interaction of magmatic fluids and silicate melt residues with saline groundwater in the footwall of the sudbury igneous complex ontario canada new evidence from bulk rock geochemistry fluid inclusions and stable isotopes abstract along the northern margin of the 1 85 ga sudbury igneous complex sic canada a volumetrically minor rock type known as the footwall granophyre fwgp preserves evidence of the interaction of magmatic fluid and groundwater the fwgp comprises veins dikes and irregular bodies of a quartz alkali feldspar plagioclase intergrowth that are most abundant near footwall style cu ni platinum group element mineralization textures and cross cutting relations show that the emplacement of the fwgp created favourable sites for the later deposition of sulfides geochemical and physical evidence show that the fwgp did not form by in situ partial melting of the archean country rocks in the footwall beneath the sic it represents a mobilized injected silicate residue from either the contact between partially melted country rocks and the sic or from the crystallizing sic itself its bulk composition can be modeled as the product of fractional crystallization of a liquid with an initial composition equivalent to granophyric matrix trapped liquid in the lowermost units of the sic norite and sublayer primary fluid saline h 2 o poor and melt silicate h 2 o rich inclusions hosted in quartz from the fwgp have bulk and trace element compositions consistent with those hosted in quartz from the granophyric matrix of the lower units of the sic norite sublayer fluid inclusions contain mixtures of a high salinity 44 70 wt nacl equivalent n 39 na fe rich aqueous magmatic fluid and a lower salinity ca and sr rich groundwater the magmatic end member is thought to be an sic derived volatile phase estimates of the mixing proportions show that primary and secondary inclusions in the fwgp contain 60 100 and 30 80 of the magmatic end member by mass respectively fluids responsible for the remobilization of ore metals represent mixtures containing a much higher proportion of the groundwater end member not less than 70 by mass compared to the fluids trapped in the fwgp at considerable distance 400 m from the sic the chlorine isotope composition of biotite in the fwgp is enriched in 37 cl 37 cl 0 98 to 1 61 scapolite from the high temperature veins and the interstices of rock types in the main mass of the sic shows similar enrichment in 37 cl up to 1 34 whereas biotite from the archean country rocks 37 cl 0 88 to 0 53 and associated groundwater are 37 cl depleted the results of this study lead to two important conclusions concerning genetic and exploration models for the footwall ore zones first magmatic end member fluid introduced into the footwall with the melt from which the fwgp crystallized contained very little cu rarely 100 ppm the main ore metal in the footwall ores this result questions hydrothermal models for footwall ore formation that hypothesize that cu and other ore metals were remobilized from sulfide deposits along the sic contact by magmatic hydrothermal fluids and redeposited in the footwall it is more likely that ore metals were only locally remobilized in the footwall ore zones when metal poor hybrid fluids interacted with pre existing sulfide veins of magmatic origin second inclusions containing the hybrid fluid occur in the fwgp rock type throughout the footwall in both mineralized and unmineralized areas therefore although the fwgp preserves stable cl isotope and fluid inclusion evidence that magmatic fluid was introduced into the footwall detection of this magmatic component alone will not serve as a useful exploration method in contrast mapping the distribution and abundance of fwgp may be ore predictive since fwgp emplacement and its higher abundance in mineralized areas appears to have been a structural and textural prerequisite for footwall ore emplacement

observations of east coast upwelling conditions in synthetic aperture radar imagery seasonal coastal upwelling in the u s mid atlantic coastal ocean normally occurs during the summer months because of generally alongshore southerly wind episodes southerly winds force an offshore surface ekman flow over the inner continental shelf colder and nutrient rich waters from below upwell toward the surface replacing offshore flowing surface waters synthetic aperture radar sar observations from the european remote sensing ers satellite ers 2 before and after upwelling favorable wind episodes in early summer 1996 along the new jersey coast are presented lower backscatter conditions appearing in the sar imagery after the onset of upwelling demonstrate the influence of the upwelling regime on the sea surface roughness satellite sea surface temperature sst observations and in situ sea temperature vertical profiles confirm upwelling conditions three key mechanisms are suggested to explain the lower radar returns observed under upwelling conditions an increase in the atmospheric marine boundary layer stability an increase in the viscosity of surface waters and the presence of biogenic surfactants in the upwelling region

data for ashley river to test channel network and river basin heterogeneity concepts to provide data to investigate hypotheses about the evolution of channel networks specifically the optimal channel network concept discharge and channel properties were measured at 336 sites in a 121 km2 basin over a 5 day period of reasonably steady flows the data are also suitable for investigating how discharge increases down river channels the data collection was a major logistical exercise which involved 80 person days in remote field locations in the expectation that the data will be of use to other researchers this paper describes how the data were measured checked and archived the archive is available at http www niwa cri nz hydrology ashpage htm and includes the associated time series of streamflow at the basin outlet and the channel network as plotted on 1 50 000 scale maps

ore metal redistribution by hydrocarbon brine and hydrocarbon halide melt phases north range footwall of the sudbury igneous complex ontario canada we report methane dominant hydrocarbon fluid inclusions ch4 c2h6 c2h2 c3h8 coexisting with primary brine inclusions and secondary halide melt solid nacl inclusions in au pt rich quartz sulfide epidote alteration veins associated with the footwall style cu pge platinum group element au deposits at the fraser mine north range of the sudbury igneous complex evidence for coentrapment of immiscible hydrocarbon brine and hydrocarbon halide melt mixtures is demonstrated a primary ch4 brine assemblage was trapped during quartz growth at relatively low t min ttrapping 145 315 c and p max ptrapping 500 bar prior to the crystallization of sulfide minerals in the veins secondary inclusions contain solid halite and a mixture of ch4 c2h6 c2h2 and c3h8 and were trapped at a minimum t of 710 c the halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally postdate by replacement early alteration quartz hosting the primary lower t brine ch4 assemblage laser ablation icp ms analyses show that the brine hydrocarbon and halide melt inclusions contain significant concentrations of cu 0 1 1 wt range au bi ag and pt all 0 1 10 ppm range cu pt and cu au ratios in the inclusions are significantly up to 4 log units lower than in the host alteration veins and adjacent massive sulfide ore veins suggesting either 1 early cu loss from the volatiles by chalcopyrite precipitation or 2 enhanced au and pt solubilities relative to cu at the temperatures of entrapment concentration ratios between coexisting brine and ch4 inclusions c rm elem rm brine c rm elem rm ch 4 are lower for cu au bi and ag than for other elements na ca fe mn zn pb indicating that during interaction with the brine the hydrocarbon phase was enriched in ore metals the high concentrations of ore metals in hydrocarbon brine and halide melt phases confirm that both aqueous and non aqueous volatiles were carriers of precious metals in the sudbury environment over a wide range of temperatures volatile evolution and magmatic sulfide differentiation were clearly part of a single continuous process in the sudbury footwall the exsolution of h2o poor volatiles from fractionated sulfide liquid may have been a principal mechanism controlling the final distribution of pge and au in the footwall ore systems the study reports the first measurements of precious metal concentrations in fluid inclusions from a magmatic ni cu pge environment the sudbury district

