stalling of near inertial waves in a cyclone 1 observations at the edge of the loop current after hurricane katrina show inertial energy amplified at a depth of approximately 600 700 m ray analysis using the eddy field obtained from a numerical simulation with data assimilation suggests that the amplification is due to inertial motions stalled in a deep cyclone

near inertial internal wave interactions with mesoscale fronts observations and models moored observations of near inertial currents and buoyancy fluctuations from the frontal air sea interaction experiment fasinex may be understood as nearinertial internal waves reflecting off sheared background currents the fasinex moored array measured upper ocean currents temperature and conductivity between january and june 1986 in a region of the sargasso sea heavily populated by strong upper ocean fronts the background jets associated with these features have typical cross front scales of 20km maximum currents of 0 5 m s 1 and relative vorticities of 0 3 in the vicinity of fronts observed near inertial currents have short horizontal scales show no clear horizontal phase structure and trace out elongated current ellipses with elevated across front over along front variance during these periods inertial band pass buoyancy fluctuations often correlate with major axis currents wkb ray tracing models of propagating monochromatic plane waves exhibit horizontal phase propagation and correlations between minor axis currents and buoyancy and thus cannot explain these results models of near inertial internal waves reflected or trapped by a barotropic frontal jet produce mode like structures with short horizontal scales little horizontal phase propagation and anisotropic current ellipses aligned primarily cross front model buoyancy may correlate with one or both current ellipse components depending on the incidence angle of the wave and the degree to which it reflects completely reflected waves with horizontal scales similar to those of the front and near normal incidence angle produce current ellipses and correlation patterns consistent with the observations

a new method of reconstituting the p t conditions of fluid circulation in an accretionary prism shimanto japan from microthermometry of methane bearing aqueous inclusions in paleo accretionary prisms and the shallow metamorphic domains of orogens circulating fluids trapped in inclusions are commonly composed of a mixture of salt water and methane producing two types of fluid inclusions methane bearing aqueous and methane rich gaseous fluid inclusions in such geological settings where multiple stages of deformation veining and fluid influx are prevalent textural relationships between aqueous and gaseous inclusions are often ambiguous preventing the microthermometric determination of fluid trapping pressure and temperature conditions to assess the p t conditions of deep circulating fluids from the hyuga unit of the shimanto paleo accretionary prism on kyushu japan we have developed a new computational code applicable to the h2o ch4 nacl system which allows the characterization of ch4 bearing aqueous inclusions using only the temperatures of their phase transitions estimated by microthermometry tmi the melting temperature of ice thyd the melting temperature of gas hydrate and th aq homogenization temperature this thermodynamic modeling calculates the bulk density and composition of aqueous inclusions as well as their p t isochoric paths in a p t diagram with an estimated precision of approximatively 10 we use this computational tool to reconstruct the entrapment p t conditions of aqueous inclusions in the hyuga unit and we show that these aqueous inclusions cannot be cogenetic with methane gaseous inclusions present in the same rocks as a result we propose that pulses of a high pressure methane rich fluid transiently percolated through a rock wetted by a lower pressure aqueous fluid by coupling microthermometric results with petrological data we infer that the exhumation of the hyuga unit from the peak metamorphic conditions was nearly isothermal and ended up under a very hot geothermal gradient in subduction or collision zones modeling aqueous fluid inclusions in the ternary h2o ch4 nacl system and not simply in the binary h2o nacl is necessary as the addition of even a small amount of methane to the water raises significantly the isochores to higher pressures our new code provides therefore the possibility to estimate precisely the pressure conditions of fluids circulating at depth

trapped near inertial waves and enhanced chlorophyll distributions waves with near inertial frequencies were observed along a front associated with a large mesoscale feature in the sargasso sea during the late summer of 1987 high subsurface chlorophyll concentrations occurred on the edge of this front coincident with the wave packets the amplitude of the waves increased with time and kinetic energy propagated downward reducing 20 m richardson numbers in the thermocline to 1 or less chlorophyll levels were episodic showing no periodicity coincident with wave dynamics however on two occasions chlorophyll concentration increased from 1 mg chl m 3 several hours after the waves penetrated the thermocline it was hypothesized that mixing associated with shear instabilities stimulated new production a diffusivity model combined with nutrient data produced a phytoplankton bloom that accounted for only one of the maxima the other increase in chlorophyll may have been the result of horizontal advection of the wave packets near the front

origin of the co2 only fluid inclusions in the palaeoproterozoic carara vein quartz gold deposit ipitinga auriferous district se guiana shield brazil implications for orogenic gold mineralisation abstract the carara gold deposit located in the ipitinga auriferous district south eastern portion of the guiana shield northern brazil is a typical orogenic greenstone hosted auriferous quartz vein mineralisation was post metamorphic and syn tectonic in relation to the host palaeoproterozoic ca 2 03 ga shear zone developed close to the tectonic boundary between a palaeoproterozoic continental arc and an archaean block the deposit style is very simple consisting of a quartz vein and its hydrothermal envelope which is composed of muscovite and tourmaline sulphides are rare muscovite and tourmaline in addition to gold fill small fractures in the quartz vein the fluid inclusion assemblage trapped in high and low grade portions of the au quartz vein is rather enigmatic consisting of one phase co 2 inclusions with no visible water at room or sub zero temperatures although small amounts of water have been detected by micro raman analysis in this aspect carara differs from the other gold showings in the same district which are characterized by abundant aqueous carbonic fluid inclusions the carbonic fluid is composed predominantly of co 2 in addition to 2 and traces of ch 4 and c 2 h 6 the carbonic fluid show very variable densities which is interpreted to result from post entrapment re equilibration inclusions in the high grade quartz are the densest 0 89 to 1 07 g cm 3 and with less effects of re equilibration these inclusions approximate the physico chemical characteristics of the parental fluid that started to be trapped at least around the amphibolite facies metamorphic conditions and then followed a retrograde path most of the inclusions appear to have been trapped and or re equilibrated at 350 to 475 c and 1 8 to 3 6 kbar which implies a 7 to 12 km depth of vein formation and gold mineralisation both phase separation of a carbonic aqueous fluid x co 2 0 8 and the existence of an originally co 2 dominated fluid could account for the observed fluid inclusion properties and the absence of h 2 o bearing inclusions in the mineralised vein the fluid inclusion characteristics combined with published geological and isotopic information indicate a deep seated source for co 2 that could be mantle magmatic or metamorphic in origin we suggest that the likely sources are fluid produced by the 2 07 ga old charnockites that occur in the region and or the coeval high grade metamorphism that is widespread in the guiana shield

gold transporting hydrothermal fluids in the earth s crust an introduction hydrothermal ore deposits that are exploited for gold include both gold only deposits such as orogenic deposits and gold bearing examples of the common hydrothermal deposit types that are formed around upper crustal magmatic centres in particular porphyry and epithermal deposits fluid inclusion data have shown that ore fluids of gold only deposits are compositionally distinct compared to fluids of other deposit types fluids of the latter deposit types are in contrast not distinctive and recent research has been focussed on relating gold content to geochemical and petrological aspects of related magmatic systems and to fluid evolution on migration through the crust this special publication includes an up to date summary of thermodynamic parameters of aqueous au species at high temperatures and pressures a dataset of fluid inclusion properties and compositions from orogenic deposits of different parts of the world several comprehensive case studies of different types of gold deposits and their fluids from the usa brazil egypt slovakia and bulgaria and numerical modelling aimed to define key parameters that affect fluid flow and gold deposition at a range of scales historical and disciplinary context the majority of gold deposits of the earth s crust are generated by fluxes of hot aqueous hydrothermal fluids that are efficiently focussed within relatively small volumes of rock a proportion of this gold is extracted from hydrothermal deposit types such as iron oxide copper gold iocg deposits porphyry deposits and lowand high sulphidation epithermal deposits as a co product with other metals most commonly with copper or silver the other group 12 elements a similar proportion is however a product of gold only hydrothermal deposits including orogenic gold intrusion related gold irgd and carlin type gold deposits in these gold only deposit types au is in most cases not only the only commodity of economic interest in the ore but we can infer from the available multi element compositional data on fluid inclusions that it is the only commodity of interest transported in the hydrothermal fluids of these deposits e g yardley et al 1993 su et al 2009 gold only hydrothermal deposits are thus environments in which gold is very effectively fractionated from other metals presumably as a consequence of gold s unique chemical properties such as high electronegativity and the tendency to form bonds with strong covalent character e g crerar et al 1985 and the strength of relativistic effects on bonding behaviour e g pyykko 2012 the affinity of gold with reduced sulphur in hydrothermal fluids was first experimentally demonstrated by seward 1973 and has been confirmed in all subsequent experimental studies see pokrovski et al 2014 gold only deposits including orogenic gold deposits do appear to be products of hydrothermal fluids that are chemically distinct compared to fluids of other higher temperature hydrothermal ore deposit types including porphyry deposits epithermal deposits and greisens hypersaline fluids are absent at almost all deposits the dominant fluid contains sufficient co2 to form a carbonic phase in fluid inclusions and has relatively low salinity in contrast the fluids of gold rich epithermal and porphyry deposits are not distinct from those of typical deposits of these types at least with respect to compositional fluid parameters that can be constrained through routine microthermometry it is difficult to pinpoint who first recognized that co2 bearing and relatively low salinity ore fluids are characteristic and almost ubiquitous in orogenic gold deposits roedder 1973 in his early comprehensive summary of knowledge of fluid inclusion compositions reported that kravtsov fridman 1965 recorded high co2 in fluid inclusions in gold quartz veins and suggested that its abundance might be an effective exploration tool for gold boyer et al 1967 recognized co2bearing fluid inclusions in quartz veins and summarized the results of other similar studies to suggest a clear relation direct or indirect between gold and co2 in another early work coveney kelly from garofalo p s ridley j r eds gold transporting hydrothermal fluids in the earth s crust geological society london special publications 402 http dx doi org 10 1144 sp402 9 the geological society of london 2014 publishing disclaimer www geolsoc org uk pub ethics at universita di bologna on june 30 2014 http sp lyellcollection org downloaded from

