gold in porphyry copper deposits its abundance and fate abstract porphyry copper deposits are among the largest reservoirs of gold in the upper crust and are important potential sources for gold in lower temperature epithermal deposits whether gold remains in porphyry copper deposits is important both to their economic attractiveness and to the distribution of gold in the upper crust cu au atomic ratios of porphyry copper ore deposits form a continuous range from about 5000 to 5 000 000 with a median near 40 000 which separates gold rich and gold poor deposits gold is found in porphyry copper deposits in solid solution in cu fe and cu sulfides and as small grains of native gold usually along boundaries of bornite sims ion probe analyses of ore minerals from the gold rich batu hijau kingking and skouries porphyry copper deposits show that bornite contains about 1 ppm au whereas chalcopyrite contains about an order of magnitude less chalcocite and covellite contain 10 20 ppm au but are not abundant enough to account for a significant part of the gold endowment in many porphyry copper deposits the amount of gold presently in solid solution in cu fe sulfides is not adequate to account for all the gold in porphyry copper deposits and the remainder is present as micron scale grains of native gold experiments in the cu fe s au system show that bornite and chalcopyrite can contain about 1000 ppm gold at typical porphyry copper formation temperatures of 600 700 c and indicate that bornite and chalcopyrite in porphyry copper deposits were saturated with respect to gold at temperatures of only 200 300 c in contrast cu au ratios of bulk ore in porphyry copper deposits would require bornite and chalcopyrite to be saturated with respect to gold at temperatures similar to those at which primary potassic ore and alteration are thought to form this indicates that the maximum gold endowment of porphyry copper deposits is probably fixed by the amount of gold that will go into solid solution in cu fe sulfides when the deposit forms at high temperature and that gold is not commonly added later from other sources although it can be redistributed during cooling or later events the experimental data also suggest that high temperature 600 700 c vapors can extract considerably more gold from porphyry copper systems than can low temperature 300 c alteration comparison to cu au ratios of volcanic emissions suggests further that high temperature processes remove copper relative to gold from porphyry copper systems whereas low temperature processes remove gold preferentially and that this can account for deposits with extremely low and high cu au ratios respectively deposits with cu au ratios between about 20 000 and 100 000 however probably reflect different degrees of removal of gold or copper by immiscible sulfides

mass flux and undertow in a surf zone abstract the mass of water carried shoreward by the breaking waves in a surf zone will in a two dimensional situation be compensated by a seaward return flow the undertow it is shown that the undertow is driven by the local difference between radiation stress and the set up pressure gradient which only balance each other in average over the depth turbulent shear stresses are required to maintain a steady situation comparison with measurements confirms the theoretical results

first whiffs of atmospheric oxygen triggered onset of crustal gold cycle lack of a suitable gold source has long been regarded as a major argument against a palaeoplacer model for the exceptionally well endowed witwatersrand gold province by comparing worldwide witwatersrand type deposits occurrences ranging in age from 3 1 to 1 8 ga we propose that the primary concentration of gold in the continental crust resulted from atmospheric and biological evolution in the mesoarchaean a high au flux off the archaean land surface orders of magnitude greater than today s was a consequence of the chemistry of the mesoarchaean atmosphere and hydrosphere when early life gradually changed from anaerobic anoxygenic to oxygenic photosynthesizers at around 3 0 ga the first whiffs of free oxygen produced by photosynthesis under an overall reducing atmosphere provided the ideal trap for au dissolved in the huge reservoir in meteoric and shallow sea water oxidative precipitation of gold on the surface of the o2 producing microbes probably cyanobacteria could fix huge amounts of gold over large areas some of this microbially mediated gold is still preserved in thin kerogen layers carbon seams that typically developed on erosional unconformities scour surfaces and bedding planes in near shore environments at around 2 9 ga this gold provided the principal source for the very rich placer deposits that formed by the subsequent sedimentary reworking of the delicate microbial mats on aeolian deflation surfaces into fluvial channels and delta deposits represented by meso to neoarchaean auriferous conglomerates tectonic reworking of these first gold rich sediments by orogenic processes explains the temporal peak of orogenic type gold formation at around 2 7 to 2 4 ga with time the strongly gold enriched archaean sediments became progressively eroded covered or tectonically reworked and their role as potential source of younger placer deposits diminished this explains why witwatersrand type deposits younger than 2 4 ga are rare and far less well endowed and effectively missing in the rock record after 1 8 ga

gold in the oceans through time during sedimentation and diagenesis of carbonaceous shales in marine continental margin settings au is adsorbed from seawater and organic matter and becomes incorporated into sedimentary pyrite la icpms analysis of over 4000 sedimentary pyrite grains in 308 samples from 33 locations around the world grouped over 123 determined ages has enabled us to track in a first order sense the au content of the ocean over the last 3 5 billion years gold was enriched in the meso and neoarchean oceans several times above present values then dropped by an order of magnitude from the first great oxidation event goe1 through the paleoproterozoic to reach a minimum value around 1600 ma gold content of the oceans then rose with perturbations through the meso and neoproterozoic showing a steady rise at the end of the proterozoic 800 to 520 ma which most likely represents the effects of the second great oxidation event goe2 gold in the oceans was at a maximum at 520 ma when oxygen in the oceans rose to match current maximum values in the archean and proterozoic the au content of seawater correlates with the time distribution of high mg greenstone belts black shales and banded iron formations suggesting that increases in atmospheric oxygen and marine bio productivity combined with the higher background of au in komatiitic and mg rich basalts were the first order causes of the pattern of au enrichment in seawater we suggest the lack of major au deposits from 1800 to 800 ma is explained by the low levels of au in the oceans during this period

magma evolution and the formation of porphyry cu au ore fluids evidence from silicate and sulfide melt inclusions silicate and sulfide melt inclusions from the andesitic farallon negro volcanic complex in nw argentina were analyzed by laser ablation icpms to track the behavior of cu and au during magma evolution and to identify the processes in the source of fluids responsible for porphyry cu au mineralization at the 600 mt bajo de la alumbrera deposit the combination of silicate and sulfide melt inclusion data with previously published geological and geochemical information indicates that the source of ore metals and water was a mantle derived mafic magma that contained approximately 6 wt h2o and 200 ppm cu this magma and a rhyodacitic magma mixed in an upper crustal magma chamber feeding the volcanic systems and associated subvolcanic intrusions over 2 6 million years generation of the ore fluid from this magma occurred towards the end of this protracted evolution and probably involved six important steps 1 generation of a sulfide melt upon magma mixing in some parts of the magma chamber 2 partitioning of cu and au into the sulfide melt enrichment factor of 10 000 for cu leading to cu and au concentrations of several wt or ppm respectively 3 a change in the tectonic regime from local extension to compression at the end of protracted volcanism 4 intrusion of a dacitic magma stock from the upper part of the layered magma chamber 5 volatile exsolution and resorption of the sulfide melt from the lower and more mafic parts of the magma chamber generating a fluid with a cu au ratio equal to that of the precursor sulfide 6 focused fluid transport and precipitation of the two metals in the porphyry yielding an ore body containing au and cu in the proportions dictated by the magmatic fluid source the cu s ratio in the sulfide melt inclusions requires that approximately 4 000 ppm sulfur is extracted from the andesitic magma upon mixing this exceeds the solubility of sulfide or sulfate in either of the silicate melts and implies an additional source for s the extra sulfur could be added in the form of anhydrite phenocrysts present in the rhyodacitic magma it appears thus that unusually sulfur rich not cu rich magmas are the key to the formation of porphyry type ore deposits our observations imply that dacitic intrusions hosting the porphyry cu au mineralization are not representative of the magma from which the ore fluid exsolved the source of the ore fluid is the underlying more mafic magma and unaltered andesitic dikes emplaced immediately after ore formation are more likely to represent the magma from which the fluids were generated at alumbrera these andesitic dikes carry relicts of the sulfide melt as inclusions in amphibole sulfide inclusions in similar dykes of other less explored magmatic complexes may be used to predict the au cu ratio of potential ore forming fluids and the expected metal ratio in any undiscovered porphyry deposit

