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

platinum group minerals in the skouries cu au pd pt te porphyry deposit the skouries deposit is a platinum group element pge enriched cu au porphyry system located in the chalkidiki peninsula greece with associated ag bi and te enrichment the deposit is hosted by multiple porphyritic monzonite and syenite intrusions which originated from a magma chamber at depth an initial quartz monzonite porphyritic intrusion contains a quartz magnetite chalcopyrite pyrite vein stockwork with intense potassic alteration the quartz monzonite intrusion is cross cut by a set of syenite and mafic porphyry dykes and quartz chalcopyrite bornite magnetite veins which host the majority of the cu and au mineralisation late stage quartz pyrite veins with associated phyllic alteration crosscut all previous vein generations electron microprobe and scanning electron microscopy shows that the pge are hosted by platinum group minerals pgm in the quartz chalcopyrite bornite magnetite veins and within potassic alteration assemblages the pge mineralisation in skouries is therefore part of the main high temperature hypogene mineralisation event platinum group minerals at skouries include sopcheite ag4pd3te4 merenskyite pd pt te bi 2 and kotulskite pd te bi with rare telargpalite pd ag 3te isomertieite pd11sb2as2 naldrettite pd2sb testibiopalladite pdte sb te and sobolevskite pdbi the most common platinum group mineral is sopcheite the pgm in skouries are small 52 m2 on average and occur as spherical grains on the boundaries between sulphides and silicates and as inclusions within hydrothermal quartz and sulphides these observations support a semi metal collector model whereby an immiscible bi te melt acts as a collector for pge and other precious metals in high temperature hydrothermal fluids this mechanism would allow the formation of pgm in porphyries without pt and pd fluid saturation

residual mean solutions for the antarctic circumpolar current and its associated overturning circulation abstract residual mean theory is applied to the streamwise averaged antarctic circumpolar current to arrive at a concise description of the processes that set up its stratification and meridional overturning circulation on an f plane simple solutions are found in which transfer by geostrophic eddies colludes with applied winds and buoyancy fluxes to determine the depth and stratification of the thermocline and the pattern of associated residual meridional overturning circulation

dawsonite formation in the beier sag hailar basin ne china tuff a natural analog for mineral carbon storage abstract we determined the rock types the authigenic minerals the paragenetic sequence and the origin of dawsonite in pyroclastic rocks from the yimin formation of beier sag in the hailar basin china dawsonite a diagenetic mineral is thought to result from a large influx of co 2 and therefore this system represents a natural analogue for in situ mineral carbon storage the studied host rocks are mainly tuffs tuffaceous sandstones which now contain up to 70 vol authigenic carbonates including dawsonite ankerite and siderite the initial alteration of the tuffs yielded minor siderite kaolinite illite and mixed illite smectite then formed as product phases dawsonite and quartz subsequently precipitated in response to co 2 influx apparently coupled to feldspar and perhaps kaolinte dissolution dawsonite reaches a maximum 25 vol of the bulk rock mass balance suggests that this co 2 influx was coupled to the external import of sodium and export of sio 2 ankerite and additional siderite precipitated during the late stage alkaline diagenesis the carbon isotope values of the dawsonite are in the range 4 1 to 2 2 indicating the magmatic origin of the co 2 vitrinite reflectance and thermal gradient constraints suggest that the dawsonite at this location formed at a temperature of 75 c

fluid inclusions reviews in mineralogy vol 12 edwin roedder 1984 mineralogical society of america 644 p u s 14

fayalite dissolution and siderite formation in water saturated supercritical co2 abstract olivines significant constituents of basaltic rocks have the potential to immobilize permanently co2 after it is injected in the deep subsurface due to carbonation reactions occurring between co2 and the host rock to investigate the reactions of fayalitic olivine with supercritical co2 scco2 and formation of mineral carbonates experiments were conducted at temperatures of 35 c to 80 c 90 atm pressure and anoxic conditions for every temperature the dissolution of fayalite was examined both in the presence of liquid water and h2o saturated scco2 the experiments were conducted in a high pressure batch reactor at reaction time extending up to 85 days the newly formed products were characterized using a comprehensive suite of bulk and surface characterization techniques x ray diffraction transmission emission mossbauer spectroscopy scanning electron microscopy coupled with focused ion beam and high resolution transmission electron microscopy siderite with rhombohedral morphology was formed at 35 c 50 c and 80 c in the presence of liquid water and scco2 in h2o saturated scco2 the formation of siderite was confirmed only at high temperature 80 c characterization of reacted samples in h2o saturated scco2 with high resolution tem indicated that siderite formation initiated inside voids created during the initial steps of fayalite dissolution later stages of fayalite dissolution result in formation of siderite in layered vertical structures columns or pyramids with a rhombus base morphology

adjusting internal model errors through ocean state estimation abstract oceanic state estimation is a powerful tool to estimate internal model parameters simultaneously with the model s initial conditions and surface forcing field that jointly would bring a model into consistency with time varying large scale ocean observations here an attempt to estimate geographically varying fields of horizontal and vertical viscosity and diffusivity within a 9 yr long estimation procedure is presented the estimated coefficients are highly efficient in preserving watermass characteristics and frontal structures by reducing the model temperature and salinity drift especially around the southern ocean the estimated mean circulation results in stronger transports of western boundary currents and of the antarctic circumpolar current moreover an increase of about 10 in the strength of the meridional overturning circulation and in the poleward heat transport can be found estimated changes in the horizontal mixing coefficients seem to agree with the notion that diapycnal mixing i

application of high resolution x ray computed tomography to mineral deposit origin evaluation and processing abstract high resolution x ray computed tomography ct is the industrial equivalent of medical cat scanning and provides a mechanism for non destructive studies of the three dimensional nature of geological materials hrxct produces two dimensional images slices that reveal the interior of an object as if it had been sliced open along the image plane for viewing a ct image is generated by differences in x ray attenuation that arise from differences in density and composition within the object by acquiring a contiguous set of slices volumetric data for all or part of a sample can be obtained allowing three dimensional inspection and measurement of features of interest ct is particularly effective in the study of metallic ores that commonly contain minerals spanning the range of densities of natural materials available software can produce grain shape size and orientation data from the scanned volume which can be particularly useful for oriented samples ct is particularly useful for studies of gold and other precious metal bearing minerals that typically have significant contrast even with common metallic mineral phases ct precisely defines the in situ location of mineral grains of interest within a sample which then can be studied in conventional petrographic sections and other forms of data collected e g isotope or trace element geochemistry another area of application is fluid inclusions which can be discerned even in opaque phases and fluid and vapor volumes measured for sufficiently large occurrences we summarize ct principles and review available instrumentation as well as scanning and data reduction protocols that provide unique three dimensional information for diverse ore types and applications in mineral deposits geology ct applications for economic geology and other fields will continue to expand as instruments continue to evolve and as scanning protocols and applications are extended for more precise quantification of three dimensional relationships particularly for fine grained particles and small fluid inclusions in larger volumes and for separation of minerals with limited contrast

experimental determination of the effect of dissolved co2 on the dissolution kinetics of mg and ca silicates at 25 c dissolution rates of diopside forsterite fo100 and fo92 wollastonite and hornblende were measured at 25 c in nacl solutions as a function of ph 1 ph 12 pco2 0 and 1 atm and activity of hco3 and co32 10 5 co2 0 1 m dissolution rates of diopside forsterite and horneblende are not affected within the experimental uncertainty by 1 atm pco2 at ph 4 and by the presence of bicarbonate up to 0 1 m and carbonate up to 0 01 m ions at ph of 8 and 11 12 respectively although wollastonite dissolution rates are unaffected by pco2 at ph 4 its rates are increased by the presence of hco3 at 0 01 hco3 0 1 m and ph 7 8 and decreased slightly by co32 at co32 0 0001 m and ph 12 these results should be useful for modeling the effect of silicate rock weathering on the global biogeochemical cycle of carbon for the first time we were able to distinguish the net effect of pco2 versus that of ph it is observed in general accord with previous results that the direct effect of co2 on basic silicates dissolution rates is very weak as a result the major parameter governing basic silicates dissolution is ph of soil solutions in contact with minerals

treating strong adjoint sensitivities in tropical eddy permitting variational data assimilation a variational data assimilation system has been implemented for the tropical pacific ocean using an eddy permitting regional implementation of the mitgcm the adjoint assimilation system was developed by the estimation of the circulation and the climate of the ocean consortium and has been extended to deal with open boundaries this system is used to adjust the model to match observations in the tropical pacific region using control parameters which include initial conditions open boundaries and time dependent surface fluxes this paper focuses on problems related to strong adjoint sensitivities that may impede the model fit to the observations a decomposition of the velocities at the open boundaries into barotropic and baroclinic modes is introduced to deal with very strong sensitivities of the model sea surface height to the barotropic component of the inflow increased viscosity and diffusivity terms are used in the adjoint model to reduce exponentially growing sensitivities in the backward run associated with nonlinearity of the forward model simplified experiments in which the model was constrained with levitus temperature and salinity data reynolds sea surface temperature data and topex poseidon altimeter data were performed to demonstrate the controllability of this assimilation system and to study its sensitivity to the starting guesses for forcing and initial conditions

platinum group elements in ores from the kalmakyr porphyry cu au mo deposit uzbekistan bulk geochemical and laser ablation icp ms data we studied primary ore samples from kalmakyr a giant cu au mo porphyry deposit in eastern uzbekistan disseminated and stockwork type high grade cu au mo mineralization showed average concentrations of 55 ppb pd 5 5 ppb pt 0 95 ppb rh 0 49 ppb ir and 4 1 ppm au n 8 this type of mineralization is characterized by the presence of pyrite chalcopyrite molybdenite and gold a peak pd content of 292 ppb was determined in a base metal rich quartz vein in granodiorite porphyry which contains galena sphalerite chalcopyrite tetrahedrite and gold palladium correlates with cu ag se and s mineralogical and laser ablation icp ms study confirmed that pd is homogeneously distributed in chalcopyrite which contains up to 110 ppm pd and tetrahedrite containing up to 20 ppm pd an assessment of the pd and pt budget at kalmakyr showed the potential of approximately 17 t of pd and 1 7 t of pt

pliocene cu au bearing igneous intrusions of the gunung bijih ertsberg district irian jaya indonesia k ar geochronology nine distinct potassic intermediate igneous bodies have been identified during detailed surface and underground mapping of 100 km 2 in the gunung bijih erstberg cu au district in the highlands of irian jaya indonesia west new guinea fourteen biotite k ar ages range from 2 6 to 3 8 ma while another from a small isolated pluton is distinctly older at 4 4 ma these ages represent times of intrusion and crystallization which followed regional kilometer scale folding that resulted from collision at a subduction zone of the northern edge of the australian continental margin with the melanesian oceanic island arc complex the grasberg and ertsberg intrusions are cut by numerous faults with only minor hundreds of meters offset throughout the island of new guinea dated neogene igneous rocks form two clusters separated in age and location a distinct belt of miocene 20 10 ma plutons maramuni arc stretches the entire length of the northern highlands of papua new guinea and recurs in western iri

genesis of pyrite au as zn bi te zones associated with cu au skarns evidence from the big gossan and wanagon gold deposits ertsberg district papua indonesia the ertsberg district hosts multiple skarn and porphyry related deposits which together comprise one of the largest cu au resources in the world earlier skarn cu au deposits at big gossan and 2 km along strike to the northwest at wanagon gold are overprinted by distinctive late stage pyrite sphalerite arsenopyrite and native gold with local bi and te minerals the wanagon gold deposit contains an estimated 2 million ounces moz of gold reserves at big gossan are 33 million tonnes mt at 2 63 percent cu 0 92 g t au and 15 72 g t ag phlogopite from the big gossan occurrence is younger than 2 82 0 04 ma based on a new 40ar 39ar age from the big gossan skarn and k feldspar from the wanagon gold deposit has a 40ar 39ar age of 3 62 0 05 ma a k ar date 3 81 0 06 ma from the wanagon sill constrains formation of the overprinting skarn cu au and late stage wanagon gold deposit to a period of ca 0 2 m y at big gossan earlier skarn cu au mineralization displays three dimensional mineralogical chemical and temperature zonation the high temperature core defined by low zn cu plunges to the northwest and is open at depth highest cu grades and greatest development of the overprinting pyrite au as zn bi te association occur to the northwest coincident with northeast striking faults pyrite au as zn bi te occurrences are also distributed in faults and fractures to the north and south of the big gossan skarn cu au deposit at wanagon gold leaching of skarn and sandstone preceded introduction of the pyrite au as zn bi te occurrences in the sandstone the pyrite au as zn bi te mineralization was accompanied by k feldspar adularia and minor quartz gangue in carbonate rocks no leaching or secondary k feldspar is apparent instead sulfides are accompanied by quartz and dolomite gangue the delta 34s of sulfide from skarn cu au and overprinting pyrite au as zn bi te occurrences at both deposits range from 0 7 to 5 1 per mil laser ablation inductively coupled plasma mass spectrometry la icpms analyses show that later pyrite overprinting both occurrences is distinct from that in the earlier skarn cu au deposits and contains up to 60 ppm au 2 percent as 680 ppm bi and 40 ppm te the mineralogy of the overprinting occurrences includes native gold argentian tetrahedrite and tennantite a silver antimony sulfide and bi and te ag au minerals including cosalite bismuthinite petzite hessite altaite and tetradymite the fineness of native gold varies with sulfide association the lowest fineness gold 737 863 occurs with pb minerals galena and sulfosalts and the higher fineness gold 904 974 occurs trapped within pyrite or in association with bismuthinite fluid inclusions in sphalerite and quartz in the big gossan pyrite au as zn bi te occurrence have an average salinity of 8 wt percent nacl equiv and an average homogenization temperature of 245 c stable isotopes indicate that the inclusion fluids were magmatic however a direct genetic relationship to earlier skarn cu au mineralization is not obvious the pyrite au as zn bi te occurrences are considered to have formed from a fluid with a different composition possibly the magmatic precursor to fluids commonly recognized in low and high sulfidation epithermal deposits that develops at shallow levels and contains significant nonmagmatic i e meteoric water

