a sulfur carbon oxygen and strontium isotope study of the volcanic hosted el soldado manto type copper deposit chile the essential role of bacteria and petroleum strata bound manto type copper deposits of chile are a major source of copper and some deposits e g mantos blancos el soldado contain as much metal as do large porphyry copper deposits elsewhere el soldado 200 mt 1 35 cu the largest manto type copper deposit in the coastal cordillera of central chile is hosted by the rhyodacite basalt upper member of the marine lower cretaceous lo prado formation paragenetic studies indicate that the deposit formed in two stages the first was a low temperature stage stage 1 130 125 ma in which liquid petroleum migrated from underlying carbonaceous shales into the overlying host volcanic rocks and abundant framboidal pyrite developed in a paleopetroleum reservoir a later hydrothermal stage stage 2 ca 103 ma introduced copper and replaced earlier pyrite to form chalcopyrite bornite and chalcocite ores this study presents isotopic data that support bacterial sulfur reduction as the process that formed the essential precursor stage 1 pyrite and the participation of basinal fluids in the hydrothermal second stage a wide range of 34s values for early stage 1 pyrite 11 1 to 28 0 supports the hypothesis that low temperature incomplete sulfate reduction from connate seawater sulfate and fe enriched oil field brines took place in a compartmentalized petroleum reservoir by bacterial sulfate reduction with the exception of a small proportion of cu fe sulfides with 34s values between 2 0 and 2 0 per mil the bulk of stage 2 cu fe sulfides replaced earlier pyrite and mimic the broad range in 34svalues 12 7 and 19 0 of stage 1 pyrite sulfur from early pyrite was recycled with no significant homogenization fractionation or addition of new sulfur and indicates the essential role of hydrocarbons and bacteria in the formation of the deposit the 13c values of gangue calcite vary between 4 2 and 20 2 per mil and reflect a mixing of various proportions of oxidized pyrobitumen derived organic and inorganic carbon from the mineralizing fluid pyrobitumen in the ores has 13c values of 30 to 26 per mil consistent with it being a residue of the original liquid petroleum 18o values of k feldspar in both ore and barren samples are similar 12 0 12 7 and are compatible with the fluids being of metamorphic rather than magmatic origin the similar 18o ranges of calcite 2 7 and k feldspar 0 7 suggest that they formed from the same hydrothermal fluid and that the fluid was in equilibrium with the host rocks the 87sr 86sr ratios in calcite of 0 7041 to 0 7051 reflect isotopic ratios inherited from the subaerial andesitic rocks that overlay the deposit where the ore forming fluids are thought to have originated

complete dynamic modeling calibration for the thurwieser rock avalanche italian central alps abstract few rock avalanches have been witnessed and no exact real time description is available the 2 5 m m 3 punta thurwieser rock avalanche september 2004 italian central alps is a unique event for which many quantitative observations have been gathered this is the first case ever of a natural rock avalanche being recorded on video and for which an almost exact value of the total time duration from initial detachment to final deposition is available the landslide travelled over 2 9 km from its source partially in a glacial environment the initial failure and the time for the complete evacuation of the source area were studied and assessed by a series of photos the mean front velocities along the path have been estimated from the video the final geometry and the characteristics of the deposit have been obtained by gps measurements aerial photos field surveys and laboratory tests a quasi 3d continuum dynamic analysis of the landslide motion has been performed assuming both a voellmy and a frictional rheology in the model dan 3d for the first time the landslide front velocities have been used for back analyses and calibration of the rheological parameters together with the final shape and thickness of the deposit and its developing extension the dynamic flow resistance parameters initially calibrated with dan were adopted and validated in dan 3d showing good consistency they are consistent with the existing database for calibrated landslides of similar type and scale flow velocities on the path segment underlain by glacial deposits up to 55 65 m s 1 are more accurately predicted by adopting a frictional rheology up to 50 55 m s 1 with zero pore pressure and a 26 friction angle than by a voellmy rheology up to 40 45 m s 1 both observations and modelling show that glacial ice plays a substantial role in increasing the rock avalanche mobility

a tale of amalgamation of three permo triassic collage systems in central asia oroclines sutures and terminal accretion the central asian orogenic belt records the accretion and convergence of three collage systems that were finally rotated into two major oroclines the mongolia collage system was a long n s oriented composite ribbon that was rotated to its current orientation when the mongol okhotsk orocline was formed the components of the kazakhstan collage system were welded together into a long single composite arc that was bent to form the kazakhstan orocline the cratons of tarim and north china were united and sutured by the beishan orogen which terminated with formation of the solonker suture in northern china all components of the three collage systems were generated by the neoproterozoic and were amalgamated in the permo triassic the central asian orogenic belt evolved by multiple convergence and accretion of many orogenic components during multiple phases of amalgamation followed by two phases of orocline rotation

geology and geochemistry of the early carboniferous eastern sawur caldera complex and associated gold epithermal mineralization sawur mountains xinjiang china abstract volcanic rocks associated with early carboniferous gold mineralization are well exposed in the eastern part of sawur mountains xinjiang china new results for these volcanic rocks recognize the eastern sawur caldera complex and broadly subdivide the volcanic magmatic activity into the three cycles and nine lithofacies the eastern sawur caldera complex consists of at least one elliptical andesite caldera associated with later and smaller circular andesite caldera mafic volcanic necks and mafic to felsic dikes the effusive rocks have a transitional character from calc alkaline to tholeiite range from porphyritic basalts basaltic andesites andesites to dacites are enriched in large ion lithophile elements lile and depleted in high field strength elements hfse relative to n morb with a pronounced negative nb anomaly chondrite normalized rare earth element ree patterns show enrichment in the light ree relative to heavy ree the volcanic rocks have near uniform initial 87sr 86sr 0 70335 0 70362 and 143nd 144nd 0 51254 0 51259 end 3 5 4 7 ratios these rocks originated from the partial melting of a subduction modified mantle wedge in a subduction setting the wedge represents an enriched morb mantle source with some transfer of subduction components to the wedge during the magmas formation crustal assimilation could have played a role in petrogenesis during the ascent of the magmas geochemical characteristics of these volcanic rocks are consistent with their formation in a subduction related tectonic setting during the early carboniferous a close spatial and temporal relationship exists between the volcanic rocks and hydrothermal gold mineralization in the sawur mountains intermediate to silicic volcanic rocks and or caldera fracture system host a number of gold deposits there is evidence for a direct genetic association i e the two processes are linked by the common mantle derived sources previous studies have suggested that ore forming fluids mainly derived from mantle this study indicates that a direct link exists between the formation of mantle magmas in subduction zones and the generation of epithermal gold deposits

porphyry copper mineralisation in the central srednogorie zone bulgaria the porphyry copper systems in the central part of the srednogorie zone bulgaria are represented by three major deposits elatsite medet and assarel and several smaller deposits and occurrences all of them within the panagyurishte ore district the hydrothermal systems are related to late cretaceous calc alkaline igneous complexes ore mineralisation is developed predominantly in the apical parts of subvolcanic and intrusive bodies as well as within the volcanic and basement metamorphic rocks several of the porphyry systems are spatially associated with shallow level intermediate and high sulphidation volcanic hosted epithermal deposits of economic importance such as the major gold copper mine at chelopech located 10 km from the elatsite porphyry copper deposit mineralisation processes in the porphyry deposits start with intensive hydrothermal alteration of the wall rocks k silicate alteration is characteristic for pre ore hydrothermal activity in all of them and it is located mostly in their central parts propylitic alteration is prominent in the medet and assarel deposits the assarel deposit is located in the central part of a palaeovolcanic structure and shows a large spectrum of pre ore alterations including propylitic sericitic and advanced argillic assemblages the initial stages of the hydrothermal systems are characterised by high temperatures 550 500 c and highly saline 50 20 wt nacl equiv and vapour rich fluids of likely magmatic origin the composition of the fluids gradually changes from h2o nacl fecl2 to h2o nacl kcl and h2o nacl dominated as the fluids cool react with wall rocks and may become diluted with meteoric water fe ti oxide mineral associations were formed early in all deposits later followed in the elatsite deposit by an assemblage of bornite chalcopyrite platinum group element pge phases co ni thiospinels ag and bi tellurides and selenides the main ore stage in all deposits is dominated by chalcopyrite pyrite associated with propylitic alteration at medet k silcate sericite alteration at elatsite and chlorite sericite alteration at assarel specific geochemical features of the ore systems are marked by precipitation of numerous fine grained mineral inclusions in chalcopyrite and pyrite palladoarsenide pd rammelsbergite cu ni sulpharsenides in elatsite co and ni pyrite carrolite vaesite sulvanite and colusite in medet enargite as sulvanite colusite goldfieldite wittichenite calaverite and aikinite in assarel native gold and electrum are observed as small grains except in elatsite where larger aggregates up to several millimetres are found molybdenite is present as small flakes within chalcopyrite or forms felted aggregates within thin quartz veinlets in the elatsite and medet deposits and very rarely at assarel thin veinlets of quartz galena sphalerite are found at the upper parts of the deposits supergene alteration of the primary sulphide minerals is developed in the assarel deposit where a thick blanket of secondary copper mineralisation chalcocite covellite has formed in the other two deposits secondary mineral associations cu and fe oxides and hydroxides are limited to near the surface differences in the deposits studied suggest that elatsite and medet are formed probably at deeper levels of the porphyry systems whereas assarel is developed at rather shallower and lower temperature conditions typical of the apical part of a subvolcanic body intruding its volcanic superstructure

investigation and dynamic analysis of the long runout catastrophic landslide at the shenzhen landfill on december 20 2015 in guangdong china at 11 40 a m december 20 2015 a catastrophic landslide occurred in shenzhen guangdong southeast china seventy seven people were killed and 33 buildings were buried or damaged which were in the direct path of the landslide at the guangming new district the landslide involved 2 73 million m3 of the municipal solid waste msw and had a horizontal runout distance of 1100 m over a vertical distance of 113 m which was equivalent to a fahrboschung of 6 and covered an area of 0 38 km2 basic post failure characteristics are described in this study dynamic simulation software danw and rheological models were used to simulate the runout behavior of the displaced landslide material in order to provide information for the hazard zonation of similar types of potential msw landslides the simulated results revealed that a combination of the frictional model and voellmy model is able to provide the best performance in simulating this landslide also the results showed that this landslide had a duration of about 50 s with a maximum velocity of 22 4 m s it was expected that these models and parameters could improve the accuracy of future hazard assessments of areas with geological topographical and climatic features similar to the shenzhen hong ao landfill