static wave setup with emphasis on damping effects by vegetation and bottom friction abstract wave setup can contribute significantly to elevated water levels during severe storms in florida we have found that wave setup can be 30 to 60 of the total 100 year storm surge in areas with relatively narrow continental shelves such as many locations along the pacific coast of the united states wave setup can be an even larger proportionate contributor of anomalous water levels during major storms wave setup can be considered as comprising two components with the first being the well known static wave setup resulting from the transfer of breaking wave momentum to the water column the second oscillating component is a result of nonlinear transfer of energy and momentum from the primary linear spectrum to waves with length and time scales on the order of the wave groups static wave setup is the focus of this paper with emphasis on effects due to internal or surface forces that act on the wave system and cause both dissipation of wave energy and transfer of momentum in particular the effects of wave damping by vegetation and bottom friction are considered linear wave theory is applied to illustrate these effects and for shallow water waves the setup is reduced by two thirds the amount that would occur if the same amount of energy dissipation occurred in the absence of forces effects of nonlinear waves are then considered and it is found for a shallow water wave of approximately one half breaking height that a wave setdown rather than setup occurs due to damping by vegetation and bottom friction the problem of wave setup as waves propagate through vegetation was stimulated by studies to establish hazard zones associated with 100 year storm events along the shorelines of the united states these storms can generate elevated water levels exceeding 4 to 6 m and can result in overland wave propagation as these waves propagate through vegetation and damp the question arose as to the contribution of this process to elevated mean water levels through additional wave setup

copper deposition during quartz dissolution by cooling magmatic hydrothermal fluids the bingham porphyry abstract scanning electron microscope cathodoluminescence imaging is used to map successive generations of fluid inclusions in texturally complex quartz veinlets representing the main stage of ore metal introduction into the porphyry cu au mo deposit at bingham utah following conventional fluid inclusion microthermometry laser ablation inductively coupled plasma mass spectrometry la icpms is applied to quantify copper and other major and trace element concentrations in the evolving fluid with the aim of identifying the ore forming processes textures visible in cathodoluminescence consistently show that the bulk of vein quartz q1 characterized by bright luminescence crystallized early in the vein history cu fe sulfides are precipitated later in these veins in a microfracture network finally filled with a second generation of dull luminescing q2 quartz mapping of brine and vapor inclusion assemblages in these successive quartz generations in combination with la icpms microanalysis shows that the fluids trapped before and after cu fe sulfide precipitation are very similar with respect to their major and minor element composition except for copper copper concentrations in inclusions associated with ore formation drop by two orders of magnitude in a tight pressure temperature interval between 21 and 14 mpa and 425 350 c several hundred degrees below the temperature of fluid exsolution from the magma copper deposition occurs within a limited p t region in which sulfide solubility shows strong normal temperature dependence while quartz solubility is retrograde this permits copper sulfide deposition while secondary vein permeability is generated by quartz dissolution the brittle to ductile transition of the quartz feldspar rich host rocks occurs in the same temperature range which further enhances vein reactivation and promotes cooling and expansion of fluids ascending across the transition from lithostatic to hydrostatic conditions

on wave set up in shoaling water with a rough sea bed in very gradually shoaling coastal water the energy of incident waves appears to be absorbed not by breaking at the upper surface but predominantly by turbulent dissipation near the rippled sea bed the question has been asked whether there can be then any wave set up that is any increase in the mean water level at or close to the shoreline to answer this question the equations of wave energy and momentum in water of slowly varying depth are generalized so as to include the presence of a dissipative boundary layer at the bottom it is then shown that the resulting equation for the mean surface slope can be integrated exactly to give the mean surface depression the set down in terms of the local wave amplitude and water depth outside the surf zone in the special case of a uniform beach slope s a closed expression is obtained for the wave amplitude in terms of the local depth under two different sets of conditions i when the thickness of the boundary layer at the bottom is assumed to be constant and ii for waves over a rippled bed when the boundary layer thickness corresponds to the measured dissipation of energy in oscillatory waves over steep sand ripples in both cases it is found that there exists a maximum bottom slope s below which the wave amplitude must diminish monotonically towards the shoreline this maximum value of s is of order 10 3 the waves can indeed penetrate close to the shoreline without breaking and the corresponding wave set up is negligible an example of where suitable conditions exist is on the continental shelf off north carolina

effects of wave rollers and bottom stress on wave setup 1 setup the increase in the mean water level associated with breaking waves observed between the shoreline and about 6 m water depth on an ocean beach is predicted well by a model that includes the effects of wave rollers and the bottom stress owing to the mean flow over the 90 day observational period the measured and modeled setups are correlated squared correlation above 0 59 and agree within about 30 although rollers may affect setup significantly on beaches with large amplitude several meters high sandbars and may be important in predicting the details of the cross shore profile of setup for the data discussed here rollers have only a small effect on the amount of setup conversely bottom stress calculated using eddy viscosity and undertow formulations based on the surface dissipation and assuming that the eddy viscosity is uniform throughout the water column significantly affects setup predictions neglecting bottom stress results in underprediction of the observed setup in all water depths with maximum underprediction near the shoreline where the observed setup is largest

observations of sand bar evolution on a natural beach waves currents and the location of the seafloor were measured on a barred beach for about 2 months at nine locations along a cross shore transect extending 255 m from 1 to 4 m water depth the seafloor location was measured nearly continuously even in the surf zone during storms with sonar altimeters mounted on fixed frames the crest of a sand bar initially located about 60 m from the shoreline moved 130 m offshore primarily when the offshore significant wave height exceeded about 2 m with 1 5 m of erosion near the initial location and 1 m of accretion at the final location an energetics type sediment transport model driven by locally measured near bottom currents predicts the observed offshore bar migration but not the slow onshore migration observed during low energy wave conditions the predicted offshore bar migration is driven primarily by cross shore gradients in predicted suspended sediment transport associated with quasi steady near bottom offshore flows these strong 50 cm s currents intensified near the bar crest by wave breaking are predicted to cause erosion on the shoreward slope of the bar and deposition on the seaward side the feedback amoung morphology waves circulation and sediment transport thus forces offshore bar migration during storms