fluid evolution and chemical controls in the fazenda maria preta fmp gold deposit rio itapicuru greenstone belt bahia brazil the fazenda maria preta fmp gold deposit is confined to two regional scale sinistral oblique brittle ductile shear zones which are located in a greenschist facies metamorphosed volcano sedimentary sequence in the northern sector of the lower proterozic rio itapicuru greenstone belt ne brazil alteration is pervasive throughout the shear zones and characterized by carbonatization and sericitization of intermediate volcanic volcaniclastic and sub volcanic rocks the orebodies are mainly shear veins hosted by or directly associated with highly deformed carbonaceous volcaniclastic rocks breccia and stockwork systems or disseminations in felsic and mafic sub volcanic bodies native gold appears as free grains finely disseminated in the quartz veins or closely related to arsenopyrite pyrite pyrrhotite sphalerite and fe chlorite in the carbonaceous wallrocks fluid inclusion studies by microthermometry and laser raman microspectroscopy revealed that the vein quartz is largely dominated by primary pseudosecondary and rarely secondary populations of co2 ch4 n2 inclusions type i whereas primary groups of low salinity 6 wt eq nacl h2o co2 ch4 n2 inclusions type ii comprise the dominant inclusion type in only a few veins the thco2 l v l data indicated a variation in the co2 density of 1 05 to 0 60 g cm3 for the type i inclusions and conversely a narrower range of 0 76 0 73 g cm3 for the type ii inclusions the broader variation of the co2 density for the co2 rich fluid could have been the result of trapping of the vein fluid under a variable pressure regime or by its re equilibration during continuous deformation within the shear zone domains and reduction of the overburden pressure during uplift the co2 rich fluid inclusions provide no evidence that they have been the result of h2o loss either during infiltration e g hydration reactions or after trapping of an original h2o co2 fluid accordingly the co2 ch4 n2 and the h2o co2 ch4 n2 fluids are considered as representatives of two distinct fluid regimes which were active during the gold mineralizing events within the shear zones both types of ore fluids are interpreted as part of a deep metamorphic magmatic hydrothermal system in which i a co2 rich fluid probably originated in the mantle was transported to and released in higher structural levels mainly by tonalitic granodioritic and alkaline magmas whereas ii a h2o co2 fluid generated by devolatilization reactions during the regional metamorphism was either directly channeled into favorable structural sites i e metamorphic fluid or absorbed and later exsolved by the crystallization of felsic magmas i e magmatic fluid sensu lato in this context gold deposition occurred between 320 c and 420 c and 2 1 to 4 4 kb and calculated values of fo2 between 10 26 5 and 10 32 4 bar reveal the relatively reducing nature of the mineralizing fluids the ore paragenesis constrains fs2 to the range of 10 10 1 10 6 5 bar for these fluids under such conditions the gold was transported mainly as bisulfide complexes by the h2o co2 fluid but in the case of the co2 rich fluid the role of thiocomplexes or some other types of ligands is obscured by the lack of high temperature experimental data deposition of the metal occurred in response to redox changes which accompanied fluid carbon interaction particularly a decrease in fo2 and fs2 of the fluid on a microscopic scale phisisorption and chemisorption processes at the fluid iron sulfide interface may have further enhanced the deposition of the gold particularly on the surfaces of precipitating pyrite and arsenopyrite

metamorphic and post metamorphic fluid flow in the low grade rocks of the harlech dome north wales a combination of fluid inclusion stable isotope and geochemical techniques has been used to study the nature of fluids present and their behaviour during caledonian low grade metamorphism of the harlech dome north wales fluid inclusion studies show that in most of the metasedimentary sequence the peak metamorphic fluid was an aqueous na k cl brine but in the graphitic clogau formation and in parts of the overlying maentwrog formation immiscible h2o rich and ch4 rich fluids coexisted late stage inclusions are of calcium rich brine and a dilute aqueous fluid the chemical composition of chlorite in metamorphic veins and rocks varies between different formations and quartz oxygen isotopic compositions show considerable variation between different units both of these features are taken to indicate that there was little or no pervasive movement of fluid between different units at the peak of metamorphism after the metamorphic peak there was focused flow of fluid upward through the sequence along fractures in response to end caledonian uplift and unloading where the migrating fluid crossed the graphitic shales interaction between the fluid and the shales gave rise to the formation of the auriferous veins of the dolgellau gold belt subsequent to this mineralizing event there was widespread development of 18o enriched calcites and micas in the case of vein minerals it is possible that these crystallized directly from late stage fluids at lower temperature than the quartz in the same veins alternatively the original vein minerals may have re equilibrated with later 18o enriched or cooler fluid in the case of muscovites in the rock matrix it is proposed that the isotopically heavy compositions are the result of re equilibration of initially light grains with an introduced fluid requiring considerable influx of fluid this event may relate to either of two late stage fluids observed as inclusions

fluid inclusion evidence for the physicochemical conditions of sulfide deposition in the olympias carbonate hosted pb zn au ag sulfide ore deposit e chalkidiki peninsula n greece the olympias pb zn au ag sulfide ore deposit e chalkidiki n greece is hosted by marbles of the polymetamorphic kerdilia formation of paleozoic or older age the geologic environment of the ore also comprises biotite hornblende gneisses and amphibolites intruded by tertiary pegmatite aplite dikes lamprophyre dikes the 30 ma stratoni granodiorite and porphyritic stocks only limited parts of the deposit display shear folding and brecciation most of it is undeformed microthermometry of fluid inclusions in gangue syn ore quartz indicates three types of primary and pseudosecondary inclusions 1 h2o rich 1 18 wt nacl equivalent 3 6 mol co2 2 h2o co2 inclusions 4wt nacl equivalent with variable co2 contents coexisting in both undeformed and deformed ore 3 aqueous highsalinity 28 32 wt nacl equivalent inclusions found only in undeformed ore type 2 inclusions are differentiated into two sub types 2a relatively constant co2 content in the narrow range of 8 15 mol and homogenization to the liquid phase 2b variable co2 content between 18 and 50 mol and homogenization to the vapor phase type 1 and 2b inclusions are consistent with trapping of two fluids by unmixing of a high temperature saline aqueous co2 bearing fluid of possible magmatic origin probably trapped in type 2a inclusions fluid unmixing and concomitant ore mineralization took place at temperatures of 350 30 c and fluctuating pressures of less than 500 bar for both undeformed and deformed ores the wide salinity range of type 1 inclusions probably represents a complex effect of salinity increase due to fluid unmixing and volatile loss and dilution due to mixing with low salinity meteoric waters high solute enrichment of the residual liquid due to extreme volatile loss during unmixing may account for high salinity type 3 inclusions the olympias fluid inclusion salinity temperature gradients bear similarities to analogous gradients related to pb zn ores formed in granite hosted low t distalskarn skarn free carbonate replacement and epithermal environments

sand composition in an iberian passive margin fluvial course the tajo river the tajo river the 10th largest river in europe drains part of the western passive margin of europe that includes multiple tectonic elements of the iberian plate modern fluvial sand composition in the tajo river drainage basin reflects the nature of the source region which lies in the central part of the iberian peninsula four fluvial petrographic provinces a b c and d can be established in the tajo drainage basin corresponding well with the four principal structural units drained 1 the iberian range 2 the hesperian massif 3 the tertiary tajo basin and 4 the neogene santarem lisboa basin province a corresponds to the tajo river head and is characterized by quartzolithic sedimenticlastic sands qm67f4lt29 and rs79rg3rm18 these sands have been derived from diverse mesozoic siliciclastics and carbonates of the iberian range province b appears in the upper reaches of the tajo river course and is quartzofeldspathic qm57f34lt9 with diverse rock fragments rs34rg23rm43 sources are hercynian granitoids and metasediments and neogene clastics and minor carbonates of the tertiary tajo basin province c extends along the middle course of the tajo river with quartzofeldspathic metamorphiclastic sand modes qm60f33lt7 rs4rg21rm75 the sources are metamorphic rocks intruded by plutonites of the hesperian massif province d is quartzofeldspathic qm55f39lt6 with a dominance of phaneritic rock fragments rs5rg33rm62 and corresponds to the lower reaches of the tajo river where siliciclastic deposits of the neogene santarem lisboa basin are the main sources sands plot on provenance discrimination diagram qmflt within the recycled orogen field tajo river head and continentalblock fields upper middle and lower course in addition we have proven the usefulness of the rsrgrm diagram to discriminate the defined fluvial provinces originating from heterogeneous parent rock textures and mineralogy climate does not exert any strong influence on the petrogenesis of the tajo river drainage basin sand and erosion in the source areas may be described in terms of weathering limited denudation regime by contrast mixing with tributary supplies is the main process that modifies composition in the tajo river sand the establishment of fluvial provinces related to the main bedrock structural units reflects the great relevance of tributaries from each province in the generation of the tajo river sand and the low significance of inherited sandy load from previous provinces the abundance of granitoid rock fragments rsrgrm rg in fluvial sand of both tributaries and main channel of the tajo river drainage basin faithfully represents the relative abundance of granodiorite monzogranite bedrock exposure in each subbasin metasedimentary and metamorphic bedrock outcrop area is overrepresented by metamorphic rock fragments rsrgrm rm in both sand from tributaries and from the tajo main trunk river this is manifested by differences of 18 23 between means of metasedimentary outcrop area and the rsrgrm rm mean in the sand from provinces b and c d respectively sedimentary mainly carbonate outcrop area is underrepresented or not represented by sedimentary rock fragments rsrgrm rs in sand of the tajo river this underrepresentation causes a difference between means of sedimentary outcrop area and the rsrgrm rs mean of 21 17 1 and 10 7 in sands from province a b and c d respectively this fact confirms the rapid loss of these grains during transport because of their labile nature

internal inertial waves in a surgasso sea front abstract this work examines the presence of internal inertial waves in a front in the north atlantic subtropical convergence zone results of doppler shear profiler and towed thermistor chain surveys are displayed to document the position and magnitude of the front objective maps of the total measured velocity are computed and subtracted from the observed velocity fields the remaining wave signal is processed to yield horizontal towed and vertical dropped kinetic energy spectra across the front from these rotary spectra are also computed along the line of tow and in the vertical to determine the horizontal and vertical anisotropy it is found that several nearly monochromatic waves are propagating northward and southward from the front with horizontal length scales of 32 50 km it was also discovered that the region of anticyclonic frontal vorticity exhibits an excess of downgoing energy at the longest vertical wavelength thus sampled 50 m while the region of cyclonic vorticity possesses more

the gurupi belt northern brazil lithostratigraphy geochronology and geodynamic evolution abstract the gurupi belt is located in northern brazil on the southern margin of the sao luis craton which is dominated by juvenile calc alkaline rocks formed in intra oceanic island arcs between 2240 and 2150 ma the gurupi belt consists of i small lenses of an archean metatonalite of 2594 ma ii calc alkaline ttg tonalites and gneisses of 2147 2168 ma and juvenile nd isotope signature formed in intra oceanic arc setting iii an i type monzogranite that intruded by ca 2159 ma formed by the reworking of the oceanic arcs iv a metavolcano sedimentary succession with calc alkaline volcanic rocks of 2148 2160 ma and juvenile nd isotope signature formed in arc systems v several peraluminous muscovite bearing collision type granites of 2070 2100 ma with nd isotopes indicating variable reworking partial melting and or erosion of paleoproterozoic and archean crust vi a sub greenschist to greenschist facies supracrustal sequence of unknown age tentatively considered to be older than 2159 ma vii an amphibolite facies metasedimentary sequence in which the youngest detrital zircon has age of 1100 ma and nd isotopes and sedimentological evidence indicating archean paleoproterozoic mesoproterozoic and neoproterozoic sources viii a deformed gneissic nepheline syenite of 732 ma formed by mixing of mantle and crustal sources ix a peraluminous muscovite bearing post tectonic granite of 549 ma combined geological and geochronological information indicate that the paleoproterozoic rocks are part of a trans amazonian eburnean orogen initiated by an accretionary phase 2240 2150 ma better represented in the adjacent sao luis craton and terminated by a collisional event 2100 2080 ma that amalgamated juvenile and reworked paleoproterozoic terrains and an archean terrain existing to the south this landmass amalgamated in the paleoproterozoic broke up before 732 ma forming a rift as suggested by the emplacement of the nepheline syenite pluton the rift received detritus coming from archean paleoproterozoic mesoproterozoic and neoproterozoic sources we infer that the rift evolved to an oceanic basin and that the closure of this basin occurred at the end of the neoproterozoic 580 550 ma as part of the brasiliano pan african cycle of orogenies