a model for the analysis of rapid landslide motion across three dimensional terrain a new numerical model for the dynamic analysis of rapid flow slides debris flows and avalanches has been developed the model is an extension of an earlier algorithm and is implemented using a nu

an intrusion related origin for cu au mineralization in iron oxide copper gold iocg provinces major cu au deposits of iron oxide copper gold iocg style are temporally associated with oxidized potassic granitoids similar to those linked to major porphyry cu au deposits stable and radiogenic isotope evidence indicates fluids and ore components were likely sourced from the intrusions iocg deposits form over a range of crustal levels because co2 rich fluids separate from the magmas at higher pressures than in co2 poor systems thereby promoting partitioning of h2o cl and metals to the fluid phase at deep levels the magma fluid system cannot generate sufficient mechanical energy to fracture the host rocks as in porphyry systems and the iocg deposits therefore form in a variety of fault related structural traps where the magmatic fluids may mix with other fluids to promote ore formation at shallow levels the iocg deposits form breccia and fracture hosted mineralization styles similar to the hydrothermal intrusive breccias and sulphide vein systems that characterize many porphyry cu au deposits the fluids associated with iocg deposits are typically h2o co2 salt fluids that evolve by unmixing of the carbonic phase and by mixing with fluids from other sources in contrast fluids in porphyry systems typically evolve by boiling of moderate salinity fluid to produce high salinity brine and a vapor phase commonly with input of externally derived fluids these different fluid compositions and mechanisms of evolution lead to different alteration types and parageneses in porphyry and iocg deposits porphyry cu au deposits typically evolve through potassic sericitic and intermediate and or advanced argillic stages while iocg deposits typically evolve through sodic calcic potassic and carbonate rich stages and at deeper levels generally lack sericitic and argillic alteration the common association of porphyry and iocg cu au deposits with potassic oxidized intermediate to felsic granitoids together with their contrasting fluid compositions alteration styles and parageneses suggest that they should be considered as part of the broad family of intrusion related systems but that they are typically not directly related to each other

geology and geochemistry of listwaenite related gold mineralization in the sayi gold deposit xinjiang nw china abstract the sayi gold deposit is part of the sartohay ophiolitic melange in west junggar xinjiang china and is hosted by listwaenite which was transformed from serpentinite in a shear zone via fluid rock reaction gold mineralization is hosted by mylonitized listwaenites and quartz veins within listwaenite lenses formed during shearing our study demonstrates that fluid concentrated au ag as sb cu cr ni and co during transformation from serpentinite to listwaenite and ductile deformation deformation due to shearing played an important role in focusing ore forming fluid along the shear zone gold mineralization accompanied formation of hydrothermal minerals in the following stages carbonate quartz pyrite cqp stage i mariposite gersdorffite gold mgg ii quartz carbonate pyrite qcp iii gold bearing quartz iv and dolomite calcite stage v geological characteristics of mgg in mylonitized listwaenite demonstrate that gold mineralization formed during the transition from ductile to brittle deformation which was followed by gold bearing quartz veins filling brittle fractures the au contents show a positive correlation with ag as cu and sb contents in mylonitized listwaenite samples consistent with the coexistence of native gold gersdorffite arsenian pyrite and chalcopyrite in mylonitized listwaenite pressure decrease due to hydraulic fracturing during the transition from ductile to brittle deformation induced gold deposition in the sayi deposit

paleoatmospheric consequences of co2 released during early cenozoic regional metamorphism in the tethyan orogen the eocene was the warmest epoch of the cenozoic with published estimates of eocene atmospheric co2 content ranging from two to six times the current value calculations of co2 consumption by silicate weathering show that co2 fluxes to the atmosphere of ca 1018 myr could account for inferred paleocene eocene atmospheric co2 contents and the resulting greenhouse effect would have contributed to eocene warmth extensive portions of the tethyan orogen underwent regional metamorphism culminating in the eocene prograde metamorphism may have been contemporaneous with the late paleocene global warming we calculated the amount of metamorphic co2 produced at depth in the himalayan orogen with data on the timing of the india asia collison duration of prograde regional metamorphism and proportions and bulk compositions of metamorphic co2 source rocks if co2 was generated at a constant rate over a 10 myr period of prograde metamorphism in the himalayan orogen we estimate that ca 1018 1019 moles myr of metamorphic co2 were produced at depth significant expulsion of metamorphic co2 to the atmosphere may have occurred by focused fluid flow along shear zones such as the extensive main central thrust in the himalayan orogen an additional ca 1018 myr could have been contributed by eocene regional metamorphism in the mediterranean tethys i e from the alps to turkey the extensive metamorphism associated with the india asia collision and the closing of tethys may have contributed to co2 greenhouse warming in the early to mid cenozoic

association of pyrobitumen with copper mineralization from the uchumi and talcuna districts central chile abstract pyrobitumen has been shown to be an essential component in formation of some chilean manto type strata bound copper deposits and its presence has been observed in a number of other deposits but has received limited investigation in this paper we present paragenetic and geochemical data from two central chilean manto type deposits from the uchumi and talcuna districts where solid pyrobitumen residual petroleum is intimately associated with copper sulfides pyrobitumen in the uchumi deposit occurs in pore space within the host conglomerates and is adjacent to a granitoid stock pyrobitumen predates bornite chalcocite mineralization and may have reduced subsequent mineralizing fluids pyrobitumen from the manto delirio deposit talcuna district fills the cores of early sphalerite veins and was partially replaced by later cu as mineralization pyrobitumen is petrographically intergrown with cu fe sulfides and light 13c values of gangue calcite indicates the interaction of pyrobitumen with the mineralizing fluid the presence of pyrobitumen within the ores of other manto type copper deposits in the lower cretaceous basin of chile suggests that degraded petroleum reservoirs in particular if biodegradation generated authigenic pyrite can be important controls for metallic mineralization derived from hydrothermal solutions of different sources

jurassic mesothermal gold mineralization of the samhwanghak mine youngdong area republic of korea constraints on hydrothermal fluid geochemistry jurassic 166 or 2 ma gold vein deposits of the samhwanghak mine youngdong area are examples of mesothermal gold deposits in the republic of korea the deposits are composed of gold bearing but relatively sulfide poor massive quartz veins which occupy shear zones in graphite bearing paragneiss of precambrian age vein quartz was deposited mostly prior to deposition of sulfides and gold and contains three main types of fluid inclusions i co 2 ch 4 fluids ii low salinity 2 kbars initial hydrothermal fluids were near their critical states at temperatures of 410 degrees to 480 degrees c and were homogeneous compositionally with x sub co 2 ch 4 of 0 45 x sub ch 4 0 14 and salinity of asymp 9 wt percent nacl type iii inclusions appear to be secondary and represent later fluids which formed through extensive fluid unmixing of type ii fluids with progressive decreases in temperature below 370 degrees c and pressure down to asymp 1 kbar but may also include deep circulating meteoric waters thermochemical calculations indicate the following evolution of hydrothermal fluids fugacity of sulfur decreased progressively with decreasing temperature near the pyrite pyrrhotite sulfidation curve fugacity of oxygen was controlled largely through graphite fluid interaction and evolved near the qfm buffer ph was maintained near neutrality temperature versus f sub o 2 relationships indicate that hydrothermal fluids were derived originally from a nearby s type magma the middle jurassic kimcheon granite gold occurs as gold rich avg 72 at au electrum intimately associated with sulfide minerals and precipitated from later aqueous type iii fluids at temperatures of 340 degrees to 240 degrees c as a combined result of cooling and decrease of sulfur activity by sulfide precipitation and or h 2 s loss accompanying fluid unmixing calculated sulfur isotope compositions of hydrothermal fluids delta 34 s sub sigma s near 2 per mil indicate that ore sulfur was derived from an ilmenite series s type granitic melt measured and calculated oxygen and hydrogen isotope compositions of ore fluids delta 18 o water 6 1 8 4ppm delta d water 62 to 72ppm are consistent with derivation from and interaction with magmatic rocks mesothermal gold vein deposits of the youngdong area were formed by extensive fracturing and veining during the jurassic daebo orogeny and developed from fluids that may have included an important component of magmatic fluids mineralogy and ore fluid chemistry of the deposits of the youngdong area are similar to those of archcan mesothermal gold vein deposits possibly validating a more general application of a magmatic hydrothermal model for the formation of mesothermal gold vein deposits

rb sr k ar and stable isotope evidence for the ages and sources of fluid components of gold bearing quartz veins in the northern sierra nevada foothills metamorphic belt california gold bearing quartz veins occur in and near major fault zones in deformed oceanic and island arc rocks west of the main outcrop of the sierra nevada composite batholith veins typically occupy minor reverse faults that crosscut blueschist to amphibolite grade metamorphic rocks whose metamorphic ages range from early paleozoic to jurassic vein micas and carbonate quartz mica assemblages that formed by hydrothermal metasomatism of ultramafic wall rocks in the alleghany grass valley washington and mother lode districts yield concordant k ar and rb sr ages the dated veins are significantly younger than prograde metamorphism penetrative deformation and accretion of their host rocks to the continental margin new and previously published mineralization ages from 13 localities in the sierra foothills range from about 140 to 110 m y ago with mean and median between 120 and 115 m y the age relations suggest that mineralizing fluids were set in motion by deep magmatic activity related to the resumption of east dipping subduction along the western margin of north america following the late jurassic nevadan collision event co 2 bearing fluids responsible for metasomatism and much of the vein mica carbonate albite and quartz deposition in several northern mines were isotopically heavy delta 18 o asymp 8 14ppm delta d between about 10 and 50ppm and do not resemble seawater magmatic or meteoric waters metasomatic and vein filling mica dolomite magnesite and quartz in altered ultramafic rocks generally formed from fluids with similar sr and o isotope ratios at a given locality consistent quartz mica delta 18 o fractionations delta 18 o sub q m 4 5 4 9ppm from various localities imply uniform equilibration temperatures probably between 300 degrees and 350 degrees c on a local mine scale fluids responsible for both carbonate alteration of mafic and ultramafic wall rocks and albitic alteration of felsic and pelitic rocks had similar sr isotope ratios samples from three veins in the central alleghany district fit a 115 7 or 3 m y rb sr isochron with a 87 sr 86 sr i value of approximately 0 7119 inferred 87 sr 86 sr ratios of metasomatic fluids from mines in different parts of the foothills region vary considerably 0 704 0 718 suggesting that sr was derived from sources ranging from western assemblage mesozoic ophiolitic or arc volcanic rocks to early paleozoic continent derived clastic rocks of the shoo fly complex systematic geographic variations in both sr and o isotopes can be rationalized by assuming extensive fluid interaction with rocks similar to the ones that are exposed within a few kilometers of the veins but the ultimate sources of the fluids and of au and other constituents may be independent of these isotopically lighter meteoric fluids deposited some late quartz overgrowths and occupied secondary fluid inclusions in earlier vein quartz