the bingham canyon porphyry cu mo au deposit iii zoned copper gold ore deposition by magmatic vapor expansion fluid inclusion microthermometry and laser ablation icpms microanalysis are combined with geological and textural observations to reconstruct the spatial and temporal evolution of magmatic fluids that formed the subvolcanic porphyry cu au mo ore deposit at bingham canyon utah the bingham canyon orebody is exposed over 1 6 km vertically and has the shape of an inverted cup with distinct metal zoning fluid inclusions in the barren but highly veined and potassically altered deep center of the system have intermediate density 0 6 g cm 3 and a salinity of 7 wt percent nacl equiv they have subequal concentrations of na k fe and cu and contain minor co2 the intermediate density fluids were trapped as a single phase mostly at 500 c and 800 bars the au cu rich center near the top of the orebody contains low density vapor inclusions 0 2 g cm 3 coexisting with brine inclusions containing 45 wt percent nacl equiv the vertical transition of different inclusion types indicates phase separation of the single phase input fluid upon volume expansion associated with a pressure drop to 200 100 bars mass balance calculation based on all analyzed inclusion components indicates that the mass of the vapor phase exceeded that of the brine by 9 1 the vapor contained cu as its dominant cation 1 5 wt and contributed about 95 percent of the total amount of copper transported to the base of the orebody bornite chalcopyrite and native gold were precipitated in a narrow temperature interval from 430 to 350 c into secondary pore space created by local redissolution of vein quartz as a result of retrograde quartz solubility in the vapor dominated fluid system intermediate density fluid inclusions in the deepest parts of the peripheral copper ore zone have identical density and composition including similar gold contents as those in the deep center microthermometry and statistical estimation of phase proportions in the inclusions show that the vapor in the peripheral cu rich but au poor ore zone remained denser and the separating brine was less saline 36 wt nacl equiv compared to vapor and brine in the central au cu ore zone this indicates that the peripheral fluids experienced a lower degree of phase separation due to slightly higher fluid pressure at equivalent temperature compared to more strongly expanding fluids in the center of the system the systematic zoning of au cu within the ore shell despite compositionally similar input fluids is interpreted to have resulted from slightly different pressure temperature density evolution paths of magmatic fluids copper was selectively precipitated in the peripheral ore zone in contrast to complete coprecipitation of au and cu in the central upflow zone of the vapor plume the formation of particularly rich cu au ore in the center of the upward expanding fluid plume is consistent with published experimental data showing that the solubility of metals in hydrous vapor decreases sharply with falling pressure due to destabilization of the hydration shell around metal complexes in expanding vapor this interpretation supports the classic vapor plume model for porphyry copper ore formation but additionally emphasizes the role of sulfur bearing complexes as a key chemical control on magmatic hydrothermal metal transport and the deposition of cu and au in porphyry ores our interpretation of selective cu au precipitation as a function of vapor density can explain the more general observation that most gold rich porphyry copper deposits are formed in shallow sub volcanic environments whereas deeper seated porphyry cu mo deposits are generally gold poor

bar trough generation on a natural beach mechanisms for bar trough generation are examined using velocities measured in the field applied to the bowen 1980 bailard 1981 energetics based sediment transport model measurements consist of a cross shore array of nine electromagnetic current meters spanning the surf zone and daily bathymetric surveys during a 10 day period during which two storms occurred when the bathymetry evolved from a three dimensional terrace to a well developed linear bar the model predicts bed and suspended load transport separately based on various velocity moments the velocities are partitioned into mean currents low frequency infragravity and shear instabilities 0 05 hz to determine the relative importance of various mechanisms to the total transport velocity moments are computed over 90 min intervals to resolve tidal fluctuations tidal signatures were apparent in all modes of transport predicted transport rates are integrated and compared with daily cross shore bathymetric profiles averaged over a 400 m length of beach the suspended load terms were an order of magnitude greater than bed load terms owing to the low fall velocity of the fine grain sand within the surf zone model results for this experiment indicate the dominant mechanism for bar development was sediments mobilized by the strong longshore current and incident short waves within the surf zone and transported offshore by the mean undertow and shoreward transport onshore due to short wave velocity skewness using standard coefficients the model correctly predicted the first order movement of the bar during storms but underpredicted trough development and did not always perform well during mild wave conditions

undertow over a barred beach the spatial distribution of the mean cross shore flow undertow over a barred beach is examined with field data obtained on three energetic wave days during the duck94 experiment the vertical structure of the undertow is modeled using a turbulent eddy viscosity closure and includes the important effects of wave breaking described using the roller concept and convective acceleration of the current other than a more realistic description of observed turbulence variations a depth dependent eddy viscosity compared with a constant does not improve the agreement between predicted and observed undertow profiles the effect of using different boundary conditions is investigated by extending the formulations of stive and wind 1986 and svendsen et al 1987 to include random waves by ensemble averaging over the wave height distribution the contribution of breaking wave rollers to the surface mass flux can be of the same order or greater than the contribution associated with the organized wave motion the largest discrepancies between model predictions and observations occur over the sandbar where the mass transport of the breaking waves appears to be underestimated

discussion on au transportation mechanism in melt magma fluid in porphyry cu deposit a case study from jinchang porphyry au cu deposit heilongjiang province china abstract at present there are au in most porphyry type copper deposits and there are also many reserves of au resources there are 11 porphyry type cu deposits with au resources greater than 500 t as of 2010 previous studies on the source migration and mineralization of cu s and cl in porphyry type cu deposits were relatively thorough but au was rarely involved especially since geologists recognized the genetic relationship of hydrothermal gold deposits and porphyry copper deposits here we proposed the mechanism of the au source transport and storage in jinchang porphyry au cu deposit located in the easternmost portion of the central asian orogenic belt in china the gold bearing characteristics and au chemical properties of siegenite show that in the initial magmatic environment with high oxygen fugacity au enters the melt phase from the solid phase with au0 oxidized to au3 the ni3 and co3 ions have similar chemical properties thus migrate together in the melt phase the gold bearing siegenite provides strong evidence for the affinity and elemental replacement of au3 and ni3 the symbiosis and differentiation mechanisms of rare earth elements also provide evidence for the affinity and differentiation mechanism between au3 and ni3 after the au3 melt undergoes the initial magma evolution to the magma chamber the oxygen fugacity of the melt phase is reduced to a certain degree during the crystallization and separation of the magma which causes the au3 in the ore forming elements to be reduced to au1 and enter the fluid phase au1 is dissolved in the fluid phase and enriched gradually as the temperature pressure and oxygen fugacity further decrease then au1 is reduced to au0 and precipitates to form native gold in porphyry or quartz veins