a comparison of sir b synthetic aperture radar data with ocean internal wave measurements an image from the shuttle imaging radar b sir b synthetic aperture radar sar shows internal wave features in an area south of long island new york coincident oceanographic measurements are used in conjunction with hydrodynamic interaction and electromagnetic scattering models to estimate the expected sar image intensity modulations associated with the internal waves there is reasonable agreement between the predicted and observed internal wave signatures

crystallization of sulfide liquids and the interpretation of ore composition we have been exploring ways to quantitatively assess the extent to which fractionation of sulfide melt has effected variations in composition within magmatic sulfide ore bodies our approach has been to determine by experiment the crystallization paths of sulfide liquids in temperature and composition dimensions in this paper the results of new major element partitioning experiments below 1050 c in the nickel free system are presented and summarized along with new and previous work in the fe ni cu s quaternary the partition coefficients d for cu between monosulfid solid solution mss and sulfide liquid in the ni free system dcu wt cu in mss wt cu in liquid cluster near 0 3 but decrease to nearly 0 1 for cu rich s poor liquids near 1000 c dni also declines with decreasing sulfur content of the liquid but increases with decreasing temperature preliminary data indicate that dni exceeds 1 0 in low ni liquids with greater than 16 wt cu at 1050 c the quality of available data on the

nonlinear features of internal waves off baja california as observed from the seasat imaging radar the synthetic aperture radar sar on seasat has yielded well defined images of quasi periodic internal waves in the waters on the west side of baja california these waves occur in groupings separated by 15 23 km each group having 2 20 striations with wavelengths of the order of 300 m or longer they appear in water approximately 200 m deep shoreward of several banks at the continental shelf edge whose depths are as shallow as 15 m the wave surface signatures exhibit clear nonlinear features higher than linear group velocities and decreases in wavelength crest length and amplitude toward the rear of the packet environmental data for the area have been examined and these show a well developed mixed layer low winds and vigorous tidal action thus stratification wind speed tidal current and bottom topography apparently combine to establish proper conditions for tidal generation of internal waves the images have been analyzed from the standpoint of nonlinear wave theory and it is shown that the vertical displacement of an isopycnal surface can be estimated from a combination of sar imagery vertical density profiles and simple theoretical expressions numerical examples are given

role of surface films in ers sar signatures of internal waves on the shelf 1 short period internal waves analysis of synthetic aperture radar sar images of internal waves iws on the iberian shelf and classification of the iw surface signatures is presented there are three types of iw signatures in the form of bright dark dark and bright bands that correspond to positive negative negative or positive variations of radar backscatter respectively strong positive sign iw signatures occur at very low wind velocities less than 2m s at winds higher than 2 m s both positive negative and negative signatures are observed for range propagating iws for azimuth propagating iws negative signatures prevail two groups of experiments carried out in the frame of the multidisciplinary oceanographic research in the eastern north atlantic morena project on the iberian shelf in august 1994 are described 1 iw measurements simultaneous with ers 1 sar overpasses and 2 iw measurements visual observations of the surface and sampling of films from the sea surface iw manifestations at low to moderate winds took the form of slicks locating over iw troughs at the near threshold wind velocity they were of the form of intensified decimeter scale waves antislicks located over iw crests measurements of wave damping due to films collected from the slick and nonslick areas showed the concentration of surfactants and retrieved film elasticity to be higher in the slicks than in the nonslick areas a theoretical model of the surface wave modulation by iws is developed to include surface wave straining by the iw current and surface wave damping due to surfactant films pressure area curves for real marine films are used in the model the relation between the film and the straining effects on the surface wave spectrum in the iw field is shown to depend on film parameters surface wave length and wind velocity the model predicts strong damping of centimeter scale waves over iw troughs mainly due to the film effect and intensification and depression of decimeter scale waves due to both straining and film effects dependencies of the model spectrum variations as a function of wind velocity for range and azimuth propagating iws are obtained the negative sign contrast being shown to predominate for azimuth propagating iws model variations of the spectrum of decimeter scale waves are shown to be significantly sensitive to surfactants film pressure the negative sign contrasts due to films being superimposed on the straining effects and these are eventually capable of suppressing the positive sign contrasts it is concluded that the occurrence of the different classes of iw signatures in the sar images can be explained by the action of surface active films

