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

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

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

porphyry and epithermal deposits in greece an overview new discoveries and mineralogical constraints on their genesis abstract greece hosts a variety of magmatic hydrothermal ore deposits prospects with porphyry and epithermal styles playing a major role in its total gold endowment these deposit types are mainly clustered in two areas the rhodope and attico cycladic massifs and formed from about 33 ma to the pleistocene as a result of back arc extension in the aegean sea metamorphic core complex formation and contemporaneous post subduction and arc magmatism in the serbo macedonian massif porphyry cu au deposits include skouries fisoka tsikara vathi and gerakario causative intrusives are oligocene to miocene granodiorites to monzonites gold and pge mineralization is associated with potassic alteration of the intrusives in the eastern rhodope massif and the ne aegean islands porphyry prospects occur at pagoni rachi konos hill myli melitena west thrace fakos sardes and kaspakas limnos island and stypsi lesvos island mineralization is associated with oligocene to miocene subvolcanics of calc alkaline to shoshonitic affinity feature of these prospects which they share in common with several porphyry au only systems is their shallow depth of emplacement the presence of potassic sodic calcic and or phyllic alteration a strong epithermal overprint their low cu content an extreme re enrichment the multistage introduction of au the presence of banded quartz veinlets and the local presence of tourmaline new discoveries of porphyry style mineralization at king arthur st philippos and aisymi increases the gold potential in west thrace high intermediate sulfidation epithermal au ag polymetallic deposits prospects overprint and or occur laterally from porphyry style mineralization where they are spatially associated with lithocaps of advanced argillic alteration high intermediate sulfidation au ag epithermal mineralization at perama hill mavrokoryfi and pefka in west thrace and at pterounda mesotopos and megala therma on lesvos island is controlled by steeply dipping extensional faults within volcanic rocks without any obvious genetic relationship to spatially related porphyry style mineralization polymetallic epithermal deposits and prospects contain critical and energy critical metals e g te se bi sb in ge and ga which may be considered as by products in the attico cycladic area porphyry mo w mineralization occurs as sheeted quartz veins and stockworks cutting a potassic to sericitic altered miocene granodiorite stock in the lavrion district bonanza grade au and or ag rich veins with epithermal affinities crosscut metamorphic rocks at lavrion and on syros tinos antiparos and anafi islands milos island is characterized by shallow submarine volcanic hosted is hs epithermal au ag te and base metal deposits antimony as ag au deposits prospects on chios samos and kos islands in the eastern aegean sea indicate the potential for carlin style mineralization in greece several factors played a role to the metal endowment of the aegean porphyry epithermal systems magma fertility in the source regions depth of emplacement of causative intrusives relative contribution of mantle versus crustal material redox state of subduction related magmas and physico chemical fluid conditions at the site of ore deposition

hydrothermal alteration and mineralization of the galore creek alkalic cu au porphyry deposit northwestern british columbia canada the late triassic galore creek porphyry district is the largest accumulation of cu au prospects in british columbia canada in terms of contained metal the principal economic resource is the central zone deposit it comprises three high grade centers the au rich north and south gold lenses and the cu dominated central replacement zone alteration footprints ore shells and porphyry intrusions in these centers dip 45 to 60 to the west in the north gold lens and southwest in the south gold lens and central replacement zone indicative of significant postmineral tilting this inclination created an oblique vertical expression of the central zone at surface and at depth providing a 700 m depth profile through the deposit galore creek is considered to be the end member of the silica undersaturated class of alkalic porphyry cu au deposits it displays a unique hydrothermal alteration footprint generally devoid of quartz veining despite the lack of crosscutting veins a paragenetic sequence of several discrete potassic and calcic alteration events has been established during main stage alteration two mineralization events occurred that formed the economic resource in the central zone highly oxidizing fluids derived from porphyritic syenite to monzonite intrusions produced initial potassic alteration and sulfide mineralization in the north gold lens and south gold lens cu au ore shells are characterized by a gold rich core dominated by bornite associated with hematite dusted orthoclase specular hematite and anhydrite the second period of hydrothermal activity caused brecciation and calcic alteration in the central replacement zone the calcic fluids formed hydrothermal cement grading from ti rich andraditic to grossularitic garnet in the core of the breccia to a diopside and magnetite dominated assemblage at the margins calcic alteration also formed in the surrounding host rock this alteration event was followed by potassic alteration and mineralization characterized by biotite anhydrite and chalcopyrite in the cu rich ore shell of the central replacement zone most of the au is hosted in bornite that is spatially associated with oxidized reddened rock units dominated by an alteration assemblage of orthoclase hematite specular hematite garnet anhydrite high grade cu in the central zone is related to abundant chalcopyrite that has commonly replaced an assemblage of biotite magnetite diopside this distinct spatial separation strongly suggests that the local redox environment within the wall rocks governed sulfide and gold distributions the switch from early au rich mineralization to late stage cu dominated mineralization appears to have been controlled by varying redox conditions within the magma the change from more oxidized alteration assemblages fe3 fe2 to more reduced assemblages fe3 fe2 is indicative of a change in oxidation potential that may have propelled sulfide saturation in the magma and thus the subsequent depletion of most of the au

nonlinear dynamic failure process of tunnel fault system in response to strong seismic event strong earthquakes and faults have significant effect on the stability capability of underground tunnel structures this study used a 3 dimensional discrete element model and the real records of ground motion in the wenchuan earthquake to investigate the dynamic response of tunnel fault system the typical tunnel fault system was composed of one planned railway tunnel and one seismically active fault the discrete numerical model was prudentially calibrated by means of the comparison between the field survey and numerical results of ground motion it was then used to examine the detailed quantitative information on the dynamic response characteristics of tunnel fault system including stress distribution strain vibration velocity and tunnel failure process the intensive tunnel fault interaction during seismic loading induces the dramatic stress redistribution and stress concentration in the intersection of tunnel and fault the tunnel fault system behavior is characterized by the complicated nonlinear dynamic failure process in response to a real strong seismic event it can be qualitatively divided into 5 main stages in terms of its stress strain and rupturing behaviors 1 strain localization 2 rupture initiation 3 rupture acceleration 4 spontaneous rupture growth and 5 stabilization this study provides the insight into the further stability estimation of underground tunnel structures under the combined effect of strong earthquakes and faults