precious metals assemblages at the mikheevskoe porphyry copper deposit south urals russia as proxies of epithermal overprinting abstract mineral assemblages and formation conditions of precious metals au ag pge in ores of the mikheevskoe porphyry copper deposit south urals are the subject of our study three mineralization types can be distinguished 1 gold silver telluride mineralization overlapping porphyry style bornite chalcopyrite ores includes native gold fineness 863 873 electrum fineness 593 672 galena hessite coloradoite and more rarely petzite stutzite au ag ditellurides native tellurium tellurobismuthite tetradymite kawazulite altaite and extremely rare melonite nite2 merenskyite pdte2 and sopcheite ag4pd3te4 2 gold arsenopyrite base metal mineralization within quartz tetrahedrite sphalerite veinlets cutting porphyry style mineralization 3 gold telluride mineralization with argillic alteration and mineralogically similar to that of type 1 but distinct because of the presence of au ag ag and pb selenides textural relationships supported by fluid inclusions data and chlorite geothermometry provide evidence that occurrence of precious metals minerals at the mikheevskoe deposit is mostly linked to epithermal overprint of the porphyry mineralization and was deposited at ca 300 200 c from moderately saline fluids ca 5 10 wt eq nacl it is suggested that the observed variability in au and ag minerals results from small fluctuations of s2 and or te2 fugacity

experimental evaluation of mixed fluid reactions between supercritical carbon dioxide and nacl brine relevance to the integrity of a geologic carbon repository abstract the reactive behavior of a mixed fluid supercritical co2 and brine under physical chemical conditions relevant to geologic storage and sequestration in a carbon repository is largely unknown experiments were conducted in a flexible cell hydrothermal apparatus to evaluate fluid rock aquifer plus aquitard reactions that may adversely impact the integrity of the repository a 5 5 molal nacl brine rock system was held at 200 c and 200 bars 20 mpa for 32 days 772 h to approach steady state then injected with co2 and allowed to react for an additional 45 days 1079 h in a separate experiment at 200 c and 200 bars the system was allowed to react for 77 days 1845 h without injection of co2 corroded magnesite and euhedral siderite crystallized in a paragenetic sequence after co2 injection nucleation and growth of siderite on shale suggests the aquitard is a reactive component in the system changes in elemental abundances in the brine following addition of co2 include ph decrease and depletion of sodium due to accelerated growth of analcime a ph increase follows pressure and temperature decrease and loss of saturated co2 from acidic brine silica concentrations and dissolution rates are enhanced and silica precipitation inhibited in the acidic brine geochemical reactions in a carbon repository extend beyond ph decrease and carbonate mineral precipitation rock dominated reaction systems yield to acid dominated and related reactions controlled by mixed fluid equilibria i e a fluid dominated system escape of co2 or migration of brine from the repository into overlying aquifers may cause silica super saturation and increased alkalinity due to mixed fluid phase equilibria these geochemical changes could be monitored in aquifers as indicators of repository integrity return of silica super saturated brine to a rock dominated reaction system buffered to neutral ph conditions may enhance precipitation of quartz chalcedony or amorphous silica in addition to the potential effects beneficial or deleterious that silica super saturation and precipitation may hold for repository performance an understanding of the effects of multi phase equilibrium relationships between supercritical co2 and dissolved silica in aquifer brine systems also raises new questions for a variety of geologic systems multi phase fluid equilibria may for example account for quartz cements in some sedimentary basin sandstones and quartz vein mineralization in some ore districts

experimental and modeling study of the interaction between a crushed marl caprock and co 2 rich solutions under different pressure and temperature conditions abstract carbon storage is regarded as a potential technology to reduce co 2 emissions this study is concerned with co 2 storage in a reservoir rock limestone which is a deep saline aquifer containing a nacl and sulfate rich groundwater in equilibrium with calcite and gypsum the reservoir rock is overlain by a very low permeability formation marls which acts as a caprock during and after co 2 injection the resulting co 2 rich acid solution gave rise to mineral dissolution and precipitation processes these reactions led to changes in porosity pore structure and permeability of the caprock and also to the alteration of its co 2 seal capacity flow through experiments using columns filled with three crushed samples marly limestone bituminous black shale and marl which constitute the hontomin caprock unit were conducted under different p total p co 2 atmospheric 1 10 3 5 bar subcritical 10 10 bar and supercritical 150 37 bar conditions and t 25 and 60 c using gypsum undersaturated and gypsum equilibrated solutions to evaluate the hontomin caprock reactivity 1d reactive transport modeling of the results enabled us 1 to better understand the overall processes that bring about the large dissolution of calcite minor dissolution of aluminosilicates and the precipitation of gypsum kaolinite zeolites and some aluminum and iron oxides and oxyhydroxides and sulfates and 2 to evaluate their implication for the hydrodynamic properties of the caprock an increase in porosity over the column length which mostly occurred near the inlet was calculated

geology and alteration geochemistry of the porphyry cu au deposit at bajo de la alumbrera argentina this paper describes the igneous geology alteration mineralogy and geochemistry as well as the ore mineralization history of bajo de la alumbrera a world class porphyry copper gold deposit in northwestern argentina the deposit occurs in the k rich calc alkaline farallon negro volcanic complex located 200 km east of the main andean porphyry copper belt of chile the deposit consists of a composite stock of dacitic porphyry intrusions and extends into the surrounding andesitic volcanic rocks two of the earliest intrusions now occupying the center of the intrusive complex show intense hydrothermal alteration and mineralization these two porphyries host the highest ore grades and were subsequently intruded by several weakly mineralized or barren porphyries intense quartz magnetite k feldspar alteration pervades the first mineralized porphyry whereas similar but lower intensity alteration affected the second laterally this alteration grades into potassic alteration secondary k feldspar and biotite which affects all porphyries except the latest dikes andesitic wall rocks within a hundred meters of the intrusions are dominated by dark hydrothermal biotite an outer halo of propylitic alteration epidote chlorite albite calcite extends up to 1 km into the andesites feldspar destructive alteration sericite pyrite clay minerals gypsum overprints the potassic and propylitic alteration in the volcanic rocks and all porphyries the alteration is locally controlled by faults and late fractures and developed most pervasively upon the outer part of the potassic zone and toward the transition to propylitic alteration in the upper part of the deposit mass balance calculations show small positive changes in net volume for the potassic alteration and minor volume decreases for the chlorite epidote and feldspar destructive alteration the intensely quartz magnetite veined sample of quartz magnetite alteration indicates a total volume increase of 350 percent copper and gold are intimately associated at all scales they occur as composite gold sulfide grains chalcopyrite rarely bornite show a close correlation of ore grades in sample assays and have a closely overlapping distribution on the mine scale a well developed ore shell coincides with potassic alteration and partly with the distribution of intense quartz magnetite veins even though the bulk of the ore minerals now occupy texturally late positions in vugs and fractures a barren zone with intense quartz magnetite potassic alteration and veins but little or no sulfides is interpreted as the focus of upflow of high temperature ore fluids prior to ore mineral saturation and coprecipitation of copper sulfides and gold in the ore shell

evolution of mineralizing fluid in the porphyry copper system of the skouries deposit northeast chalkidiki greece evidence from combined pb sr and stable isotope data the porphyritic syenite of the skouries deposit intruded the metamorphic basement of the serbomacedonian massif in the northeast chalkidiki peninsula at 19 ma the final eraplacement was controlled by dominantly northeast southwest trending steep faults that created pathways for the deep seated magma to rise to shallow crustal levels following its eraplacement stage i the porphyritic syenite suffered a pervasive potassic alteration stage ii approximately 590 degrees 640 degrees c two later veining stages with propylitic characteristics stage iiia approximately 480 degrees c stage iiib approximately 380 degrees c brought in most of the cu which was deposited in the form of chalcopyrite quartz sulfide calcite veins transect the porphyritic syenite as well as the country rocks in a narrow 50 m wide halo around the stock only the range of delta 18 o values from 3 5 to 7 6 per rail for the fluids in equilibrium with vein quartz is within the typical range of early ore forming fluids associated with porphyries representing magmatic fluids that may to some extent have interacted with the igneous wall rock a subsequent late propylitic alteration stage iv approximately 210 degrees c more localized and patchy affected the country rocks and the porphyritic syenite and deposited disseminated pyrite and chalcopyrite the delta 34 s values from vein and disseminated sulfides range from 2 1 to 0 3 per rail indicative of a magmatic origin for the sulfur the 207 pb 204 pb ratios from pyrite and chalcopyrite deposited in stage iiia early and stage iiib late veins 15 683 15 687 are markedly lower than those from disseminated sulfides related to stage iv 15 696 15 734 and lie within the range of 15 672 to 15 696 defined by feldspars from the porphyritic syenite the pb isotopes therefore indicate an evolution of the fluid composition from one characterized by magmatic components to one dominated by the country rocks whereas ore hosted in veinlets stage iii contains lead from both sources furthermore they suggest that the lead in the ores developed in continental crustal environments with high mu 2 and w 2 values and evolved in a reservoir with high th pb and low u pb ratios age corrected 87 sr 86 sr ratios from inclusion fluids in vein quartz range from 0 7086 to 0 7099 for veins within the country rock and from 0 7061 to 0 7080 in veins transecting the porphyritic syenite values for porphyry feldspars range from 0 7079 to 0 7081 and country rock from 0 7135 to 0 7342 these data confirm the pb isotope trends and indicate that sr contamination took place where the veins crosscut the country rocks fluids in veins within the porphyry could ascend rapidly from deeper levels without reacting with the porphyry and thus show an unaffected magmatic sr isotope signature pb and sr isotopes in inclusion fluids are shown to be extremely sensitive tracers for elucidating the hypogene leaching processes in the skouries porphyry system

geology re os ages sulfur and lead isotopes of the diyanqinamu porphyry mo deposit inner mongolia ne china the diyanqinamu porphyry mo deposit in the southern greater khingan range of the central asian orogenic belt contains 800 million metric tons mt of ore with an average grade of 0 097 molybdenum the deposit is hosted in late jurassic volcanic rocks of tuff andesite and volcanic breccia multiple stage hydrothermal activities have resulted in propylitic phyllic and argillic alteration in this deposit five stages i v of hydrothermal activity are identified stage i is represented by a mineral assemblage of epidote chlorite and magnetite with some discontinuous barren veinlets of quartz k feldspar fluorite magnetite epidote chlorite stage ii is marked by occurrence of quartz fluorite molybdenite magnetite pyrite sericite siderite veinlets veins with phyllic halos stage iii consists of fluorite siderite quartz molybdenite pyrite ankerite calcite chalcopyrite veins that are commonly related to phyllic alteration and dissemination of fluorite in the altered rocks stage iv has an assemblage of fluorite quartz pyrite ankerite calcite molybdenite chalcopyrite sphalerite galena in coarse veins 10 20 mm wide stage v consists of narrow 5 mm wide veinlets of calcite fluorite pyrite quartz molybdenite mainly occurs in stages ii and iii re os dating results for molybdenite samples from these two stages yielded an isochron age of 156 2 4 2 ma 2 mswd 0 96 n 10 most molybdenite samples have high 34s values 8 4 relative to other sulfide minerals i e galena sphalerite pyrite and chalcopyrite of stages ii to v 34s 2 5 8 3 n 22 molybdenite also has low 207pb 204pb and 208pb 204pb ratios relative to other sulfide minerals although there are minor overlaps in a diagram of 206pb 204pb versus 207pb 204pb these pb isotope data display a positive trend transecting the growth curves of crustal lead which could be invoked by mixing of crustal and mantle sources with distinct pb isotopes in combination with the s isotope data and mineral paragenesis we suggest that magmas were the main source of molybdenum whereas other metals i e pb zn and cu were possibly sourced from the country rocks