systematics of chlorite alteration at the phelps dodge massive sulfide deposit matagami quebec hydrothermal alteration at the phelps dodge archcan volcanogenic massive sulfide deposit has converted rhyodacite and rhyolite footwall rocks into the following mineral assemblages quartz chlorite albite epidote or sericite quartz chlorite or sericite chlorite or sericite and chlorite talc or stilpnomelane alteration at constant al was initiated by hydration addition of fe mg silicification and leaching of ca na which produced al saturated chlorites with a wide range of fe fe mg ratios within the assemblage quartz chlorite albite epidote or sericite with continued addition of fe and less mg combined with extensive leaching of quartz the chlorite became al undersaturated quartz chlorite talc assemblage and ultimately formed a rock composed essentially of chlorite the chlorite talc or stilpnomelane assemblage is stable in late crosscutting veinlets and in the ore zone chlorites in the si al mg fe system form a rectangular solid solution plane with limited substitution of al for si and extensive substitution of fe for mg in si al space the solid solution plane is outlined by al saturation presence of other al rich mineral and al undersaturation presence of al poor or al free mineral boundaries al iv substitution for si in the chlorites increases from 2 3 to 3 01 formula units based on 8 si al iv with fe fe mg whereas al iv occupancy decreases from 2 88 to 2 65 the valence charge balance is compensated by octahedral site vacancies or by the conversion of fe super 2 to fe super 3 the al iv content of chlorite also increases with temperature chlorites on the al saturated boundary of the solid solution field form a potentially useful geothermometer t degrees c 106 al iv 18 al iv is corrected for changes with the fe fe mg ratio as al iv corrected al iv 0 7 fe fe mg the fe fe mg ratios of bulk rock and contained chlorite correlate well birefringence colors of the chlorite change from green to brown violet and berlin blue as fe fe mg changes from 0 18 to 0 64 the fe fe mg variation apparently depends largely on the proportions of mg rich seawater and fe rich hydrothermal fluid in the altering brine

preliminary evaluation of trace hydrocarbon speciation and abundance as an exploration tool for footwall style sulfide ores associated with the sudbury igneous complex ontario canada deposits of cu ni platinum group elements pge rich sulfides occur along the north range footwall of the sudbury igneous complex ontario canada the deposits have been modified chemically mineralogically and texturally by multiple syn to postmagmatic hydrothermal events and are hosted mainly within sudbury breccia a contact metamorphosed and hydrothermally altered impact breccia the composition of c1 to c6 unsaturated and saturated hydrocarbons in bulk fluid inclusion volatiles in the matrix of the sudbury breccia was investigated using in line rock crushing gas chromatography gc in order to compare the hydrocarbon composition of this rock type in breccia zones containing economic footwall sulfide deposits at the morrison deposit levack mine north range sudbury ontario with barren breccia zones trace hydrocarbons possibly abiogenic in origin occur throughout the sudbury igneous complex footwall and country rocks investigated however there are differences in the composition and abundance of bulk hydrocarbons released from mineralized and barren sudbury breccia when fluid inclusions are opened volatiles released from samples of sudbury breccia from sulfide mineralized and sulfide barren environments showed the following 1 higher average abundances of light saturated hydrocarbons c1 c4 and an approximately 2 higher total abundance of hydrocarbons mol g of rock basis associated with samples from the mineralized study area and 2 comparable average unsaturated hydrocarbon abundances in both settings but a larger range in unsaturated hydrocarbon abundances in the mineralized study area differences in bulk hydrocarbon abundance and composition reflect differences in the abundance and hydrocarbon content of fluid inclusions trapped in the barren and mineralized sudbury breccia zones in addition the compositional modification of circulating fluids by processes and conditions unique to the mineralized sudbury breccia environment may have occurred prior to inclusion entrapment e g modification by mineral catalysts differences in temperature and oxygen fugacity preliminary spatial analysis of the hydrocarbon distribution within and surrounding the morrison deposit shows that the total hydrocarbon abundance in the sudbury breccia does not change with orebody proximity within a single host breccia zone however volatiles trapped in the sudbury breccia matrix near the top of the footwall deposit where it is physically connected to contact style ni cu pge ores have elevated unsaturated hydrocarbon abundances e g propene compared to other parts of the same breccia zone distal to this zone of physical connection samples of the pge enriched sudbury breccia and mineralized veins containing alteration assemblages characteristic of the footwall ore styles have higher unsaturated hydrocarbon abundances and unsaturated saturated ratios compared to sudbury breccia and vein samples that are pge poor localized enrichments in unsaturated hydrocarbons in sudbury breccia zones may be the result of specific ore minerals and metal complexes involving the pge and group viii metals that acted as catalytic agents modifying the composition of initially light saturated hydrocarbon species prior to entrapment in fluid inclusions to apply the analysis of hydrocarbon compositions in trapped fluid inclusions to discriminating mineralized from barren zones of sudbury breccia samples from targeted areas were compared to samples of barren sudbury breccia background although a large data set is presented here to establish these compositional fields analysis of smaller sample subsets from each environment yields a statistically significant separation between the two environments total hydrocarbon abundance c3 c1 ratios and unsaturated saturated hydrocarbon ratios are useful indicators of sulfide ore proximity and may help delineate regions enriched in pge

overview of the shuttle imaging radar b preliminary scientific results the shuttle imaging radar b experiment consisted of a large number of scientific investigations in the earth sciences nine oceanographic experiments were conducted to study the generation and propagation of surface waves the dynamics of internal waves oil slick detection and the properties of southern polar ice stereo imaging from space allowed three dimensional viewing of surface features geologic experiments were conducted to study subsurface penetration structural mapping and lithologic classification imaging radar angular scatterometry was used in the vegetation cover forest type and urban areas classification experiments this article provides an overview of the scientific results some of which are also presented in this issue

lead isotopes in sulfides from the stillwater complex montana evidence for subsolidus remobilization isotopic ratios of pb in sulfide minerals primarily pyrrhotite chalcopyrite and pentlandite from a suite of samples from the platiniferous j m reef of the stillwater complex were measured to elucidate the temporal and genetic relationship between sulfides and host silicate minerals results indicate that sulfides and coexisting plagioclases are generally not in isotopic equilibrium that both sulfides and feldspars record highly radiogenic initial ratios at 2 7 ga and that a component of post emplacement radiogenic pb has mixed with common pb in the sulfides a model involving introduction of radiogenic pb carried by fluids derived from sources external to the complex is favored analyses of the lead isotopic composition of sulfides in veins which cut the complex indicate that a significant fraction of the radiogenic lead which was added to the sulfides was externally derived during an extensive hydrothermal episode associated with proterozoic regional metamorphism around 1 7 ga the possibility that some fractions of the radiogenic pb may have been derived from primary minerals altered during the low grade metamorphism cannot be discounted the amount of radiogenic lead added is variable and in some cases negligible there is a good correlation between the lead isotope composition and the nature of the secondary mineral assemblage sulfides and plagioclases in samples that show little or no alteration of the primary minerals are generally in isotopic equilibrium and preserve isotope ratios consistent with magmatic crystallization at 2 7 ga samples with the most radiogenic sulfides contain abundant secondary minerals serpentine talc actinolite chlorite and zoisite associated with greenschist facies metamorphism some of the radiogenic pb in the sulfides can be removed by progressive stepwise leaching however in most samples recrystallization of sulfides during metamorphism has mixed common pb and radiogenic pb throughout the crystal structure such that in these samples stepwise leaching does not recover initial pb isotopic ratios plagioclases are much more resistant to low temperature recrystallization and in almost all cases stepwise leaching reveals the initial lead isotopic composition the reactivity of sulfides over a wide temperature range enhances their utility in understanding not only the processes involved in their formation at the time of magmatic emplacement but also postmagmatic processes which were important in the redistribution and enrichment of platinum group elements pge within the ore zone