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

subepithermal au pd mineralization associated with an alkalic porphyry cu au deposit mount milligan quesnel terrane british columbia canada at the mount milligan cu au porphyry deposit quesnel terrane british columbia canada barren and weakly mineralized late stage hydrothermal veins occur in volcanic rocks adjacent to zones of cu au porphyry mineralization and have overprinted the porphyry stage veins the earliest of the late stage hydrothermal veins are barren and consist of quartz pyrite carbonate chlorite tourmaline these veins are similar to transitional to late stage hydrothermal veins in other alkaline porphyry cu au deposits and we consider these to be the equivalent of transitional post porphyry pre epithermal quartz sericite pyrite veins in calc alkaline porphyry environments a later generation of volumetrically minor mineralized veins are composed of pyrite hg and as bearing quartz carbonate chlorite and contain early electrum arsenopyrite tetra hedrite tennantite platinum group element pge tellurides galena sphalerite barite and chalcopyrite as inclusions in pyrite and a later assemblage of electrum pge tellurides arsenides and antimonides galena sphalerite chalcopyrite and various au ag te bi minerals in annealed fractures and open space infillings in quartz and pyrite metal precipitation in these veins was temporally and spatially associated with the deposition and later recrystallization of pyrite primary fluid inclusions in quartz in the barren and weakly mineralized veins are two phase l v homogenize to liquid over a narrow range in t 170 270 c n 96 12 veins and show a wide range in salinity 4 2 wt nacl equiv to 28 7 wt cacl2 equiv when all samples are considered however individual veins show narrow ranges in salinity and homogenization temperature la icp ms analyses indicate that the fluids were highly enriched in as to 2 260 ppm sb to 230 ppm b to 5 400 ppm au 1 2 ppm and pd 0 5 1 ppm but depleted in cu 80 ppm compared to typical porphyry stage fluids metal ratios in the fluids overlap with bulk rock metal ratios in the mineralized veins the inclusions are interpreted to contain a contracted magmatic vapor produced by boiling that lost cu during the formation of porphyry stage veins at depth fluids show decreasing b as sb and increasing sr ca and salinity with time stable c o and h isotope analyses of vein minerals indicate that mixing of this magmatic fluid with meteoric water was not responsible for metal deposition rather metal precipitation was possibly the result of mixing of the magmatic derived fluid with a heated saline groundwater the precious and accessory metal mineralogy of the hydrothermal veins is similar to that found in low to intermediate sulfidation epithermal systems fluid inclusion microthermometry and chlorite thermometry constrain the approximate formation conditions of the veins between 200 and 1 500 bars and 240 and 280 c after the formation of the mineralized veins circulation of low salinity metal depleted fluids occurred these latest stage fluids may have formed by mixing of the saline magmatic fluid groundwater hybrid with meteoric water the results of this study suggest a genetic link between porphyry stage events and the deposition of au and pge in late stage veins in an alkalic igneous environment recognition of hydrothermal processes involving the transport of au pge as sb bi te b rich fluids in the subepithermal regimes implies that low sulfidation epithermal au deposits may have been present in the shallower parts of the magmatic hydrothermal complex and that there is potential for the discovery of pge rich epithermal veins in less deeply exhumed terranes on the other hand the formation of high grade low sulfidation epithermal au pge deposits may be prohibited if porphyry epithermal transitional fluids precipitate ore metals through mixing with groundwater prior to reaching the level where meteoric water mixing and epithermal boiling normally occur

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

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

mineralization u pb geochronology and stable isotope geochemistry of the lower main zone of the lorraine deposit north central british columbia a replacement style alkalic cu au porphyry the lower main zone of the lorraine alkalic porphyry cu au district bc canada is hosted in an intrusive complex that comprises pre and late mineral biotite pyroxenites monzonites and syenites some of the biotite pyroxenites have interstitial sulfides which appear similar to net textured sulfides in magmatic ore deposits however the pyroxenites have undergone several stages of hydrothermal alteration main stage mineralization produced sulfide zonation patterns consisting of a bornite chalcocite or bornite chalcopyrite core grading outward to domains of chalcopyrite chalcopyrite pyrite and a peripheral domain of pyrite with minor chalcopyrite syenite in the inner bornite chalcopyrite zone typically contains abundant turbid k feldspar 70 whereas syenite marginal to the bornite chalcopyrite core contains less k feldspar 50 70 indicating an increase in k metasomatism of syenites toward the core of the deposit main stage mineralization predominantly occurs as fine grained disseminated sulfides in syenite biotite pyroxenite and fine grained k feldspar biotite rock textural analyses have shown that 1 primary magmatic diopside in contact with sulfides has corroded and actinolite altered margins suggesting alteration of primary minerals 2 scalloped relicts of biotite and diopside occur as inclusions in sulfides implying that sulfides have replaced primary minerals and 3 the deposit scale sulfide zonation patterns overprinted numerous rock types including the biotite pyroxenites that contain interstitial sulfides these results provide evidence for replacement style mineralization at lorraine where primary magmatic biotite and diopside were totally or partially replaced by sulfide minerals during main stage alteration u pb zircon dates from pre and late mineral syenite dikes show that the timing of main stage mineralization occurred between 178 8 and 176 0 ma lorraine is hosted within the quesnel island arc terrane and mineralization and magmatism at lorraine postdate accretion of the quesnel terrane to ancestral north america by approximately 7 to 10 m y the lorraine deposit represents the youngest known alkalic cu au porphyry deposit within the quesnel terrane and appears to coincide with the last gasp of alkalic magmatism within the quesnel terrane during the mesozoic