field observations of wave driven setdown and setup wave driven setdown and setup observed for 3 months on a cross shore transect between the shoreline and 5 m water depth on a barred beach are compared with a theoretical balance between cross shore gradients of the mean water level and the wave radiation stress the observed setdown the depression of the mean water level seaward of the surf zone is predicted well when radiation stress gradients are estimated from the observations using linear theory at each location along the transect the observed setdown also agrees with analytical predictions based on offshore wave observations and the assumption of linear dissipationless normally incident waves shoaling on alongshore homogeneous bathymetry the observed setup the superelevation of the mean water level owing to wave breaking is predicted accurately in the outer and middle surf zone but is increasingly underpredicted as the shoreline is approached similar to previous field studies setup at a fixed cross shore location increases with increasing offshore wave height and is sensitive to tidal fluctuations in the local water depth and to bathymetric changes numerical simulations and the observations suggest that setup near the shoreline depends on the bathymetry of the entire surf zone and increases with decreasing surf zone beach slope defined as the ratio of the surf zone averaged water depth to the surf zone width a new empirical formula for shoreline setup on nonplanar beaches incorporates this dependence

a study of radiation stress and set up in the nearshore region abstract in this paper the variations of radiation stress and mean water level are studied for the two dimensional shoaling and breaking of progressive periodic waves on a plane gently sloping laboratory beach observations of radiation stress and mean water level were made for two initial conditions the observed variations are compared to the variations as calculated by a linear theory james nonlinear theory and a new nonlinear theory based on cokelet s work it is shown that the nonlinear theories are qualitatively and quantitatively superior to the linear theory thus indicating that the effects of finite amplitude are important for the present case

a note on the three dimensional shear stress distribution in a surf zone the three dimensional time mean shear stress distribution in a surf zone is analyzed thereby determining the vertical distribution of the driving forces due to wave breaking it is found that on a uniform coast the longshore current can be described as driven by a surface shear stress equal to the cross shore gradient in the shear component of the radiation stress the near surface shear stress is found to be in the direction of wave propagation having a magnitude determined by the dissipation of wave energy it can be determined as the shear force acting on the waves from the surface rollers of spilling breakers or broken waves

modeling the solubility of sulfur in magmas a 50 year old geochemical challenge there are myriad reasons why we wish to understand the behavior of sulfur in magmatic systems reasons that vary from pure intellectual curiosity to possible impacts on society and its resources since ancient times sulfur has been associated with volcanic activity and the role of sulfur in the formation of ore deposits has long been recognized because of the necessity of metal ores for our modern life style e g barnes 1979 naldrett 1989 simon and ripley 2011 this volume recently the mechanisms and quantities of sulfur freed from natural magmas have become an important environmental issue due to their potential effects on global climate change for example the average annual volcanic so2 emission rate of 7 5 to 10 5 teragrams tg per year halmer et al 2002 may contribute 10 of the global atmospheric sulfur input halmer et al 2002 smith et al 2004 and individual eruptive episodes can rapidly contribute gigantic sulfur loads to the atmosphere 100 s to 1000 s of tg depending on the scale of the eruption self 2006 such sulfur emissions can produce potentially catastrophic local and global changes e g fedele et al 2003 ward 2009 courtillot and rennes 2003 correlated the timing of flood basalts with extinction events in earth s history and hypothesized a causal relation part of the kill mechanism responsible for extinction may be volcanically derived sulfur creating anoxic oceans and another part of the mechanism may be climatic changes brought about by sulfur injection into the atmosphere ward 2009 indeed erwin 2006 advocates that sulfur released from the eruption of the siberian flood basalts played a role in the end permian extinction in light of the evidence that volcanic degassing is a significant source of sulfur to the atmosphere stoiber et al 1987 symonds et al 1994 andres

vertical flow structure during sandy duck observations and modeling abstract observations of the vertical distribution of time averaged cross shore and alongshore flows during the sandy duck field experiment are compared with model predictions to assess the parameters governing the flow behaviour the measurements were obtained with a vertical stack of eight two component current meters with the lowest and highest sensor at respectively o 0 1 and o 2 7 m above the bed observations under breaking wave conditions within the surfzone show that the maximum return flow velocities occur in the lower part of the water column consistent with laboratory observations under non breaking conditions outside the surfzone the maximum return flow velocities are observed closer to the water surface again in line with laboratory results analogous to previous observations the measured longshore current velocity profiles are logarithmic under non breaking conditions and become more depth uniform under breaking conditions the model description of the vertical structure of the flow includes the presence of wind stresses wave stresses pressure gradients turbulent eddy viscosity and a wave boundary layer the model utilizes parabolic shape functions to describe the vertical distribution of the turbulent eddy viscosity in the middle layer and within the bottom boundary layer eddy viscosity is enhanced in regions where turbulence is produced i e near the surface in the case of breaking waves and within the bottom boundary layer estimates of the wave breaking induced turbulent eddy viscosity and bottom friction are obtained by minimizing the model measurement discrepancies predictions utilizing calibrated expressions for both the turbulent eddy viscosity and bottom friction are in general agreement with the observations provided the wave transformation and associated mass flux are modeled correctly and a parabolic eddy viscosity distribution is used using a piecewise constant eddy viscosity distribution generally results in a degrading of the agreement between measurements and model results

giant ore deposits formed by optimal alignments and combinations of geological processes giant ore deposits are priority targets for mining companies a review of the characteristics of several giant porphyry and epithermal deposits worldwide suggests that they formed from ordinary processes that were fortuitously operating at maximum efficiency

porphyry copper deposit formation by sub volcanic sulphur dioxide flux and chemisorption the processes that create economic grade accumulations of metals above magma chambers are unclear high temperature laboratory experiments show that rapid reactions between magmatic gases and earth s crust can trigger efficient metal deposition

identification of intense intermittent coherent motions under shoaling and breaking waves laboratory measurements of the instantaneous horizontal and vertical turbulent velocities u and w induced by regular waves spilling on a rough impermeable slope were analyzed to elucidate the nature of turbulence generated in the bottom boundary layer and by wave breaking the analyses focused on the instantaneous turbulent events such as the absolute shear stress u w and turbulent kinetic energy k u 2 w 2 2 below trough level inside the surf zone the horizontal and vertical velocity records showed intense intermittent turbulent events that did not occur with the passing of each wave and the instantaneous quantities of and k could not be explained in terms of the phase averaged quantities the intermittent turbulent events extended into the bottom boundary layer inside the surf zone and in this region the infrequent but intense turbulence generated by wave breaking was an order of magnitude larger than the turbulence generated locally at the boundary two techniques were used to analyze the turbulent motions a quadrant analysis technique showed that although the large turbulent motions did not occur with each wave they were phase dependent near trough level and less so near the bottom a conditional sampling technique quantified the intensity and duration of the turbulent motions indicating that coherent events intense events occurred for 10 2 of the record and accounted for approximately 50 20 of the turbulent motion it is likely that the exactitude of these statistics will differ depending on breaker type nevertheless these statistics indicated that large turbulent motions are infrequent but contribute significantly to the turbulence intensity and possibly the suspension of bottom sediments