the significance of partial melting processes in hydrothermal low sulfide cu ni pge mineralization within the footwall of the sudbury igneous complex ontario canada we present new results and review existing data highlighting different aspects of the genetic relationship between partial melting and hydrothermal mineralizing processes in the contact aureole of the sudbury igneous complex at the basal contact of the igneous complex in the footwall breccia crystallized partial melt pods and veins referred to as footwall granophyres are abundant and intrude all rock types including the breccia matrix as well as massive ni cu sulfide ore the final crystallization of these melts was accompanied by the segregation of high salinity fluids dominantly in the temperature range of 450 to 550 c as revealed by ti inquartz thermometry and studies on primary fluid inclusions in mineralized parts of the footwall breccia there is clear evidence that interaction of partial melts exsolved fluids and preexisting magmatic sulfides occurred in the deeper footwall of the sudbury igneous complex similar footwall granophyres occur as networks of veins intruding impact brecciated sudbury breccia country rocks and have an intimate spatial association with hydrothermal low sulfide assemblages highly enriched in pt pd and au with a unique assemblage of pgm including malyshevite and lisiguangite it is suggested that partial melting processes were widespread in the contact and proximal footwall environment of the igneous complex and they were important in providing high salinity magmatic fluids to a hydrothermal system responsible for redistribution of base and precious metals we describe observations which may evidence the migration of partial melts from the contact into the deeper footwall furthermore we suggest a cogenetic model for the precipitation of sulfide hydrous silicate assemblages in close spatial association to footwall granophyres we emphasize that the use of footwall granophyres in mineral exploration for cu ni pge ores in the footwall of the sudbury igneous complex is clearly justified mapping of footwall granophyre vein networks highlights areas that were proximal to the contact environment and point out structural pathways that may have been used by syn or postgenetic mineralizing fluids in a given area widespread partial melting appears to have occurred in the footwall of other large mafic ultramafic complexes such as bushveld and duluth and similar genetic relationships of partial melting and ore forming hydrothermal processes may have possibly existed also in these systems

geochronology geochemical and sr nd hf pb isotopic compositions of the granitoids in the yemaquan orefield east kunlun orogenic belt northern qinghai tibet plateau implications for magmatic fractional crystallization and sub solidus hydrothermal alteration abstract a general consensus has emerged that high field strength elements hfse can mobile to some extent in a hydrothermal fluid however there are hot debates on whether sub solidus hydrothermal alteration can lower the nb ta ratio in evolved melts in this study we present petrography geochronology and geochemistry of the barren and mineralized rocks in the yemaquan skarn iron deposit northern qinghai tibet plateau to probe magmatic hydrothermal transition the barren rocks consist of diorites granodiorites granites and syenogranites whereas the porphyritic granodiorites are associated with mineralization for an excellent consistency between the magmatic zircon u pb age 225 2 ma and the hydrothermal phlogopite 40 ar 39 ar age 225 1 5 ma the sr nd hf pb isotopic data demonstrate that the yemaquan granitoids are originated from a relatively homogenous enriched mantle with different degrees of crust contamination assimilation fractional crystallization afc trace elements signatures indicate that the porphyritic granodiorites related to mineralization display amphibole crystallization for high water contents whereas the barren granites have gone through biotite crystallization due to potassium enrichment by continuous upper crust contamination both of which are responsible for their nb ta ratios respectively modeling results suggest that a basaltic melt with nb ta ratio of 15 3 can reach a minimum nb ta ratio of 12 in the producing granodioritic melt by amphibole fractional crystallization based on partition coefficients of nb and ta between amphibole and melts from previous experiments this may explain the average nb ta ratio 13 7 of the barren granodiorites while it cannot account for the average nb ta ratio 8 4 of the mineralized porphyritic granodiorites and it is even lower than that of the granites 10 3 with biotite fractional crystallization exsolution of a magmatic hydrothermal fluid is inevitable when a water saturated magma emplaced in shallow crust leading to a transportation of certain chemical components from the magmatic melts to exsolved fluids because nb seems more mobile than ta in fluorine bearing fluids we contend that a preferentially transport nb over ta by sub solidus hydrothermal alteration can further lower the nb ta ratios of the mineralized porphyritic granodiorites which may also result in a broad range of hfse contents and their ratios in the altered porphyritic granodiorites formed in a post magmatic process

fluid mineral equilibria in prehnite pumpellyite to greenschist facies metabasites near flin flon manitoba canada implications for petrogenetic grids a sequence of regional metamorphic isograds indicating a range from prehnite pumpellyite to lower amphibolite facies was mapped in metabasites near flin flon manitoba the lowest grade rocks contain prehnite pumpellyite and are cut by younger brittle faults containing epidote chlorite calcite isobaric temperature xco2 and pressure temperature constant xco2 diagrams were calculated to quantify the effects of co2 in the metamorphic fluid on the stability of prehnite pumpellyite facies minerals in metabasites containing excess quartz and chlorite prehnite and to a lesser extent pumpellyite are stable only in fluids with xco2 0 002 epidote chlorite calcite assemblages are stable our calculated phase relations are consistent with regional metamorphism in the flin flon area in the presence of an h2o rich fluid and a more co2 rich fluid in the later fault zones we believe that the potential effects of small amounts of co2 in the metamorphic fluid should be assessed when considering the pressure temperature implications of mineral assemblages in low grade metabasites