sulfosalt melts evidence of high temperature vapor transport of metals in the formation of high sulfidation lode gold deposits in enargite gold high sulfidation vein deposits magmatic fluid is considered responsible for the transport of metals and sulfur into the depositional regime new data from field emission sem analyses of sulfosalt mineral assemblages primarily enargite and tennantite from el indio chile and summitville colorado provide direct evidence of high temperature deposition including the following 1 the preservation of delicate euhedral quartz assemblages in sulfosalts 2 a range of discrete sb rich sulfosalt quartz feldspar and flourapatite vug filling minerals and 3 symplectic sulfosalt chalcopyrite textures that are arguably quenched melts together these features indicate formation from the vapor phase at high temperatures furthermore euhedral quartz crystals from el indio contain high temperature vapor rich fluid inclusions combined these observations are interpreted as suggestive of deposition in response to vapor phase decompression within fracture arrays that may be considered the analogues of the feeder fractures beneath large low grade silver gold deposits such as yanacocha peru

precious metal distribution and fluid inclusion petrography of the elatsite porphyry copper deposit bulgaria the elatsite porphyry copper deposit occurs in an island arc setting hosted by late cretaceous monzonitic monzodioritic porphyry stocks which were emplaced into precambrian cambrian phyllites trace element data of the late cretaceous intrusive rocks suggest that they are i type volcanic arc granitoids two main ore mineral assemblages are distinguished 1 magnetite bornite chalcopyrite and 2 chalcopyrite pyrite the first one is linked to potassic propylitic and the second to phyllic argillic alteration minor ore minerals are hematite molybdenite sphalerite pyrrhotite marcasite hessite and solid solutions of linnaeite siegenite carrollite tetrahedrite tennantite clausthalite galena gold electrum and merenskyite moncheite precious metal contents are relatively high throughout the deposit but au pd and pt are concentrated more strongly in the magnetite bornite chalcopyrite assemblage average grades of au ag pd and pt calculated for the 0 33 cu ore body are 0 96 0 19 0 007 and 0 002 g t respectively analyses of flotation concentrates revealed 25 6 cu and ag au pd and pt contents of 33 0 13 6 0 72 and 0 15 g t respectively the copper mineralisation at elatsite took place at pressures of 120 to 300 bar corresponding to depths of formation of 1 to 3 km under hydrostatic conditions the precious metals were probably transported jointly as chloride complexes in highly saline magmatic hydrothermal solutions the fluids had temperatures of 340 to 700 c and salinities of 28 to 64 nacl and mixed with meteoric water

turbulent momentum and salt transport in the mixing zone of the elbe estuary measurements in the mixing zone of the elbe estuary were performed during three consecutive tidal cycles with three types of instruments a moored tripod with velocity and temperature conductivity light attenuation sensors a profiling sonde with similar sensors lowered from an anchored vessel and instrumented moorings acoustic travel time sensors were used for velocity measurements spectral analysis of 12 8 min pieces of the obtained time series gives results that are consistent with isotropic turbulence for part of the frequency space temporal changes of turbulent kinetic energy are correlated with tidal current velocity a retardation is found between changes in tidal current and turbulent energy not all shear stress terms are in similar phase with tidal flow mean gradients reynolds stress terms and turbulent salt flux terms are combined to determine eddy viscosity and eddy diffusion coefficients

the carpatho balkanides and adjacent area a sector of the tethyan eurasian metallogenic belt the tethyan eurasian metallogenic belt temb was formed during mesozoic and post mesozoic times in the area of the former tethyan ocean on the southern margin of eurasia with the afro arabian and indian plates to the south it extends from western mediterranean via the alps and southeastern europe through the lesser caucasus the hindu kush and the tibet plateau to burma and sw indonesia linking with the west pacific metallogenic belt the carpatho balkan region is one of the sectors of the temb characterized by some specific features the emplacement of ore deposits is related to a definite time interval and to specific tectonic settings such as

the mineralogy and mineral associations of platinum group elements and precious metals in the aurora cu ni au pge deposit northern limb bushveld complex abstract aurora is a platinum group element pge prospect hosted in the northern limb of the bushveld complex south africa it is one of only three deposits discovered in the northern limb so far to be hosted in the melanocratic leucocratic gabbroic cumulates of the main zone of the rustenberg layered suite aurora moorddrift and waterberg t zone deposits rather than in predominantly ultramafic rocks e g platreef the host cumulates at aurora have been divided into three principal units and they intrude the dolomites of the lower transvaal supergroup base metal sulphide bms mineralisation with pge is present in the leucogabbronorites and gabbronorites of unit 2 and in coarse grained gabbronorite veins which intrude the peridotites of unit 1 these veins contain up to 50 interstitial pyrrhotite pentlandite chalcopyrite pyrite unit 2 contains 1 3 pentlandite pyrrhotite chalcopyrite assemblages and 1 5 chalcopyrite pyrite pyrrhotite associated with hydrothermal alteration the pge content of aurora however is predominantly controlled by the presence of platinum group minerals pgm not bms la icp ms analysis of sulphides shows the bms in aurora have lower pge concentrations than other bushveld magmatic sulphides with pentlandite carrying much lower concentrations of pd average 23 ppm than the platreef or the merensky reef sem eds analysis of 26 sections characterised 995 platinum group minerals pgm and precious metal bearing minerals pmm with a total area of 27850 m2 and an average size of 28 2 m2 of the pgm and pmm identified in aurora 85 by area are pd te bi minerals with 6 pd te minerals 4 electrum and 3 ag te minerals along with minor pd bi pd as pt te bi pt as and pt s minerals that collectively comprise 2 of total area only 25 of the pgm and pmm in aurora are bms hosted with the rest hosted in silicates of the total pgm and pmm area 22 are hosted in alteration silicates quartz chlorite or actinolite in an alteration halo around sulphides unusually 52 of the pgm and pmm are spatially removed from bms instead hosted in alteration silicates and within cracks in primary silicates away from any bms this indicates a multi stage ore genesis model with hydrothermal remobilisation of pge important for ore formation the style and host rocks for mineralisation in the aurora deposit are fundamentally different from other deposits in the northern limb of the bushveld hosted in ultramafic rocks such as the platreef gnpa member deposits and the f zone of the waterberg deposit all of which contain a greater diversity of pgm and bms with higher precious metal contents the mineralisation most similar to aurora is the t zone of the waterberg deposit located to the north of aurora which been suggested to be an along strike equivalent of the aurora main zone mineralisation however despite strong similarities in pgm mineralogy and s isotope signatures there are significant differences in bms mineralisation and host lithology meaning it is unlikely they are directly linked stratigraphically at present it seems more likely that aurora and the waterberg t zone reflect similar fluid influenced processes operating in different parts of the main zone perhaps at different times and in different structural basins rather than a continuous mineralised zone along strike