metamorphic origin of ore forming fluids for orogenic gold bearingquartz vein systems in the north american cordillera constraints froma reconnaissance study of δ15n δd and δ18o the western north american cordillera hosts a large number of gold bearing quartz vein systems from the mother lode of southern california through counterparts in british columbia and southeastern alaska to the klondike district in central yukon these vein systems are structurally controlled by major fault zones which are often reactivated terrane bounding sutures that formed in orogens built during accretion and subduction of terranes along the continental margin of north america mineralization ages span mid jurassic to early tertiary and encompass much of the evolution of the cordilleran orogen nitrogen contents and 15n values of hydrothermal micas from veins are between 130 and 3 500 ppm and 1 7 to 5 5 per mil respectively these values are consistent with fluids derived from metamorphic dehydration reactions within the phanerozoic accretion subduction complexes which have 15n values of 1 to 6 per mil the 18o values of gold bearing vein quartz from different locations in the cordillera are between 14 6 and 22 2 per mil but are uniform for individual vein systems the d values of hydrothermal micas are between 110 and 60 per mil ore fluids have calculated 18o values of 8 to 16 per mil and d values of 65 to 10 per mil at an estimated temperature of 300 c d values of ore fluids do not show any latitudinal control these results indicate a deep crustal source for the ore forming fluids most likely of metamorphic origin low dh2o values of 120 to 130 per mil for a hydrous muscovite from the sheba vein in the klondike district reflect secondary exchange between recrystallizing mica and meteoric waters collectively the n h and o isotope compositions of ore related hydrothermal minerals indicate that the formation of these gold bearing veins involved dilute aqueous carbonic and nitrogen bearing fluids that were generated from metamorphic dehydration reactions at deep crustal levels these data are not consistent with either mantle derived fluids or granitoid related magmatic fluids nor do they support a model involving deeply circulated meteoric water

mineralogic fluid inclusion and stable isotope studies of several gold mines in the mother lode tuolumne and mariposa counties california gold bearing quartz veins in the southern part of the mother lode california formed from fluids which contained si k co 2 ca s and metals and which were focused into permeable fault zones in the coulterville district of the mother lode these fluids altered serpentinite to a talc chlorite magnesite quartz assemblage which is crosscut by veins containing quartz dolomite sericite sulfides tellurides and gold textural relationships among the vein filling minerals reveal that galena tellurides pb ni ag au ag and native gold precipitated last among the vein minerals observations from the oro rico and mcalpine mines coulterville district indicate that these deposits were subjected to deformation during and after their formation fluid inclusions in the milky vein quartz exhibit only a narrow range in t sub m ice but a large range in t h which probably reflects posttrapping deformation microthermometry of fluid inclusions from vug filling quartz in the alleghany district in the northern portion of the mother lode reveals low salinity 2 h 2 o fluids with t sub mco 2 56 7 degrees c t sub m clathrate 9 5 degrees c and t sub h total 150 degrees to 200 degrees c visual estimates of co 2 content indicate a maximum of 10 mole percent co 2 in contrast inclusions from vug filling quartz in the coulterville district are filled with low salinity low t h 110 degrees 140 degrees c h 2 o rich fluids which were probably later than and unrelated to the gold mineralizing fluids oxygen isotope values of vein quartz from the southern mother lode indicate formation by 18 o enriched fluids in the range 6 to 11 per mil vs smow these values are similar to estimates of 8 to 15 per mil from vein quartz of the alleghany district taylor 1981 boehlke and kistler 1986 the average delta 13 c values for magnesite and dolomite of 4 5 or 0 6 per mil vs pdb from the southern mother lode are identical to results from the alleghany district 200 km to the north rosenbaum and taylor 1984 these data suggest either a single or well mixed source of oxidized carbon for the fluids oxygen isotope compositions of magnesite calculated using an experimentally derived phosphoric acid fractionation factor at 50 degrees c of 1 0096 are enriched in 18 o relative to coexisting dolomite as predicted for isotopic equilibrium the chemistry of the mother lode ore forming fluids is characterized by several approaches with an x sub co 2 estimate of 0 1 from fluid inclusions quartz magnesite assemblages in the coulterville serpentinite alteration zones limit the temperature of formation to below 325 degrees c for p 2 h 2 o fluid coupled with the assumption of trapping temperatures of 300 degrees c suggests minimum trapping pressures of 1 000 to 2 000 bars assuming equilibrium the assemblage of daughter minerals described by coveney 1981 indicates neutral ph conditions of 5 5 to 6 0 at the prevailing p t conditions sulfide mineral stabilities imply that h 2 s was the dominant sulfur species and that a sub o 2 of the mineralizing fluids was in the range 10 super 32 to 10 super 35 our preferred model for the formation of the mother lode vein system involves magmatic activity associated with a subducting slab in this model generation of ore forming fluids is possible by a variety of mechanisms including metamorphic devolatilization reactions in rocks adjacent to the plutons direct magmatic input and deep circulation of meteoric water any of these mechanisms is possible given the available data on the mother lode deposits

modeling fluid transfer along california faults when integrating pressure solution crack sealing and compaction processes 1 several models pertaining to earthquake cycles imply intermittent fluid flow through fault during the interseismic period increase in fluid pressure from hydrostatic to lithostatic values is a crucial parameter in mechanisms leading to earthquakes to achieve such pressures geodynamic processes gouge compaction fluid flow and changes in permeability are required previous models have postulated that changes in permeability by self healing are faster than the effects of geodynamic processes we consider the different mechanisms and rates of crack sealing near active fault on the examples of uplifted californian faults we find that natural crack sealing is normally not achieved by a rapid self healing process pressure solution with mass transfer from solution cleavage to cracks appears to be a more important mechanism for crack sealing and creep during postseismic deformation the geometry of transfer path and experimental data have been used to model crack sealing rates by pressure solution which are estimated to be rather slow similar to the recurrence time of some earthquakes such slow changes in permeability may be crucial factors in controlling the increase in fluid pressure and consequently the mechanism of critical failure in faults then numerical modeling of fluid pressure and transfer around active faults has been performed integrating a slow change in permeability by crack sealing gouge compaction and fluid flow from depth this modeling shows various location and evolution of fluid overpressure during the interseismic period depending on these processes and allows one to estimate the amount of fluid transferred from depth during interseismic periods

from serpentinization to carbonation new insights from a co2 injection experiment abstract we injected a co2 rich hydrous fluid of seawater chlorinity into an ongoing mildly reducing h 2 a q 3 mmol kg serpentinization experiment at 230 c and 35 mpa to examine the changes in fluid chemistry and mineralogy during mineral carbonation the chemistry of 11 fluid samples was measured speciated and compared with mgo sio2 h2o co2 mshc phase equilibria to approximate the reaction pathway from serpentinization to carbonation although the overall system was in apparent disequilibrium the speciated activities of dissolved silica a sio 2 a q and carbon dioxide a co 2 a q evolved roughly along mshc equilibrium phase boundaries indicative of 4 distinct mineral assemblages over time 1 serpentine brucite magnesite before the injection to 2 serpentine talc magnesite 2 h after the injection to 3 quartz magnesite 48 h after injection and 4 metastable olivine magnesite 623 h after injection until the experiment was terminated inspection of the solid reaction products revealed the presence of serpentine magnesite minor talc and magnetite in addition to relict olivine although quartz was saturated over a short segment of the experiment it was not found in the solid reaction products a marked and rapid change in fluid chemistry suggests that serpentinization ceased and precipitation of magnesite initiated immediately after the injection a sharp decrease in ph after the injection promoted the dissolution of brucite and olivine which liberated sio 2 a q and dissolved mg dissolved mg was efficiently removed from the solution via magnesite precipitation whereas the formation of talc was relatively sluggish this process accounts for an increase in a sio 2 a q to quartz saturation shortly after the injection of the co2 rich fluid molecular dihydrogen h 2 a q was generated during serpentinization of olivine by oxidation of ferrous iron before the injection however no additional h 2 a q was generated after the injection speciation calculations suggest a strong affinity for the formation of methane ch 4 a q at the expense of co 2 a q and h 2 a q after the injection but increased ch 4 a q formation was not observed these findings suggest that kinetically fast mineral carbonation dominates over sluggish ch 4 a q formation in mildly reducing serpentinization systems affected by injection of co2 rich fluids

carbonate sulfide equilibria and stratabound disseminated epigenetic gold mineralization a proposal based on examples from alleghany california u s a abstract stratabound disseminated pyritic au ore bodies were produced by reactions between wall rocks and through flowing fluids in mesozoic epigenetic au quartz vein systems in the sierra nevada metamorphic belt equilibrium relations among fe bearing carbonate and sulfide minerals were critical in determining which rock types were likely to host disseminated mineralization along portions of discordant veins the compositions of metasomatic carbonates in hydrothermally altered wall rocks at alleghany california u s a were larely predetermined by the relative proportions of fe mg and ca in the unaltered wall rocks thus coexisting solid solutions in the magnesite siderite and dolomite ankerite series from a variety of different wall rocks yield an empirical phase diagram for a large part of the ca co 3 mgco 3 feco 3 system at the temperature of metasomatism 325 50 c because fe mg silicates were unstable in alteration zones adjacent to the veins wall rock fe was partitioned between carbonates and sulfides pyritization and disseminated au mineralization occur in a variety of igneous and metasedimentary wall rocks in which the initial molar fe fe mg 0 5 in altered wall rocks with initial molar fe fe mg 0 5 fe was incorporated almost entirely within mg rich carbonates x feco 3 0 6 in magnesite siderite solutions it is proposed that the co 2 rich vein fluid responsible for the alteration and mineralization was partially buffered with respect to h 2 s co 2 h 2 ratios by equilibrium between pyrite and mg 0 4 fe 0 6 co 3 graphite as it traversed and altered intermediate volcanic and sedimentary rocks this fluid then locally reacted with lower fe fe mg rocks to form fe bearing dolomite magnesite assemblages and reacted with higher fe fe mg rocks to form ankerite pyrite assemblages gold precipitated from saturated solutions of bisulfide complexes partly in response to fluid desulfidation and reduction caused by the pyritization reactions in terranes dominated by intermediate metavolcanic and metasedimentary rocks favorable host rocks for this type of mineralization need not have high fe contents but do require high fe fe mg ratios they may include felsic volcanic and plutonic rocks fe rich tholeiitic differentiates banded fe formations and a variety of siliceous and argillaceous sedimentary rocks rocks which tend not to be heavily sulfidized because they have low initial fe fe mg ratios include ultramafic and mafic igneous rocks and some argillaceous sedimentary rocks exploration guidelines based on these principles may be useful elsewhere in the sierra nevada and in other comparable heterogeneous metamorphic terranes if modified to reflect the dominant buffering rock types in a given fluid flow path carbonate sulfide equilibria are capable of approximately buffering the carbonate sulfide ratios of co 2 rich vein fluids f co 2 10 2 8 at 325 c 200mpa or 2000 bar the alleghany fluid f co 2 10 3 2 or 10 mol co 2 had a molar co 2 h 2 s ratio of approximately 10 3 assuming graphite saturation at lower co 2 fugacities fe bearing silicates entered the buffering assemblages carbonatization reactions could potentially de sulfidize some wall rocks releasing s and associated metals to the fluid this would be most likely to occur in pyrite bearing mafic and ultramafic rocks and some argillites