metallogeny and tectonics of porphyry copper molybdenum deposits in british columbia metallogenic studies in british columbia are based on data for over 1200 deposits that include metals and ore minerals recorded age and lithology of sedimentary and volcanic host rocks and the nature of any related granitoid intrusions analysis of these data defines a bimodal source of metals in porphyry deposits cu and mo are derived from the primary granitoid melt and the cu mo ratio reflects the composition of that melt pb zn ag and au occur in veins peripheral to porphyry intrusions and the metal content of these veins is controlled by the lithology of their wall rocks petrogenetic constraints imply that granitoids are predominantly anatectic crustal melts thus we use the distribution of porphyries with varying metal ratios to define a map of the lower crust which then constrains a tectonic model two major volcanic plutonic arcs coastal jurassic early tertiary takla triassic were generated above two subduction zones anatexis of the associated underplates produced cu porphyries th

platinum group minerals in the santo tomas ii philex porphyry copper gold deposit luzon island philippines mineralized quartz diorites of the santo tomas ii porphyry copper gold deposit carry high au contents average 1 8 ppm as well as 160 ppb pd and 38 ppb pt values of other platinum group elements pge and rhenium are below the analytical detection limits there is a significant positive correlation between au and cu the highest pd values were detected in the most au and cu rich rocks platinum group minerals pgm occur exclusively as inclusions in chalcopyrite and bornite potential pd and pt contents in sulphide concentrates are estimated at 1 5 g t and 0 4 g t respectively the precious metal assemblages consist of merenskyite main pgm kotulskite moncheite native gold electrum hessite and petzite polyphase fluid inclusions in quartz veinlets associated with a pgm bearing bornite chalcopyrite magnetite assemblage are characterized by high salinity 35 to 60 eq wt nacl and high trapping temperatures between 380 and 520 c they may represent primary magmatic hydrothermal fluids which have been responsible for the transport of pd pt and au as chloride complexes

carbonation of ca bearing silicates the case of wollastonite experimental investigations and kinetic modeling abstract carbonation reactions of wollastonite have been investigated in experiments conducted at conditions relevant to geologic co 2 sequestration in subsurface environments t 90 c and pco 2 25 mpa experiments were performed in batch reactors on single mineral powders of selected grain size either in supercritical co 2 or in aqueous solutions with different alkalinities the main reaction products were calcite and amorphous silica calcite occurred either as a compact continuous coating of small crystals in the case of supercritical co 2 and in circum neutral ph aqueous solutions or as isolated larger crystals in acidic aqueous solutions measured extents of carbonation were faster in aqueous solutions than in supercritical co 2 extents of carbonation in aqueous acidic solutions were modelled using a geochemical code incorporating kinetic parameters for wollastonite dissolution and calcite precipitation taken from the literature comparison with experimental results shows that in aqueous solutions wollastonite dissolution is the rate limiting step of the carbonation reaction and that silica layers have only a minor passivation effect on the overall reaction rate in acidic solutions secondary calcite coating has only a minor effect on carbonation extent whereas the experimental data in circum neutral ph aqueous solutions are consistent with dissolution rates inhibited by the observed dense calcite coating a geochemical code incorporating a modified reactive surface model successfully accounted for this passivation effect the more efficient carbonation in acidic than in circum neutral ph solutions is thus ascribed to differences in microstructures of the secondary calcite layers due to differences in supersaturation states of calcite when its precipitation begins inhibitory effects of dense calcite coating are also invoked for limiting carbonation extents of wollastonite in supercritical co 2 secondary calcite precipitations are thus shown to play a major role both as coatings of reactive surfaces and by maintaining large undersaturation with respect to wollastonite dissolution

reaction path modelling of in situ mineralisation of co2 at the carbfix site at hellisheidi sw iceland abstract results from injection of 175 tonnes of co2 into the basaltic subsurface rocks at the carbfix site in sw iceland in 2012 show almost complete mineralisation of the injected carbon in less than two years matter et al 2016 snaebjornsdottir et al 2017 reaction path modelling was performed to illuminate the rate and extent of co2 water rock reactions during and after the injection the modelling calculations were constrained by the compositions of fluids sampled prior to during and after the injection as reported by alfredsson et al 2013 and snaebjornsdottir et al 2017 the ph of the injected fluid prior to co2 dissolution was 9 5 whereas the ph of the background waters in the first monitoring well prior to the injections was 9 4 the ph of the sampled fluids used in the modelling ranged from 3 7 at the injection well to as high as 8 2 in the first monitoring well modelling results suggest that co2 rich water basalt interaction is dominated by crystalline basalt dissolution along a faster high permeability flow path but by basaltic glass dissolution along a slower pervasive flow path through which the bulk of the injected fluid flows dissolution of pre existing calcite at the onset of the injection does not have a net effect on the carbonation but does contribute to a rapid early ph rise during the injection and influences which carbonate minerals precipitate at low ph mg and fe are preferentially released from crystalline basalts due to the higher dissolution rates of olivine and to lesser extent pyroxene compared to plagioclase and glass gudbrandsson et al 2011 this favours the formation of siderite and fe mg carbonates over calcite during early mineralisation the model suggests the formation of the following carbonate mineral sequences siderite at ph 5 and calcite at higher ph other minerals forming with the carbonates are al and fe hydroxides and chalcedony and zeolites and smectites at elevated ph the most efficient carbonate formation is when the ph is high enough for formation of carbonates but not so high that zeolites and smectites start to form which compete with carbonates over both cations and pore space the results of reaction path modelling at the carbfix site in sw iceland indicate that this sweet spot for mineralisation of co2 is at ph from 5 2 to 6 5 in basalts at low temperature 20 50 c

in situ distribution of gold in ores using high resolution x ray computed tomography high resolution x ray computed tomography hrxct is the industrial equivalent of medical computed axial tomography cat scanning and provides a mechanism for nondestructive three dimensional analysis of ore samples hrxct produces two dimensional images slices that reveal the interior of an object as if it had been sliced open along the image plane for viewing by acquiring a contiguous set of slices a density map for all or part of a sample volume can be obtained allowing three dimensional inspection and measurement of features of interest hrxct can resolve details as small as a few tens of microns even when imaging objects are made of high density materials because the hrxct technique differentiates mineral grains largely based on their contrasting densities these studies are particularly effective in the study of gold and other extremely high density grains in contrast to typical rock forming minerals and other metallic minerals imaging of typical stockwork ore from the grasberg porphyry deposit identified native gold grains as small as 13 m in diameter all of the gold grains are associated with chalcopyrite masses indicating that both copper and gold concentrations occupy the same fracture porosity and thus appear to have been precipitated during the same mineralization event these reconnaissance investigations suggest considerable potential for hrxct studies to contribute to the understanding of ore forming systems and to practical applications such as ore dressing to maximize precious metal recovery

isotopic and geochemical characteristics of laramide magmatic systems in arizona and implications for the genesis of porphyry copper deposits major element trace element and nd sm and rb sr isotope data are described from igneous rocks in 11 multiphase magmatic complexes of laramide age in arizona eight complexes contain barren stocks as well as productive plutons associated with the formation of porphyry base metal deposits whereas in three complexes porphyry orebodies have not been recognized most of the complexes evolved through similar stages early dominantly intermediate volcanic rocks were intruded by multiphase complexes temporally characterized by increases in sio 2 changes in the ferromagnesian mineral assemblage increasingly porphyritic textures and a progression from barren to subproductive to productive intrusions within complexes the sequence is independent of both the absolute age of initiation of local magmatism and its duration analytical data and field relationships are combined to show elements of the petrogenetic history of these complexes potential relationships between productive and barren magmas and factors which may have influenced formation of the characteristic magmatic hydrothermal sequence the isotopic composition of laramide igneous rocks forms an array from epsilon ndt and 87 sr 86 sr initial values of 0 and 0 704 to 14 and 0 710 respectively early volcanic rocks have a more primitive signature consistent with retention of a significant mantle component subsequent intrusions were derived predominantly from isotopically heterogeneous precambrian lower crust but probably also contain an undefined amount of mantle component individual complexes do not exhibit any consistent isotopic trends over time and unique types of source rocks are not indicated for productive magmas in contrast rare earth elements ree in several complexes display temporally systematic behavior progressively younger intrusions in a given complex follow a path of decreasing concentration of ree steepening profiles greater upward concavity in heavy ree profiles and changes in the eu anomaly from negative to either markedly less negative or positive the ree data from individual complexes suggest an increasing petrogenetic involvement of amphibole either in the restite of the source region or as a fractionating phase and similar paths of petrogenetic evolution in spite of chronologic and trace element evidence which argues against completely comagmatic development productive and barren intrusions cannot be clearly distinguished by the isotopic data but the systematic ree trends parallel increasing productivity of magmas in individual complexes models which reconcile isotopic variation systematic ree behavior protracted local but largely noncomagmatic magmatism and the increasing development of porphyry mineralization include 1 progressive metasomatism of the crustal component 2 increasing assimilation of amphibolitic crust by mantle basalts and 3 migration of crustal anatexis from deep anhydrous rocks to shallower amphibolites the relative importance of these processes cannot yet be clearly assessed from the data but a plausible metallogenic impact of each would be upon the concentration and possibly the composition of magmatic volatiles in the primary melts and or during subsequent fractionation in this light existing models which propose that the principal control upon intrusion productivity is a balance between crystal fractionation and the timing of saturation and release of magmatic hydrothermal fluids may be strongly influenced by processes operative either in their source regions or during their interaction with the crust initiation of such processes may be a response to abrupt changes in tectonic regime in the volcanic are environment

a re os isotope study of sedimentary rocks and copper gold ores from the ertsberg district west papua indonesia abstract the ores of the ertsberg district consist of both porphyry stockwork and contact controlled mineralization related to the grasberg and ertsberg intrusion centers high grade copper mineralization with gold occurs in skarns on the periphery of each of the intrusion centers the periphery mineralization includes the kucing liar skarn related ores the massive sulfide lenses on the borders of the grasberg intrusive complex and the giant skarn bodies of the deep and intermediate ore zones together with the ores of the dom complex on the margin of the ertsberg diorite the ertsberg orebody the basis of discovery of the district is a copper gold roof pendant of sedimentary strata in the diorite in order to clarify genetic and geochronologic links between the peripheral sediment hosted ore bodies and the intrusion hosted ore bodies re os isotopes of the ores and subjacent precambrian and phanerozoic crust were analyzed re os geochronology of molybdenites was used to resolve the age relationships of the ore bodies the grasberg and kucing liar molybdenites have older molybdenite mineralization ages of 2 88 0 02 ma and 3 01 0 02 ma respectively whereas the ertsberg molybdenite has a younger age of 2 54 0 02 ma these data agree with ar chronologies of the alteration associated with mineralization pollard and taylor 2000 pollard p j taylor r 2000 geochronology of intrusive rocks and cu au mineralization in the ertsberg district in proceedings of freeport institut teknologi bandung itb geological symposium bandung java pp 17 19 and also indicate that the grasberg and kucing liar molybdenites are closely similar in age and older than the ertsberg intrusive system re os data from pyrite chalcopyrite magnetite gold and the surrounding sedimentary rocks from the district define a mixing relationship between samples from the initial stockwork mineralization and peripheral ores of each intrusion center sulfide and oxide minerals from primary stockwork mineralization are isotopically homogeneous and define trends on isochron diagrams with distinct os initial ratios whereas sulfides and oxides taken from peripheral ores are isotopically heterogeneous and define trends on mixing diagrams one possible end member for the mixing is sedimentary rock surrounding the porphyries the measured os ratios of the sedimentary rocks range from 0 52 to 2 21 and overlap the os initial ratios of the sulfides and oxides sampled from both stockwork and contact mineralization the data suggest a model in which the continental crust supplied some of the os and by inference other metals during magma genesis in the lower crust and the remainder came from sedimentary rocks near the intrusion centers

