters floats and remotely sensed data near surface drifters were deployed in the california current system during the period 1993 1994 in order to study mean and eddy currents the deployment scheme allowed a 2 year period where data density was high enough to make meaningful estimates of eddy statistics and of seasonal mean currents and variances on a 5 grid eddy variability which tended to be isotropic was higher near the coast standard deviations around 0 2 m s 1 and decreased offshore down to 0 1 m s 1 seasonal mean surface flow west of california was southward during all seasons if a davidson current existed during 1993 1995 it was probably either short lived or only found closer to the coast than our study area i e within 100 150 km of shore in some cases drifter populations within a discrete feature were high enough to allow some detailed resolution of its behavior we note a tendency for individual eddies which can last for up to 3 5 months to drift westward at rates of o 5 km day 1 not all eddies in the region are surface intensified there is clear evidence for at least the occasional presence of a thin meandering southward jet in the region that can be 1000 km or more long this jet can be identified with that found in the coastal transition zone program in association with cool filaments the jet appears to become broader and slower south of point conception we hypothesize on the basis of others results as well as ours that the eddies that are strongest at the surface result primarily from instabilities on a southward alongshore mean current and that eddies that are maximal at depth are spawned by the northward undercurrent

diffusion of osmium in pyrrhotite and pyrite implications for closure of the re os isotopic system abstract in order to better constrain the extent to which common sulfide minerals will retain their osmium isotopic composition subsequent to crystallization we have conducted experiments to quantify the diffusion behavior of osmium in pyrite and pyrrhotite experiments consisted of either 1 isothermal soaking of diffusion couples consisting of natural pyrite or pyrrhotite crystals packed against powdered os bearing fe sulfide or 2 relaxation of initially high near surface osmium concentrations produced in the latter experiments pyrite only osmium penetration into samples was characterized by depth profiling using rutherford backscattering spectroscopy rbs pyrite or electron microprobe analyses across sectioned run products pyrrhotite results of the first type of diffusion experiment involving pyrite show only limited osmium penetration into sample surfaces with the extent of penetration uncorrelated with run duration images of pyrite samples using atomic force microscopy show roughening of initially smooth surfaces as a consequence of step formation and suggest that osmium incorporation into the near surface occurred by solute uptake during step growth and not by volume diffusion prolonged 1000 h relaxation experiments revealed no additional osmium penetration into pyrite surfaces and based on the depth resolution for rbs a maximum diffusion coefficient of 2 5 10 23 m2 s at 500 c was calculated experiments involving pyrrhotite over the temperature range of 950 1100 c showed extensive osmium uptake and osmium concentration gradients that conform with fickian diffusion behavior we found that pyrrhotite fe s could be varied by changes in the composition of the starting material and osmium source and over the range of fe s produced in experiments molar fe s 0 83 0 90 we observed no systematic variation in the osmium diffusion coefficient diffusion coefficients measured parallel to the a crystallographic axis were on average 1 4 higher than values measured parallel to c and regression of the c axis data yielded the arrhenius relation d t 1 31 0 16 10 5 m 2 s exp 211 5 14 7 kj mol rt the application of these diffusion data to simple models of diffusive exchange during static or polythermal time temperature histories is used to assess the conditions under which radiogenic osmium will be retained during isothermal annealing calculations indicate that the cores of millimeter sized spherical pyrrhotite crystals undergoing diffusive exchange with an external osmium reservoir will have their initial compositions perturbed in 0 5 ma at temperatures exceeding 400 c pyrite undergoing the same process at 500 c requires in excess of 10 ma before crystal cores are affected the relatively short core retention time scales for pyrrhotite indicates that this mineral may be prone to isotopic resetting following relatively brief crustal thermal events thus possibly accounting for the scatter that commonly occurs in re os isochrons generated from massive sulfide samples calculated closure temperatures tc for osmium exchange in pyrrhotite yielded values of 300 400 c for grain sizes ranging from 10 to 1000 m these values of tc are similar to those calculated for ar retention in biotite and considerably lower than for sr in apatite and plagioclase for example such low closure temperatures for pyrrhotite suggest this mineral will date the final stage in the cooling of a magmatic system and possibly be susceptible to open system osmium exchange in the presence of late stage hydrothermal fluids this latter result infers that caution be applied when interpreting elevated initial osmium isotopic ratios as a product of crustal assimilation at the magmatic stage