fine scale temperature variability the influence of near inertial waves measurements made with a towed thermistor chain and acoustic doppler current profiler in the seasonal thermocline of the sargasso sea are examined for relationships among small scale temperature activity shear and internal wave variability patches of intense activity measuring 5 10 m high and several kilometers in length are found to persist within a near inertial wave packet the packet was tagged with a drogue and followed for about 16 hours as it was advected along an edge of a cold core ring the patches occur along surfaces of high vertical shear where the richardson number 7 m vertical resolution falls to values less than one within the patches are groups of small scale internal waves and fluid overturns the overturns are 1 3 m high and are associated with wave breaking events away from the wave packet activity levels are less and the active fraction of the water column appears to be linked to variability in the internal wave field it is conjectured that the near inertial wave patches are the same species as persistent mixing patches observed by gregg et al 1986 which were also associated with a near inertial wave

new metallogenic model of telescoped eocene miocene au u epithermal mineral deposit in the placer de guadalupe district chihuahua mexico abstract the chronological repartition of mineral deposits in mexico and the southern usa coincides with the distribution of the three main volcanic pulses of the sierra madre occidental these pulses are eocene to early miocene in age suggesting that a broad migration occurred from northwest to southeast where the last ignimbrite flare up occurred the most fertile event occurred from 36 to 28 ma and produced all of the largest ag au mining districts the placer de guadalupe au u district contain a unique association of metals with high variations in their u au ratios that are not common worldwide the uraninite population dated by wells 1930 yielded an age of ca 36 ma which is comparable to that of the volcanic intrusions and dykes dated in the district yielding ages of ca 36 ma altered uraninite cemented by gold sheets provide an age of 21 ma which is interpreted to be the age of the gold epithermal event studies of fluid inclusions in the quartz and calcite cements formed in the gold event indicate the presence of immiscible magmatic brines and co2 homogenization temperatures by halite melting range from 268 c to 305 c and 266 6 c to 283 c with salinities ranging from 35 9 to 38 9 and 36 0 to 37 5 wt eq nacl in the quartz and calcite stages respectively c o isotopic compositions of u and au calcite cements suggest a trend of low temperature alteration caused by hydrothermal fluids these c o isotopes suggest that during the gold event water rock interaction processes occurred between magmatic fluids and the carbonate host rock ree enrichment in the u calcite cement suggests that la ce enriched carbonatite volcanic formations participated in the mineralizing process the u mineralization event was controlled by 1 a metal and heat source in this case late eocene volcanism and in particular a carbonatite volcanic event 2 an efficient transport mechanism for the large scale input of meteoric water which was channeled heated and u enriched into reactivated crustal eocene faults from a deep u source to a shallow sedimentary chemical trap 3 an effective trap which is represented in this study by the presence of an organic matter rich sedimentary formation the gold mineralization event was characterized by the miocene extensional peak coupled with asthenospheric upwelling which facilitated the melting metamorphism of the lower crust and the expulsion and transport of large amounts of co2 bearing fluids to a shallow crustal level through the reactivated crustal laramide thrust faults the fluids interactions with the entire stratigraphic column from the grenvillian to the late triassic basement favored the leaching of gold and the enrichment of co2 bearing fluids gold deposition appears to be related to boiling but was ultimately favored by water rock interaction with u mineralization and the upper plomosas shale study of the au u placer de guadalupe deposit reveals evidence of a new miocene metallogenic event in central and northern mexico its genetic relationship with the basin and range bnr and rio gande rift rgr in usa and its transition from post orogenic to miocene intraplate extension in mexico provides a new perspective regarding the exploration of miocene gold epithermal deposits in northern mexico and the southern usa

the hydrothermal fluid of archaean lode gold deposits at different metamorphic grades compositional constraints from ore and wallrock alteration assemblages a low salinity mixed aqueous carbonic fluid is common to all archaean lode gold deposits throughout the range of mineralising conditions from sub greenschist to lower granulite facies temperatures alteration assemblages and fluid inclusion data give constraints on the fluid composition fluid xco2 is 0 1 0 3 in typical greenschist facies mesothermal deposits at higher temperatures the assemblages are consistent with formation from a fluid of similar composition but slightly higher or lower xco2 cannot be ruled out and fluid inclusion data indicate that ch4 may be an important component in ore fluids at these temperatures fluid ph is neutral or weakly alkaline at all conditions a range of relative oxidation states of four orders of magnitude fo2 is indicated at any temperature with deposits more oxidising relative to qfm at lower temperature sulphur contents of the fluids vary from 10 to 10 3 5m s with a trend towards lower sulphur contents at lower temperatures the relative concentrations of major cations in solution are similar at all conditions with na k ca although ca may be less abundant at low temperatures the broad similarities in ore fluid composition at all temperatures give support to crustal continuum models in which archaean lode gold mineralisation involved either a single fluid moving through the middle and upper crust or derivation of ore fluids by similar processes at different crustal levels many of the compositional differences between high and lowtemperature ore fluids may be attributed to evolution of deep sourced hydrothermal solutions as they rise along structurally controlled conduits the constancy of major ore fluid component concentration e g co2 cl k suggests fluid buffering and high fluid rock ratios along fluid pathways fluid buffered conditions can also explain the ore fluid fo2 temperature relations with equilibria between oxidised and reduced aqueous carbon or sulphur species controlling the oxidation state in contrast the concentrations of components present in lesser abundance in archaean gold ore fluids e g s ca h were probably controlled either by saturation of one or more mineral phases brought on by decreasing temperature or were rock buffered through fluid rock reactions extrapolation to high temperatures of the k na and ca contents of the gold bearing fluids indicates that their composition is consistent with derivation from or final equilibration with rocks of intermediate granitic composition thus giving support to isotopic and geological arguments for ore fluid source regions external to the greenstone belts the fluid oxidation states are characteristic of a wide range of potential source rocks including mantle derived igneous rocks calc alkaline granitoids and magmas and seaflooraltered metabasalts strongly oxidised magmatic sources or unusually oxidising source processes e g co2 streaming during granulitisation of the lower crust are therefore not required in the genesis of arch an lode gold deposits

magmatic hydrothermal evolution of highly fractionated granites evidence from the kuiqi miarolite in fujian province se china abstract the kuiqi miarolite a highly evolved alkaline granite pluton is situated in fujian province southeastern china quartz crystals from the kuiqi miarolite contain abundant inclusions which have preserved a complete record of the magmatic hydrothermal evolution five inclusion type were identified i e the melt m type melt fluid ml type daughter mineral bearing s type vapor rich v type and aqueous l type inclusions integrated petrographic microthermometric and laser raman spectroscopy studies demonstrate that the whole magmatic hydrothermal evolution at kuiqi comprises three stages i e the magmatic magmatic hydrothermal and hydrothermal stages the m type inclusions minimal trapping temperatures ca 710 800 c represent the melts entrapped at the magmatic stage of crystallization while the occurrence of euhedral prismatic arfvedsonites in these melt inclusions indicates that the granitic magma was probably volatile rich at the magmatic hydrothermal stage both the ml type inclusions t h ca 500 710 c and coexisting m and v type inclusions reflect the presence of late magmatic fluid circulation and melt volatile immiscibility exhibiting a transition toward the hydrothermal stage at the hydrothermal stage the pressure and temperature 700 485 c drop may have led to oversaturation of the primary saline fluids resulting in the phase separation a highly saline and a volatile rich fluid occurred accompanied by the widespread vapor brine immiscibility the l type inclusions in the miarolitic quartz display bimodal salinity distribution the t h and salinity of the inclusions at the bottom l 1 miarolitic quartz are ca 303 427 c and ca 6 6 17 9 wt nacl equiv respectively while that of the inclusions at the top l 2 are ca 165 232 c and ca 0 2 5 7 wt nacl equiv respectively this indicates a drop of fluid temperature and salinity during the miarolitic cavity formation moreover the low homogenization temperatures and salinities of the l type inclusions suggest an influx of meteoric water during the late hydrothermal evolution stage

multi stage cu remobilization of the huping metamorphic hydrothermal deposit in the southern north china craton abstract the zhongtiao region is a well endowed cu metallogenic province in the southern north china craton and contains a large number of early precambrian cu deposits of different styles most of which have been subjected to the ca 1 85 ga regional metamorphism however whether there was any role for the proterozoic metamorphism on the extensive cu mineralization is yet to be well understood this paper presents an integrated investigation on the field geology mineral chemistry fluid inclusion and c h o s isotopes of the huping metamorphic hydrothermal deposit in the neoarchean paleoproterozoic zhongtiao metamorphic terranes and reveals multi stage cu remobilization that formed and upgraded the cu deposits in the region we identified three stages of syn to post metamorphic cu remobilization transportation in the huping cu deposit including i early mechanical transport ii intermediate metamorphic hydrothermal remobilization and iii late meteoric fluid incursion in stage i sulfides were remobilized and transported internally under lower greenschist facies metamorphism forming the veinlet disseminated ores and chalcopyrite avg 34s 2 1 similar to the chlorite amphibole schist wall rocks in stage ii the immiscibility of metamorphic fluids avg 18o 4 6 and d 56 6 from the metamorphic terranes triggered the precipitation of higher 34s chalcopyrite avg 8 0 led by the incorporation of extra sulfur during the fluid migration in stage iii incursion of meteoric fluids into the waning metamorphic hydrothermal system formed the barren quartz calcite veins avg 18o 0 09 and 13c 0 88 during these cu remobilization processes the earlier formed sulfides were chemically stable during the mechanical transfer by regional metamorphism and deformation subsequently the immiscibility of metamorphic fluids induced significant cu remobilization and precipitation in the metamorphic hydrothermal system we thus propose a model of multi stage mechanical and chemical cu remobilization for the huping cu deposit which highlights the crucial impacts of metamorphic remobilization processes on the regional cu mineralization in the zhongtiao region

evolution of high temperature hydrothermal fluids associated with greisenization and feldspathic alteration of a tin mineralized granite northeast queensland greisenization albitization and k feldspathization occur as pervasive background alteration and fracture controlled selvage style alteration in the go sam granite in the herberton mount garnet tin fields of northeast queensland optical sem and microthermometric investigations of fluid inclusions principally from vug filling minerals in selvage style alteration permit interpretation of the nature and evolution of hydrothermal fluids responsible for alteration of the granite saline hydrothermal fluids are dominated by na k ca fe chloride solutions with mg mn zn si al th ce and la relatively minor but important components salinities of up to 70 wt percent total dissolved salts have been calculated using the phase volume method indicated trapping temperatures of 600 degrees to 650 degrees c for many saline inclusions in vug filling minerals from feldspathic rocks record minimum temperatures for feldspathic alteration inferred temperatures for greisenization are similar and slightly lower 450 degrees 525 degrees c trapping temperatures and the composition of fluids in saline inclusions suggest late magmatic to early postmagmatic alteration of the granite by predominantly magmatic fluids inclusions containing relatively dilute fluids of possible meteoric origin homogenize between 100 degrees and 400 degrees c salinities as low as 2 equiv wt percent nacl are indicated and significant co super 2 3 hco super 3 or so super 2 4 may be present associated vapor rich inclusions indicate that the dilute fluids were probably boiling between 300 degrees and 400 degrees c a continuous range of salinities from dilute fluids to saline fluids has been found in the inclusions investigated dilution of very saline high temperature fluids could have occurred by separation of dissolved components as the fluid cooled and by mixing with dilute fluids below 400 degrees c data from fluid inclusions in magmatic quartz from the go sam granite are similar to those obtained from vug filling minerals in fracture controlled metasomatic rocks they suggest that pervasive alteration and fracture controlled alteration occurred contemporaneously and as a result of interaction with the same fluids consistently high temperatures inferred for the formation of all feldspathic rocks and associated greisens do not fit an established soviet model which emphasizes falling temperatures for the origin of comparable rocks a tentative model which emphasizes high temperature evolution of hydrothermal fluids due to changes in chemical parameters ph salinity na k f sub f 2 and confining pressures is discussed