kerogen maturation in a reference kerogen type ii series the toarcian shales of the hils syncline nw germany abstract studies on the generation and migration of petroleum in the reference type ii source rocks of the hils syncline were published some years ago by rullkotter et al 1988 and leythaeuser et al 1988 in the present study kerogens of these reference samples ranging from 0 48 to 1 45 vitrinite reflectance r o were isolated and analysed after having confirmed their similarity with the toarcian shales of the paris basin series an immature kerogen of this latter series was added to the german natural series this same kerogen was heated in sealed gold tubes at various temperatures for one day these two series of kerogens allowed us to follow the thermal maturation both under natural and artificial conditions and to compare them to find common maturation parameters comparison of samples relies both on bulk analyses of kerogens and on molecular analyses of their thermal degradation products bulk analyses comprise elemental analysis 13 c nmr spectroscopy and rock eval pyrolysis molecular analyses are based on mass balance of saturated and aromatic hydrocarbons in extracts and structural analyses of saturated hydrocarbons by gas chromatography and mass spectrometry these analyses show that the evolution of the natural series is adequately reproduced by the heated samples the latter having the advantage of recovering all the compounds formed during kerogen maturation from methane to coke without losses during sampling or by migration phenomena as in natural samples

wave transformation across the inner surf zone sea and swell wave heights observed on transects crossing the mid and inner surf zone on three beaches a steep concave up beach a gently sloped approximately planar beach and a beach with an approximately flat terrace adjacent to a steep foreshore were depth limited i e approximately independent of the offshore wave height consistent with previous observations the wave evolution is well predicted by a numerical model based on the one dimensional nonlinear shallow water equations with bore dissipation the model is initialized with the time series of sea surface elevation and cross shore current observed at the most offshore sensors located about 50 to 120 m from the mean shoreline in mean water depths 0 80 to 2 10 m the model accurately predicts the cross shore variation of energy at both infragravity nominally 0 004 f 0 05 hz and sea swell here 0 05 f 0 18 hz frequencies in models of surf zone hydrodynamics wave energy dissipation is frequently parameterized in terms of s the ratio of the sea swell significant wave height to the local mean water depth the observed and predicted values of s increase with increasing beach slope and decreasing normalized by a characteristic wavenumber k water depth kh and are well correlated with kh a measure of the fractional change in water depth over a wavelength errors in the predicted individual values of s are typically less than 20 it has been suggested that infragravity motions affect waves in the sea swell band and hence s but this speculation is difficult to test with field observations numerical simulations suggest that for the range of conditions considered here s is insensitive to infragravity energy levels

fluid inclusions from the jinchang cu au deposit heilongjiang province ne china genetic style and magmatic hydrothermal evolution abstract the jinchang cu au deposit is located in the easternmost part of the central asian orogenic belt caob the mineralization here is associated with cretaceous porphyritic intrusions of ca 120 110 ma and is mainly hosted within intensely altered mesozoic granites breccia pipes ringed and radial faults the gold ores are disseminated in the wall rock and also occur as massive auriferous quartz sulfide veins in fractures and breccias fluid inclusion data from breccias chalcopyrite quartz vein and pyrite quartz vein display homogenization temperatures in the range of 200 to 550 c and the fluids show variable salinity in the range of 0 58 wt nacl equiv the halite absent fluid inclusions shows a slight increase in salinity with a sharp decrease in temperature we interpret that the high salinity brine and low salinity vapor or aqueous rich fluids from ores represent fluid unmixing from magma the fluid inclusion data from jinchang demonstrate that the main mineralization took place at temperatures from 480 c to 200 c and evolved from high to low salinities geology and fluid inclusion data suggest that the jinchang deposit is an oxidized intrusion related cu au deposit the voluminous hydrothermal magnetite formed during high temperature potassic alteration of wall rocks in this ore deposit can be used as a potential prospecting tool

zircon ce4 ce3 ratios and ages for yulong ore bearing porphyries in eastern tibet yulong ore bearing porphyries along the northwestern extension of the red river ailao shan fault system in eastern tibet consist of five porphyry deposits containing a total of more than 8 million tons of copper resources u th pb laser inductively coupled plasma mass spectrometry dating of zircon shows that the porphyries were emplaced in early tertiary 41 2 36 9 ma covering a period of 4 3 ma with formation ages decreasing systematically from northwest to southeast the start of porphyry magmatism coincided with the onset of transpressional movement along the red river ailao shan fault system implying a close link between these two events age sequence in intrusions can be plausibly explained by assuming that a region of melting in the lower northwestern plate moved southeasternward along the tuoba mangkang fault relative to the upper plate zircon grains from the yulong ore bearing porphyries have higher ce4 ce3 than those from barren porphyries in the region this suggests that the ore bearing porphyries crystallized from a relatively oxidized magma which has important implications for future ore exploration in the region and other cu deposits in convergent margin environments in general

a laboratory study of longshore currents over barred and non barred beaches abstract a detailed description is given of the results of laboratory experiments on wave driven longshore currents on both barred and non barred beaches the objective is to examine the cross shore distribution of the longshore current velocities for purely wave driven currents with emphasis on the position of maximum current velocity with respect to areas where wave energy is dissipated unidirectional obliquely incident waves both regular and random were used the measurements were performed in a large wave basin with a pump recirculation system to create spatially homogeneous longshore currents the experiments yielded information on wave transformation set up of the mean water level and the cross shore distribution of wave driven longshore current velocity a number of cases are presented and compared with each other the measurements show that in the case of purely wave driven longshore currents the maximum current velocities occur close to areas where wave breaking is most intense the effect of mixing bottom friction and wave rollers on the longshore current velocity profile are examined in more detail with help of numerical modelling existing model equations based on the assumption of alongshore uniformity are used the results for the mean longshore current profile on a barred beach are in close agreement with the measurements

economic geology gold buried by oxygen he witwatersrand basin in south africa contains extraordinary amounts of gold thermodynamic calculations suggest that the gold may have accumulated there in response to a perfect storm of conditions available only during the archaean

spectral evolution of shoaling and breaking waves on a barred beach field observations and numerical model predictions are used to investigate the effects of nonlinear interactions reflection and dissipation on the evolution of surface gravity waves propagating across a barred beach nonlinear interactions resulted in a doubling of the number of wave crests when moderately energetic about 0 8 m significant wave height narrowband swell propagated without breaking across an 80 m wide nearly flat 2 m depth section of beach between a small offshore sand bar and a steep slope 0 1 beach face where the waves finally broke these nonlinear energy transfers are accurately predicted by a model based on the nondissipative unidirectional i e reflection is neglected boussinesq equations for a lower energy wave height about 0 4 m bimodal wave field high frequency seas dissipated in the surf zone but lower frequency swell partially reflected from the steep beach face resulting in significant cross shore modulation of swell energy the combined effects of reflection from the beach face and dissipation across the sand bar and near the shoreline are described well by a bore propagation model based on the nondispersive nonlinear shallow water equations boussinesq model predictions on the flat section where dissipation is weak are improved by decomposing the wave field into seaward and shoreward propagating components in more energetic wave heights greater than 1 m conditions reflection is negligible and the region of significant dissipation can extend well seaward of the sand bar differences between observed decreases in spectral levels and boussinesq model predictions of nonlinear energy transfers are used to infer the spectrum of breaking wave induced dissipation between adjacent measurement locations the inferred dissipation rates typically increase with increasing frequency and are comparable in magnitude to the nonlinear energy transfer rates