on the initiation of metamorphic sulfide anatexis mineral assemblages in common sulfide ore deposits are examined together with phase relations to 1 investigate the pressure temperature conditions required for the onset of metamorphically induced partial melting involving economic minerals and 2 place constraints on the amount of melt produced deposits that contain sulfosalt or telluride minerals may start to melt at conditions ranging from lowest greenschist facies to amphibolite facies deposits lacking sulfosalt and or telluride minerals may begin to melt once p t conditions reach the upper amphibolite facies if galena is present or well into the granulite facies if galena is absent the result is two broad melting domains a lowto medium temperature low melt volume domain involving melting of volumetrically minor sulfosalt and or telluride minerals and a high temperature potentially higher melt volume domain involving partial melting of the major sulfide minerals epithermal gold deposits which are especially rich in sulfosalt minerals are predicted to commence melting at the lowest temperatures of all sulfide deposit types massive pb zn cu deposits may start to melt in the lower to middle amphibolite facies if pyrite and arsenopyrite coexist at these conditions and in the upper amphibolite facies if they do not excepting sulfosalt bearing occurrences massive ni cu pge platinum group element deposits will show little to no melting under common crustal metamorphic conditions whereas disseminated cu deposits are typically incapable of generating melt until the granulite facies is reached when partial melting commences in bornite bearing rocks the volume of polymetallic melt that can be generated in most deposit types is therefore largely a function of the abundance of sulfosalt minerals even at granulite facies conditions this volume is usually less than 0 5 the exception is massive pb zn deposits where melt volumes significantly exceeding 0 5 vol may be segregated into sulfide magma dykes allowing mobilization over large distances

kinematics of inner shelf motions during the summer stratified season off new jersey subinertial currents on a wide 100 km shallow 20 m but nevertheless vertically stratified shelf off the atlantic seaboard of the united states are investigated at spatial scales of about 20 km in the alongshore and 10 km in the across shore direction during the summer of 1996 the inner shelf off new jersey was stratified due to both temperature and salinity that varied vertically by more than 128c and 4 psu respectively upwelling favorable winds and an intermittent buoyancy driven hudson coastal current impact this stratification inshore of the 15 m isobath waters offshore were always stratified except during the passage of tropical storm bertha mean currents are weak because wind forced upwelling and buoyancy forced downwelling events occurred about evenly during the observational study period at monthly to daily timescales currents always veered counterclockwise with depth in a bottom ekman layer sense by more than 308 inshore and 508 offshore complex empirical orthogonal function ceof analyses revealed that these veering angles are contained in the first mode that explains 80 85 of the total variance at individual locations it also explains 72 of the variance of 44 current time series of an across shore section the veering constitutes a robust feature that cannot be rationalized by ekman dynamics in shallow water alone the authors hypothesize that the veering represents a frictional response common to both upwelling and downwelling events the ceof analysis does not separate wind from buoyancy forcing the two forcing mechanisms thus appear to be dynamically coupled nevertheless the first two ceofs suggest distinctly different circulation regimes for positive and negative temporal amplitudes mode 1 represents a wind forced upwelling and a buoyancy forced downwelling circulation while mode 2 represents the lateral shear of the flow field synoptic maps of surface currents from ocean surface current radar reveal realizations of these event types

platinum group element gold silver and base metal distribution in compositionally zoned sulfide droplets from the medvezky creek mine noril sk russia concentrations of ag au cd co re zn and platinum group elements pge have been determined in sulfide minerals from zoned sulfide droplets of the noril sk 1 medvezky creek mine the aims of the study were to establish whether these elements are located in the major sulfide minerals pentlandite pyrrhotite chalcopyrite and cubanite to establish whether the elements show a preference for a particular sulfide mineral and to investigate the model which suggests that the zonation in the droplets is caused by the crystal fractionation of monosulfide solid solution mss nickel cu ag re os ir ru rh and pd were found to be largely located in the major sulfide minerals in contrast less than 25 of the au cd pt and zn in the rock was found to be present in these sulfides osmium ir ru rh and re were found to be concentrated in pyrrhotite and pentlandite palladium and co was found to be concentrated in pentlandite silver cd and zn concentrations are highest in chalcopyrite and cubanite gold and platinum showed no preference for any of the major sulfide minerals the enrichment of os ir ru rh and re in pyrrhotite and pentlandite exsolution products of mss and the low levels of these elements in the cubanite and chalcopyrite exsolution products of intermediate solid solution iss support the mss crystal fractionation model because os ir ru rh and re are compatible with mss the enrichment of ag cd and zn in chalcopyrite and cubanite also supports the mss fractionation model these minerals are derived from the fractionated liquid and these elements are incompatible with mss and thus should be enriched in the fractionated liquid gold and pt do not partition into either iss or mss and become sufficiently enriched in the final fractionated liquid to crystallize among the iss and mss grains as tellurides bismithides and alloys during pentlandite exsolution pd appears to have diffused from the cu rich portion of the droplet into pentlandite