geology and stable isotope o h c s constraints on the genesis of the cachoeira gold deposit gurupi belt northern brazil the cachoeira gold deposit is one of several large n20 tonnes au shear zone hosted hydrothermal gold deposits of the proterozoic gurupi belt in northern brazil o h c and s isotope compositions of carbonate silicate and sulfide minerals and from graphite and inclusion fluids from this deposit have been measured in order to infer the composition of ore forming fluids the data show small variation at the deposit scale irrespective of host rock calculated y 18 o values of h2o in the fluid in equilibrium with quartz hydrous silicates and carbonates are respectively 6 2 to 12 4x 5 0 to 9 0x and 5 9 to 11 0x smow the ydh2o of inclusion fluids is 22x whereas values for chlorite and white mica are 16x and 20 to 28x smow respectively these values are compatible with a metamorphic origin which is in agreement with the postmetamorphic timing of the mineralization the calculated y 13 c value of co2 of the fluid in equilibrium with the carbonates is from 9 5x to 12 7x pdb whereas the graphite bearing host rocks have y 13 c value of graphite carbon of 29 7x the calculated y 34 so f h2s of the fluid varies mainly between 0 7x and 5 5x cdt and is interpreted as reflecting a magmatic or average crustal source for sulfur the restricted isotopic compositions indicate a relatively homogeneous fluid and deposition under restricted temperature conditions nonetheless a relatively wide temperature range of 272 383 8c is estimated for the ore bearing fluid using the quartz dolomite oxygen isotope thermometer collectively the data indicate that gold was transported as a reduced sulfur complex by a metamorphic fluid having a near neutral ph at relatively low co2 furthermore the data suggest that gold was deposited during the structural evolution of the associated shear zone probably as a result of sulfidation and carbonatization reactions with the fe and c rich host rocks which resulted in changes of the ph and in the redox state of the ore fluid d 2005 elsevier b v all rights reserved

statistics of mixing patches observed in the sargasso sea temperature measurements made with a towed thermistor chain in the seasonal thermocline of the sargasso sea have been converted to sections of fine structure activity by normalizing values of meter scale horizontal fluctuations by the local vertical gradient individual patches of high activity are then separated from background and examined for length l height h aspect ratio l h and signal intensity over the range 0 5m h 20m and 30 m l 2 km the aspect ratio tends to be about 100 similar to reports of turbulent patches measured with velocity microstructure profilers numbers of patches decrease with increasing patch height and length and large patches tend to have higher activity levels

hydrothermal transport and depositional processes in archean lode gold systems a review abstract compelling evidence now exists for the formation of archean lode gold deposits over a substantial range in metamorphic conditions and crustal depth the commonality of ore fluid isotopic and geochemical characteristics the extreme fluid rock ratios within actual ore zones and the observed depth continuity within individual orebodies all suggest that these deposits formed within vertically extensive crustal scale hydrothermal systems calculations based on new thermodynamic data and estimated ore fluid conditions suggest that gold would have been transported as au hs 2 over most of this range gold transport in the ore fluids that formed some diopside and diopside k feldspar class deposits t 550 c would have been as aucl2 whereas the au hs complex may have been significant in some of the lower temperature 270 c less alkaline ore fluids the high solubility of gold in lode gold ore fluids at amphibolite facies conditions 10 s to 1000 s ppb suggests that fluids may have been undersaturated in gold within their source regions promoting the ore fluid s capacity to retain gold in solution over the large transport distances involved ore depositional mechanisms were also likely to vary between crustal levels fluid rock interactions and wallrock sulphidation in particular appear to be the most important type of precipitation mechanism however with decreasing depth of formation the scope of other depositional mechanisms notably phase separation and fluid mixing becomes greater

metallogenesis of the french part of the variscan orogen part ii time space relationships between u au and snw ore deposition and geodynamic events mineralogical and upb data abstract mineralogical geochemical structural and isotopic u pb studies were carried out on representative uranium and gold deposits from the french part of the variscan orogen results are compared with complementary data from the literature in order to propose a reconstruction of the metallogenesis in the variscan terranes with a particular emphasis on u deposits the data show that the early metal concentrations or pre enrichments in the terranes are affected by successive metallogenic stages which caused significant metal transport and deposition thus the significant geodynamic events which affected the variscan terranes were responsible for multistage metal deposition or alteration of the early concentrations and for the superimposed features of the metal deposits u pb geochronological results complemented by a compilation of geochronological data on u and pb zn ba f deposits show that three major stages of u deposition took place in western europe in the periods 325 300 ma 290 260 ma and 190 170 ma in addition small uranium mineralization events have been dated at 425 ma 90 110 ma and as tertiary about 40 ma the permo stephanian stage is associated with late brittle deformation associated with major shear zone movements and constitutes the major stage of u concentration the jurassic phase has a prominent part in the hydrothermal remobilization of uranium and in f ba pb zn deposition throughout western europe especially in the eastern part of the massif central other stages correspond to subordinate uranium migration within variscan terranes during earlier or later geodynamic phases the silurian metamorphism in vendee and the mesozoic to tertiary tectonic movements related to the pyrenean or alpine orogenies in the south eastern part of the massif central and in the alps data available on au and sn w as sb deposits have been considered for comparison with the u metallogenesis stages related to the deposition of such metals display significant similarities with those related to uranium deposition they occurred mostly during visean to permian events related to the intrusion of the late visean sn w and late carboniferous sn w li f granitoids and to the late brittle deformation stages which affected the hercynian basement in the vicinity of major shear zones au as sb however the significant discrepancies between the physical chemical conditions of solubilization transport and deposition of the metal led to distinct deposit location independently of the metal source location within the terranes

mineralogical fluid inclusion and stable isotope characteristics of birimian orogenic gold mineralization at the morila mine mali west africa abstract gold mineralization at morila is hosted in flat lying meta graywacke associated with a birimian aged massigui schist belt in mali three major events of deformation metamorphism fluid flow d 1 d 2 and d 3 are recognized at morila with mineralization associated with various increments of deformation and fluid flow during d 2 three distinct vein sets v 1 v 3 associated with d 1 d 3 respectively have also been recognized v 1 vein sets are thin poorly defined quartz feldspar metamorphic segregations broadly parallel to the regional fabric v 2 veins are generally boudinaged foliation parallel quartz feldspar veins or occur as felsic melt segregations in the form of quartz k feldspar muscovite biotite blebs located essentially within the ore zone v 3 veins occur as sub parallel to high angle biotite arsenopyrite gold veins that appear to be extensional in nature the ore zone is characterized by compositionally distinct biotite higher mgo and lower feo and more calcic plagioclase than otherwise texturally identical minerals in the footwall and hanging wall of the mineralized zone suggesting that prograde metamorphic minerals were modified by post metamorphic mg and ca rich mineralizing fluids gold forms discrete grains in the v 2 veins or in the adjacent host rock and is closely associated with pyrrhotite and arsenopyrite gold also occurs with sb bi ore minerals in rare microfractures numerous thin biotite arsenopyrite gold veinlets cut d 1 and d 2 fabrics and often carry significant gold associated with kink bands in the d 2 fabric fluid inclusion and oxygen isotope study provide evidence that morila fluids are intermediate salinity 12 16 wt nacl equivalent nacl cacl 2 mgcl 2 h 2 o ch 4 n 2 fluids of magmatic origin 18 o water 10 9 0 3 the ore forming fluid subsequently unmixed to form a compositional range of vapor rich ch 4 n 2 dilute nacl ch 4 n 2 aqueous and liquid rich brine associated with the opening of a micro fracture network and vein development quartz biotite isotope geothermometry indicates that mineralization occurred between 350 to 450 c gold mineralization at morila was an integral part of coeval plutonism deformation and regional metamorphism while the modification of the ore fluid by unmixing was the most important factor associated with the concentration of economically viable gold grades at morila

hydrothermal alteration and cu ni pge mobilization in the charnockitic rocks of the footwall of the south kawishiwi intrusion duluth complex usa in the neoarchean 2 7 ga contact metamorphosed charnockitic footwall of the mesoproterosoic 1 1 ga south kawishiwi intrusion of the duluth complex the primary metamorphic mineral assemblage and cu ni pge sulfide mineralization is overprinted by an actinolite chlorite cummingtonite prehnite pumpellyite quartz calcite hydrothermal mineral assemblage along 2 3 cm thick veins in calcite hosted by the hydrothermal alteration zones and in a single recrystallized quartz porphyroblast four different fluid inclusion assemblages are documented the composition of these fluid inclusions provide p t conditions of the fluid flow and helps to define the origin of the fluids and evaluate their role in the remobilization and reprecipitation of the primary metamorphic sulfide assemblage pure co2 fluid inclusions were found as early inclusions in recrystallized quartz porphyroblast these inclusions may have been trapped during the recrystallization of the quartz during the contact metamorphism of the footwall charnockite in the footwall of the ski the estimated trapping pressure 1 6 2 0 kbar and temperature 810 920 c conditions correspond to estimates based on felsic veins in the basal zones of the south kawishiwi intrusion fluid inclusion assemblages with co2 h2o nacl and ch4 n2 h2o nacl compositions found in this study along healed microfractures in the recrystallized quartz porphyroblast establish the heterogeneous state of the fluids during entrapment the estimated trapping pressure and temperature conditions 240 650 bar and 120 150 c for co2 h2o nacl inclusions and 315 360 bar and 145 165 c for ch4 n2 h2o nacl inclusions are significantly lower than the p t conditions 700 c and 1 6 2 kbar during the contact metamorphism indicating that this fluid flow might not be related to the cooling of the duluth complex and its contact aureole the presence of chalcopyrite inclusions in these fluid inclusions and in the trails of these fluid inclusion assemblages confirms that at least on local scale these fluids played a role in base metal remobilization no evidences have been observed for pge remobilization and transport in the samples the source of the carbonic phase in the carbonic assemblages co2 ch4 could be the graphite present in the metasedimentary hornfelsed inclusions in the basal zones of the south kawishiwi intrusion the hydrothermal veins in the charnockite can be characterized by an actinolite cummingtonite chlorite prehnite pumpellyite calcite i ii quartz mineral assemblage chlorite thermometry yields temperatures around 276 308 c during the earliest phase of the fluid flow in the late calcite ii phase high salinity 21 6 28 8 nacl cacl2 equiv wt low temperature 90 160 c primary aqueous inclusions were found chalcopyrite sphalerite millerite replacing and intersecting the early hydrothermal phases are associated to the late calcite ii phase the composition of the formational fluids in the canadian shield is comparable with the composition of the studied fluid inclusions this suggests that the composition of the fluids did not change in the past 2 ga and base metal remobilization by formational fluids could have taken place any time after the formation of the south kawishiwi intrusion sulfur isotope studies carried out on the primary metamorphic 34s 7 4 8 9 and the hydrothermal sulfide mineral assemblage 34s 5 5 5 7 proves that during the hydrothermal fluid flow the primary metamorphic ores were remobilized