multiple fluid generations in the sudbury igneous complex fluid inclusion ar o h rb and sr evidence abstract the elliptically zoned sudbury structure in northern ontario is host to world class nickel copper pge deposits which are generally regarded as the products of a single magmatic event however there is increasing evidence of multi episodic fluid rock including ni cu sulphide interactions in the sudbury structure that range from early remobilization of the cooling ores ca 1850 ma through metamorphism and deformation related to the penokean orogeny to neotectonic fracturing ca 5 13 ma previous fluid inclusion studies have identified an h2o nacl co2 kcl fluid of highly variable phase ratios intimately associated with the ores and a distinct population of primary two phase fluid inclusions associated with post intrusion metasomatic alteration this study introduces two new distinct populations of fluid inclusions 1 a population represented by two phase co2 bearing fluid inclusions hosted along healed fracture planes in quartz that offset ore minerals that was trapped between 280 340 c and 1750 to 3500 bars pressure as the fluid inclusion trails offset and therefore post date the ore their genesis is consistent with a late penokean 1 83 1 89 ga or later ca 1450 contractional event 2 a two phase highly saline 16 wt nacl equivalent fluid hosted within neotectonic 5 13 ma rb sr galena sphalerite calcite quartz chlorite veins inclusions of this fluid were trapped at temperatures ranging from 60 to 135 c and maximum confining pressures of 950 bars stable isotope data o d from biotite amphibole and epidote from the alteration assemblages of remobilized veins within the sudbury structure show distinct evidence of a mixing trend of fluids originating within or near the magmatic water box and trending towards a metamorphic fluid of isotopic composition similar to an evolved sudbury structure groundwater ar ar data from the amphiboles within sudbury intrusive complex sic footwall breccia from the craig mine are consistent with a mixed ar ar spectrum the step heating ar release spectrum yields ages ranging from ca 1800 ma at the low temperature end to approximately 2640 ma for high temperature steps these dates are in agreement with the ca 1850 and 2647 ma ages for the sic and levack gneisses respectively and are interpreted as the reinjection of country rocks partially melted by the sic back into the sudbury structure the isotopic evidence for mixed fluids derived from a combination of a magmatic fluid and a regional groundwater metamorphic fluid suggests that the highly variable phase ratio fluid inclusions associated with the ore may be divided into two end member fluids represented by an exsolved sic fluid and a regional groundwater metamorphic fluid this is consistent with at least five distinct fluids being present during the evolution of the sudbury structure

platinum palladium gold copper rich stringers at the strathcona mine sudbury their enrichment by fractionation of a sulfide liquid recent study of the platinum group elements pge in the strathcona ni cu sulfide deposit has shown that their distribution is zoned pt pd au and cu increase progressively from the hanging wall ore zone through the main zone into the deep ore zone rh ru ir and os show a reverse trend naldrett et al 1982 the copper and deep copper zones at strathcona are the farthest away from contact with the sudbury igneous complex and consist of veins of massive sulfides up to 6 m in width which narrow down to thin veins

multi stage hydrothermal processes involved in low sulfide cu ni pge mineralization in the footwall of the sudbury igneous complex canada amy lake pge zone east range the amy lake pge zone is a low sulfide type cu ni pge mineralization in the east range footwall of the 1 85 ga sudbury igneous complex occurring in a 100 m wide sudbury breccia belt that coincides with an impact related major fracture zone bay fault zone detailed hydrothermal alteration mapping fluid inclusion trace element and stable isotope studies revealed a complex alteration and mineralization history in a multi source multi stage sudbury related hydrothermal system the two major stages of syn sudbury hydrothermal activity are characterized by similarly high salinity high temperature fluids that are 1 locally derived from footwall granophyre bodies and typified with high ni cu and pge s ratios and high ree contents magmatic hydrothermal stage and 2 a more voluminous cu ni pge rich fluid flux probably originated from the sudbury igneous complex footwall contact hydrothermal stage the second hydrothermal flux was introduced by brittle fractures in the area and resulted in a complex zonation of alteration assemblages and mineralization governed by local footwall composition the sudbury related hydrothermal event was overprinted by shear related epidote veining and calcite chlorite replacement both regionally present in the sudbury structure based on analogies the most important factors involved in the formation of hydrothermal low sulfide mineralization are proposed to be 1 accumulation of pge enriched fluids 2 large scale brittle structures as conduits to these fluids and 3 adequate host rock composition as a chemical trap resulting in sulfide and pgm precipitation in environments meeting these criteria hydrothermal pge mineralization is known to have formed not only in the sudbury footwall but also from mafic ultramafic intrusions associated with primary magmatic pge from several locations around the world

textural development in sulfide matrix ore breccias in the voisey s bay ni cu co deposit labrador canada abstract magmatic ni cu sulfide ores at voisey s bay contain complex assemblages of extremely heterogeneous rocks these range from polymict breccias with rock fragments in sulfide rich and or sulfide poor matrices to heterogeneous vari textured gabbros with rapid short range variations in grain size and content of hydrous phases rock fragment populations in the breccias include endogenous olivine gabbros cumulate and non cumulate and cumulate peridotites along with extensively depleted plagioclase hercynite gneisses interpreted as restites from extensive partial melting of country rock quartzo feldspathic paragneisses using a combination of desk top microbeam xrf mapping at cm scale and 3d x ray tomography we show that both sulfide poor and sulfide rich breccias comprise heterolithic assemblages of clasts within a matrix of olivine gabbro this matrix is characterised by an interconnected 3d framework of plagioclase crystals highly variable in grain size at mm to cm scale with interstitial olivine and poikilitic clinopyroxene and is texturally indistinguishable from clast free olivine gabbro sulfide forms interconnected networks at cm to dm scale and possibly larger much of the plagioclase developed by outgrowth from the margins of paragneiss xenoliths when the porosity was occupied by silicate melt the observed range of textures is explained by a model of percolation of molten sulfide through variably crystalline inter clast matrix displacing the silicate melt to leave the refractory plagioclase olivine or in some cases plagioclase only component now entirely within a sulfide matrix the process is analogous to that believed to have formed interspinifex ore in komatiite hosted deposits biotite rims on plagioclase enclosed in sulfide are interpreted as the result of reaction between plagioclase olivine and a hydrous component derived from the sulfide melt itself with a possible component of migrating residual silicate melt wicking along sulfide silicate contacts this sulfide infiltration model offers an alternative to the current model for upward emplacement of a slurry of silicate melt sulfide melt and breccia fragments as a late stage injection into the dyke sill complex the preserved range of textures is interpreted as being due to gravity driven percolation of sulfide liquid through a pre existing partially molten intrusion breccia in this model the breccia serves as a physical trap site accumulating downward migrating sulfide liquid however the invariable close mutual association of sulfide and rock fragments at voisey s bay implies a common derivation