methodology for a regional tidal model evaluation with application to central california abstract observations from disparate observational assets including tide gauges moorings and high frequency hf radars were used to depict the tidal variability and to evaluate model tidal simulations for a region off central california including the monterey bay for this study the hydrodynamic model was forced only with tides derived from a large scale model for the northeast pacific ocean homogeneous density and initially horizontally uniform density stratification cases were considered the model successfully reproduced tidal sea surface height variations within the model domain as determined by comparisons with sea level or bottom pressure measured at six locations to achieve tidal currents with realistic amplitudes as determined from hf radar and moored measurements it was found that barotropic velocity as well as sea level from the large scale regional tidal model must be included in specifying the open boundary condition however even with such forcing the model with homogeneous density field under predicted the semidiurnal and diurnal barotropic currents as estimated from depth averaged currents measured at 11 locations in the diurnal frequency band the observed surface and nearshore depth averaged currents are likely influenced by meteorological forcing which was not included in the model the hf radar measured surface tidal currents both semidiurnal and diurnal are consistent from year to year and between the winter season and the entire year semidiurnal surface tidal currents derived from year long hf radar measurements do not resemble either the modeled or measured barotropic current fields rather they exhibit amplitudes and small scale spatial variability indicative of the presence of internal tides thus indicating that model derived barotropic tidal currents cannot be validated over large spatial extents using long time series of hf radar derived surface currents with initially horizontally uniform vertical density stratification the model produced surface currents with spatial variability and amplitude range comparable to what was derived from hf radar surface current measurements but the point by point comparisons are not impressive for this region of complex topography likewise the subsurface current comparisons performed at four deepwater locations show considerable model data differences possible reasons for these disparities include the effects of atmospheric forcing spatially and temporally varying stratification remotely generated coastally trapped waves and remotely generated internal tides

the subpolar front of the japan east sea part iii competing roles of frontal dynamics and atmospheric forcing in driving ageostrophic vertical circulation and subduction abstractthe effects of wind stress and surface cooling on ageostrophic vertical circulation and subduction at the subpolar front of the japan east sea are investigated using a nonhydrostatic numerical model in experiments forced by wind and or cooling ageostrophic vertical circulation is enhanced relative to the unforced case both surface cooling and wind stress intensify the circulation by enhancing frontogenesis associated with frontal meandering winds further strengthen vertical motions by generating internal gravity waves downfront winds i e oriented along the frontal jet transport surface water from the denser to lighter side of the front causing it to migrate toward the region of higher stratification and enhancing the vertical mixing at the front this induces outcropping of isopycnals from the middle of the pycnocline along which surface water is subducted hence downfront winds enhance subduction down to the middle of the pycnocline but not beneath on the other hand cooling uplifts i

hf radar data assimilation in the monterey bay area 1 the utility of high frequency hf radar data for improving numerical circulation model predictions is evaluated comparisons of the statistical properties of the codar type hf radar data and the observed wind indicate a strong correlation between the dominant alongshore upwelling favoring wind forcing and hf radar derived surface currents along the central california coastline because inadequate knowledge of the wind stress is probably a significant source of error in the model solutions the idea of using hf radar data to provide corrections to the model wind forcing is promising different hf radar data assimilation schemes are compared and judged based on the correlations observed between model currents and independent observations from two mooring sites analysis of correlation maps between model predicted and observed currents indicates a spatial and temporal shift between modeled and observed features however the impact of hf radar data assimilation reduces these spatial and temporal shifts a significant improvement in the correlation between the model and observed subsurface currents is achieved when an ekman layer projection of the corrections is included in this approach assimilation of hf radar data produces additional ekman pumping vertical velocity based on the horizontal pattern of model observed velocity mismatch at the surface

zonal momentum balance at the equator abstract the conventional view of equatorial dynamics requires that the zonal equatorial wind stress be balanced in the mean by the vertical integral of large scale terms such as the zonal pressure gradient mesoscale eddy flux and mean advection over the upper few hundred meters it is usually presumed that the surface wind stress is communicated to the interior by turbulent processes turbulent kinetic energy dissipation rates measured at 140 w during the tropic heat i experiment and a production rate dissipation rate balance argument have been used to calculate the zonal turbulent stress at 30 to 90 m depth the calculated turbulent stress at 30 m depth amounts to only 20 of the wind stress and decreases exponentially with depth below 30 m typical large scale estimates of the zonal pressure gradient mesoscale eddy flux and advection have a depth scale larger than the turbulent stress and are inconsistent with the vertical divergence of the stress as estimated from the dissipation rate measu

magmatic sulfides and au cu ratios in porphyry deposits an experimental study of copper and gold partitioning at 850 c 100 mpa in a haplogranitic melt pyrrhotite intermediate solid solution gold metal assemblage at gas saturation abstract the behavior of copper and gold in the phase assemblage pyrrhotite po intermediate solid solution iss haplogranitic melt gold metal capsule at 850 c 100 mpa and gas saturation ah2o 0 9 has been investigated the results are presented as nernst partition coefficients the partition coefficient dcupo melt 2 6 0 3 103 1 was determined for po and melt in equilibrium with an iss of composition cu 19 1 fe 30 1 s 51 1 2 for gold the partition coefficients are dauiss melt 5 7 2 2 103 1 between iss and melt and daupo melt 140 40 1 between po and melt these imply dauiss po 42 9 1 between iss and po the oxygen fugacity for the experiments log f o 2 13 2 0 3 1 was determined by using the hydrogen sensor technique the sulfur fugacity log f s 2 1 0 0 7 1 was calculated from the composition of po in our experiments melts at iss saturation have cu fe by weight of ca 1 100 the results indicate that crystallization of iss may deplete a melt in gold and crystallization of po may deplete a melt in copper however a melt saturated with iss at a given bulk composition temperature pressure oxygen and sulfur fugacity and feo concentration will have a fixed concentration of cu preventing strong depletion of the melt in cu until iss is fractionated from the melt or changes in environmental conditions destabilize iss a thermodynamic model for the partitioning of cu and au between po and melt in terms of oxygen and sulfur fugacity indicates that dcupo melt and daupo melt may increase greatly with increasing sulfur fugacity and decreasing oxygen fugacity within the po stability field the model also suggests that destabilization of both iss and po relative to magnetite due to changes in oxygen and sulfur fugacities can result in the release of cu and au from the sulfides to the melt