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

supershear rupture on multiple faults for the mw 8 6 off northern sumatra indonesia earthquake of april 11 2012 1 we perform a back projection method to image the rupture propagation and short period energy release of the 2012 off northern sumatra earthquake mw8 6 using hi net data recorded in japan the results show a complex pattern of four conjugate faults over about 180 sec there is a striking correspondence between the lengths and orientations of our rupture pattern with the distribution of aftershocks each of the first three stages of the rupture corresponds to a clear lineation in the aftershocks with lengths of 200 to 400 km rupture speeds for several of the fault segments were very high about 5 km s and exceed the local s wave velocity this is the first example of an oceanic earthquake with supershear rupture speed

seismic moment ratio of aftershocks with respect to main shocks the empirical bath s law indicates that the earthquake process is self similar and provides an opportunity to estimate the magnitude of the largest aftershock subsequent to a main shock however the analysis of this relation is limited to a small magnitude range and also depends on the aftershock selection rules as an alternative we analyze in this paper the cumulative seismic moment of aftershocks relative to the main shock moment because i it is a physical quantity that does not only take the largest aftershock into account ii background activity can be considered and as a result estimations are less affected by selection rules and iii the effects of the catalog cut off magnitude can be corrected what leads to larger magnitude range for the analysis we analyze the global preliminary determination of epicenters u s geological society catalog combined with centroid moment tensor focal mechanisms and find that the seismic moment release of aftershocks is on average approximately 5 of the main shock seismic moment we show that the results can be well fitted by simulations of the epidemic type aftershock sequence model in particular we test whether simulations constrained by predictions of the static stress triggering model proposing a break of self similarity due to the finite seismogenic width are in agreement with observations our analysis shows that the observed dependency on the main shock magnitude as well as systematic variations with the main shock fault plane solution can be both explained by the constraints based on the static stress triggering

simulating earthquake rupture and off fault fracture response application to the safety assessment of the swedish nuclear waste repository abstract to assess the long term safety of a deep repository of spent nuclear fuel upper bound estimates of seismically induced secondary fracture shear displacements are needed for this purpose we analyze a model including an earthquake fault which is surrounded by a number of smaller discontinuities representing fractures on which secondary displacements may be induced initial stresses are applied and a rupture is initiated at a predefined hypocenter and propagated at a specified rupture speed during rupture we monitor shear displacements taking place on the nearby fracture planes in response to static as well as dynamic effects as a numerical tool we use the 3dimensional distinct element code 3dec because it has the capability to handle numerous discontinuities with different orientations and at different locations simultaneously in tests performed to benchmark the capability of our method to generate and propagate seismic waves 3dec generates results in good agreement with results from both stokes solution and the compsyn code package in a preliminary application of our method to the nuclear waste repository site at forsmark southern sweden we assume end glacial stress conditions and rupture on a shallow gently dipping highly prestressed fault with low residual strength the rupture generates nearly complete stress drop and an m w 5 6 event on the 12 km 2 rupture area of the 1584 secondary fractures 150 m radius with a wide range of orientations and locations relative to the fault a majority move less than 5 mm the maximum shear displacement is some tens of millimeters at 200 m fault fracture distance

bi melt formation and gold scavenging from hydrothermal fluids an experimental study abstract the role of polymetallic melts in scavenging ore components has recently been highlighted in the context of fluid poor metamorphosed ore deposits in contrast the role of polymetallic melts in systems dominated by hydrothermal fluids remains poorly understood using a simple au bi model system we explored experimentally whether such polymetallic melts can precipitate directly from a hydrothermal fluid and investigated the ability of these melts to scavenge au from the solution the experiments were conducted in custom built flow through reactors designed to reproduce a hydrothermal system where melt components are dissolved at one stage along the flow path e g bi was dissolved by placing bi minerals along the fluid path whereas melt precipitation was caused further along the flow path by fluid rock interaction bi rich melts were readily obtained by reaction with pyrrhotite graphite or amorphous fes when au was added to the system bi au melts with compositions consistent with the au bi phase diagram were obtained in the case of fluid reaction with pyrrhotite epitaxial replacement of pyrrhotite by magnetite was observed with textures consistent with an interface coupled dissolution reprecipitation reaction icdrr in this case the metallic melt precipitated as blebs that were localized at the replacement front or within the porous magnetite direct fractionation of bi au melts from a hydrothermal fluid or precipitation of a bi melt followed by partitioning of au from ambient fluid offer new pathways to the enrichment of minor ore components such as au without requiring fluid saturation with respect to a au mineral this mechanism can explain the strong geochemical affinity recognized between au and low melting point chalcophile elements such as bi in many gold deposits examples of deposits where such a model may be applicable include orogenic gold deposits and gold skarns contrary to models involving migration of polymetallic melts to explain element remobilization only small quantities ppm of polymetallic melts are required to affect the au endowment of a deposit via interaction with a hydrothermal fluid the experiments also show that micro environments can play a critical role in controlling melt occurrences for example reaction fronts developing via icdr reactions can promote melt formation as observed during the replacement of pyrrhotite by magnetite the associated transient porosity creates space for the melt and promotes melt fluid exchanges whereas the reaction front provides local geochemical conditions favorable to melt precipitation e g reduced low ah2s aq and catalytic surface

modeling of gold scavenging by bismuth melts coexisting with hydrothermal fluids the effect of gold scavenging by bismuth melts is investigated using equilibrium thermodynamic modeling of an aqueous solution mineral melt system the calculations for the au bi na cl s h o system performed at temperatures between 300 and 450 c demonstrate that au concentrations in the melt are several orders of magnitude higher than in the coexisting fluid indicating the possible formation of economic gold deposits from undersaturated aqueous fluids in which mineralization would not be expected in the absence of a bismuth melt the model applies to any deposit where a bi melt is stable and coexists with a hydrothermal fluid examples of such deposits are known from skarn intrusion related orogenic and volcanogenic massive sulfide vms gold systems in sulfur poor systems the partitioning curves presented here can be used directly to correlate the gold concentration in the fluid and the au grade in the ore e g escanaba trough vms deposit these results also illustrate important principles generally applicable to understanding magmatic hydrothermal and metamorphic deposits that may have contained significant volumes of more complex polymetallic melts