zircon compositional evidence for sulfur degassing from ore forming arc magmas porphyry cu mo au and epithermal au ag deposits are major sources of mined metals and are commonly formed by magmatic hydrothermal fluids derived from hydrous magmas in phanerozoic convergent margin settings the igneous rock assemblages associated with porphyry mineral deposits are common in modern convergent margin settings but while many have produced acidic magmatic fluids very few past or present have produced sufficient metal chlorine and sulfur enrichments necessary to engender an ore deposit the reasons for this remain uncertain we report shrimp rg ion microprobe analyses of hafnium titanium and rare earth element ree abundances in zircon a nearly ubiquitous and robust trace mineral in crustal magmas comparison of the compositions of zircons in ore forming and barren granitic plutons indicate that ore forming granites crystallized at relatively low temperature and have relatively small negative europium anomalies mostly eu n eu n 0 4 we interpret these small zircon europium anomalies to indicate oxidizing magmatic conditions and hypothesize that in many cases this reflects oxidation due to so 2 degassing from magmas with a relatively low fe s ratio oxidation of europium and iron in the melt is produced by reduction of magmatic sulfate s 6 to so 2 s 4 upon degassing this interpretation reinforces the important role of oxidized sulfur rich fluids in porphyry and epithermal mineral deposit formation zircon compositions thus may be used to identify ancient magmas that released significant amounts of so 2 rich gases and regional surveys of zircon composition are potentially a valuable tool for mineral exploration

giant porphyry deposits characteristics distribution and tectonic controls more than half of the 25 largest known porphyry copper deposits defined in terms of contained copper metal formed during three time periods the paleocene to eocene eocene to oligocene and middle miocene to pliocene these giant deposits are clustered within three provinces central chile northern chile and southwest arizona northern mexico other giant deposits occur in montana utah panama peru argentina irian jaya mongolia and iran compressive tectonic environments thickened continental crust and active uplift and erosion were associated with the formation of many of these deposits calc alkalic magmas are most favorable for the formation of giant porphyry copper deposits although several of the largest systems are associated with high k calc alkalic intrusions the 25 largest gold rich porphyry deposits are concentrated in the southwest pacific and south america with other occurrences in eurasia british columbia alaska and new south wales many of the deposits formed in the last 13 m y the largest of the deposits are associated with high k calc alkalic intrusions many calc alkalic porphyritic intrusions have also produced giant gold rich porphyries in the last 20 m y the formation of giant porphyry copper molybdenum and copper gold deposits in the circum pacific region has been closely associated with subduction of aseismic ridges seamount chains and oceanic plateaus beneath oceanic island and continental arcs in several examples these tectonic perturbations have promoted flat slab subduction crustal thickening uplift and erosion and adakitic magmatism coeval with the formation of well endowed porphyry and or epithermal mineral provinces similar tectonic features are inferred to be associated with the giant porphyry copper molybdenum provinces of northern chile eocene oligocene and southwest united states cretaceous paleocene topographic and thermal anomalies on the downgoing slab appear to act as tectonic triggers for porphyry ore formation other factors such as sutures in the overriding plate permeability architecture of the upper crust efficient processes of ore transport and deposition and in some cases formation and preservation of supergene enrichment blankets are also vital for the development of high grade giant ore deposits a low grade geochemical anomaly may be the final product of mineralization if ore forming processes do not operate efficiently even in the most favorable geodynamic settings

vertical profiles of longshore currents and related bed shear stress and bottom roughness the vertical structure of the mean wave driven longshore current over a barred beach is examined on three strong current days during the duck94 experiment and it is found that the bottom boundary layer is well described by a logarithmic profile mean correlation coefficient for all 22 profiles 0 98 the logarithmic profile fits better in the trough where turbulent bottom boundary layer processes predominate than over the bar where breaking wave induced turbulence generated at the surface modifies the profile the surface layer in the presence of waves is well described by adjusting the logarithmic profile for the intermittent presence of water and adding the alongshore component of the mass transport velocity slope of the least squares linear regression between model predictions and observations 1 005 and root mean square rms error of 7 bed shear stresses calculated from logarithmic velocity profiles are equated to a quadratic bottom shear stress formulation the associated bed shear stress coefficients vary by more than an order of magnitude across the surf zone 0 0006 0 012 bottom roughness was measured throughout the nearshore using a sonic altimeter mounted on a moving platform the bed shear stress coefficients are positively correlated with bottom roughness linear correlation coefficient 0 6 a higher linear correlation coefficient 0 8 is obtained by subtracting skin friction from the total bed shear stress

native gold and native copper grains enclosed by olivine phenocrysts in a picrite lava of the emeishan large igneous province sw china a native gold bleb found in an olivine phenocryst in a picrite lava from the emeishan large igneous province elip may be the first documented case of the transport of gold as a distinct precious metal phase in a mantle derived magma four picrite layers have been recognized in the lower part of the volcanic succession in the lijiang area in the western part of the elip the native gold bleb was found enclosed in an olivine phenocryst in the second picritic layer of a basalt picrite succession in the elip the gold bleb is spheroidal about 30 m in diameter consists of pure gold and does not contain any other elements in addition native copper grains were also discovered in the serpentinized olivine phenocrysts and native zinc and moissanite sic were separated from an 20 kg sample of picrite the paragenesis of these minerals suggests that the primary magmas were s unsaturated the native gold and native copper grains are considered to be xenocrysts from the mantle transported to shallow depths by a rising plume and then captured by the picritic melts the discovery of native gold and native copper grains provides direct evidence that the gold in the hydrothermal gold deposits and the native copper deposits in the elip lavas ultimately may be derived from a mantle plume

porphyry copper gold mineralization at yulong china promoted by decreasing redox potential during magnetite alteration the yulong porphyry cu au deposit occurs on the eastern margin of the tibetan plateau and is one of the largest porphyry cu au deposits in china containing more than 6 million tons of cu metal similar to other porphyry cu deposits in the world the yulong porphyry is highly oxidized sulfate is the dominant sulfur species in fluid inclusions hosted by magmatic quartz phenocrysts and no sulfide is observed indicating an oxygen fugacity above the sso buffer during magmatic processes the sulfur species changed from sulfate dominant during magmatic processes to sulfide dominant during the main mineralization processes with sulfate and sulfide mineral assemblages observed in fluid inclusions in mineralized quartz veinlets and only sulfides in the orebodies corresponding to a decrease in redox potential from the porphyry to the hydrothermal fluid magnetite crystallization was coincident with the onset of major sulfate reduction indicating that magnetite isolated trivalent iron reducing sulfate and consequently leading to the formation of porphyry cu au mineralization most porphyry cu au ore deposits are spatially associated with and genetically related to oxidized felsic magmas our results indicate that sulfate reduction promoted by magnetite crystallization is essential for the final precipitation of cu au bearing sulfides i e decreasing redox potential of the fluid is the key to and direct cause of ore formation in yulong initial high redox potential is a prerequisite for and may be an indirect indicator of most mineralization of this kind because it enables efficient transportation of cu au redox potential fluctuations can be well preserved in zircon a resistant accessory mineral commonly found in porphyries which might be developed as a handy and reliable exploration tool for porphyry cu deposits associated with magnetite