link between gold provinces low salinity high temperature 200 degrees c reducing fluids are poorly represented in ore forming processes yet appear to account for 90 percent of the primary gold mined to date such fluids have been implicated in the formation of many archcan greenstone witwatersrand slate belt and epithermal gold deposits these low salinity auriferous fluids occur in variable time space lithological sequence and tectonic settings and are most easily explained by metamorphic devolatilization of mafic and or graywacke successions metamorphism of chlorite calcite albite quartz assemblages e g mafic or graywacke at the greenschist amphibolite facies boundary occurs around 480 degrees or 20 degrees c for 3 5 kbars and produces large volumes of low salinity h 2 o co 2 fluid similar in composition to those recorded in many gold deposits widespread pyrite in the above assemblage typically leads to elevated levels of dissolved sulfur such conditions are ideal for gold transport as a molecular au s complex and can lead to deposits rich in gold relative to silver and base metals deposition of gold occurs in the temperature range of 250 degrees to 400 degrees c and can be facilitated by lower temperature lower sulfur activity and changes in oxygen activity lower sulfur activity is most readily achieved by fluid interaction with fe rich host rocks with the formation of pyrite or pyrrhotite whereas lower oxygen activity is readily achieved by interaction with carbonaceous metasediments low salinity fluids produced by metamorphic devolatilization provide a common theme embracing the formation of many archcan greenstone slate belt witwatersrand and potentially epithermal gold deposits it involves the common features of high geothermal gradient low salinity fluid high au ag high au base metals and broad synchroneity with metamorphism it also accounts for the considerable variability in hosting structures detailed timing relations host rocks alteration assemblages and geologic age of different deposits interestingly the similarities are explained by deeper processes the differences by processes at or near the depositional sites

origin and evolution of ore fluid and gold deposition processes at the giant taishang gold deposit jiaodong peninsula eastern china abstract the early cretaceous taishang gold deposit is the largest deposit in the linglong goldfield jiaodong peninsula with a pre mining endowment of 326 t of gold it is hosted in the 165 150 ma linglong biotite granite and controlled by the nee to ne trending potouqing fault near the northern end of the regional zhaoping fault system hydrothermal alteration is well developed in the footwall of the potouqing fault and is characterized by a narrow zone of sericitization followed by a wider zone of silicification and an even wider zone of potassic alteration the main orebodies no i orebody comprise disseminated and stockwork veinlet systems although about 5 of the resources are in larger quartz veins no ii orebody four stages have been identified for both styles of mineralization on the basis of cross cutting relationships and mineralogical and textural characteristics pyrite quartz sericite stage 1 quartz pyrite stage 2 quartz pyrite base metal sulfide stage 3 and quartz carbonate stage 4 gold was mainly deposited in stages 2 and 3 with minor amounts in stage 1 petrographical microthermometric and laser raman spectroscopic studies on fluid inclusion assemblages in quartz and calcite from the four stages reveal three types of primary fluid inclusions type 1 h 2 o rich aqueous carbonic type 2 co 2 rich aqueous carbonic and rare type 3 carbonic inclusions stage 1 quartz primary inclusions are only type 1 inclusions with an estimated composition of 88 h 2 o 10 co 2 4 5 wt nacl equiv and 0 5 ch 4 with trapping at 336 c and 1 7 kbars the gold rich stages 2 and 3 from both orebodies typically contain primary fluid inclusion assemblages with both type 1 and 2 inclusions which show similar phase transition temperatures and were trapped between 246 and 294 c the stage 4 quartz and calcite contain only primary type 1 inclusions which are estimated to have a composition of 93 h 2 o 6 0 co 2 3 6 wt nacl equiv and trace amount of ch 4 and were trapped at temperatures of 236 c the 34 s values of hydrothermal pyrite from the four stages have a narrow range from 4 5 to 8 0 and are within the ranges for whole rock sulfides from the archean jiaodong group and magmatic pyrite from mesozoic granitoid and intermediate basic dikes the 18 o values of hydrothermal quartz range mainly from 10 9 to 12 5 and remain constant for all four stages calculated fluid 18 o values are 1 3 10 0 the d water values calculated from hydrothermal sericite range from 60 to 45 considering the fluid inclusion compositions 18 o and d compositions of ore forming fluids and regional geological events the most likely ultimate potential fluid and metal reservoirs would be the paleo pacific oceanic slab and its overlying sediments which were thrust below the high grade metamorphic rocks of the jiaodong peninsula the initial ore forming fluids were medium high temperature co 2 rich and low salinity h 2 o co 2 nacl ch 4 homogeneous fluids over the duration of the hydrothermal system the fluid remained fairly consistent in p t x although becoming slightly more water rich during final post ore activity fluid immiscibility occurred during stages 2 and 3 ore deposition at pressures that fluctuated strongly from 1700 to 580 bars during hydrofracturing the hs 2 ion was the most probable gold transporting complex at taishang wall rock sulfidation and episodic pressure drops with associated fluid unmixing and other chemical changes were the two main mechanisms of ore deposition

fluid regimes during late stages of a continental collision physical chemical and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the central alps switzerland fluid evolution during neo alpine metamorphism during late stages of the continental collision between europe and africa was studied by analyzing fluid inclusions in alpine fissure quartz collected in forty nine localities along a geotraverse through the central alps switzerland the methods employed include microthermometry micro raman spectroscopy k na thermometry and stable isotope analysis early fluid inclusions provide evidence of close to peak metamorphic temperatures of the late tertiary or neo alpine metamorphic event fluid composition evolved along the geotraverse from north to south as follows higher hydrocarbons were dominant in the low and medium grade diagenetic zones methane was the main volatile in the high grade diagenetic and low grade anchizone water dominated in the highgrade anchizone and low grade epizone with co2 10 mol in the high grade epizone and in the mesozone higher hydrocarbons and ch4 were the products of kerogen maturation and cracking of preexisting petroleum large water supplies originated from the dehydration of cooler metasedimentary rocks that were overthrust by crystalline basements of the lepontines aar and gotthard massifs carbon isotope analyses suggest that the co2 component was derived from oxidation of graphitic matter especially in the vicinity of sulfate bearing metasediments and from decarbonation reactions in the aar and gotthard massifs as well as in the helvetic axen nappe and its underlying north helvetic flysch high fluid pressures prevailed and favored nappe transport by contrast in the southern lepontine area very low early fluid pressures were probably related to dry rocks and scarce metasediments and to high geothermal gradients that resulted from intense uplift and erosion between 26 and 18 ma retrograde fluid evolution was recorded by a succession of fluid inclusion populations in each alpine fissure it was controlled by uplift and cooling and characterized by decreasing contents of volatiles and an increase in 18o of host quartz tectonic activity led to episodic pressure drops of at least 0 5 to 2 kbar and promoted fluid unmixing channelized flow and rapid growth of skeletal quartz channelized rather than pervasive fluid migration at temperatures 450 c and under conditions of brittle deformation is documented by episodic increases in salinity and by fluid flushing through the massifs there is stable isotope evidence for involvement of meteoric water only in late crystallizing quartz formation of alpine fissures and fissure minerals was the result of a unique coincidence of late continental collision 450 c fluid expulsion from overthrust metasediments uplift and erosion

p t x conditions of hydrothermal fluids and precipitation mechanism of stibnite gold mineralization at the wiluna lode gold deposits western australia conventional and infrared microthermometric constraints the wiluna lode gold deposits are located in the archean wiluna greenstone belt in the northern sector of the norseman wiluna belt in the yilgarn craton of western australia they are hosted in subgreenschist facies meta basalts and controlled by the wiluna strike slip fault system and associated shear veins and breccias the 13 individual lode gold deposits have produced around 115 t au from 1901 to 1946 and 1986 to today historically they also produced 38 3 t as and 3 5 t sb gold formed in two stages stage 1 gold pyrite arsenopyrite is finely disseminated in the wallrock and breccia fragments whereas stage 2 gold stibnite is located in massive shear veins and breccia matrix as fracture fill and in banded colloform textured veins stibnite gold orebodies only occur in some of the deposits e g moonlight and northern part of the west lode and also display a restricted vertical extent being preserved only in the uppermost 200 m of stibnite bearing lodes petrographic conventional and infrared microthermometric and laser raman analysis on stibnite bearing quartz veins and breccias reveal that the antimony and gold rich hydrothermal fluid was of mixed h2o nacl co2 ch4 type microthermometric measurements reveal maximum homogenization temperatures of 340 c average 290 25 c and a wide range of salinities between 0 2 and 23 eq wt nacl aqueous carbonic fluid inclusions contain variable xco2 ch4 0 03 to 0 82 with the carbonic phase containing a maximum xch4 of 0 21 combined petrographic and microthermometric evidence suggests that the fluid inclusion properties reflect fluid immiscibility of a low salinity medium xco2 ch4 homogeneous parent fluid at about 290 c and pressures between 700 and 1 700 bar fluid immiscibility was triggered by cyclic pressure release during fault zone movement the decompression adiabatic cooling of the hydrothermal fluids shifted the ore fluid to lower temperatures significantly reduced the degree of stibnite undersaturation and caused stibnite to precipitate the deposition of stibnite reduced the ore fluid h2s concentration thereby destabilized gold bisulfide complexes in solution and caused gold precipitation locally this mechanism explains the intimate spatial association of stibnite and gold in quartz veins and breccias in the stibnite gold orebodies at wiluna

ore fluids of orogenic gold deposits of the gurupi belt brazil a review of the physico chemical properties sources and mechanisms of au transport and deposition

geochemistry and zircon geochronology of paleoproterozoic granitoids further evidence on the magmatic and crustal evolution of the sao luis cratonic fragment brazil abstract the tromai intrusive suite is the predominant exposed unit of the sao luis cratonic fragment in northern brazil the suite forms batholiths and stocks of granitoids that were emplaced between 2168 4 ma and 2149 4 ma and intruded a 2240 5 ma old metavolcano sedimentary sequence the batholiths are composed of a variety of petrographic types that have been grouped in three sub units based on the predominant petrographic type and named cavala tonalite bom jesus granodiorite and areal granite from the more primitive to the more evolved phases in addition to subordinate shallow felsic intrusions the tromai suite is an expanded magmatic association comprising minor mafic rocks to predominantly intermediate and felsic low to high k and metaluminous to weakly peraluminous granitoids that follow a na enriched calc alkaline trend combined rock association geochronology nd isotopes and geochemical signature indicate that the tromai suite formed from magmas derived from juvenile protoliths modified by fractional crystallization the juvenile protoliths included ocean plate mantle wedge and minor sediments the data also indicate an intra oceanic arc setting that possibly transitioned to a continental margin and that the tromai intrusive suite records the main accretionary stage of the rhyacian orogen ca 2 24 2 15 ma that culminated with a collision stage at about 2 1 ga and gave rise to the present day sao luis cratonic fragment this time interval is coincident with the main period of crustal growth in the south american platform and in the paleoproterozoic terranes of the west african craton the beginning of this period is also coincident with the end of a period in which only minor amounts of juvenile crust is found worldwide the negra velha granite is a distinct unit that forms a few stocks that intruded the granitoids of the tromai suite between 2076 and 2056 ma ago negra velha is an association of monzogranite and subordinate quartz monzonite and syenogranite with an alkaline signature that shows high rb sr ba enrichments resembling shoshonitic associations this granite represents the post orogenic phase of the rhyacian orogenesis

