structural controls on sulfide mobilization at the high grade flying fox ni cu pge sulfide deposit forrestania greenstone belt western australia the flying fox komatiite hosted ni deposit is located in the forrestania greenstone belt of the yilgarn craton in western australia the host volcanosedimentary succession has been metamorphosed to amphibolite facies and deformation has sheared and dismembered the orebody creating 11 distinct ore shoots the ore shoots are hosted at the base of a komatiite sequence structurally overlying deformed metasedimentary rocks the ni sulfide orebody has undergone six phases of deformation 1 d 1areg e w compression resulted in tilting of the stratigraphy 2 d 1bff continued e w compression resulted in coaxial flattening along the footwall sedimentary rock sulfide komatiite contact and the basalt hanging wall sedimentary rock contact 3 d 2ff ene wsw compression resulted in noncoaxial shearing of the d 1bff structures 4 d 3ff ese wnw compression resulted in shallow angle thrusts 5 d 4ff during e w extension normal ductile brittle faults formed by the pooling and dilation of granitic magma along the f 2 structural contact between the footwall sedimentary and komatiite rocks and 6 d 5ff intrusion of a proterozoic dolerite dike during n s extension accompanied by late stage brittle normal faulting during deformation the ni sulfides reverted to monosulfide solid solution mss and were mechanically relocated along the footwall sedimentary rock komatiite contact offset into the footwall sedimentary rocks and entrained in the granitic magma creating atypical granite hosted sulfides the ni sulfides were mobilized up to 5 m away from the ultramafic rocks during the d 1 and d 2 events however subsequent dismemberment of the original orebody into separate ore shoots along flat lying faults during the d 3 event led to offsets of up to 300 m the detailed structural analysis of the flying fox deposit has shown that restoration of the lithostratigraphy along known faults can be used to define the volcanic stratigraphy including primary ni ore horizons this information can be used as a guide to the location of concealed extensions to known ore shoots or completely unknown orebodies at depth or along strike

radar imaging mechanism of marine sand waves at very low grazing angle illumination caused by unique hydrodynamic interactions 1 the investigations carried out between 2002 and 2004 during six field experiments within the operational radar and optical mapping in monitoring hydrodynamic morphodynamic and environmental parameters for coastal management oroma project aimed to improve the effectiveness of new remote sensing monitoring technologies such as shipborne imaging radars in coastal waters the coastal monitoring radar of the gkss research center geesthacht germany is based on a kelvin hughes rsr 1000 x band 9 42 ghz vertical vv polarized river radar and was mounted on board the research vessel ludwig prandtl during the experiments in the lister tief a tidal inlet of the german bight in the north sea the important progress realized in this investigation is the availability of calibrated x band radar data another central point of the study is to demonstrate the applicability of the quasi specular scattering theory in combination with the weak hydrodynamic interaction theory for the radar imaging mechanism of the seabed radar data have been taken at very low grazing angles 2 6 of flood and ebb tide oriented sand wave signatures at the sea surface during ebb tidal current phases current speeds perpendicular to the sand wave crest 0 6 m s 1 have been measured at wind speeds 4 5 m s 1 and water depths 25 m the difference between the maximum measured and simulated normalized radar cross section nrcs modulation of the ebb tide oriented sand wave is 27 for the flood tide oriented sand wave a difference of 21 has been calculated the difference between the minimum measured and simulated nrcs modulation of the ebb tide oriented sand wave is 10 and for the flood tide oriented sand wave a value of 43 has been derived phases of measured and simulated nrcs modulations correspond to asymmetric sand wave slopes the results of the simulated nrcs modulation show the qualitative trend but do not always quantitatively match the measured nrcs modulation profiles because the quasi specular scattering theory at very low grazing angle is a first order theory

quantitative mass balance of platinum group elements in the kelly lake ni cu pge deposit copper cliff offset sudbury a mineralogical mass balance has been calculated for the fraction of platinum group elements pge incorporated as solid solution in sulfides and sulfarsenides and the fraction that occurs as major constituents in platinum group minerals pgm in the kelly lake ni cu pge sulfide deposit in the copper cliff offset sudbury low levels of pge in sulfides were determined quantitatively for the first time in sudbury ores by laser ablation microprobe inductively coupled plasma mass spectrometry lam icp ms providing significantly more accurate data on the inventory and mineralogical distribution of the pge than in previous studies the majority of the pt 98 rh 97 and ir 86 91 and lesser but still large fractions of pd 77 87 and ru 67 71 occur as discrete pgm with the remainder occurring in decreasing abundance in solid solution in gersdorffite 1 700 ppm pge pentlandite 1 35 ppm chalcopyrite 0 5 ppm and pyrrhotite 0 3 ppm although the pge are present in low concentrations in sulfides the abundances of these phases can be high enough to constitute a significant fraction of the total pge in particular significant proportions of the pd 14 23 and ru 30 in the kelly lake samples are hosted by sulfides and sulfarsenides this has important implications for the genesis of the pge for the redistribution of the pge during cooling and hydrothermal alteration and for metal recovery during ore beneficiation

radar imaging mechanism of the seabed results of the c star experiment in 1996 with special emphasis on the relaxation rate of short waves due to current variations abstract during the field experiment of the coastal sediment transport assessment using sar imagery project of the marine science and technology program of the european commission an air sea interaction drift buoy asib system was equipped with special sensors and instruments to measure the position the water depth the surface current velocity and direction the modulation characteristics of short wave energies and relevant air sea interaction parameters due to undulations in the seabed the asib system was operated from on board a research vessel and the data were measured while the buoy drifted in the tidal currents across sand waves of the study area all buoy measurements were analyzed by computing frequency spectra of low and high frequency waves scalar spectra between 0 1 and 50 hz the whole range of short water waves was recorded by these in situ measurements on board the buoy which is responsible for the backscattering of commonly used air and spaceborne imaging radars a comprehensive da

the nickel sulfide mineralization and metamorphic setting of the forrestania area western australia the forrestania group of nickel sulfide occurrences of the archean southern cross province is localized in intrusive dunite bodies at the base of a lower komatiite unit which is interlayered with tholeiitic mafic rocks para amphibolites quartz biotite schists chemical sedimentary rocks iron formation and sulfide cherts and komatiites concordant lenticular metamor phosed sill like mineralized dunites have komatiitic affinities and appear to be feeder chambers to overlying thick sequences of dominantly extrusive ultramafic komatiites and rare pyroclastic komatiites unmineralized portions of the dunites are extremely rich in magnesium with mgo values ranging between 45 and 51 percent the important nickel sulfide occurrences are pentlandite rich disseminations distributed in the basal portions of metamorphosed intrusive dunites e g cosmic boy and digger rocks south digger rocks similar mineralization also occurs in hanging wall and internal portions of dunites but is generally of less importance than the basal mineralization because of lower nickel tenor massive pyrrhotite rich sulfides occur within reaction zones between dunite and footwall country rocks and as remobilized veins and stringers in footwall metasediments this type of mineralization forms important small tonnage high grade deposits at new morning and flying fox supergene alteration of primary sulfides is extensive and massive violarite pyrite magnetite zones are developed in weathering profiles polyphase deformation and metamorphism with peak conditions estimated at 655 degrees or 30 degrees c and 4 0 or 1 0 kb resulted in widespread recrystallization and tectonic remobilization of ductile sulfides cumulate dunites were metamorphosed to bladed granular and granoblastic aggregates of forsterite talc forsterite talc anthophyllite and forsterite talc enstatite formed under varying f sub co 2 and f sub h 2 o conditions retrograde serpentinization and talc carbonate alteration followed by later supergene alteration has caused textural modification and oxidation of primary sulfides with development of pyrite violarite and magnetite rich ores nickel values and ni cu ratios vary for different types of mineralization the economically important basal disseminations of pentlandite pyrite pyrrhotite chalcopyrite have ni values in the range 2 to 5 percent and constant ni cu ratios in the range 14 1 to 22 1 bulk composition of primary sulfides of this type at cosmic boy is s rich with fe 39 4 percent ni co 18 6 percent and s 42 0 percent massive remobilized veins of pyrrhotite pentlandite pyrite chalcopyrite have high ni 3 to 8 and erratic ni cu ratios generally in the range from 10 1 to 200 1 with a mean of 45 1 this mineralization is fe rich with fe 50 4 percent ni co 7 4 percent and s 42 2 percent broad irregular sparse disseminations less than 2 of pentlandite heazlewood chalcopyrite form in the internal portions of cumulate and metamorphosed dunites they have low ni 0 3 to 0 5 high ni cu ratio 50 1 to 100 1 and bulk composition close to pentlandite composition with fe 31 8 percent ni co 34 2 percent and s 34 0 percent the bulk compositions of sulfides generally plot on the s rich side of the monosulfide solid solution field at 650 degrees c and this appears to reflect nickel and sulfur mobility during retrograde metamorphism

controls on porphyry cu mineralization around hanza mountain south east of iran an analysis of structural evolution from remote sensing geophysical geochemical and geological data abstract hanza mountain in urmia dokhtar magmatic arc southeast of iran consists of monocline of eocene volcanic rocks into which the oligocene granitoid rocks have been intruded this area has excellent potential for economic porphyry copper deposits with bondar hanza daralu and sarmesk deposits among them hanza mountain is located between nw se horsetail thrust faults derived from the gowk and sabzevaran strike slip faults the analysis of the kinematics of these strike slip faults shows that they were not the cause of the formation of the pull apart basin thus they have not directly played any effective role in localizing the final emplacement of porphyries responsible for the formation of these copper deposits but the cu mineralization occurred mainly within a set of normal and thrust faults in the region the alteration types and faults in bondar hanza were distinguished using detailed local geology including distribution of known mineralization supported by remote sensing aster airborne geophysics and topography the relationship between mineralization and faults was examined using rose diagrams and fry analysis this investigation of bondar hanza deposit has revealed that the trend of faults and dykes as well as the distribution of copper analyses within drill cores is aligned with the main trend of mineralization the nw se trending faults in the urmia dokhtar magmatic arc are effective in localizing the emplacement of porphyry copper ore deposits and those that trend between n125 n145 are key to further exploration