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

distribution of platinum group elements in magmatic and altered ores in the jinchuan intrusion china an example of selenium remobilization by postmagmatic fluids the division of platinum group elements pge between those hosted in platinum group minerals pgm versus those in solid solution in base metal sulfides bms has been determined for ores from the pge bearing ni cu rich jinchuan intrusion in northwest china all the bms are devoid of pt and ir and magmatic bms are also barren of rh these pge may have been scavenged by arsenic to form pgm during magmatic crystallization of the bms pd os and ru are recorded in bms and pd is predominantly in solid solution in pentlandite unlike the fresh magmatic ores in altered or serpentinized ores pd pgm are present froodite is hosted in magnetite formed during alteration of bms accompanied by sulfur loss and liberation of pd michenerite pd pt bite sperrylite ptas2 and au bearing pgm are located in altered silicates irarsite irass occurs mainly enclosed in bms padmaite pdbise identified at the junctions of magnetite and bms was the last pgm to form and locally partially replaces earlier non se bearing pgm we propose that padmaite formed under oxidizing conditions during late local remobilization of se from the bms se bearing pgm are rare and our review shows they are frequently associated with carbonate suggesting that pd and se can be mobilized great distances in low ph oxidizing fluids and may be precipitated on contact with carbonate s se ratios are used by researchers of magmatic ni cu pge ores to determine sulfur loss assuming se is immobile and representative of magmatic sulfur content this study shows that se as well as s is potentially mobile and this should be considered in the use of s se ratios

tectonic triggers for postsubduction magmatic hydrothermal gold metallogeny in the late cenozoic anatolian metallogenic trend turkey

fennoscandian earthquakes whole crustal rupturing related to postglacial rebound local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern fennoscandia these paleoearthquakes with fault lengths of up to 160 kilometers and average displacements of up to 15 meters were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation the fennoscandian faults were probably formed by single events that ruptured through most of the crust the largest event moment magnitude mw 8 2 was larger than other known stable continent earthquakes outside failed rifts or extended crust

isotope geochemistry of the northeast zone mount polley alkalic cu au ag porphyry deposit british columbia a case for carbonate assimilation mount polley is a late triassic 205 ma alkalic porphyry cu au ag deposit 226 3 thousand tonnes t cu 21 5 t au and 65 1 t ag hosted by silica undersaturated to silica saturated monzonitic intrusions of the mount polley complex located in british columbia canada the northeast ore zone at mount polley is hosted by magmatic hydrothermal breccia copper and precious metals occur in sulfide minerals primarily as coarse to fine grained breccia cement local wall rocks include equigranular to porphyritic diorite monzodiorite and monzonite alteration breccia cement and veins of the northeast ore zone formed in five paragenetic stages prebreccia stage 1 brecciation and main stage mineralization stage 2 late stage mineralization stage 3 unmineralized postbreccia dikes and veins stage 4 and epithermal style veins stage 5 intense pervasive k and fe metasomatism calcite and calc silicate alteration occurred prior to brecciation caused by the intrusion of megacrystic k feldspar phyric monzonite stage 2 fluids were silica undersaturated high temperature 350 c co2 enriched and of near neutral to alkaline ph potassic sodic and calc potassic assemblages precipitated with mineralization during stage 2 with moderate temperatures at the deposit periphery and in stages 3 and 4 evidence for more acidic and lower temperature conditions is preserved in stage 5 veins the 34ssulfide isotope compositions of stages 2 and 3 chalcopyrite pyrite and bornite range from 7 1 to 1 4 sulfur isotope compositions of anhydrite and gypsum are mostly between 6 2 and 9 8 these values together with the presence of hematite are consistent with deposition from an oxidized sulfate dominant high temperature magmatic hydrothermal fluid limited sulfur isotope geothermometry indicates that cu sulfides precipitated at temperatures from 480 to 250 c hydrothermal calcite occurs in all paragenetic stages at mount polley calcite 13c values range from 0 2 to 10 5 and 18o values from 4 0 to 20 9 the enriched c o isotope values are not consistent with simple precipitation from an entirely magmatic source of hydrothermal fluid interaction of the fluid and or magma with limestone is considered a likely process to explain the c and o isotope signature lead isotope data suggest mixing of mantle and crustal sources during mineralization main stage chalcopyrite and pyrite as well as late stage galena have 206 204pb values of 18 77 to 18 92 207 204pb of 15 56 to 15 59 and 208 204pb of 38 22 to 38 32 strontium isotope data 0 70331 0 70371 provide evidence of a strongly depleted mantle source of sr with minor crustal input epsilon nd values for main stage apatite range between 5 9 and 6 5 also indicating a depleted mantle source stage 5 carbonate 206 204pb values of 18 96 to 19 04 207 204pb of 15 57 to 15 59 and 208 204pb of 38 26 to 38 36 suggest superposition of an epithermal system onto the northeast ore zone potentially as late as 100 m y after breccia formation the data presented are consistent with the hypothesis that the silica undersaturated alkalic mount polley complex formed due to carbonate assimilation prior to mineralization this process can explain the 13c 18o isotope data calcite precipitation concurrent with cu au mineralization and silica undersaturation of the magma the co2 released during assimilation of carbonate also could have promoted magmatic hydrothermal brecciation silica undersaturated alkalic porphyry systems may preferentially form in arc terranes built on a carbonate bearing substrate