transport of metals and sulphur in magmas by flotation of sulphide melt on vapour bubbles emissions of sulphur 1 2 and transition metals 3 4 from magmas in the shallow crust have global impacts on human society by affecting climate after volcanic eruptions 5 6 and by forming giant copper and gold ore deposits which are massive anomalies of sulphur as well as of the ore metals themselves 3 4 7 8 these emissions vastly exceed the amounts that could have been derived from the associated magmas themselves 2 intrusion of denser hotter vapour and sulphide saturated magma beneath the cooler and more buoyant bodies that are finally erupted is the most probable source of the excess sulphur and metals in eruptive or hydrothermal systems 1 4 9 10 however the mechanism for the selective upward transfer of sulphur and metals remains poorly understood because their main carrier phase sulphide melt is dense and is generally assumed to settle to the bottoms of magma bodies here we show by experimental observation and by gas speciation and mass balance models that such transfers may be achieved by the flotation of compound drops 11 comprising droplets of sulphide melt attached to vapour bubbles by proposing and demonstrating the feasibility of a novel physical mechanism for upward mobility of sulphide liquids our work provides a mechanism for massive atmospheric releases of sulphur and contradicts widely held assumptions that dense sulphide liquids rich in sulphur copper and gold will remain sequestered in the crust

field observations of wave setup wave setup is assumed to be a balance between the cross shore convergence of the onshore flux of momentum wave radiation stress sxx in the surfzone and a cross shore pressure gradient oceanic observations between the 2 and 8 m isobaths near duck north carolina provide a test of the wave setup balance without assuming that wave height in the surfzone is proportional to water depth analysis of data from a cross shore array of 11 pressure gauges and 10 sonar altimeters deployed during the fall of 1994 indicates the wave setup balance holds to at least the accuracy of the pressure measurements a few centimeters the correlation between the two terms in the setup balance is 0 93 and the linear regression slope is 1 05 0 19 accurate estimates of the cross shore pressure gradient require density measurements to adjust pressure measurements taken at different depths to the same level the assumption that pressure and bathymetry are linear between the 2 and 8 m isobaths or the more common assumption that the height of normally incident shallow water waves is proportional to the water depth introduces errors of up to 6 cm for the conditions considered here given this assumption 3 5 years of data from pressure gauges in 2 and 8 m of water indicate that the wave setup balance is valid for a wide range of conditions correlation 0 71 and regression slope 0 98 0 08

magmatism and metallogeny associated with mantle upwelling zircon u pb and lu hf constraints from the gold mineralized jinchang granite ne china abstract the jinchang gold deposit is located in the easternmost portion of the central asian orogenic belt caob and represents one of the major gold districts in eastern jilin heilongjiang provinces of china the gold ore bodies are hosted mainly in altered mesozoic granitoids breccia pipes and ring and radial faults gold mineralization consists of alteration stockwork in hydrothermally altered granites breccia and quartz sulfide vein types alteration assemblages around the alteration style ore body show a vertical sequence of potassic phyllic and propylitic zones in this study we present u pb and lu hf isotope data on zircons derived from mineralized granophyric granite biotite monzogranite granodiorite and granite porphyry and sericite rb sr ages from the jinchang gold deposit the results show 206pb 238u ages of 201 3 ma mswd 1 1 203 4 ma mswd 1 4 201 5 ma mswd 2 1 and 110 3 ma mswd 1 6 respectively sericite from the gold mineralized phyllic altered granodiorite and granite porphyry returns rb sr isochron ages of 110 4 ma mswd 1 04 and 107 5 ma mswd 0 91 respectively our new data indicate that the gold mineralization at jinchang took place at ca 110 ma and was temporally related to intrusion of the granite porphyry zircon e hf 200 ma values of the ca 200 ma granites vary from 4 8 to 8 1 with tcdm model ages of 727 1535 ma reflecting their derivation mainly by partial melting of juvenile proterozoic crust the gold bearing 110 ma granite porphyry returns e hf 110 ma values in the range of 1 6 to 9 8 with tcdm model ages of 542 1069 ma suggesting partial melts of juvenile proterozoic crust with notable input of mantle components as compared to the ca 200 ma granites compiled oxygen 18osmow 0 7 10 1 and hydrogen dsmow 99 to 70 stable isotopic values of quartz from ores indicate that the ore forming fluids were predominantly exsolved from magmas with minor amount of meteoric water in quartz sulfide veins at the late stage the hf isotope data from the granite porphyry integrated with the results from previous data on s and pb isotopic composition of ores constrain the source of ore forming components as lower crust with discernible mantle inputs and wall rock assimilation our results have implications bearing on the widespread magmatism and metallogenic event during the early cretaceous time in east china and link them to mantle upwelling that contributed both heat and volatiles for crustal melting and scavenging of metals which in turn were concentrated in upper crustal levels through exsolution for the magmas

sulfur evolution of oxidized arc magmas as recorded in apatite from a porphyry copper batholith uniformly sulfur rich cores abruptly zoned to sulfur poor rims 1 to 0 2 wt so3 in apatite from the yerington batholith nevada indicate that early magma that is crystal poor oxidizing and sulfate rich evolved to sulfate poor magma via crystallization of anhydrite a mineral observed in magmas from pinatubo and el chichon we predict that the characteristic zonation to sulfur poor rims of apatite in the yerington batholith is common in other oxidized hydrous calc alkaline magmas and can be used to track cryptic anhydrite saturation as well as to monitor sulfur evolution sulfate rich arc magmas such as yerington magmas may crystallize to produce hydrothermal fluids rich in chlorine copper and sulfur and porphyry copper ores

re os isotopic and trace element compositions of pyrite and origin of the cretaceous jinchang porphyry cu au deposit heilongjiang province ne china abstract the jinchang cu au deposit in northeast china contains more than 76 tons of au and 4683 tons of cu with average ore grades of 11 34 g t au and 1 44 cu the deposit is typical of porphyry types and consists of gold orebodies mainly hosted in a 113 ma granitic porphyry and breccia pipes within the porphyry intrusion mineralization is closely associated with early potassic alteration and late phyllic alteration pyrite is the main au bearing mineral and contains 1 48 18 9 ppb re and 11 4 38 ppt common os extremely low common os concentrations and high re os ratios are indicative of derivation of ore forming materials from the crust low re in pyrite from the jinchang deposit may indicate a mixing source of mantle and crust or a crustal source five re os isotopic analyses yield a model 1 isochron age of 114 22 ma 2 mswd 0 15 similar to the age of the host porphyry pyrite contains detectable co ni cu zn as ag au sb pb and bi pyrite has co ni ratios similar to that of volcanogenic and hydrothermal sulfide deposits indicating a magmatic hydrothermal origin and has au and as contents similar to that of porphyry epithermal systems pyrite grains from potassic and phyllic alteration stages have different trace element contents reflecting the evolution of ore forming fluids from magmatic dominated to magmatic mixed with meteoric water in combination with regional geology our new results are suggestive of origin of the jinchang cu au deposit from contemporary intrusions of granitic porphyries related to the early cretaceous subduction of the paleo pacific plate