composition of holocene colorado river sand an example of mixed provenance sand derived from multiple tectonic elements of the cordilleran continental margin abstract the colorado river and its tributaries drain a complex provenance that includes multiple tectonic elements of the proterozoic to phanerozoic cordilleran margin in order to provide 1 a more reliable estimate than that reported in the literature for the composition of holocene colorado river sand and 2 a standard for comparison with ancient sandstones that may contain detritus derived from a similar complex provenance 25 unconsolidated samples were collected along the lower reaches of the colorado river for detailed petrological examination each specimen was artificially consolidated with epoxy thin sectioned and stained for feldspar each author utilizing the gazzi dickinson point count method counted 400 points per sample the results from the two point count operators wer averaged the average colorado river sand in our collection is medium grained moderately to well sorted and composed of 66 2 q 18 1 f 14 7 l and 1 3 miscellaneous grains q on average is composed of 89 monocrystalline and 11 polycrystalline quartz grains the average plagioclase to total feldspar ratio is 0 66 and the average unstable aphanitic rock fragment population l consists of 6 metamorphic lm 43 volcanic lv 51 sedimentary ls and 1 alterite fragments on the qfl provenance discrimination diagram developed by w r dickinson and associates our point count data plot entirely within the recycled orogen field w r dickinson and colleagues ascribed such provenances to subduction complexes collision orogens and foreland uplifts ass ciated with fold and thrust belts rocks in the colorado river drainage basin however include 1 remnants of precambrian crystalline rocks which form a part of cratonal north america 2 miogeoclinal and platformal sequences that developed along the north american continental margin during paleozoic time 3 deformed paleozoic and mesozoic sedimentary successions that make up the sevier laramide fold and thrust belt 4 mesozoic and cenozoic sedimentary fill of the sevier foreland basin 5 cenozoic basement cored uplifts that formed during the laramide orogeny 6 plutonic and volcanic rocks of the mesozoic and cenozoic cordilleran continental margin magmatic arc and 7 cenozoic sedimentary and volcanic rocks associated with extension and dextral shear along the cordilleran co tinental margin thus the qfl compositions of holocene sand derived from the colorado river drainage basin do not fit neatly into the recycled orogen model proposed by w r dickinson and colleagues in contrast on the qmflt provenance discrimination diagram also engendered by w r dickinson and associates 16 samples plot in the mixed provenance field and nine specimens plot in the quartzose recycled or transitional continental fields on the lmlvls diagram formulated by r v ingersoll and c a suczek our samples plot close to the lv ls join approximately midway between the fields of magmatic arcs rifted continental margins and suture belts probably as a result of their mixed heritage thus the qmfl sub t and lmlvls diagrams produce results that reflect more accurately than do the results derived from the qfl provenance discrimination diagram the complex multiple tectonic characteristics of the source rocks in the colorado river drainage basin our samples therefore represent excellent examples of mixed provenance sands casual use of only the qfl diagram can lead to erroneous interpretations of provenances composed of more than one major tectonic element

crystallization conditions and evolution of magmatic fluids in the harney peak granite and associated pegmatites black hills south dakota evidence from fluid inclusions abstract a microthermometric study of inclusions in granites and pegmatites in the proterozoic harney peak granite system identified four types of inclusions type 1 inclusions are mixtures of co2 and h2o and have low salinities on average 3 5 wt nacleq type 2 inclusions are aqueous solutions of variable salinities from 0 to 40 wt nacleq type 3 inclusions are carbonic dominated by co2 with no detectable water and type 4 inclusions consist of 20 to 100 solids with the remaining volume occupied by a co2 h2o fluid many inclusions have a secondary character however a primary character can be unambiguously established in several occurrences of the type 1 inclusions these inclusions were trapped above the solidus and represent the exsolved magmatic fluid the secondary populations of types 1 2 and 3 probably formed as a result of reequilibration and unmixing of the type 1 fluid that progressively changed composition and density with decreasing temperature and pressure and was finally trapped along healed microfractures under subsolidus conditions type 4 inclusions are primary and are interpreted to be trapped fluid bearing complex silicate melts that subsequently solidified or underwent other posttrapping changes it is demonstrated that primary type 1 fluid inclusions that coexist with crystallized melt inclusions in the complex li bearing tin mountain pegmatite were trapped along the two fluid phase boundary in the system co2 h2o nacleq consequently the temperature and pressure conditions of trapping are identical to the bulk homogenization conditions on average 340 c and 2 7 kbar these conditions indicate that this li cs rb p and b rich pegmatite crystallized at some of the lowest known temperatures for a silicate melt in the crust an internally consistent empirical solvus surface in p t xco2 coordinates was generated for the pseudobinary co2 h2o 4 3 wt nacleq pegmatite fluid system distribution coefficients for the major species co2 h2o nacl and ch4 between the immiscible co2 rich and h2o rich fluid phases as a function of pressure and temperature were extracted from data for the two cogenetic fluid inclusions types

fluid immiscibility in natural processes use and misuse of fluid inclusion data ii interpretation of fluid inclusion data in terms of immiscibility abstract phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility in part i following from that point the major limits on the accuracy and even the validity of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed the practical implications of the general constraints temperature pressure topology of the fluid systems are envisaged emphasis is laid on some important consequences such as the use of isochore intercepts and the possible resulting interpretation of fluid mixing rather than unmixing the case of highly saline inclusions the identification and interpretation of heterogeneous trapping the composition and density constraints on coexisting fluids are presented and illustrated by natural examples taking into account all the measurable parameters in fluid inclusions volume temperature and nature of phase transitions more or less complete individual spectroscopic analyses all the available experimental data and all the theoretical constraints may be long and difficult however it is most generally very informative and productive although part of these data is often sufficient to deny unmixing nevertheless a final example on metamorphic fluids demonstrates how such an approach can prove and also characterize a fluid unmixing during a geologic process

structural and geochemical controls on the development of turbidite hosted gold quartz vein deposits wattle gully mine central victoria australia gold quartz vein deposits in the wattle gully mine arefault related structures developed in a low grade metamorphosed ordovician quartz rich flysch sequence the major mineralization is associated with a high angle reverse fault wattle gully fault that has a maximum displacement of 40 m over 10 6 metric tons t of vein quartz averaging 10 5 g t au occur within a dilatant jog in this structure fold geometry has controlled fault geometry and resulted in the localization of the jog segment where the wattle gully fault traverses an east dipping fold limb to link two more steeply dipping bedding parallel fault sediments on adjacent west dipping fold limbs gold mineralization is also associated with several minor east clipping reverse faults and a bedding parallel fault whose development is related to flexural slip during fold tightening mineralization occurs within fault fill veins and extension veins adjacent to faults the geometry and internal structures of veins indicate that vein growth has been controlled by repeated fluctuations in fluid pressure and shear stress associated with fault valve behavior vein mineralogy is dominated by quartz with minor carbonates chlorite white mica albite and apatite arsenopyrite and pyrite are the major sulfide phases but sphalerite galena chalcopyrite and pyrrhotite are also present the highest au grades tend to be localised in vein systems that are in proximity to carbonaceous slates wall rock alteration is minor and restricted mainly to narrow zones adjacent to major vein systems sulfur isotope fractionation between galena and sphalerite indicates mineralization occurred at temperatures around 300 degrees c the delta 34 s compositions of pyrite and arsenopyrite are nearly uniform throughout the mine 1 5 2 8 but are generally not in equilibrium with the delta 34 s values of associated base metal sulfides 0 7 5 3 the delta 18 o values for vein quartz vary between 15 6 and 18 0 per mil and correspond to delta 18 o values

infrared microthermometric and noble gas isotope study of fluid inclusions in ore minerals at the woxi orogenic au sb w deposit western hunan south china abstract the woxi au sb w deposit hosted by the neoproterozoic low grade metamorphic clastic rocks is located in a brittle ductile shear zone within the xuefengshan range south china orebodies are predominantly banded quartz veins which are strictly controlled by bedding faults and display significant vertical extents up to 2 km without obvious vertical metal zoning fluid inclusions hosted in quartz scheelite and stibnite from quartz scheelite and quartz sulfide gold veins have been studied using conventional and infrared microscopy respectively four types of fluid inclusions were identified based on petrography including type i two phase liquid rich aqueous inclusions type ii two or three phase co 2 rich inclusions type iii two phase vapour rich aqueous inclusions and type iv single phase aqueous inclusions the fluid inclusions in ore minerals scheelite and stibnite and their coexisting quartz largely share similar characteristics in terms of their types homogenization temperatures and salinities this is consistent with the fact that these ore minerals are always intergrown with quartz microthermometric and laser raman data indicate a low to moderate temperature 140 240 c low salinity 2 rich n 2 bearing aqueous ore forming fluid such fluid is further identified as a deeply non magmatic crustal fluid rather than a mantle source fluid by the significantly low 3 he 4 he ratios 0 002 0 281 ra and a small amount of meteoric water or host rock buffered fluid could be involved w ore precipitation was probably associated with mixing between a deeply originated crustal fluid and host rock buffered fluid based on the fluid inclusion features in scheelite and quartz i however au and sb ore deposition probably resulted from boiling which was caused by the marked pressure drop geological features such as banded structure and crack sealing structure also indicate that fluid pressure fluctuation induced by fault valve mechanism occurred during ore precipitation these characteristics of the ore forming fluids in the woxi deposit are in good agreement with the definition of orogenic gold deposits and the woxi au sb w deposit is probably an atypical orogenic gold deposit for its unique ore forming element association

spreading of near inertial energy in a 1 12 model of the north atlantic ocean near inertial energy in the ocean is thought to be redistributed by s dispersion whereby near inertial waves generated at the surface by wind forcing propagate downward and equatorward in this letter we examine the spreading of near inertial energy in a realistic 1 12 model of the north atlantic driven by synoptically varying wind forcing we find that 1 near inertial energy is strongly influenced by the mesoscale eddy field and appears to be locally drained to the deep ocean largely by the chimney effect associated with anticyclonic eddies and 2 the interior of the subtropical gyre shows very low levels of near inertial energy contrary to expectations based on the s dispersion effect