surficial geology indicates early holocene faulting and seismicity central sweden in sweden knowledge of the location and timing of glacially induced faulting and seismicity is critical to effective engineering of a long term nuclear disposal facility to improve understanding and modeling of the complex ice induced and tectonic stresses associated with glacially induced faulting field studies detailing the location and timing of movement of such structures are required although the fault has not been confirmed in the bedrock multi proxy surficial geologic evidence indicates that the recently discovered scarp in bollnas is such a structure machine excavated trenches across the scarp reveal landsliding down the scarp and in one location faulted and vertically offset fine grained glacial sediments the presence of water escape structures in trenches excavated on a topographic high strongly suggests a co seismic origin derived from earthquake magnitudes 5 5 numerous landslides in till exist in the region as well four slopes with landslides were examined in detail and the factors of safety for these slopes indicate stable conditions and suggest a seismic trigger basal radiocarbon dates from peat bogs located stratigraphically above the landslides provide minimum limiting ages for the co seismic landslides the oldest date indicates sliding prior to 10 180 calendar years before the present the proposed bollnas fault is 400 km south of the so called lapland fault province to date it is the southernmost confirmed glacially induced fault in sweden the results of this study are consistent with existing modeling results that indicate fault instability in this region of central sweden following deglaciation

insights into the liquid bismuth collector model through analysis of the bi au stormont skarn prospect northwest tasmania the liquid bismuth collector model has previously been proposed to explain the common association between gold and bismuth seen in many ore deposits and involves the scavenging of gold from hydrothermal fluid by liquid bismuth here textural relationships and temperature and chemical conditions of mineralization at the stormont bi au skarn prospect in northwestern tasmania are analyzed to investigate whether the liquid bismuth collector model can explain gold accumulation at this prospect the calc silicate skarn assemblage containing grandite hedenbergite actinolite magnetite epidote quartz and calcite suggests that initial metasomatism involved temperatures 400 to 500 c visible gold is associated with native bismuth bismuthinite maldonite galena and an unknown bi te s mineral native bismuth is directly associated with grandite which formed during initial stages of metasomatism this implies that bismuth would have precipitated from a hydrothermal fluid as a liquid heating experiments showed that bismuth alloy inclusions in garnet melt between temperatures of 250 and 288 c the mineralization setting at stormont and textural relationships suggest that gold was scavenged from hydrothermal fluids by liquid bismuth rhythmically zoned grandite crystals provide evidence for fluctuating hydrothermal fluid conditions which may have contributed to dissolution and reprecipitation of gold thus facilitating an ore zone refining process within the prospect this refining process is made possible by the tendency of liquid bismuth to scavenge gold from significantly under saturated fluids infiltrating gold undersaturated fluids can dissolve gold not in contact with bismuth which can then be preferentially redeposited upon encountering a bismuth droplet enhancing the correlation between the two elements a long lived and focused fluid flow system would maximize the efficiency of this ore zone refining process which is likely to be relevant to gold deposition at a range of deposit types

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

approach to estimating the maximum depth for glacially induced hydraulic jacking in fractured crystalline rock at forsmark sweden hydraulic jacking is a significant dilation of a fracture that occurs when the pore pressure within it exceeds the sum of the fracture s normal stress and tensile strength this phenomenon may occur during a glacial period because of changes in hydraulic and mechanical boundary conditions since hydraulic jacking may alter flow patterns and the transport capacity of the rock mass its possible effects on the long term performance of a nuclear waste repository should be considered we develop an approach to assess glacially induced hydraulic jacking in fractured crystalline rock and establish bounding estimates of the maximum jacking depth for the swedish nuclear fuel and waste management company s skb repository site at forsmark the pore pressure is estimated using mechanically uncoupled two dimensional poroelastic continuum models with hydraulic and mechanical conditions based on skb s reconstruction of the weichselian glaciation at this site 120 0kab p for warm based conditions the water pressure at the ice bed interface is set at 98 of the mechanical load whereas for glacial conditions with extensive proglacial permafrost the corresponding water pressure is set at a lower annual average value we demonstrate that the pore pressure within the uppermost kilometer of rock is mainly governed by the water pressure at the ice bed interface and that the mechanical impact of the ice load on the pore pressure is sufficiently small to be ignored given the current and estimated future stress conditions at forsmark hydraulic jacking is mainly of concern for subhorizontal fractures i e it is sufficient to consider situations when the pore pressure exceeds the vertical stress we conclude that hydraulic jacking at forsmark will be confined to the uppermost 200m of the rock mass

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

the baltic shield earthquakes abstract the baltic shield area is a low seismicity area with few seismic events exceeding m l 4 since 1979 dense regional seismic networks have been in operation and have allowed accurate location including focal depths and fault plane solutions of more than 200 earthquakes in the range m l 0 6 4 5 the location of the southern sweden seismicity shows that a long part of the protogine zone the border between the younger western and older eastern crustal rocks marks a change in seismic activity the focal depths of the earthquakes indicate three seismically different crustal layers upper crust 0 13 km in northern sweden 0 18 km in southern sweden middle crust down to 35 km and the seismically quiet lower crust the gutenberg b value is smaller for the middle crust than for the upper crust the fault plane solutions show that strike slip is dominant along the tornquist line the southwestern border of the baltic shield area normal faulting occurs in northern sweden reverse faulting is more common than normal faulting the stresses released by the earthquakes show a remarkable consistency considering the small sizes of the earthquakes the data are consistent with a n60w direction of the regional principal compression supporting the view that the baltic shield seismicity is related to plate tectonic processes rather than to uplift the spatial distribution of the baltic shield seismicity is consistent with a model in which the earthquakes are considered as sudden breakdowns of asperities of normally stably sliding faults aseismic sliding is estimated to be more than 20 000 times more extensive than seismic sliding the rate at which southern sweden presently deforms horizontally is estimated to be 1 mm yr