platinum group minerals from the kambalda nickel deposits western australia the relative abundance compositional variability and geologic occurrence of platinum group minerals have been determined by a study of samples from a number of geologic environments in the kambalda nickel deposits these results have been integrated with findings from a previous study by hudson and donaldson 1984 of platinum group minerals in amalgamation residues from the gold recovery circuit of the kambalda nickel mill to give an overall picture of the nature and distribution of platinum group minerals at kambalda the major platinum minerals are sperrylite and moncheite and the major palladium minerals are sudburyite merenskyite stibiopalladinite palladoarsenide michenerite and testibiopalladite palladium also occurs in solid solution in palladian melonite irarsite is the only iridium mineral recognized and no discrete phases have been observed for the other platinum group elements sperrylite occurs within massive pyrrhotite pentlandite ores and is particularly abundant in ores that are rich in chalcopyrite a high proportion of the pt in the kambalda nickel deposits is believed to occur as sperrylite but not all sperrylite is sufficiently coarse in grain size to enable gravity concentration nevertheless sperrylite is the dominant platinum group mineral recovered in gravity concentrates discrete palladium minerals are most abundant in stringers of sulfide in the footwall to the ore in crosscutting sulfide veins or in reaction zones associated with hydrothermal veins and porphyries within the massive and matrix ores coarse discrete palladium minerals are rare and it is concluded that palladium occurs in solid solution or as finely dispersed submicroscopic grains in sulfide minerals predominantly pentlandite the occurrence within the ore zones of pt as sperrylite and pd dispersed in pentlandite is believed to reflect a primary magmatic distribution however the presence of sudburyite moncheite merenskyite michenerite testibiopalladite and palladian melonite in stringers and reaction zones indicates that their formation may be related to postmagmatic processes in particular metamorphic segregation of sulfides and the interaction of ore sulfides with younger hydrothermal fluids

implication of dating of early tertiary volcanic rocks from the north chilean precordillera abstract since the early jurassic subduction induced volcanic activity in the north chilean andes 21 23 5 s has migrated 200 300 km eastward from the present coast jurassic magmatic arc to the western cordillera miocene recent volcanic rocks due to the paucity of chronological data however the exact age and extent of various magmatic sub belts within this area are not well constrained in the precordillera a sequence of 1500 5000 m thick red bed sediments is partly intercalated with and mostly covered by predominantly intermediate calc alkaline tuffs and lavas presently the age of this sequence is considered to be upper jurassic and or cretaceous from this sequence eleven biotites and seven hornblendes were analyzed and yielded 40 ar 39 ar plateau ages of between 48 and 38 ma indicating upper eocene volcanic activity in the eastern part of the precordillera in contrast volcanic activity in the western part of the precordillera has been dated at 92 2 5 ma indicating an earlier onset of volcanism and therefore sedimentation of the red beds in the late eocene the intense volcanism ceased in this area contemporaneous with decreasing relative convergence rate of the nazca plate and the south american continent this final phase of eocene volcanism coincided with a period of important deformation the incaic phase biotites from two ash fall tuffs separated by a distinct angular unconformity yield identical ages of 38 50 0 90 ma and 38 45 0 60 ma these dates provide the best age estimate of the incaic phase in the north chilean precordillera

modulation of radar backscatter from the ocean by a variable surface current abstract calculations of surface wave and radar cross section modulation induced by a spatially varying surface current have been compared with field measurements made with sar x and l bands real aperture radar x band laser slope guage and ccd video camera during the joint canada u s ocean wave investigation project jowip which took place in august 1983 the comparison reveals that i many existing wind relaxation models underpredict the hydrodynamic effect of the current ii simple bragg scattering model underpredicts radar backscatter modulation for higher frequency radars e g x band but appears acceptable at lower radar frequencies e g l band iii the discrepancy between measurements and calculations at high radar frequency is reduced but not eliminated when the effects of long surface waves have been accounted for keywords include radar backscatter surface wave modulations wave current interactions georgia strait experiment and jowip

new geochronological results and structural evolution of the pataz gold mining district implications for the timing and origin of the batholith hosted veins abstract the paleozoic pataz parcoy gold mining area is located in a right stepping jog on the regional cordillera blanca fault in northern peru most of the 8 million ounces of gold production from this area has come from quartz carbonate sulfide veins hosted by the pataz batholith despite a subduction zone setting since at least the cambrian the area records several periods of extension and its present structure is that of a rift and graben terrain the pataz district the northern part of the pataz parcoy area is dominated structurally by northwest to north northwest striking nw nnw faults and northeast to east northeast striking ne ene lineaments both of which have been active periodically since at least the mississippian early carboniferous nw nnw faults control the margins of a central horst that exposes basement schist and the pataz batholith and step across ne ene lineaments the lavasen graben to the east of the central horst contains the lavasen volcanics and the chagual graben to the west contains an allochthonous sedimentary sequence derived from the western andean cordillera new shrimp zircon geochronological data indicate emplacement of the pataz batholith during the middle mississippian at around 338 336 ma approximately 10 ma earlier than previous estimates based on 40 ar 39 ar geochronology the calc alkaline i type batholith comprises diorite and granodiorite the latter being the major component of the batholith and was emplaced as a sill complex within the moderately ne dipping sequence of the eastern andean cordillera moderate to high temperature ductile deformation took place on the batholith contacts during or shortly after emplacement following emplacement of the batholith differential uplift occurred along nw nnw faults forming the lavasen graben into which the lavasen volcanics were deposited shrimp u pb in zircon ages for the lavasen volcanics and the esperanza subvolcanic complex which was intruded into the western margin of the graben are within error of one another at ca 334 ma the ductile batholith contacts were cut by renewed movement on nw nnw faults such that the margins of the batholith are now controlled by these steep brittle ductile faults the nw nnw faults were oriented normal to the principal axis of regional shortening ene wsw during formation of the batholith hosted gold bearing quartz carbonate sulfide veins the misoriented faults were unable to accommodate significant displacement leading to high fluid pressures vertical extension in the competent batholith and formation of gold bearing veins brittle failure of the batholith was most extensive in the northern pataz district where the fault controlled western contact of the batholith is offset by a swarm of ne ene lineaments the timing of vein formation is not established despite published 40 ar 39 ar ages of 312 to 314 ma for metasomatic white mica which are interpreted as minimum ages of formation gold bearing veins formed during or shortly after uplift of the pataz batholith and formation of the lavasen graben they were therefore broadly coeval with deposition of the lavasen volcanics and emplacement of the esperanza subvolcanic complex these k rich weakly alkalic ferroan a type magmas may provide a viable source for the ore fluid that deposited gold in the pataz batholith

uplift of the central andean plateau and bending of the bolivian orocline the topography of the central andes can be considered the primary tectonic signal of late cenozoic mountain building in an arid region where the effects of uplift and magmatism are little obscured by denudation the spatial coverage of the topographic signal is more complete than that for sparsely sampled geological and geophysical data a color coded image of digitized topography between 12 s and 37 s highlights the altiplano puna one of the world s most remarkable plateaus and reveals important physiographic clues about the formation of that major feature the topographic data combined with information on structure magmatism seismicity and paleomagnetism support a simple kinematical model for the late cenozoic evolution of the central andes the model does not require collisional effects or enormous volumes of intrusive additions to the crust but instead calls upon plausible amounts of crustal shortening and lithospheric thinning the model interrelates andean uplift a changing geometry of the subducted nazca plate and a changing outline in map view of the leading edge of the south american plate crustal shortening has accommodated convergence between the chilean peruvian forearc and the south american foreland the altiplano puna plateau can be constructed by a combination of crustal shortening and thickening and lithospheric thinning above a shallow dipping 20 30 subducted plate the seawardly concave bend of western south america the bolivian orocline was enhanced but not completely produced by an along strike variation in the amount of late cenozoic shortening maximum shortening in bolivia both produced the widest part of the plateau and increased the seaward concavity of the bolivian orocline the along strike variations of shortening are hypothesized to result from corresponding along strike variations in the width of a weakened zone in the overriding plate weakening occurs above the wedge of asthenosphere located between the subducted and overriding plates hence the width of the zone of weakening depends upon the dip of the subducted plate two types of shortening are recognized 1 a widespread basin and range laramide like shortening that characterizes modem activity in the sierras pampeanas and late miocene deformation of the altiplano puna and 2 on the eastern side of the cordilleras and plateau an east verging foreland fold thrust belt in which the underthrust foreland compresses and thickens the ductile lower crust and produces a plateau uplift of the upper crust the second type of shortening can be applied to plio quaternary deformations throughout the central andes but with a substantial narrowing of the region of plateau uplift in peru and south of 28 s a proposed monoclinal flexure of the upper crust on the western side of the plateau uplift explains the remarkably simple and regular morphology of the main western slope of the central andes the monocline is located above the tip of the asthenospheric wedge between the converging plates it is postulated to occur above the western limit of lower crustal thickening in the regions of horizontal subduction the monocline can be associated with a late miocene asthenospheric wedge tip

the physical volcanology of archaean komatiite sequences from forrestania southern cross province western australia abstract the archaean supracrustal sequence at forrestania contains at least five komatiitic belts which can be traced along strike for distances in excess of 30 km lithologies range from olivine cumulates which crystallised at the interface between substrate and flowing lava to spinifex textured rocks which underwent rapid crystallisation within ponded lava lobes characteristic associations of different rock types are interpreted in terms of variations in eruption rate which presumably reflect proximity to the vent or to a major lava river thick sequences of olivine adcumulate to mesocumulate crystallised in a dynamic environment where lava flow was continuous and eruptive velocities were high sheeted bodies of olivine cumulate formed from voluminous turbulent flow of lava over relatively refractory substrates such as basalt and oxide facies banded iron formation ribbon shaped olivine cumulate bodies formed in an equally dynamic environment within major lava channels where the substrate was less refractory and consisted of quartz rich sedimentary rocks which were susceptible to thermal erosion distributary lava channels in more distal settings are represented by thinner ribbon like accumulations of olivine mesocumulate to orthocumulate unusual poikilitic pyroxene bearing rocks are present at the base of some lava channels and appear to represent the crystallisation product of a komatiitic lava which has been contaminated by cherty sedimentary rocks pyroxene and plagioclase bearing cumulates are present at the top of other channel sequences and reflect late stage ponding and in situ differentiation of komatiitic lava within the channel the channel facies rocks are flanked by sequences comprising multiple thin spinifex textured flow units which formed from the episodic overflow of lava from the distributary channels similar rocks also occur stratigraphically above many of the thick olivine cumulate bodies and reflect episodic emplacement of thin cooling units during the waning stages of the eruptive cycle