precious metal mineralogy in porphyry skarn and replacement type ore deposits of the ertsberg gunung bijih district irian jaya indonesia petrographic and electron microprobe analyses of native au and a variety of sulfide minerals indicate a generally high but widely varying native au fineness and a cu fe sulfide host for most ag in the gunung bijih timur complex of cu au skarn deposits the big gossan and dom cu skarn deposits and the grasberg porphyry cu au deposit native au rims bornite in veins and forms inclusions in bornite and chalcopyrite in samples from grasberg and from the gunung bijih timur complex as well as filling open space in quartz veins in the complex skarn and quartz veins in the big gossan area host native au in association with pyrite pyrrhotite galena chalcopyrite sphalerite and arsenopyrite native au from the gunung bijih timur complex has a wide but bimodal range of fineness 920 to 990 and 340 to 820 avg 860 native au from grasberg samples is or 930 fine avg 960 fineness of big gossan au ranges from 540 to 960 avg 830 although compositional ranges are small within most individual samples native au from grasberg falls into two groups with respect to pd pd bearing or 3 500 ppm avg 1 800 ppm and with no detectable pd fire assay of grasberg ore reveals trace but detectable 10 ppb pd 500 ppb avg or 50 ppb concentrations of pd and no detectable pt native au from the gunung bijih timur complex averages twice as much cu as that from grasberg 1 7 vs 0 8 wt cu native au from big gossan has uniformly low cu contents or 1 200 ppm cu avg 300 ppm mass balance calculations and analytical data indicate that the bulk of the ag in the gunung bijih timur complex is contained by bornite indicating a partitioning of ag into bornite relative to native au or a discrete ag mineral this is supported by the consistent positive correlation of cu and ag throughout the gunung bijih timur complex as well as in grasberg and dom ag bearing galena occurs in the big gossan area but is rare in the grasberg the gunung bijih timur complex and the dom orebodies the high fineness of native au from the gunung bijih district represents the upper end of the reported range for porphyry and skarn type cu au deposits but is similar to values reported elsewhere in indonesia the fineness of native au in the gunung bijih timur complex does not appear to be controlled by depth or distance from the local intrusive contact mineral assemblage or paragenetic relationship the fineness of native au from the big gossan area shows a positive correlation with elevation suggestive of a lower temperature more distal character than in the other skarns of the district differences in pd contents may be related to acidity and redox conditions during native au deposition high cu high pd and low ag compositions of au grains in pan concentrates suggest a porphyry or cu skarn source relative to a more distal source compositional characteristics identified in this study may have applications to exploration within the ertsberg district and elsewhere

evaluation of the impact of co2 co contaminant gas aqueous fluid and reservoir rock interactions on the geologic sequestration of co2 lowering the costs of front end processes e g separation in the geologic sequestration of co2 can dramatically lower the overall costs one possible approach is to sequester less pure co2 waste streams that are less expensive or require less energy to separate from flue gas or a coal gasification process etc the objective of this research is to evaluate the impacts of co2 itself as well as an impure co2 waste stream on geologic sequestration using reaction progress models reactive transport simulators and analogous reactive transport experiments run in a plug flow reactor specifically we are investigating the potential for co injecting the sox nox and h2s present in coal fired waste streams along with the co2 we present here the results of reactive transport simulations made to investigate the long term impact of dissolved co2 h2s and so2 on carbon sequestration in the frio fm tx the results suggest that addition of relatively large amounts of h2s to a co2 injection should not adversely impact injectivity or sequestration compared to the injection of co2 alone the co injection of so2 however could produce significantly different results if conditions are such that so2 can oxidize to sulfate in the long term the simulations suggest that carbonate mineral formation can sequester a significant fraction of the injected carbon through the formation of calcite magnesite and dawsonite

the role of silicate surfaces on calcite precipitation kinetics abstract the aim of this study is to illuminate how calcite precipitation depends on the identity and structure of the growth substrate calcite was precipitated at 25 c from supersaturated aqueous solutions in the presence of seeds of either calcite or one of six silicate materials augite enstatite labradorite olivine basaltic glass and peridotite rock calcite saturation was achieved by mixing a cacl2 rich aqueous solution with a nahco3 na2co3 aqueous buffer in mixed flow reactors containing 0 5 2 g of mineral rock or glass seeds this led to an inlet fluid calcite saturation index of 0 6 and a ph equal to 9 1 although the inlet fluid composition flow rate and temperature were identical for all experiments the onset of calcite precipitation depended on the identity of the seeds present in the reactor calcite precipitated instantaneously and at a constant rate in the presence of calcite grains calcite precipitated relatively rapidly on labradorite olivine enstatite and peridotite mainly composed of mg olivine surfaces but more slowly on augite and basaltic glass calcite precipitation rates however became independent of substrate identity and mass over time and all rates approach 10 9 68 0 08 mol s for 10 day long experiments and 10 9 21 0 2 mol s for 70 day long experiments scanning electron microscope images showed olivine enstatite and peridotite surfaces to be covered extensively with calcite coatings at the end of the experiments less calcite was found on labradorite and augite and the least on basaltic glass in all cases calcite precipitation occurs on the mineral rock or glass surfaces calcite precipitation on these surfaces however negligibly affects the dissolution rates of the silicate grains these results support ultramafic and basalt carbonation as a long term carbon storage strategy as calcite readily precipitates on the surfaces of minerals contained in these rocks without inhibiting their dissolution

dissolution of altered tuffaceous rocks under conditions relevant for co2 storage abstract we conducted co 2 water rock interaction experiments to elucidate the dissolution characteristics and geochemical trapping potential of three different altered andesitic to rhyolitic tuffaceous rocks tsugawa ushikiri and daijima tuffaceous rock relative to fresh mid ocean ridge basalt the experiments were performed under 1 mpa co 2 pressure to reproduce the water rock co 2 interactions in co 2 storage situations basalt showed high acid neutralization potential and rapid dissolution of silicate minerals two of the tuffaceous rocks ushikiri and daijima showed relatively high solubility trapping potential mainly due to the dissolution of carbonate minerals in the andesitic ushikiri tuffaceous rock and the ion exchange reaction with zeolite minerals in the rhyolitic daijima tuffaceous rock the mineral trapping potential of the ushikiri tuffaceous rock was found to be relatively high due to the rapid dissolution of mg and ca bearing silicate minerals our experimental results suggest that regions of porous and andesitic tuffaceous rock hold global promise as co 2 storage sites

mineral chemistry and sources of fluid and sulfur at the katbasu gold deposit in south tianshan nw china abstract katbasu is a gold and copper deposit located in an arc on the southern margin of the ili central tianshan micro continent an in situ method was conducted to acquire trace element concentrations to elucidate the origins and chemistry of the fluid in the katbasu deposit this included oxygen isotopes in quartz as well as sulfur isotopes and trace elements concentrations in pyrite trace elements in gold deficient veins have higher concentrations compared to those in the gold bearing veins the 18o values of gold deficient veins are between 3 9 and 8 1 which imply a magmatic oxygen isotope signature in contrast oxygen isotopes in gold bearing veins range between 1 3 and 5 8 indicating the involvement of meteoric water in the mineralization system this data combined with evidence from alteration style and metal assemblages shows that the ore forming fluids at the katbasu gold deposit is of a magmatic origin the data also indicates that meteoric water diluted the magmatic fluid and caused an oversaturation of gold causing precipitation of native gold grains trace elements in pyrite show no difference among the veins analyzed however they have distinctly different trace element patterns of pyrite from orogenic gold deposits based on the 34s values of pyrite 8 3 12 9 and the lack of coeval regional metamorphism we conclude that the enriched 34s at the katbasu gold deposit is derived from a subducted slab during the late carboniferous

construction of the adjoint mit ocean general circulation model and application to atlantic heat transport sensitivity we first describe the principles and practical considerations behind the computer generation of the adjoint to the massachusetts institute of technology ocean general circulation model gcm using r giering s software tool tangent linear and adjoint model compiler tamc the tamc s recipe for fortran line by line generation of adjoint code is explained by interpreting an adjoint model strictly as the operator that gives the sensitivity of the output of a model to its input then the sensitivity of 1993 annual mean heat transport across 29on in the atlantic to the hydrography on january 1 1993 is calculated from a global solution of the gcm the kinematic sensitivity to initial temperature variations is isolated showing how the latter would influence heat transport if they did not affect the density and hence the flow over 1 year the heat transport at 29on is influenced kinematically from regions up to 20 o upstream in the western boundary current and up to 5 o upstream in the interior in contrast the dynamical influences of initial temperature and salinity perturbations spread from as far as the rim of the labrador sea to the 29on section along the western boundary the sensitivities calculated with the adjoint compare excellently to those from a perturbation calculation with the dynamical model perturbations in initial interior salinity influence meridional overturning and heat transport when they have propagated to the western boundary and can thus influence the integrated east west density difference our results support the notion that boundary monitoring of meridional mass and heat transports is feasible

on the diversity of the pge content in chromitites hosted in ophiolites and in porphyry cu systems controlling factors abstract the present study on the diversity of the platinum group elements pge content in chromitites and porphyry cu deposits from greece and everywhere literature data aims to define factors controlling precious metal enrichment in ophiolite complexes and the unknown pd and pt potential in porphyry cu systems through an integrated set of mineralogical and geochemical approaches the pge content in chromitites associated with ophiolite complexes is commonly low a few 100 s of ppb however a significant pge enrichment up to 10 s of ppm is a feature of relatively small chromite occurrences regardless their major element composition plots of the pd ir versus normalized pt pt ratios defined separate fields corresponding to various chromitite types large chromite deposits exhibit low pd ir values reflecting low degree of fractionation primitive magmas negative pt pt partial melting of already depleted mantle and increasing partial melting trend from high al towards to high cr deposits the association with hydrous silicates cr bearing hydrogrossular chlorite and serpentine and texture features of os ir ru rich compatible or ipge minerals coupled with very low pd ir and negative pt pt values were attributed to an origin by partial melting of already depleted mantle and increased partial melting degree during a subsequent crustal mantle recycling stage via fluid driven processes assuming that the increasing pd ir reflects a fractionation trend of parent magma a significant enrichment in pt and pd incompatible or ppge occurring in small occurrences either high cr or high al type may be a sensitive fingerprint for the orientation in the mantle sequence of the ophiolites and exploration for chromite commonly the pge content in porphyry cu mo au deposits is less than 10 ppb however elevated pd pt contents over 6 ppm in sulfide rich samples are a characteristic feature of certain porphyry cu au alkaline intrusions evidence of a favorable tectonic setting post collisional for the origin of porphyry cu au pd pt elevated porphyry deposits include elevated up to hundreds of ppm contents in cr co ni and re and elevated 187 os 188 os ratios reflecting mixing and contribution to the magma composition the oxidized nature of parent magmas abundant magnetite and the evolved mineralized fluid system in porphyry deposits are considered to be critical requirements for the transportation and deposition of sufficient au and pge elevated pd pt and au contents in porphyry deposits combined with the association of the major pd mineral merenskyite with bornite and chalcopyrite major cu minerals are encouraging economic factors for the contribution to the global pd pt production

forsterite dissolution and magnesite precipitation at conditions relevant for deep saline aquifer storage and sequestration of carbon dioxide the products of forsterite dissolution and the conditions favorable for magnesite precipitation have been investigated in experiments conducted at temperature and pressure conditions relevant to geologic carbon sequestration in deep saline aquifers although forsterite is not a common mineral in deep saline aquifers the experiments offer insights into the effects of relevant temperatures and pco2 levels on silicate mineral dissolution and subsequent carbonate precipitation mineral suspensions and aqueous solutions were reacted at 30 c and 95 c in batch reactors and at each temperature experiments were conducted with headspaces containing fixed pco2 values of 1 and 100 bar reaction products and progress were determined by elemental analysis of the dissolved phase geochemical modeling and analysis of the solid phase using scanning electron microscopy infrared spectroscopy and x ray diffraction the extent of forsterite dissolution increased with both increasing temperature and pco2 the release of mg and si from forsterite was stoichiometric but the si concentration was ultimately controlled by the solubility of amorphous silica during forsterite dissolution initiated in deionized water the aqueous solution reached supersaturated conditions with respect to magnesite however magnesite precipitation was not observed for reaction times of nearly four weeks magnesite precipitation was observed in a series of experiments with initial solution compositions that simulated extensive forsterite dissolution the precipitation of magnesite appears to be limited by the process of nucleation and nucleation requires a critical saturation index between 0 25 and 1 14 at 95 c and 100 bar pco2 magnesite precipitation is fastest in the presence of an initial magnesite seed although magnesite precipitates do form on the surfaces of forsterite particles the presence of the forsterite surface does not significantly accelerate magnesite precipitation relative to solid free systems

the el galeno and michiquillay porphyry cu au mo deposits geological descriptions and comparison of miocene porphyry systems in the cajamarca district northern peru el galeno and michiquillay are early to middle miocene cu au mo porphyry related deposits located in the auriferous cajamarca district of northern peru the el galeno deposit 486 mt at 0 57 cu 0 14 g t au and 150 ppm mo is associated with multiple dioritic intrusions hosted within lower cretaceous quartzites and shales emplacement of the porphyry stocks 17 5 16 5 ma in a hanging wall anticline was structurally controlled by oblique faults superimposed on early wnw trending fold thrust structures early k feldspar biotite magnetite potassic alteration was associated with pyrite and chalcopyrite mineralisation a quartz magnetite assemblage that occurs at depth has completely replaced potassically altered rocks late and post mineralisation stocks are spatially and temporally related to weak quartz muscovite phyllic alteration high au grades are associated with early intrusive phases located near the centre of the deposit highest cu grades 0 9 cu are mostly associated with a supergene enrichment blanket whilst high mo grades are restricted to contacts with the metasedimentary rocks the michiquillay cu au mo deposit 631 mt at 0 69 cu 0 15 g t au 100 200 ppm mo is associated with a miocene 20 0 19 8 ma dioritic complex that was emplaced within the hanging wall of a back thrust fault the intrusive complex is hosted in quartzites and limestones the ne trending deposit is crosscut by nnw trending prospect scale faults that influenced both alteration and metal distribution in the sw and ne of the deposit potassic alteration zones contain moderate hypogene grades 0 14 g t au and 0 8 cu and are characterised by chalcopyrite and pyrite mineralisation the core of the deposit is defined by a lower grade 0 08 g t au and 0 57 cu phyllic alteration that overprinted early potassic alteration michiquillay contains a supergene enrichment blanket of 45 80 m thickness with an average cu grade of 1 15 which is overlain by a deep leached cap up to 150 m cu au mo el galeno michiquillay and au rich minas conga deposits in the cajamarca region are of similar age early middle miocene and intrusive rock type dioritic associations despite these geochronological and geochemical similarities findings from this study suggest variation in metal grade between the hybrid type and au rich deposits result from a combination of physio chemical factors these include variations in temperature and oxygen fugacity conditions during hypogene mineralisation resulting in varied sulphide assemblages host rock type precipitation of ubiquitous hydrothermal magnetite and late hydrothermal fluid flow resulting in a well developed phyllic alteration zone