elastic stress relaxation a mechanism for opposite sense of secondary faulting with respect to a major fault abstract the motion along a major fault perturbs the local stress field and produces numerous secondary fractures among these the secondary fractures that have the opposite sense of motion with respect to the main fault are particularly intriguing for example the right lateral reverse motion of the ms 7 1 loma prieta earthquake of 18 october 1989 produced a series of left lateral normal fractures located in a narrow zone about 1 km in widt subparallel to the trace of the san andreas fault through a rigorous inversion of geodetic data associated with the earthquake that allowed the slip to vary on the rupture surface we studied the origin of the left lateral normal fractures by comparing the location orientation and slip sense of the observed fractures with the perturbed elastic stress field calculated from the estimated slip distribution of the earthquake the perturbed state of stress at the earth s surface is complex and the greatest principal stress changes from horizontal to vertical the area of left lateral tensile state of stress coincides with that of the observed left lateral normal fractures the magnitudes of the induced fault normal tensile stresses of 60 120 bars and left lateral fault parallel shear stresses of 0 4 bars in the area are large enough to produce the ground failures thus the observed left lateral normal fractures adjacent to the san andreas fault are interpreted to be related to coseismic elastic stress relaxation the same mechanism can also be used to explain the normal faulting in the upthrown blocks of the thrust faults which produced the 1980 el asnam algeria and the 1968 tokachi oki japan earthquakes

tectonic magmatic and metallogenic evolution of the tethyan orogen from subduction to collision abstract this paper reviews the tectonic magmatic and metallogenic history of the tethyan orogen from the carpathians to indochina focus is placed on the formation of porphyry cu mo au deposits as being the most characteristic mineral deposit type formed during both subduction and collisional processes in this region relatively little is known about the history of the paleotethys ocean which opened and closed between gondwana and eurasia in the paleozoic and few ore deposits are preserved from this period the neotethyan ocean opened in the permian early triassic as the cimmerian continental fragments the cores of turkey iran tibet and indochina rifted from the northern gondwana margin and drifted northwards these microcontinents docked with the eurasian margin at various points in the mesozoic and cenozoic and formed a complex archipelago involving several small back arc basins and remnants of the paleotethyan ocean the main neotethyan ocean and these smaller basins were largely eliminated by collision with india and africa arabia in the early eocene and early mid miocene respectively although neotethyan subduction continues beneath the hellenic arc and the makran the majority of porphyry type deposits are found in association with neotethyan subduction mainly in the mesozoic and paleogene and syn to post collisional events in the mid paleogene to neogene they are found throughout the orogen but some sections are particularly well endowed including the carpathians balkans rhodopes eastern turkey lesser caucasus nw iran se iran sw pakistan southern tibet and se tibet indochina other sections that appear barren may reflect deeper levels of erosion young sedimentary cover or lack of exploration although there may also be real reasons for low prospectivity in some areas such as minimal subduction e g the western mediterranean region or lithospheric underthrusting as proposed in western tibet over the last decade improved geochronological constraints on the timing of ore formation and key tectonic events have revealed that many porphyry deposits that were previously assumed to be subduction related are in fact broadly collision related some forming in back arc settings in advance of collision some during collision and others during post collisional processes such as orogenic collapse and or delamination of subcontinental mantle lithosphere while the formation of subduction related porphyries is quite well understood collisional metallogeny is more complex and may involve a number of different processes or sources these include melting of orogenically thickened crust previously subduction modified lithosphere including metasomatized mantle underplated mafic rocks or lower crustal arc plutons and cumulates or upwelling asthenosphere e g in response to delamination slab breakoff back arc extension or orogenic collapse the most fertile sources for syn and post collisional porphyry deposits appear to be subduction modified lithosphere because these hydrated lithologies melt at relatively low temperatures during later tectonomagmatic events and retain the oxidized and relatively metalliferous character of the original arc magmatism unusually metallically enriched lithospheric sources do not seem to be required but the amount of residual sulfide phases in these rocks may control metal ratios e g cu au in subsequent magmatic hydrothermal ore deposits relatively au rich deposits potentially form in these settings as observed in the carpathians e g rosia montan turkey kisladag copler and iran sari gunay dalli although the majority of syn and post collisional porphyries are cu mo rich and resemble normal subduction related deposits e g in the gangdese belt of southern tibet this similarity extends to the associated igneous rocks which being derived from subduction modified sources largely retain the geochemical and isotopic character of those original arc magmas while still retaining a broadly calc alkaline character these rocks may extend to mildly alkaline shoshonitic compositions and may display adakite like trace element signatures high sr y and la yb ratios reflecting melting of deep crustal garnet amphibolitic sources but they are otherwise hard to distinguish from normal subduction related magmas small post collisional mafic alkaline volcanic centers are common throughout the orogen but for the most part appear to be barren however similar rocks in other post subduction settings around the world are associated with important alkalic type porphyry and epithermal au cu deposits and the potential for discovery of such deposits in the tethyan orogen should not be overlooked

kinematics of the southern rhodope core complex north greece the southern rhodope core complex is a wide metamorphic dome exhumed in the northern aegean as a result of large scale extension from mid eocene to mid miocene times its roughly triangular shape is bordered on the sw by the jurassic and cretaceous metamorphic units of the serbo macedonian in the chalkidiki peninsula and on the n by the eclogite bearing gneisses of the sideroneron massif the main foliation of metamorphic rocks is flat lying up to 100 km core complex width most rocks display a stretching lineation trending ne sw the kerdylion detachment zone located at the sw controlled the exhumation of the core complex from middle eocene to mid oligocene from late oligocene to mid miocene exhumation is located inside the dome and is accompanied by the emplacement of the synkinematic plutons of vrondou and symvolon since late miocene times extensional basin sediments are deposited on top of the exhumed metamorphic and plutonic rocks and controlled by steep normal faults and flat ramp type structures evidence from thassos island is used to illustrate the sequence of deformation from stacking by thrusting of the metamorphic pile to ductile extension and finally to development of extensional plio pleistocene sedimentary basin paleomagnetic data indicate that the core complex exhumation is controlled by a 30 dextral rotation of the chalkidiki block extensional displacements are restored using a pole of rotation deduced from the curvature of stretching lineation trends at core complex scale it is argued that the rhodope core complex has recorded at least 120 km of extension in the north aegean since the last 40 my