multiple hydrothermal processes in footwall units of the north range sudbury igneous complex canada and implications for the genesis of vein type cu ni pge deposits systematic regional sampling along the contact zone of the 1 85 ga age sudbury igneous complex with the archean levack gneiss footwall in the north range of the sudbury structure revealed textural mineralogical and fluid inclusion systematics of post sudbury igneous complex hydrothermal processes that affected the various lithologies at late stages of emplacement of the sudbury igneous complex and formation of magmatic fe ni cu sulfide deposits a partial melt from the levack gneiss invaded the contact zone this partial melt is revealed by small microdikes and irregular bodies of granophyric quartz plagioclase with megacrysts of hornblende clinopyroxene and titanite plagioclase hornblende equilibrium was established at 750 to 800 c and 1 10 to 1 55 kbars pressure corresponding to about a 4 to 6 km depth under lithostatic conditions f cl wt percent ratios around 15 for accessory apatite and hornblende indicate that a cl rich fluid phase separated during the crystallization of the footwall granophyre this is expressed as miarolites the cl rich fluid 50 wt nacl equiv salinity was trapped as primary fluid inclusions in quartz at around 480 c minimum temperature and around 1 1 kbars minimum pressure during supercooling these inclusions are rich in ca fe mn and k as well as na chloride this fluid may have interacted with earlier primary magmatic sulfide causing remobilization and reprecipitation of cu ni platinum group elements pge in veins and disseminations in the footwall these veins are parallel to the sudbury igneous complex footwall contact and are characterized by chalcopyrite pentlandite millerite magnetite stilpnomelane ferropyrosmalite epidote and chlorite michenerite moncheite merenskyite froodite insizwaite sobolevskite gold and bi ni sulfides are associated with sulfides epidote quartz actinolite and chlorite are common in the alteration selvages of the veins compositions and assemblages of platinum group minerals pgm indicate their precipitation below 575 to 485 c primary highly saline fluid inclusions about 40 wt nacl equiv in quartz indicate crystallization at 400 to 480 c and around 1 6 kbars minimum t and p respectively late carbonate epidote actinolite chlorite veins and alteration overprinted the earlier assemblages at about 300 to 400 c with some bornite millerite native silver and other bi sulfides the second stage of hydrothermal activity is characterized by regional carbonic aqueous nacl co 2 ch 4 h 2 o type immiscible fluids that were trapped as secondary inclusions in quartz from various lithologies no mineralization is related to this stage along the north range boiling of these fluids took place during a pressure drop from lithostatic to hydrostatic conditions during uplift from about a 5 to 6 to a 3 to 4 km depth at 300 to 350 c high 20 26 wt nacl equiv and low salinity 6 12 wt nacl equiv fluids coexisted with different carbonic species contents the predominant north south and northwest southeast orientations of fluid inclusion planes reveal that mobilization of carbonic aqueous solutions may be related to the northwesterly oriented thrusting in the sudbury structure during the late stages 1 8 1 7 ga of the penokean orogeny and to predominantly north south faulting in the north range the third stage of fluid mobilization also took place mostly along northerly and northwesterly oriented fractures aqueous fluids were ca rich brines 20 40 wt salinity with temperatures between 150 and 250 c some of these fluids also circulated in fractures parallel to the sudbury igneous complex footwall contact ne sw thus they locally may have interacted with the earlier sulfide assemblages and are also responsible for formation of late veinlets with chalcopyrite epidote quartz chlorite assemblages mobilization of these fluids took place under litho and hydrostatic conditions at about a 4 to 6 km depth this hydrothermal activity is related to a regional tectonothermal event during emplacement of northwesterly oriented sudbury dikes 1 24 ga regional scale fluid inclusion studies along the north range highlight the role of multiple hydrothermal processes in the metallogenic evolution of the sudbury igneous complex and especially in the distribution of copper and precious metals in the footwall units

fluid inclusion and stable isotope constraints on ore genesis of the zajkan epithermal base metal deposit tarom hashtjin metallogenic belt nw iran in the zajkan pb zn cu au ag deposit of the tarom hashtjin metallogenic belt thmb northwest iran mineralization occurs as quartz base metal sulfide veins hosted by eocene volcanic and volcaniclastic rocks of the karaj formation four stages of ore formation are identified at zajkan 1 quartz chalcopyrite pyrite veins 2 quartz galena sphalerite chalcopyrite pyrite veins and breccias 3 quartz hematite veins and breccias and 4 barren quartz carbonate veinlets the primary metallic minerals are pyrite chalcopyrite sphalerite galena and trace amounts of hematite gangue minerals are mainly quartz sericite chlorite and calcite the main wall rock alteration is silicification and intermediate argillic and propylitic alteration the coexistence of different types of fluid inclusions lv vl and v in individual fluid inclusion assemblages in quartz and sphalerite suggests boiling and heterogeneous trapping excluding the heterogeneously entrapped fluid inclusions the microthermometric measurements of primary lv fluid inclusion assemblages in quartz and sphalerite indicate that the veins were formed at temperatures between 217 and 273 degrees c from fluids with salinities between 1 7 and 6 4 wt nacl equiv the oxygen isotopic compositions delta o 18 water vsmow of 3 7 to 1 1 parts per thousand indicate that the ore forming fluids were mainly derived from magmatic water with the input of meteoric water in the later ore stages sulfur isotopic values of sulfide minerals vary over a narrow range from 5 0 to 0 9 parts per thousand vcdt averaging 2 2 parts per thousand vcdt suggesting that sulfur was derived from a homogeneous magmatic source the fluid inclusion and stable isotope data indicate that fluid boiling and mixing facilitated hydrothermal alteration and mineralization at zajkan our data suggest that the zajkan deposit is an intermediate sulficiation style epithermal mineralization the estimated ore formation depth of zajkan indicates minor denudation in the region and may imply a great prospecting potential for other epithermal mineralization in the thmb

composition of modern stream sand derived from a mixture of sedimentary and metamorphic source rocks henares river central spain the henares river central spain flows westward from the iberian range mesozoic sedimentary rocks under semiarid climatic conditions in the middle and lower reaches the henares river receives sediment from three tributaries canamares bornova and sorbe rivers that drain the central system paleozoic crystalline rocks low grade metamorphic rocks and minor amounts of mesozoic sedimentary rocks modern sands from the henares river and its tributaries offer an excellent opportunity to evaluate the importance of lithology and physiography in determining detrital modes from mixed metamorphic and sedimentary source terrain sand modes from the henares river and its tributaries are quartzolithic they plot in a restricted area on a qmflt diagram with low contents of feldspar and variable amounts of quartz and carbonate metamorphic and minor siliciclastic lithic fragments higher feldspar abundances in the canamares and bornova stream sands are related to the erosion of gneissic rocks by contrast sands from sorbe river are low in feldspar reflecting the absence of coarse metamorphic sources thus proportions of bedrock lithologies in the drainage sub basins are the main control on detrital modes of the tributaries in addition slope acts on the sand productivity of source rocks sedimentary source rocks in the upper reaches of the three tributaries have a poor productivity in the carbonate lithic fragments lsc compared with the lsc productivity of sedimentary sources located downstream with higher relief the percentage of bedrock types in the source area versus petrographic indices lm l lss l and lsc l provide a useful contrast between source and sand composition in the tributaries thus the high content of metamorphic lithic grains in the lithic grain population over represents this lithology slate plus schist at the source terrain lithic grains from sedimentary clastic sources generate few recognizable grains lss in the lithic grain population local supplies from carbonate sources may produce important increases of lsc in short reaches of the channels sand compositions in the henares river seem to be very homogeneous in a qmflt diagram with only minor differences caused by the supplies from the tributaries these differences can be modeled in terms of end member mixing processes between henares detritus and detritus from the relevant tributary these mixing processes are more evident when lithic grain contents lmlvls and lmlsslsc diagrams are compared changes produced by inputs from the canamares bornova and sorbe rivers are not permanent along the henares course an important homogenization of henares sand composition takes place by the mixing of tributary deposits with previously deposited henares river terraces abrasion during transport does not appear to cause significant changes in the sand composition along the henares river

fluid inclusion microthermometry and the p t evolution of gold bearing hydrothermal fluids in the niuxinshan gold deposit eastern hebei province ne china niuxinshan is a typical example of the numerous mesothermal gold deposits formed during mesozoic tectono magmatic reactivation of the archean north china craton in eastern hebei province gold occurs in quartz sulfide lodes in archean amphibolites and also in greisen zones in the mesozoic niuxinshan granite stock four mineralization stages can be recognized from early to late 1 quartz k feldspar 2 quartz pyrite 3 quartz polysulfide and 4 quartz carbonate gold mineralization mainly occurs in stages 2 and 3 fluid inclusions in quartz and fluorite from greisen zones in the niuxinshan granite and inclusions in vein quartz and sphalerite from stages 1 to 3 in the amphibolites have been studied by microthermometry three compositional types of inclusions are recognized type 1 tp1 are h2o co2 bearing inclusions and include primary tp1 p and secondary tp1 s inclusions these are found in quartz and fluorite from the greisen zones as well as in vein quartz and sphalerite from stages 1 to 3 the tp1 p inclusions are considered to represent the gold bearing hydrothermal fluids type 2 tp2 s are secondary h2o co2 solid phase inclusions in fluorite from the greisen zones type 3 tp3 s are secondary aqueous inclusions with a solid phase which coexist with the tp2 s in fluorite from the greisen zones the tp1 p inclusions show variable vco2 commonly 0 3 to 0 6 and xco2 values mainly 0 1 to 0 4 the salinities of inclusions cluster around 3 to 11 wt nacl equivalent and their homogenization temperatures to the liquid phase th l fall dominantly in the range of 260 to 360 c the compositional variations of inclusions in stage 1 probably result from exsolution of magmatic fluids at various stages immiscibility or boiling of the fluids can be ruled out the compositional variations of inclusions in the greisen zones and in vein stages 2 and 3 are attributed to cooling mixing dilution and necking down of the fluids the tp1 s and tp2 s inclusions show salinities of 3 to 6 wt nacl equivalent and xco2 values of 0 04 to 0 17 th l clusters at 240 to 260 c the tp3 s inclusions have salinities of 3 to 6 wt nacl equivalent and th l of 170 to 240 c isochoric reconstructions combined with oxygen and sulfur isotope geothermometry of mineral pairs give trapping p t conditions for the gold bearing fluids the greisen zones formed at 310 to 460 c and 1 3 to 3 7 kbar stage 1 veins at 300 to 430 c and 1 2 to 3 7 kbar stage 2 veins at 290 to 380 c and 1 to 3 kbar stage 3 veins at 250 to 350 c and 1 to 3 kbar h2o co2 fluids with low to moderate salinities and moderate to high densities 0 66 to 1 01 g cm3 dominated at early mineralization stages and evolved towards h2o richer and co2 and less saline fluids through time the retrograde p t evolution probably resulted from regional uplift and cooling of gold bearing hydrothermal fluids the gold bisulfide complex was dominant in the fluids during mineralization and gold deposition was mainly induced by decreases of temperature and pressure as well as destabilization of the bisulfide complex during sulfidization of wall rocks

inertial wave dynamics in the north atlantic subtropical zone doppler current profiler observations of an inertial wave packet are presented from a region where a cold core ring impinges on a front in this intense current a drogue is deployed to mark one region of the fluid as the drogue is advected by the current the ship follows it zigzagging across the drogue s trajectory along this ship track vertical rotary velocity spectra indicate the presence of a downgoing intertial wave with a vertical wavelength which slowly changes from 50 to 100 m as time progresses the wave s intrinsic frequency was measured for the first time ever a horizontally synoptic data set is obtained at the drogue depth by correcting for frontal advection and the temporal rotation of the wave velocity examination of these synoptic data indicates the presence of a southgoing near inertial wave with horizontal wavelength 20 km the wave is confined to a 25 km region supplementary ray tracing calculations through objective maps of the ring flow field indicate that the wave is strongly influenced by doppler shifting this is accompanied by a slow counterclockwise turning of the horizontal wave number vector a decrease in the intrinsic frequency and an increase in the vertical wavelength in qualitative agreement with the data a companion paper marmorino et al this issue details the effect of this inertial wave upon the small scale temperature activity with horizontal length scales of 1 3 m