chemical changes in fluid composition due to co2 injection in the altmark gas field preliminary results from batch experiments dissolution precipitation phenomena induced by co2 injection to altmark permian sandstone were observed through laboratory experiments carried out under simulated reservoir conditions 125 c and 50 bars of pressure the rock sample was collected from the altmark gas reservoir which is being considered for enhanced gas recovery two sets of experiments were performed with pulverized rock samples in a closed batch reactor with either pure water run 1 or 3 m aqueous nacl solution run 2 and reacted with injected co2 for 3 5 and 9 days the liquid samples were analyzed by inductively coupled plasma optical emission spectroscopy and total reflection x ray fluorescence where the latter proved to be a feasible alternative to conventional analytical techniques especially since only small sample volumes about 10 l are needed chemical analysis for both fluids water and nacl brine indicated a significant dissolution of calcite and anhydrite in the solution which might be a crucial process during co2 injection the brine solution enhanced the dissolution of calcite and anhydrite compared to pure water at the beginning of the reaction moreover the progressive higher si4 al3 molar ratios in average by a factor of 3 in the brine experiments indicated quartz dissolution thermodynamic calculations of mineral saturation indices highlighted the dissolution of the ca bearing minerals which was in agreement with experimental results modeling enabled an evaluation of the dissolution processes of minerals in a low salinity region yet hindrances to model more saline conditions emphasize the need for further laboratory studies in order to parameterize models for deep aquifer conditions

a distinctive pd hg signature in detrital gold derived from alkalic cu au porphyry systems abstract this study comprises the first systematic classification of native gold geochemistry within alkalic porphyry cu au systems and the placer expression of such systems the geochemistry and mineral associations of gold from four alkalic porphyry deposits in british columbia canada afton mount milligan mount polley and copper mountain have been compared to comment on the likely detrital gold expression of similar systems globally populations of gold grains collected from in situ hypogene mineralization as well as fluvial deposits downstream of these deposits have been characterized in terms of their alloy composition au ag cu hg and pd and associated mineral inclusions these data are combined to generate a microchemical signature gold compositions vary according to the alteration zone within a porphyry system previous compositional studies of gold in porphyry systems have focused on the most economically important ore associated with potassic alteration wherein native gold hosted either by bornite or chalcopyrite comprises tiny blebs typically 5 20 m containing detectable cu in the gold alloy to a maximum of around 5 but quite variable 2 30 wt ag the presence of such grains have been confirmed in hypogene ore from the four systems studied but they have been shown to be compositionally distinct from detrital gold collected from nearby fluvial placers which exhibit a strong pd and hg signature both in the alloy and as mineral inclusions several workers have described late stage veins associated with alkalic porphyries which contain distinctive pd hg bearing minerals in association with other sulphides and sulphosalts this unusual mineralogy has been observed in the mineral inclusion suites of populations of detrital gold grains collected in the environs of the porphyry systems we conclude that whilst the micron scale cu rich gold grains formed in potassically altered rocks are in general too small to be recovered during routine sediment sampling those formed in later stage hydrothermal systems are larger and exhibit a distinctive microchemical signature which may be differentiated from those of gold formed in other mineralizing systems consequently compositional studies of detrital gold could underpin a mineral indicator methodology in the exploration for alkalic porphyry cu au deposits

allard stock la plata mountains colorado an alkaline rock hosted porphyry copper precious metal deposit the allard stock which hosts a porphyry cu ag au pt metals deposit is an epizonal laramide pluton at the southwest end of the colorado mineral belt the stock and associated mineralization evolved by a complex interaction of igneous and metasomatic processes as follows stage 1 forceful emplacement of syenite plutons stage 2 intense hydrothermal argillization of stage 1 syenites stage 3 intrusion of mafic syenite plutons some of which are layered along shear zones stage 4 violent escape of volatiles producing intrusive breccia pipes stage 5 intense k metasomatic alteration of the older stock units with production of a fenitelike alteration halo extending 1000 m beyond the stock and simultaneous intrusion of carbonate bearing alkali feldspar dikes stage 6 emplacement of trachyte syenite pegmatite and mafic pegmatite dikes stage 7 deposition of metallic minerals sanidine quartz calcite and fluorite as veinlets and disseminated replacement masses from hydrothermal solutions the stock

phase transitions in the mgco2h2o system and the thermal decomposition of dypingite mg5 co3 4 oh 2 5h2o implications for geosequestration of carbon dioxide abstract the application of hydrated mg carbonates as co2 sequestering media is a pressing environmental challenge which requires a deep knowledge of the phase transitions occurring in the mg co2 h2o system as well as the thermal and structural stability of these phases in this paper we investigate the phase transition of nesquehonite mgco3 3h2o to dypingite mg5 co3 4 oh 2 5h2o occurring after an incubation of months and years in solution at ambient conditions however as the kinetics of this process resulted to be slow the phase transition of dypingite to hydromagnesite mg5 co3 4 oh 2 4h2o was investigated at non ambient conditions using in situ real time high resolution x ray powder diffraction moreover the thermal behaviour of dypingite and its decomposition have been also investigated with the aim to explore the appropriateness of this carbonate and the products of its decomposition as sinks of anthropogenic carbon dioxide the results suggest that the dypingite structure remains unaffected up to 438 k at temperature above this threshold dypingite transforms into hydromagnesite a further increase in temperature converts the well ordered hydromagnesite into a collapsed form at 528 k the heating of dypingite does not produce a loss of co2 as the intermediate phases have the same co2 mg molar ratio the final product of the heating is periclase mgo its nucleation occurs at temperature ranging from 573 to 663 k and it becomes the only phase in the temperature range 633 678 k these results highlighted that dypingite assures a stable storage of co2 in the conditions that prevail at the earth s surface moreover the transformation of dypingite in more thermodynamically stable hydromagnesite occurring without release of co2 enhances the safety of carbon dioxide disposal in solid form furthermore the observed volume changes during phase transitions which in turn could affect the porosity and permeability of the geological reservoir have been evaluated in order to improve the prediction of the safe and permanent storage of co2 in underground

effects of mineral spatial distribution on reaction rates in porous media 1 this study examined the effects of variations in mineral spatial distributions on reaction rates in porous media pore scale network models were constructed to represent sandstones with anorthite and kaolinite present in various amounts and in different spatial patterns simulation conditions corresponded to geological sequestration of carbon dioxide to examine scaling effects arising from pore scale heterogeneities reaction rates from network models were compared to rates from continuum models that use uniform concentrations with small percentages of reactive minerals the scaling effects are large and the effect of spatial distribution is significant scaling effects are largest when reactive minerals are closely clustered and oriented parallel to flow conversely spatial distributions that enhance mass transport to and from reactive minerals such as small mineral clusters or elongated clusters oriented transverse to flow result in reaction rates that are well represented by the continuum model

the partition of regional sea level variability abstract the existing altimetric record offers an unprecedented view of sea level variability on a global scale for more than 2 decades optimal inference from the data involves appropriate partition of signal and noise in terms of relevant scales physical processes and forcing mechanisms such partition is achieved here through fitting a general circulation model to altimeter and other datasets to produce a best estimate of variability directly forced by the atmosphere the signal of primary interest here in this context noise comes primarily from instrument errors and meso scale eddies as expected but spatial smoothing effectively reduces this noise a separate constraint is thus formulated to measure the fit to monthly large scale altimetric variability that unlike the daily pointwise constraint shows a high signal to noise ratio the estimate is explored to gain insight into dynamics forcing and other factors controlling variability contributions from thermo steric halo steric and bottom pressure terms are all important depending on region but slopes of steric spectra red and bottom pressure spectra white are nearly invariant with latitude much variability can be represented by a seasonal cycle and linear trend plus a few eofs that can be associated with known modes of climate variability and or with topographic controls both wind and buoyancy forcing are important the response is primarily basin bound in nature but uneven patterns of propagation across basin boundaries are clearly present with the pacific being able to affect large portions of the indian and atlantic basins but the atlantic affecting mostly the arctic

hidden mineral deposits in cu dominated porphyry skarn systems how resource reporting can occlude important mineralization types within mining camps a single mining camp or ore deposit can contain multiple mineral deposit types but may have mineral reserves or resources classified by what a mining or mineral exploration company considers to be the dominant mineralization type in the area in this paper we summarize recent work on the challenges of reporting mineral deposits by geologic processes rather than by grades tonnages and mineral processing approaches for example the ertsberg grasberg district of indonesia contains several large skarn cu au ag deposits with the discovery outcrop as well as early production entirely in skarn all early publications and resource descriptions refer to it as the ertsberg district subsequent discovery of the giant grasberg porphyry cu au ag deposit led to the entire district being renamed grasberg and classified as a porphyry deposit despite the skarn focused discovery and early production history of the deposit as well as the presence of several large skarn deposits within the district the ok tedi cu au ag deposit of western papua new guinea also is generally thought of as a major porphyry cu deposit yet hosts both porphyry and skarn mineralization current reserve estimates indicate that the majority of the contained metal within the deposit is hosted by skarns rather than porphyry bodies thus following the grasberg example in terms of contained metal ok tedi could be classified as a skarn rather than a porphyry deposit in addition comparatively minor mineral deposits can prove useful during exploration this is exemplified by the large au cu ag porphyry deposits at cadia in australia that were discovered by exploring modest skarn deposits using the ertsberg grasberg skarn porphyry model here we extend a recent global compilation of economic cu mineral resources by analyzing cumulative production and reserve resource data for ertsberg grasberg ok tedi and cadia and provide a brief review of a number of other cu projects that contain multiple mineralization types overall in order to help inform exploration strategies as well as facilitate the development of more comprehensive and accurate mineral deposit models there is clearly positive value for the mineral exploration and mining industry in reporting ore reserves and mineral resources by mineralization type

sea level rise during past 40 years determined from satellite and in situ observations the 3 2 0 2 millimeter per year global mean sea level rise observed by the topex poseidon satellite over 1993 98 is fully explained by thermal expansion of the oceans for the period 1955 96 sea level rise derived from tide gauge data agrees well with thermal expansion computed at the same locations however we find that subsampling the thermosteric sea level at usual tide gauge positions leads to a thermosteric sea level rise twice as large as the true global mean as a possible consequence the 20th century sea level rise estimated from tide gauge records may have been overestimated

gold mineralization and skarn development near muara sipongi west sumatra indonesia gold mineralized skarns occur near the village of muara sipongi in west sumatra and were mined for gold prior to world war ii they are developed in limestones and andesitic volcanics of permo triassic age into which late jurassic diorites and granodiorites have been intruded the intrusions are of i type affinity the skarns range from andradite diopside rocks to grossular idocrase wollastonite diop side rocks which formed at about 450 degrees to 650 degrees c later retrogressive alteration caused the formation of epidote prehnite pumpellyite actinolite chlorite calcite and quartz these phases record temperatures down to less than 200 degrees c fluids during skarnification probably contained less than 5 mole percent co 2 during retrogressive hydration the skarns were mineralized locally with chalcopyrite pyrite magnetite hematite bornite and gold followed by sphalerite arsenopyrite marcasite tetrahedrite co ni sulfarsenides and au ag tellurides chlorite calcite retrogressive alteration of the skarns is related to quartz veining which is hosted by the volcanic members of the country rocks these veins are enriched in pb zn compared to the skarns gold occurs as inclusions within arsenopyrite fluid inclusion data indicate the vein forming fluids to be weakly saline and to contain minor co 2 but also to contain significant amounts of ch 4 and n 2 homogenization temperatures fall in the range 180 degrees to 240 degrees c which together with the low co 2 correlate with the conditions inferred for chlorite calcite skarn alteration the composition of native gold derived from skarn and associated veins is characterized by 5 to 35 at percent ag and up to 0 8 at percent cu a suite of alluvial golds in the area have negligible cu and 45 to 65 at percent ag and can be related to a nearby suite of tertiary epithermal quartz veins the bulk au ag cu pattern and gold compositions of the muara sipongi mineralization are discussed and compared with other examples of gold bearing skarns and cu porphyries with which they are often associated the source and controls on mobilization of the gold may be significantly influenced by regional faults in the area which form part of the 1 600 km long sumatra fault zone pervasive alteration of altrabasic and basic assemblages which are associated with this fault system is one mechanism for liberating au and other metals that are subsequently channeled upward along faults to be deposited in a favorable environment the gold was most probably transported by thio and or carbonyl complexes