an experimental study on the geochemical behavior of highly siderophile elements hse and metalloids as se sb te bi in a mss iss pyrite system at 650 c a possible magmatic origin for co hse bearing pyrite and the role of metalloid rich phases in the fractionation of hse abstract pyrite the most abundant sulfide in the earth s crust is an accessory mineral in several magmatic sulfide deposits although most pyrite is hydrothermal previous experimental studies have shown that pyrite can also have a primary magmatic origin by exsolving from monosulfide solid solution mss during cooling of a sulfide melt if sulfur fugacity is sufficiently high pyrite from some localities has significant amounts of co and complex zonation in some low melting point chalcophile elements lmce such as as se sb te bi henceforth referred to as metalloids and some platinum group elements pge ru rh pd os ir pt however the origin of such pyrite and the causes of zonation are not clear because the distribution of some of these elements is heterogeneous and seems to be developed in concentric zones the zonation has been interpreted to represent growth stages some of them secondary and caused partly by hydrothermal fluids better constraints on the origin of co pge bearing pyrite could help unravel the geochemical processes affecting the sulfide assemblages in which it is found thus an experimental study was undertaken to characterize pyrite formation in magmatic sulfide environments and its relationship with metalloids and highly siderophile elements hse pge re au natural pyrrhotite chalcopyrite pentlandite and elemental s were mixed and doped with approximately 50 ppm of each hse a mixture of metalloids was added at 0 2 wt or 3 wt to aliquots of sulfide mixtures starting materials were sealed in evacuated silica tubes and fused at 1200 c the temperature was subsequently reduced to 750 c at 60 c h then to 650 c at 0 5 c h to produce relatively large euhedral pyrite crystals then quenched the experiments were analyzed using reflected light sem epma and la icp ms experimental products contained euhedral pyrite mss intermediate solid solution iss and metalloid rich phases interpreted as quench product of an immiscible metalloid rich liquid the results show that co ni hse bearing pyrite with complex zonation in ru rh os ir and pt can form by a subsolidus reaction involving both mss and iss and does not require secondary e g hydrothermal processes because such pyrite results from the cooling of a sulfide melt after mss and iss it can be described as magmatic among the hse ru rh os re and ir have identical zonation patterns in pyrite pt is also zoned but differently and au and pd are essentially excluded previously documented natural hse bearing pyrite also display identical zonation patterns in ru rh os and ir the complex zoning is likely preserved due to the extremely slow diffusion rates for those elements in pyrite thus the presence of pyrite with similar characteristic in natural sulfide assemblages is consistent with a magmatic origin and does not require hydrothermal processes the results also show that if a metalloid rich liquid is present it will significantly sequester au pd and pt but will not affect ru rh os re and ir in the absence of metalloid rich phases au partitions strongly into iss and pd partitions preferentially into mss

detecting and characterizing ekman currents in the southern ocean abstractthis study presents a unique array of velocity profiles from electromagnetic autonomous profiling explorer em apex profiling floats in the antarctic circumpolar current acc north of kerguelen the authors use these profiles to examine the nature of ekman spirals formed by the action of the wind on the ocean s surface in light of ekman s classical linear theory and more recent enhancements vertical decay scales of the ekman spirals were estimated independently from current amplitude and rotation assuming a vertically uniform geostrophic current decay scales from the ekman current heading were twice as large as those from the current speed decay indicating a compressed spiral consistent with prior observations and violating the classical theory however if geostrophic shear is accurately removed the observed ekman spiral is as predicted by classical theory and decay scales estimated from amplitude decay and rotation converge toward a common value no statistically robust relationship is