megaripple migration in a natural surf zone migrating megaripples are bedforms that appear in the surf zone of sandy coasts1 with heights of 0 1 0 5 m and wavelengths of 1 5 m they are similar in size and shape to small dunes large ripples or sand waves such sedimentary bedforms have been studied in subaerial2 steady flow3 and intertidal4 environments as well as in laboratory flume experiments5 they affect overlying currents by introducing hydraulic roughness4 6 and may provide a mechanism for sediment transport7 8 as well as forming sedimentary structures in preserved facies9 10 the formation orientation and migration of such bedforms is not understood well11 12 dunes for example can be aligned with their crests perpendicular to steady unidirectional winds13 but in more complex wind fields their orientation becomes difficult to predict14 15 16 17 similarly it is not known how sea floor megaripples become aligned and migrate in the complex flows of the surf zone here we present observations in the surf zone of a natural beach which indicate that megaripples do not migrate in the direction of the vector sum of the currents but are aligned so that the sediment transport normal to the bedform crest is maximized17 this may need to be taken into account in modelling morphology change and interpreting existing and fossil morphologic patterns

cross shore hydrodynamics within an unsaturated surf zone abstract this paper concerns the hydrodynamics induced by random waves incident on a steep beach new experimental results are presented on surface elevation and kinematic probability density functions cross shore variation in wave heights the fraction of broken waves and velocity moments the surf zone is found to be unsaturated at incident wave frequencies with a significant proportion of the incident wave energy remaining at the shoreline in the form of bores wave heights in both the outer and inner surf zones are best described by a full rayleigh distribution thornton e b guza r t 1983 transformation of wave height distribution j geophys res 88 5925 5938 rather than a truncated rayleigh distribution as used by battjes and janssen 1978 battjes j a janssen j p 1978 energy loss and setup due to breaking of random waves proc 16th int conf coastal eng asce new york pp 569 588 a new parametric wave transformation model is outlined which provides explicit expressions for the fraction of broken waves and the energy dissipation rate within the surf zone on steep beaches the model appears to offer improved predictive capabilities over the original battjes and janssen model cross shore variations in the velocity variance and velocity moments are best described using linear gaussian wave theory with less than 20 of the velocity variance in the inner surf zone due to low frequency energy

swash on a gently sloping beach waves observed in the inner surf and swash zones of a fine grained gently sloping beach are modeled accurately with the nonlinear shallow water equations the model is initialized with observations from pressure and current sensors collocated about 50 m from the mean shoreline in about i m depth and model predictions are compared to pressure fluctuations measured at five shoreward locations and to run up run up was measured with a vertical stack of five wires supported parallel to and above the beach face at elevations of 5 10 15 20 and 25 cm each 60 m long run up wire yields time series of the most shoreward location where the water depth exceeds the wire elevation as noted previously run up measurements are sensitive to the wire elevation owing to thin run up tongues not measured by the more elevated wires as the wire elevation increases the measured mean run up location moves seaward low frequency infragravity energy decreases and higher frequency sea swell energy increases these trends as well as the variation of wave spectra and shapes e g wave skewhess across the inner surf zone are well predicted by the numerical model

sulphide magma as a source of metals in arc related magmatic hydrothermal ore fluids as magma ascends in subduction zones decreasing pressure and temperature cause it to separate into two or more phases in a process known as exsolution hydrothermal ore fluids and metal rich sulphide melts may be products of this exsolution conventionally the ore fluids are thought to acquire their metal content directly from the parent magma however it is probable that the ore fluids and sulphide melts interact after exsolution and therefore possible that the sulphide melts are an important source of metals for the ore fluids here we use petrographic analyses of erupted sulphide melts and compositional analyses of volcanic gases emitted immediately after an eruption at merapi volcano indonesia to show that magmatic hydrothermal fluids can derive their metals from dissolution of sulphide melts we find that the volcanic gases exhibit metal ratios that are comparable to those in the erupted sulphide melts furthermore we show that gases sampled immediately after the eruption have metal concentrations that are orders of magnitude higher than those of gases emitted during periods of quiescence we propose that the metal content of ores forming in volcanic arc environments is established by exsolution accompanying injections of primitive magma immediately before explosive eruptions the metal content of ore deposits formed during subduction zone volcanism was thought to be established when the ore fluid separates from the parent magma analyses of metal concentrations in erupted melts and the volcanic gases emitted after an eruption in indonesia reveal that metals can be added to the ore fluid later during mixing with separated melts

the interaction between the undertow and the boundary layer flow on a beach the theoretical result for undertow in a surf zone found by svendsen 1984a is combined with a boundary layer solution at the bottom and it is shown that in this boundary layer the eddy viscosity is small relative to that produced by the breaking the proper eddy viscosity t between the surface and the bottom boundary layer is determined by comparison with measurements which leads to quite accurate reproduction of the velocity profiles the model also predicts the mean flow in the boundary layer and the mean bottom shear stress and the results are analyzed for sensitivity to inaccuracies in the basic assumptions

high sr y arc magmas and porphyry cu mo au deposits just add water porphyry cu mo au deposits are commonly associated with intermediate composition arc related igneous rocks with high sr y and la yb ratios and such rocks are equated by some researchers with melts derived from subducted oceanic crust undergoing eclogite facies metamorphism adakites however similar geochemical characteristics are readily developed in normal asthenospheric mantle wedge derived magmas by fractionation of amphibole and or garnet and or by interaction with crustal materials during ascent through the upper plate lithosphere while there is widespread evidence for such fractionation and contamination processes in porphyry magmas there is little direct evidence for an origin by slab melting the enhanced fertility of arc magmas relates primarily to their high water content which is required for the formation of magmatic hydrothermal systems upon shallow crustal emplacement magmatic water contents 4 wt percent h 2 o cause abundant amphibole garnet fractionation but suppression of plagioclase crystallization at deep crustal levels resulting in increasing sr y and la yb ratios with differentiation commonly into adakitic ranges but not reflecting slab melting additional factors that affect arc magma fertility are relatively high oxidation states and sulfur content but these are secondary to the requirement for sufficient water thus arc magmatic suites with high sr y ratios and evidence for the presence of hydrous phenocryst phases hornblende and or biotite are indeed prospective for porphyry cu mo au deposits but only because these parameters indicate high magmatic water content