dynamic modelling of entrainment in rapid landslides entrainment of path material is an important feature of many rapid landslides the associated increases in volume and changes in flow character can significantly influence mobility a simple material entrainment algorithm based on the assumption of natural exponential growth with displacement has been incorporated into a new computer model designed to simulate rapid landslide motion across 3d terrain the user controls the growth rate and can also implement a change in rheology at the onset of entrainment a hypothetical example is used to demonstrate the influence of the mass and momentum transfer assumptions a back analysis of the 1999 nomash river landslide is included to show that the simple model is capable of simulating the bulk characteristics of a complex event involving substantial entrainment key words landslides debris flows rock avalanches entrainment erosion dynamic modelling

high grade metamorphic processes which influence archaean gold deposits with particular reference to big bell australia mineralogical and geochemical evidence indicates that partial melting and desulphidation have occurred in the big bell gold deposit decarbonation may also have occurred to account for the lack of a carbonate alteration halo this is compatible with the present data but difficult to test the big bell deposit consists of auriferous sulphide bearing lode schists with muscovite and k feldspar and surrounding biotite schists all derived by intense premetamorphic alteration of rocks of mafic composition assemblages which include cordierite sillimanite k feldspar garnet biotite quartz suggest peak metamorphic conditions of 4 5 kbar and 650 700 c based on phase relations geobaro meters and garnet biotite fe mg exchange partitioning partial melting occurred at peak metamorphism particularly in the altered mafic rocks in and around the deposit and its occurrence may have been essential to the preservation of the deposit melting greatly limited the importance of devolatilization reactions resulting in negligible aqueous fluids and no means of removing appreciable gold minor gold loss may have accompanied desulphidation a diversity of complex metamorphic assemblages occurs around the mine compared to the assemblages developed regionally variable bulk rock composition influences this contrast but there is no evidence of higher metamorphic grades at the mine nor that this might have been the prime control on the different assemblages in this narrow belt it is suggested that the big bell and hemlo deposits are the higher metamorphic grade equivalents of the more abundant greenschist facies gold deposits within archaean greenstone belts this interpretation is favoured by the host rock setting and geochemical characteristics of big bell alternative models that suggest that this class of deposit is a new type must account for the absence of high grade equivalents of the greenschist facies deposits and also the lack of low grade equivalents of the big bell hemlo type archaean gold deposits in high grade metamorphic terrains have undergone a series of processes that are not recorded in the more typical gold deposits of the greenschist facies

prediction of hidden au and cu ni ores from depleted mines in northwestern china four case studies of integrated geological and geophysical investigations integrated geological and geophysical investigations were carried out in 26 active mines in northwestern china during the period 2001 2006 to explore for hidden extensions of known ore bodies and to search for new mineralization this paper presents four case studies from northwest china the kuoerzhenkuoa volcanogenic hydrothermal gold deposit the nanjinshan breccia associated gold deposit the duolanasayi deposit associated with a ductile shear zone and the hulu magmatic cu ni sulfide deposit in these studies detailed mine scale geological studies were carried out to determine the location and controls on ore formation based on these investigations and a review of previous exploration data genetic models for the deposits were evaluated and specific new targets were generated these target areas were tested with surface geophysical surveys using the stratagem eh4 system a hybrid source magnetotellurics mt method analysis of the data obtained in the surveys identified geophysical target anomalies that were subsequently drilled many of these test holes demonstrate the presence of au and cu ni mineralization evaluation of the geological models was crucial in developing conceptual targets as a basis for surface geophysical surveys these models established the most likely target areas where au and cu ni mineralization could occur but they did not define the limits or the geometries of the mineralized zones hybrid mt surveys played an important role in defining the location of buried mineralized systems and in testing the validity of the conceptual targets the resistivity cross sections obtained by imaging the mt data established the boundaries and geometries of the host rocks including the distribution of lithology structures alteration and mineralization the four case studies in this paper show how this integrated geological and geophysical approach was used successfully to discover hidden mineral deposits

archaean hydrothermal zircon in the abitibi greenstone belt constraints on the timing of gold mineralisation abstract hydrothermal zircons have been found in archaean mesothermal au veins and altered wallrock selvages at val d or in the abitibi greenstone belt of canada the zircons are paragenetically associated with vein quartz tourmaline mica carbonate scheelite pyrite and gold zirconium mobility and the consequent occurrence of hydrothermal zircon may be associated with the intense tourmalinisation characteristic of archaean gold deposits in this district the shrimp ion microprobe has been used to analyse hydrothermal zircons from four separate mines spatially associated with the bourlamaque batholith and has yielded ages constraining formation of the au bearing vein systems to within 20 ma of emplacement of the pluton the ion microprobe data reveal multiple stages of hydrothermal zircon growth in the vein systems contemporaneous with the regional metamorphic peak and late kinematic activity along regional structures younger including proterozoic ages previously obtained for the veins using other minerals and isotopic schemes must reflect either alteration or renewed mineral growth during much later reactivation of fluids along the same structures up to 400 ma after initial formation of the veins

long runout mechanism and landsliding behaviour of large catastrophic landslide triggered by heavy rainfall in guanling guizhou china a large catastrophic landslide was triggered by a heavy rainfall on 28 june 2010 in guanling guizhou china the landslide buried two villages and killed 99 people along the runout path the lands

dda validation of the mobility of earthquake induced landslides abstract this paper studies the run out of earthquake induced landslides there are more than 20 mechanical models to explain long run out of rapid landslides including some earthquake induced landslides however notably few of them considered the effect of seismic loading on the run out of landslides in a previous study we have proposed a model which is called the multiplex acceleration model mam to interpret the long run out mechanism and a shaking table test has been performed to verify the mam because the previous mam is a conceptual model and only a single stone has been examined under sine waves by the shaking table test the mam needs to be extended and further verified in this paper the mam was extended by introducing the movement change that was induced by the so called trampoline effect of earthquake loading and the latest practical numerical simulation program discontinuous deformation analysis dda was used to verify the mobility of earthquake induced landslides after a conceptual landslide model was used to verify the effect of seismic loading on the mobility the donghekou landslide which was a typical long run out landslide that was induced by the 2008 wenchuan earthquake was analyzed the results show that the seismic loading could be one of the factors that could eventually help increase the run out of landslides

a dynamic model for rainfall induced landslides on natural slopes assessment of landslide hazard often requires a good knowledge of the landslide characteristics and runout mechanics in this paper a quasi three dimensional model using lagrangian finite element method lfem is formulated to reproduce the dynamic runout process caused by landslides a case study of rainfall induced landslide on a natural slope in 1993 in lantau island hong kong is presented voellmy rheology is adopted to characterize the multi dimensional runout behaviour for engineering applications the selection of appropriate rheology and the determination of relevant key parameters associated with the failure mechanisms and runout mechanics are highlighted details of the mathematical formulation particularly with respect to the stability of the numerical scheme and quality control of the mesh are provided the close correlation between the calculation results and the field observations shows that if an appropriate rheological relationship is selected for the simulation a reasonable description of the runout behaviour can be obtained using the present model implications of the potential hazard from natural terrain landslides to downslope development are also discussed used in conjunction with geographical information system gis database the model can also be applied to the preliminary hazard zoning of terrain and land use management in mountainous areas

trace element contents and in situ sulfur isotope analyses of pyrite in the baiyun gold deposit ne china implication for the genesis of intrusion related gold deposits abstract trace elements distribution in minerals and formation mechanism of visible gold are poorly understood in intrusion related gold systems here we choose the baiyun gold deposit which is hosted within the paleoproterozoic metamorphic rocks in the liaodong peninsula ne north china craton ncc as a case study to address these issues the ore deposit geology characteristics and paragenesis are described in details in situ geochemical and sulfur isotopic compositions of pyrite and bulk pb isotopic ratios of pyrite were presented to define the genesis of pyrite that is closely associated with gold mineralization three generations of pyrite were recognized based on petrographic studies metamorphic pyrite py0 hydrothermal pyrite py1 coexisting with milky quartz and hydrothermal pyrite py2 coexisting with smoky quartz in situ laser ablation inductively coupled plasma mass spectrometer la icp ms spot analysis suggests that both py0 and py1 contain low contents of invisible gold mean 0 19 ppm and 0 17 ppm respectively however py1 is low in most other trace element contents and contains au ag cu pb bi micro inclusions in contrast py2 contains both invisible gold mean 0 50 ppm and au ag cu pb bi micro inclusions furthermore la icp ms mapping reveals the distributions of ag cu pb bi and te closely mimic that of au indicating an episode of ore forming fluid rich in au ag cu pb bi and te in situ sulfur isotope analysis of pyrite shows that py0 has significantly positive 34s values 11 74 17 33 suggesting that sulfur was derived from sedimentary sources py1 and py2 have negative 34s values 8 53 6 19 10 44 6 86 respectively indicating that sulfur was derived from oxidized magmatic fluids the magmatic fluids are concluded to be released from the early cretaceous microdiorite magmas providing most of the sulfur and ore forming metals proofs include the close spatial association of the ore bodies and the dykes as well the uniform pb isotopic ratios of py1 and the early cretaceous microdiorite lines of geological mineralogical geochemical and isotopic evidence consistently suggest that the gold mineralization in the baiyun deposit is intrusion related and was resulted from the 126 ma magmatic hydrothermal activities in the region visible gold precipitating in pyrite and fractures was from metal rich magmatic fluids rather than being remobilized from the metamorphic pyrite