textural and compositional evidence for the formation of pentlandite via peritectic reaction implications for the distribution of highly siderophile elements the distribution of highly siderophile elements is used in the study of a wide variety of geological topics from planet formation and evolution to the formation of ore deposits under mantle and crustal conditions these elements behave as highly chalcophile elements and pentlandite pn is an important host for most of these elements therefore understanding how pn forms is important to understanding the processes that control these elements the classic model for the formation of pn is that below 650 c the high temperature sulfides monosulfide solid solution mss and intermediate solid solution iss are no longer stable and exsolve into pyrrhotite po pn and chalcopyrite ccp however pn has been shown to be the main host of pd in many ore deposits and given that pd is incompatible with both mss and iss this observation is inconsistent with the exsolution model furthermore experimental work has shown that pn can form by peritectic reaction between mss and fractionated sulfide liquid to date this type of pn has not been reported in natural samples in our study of chalcophile element concentrations in pn from iconic magmatic ni cu platinum group element deposits we observed three textures of pn contact pn in between po and ccp granular pn included within ccp or po and flame pn included within po the contact pn shows zonation in mo rh ru re os and ir with these elements being enriched toward the po contact and depleted toward the ccp contact in some cases pd displays a zonation antithetical to that of these elements in this contribution we propose that the contact pn formed via the peritectic reaction described above and inherited mo ru rh re os and ir from the mss whereas pd was contributed from the fractionated sulfide liquid we expect that this type of pn should be present wherever mss and fractionated sulfide liquid remained in contact

evidence for as contamination and the partitioning of pd into pentlandite and co platinum group elements into pyrite in the fazenda mirabela intrusion brazil the fazenda mirabela intrusion in brazil hosts two zones of mineralization the santa rita ni cu sulfide ore zone occurring predominantly in an orthopyroxenite layer and an underlying basal platinum group element pge anomaly hosted in s poor dunite we show that in the northern and southern marginal zones of the intrusion pt pd ni cu fe bi te 2 minerals are accompanied by as bearing platinum group minerals pgm sperrylite ptas2 and irarsite rhirpt ass these as bearing pgm are extremely rare in the central zone of the intrusion suggesting that as has been introduced into the margins of the intrusion from the country rocks via crustal assimilation or synmagmatic hydrothermal processes other pgm and precious metal minerals pmm including hessite ag2te pd ag tellurides electrum and native au are observed in the santa rita ore zone and do not show any lateral variation in the semimetal and s poor dunite hosting the basal pge anomaly pge are predominantly retained in the base metal sulfides and only minor pge alloys are present in this s poor dunite pt au and semimetals partitioned into a fractionated cu rich liquid which formed during the crystallization of monosulfide solid solution mss and was largely removed by high temperature magmatic fluids palladium was not affected by this process and significant concentrations of pd are identified in pentlandite suggesting that pd preferentially partitioned into mss as it crystallized and subsequently pentlandite as it exsolved pyrite in the santa rita ore zone is co rich and contains higher concentrations of ipge os ir ru and rh than pyrrhotite and pentlandite suggesting that pyrite has not replaced and inherited the pge concentrations of these sulfides the pd poor nature of pyrite also indicates that it has not replaced pd rich pentlandite it is proposed that the ipge and co preferentially partitioned into pyrite as it exsolved from mss

spatial and temporal characteristics of the mesoscale circulation of the california current from eddy resolving moored and shipboard measurements moored observations of currents and temperatures made in the upper 600 rn on eddy resolving scales over a 2 year period are used to examine the spatial and temporal characteristics of the california current mesoscale circulation the observations were made at three principal longitudes 124ow 126ow and 128ow in the vicinity of point arena they bracket the 600 km wide band of high mesoscale variability found along the eastern boundary of the north pacific at all locations the mesoscale variability was larger than the mean flow and the spatial modes of variability as determined from empirical orthogonal function analysis consisted of an alongshore mode a cross shore mode and a rotational mode observations made near the continental slope 124ow were dominated by the poleward flowing california undercurrent with mesoscale eddies and meanders superposed the nearshore eddy kinetic energy peaked in a band centered around 60 days observations made at 128ow near the offshore boundary between the energetic mesoscale band and the eddy desert of the northeast pacific were characterized by small means fewer eddy events and a peak in eddy kinetic energy at 120 180 days the good horizontal resolution of the current meter arrays allowed us to estimate the relative vorticity horizontal divergence and rossby number and therefore to evaluate the relative strength and occurrence of anticyclones and cyclones we found the mesoscale eddy field to be strongly nonlinear with rossby numbers ranging from 0 1 to 0 5 all of the eddies observed at the offshore site were nonlinear deep warm anticyclones shipboard hydrography revealed the origin of one of these anticyclones to be the california undercurrent and this eddy retained its strong anomalies after several months and several hundred kilometers of propagation despite the lower incidence of eddies as one moves west from the coast the eddies that we observed offshore provide evidence for propagation and transport of properties from the coast to the central north pacific across the california current system

nonlinear equilibration of thermohaline intrusions abstract the nonlinear behavior of thermohaline intrusions on a wide front is investigated using a one dimensional numerical model the model is used to follow the evolution of a field of intrusions from infinitesimal amplitude to a large amplitude state characterized by inversions in temperature and salinity it is thus possible to extend the analytical studies of toole and georgi and others to large amplitude allowing for the effects of amplitude dependent diffusivities and for the appearance of stably stratified diffusively stratified and statically unstable regions in the water column as the intrusions grow the model runs are initialized with infinitesimal disturbances that grow exponentially in time until inversions in temperature and salinity occur after inversions appear the intrusions evolve toward an equilibrium state in which friction balances buoyancy forces for both finger and diffusive sense basic state stratifications these equilibrium states are characterized by statically unstabl