a theory of the ka band radar imaging mechanism of a submerged wreck and associated bed forms in the southern north sea the ka band radar imaging mechanism of the submerged wreck sand ribbon of the motor vessel m v birkenfels in the southern north sea is investigated by applying the quasi specular scattering theory and considering the capillary as well as the gravity wave ranges of the wave energy density spectrum for the imaging of wrecks and other oceanographic and meteorological phenomena at the sea surface it is assumed that quasi specular scattering becomes dominant at higher radar frequencies like ka and x band and wind speeds 7 8 m s 1 multibeam echo sounder images of the birkenfels wreck and associated sand ribbons as well as other available environmental in situ data have been analyzed the formation of sand ribbons at the sea bed and the manifestation of its radar signatures at the water surface are caused by an elliptical vortex or helical flow cell triggered by unidirectional tidal current flow interacting with the wreck the difference between simulated and measured normalized radar cross section nrcs modulation as a function of the space variable is less than 31 6 results are presented for nrcs simulations dependent on position for different effective incidence angles unidirectional current speeds wind speeds and relaxation rates the calculated current gradient or strain rate of the imaging theory has the same order of magnitude as those obtained for marine sand waves this implies that the responsible hydrodynamic interaction mechanism is able to produce radar signatures of submerged wrecks sand ribbons and make them visible at the sea surface

how do metals escape from magmas to form porphyry type ore deposits abstract many precious and base metals cu au ag mo w sn in porphyry type deposits are extracted from a granitic to granodioritic silicate melt and transported by magmatic hydrothermal fluids to the site of ore deposition metals abundance increases from some ppb in the melt to in ore bodies assuming a unique magmatic source for metals it implies an exceptional combination of enrichment process acting over up to 4 orders of magnitude previous models of magma differentiation and hydrothermal circulations omitted to consider the role of metal segregation during magma chamber evolution models for the formation and evolution of intrusions have recently shifted from the so called melting storage assimilation homogenization mash paradigm basically steady state to the mantle melting segregation ascent emplacement m m sae paradigm dynamic and discontinuous in time successive magma injections of variable compositions progressively build the magma chamber this is supported by field relations e g cross cutting dykes and stocks textures e g partially resorbed enclaves or mineral fabrics geochemistry e g hybridization signatures and age dating aswell as istopic studies as melt crystallizes and forms a mush 50 crystals volatiles also exsolve forming a magmatic volatile phase mvp while melt motion slows down metals partition between the three phases melt crystals and mvp they generally prefer the mvp owing to more favorable partition coefficients this is indicated by metal content in coeval melt and fluid inclusions with homogenization temperatures above 600 c or in volcanic fumaroles here by simulating the physical interactions between the three phases we suggest a model of fluid sparging during which metals segregate towards the mvp by diffusion and are further transported by advection as metal complexes the model also provides estimates of metal enrichment an undimensional peclet number rules the competition between diffusion and advection basically scaling with respect to the inverse of the product of melt viscosity by metal diffusivity d the threshold value of the peclet number between diffusion and advection is roughly 10 9 fast diffusive metals au cu ag w readily diffuse from silicate melt and towards bubbles of the mvp to escape the mush through tubular structures the mvp must overcome a critical gas saturation level about 20 vol usually reached after several magma injections advection then takes over and transports the metal enriched mvp towards the top of the magma chamber this leads to nearly coeval 1 separation between a high salinity liquid phase and a low salinity vapor phase 2 fluid rock interactions resulting in potassic advanced argillic and phyllic alterations and 3 metal deposition the metal enrichment scales as the ratio between partition coefficient i e related to the gradient in chemical potential diffusivity i e related to the gradient of concentration and melt viscosity i e related to the gradient of momentum the rates at which all such gradients relax determe metals enrichment inducing chemical and physical instabilities leading to a cyclic process the whole cycle also encompasses the case of a partial non completed full enrichment yielding to barren intrusions a tentative model generalizes the sparging fluid model to other metal deposits linked to an intrusion such generalization should be interpreted as predicting metal enrichment by 3 4 orders of magnitude rather than predicting an exact value

variability of outcrop magnetic susceptibility and its relationship to the porphyry cu centers in the highland valley copper district abstract the highland valley copper porphyry cu mo centers compose canada s largest porphyry cu mining district and are hosted in plutonic rocks of the late triassic guichon creek batholith in the quesnel terrane british columbia here we evaluate the relationship between variations in magnetic susceptibility and alteration in order to define a footprint around the porphyry cu centers using a district scale dataset of 1610 minimally weathered outcrops and 11 432 magnetic susceptibility measurements statistical analysis of the outcrop based measurements revealed changes in outcrop geometric mean magnetic susceptibility and the coefficient of variation extent of variability in relation to the mean are proportional to vein frequency and altered rock volume estimates at a confidence interval of 95 and 9 degrees of freedom the average standard error uncertainty of the geometric mean and coefficient of variation from 10 magnetic susceptibility outcrop measurements is 7 3 and 13 2 respectively modeling of outcrop magnetic susceptibility data shows that domains of coefficient of variation of 0 3 extend 1 4 km away from the porphyry centers whereas pronounced susceptibility lows of

sulfide silicate textures in magmatic ni cu pge sulfide ore deposits massive semi massive and sulfide matrix breccia ores abstract much of the value of magmatic ni cu pge sulfide orebodies is contained within massive or semi massive ores that show a wide variety of textural relationships to included or adjacent silicate rocks we identify five mutually gradational textural types 1 pure inclusion free massive sulfide ores 2 sulfide matrix ore breccias of sharp wall soft wall or mixed character 3 emulsion textured ores formed by frozen mixtures of molten silicate and sulfide most commonly developed as melt films at thermal erosion contacts 4 vein hosted sulfides formed at late magmatic or high temperature post emplacement deformation stage close to the brittle ductile transition in the country rocks or host igneous bodies and 5 tectonic durchbewegung breccias formed by mechanical inter shearing of less ductile silicate inclusions and more ductile solid sulfides some deposits the moran shoot at kambalda being the type example record the invasion of country rock footwall by downward or sideways percolating superheated molten sulfide liquid generating vertical sequences of pure massive sulfide emulsion textured ores and finely spaced invasive sulfide veins these are referred to as sulfide melting infiltration fronts and may provide a clue to the mechanism of formation of sulfide rich magmatic ores as whole sulfide matrix ore breccias are particularly well developed in the voisey s bay and aguablanca deposits where they developed by flooding of percolating sulfide melt through the silicate matrix of magmatic intrusion breccias displacing silicate melt the lithology of the silicate or carbonate rock inclusions determines the nature of the inclusion matrix relationships non refractory inclusions typically disaggregate along original grain boundaries to leave coherent inclusions surrounded by clouds of inclusion derived or matrix derived crystals with the low melting silicate component preferentially displaced by sulfide liquid whereas refractory inclusions retain sharp boundaries zonation of inclusions and overgrowths preserves reaction between inclusion and silicate matrix that pre dates invasion of the intrusion breccia by sulfide liquid the process of percolation of dense low viscosity sulfide liquid into pore space and fractures within partially molten or melting silicate rock is a unifying theme that links sulfide matrix ore breccias and emulsion textured ores with distinctive textures in less sulfide rich rocks such as net texture matrix ore texture leopard texture poikilitic net texture and interspinifex ore vein hosted massive sulfides may be emplaced under magmatic conditions where the excess pressure of the sulfide liquid column drives or enhances fracturing of the country rock and injection of sulfide into the cracks such veins are commonly referred to as remobilised a term which may obscure process understanding and should be reserved for cases where tectonic solid state mobilisation of sulfide can be demonstrated on textural and structural grounds the tendency of sulfide liquids to invade country rocks and potentially to drive the propagation of their own magmatic containers may be a critical feedback loop in the development of magmatic sulfide mineral systems

mapping submarine sand waves with multiband imaging radar 1 model development and sensitivity analysis in 1989 and 1991 unexpected modulations caused by submarine sand waves were observed with the airborne imaging radar air a p l and c band synthetic aperture radar the measurements were performed in a sand wave area off the dutch coast the sand waves have an asymmetric sawtooth shaped profile with the steep slope oriented toward the northeast during the experiments wind and current had opposite directions the wind was directed toward the northeast and the current toward the southwest under these conditions existing models for the imaging mechanism predict that the modulation depth decreases with increasing radar frequency and that the steep slopes show up as dark lines in radar images the air images show a relation between modulation depth and radar frequency as predicted however only the p band image of 1989 shows the steep slopes of the sand waves as dark lines the p band image of 1991 and the l band images of 1989 and 1991 show a sawtooth shaped modulation which cannot be explained by existing theory a new model is developed that is one dimensional in position space and fully two dimensional in wavenumber space the radar cross section is calculated using both first order bragg and an integral equation scattering model in which the cross section originates from a spectral band rather than a single value the new model contains two improvements over previous ones first wave blocking or better wave reflection is included though in an approximate manner it is shown to be of importance at p band only second the contribution to the radar cross section from waves moving both to and from the radar is included whereas some previous models consider only one of these contributions this explains the observed modulations at least qualitatively under the assumptions that the angular distribution of short waves is almost constant and that waves moving against the wind have small relaxation rates

pt and pd mobility in hydrothermal fluids evidence from komatiites and from thermodynamic modelling abstract komatiite host rocks and ores provide a natural laboratory for the study of pt and pd during hydration and carbonation of ultramafic rocks the degree of correlation between pt and pd and of those elements with lithophile elements such as ti in komatiitic rocks and ores is strongly dependent on the magmatic sulfide content of the rock pt and pd are typically very strongly correlated within s poor komatiites and in disseminated ores containing 5 volume or less magmatic sulfides in contrast they are almost completely decoupled in sulfide rich ore samples thermodynamic modelling based on the existing body of published experimental data on pt and pd solubilities suggests that pd and pt can be readily transported as bisulfide complexes in acidic neutral solutions under reduced and moderate oxidation condition at 300 c and chloride complexes are only important under extremely acidic oxidised conditions pd is much more soluble than pt in the case of fluids in sulfide rich environments in equilibrium with the characteristic assemblages found within altered and metamorphosed komatiites solubilities of both elements are much lower in sulfide poor environments especially where ph values are constrained to neutral values by the near ubiquitous presence of carbonate minerals in the alteration assemblage this accounts for the evident near immobility of pt and pd in even the most altered silicate host rocks as compared with their wide dispersion in sulfide rich ores