olivine dissolution rates a critical review abstract the dissolution rates of olivine have been considered by a plethora of studies in part due to its potential to aid in carbon storage and the ease in obtaining pure samples for laboratory experiments due to the relative simplicity of its dissolution mechanism most of these studies provide mutually consistent results such that a comparison of their rates can provide insight into the reactivity of silicate minerals as a whole olivine dissolution is controlled by the breaking of octahedral m2 oxygen bonds at or near the surface liberating adjoining sio44 tetrahedra to the aqueous fluid aqueous species that adsorb to these bonds apparently accelerate their destruction for example the absorption of h h2o and at some conditions selected aqueous organic species will increase olivine dissolution rates nevertheless other factors can slow olivine dissolution rates notably olivine dissolution rates are slowed by lowering the surface area exposed to the reactive aqueous fluid by for example the presence and or growth on these surfaces of either microbes or secondary phases the degree to which secondary phases decelerate rates depends on their ability to limit access of the reactive aqueous fluids to the olivine surface it seems likely that these surface area limiting processes are very significant in natural systems lowering olivine surface reactivity in many environments compared to rates measured on cleaned surfaces in the laboratory a survey of the literature suggests that the major factors influencing forsteritic olivine dissolution rates are 1 ph 2 water activity 3 temperature and 4 mineral fluid interfacial surface area evidence suggests that the effects of aqueous inorganic and organic species are relatively limited and may be attributed at least in part to their influence on aqueous solution ph moreover the observed decrease in rates due to the presence of secondary mineral coatings and or the presence of microbes can be attributed to their ability to decrease olivine surface area directly exposed to the reactive aqueous fluid as the reactivity of forsterite surfaces are spatially heterogeneous its surface area normalized rates will tend to decrease as it dissolves even in the absence of a mineral or bacterial coating each of these factors limits and or influences the application of forsterite dissolution to 1 enhanced weathering efforts 2 mineral carbonation and 3 the low temperature generation of hydrogen or hydrocarbons via the oxidation of its divalent iron

dolomite effect on borosilicate glass alteration dolomite camg co3 2 is one of the common rock forming minerals in many geological media in particular in clayey layers that are currently considered as potential host formations for a deep radioactive waste disposal facility magnesium in solution is one of the elements known to potentially enhance the alteration of nuclear glasses the alteration of borosilicate glasses with dolomite as a mg bearing mineral source was investigated for 8 months in batch tests at 90 c glass composition effects were investigated through two compositions sibnaalcazro and sibnaalzro differing in their ca content the ca rich glass alteration is slightly enhanced in the presence of dolomite compared to the alteration observed in pure water this greater alteration is explained by the precipitation of mg silicate phases on the dolomite and glass surfaces in contrast the ca free glass alteration decreases in the presence of dolomite compared to the alteration observed in pure water this behavior is explained by ca incorporation in the amorphous layer formed during glass alteration coming from dolomite dissolution calcium acts as a layer reorganizer and limits glass alteration by reducing the diffusion of reactive species through the altered layer modeling was performed using the graal model implemented within the chess hytec geochemical code to discriminate and interpret the mechanisms involved in glass dolomite interactions magnesium released by dolomite dissolution reacts with silica provided by glass alteration to form mg silicates this reaction leads to a ph decrease the main mechanism controlling glass alteration is the ability of dolomite to dissolve during the experiment the quantities of secondary phases formed were very small but for longer time scales this mechanism could supply sufficient mg in solution to form large amounts of mg silicates and sustain glass alteration the ability of the graal model to reproduce the concentrations of elements in solution and solid phases regardless of the amount of dolomite and the glass composition strongly supports the basic modeling hypothesis

geodynamic evolution of the taiwan luzon mindoro belt since the late eocene abstract the structural framework of the taiwan luzon mindoro belt or festoon is described following three major transects the luzon transect with active subduction and active island arc the taiwan transect with active collision the mindoro transect with active subduction and inactive collision based on this geological study and on available geophysical data a model for the geodynamic evolution of this portion of the philippine sea and eurasia plates boundary is proposed in a succession of reconstructions between the late eocene and the present the major geodynamic events are 1 1 beginning of the opening of the south china sea s c s in lower oligocene times contemporaneous with obduction of the zambales and angat ophiolites on luzon 2 2 subduction of a mesozoic oceanic basin along the proto manila trench from the upper oligocene to the lower miocene 3 3 obduction of the south china sea oceanic crust onto the chinese and reed bank calamian passive margins in middle miocene time 14 15 ma related to a major kinematic reorganization end of opening of the s c s 4 4 beginning of collision between the luzon microblock and the two margins of the s c s in the upper miocene 7 ma collision is still active in taiwan whereas it stopped in mindoro during the pliocene

the lower changjiang yangzi yangtze river metallogenic belt east central china intrusion and wall rock hosted cu fe au mo zn pb ag deposits abstract the lower valley of changjiang from wuhan of the hubei province in the west to zhenjiang of the jiangsu province in the east contains more than 200 polymetallic cu fe au mo zn pb ag deposits and is one of the most important metallogenic belts in china this metallogenic belt situated at the northern margin of the yangzi craton and bordered by the dabieshan ultrahigh pressure metamorphic belt to the north consists mainly of cambrian triassic marine clastic sedimentary rocks and carbonate and evaporite rocks which overlay a precambrian basement and are intruded by yanshanian 205 to 64 ma granitoid intrusions and subvolcanic complexes repeated tectonism from late proterozoic to triassic resulted in extensively developed networks of faults and folds involving the cambrian triassic sedimentary strata and the precambrian basement the yanshanian granitoid intrusions and subvolcanic complexes in the lower changjiang metallogenic belt are characterized by whole rock 18 o of 8 to 10 initial 87 sr 86 sr of 0 704 to 0 708 and ndt from 10 to 17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials also the yanshanian granitoids exhibit eastward younging and increase in alkalinity i e from older calc alkaline in the west to younger subalkaline alkaline in the east which are related to oblique collision between the yangzi and sino korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes most polymetallic deposits in the lower changjiang metallogenic belt are clustered in seven districts where the yanshanian magmatism is particularly extensive from west to east edong jiurui anqing guichi luzhong tongling ningwu and ningzhen mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits orebodies in yanshanian granitoid intrusions skarn orebodies at the contact zones between the yanshanian intrusions and late paleozoic early mesozoic sedimentary rocks and stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata the most important host sedimentary strata are the middle carboniferous huanglong formation lower permian and lower middle triassic carbonate and evaporite rocks the intrusion hosted and skarn orebodies exhibit well developed zonation in alteration assemblages metal contents and isotopic compositions within individual deposits and apparently formed from hydrothermal activities related to the yanshanian magmatism the stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano sedimentary exhalative processes in shallow marine environments however extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization on the basis of geological relationships and isotope geochemical characteristics we propose a carbonate hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies this model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the yanshanian intrusions with carbonate and evaporite wall rocks mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion hosted orebodies the stratabound massive sulfide deposits of the lower changjiang metallogenic belt share many features with the well studied high temperature carbonate hosted replacement deposits of northern mexico and western united states particularly with respect to association with small shallow granitoid complexes structural and stratigraphic controls on mineralization alteration assemblages geometry of orebodies metal association metal zonation and isotopic systematics

the ridgeway gold copper deposit a high grade alkalic porphyry deposit in the lachlan fold belt new south wales australia ridgeway is a high grade gold copper porphyry deposit 54 mt at 2 5 g t au and 0 77 cu related to an alkalic intrusive complex of monzonitic composition the deposit occurs within the cadia district of new south wales australia which consists of a cluster of four late ordovician gold copper porphyry deposits and two iron copper gold skarn deposits with a combined gold resource in excess of 574 metric tonnes t the deposits lie on a 7 km long northwest oriented corridor of alteration and mineralization transverse to the axis of the postulated volcanic arc alteration and mineralization at ridgeway are zoned around a vertically attenuated intrusive complex of monzodioritic to quartz monzonitic composition distinct styles of veining and alteration are related to different intrusive phases of the monzonite complex with the intensity of alteration and grade of mineralization decreasing from early to late mineral intrusions early mineral intrusions are associated with intense actinolite magnetite biotite calc potassic alteration and up to four stages of high grade quartz magnetite sulfide veining bornite is the most abundant sulfide formed during early stage alteration and correlates well with gold moderate to weak intensity orthoclase biotite plus or minus magnetite potassic alteration accompanies the inter and late mineral intrusions this alteration being associated with chalcopyrite and pyrite rich quartz orthoclase veins propylitic and sodic albite pyrite alteration assemblages are peripheral to and locally overprint the potassic alteration phyllic alteration is restricted to the margins of late stage faults the fluid inclusion assemblage comprises one and two salt bearing brine inclusions in addition to aqueous liquid vapor inclusions of low to moderate salinity no low density vapor rich inclusions are present indicating that the fluids from which the quartz veins precipitated did not enter the liquid vapor field of the h2o nacl system the brine inclusions undergo final homogenization to liquid via halite dissolution this phenomenon in addition to the absence of low density vapor inclusions suggests that the mineralizing fluids at ridgeway were nonboiling hypersaline brines that exsolved directly from the crystallizing magma the presence of mineralized aplitic vein dikes and comb quartz layering are interpreted to indicate that the early and transitional stages of mineralization at ridgeway formed at the transition between magmatic and hydrothermal conditions

adjoint sensitivity of an ocean general circulation model to bottom topography abstract bottom topography or more generally the geometry of the ocean basins is an important ingredient in numerical ocean modeling with the help of an adjoint model it is shown that scalar diagnostics or objective functions in a coarse resolution model such as the transport through drake passage the strength of the atlantic ocean meridional overturning circulation the deacon cell and the meridional heat transport across 32 s are sensitive to bottom topography as much as they are to surface boundary conditions for example adjoint topography sensitivities of the transport through drake passage are large in choke point areas such as the crozet kerguelen plateau and south of new zealand the atlantic meridional overturning circulation is sensitive to topography in the western boundary region of the north atlantic ocean and along the scotland iceland ridge many sensitivities are connected to steep topography and can be interpreted in terms of bottom form stress that is the product of bottom pre

gold in porphyry copper deposits experimental determination of the distribution of gold in the cu fe s system at 400 to 700 c experiments in the system au cu fe s were carried out at temperatures of 400 to 700 c to determine how much gold could be accommodated by bornite and chalcopyrite the two most common ore minerals in porphyry copper gold deposits our results show that for all temperatures bornite contains one order of magnitude more gold than chalcopyrite or intermediate solid solution iss its high temperature equivalent the range of gold concentrations in bornite and chalcopyrite or iss decreases with decreasing temperature from 1 280 to 8 200 ppm au in bornite and 100 to 125 ppm au in iss at 600 c to 235 to 364 ppm au in bornite and 5 to 16 ppm au in chalcopyrite or iss at 500 c and to 13 to 80 ppm au in bornite and 2 to 4 ppm au in chalcopyrite or iss at 400 c the amount of gold in bornite is also strongly dependent on the composition of bornite being highest in stoichiometric bornite compositions cu5fes4 and decreasing toward cu rich and cu poor compositions phase equilibrium constraints for solutions with geologically reasonable reduced sulfur contents indicate that high temperature porphyry copper gold deposits will contain bornite and magnetite whereas lower temperature deposits whether primary or overprinted by phyllic alteration will contain chalcopyrite and pyrite if gold is present in the ore forming solutions more of it will be deposited in high temperature porphyry copper gold deposits where it will be closely associated with bornite coexisting magnetite in these deposits should generate magnetic anomalies lower temperature deposits will contain less gold which is hosted by pyrite as well as chalcopyrite and will lack magnetic anomalies comparison of the amount of gold hosted by natural porphyry copper gold ores to that hosted by bornite and chalcopyrite in our experiments suggests that significant amounts of gold can be lost from these deposits into surrounding hydrothermal systems

influence of amorphous silica layer formation on the dissolution rate of olivine at 90 c and elevated pco2 for mitigating against rising levels of atmospheric co2 carbonation of m2 bearing silicates has been proposed as a possible option for sequestering co2 over long time spans due to its rapid far from equilibrium dissolution rate and its widespread occurrence in mafic and ultramafic rocks olivine has been suggested as a potentially good candidate for achieving this goal although the efficacy of the carbonation reaction still needs to be assessed with this as a goal the present study aims at measuring the carbonation rate of san carlos olivine in batch experiments at 90 c and pco2 of 20 and 25 mpa when the reaction was initiated in pure water the kinetics of olivine dissolution was controlled by the degree of saturation of the bulk solution with respect to amorphous silica this yet unrecognized effect for olivine was responsible for a decrease of the dissolution rate by over two orders of magnitude in long term 45 days carbonation experiments with a high surface area to solution volume ratio sa v 24 600 m 1 the final composition of the solution was close to equilibrium with respect to sio2 am independent of the initial concentration of dissolved salts nacl and naclo4 ranging between 0 and 1 m and with an aqueous mg si ratio close to that of olivine no secondary phase other than a ubiquitous thin 40 nm si rich amorphous layer was observed these results are at odds with classic kinetic modeling of the process due to experimental uncertainties it was not possible to determine precisely the dissolution rate of olivine after 45 days but the long term alteration of olivine was indirectly estimated to be at least 4 orders of magnitude slower than predicted taken together these results suggest that the formation of amorphous silica layers plays an important role in controlling the rate of olivine dissolution by passivating the surface of olivine an effect which has yet to be quantified and incorporated into standard reactive transport codes