observations of seasonal variation in the ekman layer abstract the seasonal variation in the ekman layer is examined using observations from the long term upper ocean study lotus including surface meteorology current and temperature the near surface current is found to be coherent with the wind at low frequencies periods greater than one day using a wind relative averaging method the authors find the observed near surface volume transport to be consistent with ekman transport the mean current profile has a spiral shape that is flat compared to the classic ekman spiral in that it rotates less with depth than does the ekman spiral the mean current e folds over 12 m in the summer and 25 m in the winter with a decay in amplitude that implies eddy viscosities of 60 10 4 and 250 10 4 m2 s 1 respectively diurnal cycling is the dominant mode of variability in the summer and it determines the vertical structure of the spiral in the winter diurnal cycling is almost nonexistent due to greatly reduced solar insolation and stronger winds a persisten

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

distribution of chalcophile and platinum group elements among pyrrhotite pentlandite chalcopyrite and cubanite from the noril sk talnakh ores implications for the formation of platinum group minerals in most magmatic sulfide deposits platinum group elements pge are found both within the structure of the base metal sulfides bms pyrrhotite po pentlandite pn chalcopyrite ccp and cubanite cbn and as platinum group minerals pgm tellurium as bi sb and sn tabs are essential elements in many of these pgm the potential role of tabs in collecting pge and thus forming a pge deposit has not been closely investigated we have determined the concentrations of a full suite of chalcophile elements in po pn ccp and cbn using laser ablation inductively coupled plasma mass spectrometry on samples from the noril sk talnakh ni deposits in these deposits the po rich ore is thought to represent monosulfide solid solution mss cumulate of the initial sulfide liquid and the ccp rich ore a mixture of the fractionated sulfide liquid and intermediate solid solution iss the bms from the po rich ore contain lower concentrations of tabs pd pt and au and higher concentrations of mo ru rh re os and ir than bms from the ccp rich ores this observation is consistent with experimental results which show that tabs pd pt and au are incompatible with mss whereas the other elements are compatible in mss counter intuitively in the po rich ore the bulk of the pd and tabs is hosted by bms this is because during crystallization although only a small amount of the incompatible elements partitioned into the bms the fractionated liquid has migrated away thus the po rich ores represent mss adcumulates therefore as the po rich ores contain very little trapped liquid fraction the bms host the bulk of pd and tabs in contrast in the ccp rich ore the bulk of au pd pt and tabs is present as pgm or electrum grains this is because more trapped liquid is present and as tabs au pd and pt are not compatible with iss they concentrated into the very last sulfide liquid and crystallized as intergrowths of pd pt tabs pgm the tabs then do not appear to collect pd pt and au but rather all elements are concentrated in the most fractionated sulfide liquid by crystal fractionation

wetting facilitates late stage segregation of precious metal enriched sulfosalt melt in magmatic sulfide systems the wetting behavior of as rich sulfosalt melts against monosulfide solid solution mss is investigated using experiments to elucidate late stage fractionation processes in magmatic sulfide systems which may control the distribution of platinum group elements a range of as rich melt compositions is found to wet mss including those that contain significant proportions 1 45 of precious metals pt pd and au however extremely au rich or pt rich sulfosalt melts 40 au 50 pt 5 au do not wet mss these results imply that if magma contamination and or fractionation processes were able to produce a late stage as rich melt sulfosalt melts crystallize cooler than mss that exceeds 0 2 of the rock volume then an interconnected melt drainage network would be able to form along mss crystal triple junctions the dense sulfosalt melt could thereby drain downward progressively sequestering incompatible bi sb te pt pd and au to form sulfosalt melt accumulations that continue to fractionate to form the platinum group minerals this late stage fractionation model is consistent with the observed mineral distribution in numerous magmatic sulfide deposits

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

pyrite and pyrrhotite textures and composition in sediments laminated quartz veins and reefs at bendigo gold mine australia insights for ore genesis the various types textures and compositional zoning of pyrite in the gold bearing saddle reefs quartz veins and surrounding sedimentary rocks provide new information on the potential source and timing of gold and arsenic and related fluid processes responsible for mineralization at bendigo nodular diagenetic pyrite in the black shale tops to sandstone turbidites is enriched in invisible gold and arsenic with mean values of 0 61 ppm au 1 300 ppm as and au ag 1 based on la icpms analyses other elements enriched in the diagenetic pyrite within the organic rich shales are mn zn mo cu v ba ag cd tl co ni bi pb and te in contrast euhedral and growth zoned hydrothermal pyrite in the turbidites and bedding parallel laminated quartz veins contains lower contents of most trace elements but has higher contents of invisible au and as especially on the outermost rim of the pyrite the gold rich pyrite rims generally become thicker a few to hundreds of microns in proximity to the gold bearing saddle reefs pyrite in the reef commonly has the highest levels of invisible au and as and the lowest levels of other trace elements it is characterized by au ag 1 and au pb 0 01 in the deepest stratigraphic levels below known productive gold reefs diagenetic pyrite in the most carbonaceous shales has been replaced by pyrrhotite during metamorphism la icpms analyses reveal that the disseminated pyrrhotite contains similar levels of ni and co to the diagenetic pyrite but is strongly depleted in as and au the spatial relationships between organic rich shales folded bedding parallel laminated quartz veins and gold arsenic bearing saddle reefs combined with the consistent trends in the trace element composition of pyrite hosted by these three geological elements is interpreted to indicate that the black shales were an initial source of au and as and the laminated quartz veins acted as the initial pathways for hydrothermal fluid flow carrying au and as from the source shales to the saddle reefs maximum gold and arsenic input into the reefs principally as free gold plus arsenopyrite occurred late during deformation toward the end of the hydrothermal cycle and is expressed by the au as rich rims to hydrothermal pyrite in the sedimentary host rocks laminated quartz veins and reefs this corresponds with final fold lockup and the development of through going fault arrays linking adjacent anticlines the source of au and as for this final and most economically important fluid flow event is considered to be from carbonaceous shales deeper in the basin where original gold bearing diagenetic arsenian pyrite reacts with organic matter and is converted to pyrrhotite with release of au as and s to the metamorphic fluid