ocean surface features and currents measured with synthetic aperture radar interferometry and hf radar this paper describes the results of the first quantitative comparison between high resolution ocean surface current fields extracted from interferometric synthetic aperture radar insar measurements and those from a high frequency hf ocean surface current radar oscr system data from each of these radar systems along with supporting measurements from shipboard and buoy mounted sensors were collected during the high resolution remote sensing experiment high res on june 20 1993 on the continental shelf off the coast of cape hatteras north carolina both components of the surface current were obtained from the insar system at roughly 10 m resolution from two orthogonal flight legs over the region separated in time by about 30 min the oscr system measured two dimensional surface current vectors at about 1 km resolution over this same region while the usns bartlett was collecting hydrographic samples and near surface current measurements two dimensional wave spectra as well as meteorological and additional current measurements were collected at two buoys within the experimental area we discuss in the paper two techniques for eliminating the effect of surface wave motion on the insar current estimates one method relies on some knowledge of the local wind and wave field and the use of a microwave scattering model the other method makes use of a few in situ current measurements spaced at different range locations across the insar image using either of these techniques we find that the agreement between the insar and oscr current estimates is generally very good furthermore the insar current and magnitude imagery show the presence of undulating surface features where abrupt changes in the current speed and direction occurred the ship surveys indicate that these features were caused by the collision of water masses of different density we show for the first time in this paper a high resolution area extensive vector surface current map derived from the insar of the two dimensional flow in the vicinity of these features our results demonstrate convincingly that high resolution oceanic surface current vectors can be derived from insar current measurements and that these measurements may be very beneficial for detailed studies of the dynamics of small scale surface features in regions of strong current divergences or shears

high chlorine alteration minerals and calcium rich brines in fluid inclusions from the strathcona deep copper zone sudbury ontario the strathcona deep copper zone consists of a complex suite of massive sulfide veins that occupy a series of fractures in the footwall gneisses and sudbury breccia it is characterized by the occurrence of branching quartz veinlets and hydrothermal alteration selvages along the margins of massive sulfide veins hornblende or actinolite epidote calcite and ferropyrosmalite fe mn 8 si 6 o 15 oh c1 10 occur in the inner zones of the alteration selvages adjacent to the massive sulfide veins annite chlorite and albite are developed in the outer zones fe rich silicates of the alteration assemblages contain significant amounts of chlorine ferropyrosmalite contains 5 79 to 6 54 wt percent cl hornblende contains up to 2 99 wt percent cl annite contains up to 2 13 wt percent cl primary fluid inclusions in the quartz from the branching veinlets are mutiphase consisting of vapor liquid and more than four solids the solid crystals of opened inclusions identified by scanning electron microscope are na ca k k pb k fe and fe mn chlorides the sequence of melting events and the nature of the solid phases suggest that the trapped fluids are nacl cacl 2 h 2 o solutions with minor k fe mn and pb these fluid inclusions are highly saline avg 60 wt nacl cacl 2 calcium rich ca na 1 by weight and homogenize to liquid at temperatures 260 degrees to 420 degrees c 342 degrees or 35 degrees c mean or std dev two options are proposed for the origin of the fluids melt fluid phase separation during sulfide liquid crystallization and convection of ambient fluids across the contact of the sulfide veins the cl rich fluids may have participated in the precipitation of pd and probably other platinum group elements pge at a later stage but they did not transport the pge very far from the magmatic sulfide veins

a new analytical model for internal solitons in the ocean abstract a new model for tidally generated internal solitons in the ocean is advanced based on a little known asymptotic analytical solution to the weakly nonlinear korteweg de vries equation the solution has many of the properties observed in oceanic internal solitary waves solitons it has been adapted to simulate the dynamics of stratified fluid flow driven by tidal forcing at continental shelves and sills and the adaptation describes the canonical behavior of such solitary wave trains it is shown that the solitons are positioned at the leading edge of an internal tidal bore on the shelf and that the distance between successive packets of solitons constitutes the internal tidal wavelength a future paper will apply the model to field observations from four geographical regions