deformation and remobilization in some western australian nickel ores abstract volcanic associated nickel deposits in the archaean greenstone belts of western australia show a variety of features related to post depositional deformation and medium to high grade regional metamorphism deformation and accompanying remobilization have resulted in changes to the gross structure shape and orientation of ore shoots and have led to the development of separate offset ores tectonic breccia ores and irregular sulphide stringers physical remobilization of ore has been mainly on a mesoscopic scale up to 150 m and largely by mechanical processes but with some fluid assisted and stress induced chemical remobilization of sulphur and possibly copper most of the present ore fabrics and textures are the result of combined deformation metamorphically induced phase changes and recrystallization massive and matrix ores show well developed tectonite fabrics defined by mineralogical layering preferred orientation of pyrrhotite and alignment of silicate and spinel inclusions layering in the ores is probably the result of both strain controlled exsolution from high temperature phases and mechanical segregation of different minerals within polyminerallic aggregates during deformation observational and experimental data suggest that sulphide deformation was dominantly by dislocation type mechanisms kinking and twinning at medium temperatures 300 550 c with diffusional mechanisms becoming important at high temperature 500 c dynamic recrystallization during deformation probably accounts for the annealed state of individual mineral grains within most ores except those deformed at a late stage

primary cumulus platinum minerals in the monts de cristal complex gabon magmatic microenvironments inferred from high definition x ray fluorescence microscopy an unusual occurrence of pt enriched pyroxenites in the monts de cristal igneous complex is characterized by unusually high ratios of pt to other platinum group elements pges and very low cu and sulfide contents synchrotron x ray fluorescence microscopy was used to identify over a hundred discrete grains of platinum minerals and relate their occurrence to textural associations in the host heteradcumulate orthopyroxenites element associations backed up by fib sem and pixe probe observations indicate that most of the pt is associated with either as or trace cu ni rich sulfides or both some of the pt as grains can be identified as sperrylite and most are likely to be pt fe alloy the relative abundances and volumes of pt minerals to sulfide minerals are very large compared with typical magmatic sulfides almost all of the grains observed lie at or within a few tens of m of cumulus orthopyroxene grain boundaries and there is no significant difference between the populations of grains located inside or outside plagioclase oikocrysts these oikocrysts are inferred to have crystallized either at the cumulus stage or very shortly thereafter on the basis of their relationship to ti enrichment in the margins of pyroxene grains not enclosed in oikocrysts this relationship precludes a significant role of trapped intercumulus liquid in pt deposition or mobilization and also allows a confident inference that pt rich and pt as enriched phases precipitated directly from the magma at the cumulus stage these observations lead to the conclusion that fractionation of pt from other pges in this magmatic system is a consequence of a solubility limit for solid pt metal and or pt arsenide

timing and formation of porphyry cu mo mineralization in the chuquicamata district northern chile new constraints from the toki cluster the recently discovered toki cluster which includes the toki quetena genoveva miranda and opache porphyry cu mo prospects is located 15 km south southwest of the chuquicamata radomiro tomic mines in northern chile these prospects occur in an area of 5 6 km and are completely covered with neogene alluvial deposits inferred resources for the cluster are estimated at about 20 mt of fine copper with toki and quetena contributing 88 of these resources mineralization in these deposits is associated with tonalite porphyries that intruded andesites and dacites of the collahuasi group and intrusions of the fortuna los picos granodioritic complex hypogene mineralization in the toki cluster consists mainly of chalcopyrite bornite with minor molybdenite with mineralization grading outward to a chalcopyrite pyrite zone and ultimately to a pyrite halo alteration is dominantly of the potassic type with k feldspar and hydrothermal biotite sericitic alteration is relatively restricted to late quartz pyrite veins d type veins previous k ar geochronology for the cluster yielded ages within a range of 34 to 40 ma four new re os ages for toki indicate that molybdenite mineralization occurred in a single pulse at 38 ma re os ages for three different molybdenite samples from quetena are within error of the toki mineralization ages these ages are concordant with a new zircon u pb age of 38 6 0 7 ma from the tonalite porphyry in quetena two re os ages for genoveva 38 1 0 2 and 38 0 0 2 ma are also within error of the toki and quetena molybdenite ages four re os molybdenite ages for opache range between 36 4 and 37 6 ma the miranda prospect is the youngest with an age of 36 ma four new re os ages for the chuquicamata deposit range between 33 and 32 ma whereas nine new 40ar 39ar ages of biotite muscovite and k feldspar range between 32 and 31 ma analyzed molybdenites have re and os concentrations that vary between 21 3 099 ppm and 8 1 231 ppb respectively the highest re and os concentrations are found in the toki prospect three new 40ar 39ar ages for the toki cluster are younger than the re os mineralization ages the age spectra for these three samples show evidence of excess argon and have similar inverse isochron ages of 35 ma that probably reflect a late hydrothermal phyllic event the new geochronological data presented here for the toki cluster indicate that molybdenite mineralization occurred within a very short period probably within 2 ma and synchronously at 38 ma in three mineralization centers toki quetena and genoveva furthermore mineralization at the toki cluster preceded the emplacement of the chuquicamata deposit 35 31 ma and indicates that porphyry cu mo mineralization occurred episodically over a period of several million years in the chuquicamata district

the precordilleran fault system of chuquicamata northern chile evidence for reversals along arc parallel strike slip faults abstract the chilean precordillera situated between the longitudinal valley and the western cordillera of northern chile was the site of the andean magmatic arc from the late cretaceous to the eocene oligocene boundary magmatism came to an end during the incaic tectonic phase 38 ma which caused arc normal shortening and the development of longitudinal dextral strike slip faults precordilleran fault system this magmatic arc tectonism is also related to the formation of the chuqicamata porphyry copper ore deposit as well as of other important deposits of this type in the precordillera structural investigations in and around the chuqicamata open pit mine have shown that wrench tectonics determined the kinematics of the area the n s striking west fissure which separates a 35 ma old non mineralised pluton to the west from a central late paleozoic basement ridge containing the mineralization became a sinistral fault along with other parallel faults in the area the central part is separated from similar paleozoic rocks to the east by the messabi este fault and a narrow faulted and sheared syncline of mesozoic cenozoic sediments this fault bears structures indicating dextral movements which probably are of an age that is similar to the mylonites 34 8 ma in the western pluton the dextral movements preceded the sinistral shear thus the fault system of chuqicamata displays a reversal of arc parallel shear movements according to the orientation of quartz veins in the mineralized body it is presumed that the sense of displacement of these strike slip motions reversed when mineralization started at about 32 ma during this time the stress field must have changed fundamentally the incaic phase dextral transpression is supposed to have been induced by the oblique vector of plate motion the following sinistral transtension corresponds to a time of reduced convergence rate and possibly reduced plate coupling as however the vector of plate motion remained unchanged during that time oblique subduction cannot be used as an argument for arc parallel sinistral shear movements

the distribution of pge and the role of arsenic as a collector of pge in the spotted quoll nickel ore deposit in the forrestania greenstone belt western australia the spotted quoll pge bearing ni deposit in the forrestania greenstone belt in the archean yilgarn block in western australia is a komatiite associated massive sulfide orebody tectonically displaced from its original host the brecciated ore contains clasts of quartz and garnet schist and is located along a shear zone overlain by banded iron formation bif and underlain by bif and quartz biotite metasediments the deformation of the ore has destroyed its magmatic textures and it has been sheared and recrystallized at amphibolite facies then the deformed ore has been subjected to a hydrothermal event that concentrated the pge with au and as often at the edge of the ni ore the pge are distributed between pgm and in solid solution in ni sulfarsenides and pd also occurs in pentlandite the pgm include sudburyite pdsb sperrylite ptas2 and irarsite irass all six pge and minor au are hosted in gersdorffite niass two generations of gersdorffite have been recognized a higher temperature magmatic euhedral co rich gersdorffite encloses ir pt and rh bearing pgm surrounded by halos of rh ir and os rich gersdorffite a lower temperature ni rich gersdorffite forms anhedral grains and rims on grains of nickeline nias in this low temperature gersdorffite pge are concentrated toward the mineral edges sudburyite and gold occur associated predominantly with nickeline the pge and gold are now predominantly associated with sulfarsenides that are the controlling factor for their distribution

structure of the surface wind field from the seasat sar an intensive analysis of the vector wind field of one seasat data set pass 1339 is described wind speed and direction signatures are found in seasat sar synthetic aperture radar images and the resulting estimates are compared with the seasat a scatterometer system sass and simultaneous noaa p 3 aircraft measurements a power law is presented to relate sar measured backscatter to sass estimated wind speed and the sar estimates are shown to agree with the sass estimates to within a standard error of 0 7 m s over a range of wind speeds from 3 m s to 13 m s the surface expressions of atmospheric roll vortices are apparent in several of the sar images and may be responsible for the wind direction signature in these cases wind field estimates averaged over regions of variable sizes are possible because of the high resolution of sar imagery a method for extracting low wave number directionality and its variability from sar spectra is described and sar direction estimates obtained from spectra of 6 4 km square images are shown to have a precision of approximately 10 although a comparison data set that could validate these higher resolution estimates is lacking averages over 40 km square regions are in good agreement with the other wind field information the sar wind direction estimates yield a more complete interpretation in a region with a turning wind field near a front that is ambiguous with only sass observations in this region the flow patterns of the high resolution estimates appear consistent with our knowledge of the overall circulation considering all the observations however in another region the small scale variability is too large and random to represent real wind variability although averages derived from these estimates are still reliable