rare earth element partitioning between titanite and silicate melts henry s law revisited we present detailed experimental results on the partitioning of rare earth elements ree between titanite and a range of different silicate melts our results show that henry s law of trace element partitioning depends on bulk composition the available partners for heterovalent substitution crystal composition and melt composition we illustrate that the partition coefficients for sm depend very strongly on the bulk concentration of sm in the system the substitution mechanism by which rare earth elements are incorporated into the crystal structure plays an important role for trace element partitioning and also for the onset of henry s law our data show that there are clear differences between substitution mechanisms of major elements compared to elements which are present only as traces our experiments also clearly show that the onset of henry s law depends on the concentrations of the sum of all trace elements which are incorporated into the crystal by the same substitution mechanism for geochemical modelling of magmatic processes involving titanite and indeed other accessory phases it is of crucial importance to first evaluate whether the ree and other trace elements are present as traces or as major elements only then appropriate d values may be chosen

wind waves and fronts frictional effects in a generalized ekman model abstractocean currents in the surface boundary layer are sensitive to a variety of parameters not included in classic ekman theory including the vertical structure of eddy viscosity finite boundary layer depth baroclinic pressure gradients and surface waves these parameters can modify the horizontal and vertical flow in the near surface ocean making them of first order significance to a wide range of phenomena of broad practical and scientific import in this work an approximate green s function solution is found for a model of the frictional ocean surface boundary layer termed the generalized ekman or turbulent thermal wind balance the solution admits consideration of general more physically realistic forms of parameters than previously possible offering improved physical insight into the underlying dynamics closed form solutions are given for the wind driven flow in the presence of coriolis stokes shear a result of the surface wave field and thermal wind shear arising from a baroclinic

pyrite physical and chemical textures pyrite may crystallize initially in forms as diverse as framboids or cubes depending upon the temperatures and pressures fluid rich diagenesis or low grade metamorphism clearly results in thorough recrystallization and the common formation of cubes once these have formed the pyrite becomes much more refractory and retains many characteristics even in deposits which have undergone penetrative deformation this is in strong contrast to the behavior of most of the accompanying sulfides which often undergo ductile deformation solid state or chemical remobilization and annealing pyrite deforms sparingly until there is brittle failure however there may be significant pyrite corrosion and regrowth during metamorphism as the result of sulfur exchange with other minerals especially pyrrhotite pyrite fabrics may also be significantly modified by pressure solution or coble creep optical microscopic examination and electron microprobe chemical mapping of pyrites from a variety of mineral deposits including several high grade metamorphic ones reveals that the pyrites frequently contain both physical and chemical textures that may be interpreted in terms of the depositional and the post depositional history of the deposits inclusions of sulfides or other minerals reveal information on the timing of the crystallization or recrystallization of the pyrite chemical mapping of elements such as ni co and as reveals information on the relative time of transport of these elements in the ore fluids

the wave driven ocean circulation oceanic surface gravity waves have a mean lagrangian motion the stokes drift the dynamics of winddriven basin scale oceanic currents in the presence of stokes drift are modified by the addition of so called vortex forces and wave induced material advection as well by wave averaged effects in the surface boundary conditions for the dynamic pressure sea level and vertical velocity some theoretical analyses previously have been made for the gravity wave influences on boundary layer motions including the ekman currents the present paper extends this theory to the basin scale depth integrated circulation in a bounded domain it is shown that the sverdrup circulation relation with the meridional transport proportional to the curl of the surface wind stress applies to lagrangian transport while the associated eulerian transport is shown to have a component opposite to the stokes drift transport a wave induced correction to the relation between sea level and surface dynamic pressure is also derived preliminary assessments are made of the relative importance of these influences using a global wind climatology and an empirical relationship between the wind and wave fields recommendations are made for further development and testing of this theory and for its inclusion in general circulation models