northwestern junggar basin xiemisitai mountains china a geochemical and geochronological approach abstract we report sims u pb zircon elemental and nd sr pb isotopic data for the volcanic rocks and their subvolcanic units from the xiemisitai mountains in the west junggar region xinjiang china aiming to determine their ages source regions and tectonic setting zircon u pb dating results of the volcanic rocks 422 5 1 9 ma 411 2 2 9 ma indicate that the volcanic strata occurred in the xiemisitai mountains at late silurian early devonian time rather than middle devonian as suggested previously they are probably the eastern extension of the early paleozoic cambrian silurian boshchekul chingiz volcanic arc of east kazakhstan in china the xiemisitai volcanic rocks include andesite rhyolite and their pyroclastic equivalents the subvolcanic units are felsite and granite porphyry andesite is moderately lree enriched with a marked negative nb anomaly and th yb enrichment rhyolite felsite and granite porphyry are enriched in lree and th and depleted nb the initial sr isotope values of the xiemisitai volcanic rocks and their subvolcanic units range from 0 702294 to 0 704456 e nd 420 ma from 0 19 to 1 88 with nd model ages ranging from 600 to 803 ma initial pb isotope ratios 206 pb 204 pb are 17 77 17 96 207 pb 204 pb are 15 49 15 54 and 208 pb 204 pb are 37 56 37 80 these features suggest that the xiemisitai volcanic rocks and their subvolcanic units derived from a mantle wedge significant mixed by subducted material emi in a subduction zone they also indicate significant involvement of neoproterozoic primitive crust in the formation of the xiemisitai magmatic arc these rocks are associated with a late silurian early devonian southward subduction of the oceanic lithosphere in the northern west junggar region this gives rise to an ew trending boshchekul chingiz volcanic arc and associated metallogenic belt in the northern west junggar region and adjacent kazakhstan

a manto type cu deposit in the central asian orogenic belt the hongguleleng example xinjiang china abstract manto type cu deposits with relatively high grade up to 8 wt cu occurred widely around the pacific rim belt and along the himalayan tibetan belt however so far manto type cu deposits have not been reported in the central asian orogenic belt caob hongguleleng also called armuqiang located in the west junggar xinjiang china is the first recognized manto type cu deposit it is hosted in the late silurian early devonian volcano sedimentary sequence and associated with pale volcanic apparatus the cu bodies are restricted to particular porous units e g andesitic volcanic breccias amygdale basalt and andesite and are mostly controlled by the steep dipping fault zones the host volcanic rocks have been overprinted by three alteration assemblages and associated copper mineralization an early barren propylitic chlorite calcite assemblage is widespread and is overprinted by epidote chlorite assemblage associated with ores they are cut by barren calcite veins the major copper sulfides are chalcopyrite bornite and chalcocite that show disseminated amygdale filling breccias vein veinlet massive and replacement textures only two fluid inclusion types were recognized in quartz calcite and epidote liquid rich and vapor rich inclusions they have homogenization temperatures in the range 140 280 c sulfur isotope compositions from ores have a positive 34s values range from 0 5 to 3 4 suggesting a magma source from the geology alteration mineralization and fluid inclusion characteristics and sulfur isotopic compositions we propose that the hongguleleng deposit is classified as a typical manto type copper deposit

listvenite and related rocks perspectives on terminology and mineralogy with reference to an occurrence at cregganbaun co mayo republic of ireland the rock listvenite is named and defined by reference to historical observations and recommendations are made so that listvenite s s can be distinguished from related carbonate rich alteration products of ultramafic rocks the mineralogy and tectonic setting of listvenite are reviewed taking into account the descriptions and classifications used in the literature the petrography of listvenite and related rocks at cregganbaun serves as a reference to illustrate the characteristics of true listvenite and closely related products of listvenitic alteration

arsenic associated with historical gold mining in the sierra nevada foothills case study and field trip guide for empire mine state historic park california the empire mine together with other mines in the grass valley mining district produced at least 21 3 million troy ounces 663 tonnes of gold au during the 1850s through the 1950s making it the most productive hardrock au mining district in california history clark 1970 the empire mine state historic park empire mine shp or emshp established in 1975 provides the public with an opportunity to see many well preserved features of the historic mining and mineral processing operations cdpr 2014a a legacy of au mining at empire mine and elsewhere is contamination of mine wastes and associated soils surface waters and groundwaters with arsenic as mercury hg lead pb and other metals at emshp as has been the principal contaminant of concern and the focus of extensive remediation efforts over the past several years by the state of california department of parks and recreation dpr and newmont usa ltd in addition the site is the main focus of a multidisciplinary research project on as bioavailability and bioaccessibility led by the california department of toxic substances control dtsc and funded by the u s environmental protection agency s usepa s brownfields program this chapter was prepared as a guide for a field trip to emshp held on june 14 2014 in conjunction with a short course on environmental geochemistry mineralogy and microbiology of arsenic held in nevada city california on june 15 16 2014 this guide contains background information on geological setting mining history and environmental history at emshp and other historical au mining districts in the sierra nevada followed by descriptions of the field trip stops regional geology empire mine shp is located in the grass valley mining district on the western sloping foothills of the sierra nevada fig 1 the sierra nevada foothills snfh orogenic gold province stretches 150 miles 240 km from the town

volcanic red bed copper mineralisation related to submarine basalt alteration mont alexandre quebec appalachians canada two types of native copper occur in upper silurian basaltic rocks in the mont alexandre area quebec appalachians 1 type 1 forms micrometric inclusions in plagioclase and is possibly magmatic in origin whereas 2 type 2 occurs as coarse grained patches rimmed by cuprite in altered porphyritic basalt type 1 has higher contents of sulphur 2 000 20 263 ppm and arsenic 146 6 017 ppm and a broader range of silver abundances 65 2 186 ppm ag than type 2 149 1 288 ppm s 90 146 as 65 928 ppm ag no mineral inclusions of sulphide or arsenide in native copper were observed at the electron microprobe scale primary igneous fabrics are preserved but the basaltic flows are pervasively oxidised and plagioclase is albitised chlorite replaces plagioclase and forms interstitial aggregates in the groundmass and has fe fe mg ratios ranging from 0 29 to 0 36 with calculated temperatures between 155 c and 182 c copper sulphides in vacuoles and veinlets are associated with malachite fibro radiating albite and yarrowite cu9s8 with up to 0 3 wt ag bulk rock concentrations of thallium and lithium range from 70 to 310 ppb and 10 to 22 ppm respectively and thallium is positively correlated with fe2o3 such concentrations of thallium and lithium are typical of spilitisation during heated seawater basalt inter action spilitisation is consistent with the regional geolog ical setting of deepwater facies sedimentation but is different from current models for volcanic red bed copper which indicate subaerial oxidation of volcanic flows the volcanic red bed copper model should be re examined to account for native copper mineralisation in basalts altered by warm seawater

concentration of gold during retrograde metamorphism of archean banded iron formations slave province canada gold bearing iron formations are widely distributed within extensive metasedimentary terranes of the archean slave province situated in the northwestern canadian precambrian shield mineralized iron formations occur within thick turbidite sequences overprinted by a protracted history of deformation metamorphism and plutonism economically significant gold prospects are specifically sited at structural culminations characterized by polyphase folding based on garnet biotite geothermometry on the stable prograde metamorphic assemblage of enveloping metapelites peak metamorphic conditions are approximated to be 570 c and 4 kbar 1 kbar 100 mpa diagnostic prograde mineralogy reveals that two facies of silicate iron formation are represented at the five gold occurrences investigated 1 amphibolitic iron formation aif characterized by quartz grunerite hornblende pyrrhotite garnet f graphite ilmenite and 2 pelitic iron formation pif consisting of quartz biotite garnet ilmenite f grunerite hornblende textures reveal that grunerite crystallization preceded hornblende and garnet within aif banded pyrrhotite is in textural equilibrium with prograde metamorphic minerals retrograde hornblende garnet zoisite apatite carbonate ferroactinolite and gold bearing sulphide minerals replace the prograde mineral assemblages on the margins of quartz veins that intensify at aif fold hinges it is hypothesized that the iron formation hosted gold deposits of the slave province are a result of multistage processes gold concentrated at high background levels within pyrrhotite bearing aif was remobilized during fluid migration into brittle aif fold hinges in subsequent metamorphic and deformational events metamorphic fluid ponded in fractured aif hinge domains caused retrogressive replacement quartz veining and gold bearing sulphide precipitation during waning temperature although the mineralized hinge zones commonly display evidence of late chloritization this alteration did not further affect gold distribution the gold precipitated with destabilization of thio complexes due to sulphidation prior to lowtemperature hydrothermal activity

strains and structures associated with a terrane bounding stretching fault the melones fault zone central sierra nevada california abstract an examination of the structures total strains and rock types across the melones fault zone indicates that in the central sierra nevada this fault separates and locally imbricates two distinct terranes east of the fault a widespread early jurassic cleavage displays west northwest to northwest strikes and is associated with moderate to high strain intensities these structures form in jura triassic metasedimentary rocks in part derived from a continental source a weak northwest striking cleavage and low strain intensities occur west of the fault in lower jurassic volcanic rocks and upper jurassic slates and sandstones the fault zone itself consists of steep east dipping ductile brittle shear zones or stretching faults along which the early jurassic structures are transposed parallel to the jura cretaceous and fault related structures large flattening type strains are common in the fault zone and may be the result of heterogeneous strains developed when the shear zones bend around resistant blocks or by volume losses total strains in the eastern hanging wall reflect the superposition of fault related on older strains therefore stretching lineations in this hanging wall do not reflect directions of fault motion stretching lineations in the footwall and fault zone kinematic indicators in the fault zone and a small eastward jump in metamorphic grade suggest an east over west or reverse sense of movement no evidence for significant strike slip or oblique slip motion was found removal of footwall strains indicates that the jura cretaceous shortening across the fault was responsible for both the transposition of older structures east of the fault and the rotation of the fault to its present steep dips thus the melones fault is a large ductile brittle shear zone along which the eastern hanging wall merced river terrane moved to the southwest over the western footwall eastern foothills terrane