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

pge geochemistry of the fengshan porphyry skarn cu mo deposit hubei province eastern china abstract the fengshan cu mo deposit is located in the western part of the jiurui cu au mo district in the late mesozoic middle lower yangtze river metallogenic belt yrmb eastern china the mineralization is spatially associated with the fengshan granodiorite porphyry stock 149 138 ma where two types of ore bodies porphyry skarn occur the fengshan deposit is located on the yangtze craton i e in an intracontinental extensional environment a geological setting not considered by previous studies of pge abundance and distribution in porphyry systems for the present investigation the pge geochemistry of fourteen samples of the granodiorite ore and flotation concentrates were determined by icp ms after preconcentration by the lead fire assay technique from large 30 g samples a maximum of 32 ppb pd and 81 2 ppb pt is reported for the molybdenum flotation concentrate cu au pt pd contents from flotation concentrate samples are almost 1 to 2 orders of magnitude higher than those reported for ore samples this is especially true for the pt content covariant diagrams of cu and mo with noble metals au ag pt and pd reveal weak correlation between cu vs au ag and mo vs pt also au shows a slightly positive relationship with pt and pd it is apparent that pd and pt contents of flotation concentrate from the fengshan deposit are considerably lower than those reported for porphyry deposits in an island arc setting however au and ag appear to be elevated in the fengshan deposit the intrusion derived from an enriched mantle source high oxygen fugacity fo2 and liberation of mantle sulfates during partial melting are the first steps for pge enrichment in porphyry cu deposits however the fengshan granodiorite was most likely generated by partial melting of enriched mantle that was previously metasomatized by slab melts related to an ancient subduction system au pt and pd in potassic alteration zones and or endocontact zones are transported as an aqueous chloride complex in high temperature hypersaline fluid in contrast au pt and pd would be transported by bisulfide complex in low temperature intermediate salinity fluid in phyllic alteration zones and or exocontact marble that is distinctly different from the porphyry cu deposits in an island arc environment where intrusion derived directly from slab melting and pd and pt are transported only as chloride complexes

platinum group element and gold contents in the skouries porphyry copper deposit chalkidiki peninsula northern greece the skouries porphyry copper deposit is located in the eastern chalkidiki peninsula northern greece along with several other porphyry copper occurrences this deposit establishes the northeastern part of the servomacedonian zone as a porphyry copper region amphibolite mica schist and two mica gneiss are the predominant rock types exposed in the skouries area these rocks have been intruded by the skouries porphyry stock which is of subalkaline composition and is tertiary in age 18 ma the skouries porphyry intrusion and the surrounding country rocks are strongly fractured and intensely altered by hydrothermal fluids in addition to intense silicification a prominent alteration type is potassic whereas phyllic and propylitic types are less common mineralization mainly includes chalcopyrite pyrite bornite chalcocite and magnetite in the form of veins stockworks and disseminations native gold and electrum commonly are present as small inclusions in chalcopyrite although lateral zoning is not defined clearly a vertical zoning in terms of both metal mineralogy and overall metal content is apparent a zone of oxidation azurite malachite covers the upper part of the ore and is underlain by a zone of reduced rock rich in covellite and chalcocite which in turn is underlain by the most important ore type including a chalcopyrite pyrite bornite magnetite assemblage both weakly and intensively altered porphyry samples from the deposit were analyzed for major oxides trace elements and all platinum group elements pge the stock exhibits high levels of cu au ag b bi co se and te barium and sr contents are also high while rb is low resulting thereby in high k rb and low rb sr ratios palladium concentrations range from less than 2 to 480 ppb ruthenium content ranges from 8 to 41 ppb and pt from 2 to 10 ppb osmium ir and rh content is below detection limit the average au ag ratio is 0 87 which is consistent with the range of several worldwide porphyry copper deposits on the basis of factor analysis of selected geochemical data a strong positive interelement correlation r or 0 83 between au ag pd nd te coupled with their association with silica appears to support a correlation of these precious metals with silicification rather than potassic type alteration such a relationship may suggest similar behavior of these metals and a common origin a positive correlation of cu with iron r 0 86 which is consistent with the association of chalcopyrite with magnetite and the low correlation of te and pd with cu may suggest that these metals and to a lesser extent copper have been redistributed during a late stage of evolution of the skouries porphyry system furthermore the close association of te with precious metals combined with the relatively low temperature for telluride minerals stability may indicate that at least partly precious metal tellurides have been formed in a relatively shallow and less hot environment

experimental study of mg rich silicates carbonation at 400 and 500 c and 1 kbar the reactivity of olivines orthopyroxenes and serpentines chrysotile with co2 rich fluids was experimentally studied at 400 500 c and 1 kbar nacl levels of formation of solid carbonate phases were measured both by analysing the recovered gas phase and by step heating of the solid samples carbonation levels of several percents per hour from 3 to 57 in 4 h depending upon experimental conditions were measured with increasing efficiency in the order orthopyroxene chrysotile olivine in the case of olivine a positive impact of water fugacity and salinity on carbonation levels was evidenced microstructures of the samples showed that the carbonation reaction proceeded by dissolution precipitation a coupling between solid carbonate production mostly as magnesite and olivine serpentinisation was demonstrated isotopic compositions of carbon in gas phases and carbonates were measured they were found to be consistent with mass balance calculations additionally suggesting the existence of an accessory carbon bearing phase carrying negative 13c signatures this phase was identified by transmission electron microscopy as an ill ordered graphite phase which would account for about 15 of carbon mineral under these conditions

high resolution x ray computed tomography studies of grasberg porphyry cu au ores papua indonesia high resolution x ray computed tomography hrxct provides unique information of the geological and metallurgical significance for gold and related ore minerals in the supergiant grasberg porphyry cu au deposit digital radiographs have proved to be an effective means of screening samples for the presence of gold for hrxct studies digital radiograph effectiveness is limited by the thickness of samples typically to 2 cm as well as the associated minerals thus preselecting samples for gold studies using hrxct is most effective using digital radiographs combined with assay information differentiating between metallic mineral grains with relatively small differences in density e g bornite 5 1 g cm3 from chalcopyrite 4 2 g cm3 is relatively straightforward for isolated monominerallic grains or composites in a similar lower density matrix but difficulties are encountered with the interpretation of typical intergrown ore minerals x ray beam hardening artifacts lead to inconsistency in attenuation determination both within and among slice images complicating quantitative processing however differentiation of chalcopyrite and bornite has been successful in smaller diameter 22 mm cores of grasberg ores small diameter 10 mm cores of the grasberg stockwork cu au ore were analyzed using hrxct methods scanned at the minimum spacing currently available 7 5 m and data reduction protocols using the blob3d program were modified to improve the quantification of grain sizes and shapes grains as small as 6 5 m have been identified all of these grains are in direct contact with chalcopyrite providing support for gold distribution in porphyry copper systems being a result of exsolution from copper sulfides hrxct scanning digital radiography precisely defines the in situ location of mineral grains of interest within a sample which then can be studied in conventional petrographic sections and other types of analytical studies conducted e g gold trace element geochemistry

factors controlling pt pd enrichments in intracontinental extensional environment implications from tongshankou deposit in the middle lower yangtze river metallogenic belt eastern china abstract the tongshankou deposit is located in the southern part of the edong district in the late mesozoic middle lower yangtze river metallogenic belt eastern china alterations related to the porphyry and skarn mineralization are pervasive and intensive based on the ore metal contents four groups of ores mineralized rocks are divided cu mo mineralized rock cu mo ore cu mo w ore and cu ore the former two groups are porphyry related and the latter two groups are skarn related the average grades of au pt and pd in the ores are hundreds ppb 2 3 ppb and 10 ppb respectively while they are 340 ppb 29 3 ppb and 14 4 ppb in the flotation concentrations respectively considering the similar geological characteristics and tectonic setting intracontinental extensional environment iee for the tongshankou and fengshan pcds they are compared with the pc ds that formed in an island arc environment iae our data show that 1 pd and pt contents of pcds in iee are much lower than those of pcds in iae 2 pd is more abundant than pt in pcds critical controlling factors for pt pd enrichments in pcds include 1 oxidized mantle derived parental magmas which also explain why pcds in iae have higher pt pd contents than pcds in iee 2 modes of pge transport and precipitation as chloride or bisulfide complexes in late stage hydrothermal fluids 3 behavior of sulfur during the magmatic evolution since pge and au could be captured and preserved in magma due to sulfur undersaturation

temporal changes in ocean eddy transports abstract new estimates from 11 yr of altimetric data are made of the global time average variability kinetic energy and its decadal scale variability making the approximation that the variability reflects primarily eddy motions a time mean but spatially varying eddy mixing coefficient is then estimated along with its changes over the last decade with a record length more than 2 times that previously available the time mean variability kinetic energy ke is statistically more reliable and smoother in its spatial pattern minimum values of ke are present in the subpolar north pacific ocean and in the eastern south pacific both less than 100 cm2 s 2 in contrast to the north pacific the subpolar north atlantic ocean shows relatively enhanced ke eddy kinetic energy and eddy mixing appear to have declined during the last decade over large parts of the western pacific ocean in some regions by as much as 50 of the time mean value increased eddy variability can be found in the kuroshio and gulf stream

the role of fe and redox conditions in olivine carbonation rates an experimental study of the rate limiting reactions at 90 and 150 c in open and closed systems abstract the mechanisms and rates of olivine carbonation reactions have been the object of a number of studies but the thermodynamic limitations and the kinetics of the elementary processes that control the overall reaction are still poorly understood and characterized the main objective of this study is to probe the effect of fe on the measured rates of olivine carbonation and its role in the formation of si rich surface layers which can significantly inhibit olivine dissolution and limit the extent of the carbonation reaction a series of batch and flow through reactor experiments was conducted in pure water at 90 and 150 c and under a co 2 partial pressure of 100 and 200 bar using both a natural sample of fe bearing olivine fo 88 and a synthetic sample of pure forsterite fo 100 experimental results show that fe plays an ambivalent role in the carbonation rates of olivine on one hand the presence of fe favors the formation of fe si rich protective layers at the interface between olivine and aqueous solution slowing down the dissolution reaction and limiting the extent of carbonation whereas pure silica coatings have little to no inhibiting effect on measured carbonation rates on the other hand fe enhances olivine to carbonate conversion rates at low degrees of supersaturation by promoting the formation of fast precipitating mg fe carbonate solid solutions the passivating properties of fe si rich layers originate from the strong fe iii si interaction and are linked to the permanence of oxidizing conditions in the aqueous fluid as a consequence under reducing conditions olivine carbonation rates can be significantly increased by higher extents of dissolution and by the formation of ferroan magnesites mg fe co 3 which nucleate faster than the pure mg end member forsterite and olivine carbonation reactions can be hindered by the formation of secondary mg sheet silicates but at the conditions studied the formation of such silicate phases was observed to be transitional and not affecting significantly the rates of carbonation at the end of one month long experimental runs this work presents new measurements of olivine carbonation rates and delivers relevant information that suggest new reference criteria for the assessment of the sequestration potential of co 2 repositories and the optimization of the mineral carbonation process in mafic and ultramafic rocks