the observation of ocean surface phenomena using imagery from the seasat synthetic aperture radar an assessment over the period july 4 to october 10 1978 the seasat synthetic aperture radar sar gathered 23 cm wavelength radar images of some 108 km2 of the earth s surface mainly of ocean areas at 25 40 m resolution our assessment is in terms of oceanographic and ocean monitoring objectives and is directed toward discovering the proper role of sar imagery in these areas of interest in general sar appears to have two major and somewhat overlapping roles first quantitative measurement of ocean phenomena like long gravity waves and wind fields as well as measurement of ships second exploratory observations of large scale ocean phenomena such as the gulf stream and its eddies internal waves and ocean fronts these roles are greatly enhanced by the ability of 23 cm sar to operate day or night and through clouds to begin we review some basics of synthetic aperture radar and its implementation on the seasat spacecraft seasat sar imagery of the ocean is fundamentally a map of the radar scattering characteristics of 30 cm wavelength ocean waves distorted in some cases by ocean surface motion we discuss how wind stress surface currents long gravity waves and surface films modulate the scattering properties of these resonant waves with particular emphasis on the mechanisms that could produce images of long gravity waves doppler effects by ocean motion are also briefly described measurements of long wavelength 100 m gravity waves using seasat sar imagery are compared with surface measurements during several experiments combining these results we find that dominant wavelength and direction are measured by seasat sar within 12 and 15 respectively however we note that ocean waves are not always visible in sar images and discuss detection criteria in terms of wave height length and direction sar estimates of omnidirectional wave height spectra made by assuming that sar image intensity is proportional to surface height fluctuations are more similar to corresponding surface measurements of wave height spectra than to wave slope spectra because seasat sar images show the radar cross section of 30 cm waves neglecting doppler effects and because these waves are raised by wind stress on the ocean surface wind measurements are possible comparison between wind speeds estimated from seasat sar imagery and from the seasat satellite scatterometer sass agreed to within 0 7 m s over a 350 km comparison track and for wind speeds from 2 to 15 m s the great potential of sar wind measurements lies in studying the spatial structure of the wind field over a range of spatial scales of from 1 km to 100 km at present the spatial and temporal structure of ocean wind fields is largely unknown because sar responds to short waves whose energy density is a function of wind stress at the surface rather than wind speed at some distance above the surface variations in image intensity may also reflect changes in air sea temperature difference thus complicating wind measurements by sar because sar images show the effects of surface current shear air sea temperature difference and surface films through their modulation of the 30 cm waves seasat images can be used to locate and study the gulf stream and related warm water rings tidal flows at inlets internal waves and slicks resulting from surface films in many of these applications sar provides a remote sensing capability that is complementary to infrared imagery because the two techniques sense largely different properties namely surface roughness and temperature both stationary ships and moving ships with their attendant wakes are often seen in sar images ship images can be used to estimate ship size heading and speed however ships known to be in areas imaged by sar are not always detectable clearly a variety of factors such as image resolution ship size sea state and winds could affect ship detection overall the role of sar imagery in oceanography is definitely evolving at this time but its ultimate role is unclear we have assessed the ability of seasat sar to measure a variety of ocean phenomena and have commented briefly on applications in the end oceanographers and others will have to judge from these capabilities the proper place for sar in oceanography and remote sensing of the ocean

joint canada u s ocean wave investigation project an overview of the georgia strait experiment an overview of the georgia strait experiment joint canada u s ocean wave investigation project or jowip 1983 is presented containing a list of participants objectives procedures and main results jowip was designed to provide quantitative comparisons between surface measurements and remote sar imagery of internal waves and narrow v surface ship wakes first order bragg modeling gives factor of 3 accuracy for l band internal wave modulation the composite model and possibly nonlinear surface wave internal wave interaction theory are required at x band narrow v wakes were imaged in dabob bay washington under low wind conditions at l band surface slopes in the kelvin wakes are not large enough to produce specular reflections even at a radar incidence angle of 23 modulations along the v arms are strongly evident and have the same wavelength as the transverse kelvin wake component these results and others are described in detail in other papers in this same issue

comparisons between measured and theoretical results for c and ku bands backscatter from naturally occurring internal wave current patterns predicted and measured values of radar backscatter and of internal wave surface currents are compared using data obtained during the scattmod internal wave experiment radar backscatter and surface truth measurements were obtained during six days in august 1985 and cover nine sets of tide generated internal waves in the georgia strait canada the radar portion of this data consists of approximately 75 sets each of c and ku band fanbeam airborne scatterometer signals each processed to 25 incidence angles and an along track resolution of either 12 5 or 6 25 m aircraft navigation data were also recorded simultaneous surface measurements including wave slope wave height current wind and ship position were obtained from the cfav endeavour current meter were located both fore and aft to allow internal wave phase velocity estimates to be computed

platinum group minerals from the jinbaoshan pd pt deposit sw china evidence for magmatic origin and hydrothermal alteration the jinbaoshan pt pd deposit in yunnan sw china is hosted in a wehrlite body which is a member of the permian 260 ma emeishan large igneous province elip the deposit is reported to contain one million tonnes of pt pd ore grading 0 21 ni and 0 16 cu with 3 0 g t pd pt platinum group minerals pgm mostly are 10 m in diameter and are commonly te sn and as bearing including moncheite ptte2 atokite pd3sn kotulskite pdte sperrylite ptas2 irarsite irass cooperite pts sudburyite pdsb and pt fe alloy primary rock forming minerals are olivine and clinopyroxene with clinopyroxene forming anhedral poikilitic crystals surrounding olivine primary chromite occurs either as euhedral grains enclosed within olivine or as an interstitial phase to the olivine however the intrusion has undergone extensive hydrothermal alteration most olivine grains have been altered to serpentine and interstitial clinopyroxene is often altered to actinolite tremolite and locally biotite interstitial chromite grains are either partially or totally replaced by secondary magnetite base metal sulfides bms such as pentlandite and chalcopyrite are usually interstitial to the altered olivine pgm are located with the bms and are therefore also interstitial to the serpentinized olivine grains occurring within altered interstitial clinopyroxene and chromite or along the edges of these minerals which predominantly altered to actinolite tremolite serpentine and magnetite hydrothermal fluids were responsible for the release of the platinum group elements pge from the bms to precipitate the pgm at low temperature during pervasive alteration a sequence of alteration of the pgm has been recognized initially moncheite and atokite have been corroded and recrystallized during the formation of actinolite tremolite and then cooperite and moncheite were altered to pt fe alloy where they are in contact with serpentine sudburyite occurs in veins indicating late pd mobility however textural evidence shows that the pgm are still in close proximity to the bms they occur in pge rich layers located at specific igneous horizons in the intrusion suggesting that pge were originally magmatic concentrations that within a pge rich horizon crystallized with bms late in the olivine clinopyroxene crystallization sequence and have not been significantly transported during serpentinization and alteration

platinum group minerals in the o toole ni cu co deposit brazil the o toole deposit is a cu ni co sulfide lens hosted by ultrabasic rocks the orebody has undergone postdeformational metamorphism and shearing the main sulfides of the o toole deposit are pyrrhotite po pentlandite pn and chalcopyrite cp in average proportions of 65po 30pn 5cp cobaltite gersdorffite and sphalerite are the most frequent accessories minerals assay data indicated the presence of platinum group elements pge platinum group minerals pgm were identified during microscopy on ore from the o toole deposit mineral identifications were made and confirmed by electron microprobe kotulskite melonite followed by irarsite and sperrylite are the most abundant pgm other identified phases include osas 2 osass osrhass ruteas osruas osas 5 and a complex os re as te fe y rh mineral platinum group minerals occur frequently as inclusions in cobaltite gersdorffite suggesting that the pgm formed first since pyrrhotite replaces cobaltite gersdorffite indicating its later crystallization it can be deduced that the pgm formed during the first stages of magma crystallization before sulfides and arsenides routine microprobe analysis identified a rhenium sulfide res 2 the second reported global occurrence

mineral potential mapping in an accreted island arc setting using aeromagnetic data an example from southwest alaska the distribution of volcanogenic massive sulfide vms porphyry epithermal alaska type ultramafic mafic complexes intrusion related au and granitoid sn w ore deposits in southwest alaska supports current metallogenic models linking the formation of these deposit types to the emplacement of different suites of igneous rocks during the evolution of this convergent plate margin regional scale aeromagnetic data provide a continuous set of observations over the deposits and show contrasting patterns over the igneous rock suites hosting the various deposit types combined with surface geologic data and regional metallogenic constraints aeromagnetic data filtered to enhance the anomalous magnetic field and map magnetic domains were used to produce a mineral potential map across this accreted island arc setting the reduced to pole upward continuation and total horizontal gradient transform maps show anomalies that could represent porphyry epithermal deposits within the intraoceanic and continental arc terranes the tilt derivative transform highlights lineaments within the back arc that may represent zones with potential for vms deposits the truncations of tilt derivative lineaments outline a major magnetic domain boundary between the back arc and craton margin which is prospective for granitoid sn w deposits annular tilt derivative highs outline granitoids that could be associated with intrusion related au deposits within the craton margin shallow magnetite rich alaska type ultramafic mafic complexes are mapped by their short wavelength high amplitude anomalies successful mineral potential mapping across southwestern alaska as performed in the present study suggests that filtered aeromagnetic data can be effectively used in mineral exploration in convergent continental margin settings

textural relationship of sulfide ores pge and sr nd os isotope compositions of the triassic piaohechuan ni cu sulfide deposit in ne china the 216 ma piaohechuan no 4 intrusion in northeastern china situated in the easternmost part of the central asian orogenic belt is composed of hornblende olivine gabbro overlain by hornblende gabbro the intrusion is about 630 m long 40 to 250 m wide and 50 to 150 m thick nickel sulfide mineralization is restricted to the lower part of the intrusion and contains 10 000 metric tons t of ni with average pge concentrations of 40 ppb os 30 ppb ir 36 ppb ru 26 ppb rh 255 ppb pt and 161 ppb pd in 100 sulfide