altimeter derived variability of surface velocities in the california current system 1 evaluation of topex altimeter velocity resolution in this paper we evaluate the temporal and horizontal resolution of geostrophic surface velocities calculated from topex satellite altimeter heights moored velocities from vector averaging current meters and an acoustic doppler current profiler at depths below the ekman layer are used to estimate the temporal evolution and accuracy of altimeter geostrophic surface velocities at a point surface temperature gradients from satellite fields are used to determine the altimeter s horizontal resolution of features in the velocity field the results indicate that the altimeter resolves horizontal scales of 50 80 km in the along track direction the rms differences between the altimeter and current meters are 7 8 cm s 1 much of which comes from small scale variability in the oceanic currents we estimate the error in the altimeter velocities to have an rms magnitude of 3 5 cm s 1 or less uncertainties in the eddy momentum fluxes at crossovers are more difficult to evaluate and may be affected by aliasing of fluctuations with frequencies higher than the altimeter s nyquist frequency of 0 05 cycles d 1 as indicated by spectra from subsampled current meter data the eddy statistics that are in best agreement are the velocity variances eddy kinetic energy and the major axis of the variance ellipses spatial averaging of the current meter velocities produces greater agreement with all altimeter statistics and increases our confidence that the altimeter s momentum fluxes and the orientation of its variance ellipses the statistics differing the most with single moorings represent well the statistics of spatially averaged currents scales of 50 100 km in the ocean besides evaluating altimeter performance the study reveals several properties of the circulation in the california current system 1 velocity components are not isotropic but are polarized strongly so at some locations 2 there are instances of strong and persistent small scale variability in the velocity and 3 the energetic region of the california current is isolated and surrounded by a region of lower energy starting 500 700 km offshore this suggests that the source of the high eddy energy within 500 km of the coast is the seasonal jet that develops each spring and moves offshore to the central region of the california current rather than a deep ocean eddy field approaching the coast from farther offshore

variability of the near surface eddy kinetic energy in the california current based on altimetric drifter and moored current data low pass filtered velocities obtained from world ocean circulation experiment woce surface drifters deployed in the california current off northern california during 1993 1995 have been compared with surface geostrophic velocity estimates made along subtracks of the topex poseidon altimeter and with moored acoustic doppler current profiler adcp data to obtain absolute geostrophic velocities a mean sea surface height ssh field was estimated using the mean drifter velocities and historical hydrographic data and was added to the altimetric ssh anomalies the correlation between collocated drifter and altimetric velocities is 0 73 significant at the 95 level the component of the drifter velocity which was uncorrelated with the altimetric velocity was correlated with the wind in the ekman transport sense monthly averages of eddy kinetic energy eke estimated using all drifter and altimeter data within the domain 124 132 w 33 40 5 n show energy levels for the drifters that are about 13 greater than those for the altimeter drifter altimeter and adcp measurements all exhibit similar seasonal cycles in eke with the altimeter data reaching maximum values of about 0 03 m 2 s 2 in late summer fall wavenumber spectra of the altimeter velocity indicate that the velocity fluctuations were dominated by features with wavelengths of 240 370 km while the adcp data suggest that the temporal scales of these fluctuations are at least several months between 36 and 40 5 n the region of monthly maximum eke migrates westward to about 128 w on a seasonal timescale this region of maximum eke coincides with the maximum zonal ssh gradient with increased eke associated with increased southward flow a simple model shows that much of the seasonal cycle of the ssh anomalies can be produced by linear processes forced by the curl of the wind stress although the model cannot explain the offshore movement of the front

an overview of chalcophile element contents of pyrrhotite pentlandite chalcopyrite and pyrite from magmatic ni cu pge sulfide deposits we have compiled the trace element concentrations in pyrrhotite pentlandite chalcopyrite and pyrite from magmatic ni cu pge ore deposits with the aim of understanding their petrogenesis and whether these minerals can be used as indicator minerals among the samples there are some of the most studied world class ni cu aguablanca duluth jinchuan noril sk talnakh kharaelakh sudbury voisey s bay and others and pge dominated bushveld lac des iles stillwater great dyke and penikat deposits crustal assimilation may be constrained using as se and sb se ratios in pentlandite the degree of interaction between the silicate and sulfide liquids r factor can be estimated by the content of highly chalcophile elements dsulf liq sil liq above 1000 in sulfide minerals the fractional crystallization of the sulfide liquid can be traced using se te ratios of pentlandite pyrite formed by exsolution from mss has higher rh ru ir and os than co existing pyrrhotite whereas pyrite formed by hydrothermal alteration of pyrrhotite inherits the rh ru ir and os contents of the pyrrhotite it replaced sulfide minerals are preserved in transported glacial cover and their trace element chemistry can be used to discriminate their source pentlandite from ni cu deposits has much lower rh and pd concentrations than those from pge dominated deposits pyrite from magmatic deposits has higher co sb and se as ratios relative to pyrite from hydrothermal deposits and chalcopyrite from magmatic deposits has much higher ni and lower cd concentrations than those from hydrothermal deposits