multiple hydrothermal processes in footwall units of the north range sudbury igneous complex canada and implications for the genesis of vein type cu ni pge deposits systematic regional sampling along the contact zone of the 1 85 ga age sudbury igneous complex with the archean levack gneiss footwall in the north range of the sudbury structure revealed textural mineralogical and fluid inclusion systematics of post sudbury igneous complex hydrothermal processes that affected the various lithologies at late stages of emplacement of the sudbury igneous complex and formation of magmatic fe ni cu sulfide deposits a partial melt from the levack gneiss invaded the contact zone this partial melt is revealed by small microdikes and irregular bodies of granophyric quartz plagioclase with megacrysts of hornblende clinopyroxene and titanite plagioclase hornblende equilibrium was established at 750 to 800 c and 1 10 to 1 55 kbars pressure corresponding to about a 4 to 6 km depth under lithostatic conditions f cl wt percent ratios around 15 for accessory apatite and hornblende indicate that a cl rich fluid phase separated during the crystallization of the footwall granophyre this is expressed as miarolites the cl rich fluid 50 wt nacl equiv salinity was trapped as primary fluid inclusions in quartz at around 480 c minimum temperature and around 1 1 kbars minimum pressure during supercooling these inclusions are rich in ca fe mn and k as well as na chloride this fluid may have interacted with earlier primary magmatic sulfide causing remobilization and reprecipitation of cu ni platinum group elements pge in veins and disseminations in the footwall these veins are parallel to the sudbury igneous complex footwall contact and are characterized by chalcopyrite pentlandite millerite magnetite stilpnomelane ferropyrosmalite epidote and chlorite michenerite moncheite merenskyite froodite insizwaite sobolevskite gold and bi ni sulfides are associated with sulfides epidote quartz actinolite and chlorite are common in the alteration selvages of the veins compositions and assemblages of platinum group minerals pgm indicate their precipitation below 575 to 485 c primary highly saline fluid inclusions about 40 wt nacl equiv in quartz indicate crystallization at 400 to 480 c and around 1 6 kbars minimum t and p respectively late carbonate epidote actinolite chlorite veins and alteration overprinted the earlier assemblages at about 300 to 400 c with some bornite millerite native silver and other bi sulfides the second stage of hydrothermal activity is characterized by regional carbonic aqueous nacl co 2 ch 4 h 2 o type immiscible fluids that were trapped as secondary inclusions in quartz from various lithologies no mineralization is related to this stage along the north range boiling of these fluids took place during a pressure drop from lithostatic to hydrostatic conditions during uplift from about a 5 to 6 to a 3 to 4 km depth at 300 to 350 c high 20 26 wt nacl equiv and low salinity 6 12 wt nacl equiv fluids coexisted with different carbonic species contents the predominant north south and northwest southeast orientations of fluid inclusion planes reveal that mobilization of carbonic aqueous solutions may be related to the northwesterly oriented thrusting in the sudbury structure during the late stages 1 8 1 7 ga of the penokean orogeny and to predominantly north south faulting in the north range the third stage of fluid mobilization also took place mostly along northerly and northwesterly oriented fractures aqueous fluids were ca rich brines 20 40 wt salinity with temperatures between 150 and 250 c some of these fluids also circulated in fractures parallel to the sudbury igneous complex footwall contact ne sw thus they locally may have interacted with the earlier sulfide assemblages and are also responsible for formation of late veinlets with chalcopyrite epidote quartz chlorite assemblages mobilization of these fluids took place under litho and hydrostatic conditions at about a 4 to 6 km depth this hydrothermal activity is related to a regional tectonothermal event during emplacement of northwesterly oriented sudbury dikes 1 24 ga regional scale fluid inclusion studies along the north range highlight the role of multiple hydrothermal processes in the metallogenic evolution of the sudbury igneous complex and especially in the distribution of copper and precious metals in the footwall units

reconstructing the geochemical signature of sudbury breccia ontario canada implications for its formation and trace metal content the sudbury breccia is an impact generated pseudotachylitic breccia formed in the footwall of the 1 85 ga sudbury igneous complex in ontario canada the breccia is commonly developed in areas of contrasting country rock types and it represents a common host to footwall style cu ni platinum group element sulfide mineralization developed in the immediate footwall of large contact type ni cu rich ore deposits at the base of the sudbury igneous complex three models have been proposed for the genesis of the sudbury breccia 1 in situ frictional or shock melting of target rocks 2 cataclasis of the target rocks and or 3 injection of allochthonous impact melt from the sudbury igneous complex into the brecciated crater floor this study reports new mineralogical and geochemical data for samples of sudbury breccia and associated host rocks both proximal and distal to mineralization from six different locations around the sudbury structure a mixing model was used to construct the composition of the sudbury breccia matrix using a combination of country rock and quartz diorite from the offset dikes which are believed to provide an estimate of the composition of the early melt sheet we demonstrate that the breccia matrix can be successfully modeled from footwall lithologies with no requirement for a contribution from the impact melt sheet instead we propose a dynamic parautochthonous in situ melt model where the matrix of the breccia was derived in part by high temperature melting of footwall lithologies these inclusion and crystal laden melts were mixed and transported into tensile fracture zones that developed adjacent to weaknesses in the country rocks principal component analysis of sudbury breccia indicates that the trace metal content within the breccia that developed distal from mineralization is associated with assimilation of mafic units in the footwall in contrast the matrix of sudbury breccia developed closer to mineral zones has a contribution of metal derived from the fractionated sulfide melt and or a contribution of hydrothermally remobilized metal thus by comparing the trace metal content in sudbury breccia with local footwall lithologies baselines can be established that can help to identify anomalous metal contributions that may be derived from the periphery of a footwall mineral system

the trace metal content of amphibole as a proximity indicator for cu ni pge mineralization in the footwall of the sudbury igneous complex ontario canada alteration veins containing cl poor actinolite and actinolitic hornblende are a common feature throughout the archean aged gneisses and granitoids along the northern margin of the sudbury igneous complex ontario canada crosscutting relations and structural measurements show that the veins postdate the sudbury impact event but predate the emplacement of footwall style cu ni pge platinum group element sulfide ores the veins are four to five times more abundant in brecciated mineralized outcrop than in unbrecciated barren outcrop analyses of vein hosted amphibole by electron microprobe emp and laser ablation icp ms la icp ms show elevated concentrations of ni up to 100 times background increasing from 100 ppm to 1 0 wt cu up to 4 times background and sn up to 2 5 times background in proximity to sulfide veins copper and sn contents in amphibole are only anomalous within 10 to 20 m of mineralization and require quantification by la icp ms however anomalous ni concentrations in vein hosted amphibole may be detected with a high level of confidence solely by emp up to 700 m from mineralization in rocks that contain no visible sulfides in hand sample or thin section and show no bulk rock ni or cu anomalies the relationship between the ni content in amphibole in ppm and mineralization proximity distance d in meters is given by the following equation batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document ni amp 5100 d 0 45 end document the data indicate wide scale ni mobility in hydrothermal solutions in the sudbury footwall the formation of ni rich amphibole in the fracture networks by either the growth of primary ni rich amphibole or metasomatic ni enrichment of preexisting ni poor amphibole was associated with circulation of a sodium and halogen rich fluid between 390o and 550oc nickel may have been released into the footwall environment by extensive hydrothermal alteration of ni rich contact style sulfide ores that lie in the hanging wall of the cu rich footwall style ores in the footwall rocks pre existing fracture networks now amphibole bearing veins acted as common structural pathways first for the circulation of early ni rich fluids associated with leaching in the contact region and the onset of footwall mineralization and second for the emplacement of cu rich footwall style sulfide veins other metal concentrations in amphibole pb zn co show no relationship to mineralization proximity these metals may have been derived locally from country rocks during alteration reactions that promoted amphibole growth in the fractures identification of fracture hosted amphibole with anomalous ni contents in thin section or ni cu sn anomalous amphibole grains liberated from surface weathered rocks hosting sulfide veins may serve as useful proximity indicators for hidden footwall style sulfide deposits at sudbury