geochemistry of komatiites from forrestania southern cross province western australia evidence for crustal contamination the 2 9 ga old forrestania greenstone belt is intermediate in character between typical 3 0 ga and 2 7 ga belts in containing both al depleted and al undepleted komatiites the extensive nickel exploration database on the belt provides a unique opportunity to examine geochemical variations in the context of volcanological evolution within each of the six komatiitic units in the greenstone belt there is a transition from komatiites 18 28 wt mgo in the liquid to high and low magnesium komatiitic basalts 5 18 wt mgo with stratigraphic height and much of the chemical variance within the komatiitic suite can be explained in terms of the addition or fractionation of olivine there are however aspects of the incompatible element signatures which must be attributed to other factors the more primitive komatiites from the lower ultramafic units are al depleted al2o3 tio2 10 5 13 0 and depleted in both light and heavy ree lasmn 0 5 gdybn 1 5 komatiites from the uppermost ultramafic units are variably less depleted in al al2o3tio2 16 5 20 5 this is interpreted to reflect decreasing retention of garnet in the source region of the forrestania komatiites over time and possibly a decrease in the depth of melting within the al depleted suite there are also anomalous enrichments in sio2 feo tio2 and zr which correlate with regional variations in the composition of substrate metasedimentary rocks banded iron formation versus felsic tuff coupled with field evidence for trough structures at the base of lava channel sequences these chemical anomalies provide strong evidence for supracrustal thermal erosion by komatiite lavas the forrestania data indicate that 2 9 ga old komatiites were generated over a range of melting conditions spanning those typical of older and younger archaean sequences and that contamination by supracrustal thermal erosion can influence komatiite chemistry on a regional scale

geological analysis of aeromagnetic data from southwestern alaska implications for exploration in the area of the pebble porphyry cu au mo deposit aeromagnetic data are used to better understand the geology and mineral resources near the late cretaceous pebble porphyry cu au mo deposit in southwestern alaska the reduced to pole rtp transformation of regional scale aeromagnetic data shows that the pebble deposit is within a cluster of magnetic anomaly highs similar to pebble the iliamna kijik and neacola porphyry copper occurrences are in magnetic highs that trend northeast along the crustal scale lake clark fault a high amplitude short to moderate wavelength anomaly is centered over the kemuk occurrence an alaska type ultramafic complex similar anomalies are found west and north of kemuk a moderate amplitude moderate wavelength magnetic low surrounded by a moderate amplitude short wavelength magnetic high is associated with the gold bearing shotgun intrusive complex the rtp transformation of the district scale aeromagnetic data acquired over pebble permits differentiation of a variety of jurassic to tertiary magmatic rock suites jurassic cretaceous basalt and gabbro units and late cretaceous biotite pyroxenite and granodiorite rocks produce magnetic highs tertiary basalt units also produce magnetic highs but appear to be volumetrically minor eocene monzonite units have associated magnetic lows the rtp data do not suggest a magnetite rich hydrothermal system at the pebble deposit the 10 km upward continuation transformation of the regional scale data shows a linear northeast trend of magnetic anomaly highs these anomalies are spatially correlated with late cretaceous igneous rocks and in the pebble district are centered over the granodiorite rocks genetically related to porphyry copper systems the spacing of these anomalies is similar to patterns shown by the numerous porphyry copper deposits in northern chile these anomalies are interpreted to reflect a late cretaceous magmatic arc that is favorable for additional discoveries of late cretaceous porphyry copper systems in southwestern alaska

platinum group minerals in the middle group of chromitite layers at marikana western bushveld complex indications for collection mechanisms and postmagmatic modification the platinum group minerals in a drill core taken through the middle group of chromitite layers in the critical zone at marikana in the western bushveld complex were found to consist mainly of laurite as inclusions in chromite grains the platinum group minerals containing pt pd and rh are concentrated in the intercumulus silicates and frequently associated with base metal sulphides up to about 20 of all platinum group minerals in the investigated chromitite layers contain sub stantial amounts of as the base metal sulphides are strongly modified in the postmagmatic stage which led to a significant loss of fe and s in this way concentrating cu ni and the platinum group elements by factors of up to 10 interaction between chromite and base metal sulphides cannot account for all the fe lost in chromite poor samples and the importance of additional processes is indicated inclusions in chromite and orthopyroxene indicate the formation of discrete platinum group minerals and as rich phases before the

satellite observations of small coastal ocean eddies in the southern california bight this study describes the characteristics of extensive small scale coastal ocean eddies in the southern california bight these surface features were primarily detected by using ers 1 and ers 2 synthetic aperture radar sar satellite imagery from 1992 to 1998 the eddies predominantly cyclonic in their rotation appeared to result from several forcing mechanisms they were mainly observed within the santa barbara channel and the santa monica san pedro basin regions and appeared to be seasonal in their distribution observed eddy diameters were all less than 50 km with over 70 less than 10 km the sar data were complemented by sea surface temperature measurements derived from advanced very high resolution radiometer satellite imagery as well as in situ data from moorings and drifters that provided substantial verification of the small scale eddies these findings are significant in that the eddies were in general smaller in size and more abundant than previously reported additionally these results provide further evidence of the complex near surface circulation within the southern california bight with important implications for nutrient flux productivity plankton patchiness larval transport and recruitment and dispersal of pollutants

primary stratigraphic controls on ore mineral assemblages in the wannaway komatiite hosted nickel sulfide deposit kambalda camp western australia abstract the 18 m long uwa 04 02 drillcore from the fe ni cu pge wannaway deposit in the widiemooltha dome district eastern goldfields western australia intersects the whole sequence of a komatiite hosted layer of metal rich sulfide magma in spite of regional deformation and amphibolite facies metamorphism the sequence in the drillcore still preserves some of the original magmatic textures and assemblages and these were examined in a great detail the magmatic orebody typically consists of basal massive sulfides grading to net textured matrix and disseminated sulfide mineralization upward into the komatiite host the ore zone is underlined by sulfide rich black shale passing to basalts country rock xenoliths are locally enclosed in the massive sulfides portions of the drillcore untouched by penetrative deformation and with minimal imprint by late stage serpentinization allow the construction of a fairly complex framework where mineral assemblages and mineral chemistry of sulfides spinels and silicates vary systematically with stratigraphy and may reflect original conditions of ore deposition the general ore assemblage is dominated by fe sulfide and pentlandite with minor sphalerite and chalcopyrite spinels zn rich chromite ti magnetite alabandite mns accessory pge rich sulfarsenides and tellurides and rare molybdenite monoclinic and high s hexagonal pyrrhotite and fresh zn mn rich chromite characterize the basal massive facies whereas the matrix ore facies is marked by magnetite sphalerite and a gradually s depleted and reduced assemblage now represented by troilite exsolving low s hexagonal pyrrhotite and alabandite compositional modifications of the fe sulfides across the whole orebody and occurrence of alabandite testify to progressive sulfur loss concomitant with the establishment of low fo2 conditions over several meters upsequence in the matrix ore facies pge rich sulfarsenides disseminated across the whole mineralized sequence display igneous textures and pge fractionation trends the composition of olivine intergrown with matrix sulfides and in the serpentinized hangingwall komatiite deviates from the typical unmetamorphosed komatiite related highly forsteritic type however the fe mn and zn contents of olivine crystals decrease systematically and gradually with distance from mineralization towards the hangingwall komatiite contamination may be an alternative to metamorphic recrystallization of olivine as the cause of these trends the role of contamination is also shown by the trends of whole rock data from the mineralized sequence across the entire drillcore textures and mineral chemistry of minerals from the different rock facies in the drillcore are evaluated in terms of metamorphic effects although the remarkable relationship observed between stratigraphy and several major and accessory phases over metric distances is suggestive of alternative options including primary processes involving the komatiitic lava flow in its interaction both with the black shale substrate and with the sulfide melt ponding at its base

sun glitter imaging of submarine sand waves on the taiwan banks determination of the relaxation rate of short waves natural science foundation of china 40476023 40876031 chinese ministry of science and technology 2009cb421205

aeromagnetic signature of porphyry copper systems in northern chile and its geologic implications the compilation of a large aeromagnetic high resolution dataset acquired for base metals exploration in northern chile between lat 19 45 s and 27 15 s revealed a pattern of transorogenic regional magnetic anomalies these anomalies occur as generally east west stripes of negative residual magnetic intensity of more than 100 nanotesla nt they have an east west extension of some tens of kilometers and a north south width of some 5 to 10 km some of them can be observed continuously from the coast to the volcanic belt their residual intensity is typically more than 100 nt they also show a loose north south spacing it is observed that all known porphyry copper deposits of the investigated segment are spatially related to these transverse magnetic anomalies we propose that the transverse magnetic anomalies are the magnetic response to the loci of emplacement of intrusive bodies of batholithic size along paths of the advancing magmatic front of the active continental margin the occurrence of several important porphyry copper deposits grouped in clusters within a district is explained as being related to a common parental intrusive complex which is geophysically signaled by a corresponding transverse magnetic anomaly a possible implication of the observed relationship between porphyry copper deposits and transverse magnetic anomalies is the quasideterministic restriction of porphyry copper deposits to certain orogen transverse loci necessary condition and the corresponding consequences for future exploration strategies

an improved composite surface model for the radar backscattering cross section of the ocean surface 2 model response to surface roughness variations and the radar imaging of underwater bottom topography in the companion paper we have presented an improved composite surface model for the calculation of normalized radar backscattering cross sections nrcs of the ocean surface the proposed model accounts for the impact of the full two dimensional ocean wave spectrum on the radar backscatter and was shown to reproduce measured absolute nrcs values for a variety of radar configurations and wind speeds satisfactorily after some reasonable tuning of the input ocean wave spectrum this paper focuses on the modulation of the nrcs in the presence of spatially varying surface currents first the sensitivity of the nrcs to intensity variations of different ocean wave spectral components is investigated then the hydrodynamic modulation of the wave spectrum over underwater bottom topography in tidal waters is computed in different ways and the resulting radar signatures are discussed the composite surface model yields comparable radar signatures at high 10 ghz x band and low 1 ghz l band radar frequencies which is in much better agreement with experimental results than the predictions of a first order bragg scattering model on the other hand measured variations of the nrcs at high radar frequencies appear to be still underestimated in some cases which may be due to shortcomings of our description of the wave current interaction by conventional weak hydrodynamic interaction theory possible improvements of the theory are discussed and requirements for future experiments are formulated

pluton spacing and the thickness of crustal layers in baja california abstract the concept that the spacing of volcanoes and plutons equals the depth to magma source layer is applied to the plutons of baja california simple analysis of spacing indicates that gabbro was derived from a depth of ca 21 km and granite from 11 to 20 km it is further suggested that the shorter spacing of many smaller plutons results from local layer control on magma ponded beneath an upper brittle crustal layer ca 6 km thick these results compare favourably with a published crustal profile an attempt is made to reconcile the simple layer model used for this analysis with a more complex subduction model