structure of the irian jaya mobile belt irian jaya indonesia image interpretation and field investigation over the central ranges of irian jaya has provided a structural overview of the inaccessible and largely unmapped irian jaya mobile belt ijmb in the region bounded by longitudes 136 30 e and 141 00 e throughout much of the southern para autochthonous part of the belt structural facing directions are visible on imagery through selective illumination of hogbacks and cuestas formed on thick bedded mesozoic siliciclastics and extensive late cretaceous neogene platform carbonate sequences north of the regional derewo fault zone the derewo metamorphics are regarded in part as correlatives of the metamorphosed om beds in western papua new guinea and display a regional structural grain parallel to the orogen the limited extent of spectrally anomalous features associated with ultramafic rocks indicate that ophiolites are confined to the southern part of the irian jaya ophiolite belt which may be largely composed of metamorphic rocks interpreted macroscopic and megascopic structures suggest the presence of seven discrete structural domains in the ijmb from north to south these are 1 north coast basin region consisting of paleogene neogene volcanics and sediments overlain by a pliocene pleistocene successor basin sequence 2 an allochthonous terrane composed of ophiolites and high grade metamorphic rocks 3 the derewo metamorphic assemblage displaying polyphase deformation 4 a complex marginal zone within mesozoic paleogene miogeoclinal sediments which includes steep duplex structures and remnant klippen 5 a 40 to 50 km wide partly inverted synclinorium composed of miogeoclinal sediments 6 a regional south vergent overturned anticlinorium formed by incompetent paleozoic sediments and 7 a foreland thrust domain involving both mesozoic cenozoic miogeoclinal cover and a deformed neogene foreland molasse basin sequence the regional disposition of interpreted structures in the irian jaya mobile belt and reference to published mapping in western irian jaya and western papua new guinea strongly indicates polyphase deformation late oligocene miocene docking of metamorphics island arc assemblages and ophiolites produced tectonically stacked e w trending structures thrust on to the north margin of the australian continent with its miogeoclinal cover late miocene pliocene collision with the melanesian arc brought the accreted australian margin into contact with the westward moving pacific plate and instituted a regime of oblique transpressional convergence resulting structures include e w sinistral wrenching and nw thrusts along lateral e w ramps

mineralogical and geochemical consequences of the long term presence of co2 in natural reservoirs an example from the springerville st johns field arizona and new mexico u s a abstract the springerville st johns co2 field in eastern arizona and western new mexico is one of more than a dozen gas fields developed within the colorado plateau and southern rocky mountain region extensive travertine caco3 deposits record a long history of co2 migration and leakage to the atmosphere the oldest travertine deposits may have formed during the initial filling of the co2 reservoir when groundwaters exsolved co2 upon reaching the surface the youngest travertine deposits are associated with springs on the floor of the little colorado river valley but travertine deposition appears to be insignificant today older deposits occur up to 325 m above the valley floor geologic relationships suggest travertine deposition began in the late pleistocene after volcanic activity ended at 0 3 ma most of the caco3 could have been derived from dissolution of the underlying limestones and dolomites interactions between the reservoir fluids and rocks were observed in core samples from one of the intervals that produced dry gas these reactions resulted in the dissolution of carbonate cements and detrital feldspars and the formation of dawsonite and kaolinite geochemical simulations suggest that the dawsonite could have been deposited when the co2 fugacity reached 20 bars and that the kaolinite formed as the co2 fugacity decreased corrosion of drill pipe by acidic waters and a pronounced hco3 anomaly above the co2 reservoir provide evidence of a continuing flux of co2 from depth co2 storage occurs primarily as dissolved carbonate species and as gas accumulations only a small percentage of the co2 was sequestered in secondary minerals

palladium platinum and gold distribution in porphyry cu mo deposits of russia and mongolia the porphyry cu mo deposits in the southern siberian craton and northern mongolia including subduction collision and rift related igneous series of early paleozoic to mesozoic age are all characterized by varying crustal contribution to their parent magmas and the presence of explosive breccias precious metal and associated element contents are reported for mineralized samples sulphide concentrates and chalcopyrite molybdenite flotation concentrates from porphyry cu mo intrusions of russia sora aksug and zhireken and mongolia erdenetiun obo average pge contents in rocks are 17 ppb pd and 22 ppb pt in the aksug deposit 13 ppb pd and 10 ppb detection limit pt in the sora 14 ppb pd and 21 ppb pt in the erdenetuin obo and 18 ppb pd and 28 ppb pt in the zhireken deposit average gold content in rocks is 61 ppb in the aksug deposit 17 ppb in the sora 21 ppb in the erdenetuin obo and 30 ppb in the zhireken deposit the highest average 2 3 ppm ag was recorded in the rocks of the sora deposit in general the precious metal distribution in the studied deposits has no apparent relationship with the alteration types the molybdenum content in rocks ranges between 1 and 128 ppm mo in the aksug deposit from 1 to 5400 ppm mo in the sora deposit from 2 to 755 ppm mo in the erdenetuin obo deposit and from 3 to 1530 ppm mo in the zhireken deposit the average copper content in rocks is 1540 ppm in the aksug deposit 460 ppm in the sora deposit 1460 ppm in the erdenetuin obo deposit and 220 ppm in the zhireken deposit the cu mo ratios are highest in the aksug and erdenetuin obo deposits and lowest in the sora and zhireken deposits the correlation matrix for selected major and trace element data on mineralized samples and sulphide concentrates 34 samples indicates that precious metals are associated with either chalcopyrite or molybdenite copper shows a strong positive correlation with au and pd r 0 91 while mo shows a strong positive correlation with pt r 0 98 in addition mo exhibits a strong positive correlation with w r 0 94 an interelement positive correlation between precious metals is 0 57 ag au the pd and pt contents of both chalcopyrite and molybdenite in flotation concentrates are low varying from 9 to 83 ppb pd and from 10 to 110 ppb pt the highest values recorded are 924 ppb pd in sulphide concentrates from the aksug deposit and 684 ppb pd and 299 ppb pt in sulphide concentrate from breccia of the zhireken deposit the highest gold content 5450 ppb au is in chalcopyrite flotation concentrate from the aksug deposit whereas in the majority of concentrates the gold content is in the order of a few hundreds parts per billion the relatively low contents and limited variation of the precious metal contents in the individual deposits of russia and mongolia point to the essential role of the composition of the source and composition of parent magmas

geological and geochemical controls on the silver content fineness of gold in gold silver deposits abstract a compilation of microprobe fineness data and a re evaluation of bullion production fineness data suggest that the gold fineness model of fisher 1945 can be updated and applied to a wide range of gold mineralised environments the major deposit classes are characterised by the overall average or range of deposits averages and total range of gold fineness values as follows archaean 940 780 1000 slate belt 920 800 1000 plutonic 825 650 970 porphyry 700 1000 650 1000 volcanogenic 650 850 520 870 epithermal 440 1000 0 1000 the archaean including witwatersrand slate belt and plutonic classes are characterised by a high and consistent average fineness and a narrow fineness range there is no clear subdivision within these classes according to deposit style or inferred genesis the porphyry volcanogenic and epithermal classes have a variable average deposit fineness and a wide total range of fineness values within these three classes higher fineness is typical of deposits in andesitic rather than rhyolitic volcanic settings deposits with cu au rather than cu mo or pb zn element associations and deposits with telluride or selenide minerals solubility calculations indicate that in all these environments gold and silver form the same aqueous species with agcl 2 dominating for silver and au hs 2 dominating for gold in all the environments the fluids transport an equal amount of gold and silver in the form of their bisulphide complexes therefore the observed gold fineness values can not be explained by the transporting mechanism only low silver in the ores and higher gold fineness values observed in the archaean plutonic and slate belt environments can be attributed to sulphidation as the dominant mechanism of ore deposition sulphidation of wall rocks destabilises only the bisulphide complexes of gold and silver in contrast epithermal volcanogenic and porphyry environments are characterised by a diversity of ore depositing mechanisms cooling boiling mixing which act alone or in combination and destabilise chloro and bisulphide complexes of gold and silver the high silver concentration in the ores low fineness values and large variation in the fineness values in these environments can be attributed to the complexities in the ore depositing mechanisms

minor and trace elements in bornite and associated cu fe sulfides a la icp ms studybornite mineral chemistry abstract in situ laser ablation inductively coupled mass spectroscopy la icp ms has been used to provide a baseline dataset on the minor element contents in hypogene bornite and accompanying cu sulfides from 12 deposits with emphasis on syn metamorphic cu vein systems in norway and skarn porphyry and epithermal systems in se europe bornite contains significant concentrations of both ag and bi especially in the vein and skarn deposits studied and has the potential to be a major ag carrier in such ores concentrations of up to 1 wt of both elements are documented measured concentrations appear to be independent of whether discrete ag and or bi minerals are present within the analyzed sulfide where bornite and chalcocite or mixtures of cu sulfides coexist ag is preferentially partitioned into chalcocite over co existing bornite and bi is partitioned into the bornite bornite is a relatively poor host for au which mimics ag by being typically richer in coexisting chalcocite most anomalous au concentrations in bornite can be readily tracked to micron and submicron scale inclusions but bornite and chalcocite containing up to 3 and 28 ppm au in solid solution can be documented selenium and te concentrations in bornite may be as high as several thousand ppm and correlate with the abundance of selenides and tellurides within the sample selenium distributions show some promise as a vector in exploration offering the possibility to track a fluid source bornite and chalcocite are poor hosts for a range of other elements such as co ni ga and ge etc which have been reported to be commonly substituted within sulfides hypogene bornite and chalcocite may have significantly different trace element geochemical signatures from secondary supergene bornite

palladium platinum and gold concentration in porphyry copper systems of greece and their genetic significance compilation of new and published data on precious metal and associated trace element contents in mineralized porphyry copper intrusions of greece indicates that the pd content in the potassic propylitic zone of the skouries deposit is relatively high ranging between 60 and 200 ppb average 110 ppb whereas in the porphyry copper intrusions of gerakario and pontokerasia it is very low 3 ppb pd the oxidized zone of fissoka op 65 exhibits low pd and cu contents but higher au te as pb and zn contents the pt content is much lower than pd in the porphyry copper intrusions studied the pd pt ratio in the skouries deposit ranges from 9 to 60 while it is much lower 2 in the mineralized samples from fissoka gerakario and pontokerasia a decrease of the pd content and pd pt ratio with increasing te as pb and zn content may indicate that the pd distribution in porphyry copper systems is effected by the evolution of the magma hydrothermal system also mineralogical and geochemical data on the skouries deposit coupled with textural relations between base metal sulphides pgm and au ag tellurides indicate that the main pd bearing mineral merenskyite is associated with the vein type chalcopyrite or bornite and was deposited during the main stage of mineralization the high magmatic oxidation state and the magmatic features of the hydrothermal system limited participation of meteoric portion in the skouries intrusion may be a strong control of its pd potential assuming that pd is mainly associated with chalcopyrite in the porphyry copper deposits the calculated pd from measured pd contents in chalcopyrite average 3300 ppb pd are relatively high and comparable to that in the chalcopyrite concentrate made after the processing of large composite drill hole samples 2400 ppb pd to 21 wt cu it is considered to be an encouraging economic factor for pd as a by product probably along with au although the main product is cu

global ocean circulation during 1992 1997 estimated from ocean observations and a general circulation model 1 a three dimensional oceanic state is estimated for the period 1992 1997 as it results from combining large scale ocean data sets with a general circulation model at the cost of increased computational load the estimation assimilation method is chosen specifically so that the resulting state estimate is consistent with the model equations having no artificial sources or sinks to bring the model into close agreement with observations its initial temperature and salinity conditions are permitted to change as are the time dependent surface fluxes of momentum heat and freshwater resulting changes of these control vectors are largely consistent with accepted uncertainties in the hydrographic climatology and meteorological analyses the assimilation procedure is able to correct for many of the traditional shortcomings of the flow field by changing the surface boundary conditions changes in the resulting flow field are predominantly on the gyre scale and affect many features that are often poorly simulated in traditional numerical simulations such as the strengths of the gulf stream and its extension the azores current and the anticyclonic circulation associated with the labrador sea tests of the results and their consistency with prior error assumptions show that the constrained model has moved considerably closer to the observations imposed as constraints but has also moved closer to independent data from the world ocean circulation experiment not used in the assimilation procedure in some regions where the comparisons remain indeterminate not enough ocean observations are available and it is difficult to ascribe the residuals to either the model or the observations although problems remain a useful first solution to the global time dependent ocean state estimation problem has been found the estimates will continue to improve through the evolution of numerical models computer power increases more data and more efficient estimation methods

archean gold mineralization and oxidized hydrothermal fluids sulfate minerals hematite and isotopically fractionated sulfides are relatively rare in rocks of archean age several archean au deposits however contain one or more of these features indicative of oxidized hydrothermal fluids they include hemlo mcintyre hollinger macassa lake shore and ross which are all in ontario canada and kalgoorlie in australia examples of lesser deposits are in hislop township and in the matachewan area ontario canada with the exception of hemlo these are quartz carbonate vein deposits spatially and temporally associated with felsic plutonism because metamorphic fluids and archean surface waters were mostly reducing the most feasible general source for the fluids was felsic magmas parent magmas were relatively oxidized hydrous and co 2 rich the oxidized character may have favored the incorporation of au into the partial melt and its partitioning into magmatic aqueous fluids high contents of co 2 are conducive to the separation of an aqueous fluid from magma at greater depth than otherwise fluid inclusion data support the formation of major archean au vein deposits at deeper crustal levels than more recent magmatic hydrothermal mineralization such as porphyry cu deposits co 2 rich fluids can unmix into two phases at relatively high temperatures and pressures a saline aqueous liquid and a low salinity h 2 o co 2 liquid this can cause partitioning of cl complexed base metals from other metals including au sb and as the extensive carbonatization around most deposits has consistent delta 13 c values in the range of juvenile magmatic co 2