a model for the runout analysis of rapid flow slides debris flows and avalanches runout analyses are used for risk assessment and design of remedial measures against rapid landslides such as debris flows debris avalanches rockslide avalanches large scale liquefaction failure

synmetamorphic lode gold deposits in high grade archean settings lode gold deposits that formed under conditions of the middle to upper amphibolite and granulite facies have been identified in the yilgarn block of western australia these deposits which form a continuum with lower metamorphic grade mesothermal gold depos its show that at least some of the fluids responsible for mesothermal gold deposits originated in or below the middle crust studies of 18 o suggest that fluid compositions were controlled by the wall rocks at least for some elements these more proximal gold deposits provide more information about deep fluid sources than do investigations of higher level mineralization deposited from fluids strongly modified by wall rock interaction during the early part of their ascent

high temperature carbonate hosted ag pb zn cu deposits of northern mexico the high temperature carbonate hosted ag pb zn cu deposits of northern mexico occur in thick carbonate dominant jurassic cretaceous basinal sedimentary sequences floored by paleozoic or older crust the districts lie within or on the margins of a major fold thrust zone structures parallel to the trends of this belt control mineralization in many districts altered and or mineralized volcanic and intrusive rocks of tertiary age are found in all but three of the districts mineralization apparently occurred during a restricted period 47 to 26 m y ago the deposits are characterized by irregular ore lenses that commonly reveal strong structural controls and are stratigraphically discordant orebodies are of three principal morphological types mantos chimneys and pods and are composed of massive sulfides and or calc silicate skarn sulfide mantos and chimneys are enclosed within carbonate rocks and are generally remote from intrusive bodies sulfide mantos commonly grade downward into sulfide chimneys which may in turn grade downward into skarn chimneys cored by dikes podiform skarn and sulfide orebodies principally occur along stock dike or sill contacts but they may also be developed at some distance from an intrusive contact the associated intrusions are not widely mineralized despite the variations between ore types major similarities are seen in structural controls host rock characteristics and sulfide mineralogy structural controls include intrusive contacts faults fold axes fractures fissures and cavern zones intrusive contacts and intrusion related faults are most important in the skarns whereas regional fault fold and fracture systems are dominant controls on mantos and chimneys mineralization commonly occurs below relatively impermeable shaly units sills or volcanic rocks but some extensive orebodies show remarkable restriction to specific horizons within apparently homogeneous carbonate successions studies of mineralized and unmineralized strata have found no consistent links between ore deposition and carbonate composition facies organic content or insoluble components however zones of secondarily enhanced porosity and permeability induced by recrystallization heating deformation or hydrothermal dolomitization are important mineralization controls geochemical data for the deposits are sparse but indicate strongly contrasting conditions among some of the major districts fluid inclusion data indicate temperatures in the range 200 degrees to 500 degrees c and salinities ranging from i to 60 equiv wt percent nacl the hotter more saline solutions are typically from skarn zones evidence for boiling has not been reported the skarn ores of naica concepcion del oro and velardefia show tight clustering of sulfide sulfur isotope values near 0 whereas the skarn and massive sulfide ores of santa eulalia show a wide range of values in most cases there is isotopic disequilibrium between galena and sphalerite pyrrhotite or pyrite calcite veinlet stockworks above mineralization and limestone wall rocks adjacent to mineralization show shifts of carbon and oxygen isotopes to lighter values the tightly clustered sulfur isotopes and high temperature high salinity fluid inclusions have been interpreted as indicating a strong magmatic component in the mineralizing fluids at naica concepcion del oro and velardena but santa eulalia and other districts show evidence suggesting extensive mixing between magmatic and meteoric fluids it appears that the spectrum of mineralization styles shown by these deposits represent differing responses to variations in intrusive associations depth of emplacement host rock characteristics and geochemical evolution of the individual systems

age of mineralization by basinal fluids at the el soldado manto type copper deposit chile 40ar 39ar geochronology of k feldspar abstract manto type copper deposits of the southern central andes are strata bound epigenetic mineral concentrations hosted by bimodal volcanic and volcaniclastic rock suites they are economically important but since they are not obviously related to intrusions their genesis has been controversial to some extent because it has proven difficult to date the ore forming event and distinguish it from the age of low grade regional metamorphism el soldado the largest manto type copper deposit in central chile is hosted by marine volcanic and subvolcanic intrusive rocks of the lower cretaceous extensional arc to discriminate between regional metamorphism and mineralization we dated 11 samples of k feldspar by the stepwise heating 40 ar 39 ar method hydrothermally precipitated k feldspar associated with copper sulfides precipitated at temperatures of 300 c and range in age from 100 5 1 5 to 106 1 1 1 ma mean 103 1 6 ma n 8 syn mineralization k feldspar gave an age of 102 5 2 0 which is interpreted to be the age of mineralization k feldspar unrelated to ore yields older ages between 109 4 1 1 and 112 2 ma mean 110 3 1 4 ma n 3 is variably reset by the younger ca 103 ma mineralization episode the above ages are interpreted to represent the age of alkali redistribution and crystallization due to burial metamorphism of the host sequence fission track dating of apatite in the host rocks yields an age of ca 90 ma indicating fast cooling of the system to less than ca 100 c after mineralization time temperature modeling of fission track length data are compatible with initial fast exhumation followed by slow exhumation and cooling to surface temperatures high levels of atmospheric ar were detected in all k feldspar samples and are tentatively attributed to connate meteoric fluids incorporated into the basinal metamorphic mineralizing fluids

on characteristics and dynamic analysis of the niumian valley rock avalanche triggered by the 2008 wenchuan earthquake sichuan china on may 12 2008 a large catastrophic rock avalanche was triggered by the wenchuan earthquake on niumian valley in yingxiu town wenchuan county china the displaced landslide materials traveled about 2 640 m with a descent of about 850 m and buried several houses and caused nearly 20 casualties based on detailed field investigation some basic characteristics of this landslide are introduced field investigation showed that the displaced landslide materials experienced three times of run up and twice of superelevation along the run out path and downslope enlargement due to the entrainment of run out path materials a numerical model dan3d is used to simulate the landsliding process by means of trial and error it can be seen that the voellmy model and values of friction coefficient f 0 19 dimensionless and turbulent coefficient xi 2 000 m s2 can provide the best performance in the prediction of sliding and depositing areas the simulated results show that the duration of the rock avalanche is about 120 s with an average velocity of 22 m s

granites in the sawuer region of the west junggar xinjiang province china geochronological and geochemical characteristics and their geodynamic significance abstract the sawuer region is located in the west junggar jimunai county of altay district and hefeng county of tacheng district xinjiang autonomous region in northwest china in the study area granitic intrusions are widespread and can be subdivided into i type granites tasite pluton sentasi pluton wokensala pluton and kaerjia pluton and a type a 2 granites kuoyitasi pluton and qiaqihai pluton the i type granites consist of granite adamelite granodiorite and the a type granites are mainly represented by alkali granite shrimp u pb dating results indicate that the granites in sawuer region were formed between 337 ma and 290 7 ma late carboniferous and early permian with the i type granites being formed between 337 ma and 302 6 ma and the a type between 297 9 and 290 7 ma from the older to the youngest granites their composition changes from calc alkalic to high k calc alkalic to alkali series and from i type to a type based on the characteristics of whole rock trace element and rare earth elements geochemistry this compositional range is the result of a change in the geodynamic regime from compressional to tensional during the late paleozoic strontium nd pb o isotope systematics suggest that both the i type and a type granites in sawuer were sourced from the mantle dm but with some crustal contamination for the kuoyitasi pluton the i type granites were formed by equilibrium partial melting while the a type granites were formed mainly by fractional crystallization based on the rb y nb and nb y ce discrimination criteria by eby eby g n 1992 chemical subdivision of the a type granitoids petrogenetic and tectonic implications geology 20 641 644 and pearce pearce j a 1996 sources and settings of granitic rocks episodes 19 120 125 and comparisons with granites in other regions of northern xinjiang the i type granites were emplaced during a transition from compressional to extensional settings in a post collision regime whereas the a type granites were emplaced in an extensional setting we concluded that the sawuer as well as the whole junggar region in northern xinjiang were involved in tectonism that gradually changed from compressional to extensional between the late carboniferous and early permian this late paleozoic granitic magmatism contributed to vertical crustal growth in the region

a fluid inclusion study of au bearing quartz vein systems in the central and north deborah deposits of the bendigo gold field central victoria australia the central and north deborah gold deposits with a production of about 7 tons au are located in one of 15 domes in the bendigo gold field central victoria australia an important mesothermal lode gold province the gold bearing quartz vein systems are hosted predominantly by reverse faults in lower ordovician turbidites which underwent lower greenschist facies metamorphism in the central and north deborah mines there are six stages of quartz veins that developed in the following sequence 1 laminated veins with a metal association of au as sb pb zn ni 2 spurs au 3 massive barren veins main dilation stage 4 brecciated veins with au as 5 quartz ankerite veinlets and 6 late pure quartz or calcite veinlets of the three mineralized vein stages 1 2 and 4 only the first one predated or was coeval with the main deformation event whereas stages 2 and 4 postdated the main deformation the vein structures indicate that vein development was controlled by repeated fluctuations of fluid pressure inducing hydraulic fracturing fluid inclusions in vein quartz contain c o h fluids of variable compositions three main types of fluid inclusions are recognized at room temperature type i two phase primary ch4 v h2o l fluid inclusions type ii two or three phase primary pseudosecondary co2 v or l ch4 v or l h2o l fluid inclusions including iia ch4 co2 h2o and iib co2 h2o fluid inclusions and type iii h2o v h2o l fluid inclusions type iii fluid inclusions are further divided into three groups iiia primary pseudosecondary vapor rich iiib primary pseudosecondary liquid rich and iiic secondary liquid rich data from fluid inclusion distribution microthermometry and raman spectroscopy indicate that fluids associated with au mineralized quartz veins stages 1 2 and 4 have moderate salinity ranging from 0 to 12 wt percent nacl equiv modeled salinities around 7 8 wt nacl equiv these veins formatted at temperatures from 325 to 375 c and pressures of 200 to 300 mpa with emplacement depths of about 8 to 12 km fluids associated with barren quartz veins stages 3 5 and 6 have a low salinity of about 0 to 3 wt percent nacl equiv modeled salinities about 2 3 wt nacl equiv and lower temperatures there is evidence of fluid immiscibility in all vein stages and mixing between fluids of the same souce but differing fo2 may also have influenced gold deposition cox et al 1995 hydrothermal ore forming fluids responsible for gold mineralization are in the ch2 co2 h2o nacl system whereas those of massive barren veins stage 3 and veinlets stages 5 and 6 are in the co2 h2o nacl and h2o nacl systems respectively the carbonic phases of type i and ii fluid inclusions range from pure ch4 through mixed ch4 and co2 to pure co2 gold ore forming fluids were weakly acidic with f o2 estimated to have been 10 25 to 10 37 bars and generally above the co2 ch4 and below the so2 h2s buffer boundaries throughout gold mineralization the relatively reduced mineralizing fluids are similar to those of other turbidite hosted lode gold deposits and counterparts in volcanic plutonic terranes