linking mineral and fluid inclusion paragenetic studies the batman deposit mt todd yimuyn manjerr goldfield australia the quartz sulphide vein system of the batman deposit at the mt todd mine australia formed during east west extension of a north northeasterly trending structure system early in d2 during retrograde contact metamorphism associated with cooling of the tennysons leucogranite four distinct fluid inclusion types have been identified in gold bearing quartz sulphide veins of the deposit type i low to moderate salinity aqueous primary inclusions 1 to 20 wt nacl equivalent with small amounts of co2 type ii high salinity na ca cl aqueous secondary inclusions 35 to 50 wt total nacl cacl2 containing halite carbonate and trona daughter minerals and minor co2 ch4 vapour type iii liquid and vapour secondary fluid inclusions 28 to 34 or 17 to 18 wt nacl equivalent with ch4 vapour and discrete gold and bismuth grains and associated growth zones type iv vapour rich co2f ch4 secondary inclusions with minor nacl liquid n 20 wt nacl equivalent a consistency in bulk fluid composition suggests a common parent fluid and a common parent source for the fluid inclusions previous paragenetic and textural studies have established a sequence in sulphide and silicate precipitation the mineral paragenesis has been linked to the trapping chronology of types i iv fluid inclusions in order to constrain the fluid conditions during micro tectonism and the mineralising process the link is possible because two mineral phases exhibit a temporal genetic relationship with the formation of fluid inclusions 1 growth zones in simple open space quartz fill contain tourmaline crystals in intimate association with type i liquid vapour fluid inclusions 2 gold is intimately associated with bismuth in type iii vapour liquid fluid inclusions either as discrete inclusions within the trails or wetting the inclusions the progressive change in the composition of types i iv is consistent with the evolution of a retrograde contact metamorphic fluid in wall rock lithologies

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

2 hydrothermal ore deposits related to post orogenic extensional magmatism and core complex formation the rhodope massif of bulgaria and greece abstract the rhodope massif in southern bulgaria and northern greece hosts a range of pb zn ag cu mo and au ag deposits in high grade metamorphic continental sedimentary and igneous rocks following a protracted thrusting history as part of the alpine himalayan collision major late orogenic extension led to the formation of metamorphic core complexes block faulting sedimentary basin formation acid to basic magmatism and hydrothermal activity within a relatively short period of time during the early tertiary large vein and carbonate replacement pb zn deposits hosted by high grade metamorphic rocks in the central rhodopean dome e g the madan ore field are spatially associated with low angle detachment faults as well as local silicic dyke swarms and or ignimbrites ore formation is essentially synchronous with post extensional dome uplift and magmatism which has a dominant crustal magma component according to pb and sr isotope data intermediate and high sulphidation pb zn ag au deposits and minor porphyry cu mo mineralization in the eastern rhodopes are predominantly hosted by veins in shoshonitic to high k calc alkaline volcanic rocks of closely similar age base metal poor high grade gold deposits of low sulphidation character occurring in continental sedimentary rocks of synextensional basins e g ada tepe show a close spatial and temporal relation to detachment faulting prior and during metamorphic core complex formation their formation predates local magmatism but may involve fluids from deep mantle magmas the change in geochemical signatures of palaeogene magmatic rocks from predominantly silicic types in the central rhodopes to strongly fractionated shoshonitic bulgaria to calc alkaline and high k calc alkaline greece magmas in the eastern rhodopes coincides with the enrichment in cu and au relative to pb and zn of the associated ore deposits this trend also correlates with a decrease in the radiogenic pb and sr isotope components of the magmatic rocks from west to east reflecting a reduced crustal contamination of mantle magmas which in turn correlates with a decreasing crustal thickness that can be observed today hydrogen and oxygen isotopic compositions of the related hydrothermal systems show a concomitant increase of magmatic relative to meteoric fluids from the pb zn ag deposits of the central rhodopes to the magmatic rock hosted polymetallic gold deposits of the eastern rhodopes

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

aftershock triggering by complete coulomb stress changes 1 we examine the correlation between seismicity rate change following the 1992 m7 3 landers california earthquake and characteristics of the complete coulomb failure stress cfs changes cfs t that this earthquake generated at close distances the time varying dynamic portion of the stress change depends on how the rupture develops temporally and spatially and arises from radiated seismic waves and from permanent coseismic fault displacement the permanent static portion cfs depends only on the final coseismic displacement cfs diminishes much more rapidly with distance than the transient dynamic stress changes a common interpretation of the strong correlation between cfs and aftershocks is that load changes can advance or delay failure stress changes may also promote failure by physically altering properties of the fault or its environs because it is transient cfs t can alter the failure rate only by the latter means we calculate both cfs and the maximum positive value of cfs t peak cfs t using a reflectivity program input parameters are constrained by modeling landers displacement seismograms we quantify the correlation between maps of seismicity rate changes and maps of modeled cfs and peak cfs t and find agreement for both models however rupture directivity which does not affect cfs creates larger peak cfs t values northwest of the main shock this asymmetry is also observed in seismicity rate changes but not in cfs this result implies that dynamic stress changes are as effective as static stress changes in triggering aftershocks and may trigger earthquakes long after the waves have passed

the ug2 merensky reef interval of the bushveld complex northwest of pretoria northwest of pretoria the ug2 merensky reef interval overlies a critical zone lower zone sequence that contains numerous large blocks of floor material nevertheless individual layers can be correlated with equivalent units at crocodile river mine the rustenburg impala union and amandelbult sections concentrations of platinum group elements in two borehole intersections of the ug2 chromitite are 4 ppm over 1 2 m and 2 4 ppm over 2 2 m therefore bulk pge levels appear to be only moderately lower than those at western platinum mine this renders models explaining pge enrichment by upward percolating melt or fluids problematic the merensky reef although containing sulphides is only weakly mineralized with pge 0 6 ppm the ug2 pyroxenite is separated from the ug2 chromitite by a 15 m noritic layer the introduction of feldspathic cumulates between two units that elsewhere directly overly each other may be explained by the more evolved composition of resident magma in those parts of the chamber distally located with regard to a major feeder zone at union section it also suggests that the ug2 unit is a multiple rather than a single cyclic unit