a special issue devoted to porphyry copper deposits of northern chile chile is known worldwide as the site of one of the largest copper concentrations on earth a total resource including production of about 400 million tons mt of fine copper has been identified in 50 porphyry copper deposits and numerous prospects fig 1 considering 10 mt of contained fine copper as a minimum tonnage to classify a porphyry copper deposit as a giant ore deposit the chilean cordillera contains nine of the 16 giant porphyries along the circum pacific belt among them are the three largest of all el teniente rio blanco los bronces and chuquicamata fig 1 all containing resources plus production of more than 50 mt of fine copper currently chile annually produces about 4 6 mt of fine copper that represents about 37 percent of the world production this enormous geologic potential has triggered numerous international mining companies to concentrate their exploration efforts in the central andes with emphasis in chile during the past 25 years exploration expenditures have surpassed a figure on the order of us 2 billion as a result a total of 76 copper and gold discoveries have been made 24 of which are already in production cabello 2000 among them the most relevant discoveries are the porphyries at la escondida escondida norte zaldivar rosario and ujina in the collahuasi mining district quebrada blanca lomas bayas and in the last 5 years spence and gaby sur the presence of such a significant number and large size of copper porphyries intrigued several generations of researchers during the twentieth century the ongoing exploration efforts have enhanced the interest in understanding the andean geological evolution and metallogenesis the geological processes that are common factors in controlling the emplacement of these orebodies have been the subject of research by numerous individuals in chile and elsewhere the support of mining companies has been

data fusion and porphyry copper prospectivity models southeastern arizona abstract mineral exploration programs commonly use a combination of geological geophysical and remotely sensed data to detect sets of optimal conditions for potential ore deposits prospectivity mapping techniques can integrate and analyse these digital geological data sets to produce maps that identify where optimal conditions converge three prospectivity mapping techniques weights of evidence fuzzy logic and a combination of these two methods were applied to a 32 000 km 2 study area within the southeastern arizona porphyry cu district and then assessed based on their ability to identify new and existing areas of high mineral prospectivity validity testing revealed that the fuzzy logic method using membership values based on an exploration model identified known cu deposits considerably better than those that relied solely on weights of evidence and slightly better than those that used a combination of weights of evidence and fuzzy logic this led to the selection of the prospectivity map created using the fuzzy logic method with membership values based on an exploration model three case study areas were identified that comprise many critical geological and geophysical characteristics favourable to hosting porphyry cu mineralisation but not associated with known mining or exploration activity detailed analysis of each case study has been performed to promote these areas as potential targets and to demonstrate the ability of prospectivity modelling techniques as useful tools in mineral exploration programs

platinum group elements in sulphide minerals platinum group minerals and whole rocks of the merensky reef bushveld complex south africa implications for the formation of the reef the concentrations of platinum group elements pge co re au and ag have been determined in the base metal sulphide bms of a section of the merensky reef in addition we performed detailed image analysis of the platinum group minerals pgm the aims of the study were to establish 1 whether the bms are the principal host of these elements 2 whether individual elements preferentially partition into a specific bms 3 whether the concentration of the elements varies with stratigraphy or lithology 4 what is the proportion of pge hosted by pgm 5 whether the pgm and the pge found in bms could account for the complete pge budget of the whole rocks in all lithologies most of the pge 65 up to 85 are hosted by pgm essentially pt fe alloy pt pd sulphide pt pd bismuthotelluride lesser amounts of pge occur in solid solution within the bms in most cases the pgm occur at the contact between the bms and silicates or oxides or are included within the bms pentlandite is the principal bms host of all of the pge except pt and contains up to 600 ppm combined pge it is preferentially enriched in pd rh and co pyrrhotite contains rh os ir and ru but excludes both pt and pd chalcopyrite contains very little of the pge but does concentrate ag and cd platinum and au do not partition into any of the bms instead they occur in the form of pgm and electrum in the chromitite layers the whole rock concentrations of all the pge except pd are enriched by a factor of five relative to s ni cu and au this enrichment could be attributed to bms in these layers being richer in pge than the bms in the silicate layers however the pge content in the bms varies only slightly as a function of the stratigraphy the bms in the chromitites contain twice as much pge as the bms in the silicate rocks but this is not sufficient to explain the strong enrichment of pge in the chromitites in the light of our results we propose that the collection of the pge occurred in two steps in the chromitites some pgm formed before sulphide saturation during chromitite layer formation the remaining pge were collected by an immiscible sulphide liquid that percolated downward until it encountered the chromitite layers in the silicate rocks pge were collected by only the sulphide liquid

the patricia zn pb ag epithermal ore deposit an uncommon type of mineralization in northeastern chile the patricia ore deposit represents an unusual example of economic zn pb ag mineralization at the northernmost end of the late eocene oligocene metallogenic belt in chile it is hosted by volcano sedimentary units which are typically tuffaceous and andesitic breccias the ore body consists of a set of subvertical e w vein systems developed under a sinistral strike slip regime that included transtensive domains with generalized extensional structures where the ores were deposited the deposit is divided into two blocks by a set of nnw ese trending reverse faults which uplifted the eastern block and exhumed thicker and deeper parts of the deposit at least 200 m of volcano sedimentary pile hosting the mineralization has been eroded in this block by contrast the western block exposes a shallower part of the system where cherts amorphous silica and jasperoids occur three main stages of mineralization have been defined 1 pre ore stage is characterized by early quartz pyrite and arsenopyrite 2 base metal and silver stage characterized by sphalerite 6 to 15 mol fes galena chalcopyrite pyrrhotite and ag bearing minerals freibergite polybasite stephanite pyrargyrite freieslebenite and acanthite and 3 post ore stage characterized by late quartz kutnohorite and minor sulfides arsenopyrite sphalerite pyrite galena ag bearing minerals and pb sulfosalts whole ore geochemistry shows two groups of elements that are positively correlated 1 ag cd cu pb zn related to the base metal sulfides and 2 au as ge sb w related to arsenopyrite and pyrite hydrothermal alteration is pervasive in the outcropping mineralized areas including silicification and locally vuggy silica textures at depth chloritic and sericitic alteration is developed along vein selvages and is superimposed to the regional propylitic alteration fluid inclusions indicate that the base metal ores were deposited from 250 to 150 c moderate salinity fluids 1 9 wt nacl the pre ore stage is characterized by a saline fluid 6 22 wt nacl and between 210 and 250 c whereas the post ore stage has salinity of 4 8 wt and temperature from 175 to 215 c cooling was the mechanism of ore mineral precipitation in the patricia deposit although mixing of fluids could have occurred in the pre ore stage mineralogical geochemical and fluid inclusion evidence is consistent with an intermediate sulfidation is epithermal deposit type this study highlights the high potential for hidden economic mineralization at depth in the western block and for extension of the ore body both to the south and to deeper levels in the eastern block of the patricia ore deposit to a larger extent the implications of finding such polymetallic epithermal style of mineralization in the northern chile precordillera is relevant both to the regional metallogenic perspective and to the exploration potential of the region where the late eocene early oligocene metallogenic belt apparently disappears

structural setting and shape analysis of nickel sulfide shoots at the kambalda dome western australia implications for deformation and remobilization integrated three dimensional structural studies have led to new insights into the geologic controls on the distribution of magmatic nickel sulfide ore shoots associated with metakomatiites at the archean kambalda dome western australia exploration models emphasize volcanic channels in deep embayments trough structures modified by thermal erosion at the base of turbulent lava flows however analysis of three dimensional models of the kambalda exploration database reveals ore shoot scale controls consistent with the regional deformation sequence d1 to d4 ore shoots in d1 settings e g ken shoot are transposed into the north northwest d1 trend and have asymmetric trough structures with reentrant updip margins indicating a sense of movement opposite to that on the kambalda dome ore shoots in d2 settings e g lunnon shoot have asymmetric trough structures bound by low angle thrusts indicating a sense of movement typical of that on the dome with thrust movement of ore into the talc and carbonated hanging wall rocks lacking primary igneous features e g mcmahon shoot ore shoots in d3 settings are offset by normal faults which host gold mineralization at the south end of the kambalda dome e g hunt shoot or by major reverse faults at the north end of the dome e g otter juan shoots ore shoots in d4 settings fisher shoot are transposed from the north northwest trend into the north to north northeast d4 trend in contrast ore shoots associated with shallow poorly defined trough structures with or without serpentinized hanging wall showing relict igneous features e g durkin shoot indicate preserved volcanic control the spectrum of volcanic and structural controls indicates a continuum of kambalda ore shoots from a volcanic controlled end member 3 shoots in shallow trough structures with relict igneous features through structurally modified 7 shoots in deep trough structures without relict features to a structurally controlled end member 1 shoot tectonically emplaced in the hanging wall with deformation features shape analysis of the three dimensional models indicates that the structurally modified and controlled ore shoots have prolate shapes and two of the volcanic controlled ore shoots have oblate shapes comparison of the prolate shapes with the shapes of strain indicators reveals the importance of constrictional d1 deformation in elongation of the ore shoots particularly at the north and south ends of the kambalda dome the oblate volcanic controlled end members reflect low strain settings adjacent to major fault zones comparisons to previous experimental systems suggest that the ore shoots and metakomatiite deformed preferentially by ductile flow the importance of deformation controls on nickel sulfide distribution at the kambalda dome means that exploration for kambalda style mineralization should take into consideration the deformation history of terranes that host ore

introduction studies of ocean wave spectra from the shuttle imaging radar b experiment imagery of ocean surface waves obtained from synthetic aperture radar sar provides a unique two dimensional fine resolution view of the ocean wave field which has been long thought to be of considerable value for studying air sea inter action wave generation and propagation and wave current refraction wave spectra from sar have also been thought to be extremely useful for updating and verifying global wave forecast models such promise prompted a sar to be placed on seasat an oceanographic satellite which operated in a rather glorious mode for only a little over 3 months in 1978 this imagery has been well studied and indeed has demonstrated the feasibility of acquiring useful directional wave spectra from space e g vesecky and stewart 1982