geology mineralization and sulfur isotopes geochemistry of the mari cu ag manto type deposit northern zanjan iran abstract the eocene volcano sedimentary sequence northern zanjan consist of 1 5 km of shallow marine sediments these include sandstone lapilli tuff andesite basalt and felsic volcanic rocks the mari deposit is strata bound that hosted by the eocene andesite rocks the major copper sulfides are bornite chalcocite and chalcopyrite associated mainly with pyrite that show open space filling disseminated vein veinlet and replacement textures the abundances of cu and ag in the ore bearing andesite are up to 40 000 and 70 ppm respectively wall rock alterations include carbonatization chloritization epidotization and sericitization sulfur isotope compositions have a negative range from 34 s 2 7 to 3 4 suggesting the presence of a reducing environment resulting from activation of sulfate reducing bacteria mineralization formed two stages stage one include volcanic activity and eruption of andesitic lava in this stage syngenetic disseminated pyrites formed in the second stage increasing of the thickness of sediments basin subsidence and burial diagenesis accompanied with the entry of metal rich fluids into the reduced host rock caused the replacement of the first stage pyrites by copper sulfides the geology ore mineralogy alteration characteristics and sulfur isotopic compositions suggest the mari deposit may be classified as a manto type deposit

effects of mother lode type gold mineralization on 187os 188os and platinum group element concentrations in peridotite alleghany district california osmium isotope compositions and concentrations of re platinum group elements pge and au were determined for host peridotites serpentinites and harzburgites and hydrothermally altered ultramafic wall rocks associated with mother lode type hydrothermal gold quartz vein mineralization in the alleghany district california the host peridotites have os isotope compositions and re pge and au abundances typical of the upper mantle at their presumed formation age during the late proterozoic or early paleozoic the hydrothermally altered rocks have highly variable initial os isotope compositions with os values deviation of 187os 188os from the chondritic average calculated for the approx 120 ma time of mineralization ranging from 1 4 to 8 3 the lowest os isotope compositions are consistent with re depletion of a chondritic source e g the upper mantle at ca 1 6 ga most of the altered samples are enriched in au and have depleted and fractionated abundances of re and pge relative to their precursor peridotites geochemical characteristics of the altered samples suggest that re and some pge were variably removed from the ultramafic rocks during the mineralization event in addition to re the pt and pd abundances of the most intensely altered rocks appear to have been most affected by mineralization the 187os depleted isotopic compositions of some altered rocks are interpreted to be a result of preferential 187os loss via destruction of re rich phases during the event for these rocks os evidently is not a useful tracer of the mineralizing fluids the results do however provide evidence for differential mobility of these elements and mobility of 187os relative to the initial bulk os isotope composition during hydrothermal metasomatic alteration of ultramafic rocks

deformation and regional carbonate metasomatism of turbidite hosted cretaceous alkaline lamprophyres northwestern papua new guinea abstract a suite of variably metasomatised camptonite dykes and rare stocks named the fu intrusives has been recognised within thrust plates of mesozoic slates in a 3000 km2 portion of the new guinea thrust belt the intrusions were emplaced prior to oligo miocene fold deformation and low grade regional metamorphism of their host and consequently have foliated margins and are cross cut by metamorphic quartz veins samples from the less altered stocks display primary cumulophyric aggregates of kaersutite titansalite titanbiotite set in a matrix of albite salite apatite olivine quartz calcite ocelli are occasionally present ree patterns la cn lu cn 10 la 100 chondrite and initial sr ratios 0 7042 are typical of alkaline lamprophyres kaersutite and titanbiotite separates from such samples have yielded concordant k ar ages of 75 ma campanian which we accept as the age of intrusion however the dykes have suffered heavy texture destructive carbonate sericite alteration though relict cumulophyric texture and globular structures are sometimes observed composition volume calculations suggest that metasomatism was accompanied by loss of na ti and p and systematic addition of ca fe and co2 as well as progressive lree depletion and fe reduction alteration carbonates exhibit a narrow range of 18o values 13 8 to 14 9 indicating uniform conditions of metasomatism throughout the terrain the calculated fluid 18o at a model temperature of 300 50 c is 8 2 which corresponds with that deduced from the 18o value 12 3 of the cleanest sericite separate the four analysed sericite separates have a mean d of 64 12 implying an hydrogen isotopic composition for the alteration fluid of 58 30 at 300 50 c the calculated fluid composition therefore overlaps the normal range of metamorphic and magmatic waters however c and sr isotopic ratios of the alteration carbonates 13c 7 3 to 0 4 87 sr 86 sr 0 7076 0 7126 strongly support a crustal source for the metasomatic fluids this is corroborated by field evidence that country rock slates adjacent to the dykes are unaffected by carbonate metasomatism and hence were in equilibrium with the alteration fluid we therefore conclude that regional carbonate metasomatism of the fu intrusive suite occurred as a result of metamorphic dewatering of their host rocks during slaty cleavage development

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

archean gold relation to granulite formation and redox zoning in the crust the archean was the principal period for gold mineralization these rocks compose 12 of the exposed crust but have produced more than half of the world9s gold most major lode deposits formed at 2 7 0 2 ga this corresponds to the principal time of crustal thickening and stabilization an essential part of which was formation of granulite the anhydrous refractory base for the crust upward streaming of mantle co 2 along shear zones in the lower crust is one means for dehydrating amphibolite to form granulite and is accompanied by removal of large ion lithophile lil elements to higher crustal levels archean lode gold deposits were formed along major shear zones at intermediate crustal depths they are enclosed by zones of co 2 metasomatism many of them kilometres in extent 13 c data indicate that the co 2 is juvenile some major archean deposits have been shown to have formed from relatively oxidized hydrothermal fluids co 2 streaming with lil element depletion could only have occurred under relatively oxidized conditions that permitted a free co 2 vapor to exist in the lower crust such conditions would also have favored dissolution of gold and associated sulfide and their transfer to the mid crust in a co 2 h 2 o fluid the h 2 o coming from dehydration of amphibolite

extreme deformation characteristics and countermeasures for a tunnel in difficult grounds in southern shaanxi china the qingling bashan qb mountain region in southern shaanxi mainly consists of strongly compressive zones from east to west with tight folds and compressive fractures there is a wide distribution of soft rocks of various types such as phyllite and slate accompanied by complex geological structures ironically tunnel construction in these difficult grounds with complicated geological conditions embraces a high risk of extreme deformation due to various unpredictable reasons which can frequently cause collapse and result in budget overruns during the construction period therefore it is crucial to conduct effective countermeasures to eliminate or avoid such adverse impacts this paper provides a case study on the yingfeng tunnel a tunnel constructed in soft rock consisting of a slate ground based on a geological survey indoor experiments and in situ monitoring a successive rock mass deformation resulted in the tunnel lining seriously intruding into construction clearance and some other sections even collapsing during the construction the maximum displacement amount was 62 5 cm while the maximum deformation speed reached as high as 34 18 mm day additionally to evaluate the construction impacts of tunnelling induced geo hazards an investigation on extreme deformation was conducted considering the time dependent features of the rock mass deformation the constraint convergence method was used to put forward applicable countermeasures in this paper finally from the feedbacks of monitoring results extreme deformation of the yingfeng tunnel was effectively controlled

gold mineralization in the okanagan valley southern british columbia fluid inclusion and stable isotope studies two styles of precious metal vein mineralization epithermal and mesothermal occur in the okanagan valley of southern british columbia the epithermal deposit dusty mac is composed of quartz stockwork mineralization in eocene volcanic and volcaniclastic rocks the mesothermal deposits fairview and oro fino consist of thick 1 10 m quartz veins in paleozoic and mesozoic metamorphic rocks fluid inclusion and stable isotope studies indicate that two distinct hydrothermal fluids were responsible for the mineralization events at dusty mac the epithermal fluid had a relatively low temperature 230 degrees 250 degrees c extremely low salinity 18 o 7 to 9ppm and delta d 133ppm values at fairview and oro fino the mesothermal fluids had higher temperatures 280 degrees 330 degrees c significant co 2 contents and higher salinities 3 6 equiv wt nacl stable isotope data show that the mesothermal fluids had low delta d 121 to 148ppm and delta 13 c 8 5ppm values but high delta 18 o 4 to 6ppm values the data indicate that the fluids involved in both styles of mineralization are 18 o shifted meteoric water with shallow circulation responsible for the epithermal deposits and deep circulation involved in the formation of the mesothermal deposits although both styles of mineralization occur in the same tectonic regime it appears that they are not temporally or genetically related to each other

dynamic process analysis for the initiation and movement of the donghekou landslide debris flow triggered by the wenchuan earthquake the donghekou landslide debris flow was a remarkable geological disaster triggered by the wenchuan earthquake in 2008 the dynamic process of a rapid landslide debris flow is very complicated and can be divided into two aspects the slope dynamic response of the earthquake and the mass movement and accumulation process a numerical method combined with a finite difference method fdm and discrete element method dem for simulation of landslide debris flow under seismic loading is presented the fdm and dem are coupled through the critical sliding surface initiation time and velocity the dynamic response of the slope is simulated by the finite difference method and critical sliding surface is determined using the earthquake response spectrum method the landslide initiation time and the velocity are determined by time history analysis the mass movement and accumulation process is simulated using the discrete element method simulation results demonstrate that the maximum amplification coefficient of dynamic acceleration for the donghekou slope is approximately 3 909 the initiation time of landslide is approximately 6 0 s and the average initial velocity of the sliding mass is approximately 0 85 m s the failure of the slope is the result of elevation orientated amplification effect and the sliding mass triggered with a small initial velocity the numerical simulated result of the maximum sliding velocity is approximately 66 35 m s and the mass is disintegrated rapidly because of collision and free fall the landslide velocity decreases when the flowing mass reaches a lower slope angle and gradually comes to a stop and the total travel distance is approximately 2400 m c 2013 elsevier ltd all rights reserved