hydrothermal remobilisation around a deformed and remobilised komatiite hosted ni cu pge deposit sarah s find agnew wiluna greenstone belt yilgarn craton western australia the sarah s find nickel deposit located 4 5 km north of the mount keith nickel mine western australia was chosen as a case study to investigate the nature and three dimensional geometry of a geochemical halo created by the hydrothermal remobilisation of base metals and platinum group elements into the country rock surrounding a small massive ni sulphide orebody portable and laboratory based xrf analyses were carried out on samples from a shear zone localised along the basal komatiite dacite contact that hosts the orebody a geochemical halo was identified that extends along the shear zone up to 1780 m away from the massive sulphides parallel to a prominent stretching lineation elevated ni and pd are associated with high as co cu and s palladium and pt concentrations increase with proximity to massive sulphides from 6 to 1190 ppb pd these anomalous concentrations reflect the presence of sulfarsenides and sulphides either physically remobilised and forming veinlets close to the massive sulphides or hydrothermally transported and redeposited within the foliation in situ laser ablation icp ms indicates that pd and pt are hosted within these nickel sulfarsenides this ni co as pd geochemical halo observed around the sarah s find ore body is interpreted as forming syn deformation by the circulation of as rich hydrothermal fluids dissolving base metals pd and pt from the orebody and redepositing them along the sheared footwall contact similar ni co pd pt as geochemical haloes could potentially exist around any magmatic nickel sulphide mineral system that has undergone a phase of arsenic metasomatism and may be a generally applicable proximity indicator for nickel sulphides in hydrothermally altered terranes

measurements of the internal wave wake of a ship in a highly stratified sea loch an internal wave experiment was conducted in loch linnhe scotland in which three ships were used to generate internal wave wakes synthetic aperture radar images of the wakes confirmed the applicability of the kinematic theory of keller and munk for the geometry of the wave pattern the waves were measured in situ using three axis current meters and other instrumentation the waves were quite well represented by linear propagation theory although the dependence of amplitude on depth did not agree precisely the time varying frequency of the waves was determined from the data in two different ways including a hubert transform method and agreed well with that predicted by the theory the subsurface data were used to estimate the surface current and its gradient the strain rate any dependence of wave amplitude on ship speed was weak enough to be obscured by variations due to changes in the stratification amplitude estimates of waves from the 1400 and 5300 tonne ships were similar those from the 29 000 tonne ship were 2 3 times greater

heavy mineral weathering under acidic soil conditions abstract the weathering of heavy minerals in acid soil profiles ph 4 5 has been studied in terms of their relative mineral proportions and by using the surface etching features of apatite and hornblende grains an increasing stability order of apatite titanite hornblende garnet epidote zircon is found in the 45 63 m coarse silt fraction of soils developed on tills in southwestern sweden in glaciofluvial deposits sorting processes during deposition have largely determined the variations in heavy mineral content of soils and only the dissolution of apatite is significant hornblende etching is more extensive in soils with low hornblende content indicating that the release of cations relative to the amount of hornblende is greater in such soils

mineralogy of ni cu platinum group element sulfide ore in the 800 and 810 orebodies copper cliff south mine and p t x conditions during the formation of platinum group minerals the 800 and 810 orebodies are two major deposits in the copper cliff south mine located at opposite contacts between the quartz diorite of the copper cliff offset dike and metapelite of the mckim formation the copper cliff south mine is one of the richest cu ni platinum group elements pge deposits in the copper cliff offset dike the ore is composed of variable proportions of pyrrhotite chalcopyrite and pentlandite and occurs as massive sulfides semimassive sulfides with inclusions of quartz diorite and wall rocks net textured sulfides disseminated sulfides and veins sphalerite and magnetite are also present in minor amounts the primary magmatic minerals in the quartz diorite are plagioclase quartz amphibole and biotite the most common platinum group mineral pgm in the copper cliff south mine is sperrylite ptas 2 it occurs in every textural type of ore typically enclosed by chalcopyrite pyrrhotite pentlandite cobaltite and hydrous silicates such as chlorite amphibole and epidote sperrylite may be homogeneous zoned with sb rich cores and sb poor rims associated with hollingworthite rhass and cobaltite or it may contain inclusions the pd bearing minerals are froodite pdbi 2 and michenerite pdbite which are most commonly enclosed by silicates chlorite biotite quartz or chalcopyrite hollingworthite invariably occurs in the center of zoned cobaltite in veins or in disseminated sulfides argentian gold au 0 56 ag 0 44 occurs as small grains in chalcopyrite and in a veinlet with parkerite ni 2 bi 3 s 2 the most abundant ag mineral is hessite ag 2 te which is present in almost every sample with galena gersdorffite and locally pgm volynskite agbite 2 occurs as a zoned grain with tsumoite bite in the center the most common trace minerals spatially and genetically associated with pgm are tsumoite galena gersdorffite cobaltite hessite melonite and native te the copper cliff south mine area was affected by more than one hydrothermal event deformation and metamorphism all of which affected the primary igneous textures and mineralogy of the rocks the first hydrothermal event was responsible for the extensive remobilization of metals including some pge this is revealed by the presence of pgm in large veins in quartz diorite and metapelite and by chlorite amphibole epidote biotite and quartz that often enclose pgm the temperature at the time of this event was estimated in samples containing garnet and biotite in equilibrium to be 327 to 540 c pressure estimated using amphibole chemistry may have been as high as 3 to 4 kbars the fluid responsible for the transport of metals was very rich in cl and oxidizing the fluid composition temperature and or pressure changed with time suggested by the presence of zoned minerals including sperrylite gersdorffite and cobaltite based on the textural relationships sperrylite precipitated before tellurides and galena and after or at the same time as michenerite a second hydrothermal event produced calcite bearing veinlets that cut larger veins