distribution of platinum group elements in the platreef at overysel northern bushveld complex a combined pgm and la icp ms study detailed mineralogical and laser ablation inductively coupled plasma mass spectrometry studies have revealed the physical manifestation of the platinum group elements pge within the platreef at overysel northern bushveld complex south africa the pge in the platreef were originally concentrated in an immiscible sulfide liquid along with semi metals such as bi and te as the sulfide liquid began to crystallize virtually all the os ir ru and rh partitioned into monosulfide solid solution mss which on further cooling exsolved to form pyrrhotite and pentlandite with os ir and ru remaining in solid solution in both phases with rh prefentially partitioning into pentlandite platinum some pd and au were concentrated in the residual sulfide liquid after mss crystallization and were then concentrated in an immiscible late stage melt along with semi metals which was expelled to the grain boundaries during crystallization of intermediate solid solution iss to form pt and pd tellurides and electrum around the margins of the sulfide grains tiny droplets of this melt trapped in the crystallizing mss and iss cooled to form pt bi te microinclusions in all sulfide phases whilst the excess pd was accommodated in solid solution in pentlandite minor redistribution and recrystallization by hydrothermal fluids occurred around xenoliths and at the very base of the mineralized zone within the footwall however the overall lack of secondary alteration coupled with the volatile poor nature of the gneissic footwall have allowed the preservation of what may be the most primary style of platreef mineralization the lack of pgm inclusions within early liquidus phases suggests very early sulfur saturation in the platreef lending support to theories involving s saturation occurring prior to intrusion of the platreef possibly within a staging chamber

sperrylite saturation in magmatic sulfide melts implications for formation of pge bearing arsenides and sulfarsenides sperrylite ptas 2 is one of most common pt minerals but the processes whereby it forms are not clearly established most commonly it is associated with the major component base metal sulfide minerals pyrrhotite pentlandite and chalcopyrite which are believed to have crystallized from magmatic sulfide melts hence sperrylite is thought to have formed by crystallization from a sulfide melt or by exsolution from sulfide minerals however sperrylite is also found associated with silicate and oxide minerals where it is thought to have formed by crystallization from the silicate magma to investigate the conditions under which sperrylite could crystallize from a magmatic sulfide melt we investigated sperrylite saturation in fe ni cu s sulfide melts under controlled f o 2 and f s 2 at 910 1060 c and 1 bar the as and pt concentrations in the sulfide melt at sperrylite saturation increase from 0 23 0 41 to 2 2 4 4 wt and from 0 36 0 65 to 1 9 2 8 wt respectively as the iron concentration in the sulfide melt decreases from 50 to 36 wt at 910 1060 c we show that transitional metal concentrations particular iron and nickel as well as sulfur and oxygen fugacities influence as and pt concentrations in the sulfide melt at sperrylite saturation these intensive variables appear to effect sperrylite solubility by influencing the oxidation state of as in the sulfide melt the measured concentrations of as and pt in sperrylite saturated sulfide melts produced in our experiments are much higher than that in most natural sulfides implying that arsenides and sulfarsenides will not reach saturation in natural magmatic sulfide melts at high temperatures unless the magma has been contaminated with an exceptionally as rich rock this suggests that the observed arsenides and sulfarsenides in natural sulfide ores were not formed by crystallization from unfractionated sulfide melts at high temperatures above 900 c but might form at low temperatures below 900 c

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

the role of preexisting geologic architecture in the formation of giant porphyry related cu au deposits examples from new guinea and chile development of giant porphyry related copper and or gold deposits in new guinea and northern and central chile occurred during tertiary magmatic events that overprinted earlier extensional tectonic settings the earlier tectonic settings consisted of a mesozoic passive margin in new guinea a jurassic cretaceous back arc basin in northern chile and an oligocene intra arc basin in central chile the preexisting architecture of the basement rocks the fault systems and the stratigraphic packages associated with these settings played a strong role in controlling development of the giant deposits although the extensional tectonic settings in these terranes were different they share a number of elements that were used during formation of the tertiary ore deposits these were the presence of coupled systems of deeply detached listric synsedimentary faults and steep transverse faults and the presence of a relatively flat lying heterogeneous volcano sedimentary rock package during tertiary collision the deeply detached listric faults were inverted and strongly focused uplift exhumation and associated overpressuring induced failure and fluid flow in addition steep transverse faults were activated to form wrench systems with attendant steep deeply tapping pathways for magma and or fluid associated with dilatant jogs flexures or fault intersections ore deposits are commonly located in the hanging wall of the thrust faults under compression associated with collision the competent units of flat lying stratigraphic packages formed plates overlying the folded weaker units underneath and separated by a detachment or otherwise faulted contact examples of the competent upper units include the darai mendi limestone or equivalents in new guinea and the lavas of the farellones formation in central chile these plates appear to have impeded magma ascent and formed a cap on a magma and or fluid system pressurized by collision and orogenesis this geometry provided an ideal location for focusing of magmas and magmatic hydrothermal fluids from these three example terranes a set of exploration indicators have been constructed to highlight belts that are prospective for giant porphyry cu systems these indicators include 1 the presence of magmatic arcs that migrated into preexisting extensional architectures 2 coupled systems of deeply detached listric synsedimentary faults and steep transverse faults 3 rigid basement blocks that could form regional stress field perturbations and 4 fold belts with a major plate to 50 km wide of competent relatively undeformed or gently folded stratigraphy overlying more complexly folded and faulted parts of the sequence

on the determination of characteristics of the interior ocean dynamics from radar signatures of internal solitary waves in this paper we discuss two different methods of inferring characteristics of the interior ocean dynamics from radar signatures of internal solitary waves visible on synthetic aperture radar sar images the first one consists in the recognition and the interpretation of sea surface patterns of internal solitary waves the second one consists in the analysis of the modulation depth of the normalized radar backscattering cross section nrcs associated with internal solitary waves for this purpose we consider a data set composed of sar and in situ measurements carried out from 1991 to 1997 in the region of the strait of messina the recognition and the interpretation of sea surface patterns of internal solitary waves in the strait of messina can be used to study characteristics of the density distribution in the area the internal wave field varies with seasonal variations in the vertical density stratification and with remotely induced variations i e variations induced by the larger scale circulation in the horizontal density distribution in order to inquire into the possibility of inferring parameters of the interior ocean dynamics by analyzing the modulation of the nrcs associated with internal solitary waves several numerical simulations are carried out using a radar imaging model these simulations are performed by assuming different wind conditions and internal wave parameters it is shown that an accurate knowledge of wind conditions is crucial for deriving internal wave parameters and hence parameters of the interior ocean dynamics from the modulation of measured nrcs associated with internal solitary waves

an issue devoted to magmatic sulfide mineralization and ore deposits with special emphasis on china preface the 12th international ni cu pge symposium held in guiyang in june 2012 brought together most of the world s leading authorities on magmatic sulfide deposits and covered a wide range of topics and deposits not surprisingly a high proportion of the papers presented at the symposium dealt with ni cu pge sulfide deposits in china several of which have received limited coverage to date in the western literature this special issue brings together a number of important new advances on ni cu pge deposits in the central asian orogenic belt including the huangshandong hongqiling poyi and erbutu deposits in china other specific studies on chinese deposits cover the well known jinchuan deposit and the mineralization associated with the zhubu intrusion in the emeishan large igneous province an account of the komatiite related spotted quoll deposit in western australia and a description of newly discovered deep seated ultramafic cumulates in the bushveld complex complete the collection of locality based papers the remainder of the issue is taken up with more generic papers covering aspects of magmatic sulfide formation at different scales geochemical modeling of s solubility in mafic magmas and fe ni partitioning between olivine and sulfide liquid the role or lack of it of subcontinental lithospheric mantle in ore formation and an account of new methodologies for three dimensional characterization of textures in magmatic sulfide ores the volume opens with a paper on the sulfide geochemistry of the jinchuan deposit the largest ni cu pge in china and the third largest in the world chen et al 2013 discuss wide variations in sulfide tenors i e the metal content of the sulfide component of the rock in the western part of the jinchuan intrusion they attribute variations in total pge contents and cu pge ratios to a combination of factors variable degrees of pre emplacement pge depletion of the parental magmas and in situ differentiation of

petrology of the yerington batholith nevada evidence for evolution of porphyry copper ore fluids the jurassic yerington batholith western nevada is a composite pluton that contains several centers of porphyry copper mineralization and is exposed in structural cross section at paleodepths ranging from 0 to 8 km within these exposures the mcleod hill quartz monzodiorite bear quartz monzonite and luhr hill granite form successive intrusions that are in turn volumetrically smaller approximately 75 19 and 6 vol respectively more deeply emplaced tops at 65 km 3 luhr hill granite the low cu content approximately 10 ppm of the granite would allow extraction of approximately 50 ppm cu from it during crystallization these data suggest an orthomagmatic model in which both high and low density saline aqueous fluids formed during exsolution of water from the crystallizing luhr hill granite and from which salts cu fe and s strongly partitioned into the high density ore fluid low density fluids may have risen from the magma as a vapor plume mineralization occurred when fluid overpressures caused fracturing of wall rock and upward intrusion of granite porphyry dikes and high density saline ore fluids both the f sub o 2 path during subsolidus cooling and the deposition of most s as chalcopyrite pyrite in ore suggest that reduction of magmatic s to sulfide may have been a mechanism for oxidation of magmatic ferromagnesian silicate and fe ti oxide minerals

the role of the antofagasta calama lineament in ore deposit deformation in the andes of northern chile during the late jurassic early oligocene interval widespread hydrothermal copper mineralization events occurred in association with the geological evolution of the southern segment of the central andes giving rise to four ns trending metallogenic belts of eastward decreasing age late jurassic early cretaceous late paleocene early eocene and late eocene early oligocene the antofagasta calama lineament acl consists of an important dextral strike slip ne trending fault system deformation along the acl system is evidenced by a right lateral displacement of the late paleocene early eocene metallogenic belts furthermore clockwise rotation of the early cretaceous mantos blancos copper deposit and the late paleocene lomas bayas porphyry copper occurred in the late eocene early oligocene metallogenic belt a sigmoidal deflection and a clockwise rotation is observed in the acl the acl is thought to have controlled the emplacement of early oligocene porphyry copper deposits 34 37 ma toki genoveva quetena and opache whereas it deflected the late eocene porphyry copper belt 41 44 ma esperanza telegrafo centinela and polo sur ore deposits these observations suggest that right lateral displacement of the acl was active during the early oligocene we propose that the described structural features need to be considered in future exploration programs within this extensively gravel covered region of northern chile