an isotopic c o sr study of vein gold deposits in the meguma terrane nova scotia implication for source reservoirs vein quartz carbonate and tourmaline from 19 meguma gold deposits in the meguma terrane of nova scotia have been analyzed for stable delta 18 o delta 13 c and radiogenic 87 sr 86 sr isotopes in order to assess the nature and origin of the vein forming fluids as with other mesothermal gold provinces the meguma gold deposits are well suited to such a study because carbonate is the next most abundant phase after quartz in these mesothermal lode gold deposits all vein types have been sampled for quartz and carbonate and in addition all compositional and textural varieties of carbonate have been sampled vein quartz is of uniform isotopic composition with most 18 o values between 10 2 to 17 6 per mil avg ca 14 per mil except for one deposit west gore sb au where values go to 19 4 per mil there is no systematic variation for quartz within a deposit or position within the meguma group stratigraphy vein carbonate 18 o values range from 11 8 to 27 5 per mil with most in the 13 to 16 per mil range the relatively 18 o enriched carbonates reflect exchange with low temperature fluids based on analyses of quartz carbonate pairs that indicate disequilibrium fractionation delta sub quartz carbonate or 0 this is best illustrated by the strong negative correlation between delta 18 o carbonate and delta sub quartz carbonate the 18 o water is estimated at 10 or 3 per mil for a temperature of vein formation of 350 degrees to 400 degrees c and using the appropriate mineral water fractionation equations whereas delta 18 o water values partly overlap the field for magmatic fluids the values are wholly consistent with a metamorphic fluid and it is considered unlikely that a primary magmatic fluid signature has been substantially modified due to wall rock influences given that mesothermal gold systems are sites of high fluid rock ratios vein carbonate has delta 13 c values of 13 1 to 25 9 per mil but a slight negative correlation between delta 13 c carbonate and delta sub quartz carbonate suggests that the primary values lie in the range 20 to 25 per mil thus the delta 13 c values indicate a reduced biogenic source for the carbon oxidation of the reduced carbon as indicated by co 2 in fluid inclusions may have occurred via hydrolysis of graphite or dissolution of carbonate minerals both of which occur in the wall rock lithologies of the meguma group the latter of which has the appropriate isotopic composition the initial 87 sr 86 sr of the vein fluid estimated from the analyses of 52 vein carbonates 17 deposits and four tourmalines three deposits ranges from 0 70118 to 0 72284 and within deposits considerable variation is observed there is insufficient data to quantify the extent of the low temperature overprint which has modified the c and o isotope data although it is likely that some influence is present nevertheless the data cannot be reconciled by a source confined exclusively to the meguma group which suggests therefore involvement of another reservoir s the isotopic heterogeneity can be explained by variable amounts of contamination of a primary fluid with radiogenic sr derived from meguma group lithologies by interaction along the fluid path or at the site of vein formation concomitant with wall rock alteration as discussed above a dominantly magmatic source is not considered feasible this fluid source is suggested to be within the structural basement to the meguma group and the liscomb gneisses are the favored source based on the combined results of the sr isotope data presented herein and previously published pb isotope data collectively the data indicate that a primary fluid of metamorphic origin has had its isotopic signature variably modified due to interaction with different reservoirs the most affected isotopic systems are c and s based on earlier work on delta 34 s values which are abundant as graphite carbonate and sulfides in the meguma wall rock respectively the range in 87 sr 86 sr values of the fluid also reflects contamination but this was quite variable the uniform delta 18 o water value for the fluid indicates that this was the least affected isotopic system except for the later exchange of carbonate at low temperatures

the role of organic matter in the genesis of the el soldado volcanic hosted manto type cu deposit chile solid bitumen residual petroleum occurs intimately associated with sulfides in several manto type cu deposits of central chile el soldado 32 degrees 38 s 71 degrees 04 w is one of the largest manto type deposits 130 million metric tons1 5 cu and is hosted by rhyolites and andesites of the lower cretaceous lo prado formation as a result of basinal burial in the early cretaceous back arc basin petroleum was generated from organic rich shales in the underlying lower lo prado formation and migrated into primary and structural porosity in the upper lo prado formation migration was controlled by extensional basinal faults low temperature 90 degrees c biodegradation of petroleum developed an early stage i assemblage of mostly framboidal pyrite or sphalerite or chalcopyrite geopetal structures related to pressure degassing of semi solid petroleum suggest that migration occurred while the strata were horizontal at ca 130 ma continued basinal burial led to thermal degassing increased maturation and solidification of the petroleum low grade regional pumpellyite prehnite metamorphism of the sequence was followed at ca 110 to 103 ma by the influx of high temperature ca 300 degrees c cu rich fluids concurrently with emplacement of the cretaceous batholith into the basin basinal fluids were focused into a now tilted sequence by a brittle shear north south to north northwest fault system copper sulfides stage ii assemblage replaced preexisting pyrite and bitumen forming zoned orebodies with a central chalcocite hematite zone followed outward by bornite chalcocite chalcopyrite bornite and pyrite chalcopyrite zones the mineralizing fluids altered the bitumen thermally and chemically as follows 1 reflectance r o increased up to ca 5 percent in the core of the orebodies against a background of ca 3 percent 2 anisotropy nongranular microscale and domain developed and the bitumen was locally graphitized 3 chlorine or cu or fe was incorporated into the bitumen affecting its reflectance the source of cu was most likely the overlying oxidized volcanic pile the cu was transported as chloride cucl complexes precipitating where the cucl rich solutions reacted with bitumen adsorption reduction and pyrite from the stage i assemblage the study demonstrates that in the lower cretaceous basin of chile degraded petroleum reservoirs can be important controls for metallic mineralization derived from hydrothermal solutions of different sources particularly if biodegradation generated pyrite

archean lode gold deposits fluid flow and chemical evolution in vertically extensive hydrothermal systems abstract the range of conditions of formation of lode gold deposits from the sub greenschist to the lower granulite facies in archean greenstone belts and the generally steeply plunging vertically continuous pipe like or tabular geometries of individual deposits indicate long distance hydrothermal fluid advection along well defined channelways in the upper and middle crust from presently available gold solubility data destabilisation of gold bisulphide complexes through h 2 s loss from the fluid to the wallrock was the dominant gold precipitation mechanism within these hydrothermal systems as a whole this inference is supported by the s au ratios of ores sulphur and au precipitation in the hydrothermal system is estimated to be relatively inefficient with only 10 50 of s or au contained in the fluid precipitated over any kilometre length of fluid channelway the relative inefficiency of gold precipitation allowed mineralisation over a significant depth range in a crustal profile

failure forecast for large rock slides by surface displacement measurements forecasting the failure of large rock slides is difficult because of nonlinear time dependency and seasonal effects which affect the displacements starting from the accelerating creep theory prop

cu mn and ag mineralization in the quebrada marquesa quadrangle chile the talcuna and arqueros districts the quebrada marquesa quadrangle in chile exhibits a series of mineralizations comprising manto type manganese and copper deposits of lower cretaceous age and copper and silver veins of tertiary age the deposits are hosted by volcanic and volcaniclastic units of the arqueros hauterivian barremian and quebrada marquesa barremian albian formations three episodes of manganese mineralization mn1 3 are recognized within the study area hydrothermal activity leading to episodes 1 and 3 was of minor importance while the second one mn2 gave rise to major manto type deposits of both manganese and copper in the talcuna mining district extensional faulting during tertiary time resulted in block faulting and the unroofing of the oldest andesitic volcanics and marine sediments arqueros formation this episode was accompanied by magmatic and hydrothermal activity leading to vein formation in the arqueros ag and talcuna cu districts the latter veins cross cut the previous manto type copper deposits ore mineralogy is similar in both styles of mineralization manto and vein type and consists mainly of chalcopyrite and bornite with variable amounts of galena tetrahedrite vein related chalcocite sphalerite pyrite hematite digenite and covellite alteration processes at talcuna can be divided into two categories those related to the lower cretaceous manto type episode lk alteration chlorite epidote calcite albite prehnite zeolite and those associated with the locally mineralized normal faults of tertiary age tt alteration chlorite calcite sericite the arqueros silver veins display an ore mineralogy consisting of arquerite argentite native silver polybasite cerargyrite and pyrargyrite proustite associated alteration includes strong chloritization of the country rock the manto type deposits formed from fluids of salinity between 11 and 19 wt nacl equivalent and temperatures between 120 and 205 c mineralizing fluids during the vein type stage circulated at lower temperatures between 70 and 170 c with salinity values in a wide range from 3 to 27 wt nacl equivalent this distribution of salinities is interpreted as the result of the complex interplay of two different processes boiling and fluid mixing the former is considered to control the major mineralogical textural and fluid inclusion features of the vein type deposits we suggest that the lower cretaceous mineralization manto type stage developed in response to widespread hydrothermal activity geothermal field type involving basinal brines

shoshonitic lamprophyre dykes and their relation to mesothermal ausb veins at hillgrove new south wales australia abstract the hillgrove mineral field in the southern part of the new england orogen of northeastern new south wales australia contains numerous mesothermal au sb vein systems calc alkaline shoshonitic lamprophyre cal dykes are also associated with mineralisation with dilational lode structures acting as conduits for dyke intrusion which has occurred before and after major quartz stibnite veining dykes include minette and vogesite compositions and were emplaced in the late permian 247 255 ma at the same time as regionally extensive i type magmatism in the new england orogen least altered dykes are enriched in mg k ba rb sr zr th cr and ni relative to i type intrusives although chemical affinities are evident between lamprophyres and the more mafic members of the high k moonbi plutonic suite hillgrove lamprophyres are commonly enriched in sb as hg au w and bi with respect to average cal compositions evidence indicates this is most likely due to contamination of magma during intrusion through mineralised structures rather than a primary magmatic feature partially resorbed xenocrystic stibnite occurs in dykes which have intruded lode structures probably facilitated by the low melting point of stibnite 550 c and its incorporation into the magma carbon and oxygen isotopic data from carbonates in least altered post lode lamprophyres are indistinguishable from carbonate in altered dykes and veins implying that hydrothermal interaction continued after dyke intrusion although it is unlikely that lamprophyre dykes have been a direct source for mineralisation at hillgrove the close temporal and spatial relation of dykes mesothermal au sb veins and i type intrusions are interpreted to be manifestations of the post collisional setting and influx of mantle derived heat and partial melts into the new england orogen during the late permian