decratonic gold mineralization evidence from the shangzhuang gold deposit eastern north china craton abstract the jiaodong peninsula in the eastern north china craton ncc hosts some of the world class gold deposits among these the shangzhuang gold deposit represents a typical fault zone hosted disseminated and stockwork style gold mineralization the mineralization is characterized by intense hydrothermal alteration halos in the wallrocks with the mineralized veins intruding into altered wallrocks zircon u pb isotope dating constrains the timing of emplacement of the guojialing granodiorite as 130 1 ma five molybdenite samples from the main mineralization stage veins yielded a well fitted isochron age of 126 2 ma mswd 1 3 marking the timing of gold mineralization four types of fluid inclusions are identified at shangzhuang and their petrographic and microthermometric features suggest fluid immiscibility followed by fluid mixing this inference is also supported by oxygen and hydrogen isotopic data of quartz veins from stage iii the measured 18 o values of quartz are 12 3 to 13 7 for stage ii and 11 7 to 12 0 for stage iii with calculated 18 o fluid values for stage ii ranging from 5 9 to 7 3 and for stage iii from 3 4 to 3 7 d values for stage ii and iii quartz range from 65 3 to 75 2 and 70 6 to 74 7 respectively the data suggest that the ore forming fluids were initially derived from magmatic sources followed by mixing with meteoric water sims in situ sulfur isotope analyses of two types of pyrite py i and py ii from different mineralization stages show different sulfur isotope features the 34 s values for py i 10 2 to 11 3 mean 10 8 n 25 are higher than those of the later mostly gold related py ii 4 1 to 6 8 mean 5 4 n 27 the higher 34 s values of py i are correlated to degassing of mantle wedge metasomatized by the slab fluids the relatively lower 34 s values of py ii might suggest increasing of f o2 through fluid mixing between ore forming fluids and meteoric water the temporal spatial and tectonic relations between the giant gold mineralization and destruction of the ncc suggest a genetic linkage the gold mineralization between 126 and 117 ma at jiaodong was probably initiated at the peak of decratonization ca 125 ma of the eastern ncc phanerozoic craton margin orogeny also played a critical role in the generation of the early cretaceous giant gold deposits in the eastern ncc integrated geological characteristics mineralization features metallogenic age sources of ore forming fluids and sulfur and tectonic settings favor a decratonic gold mineralization model for the shangzhuang gold deposit the geodynamic scenario proposed for the early cretaceous giant gold mineralization event in the eastern ncc includes the paleo west pacific plate subduction asthenospheric upwelling multiple subduction collision processes along the margins

geology and fluid characteristics of the mina velha and mandiocal orebodies and implications for the genesis of the orogenic chega tudo gold deposit gurupi belt brazil the chega tudo gold deposit is located in the gurupi belt of northern brazil gold mineralization in the mina velha upper level and mandiocal intermediate and lower levels orebodies is hosted in highly strained paleoproterozoic 2148 2160 ma felsic to intermediate metavolcanic rocks and schists that record greenschist facies metamorphism the orebodies are broadly concordant with the regional northwest oriented foliation and mineralization comprises thick quartz vein sets and small quartz carbonate sulfide veinlets and enclosing hydrothermally altered host rocks the hydrothermal mineral assemblage is postpeak metamorphism syn to late tectonic and includes quartz calcite chlorite white mica pyrite subordinate chalcopyrite and traces of sphalerite and galena free milling gold occurs in sulfide poor veins in the upper and lower zones of the deposit whereas refractory gold was deposited in fractures of pyrite and quartz in the more gold enriched intermediate lower level fluid inclusion and stable isotope o h c and s data indicate that the two styles of gold deposition were produced by a combination of fluid immiscibility fluid rock reactions sulfidation carbonatization and probably mixing occurring in two discrete stages within a single mineralizing event associated with fluid flow within and around an active shear zone under fluctuating pressure conditions the refractory gold was deposited at 340 to 370 c from a co2 ch4 h2o nacl fluid having salinity of 5 8 2 7 wt percent nacl equiv variable co2 contents typically 12 22 mol and up to 6 mol percent ch4 the 18o and d values of this fluid are 7 9 to 9 4 per mil and 29 to 37 per mil respectively indicating a metamorphic origin carbon isotopes show contrasting values in fluid inclusion co2 13c 24 1 and calcite 13c of 3 8 the strongly negative value of fluid inclusion co2 is interpreted to be an organic signature acquired at the site of deposition by reaction of the deeply sourced ore forming fluid with carbonaceous schists present in the deepest part of the deposit the higher value for calcite probably records a crustal source oxygen fugacities calculated for the whole range of t p xco2 conditions yielded log fo 2 between 28 7 and 30 5 indicating reduced conditions for the fluid which is in agreement with the mineral paragenesis fluid inclusion compositions and sulfur isotope values the second fluid responsible for the deposition of the free milling gold in veins and probably part of the gold of the lower zone of the deposit had a lower temperature 330 340 c this co2 h2o nacl fluid had a salinity of 1 6 to 2 5 wt percent nacl equiv and contained 11 to 13 mol percent co2 the 18o and d values of this fluid are 5 3 to 7 2 per mil and 12 to 30 per mil respectively also indicating a metamorphic source the 13c value of fluid inclusion co2 is 6 9 per mil likely representing a mantle derived carbon source log fo 2 values between 30 5 and 31 5 also indicate slightly more reduced conditions for this fluid both fluids had near neutral ph between 5 and 6 2 and 34s values of h2s between 0 2 and 1 0 per mil interpreted to reflect derivation of sulfur from magmatic sulfides

determining phase volumes of mixed co 2 h 2 o inclusions using microthermometric measurements a new graphical technique has been developed which permits the composition and volumetric properties of mixed co2 h2o inclusions to be determined using microthermometric measurements if the values of only two of the four variables 1 density of the co2 phase derived from the temperature and mode of partial homogenization 2 temperature and mode of total homogenization 3 volume fraction of the co2 phase at 40 c and 4 molar fraction of co2 of a mixed co2 h2o inclusion are known the values of the other two variables can be taken from a diagram depicting the relationships between all four variables the diagram can be used to derive the volume fraction of the co2 phase from measurements of the partial and total homogenization temperature it can also be employed in the opposite sense for determining the theoretical homogenization temperature of an inclusion which decrepitates before reaching total homogenization provided a good visual phase volume estimate is available the graphical technique can also be applied to mixed co2 h2o inclusions which contain 6 wt nacl

shallow water stratigraphy at the mount chalmers volcanic hosted massive sulfide deposit queensland australia mapping of the permian stratigraphy at the mount chalmers massive sulfide footwall stockwork cu au orebody has revealed shallow water body fossils trace fossils and nonwelded to partly welded pyroclastic units within the fiat lying host sequence the massive sulfide bearing lower chalmers sediment and the upper chalmers sediment are each 20 to 40 m thick and comprise fossiliferous tuffaceous mudstone and wacke they are separated by the north star pumice breccia the breccia is 50 m thick at the mine and comprises watertransformed pyroclastic fiow deposits but 2 km to the south and southwest it is 120 m thick and includes probable nonwelded ignimbrite the upper chalmers sediment is overlain by a dacitic tuff which has a 5 m thick blocky to columnar jointed interval near the base termed the chalmers welded tuff the tuff contains strongly spherulitic pumice lenses within a weakly spherulitic matrix with relict fine banding it extends at least 450 m north and 300 m west from the mine the upper chalmers sediment has yielded an assemblage of brachiopods gastropods bivalves and bryozoans from five localities 1 to 2 km north and south of the mine these body fossils show limited reworking and are typical of a shallow marine shelf setting near or below wave base although seawater depths of 50 to 300 m are possible a range of 100 to 200 m depth is considered most likely the upper and lower chalmers sediments contain trace fossils typical of the cruziana ichnofacies below and above the ore position also suggesting shelf sedimentation below the effective wave base these consistent estimates suggest that seawater depths of 200 to 300 m prevailed during deposition of the massive sulfide contrary to the 1 000 m seawater depth usually regarded as necessary to form vhms ore deposits the shallow depth would have allowed the ascending ore forming fluids to boil prior to reaching the sea floor unless prevented by channel constrictions boiling may account for the strong cu rich footwall stringer zone and elevated fluid inclusion salinities at mount chalmers large and both 1980 the duplication of these features at other deposits suggests that mount chalmers is not an isolated case the relatively shallow water depths have also

geochemistry and u pb hf zircon data for plutonic rocks of the troia massif borborema province ne brazil evidence for reworking of archean and juvenile paleoproterozoic crust during rhyacian accretionary and collisional tectonics abstract rhyacian c 2 30 2 05 ga subduction accretion and collisional processes are thought to represent an important event of crustal growth and reworking often reported in the so called tranzamazonian eburnean granite greenstone terranes of n ne brazil and west african craton in this work we present whole rock geochemistry and u pb hf zircon ages for rhyacian plutonic rocks that intrude paleoproterozoic granite greenstone terranes and archean basement rocks of the troia massif borborema province ne brazil u pb shrimp zircon age of 2185 4 ma was obtained for a metatonalite sample mirador metatonalites the metatonalites show geochemical affinity similar to those of adakites like rocks with all classic slab derived adakitic signature e g high sr y la yb and low hree but more akin to those evolved from partial melting of the metasomatized mantle wedge followed by fractional crystallization zircon hf crustal model ages of the metatonalite sample range between 2800 and 2660 ma evidencing that archean crustal components contributed to its magma genesis probably via subduction of continental derived sediments to the mantle wedge for potassic plutons of the troia massif bananeira suite we obtained u pb shrimp zircon age of 2079 4 ma for a deformed quartz monzonite with geochemical affinities similar to those derived from low pressure partial melting of a k rich mafic protolith for less deformed equigranular granites we obtained a u pb la icpms zircon age of 2068 5 ma they are high k calc alkaline and slightly peraluminous granites that probably derived from low pressure partial melting of tonalitic crustal sources metatonalites and or metagraywackes zircon hf crustal model ages of a granite sample range from 2713 to 2535 ma evidencing archean crustal contribution to magma genesis however two analyzed c 2307 ma inherited zircon grains show ehf t values of c 4 87 indicating that crustal reworking of less radiogenic paleoproterozoic sources also participated in its genesis regional correlations of our results with the paleoproterozoic record of the troia massif borborema province and surrounding cratonic domains suggest that the studied plutons are related to the c 2 2 2 0 ga transamazonian eburnean orogenic cycle the c 2185 ma metatonalites are associated to pre collisional setting while the c 2079 2068 ma quartz monzonites and granites evolved during collisional setting

paleoproterozoic turbidite hosted gold deposits of the ashanti gold belt ghana west africa comparative analysis of turbidite hosted gold deposits and an updated genetic model abstract the paleoproterozoic gold deposits of the ashanti gold belt ghana occur mainly as auriferous quartz veins in graphitic shears proximal to contacts between deformed and metamorphosed turbidites and tholeiitic volcanics alternately block faulted tarkwaian sediments they are suggested in this article to belong to that class of gold deposits recognized as turbidite hosted hence evidence from previous investigations of turbidite hosted and turbidite associated gold deposits occurring in circumstances roughly similar to the ashanti deposits are used where relevant to produce an updated genetic model for the latter given the relatively significant amounts of graphite associated with the major ashanti deposits the role of non carbonate carbon is assessed in the light of conclusions reached by work on other turbidite hosted and turbidite associated gold belts conclusions as to the origins of mineralizing fluids and temporary repositories of gold auriferous interflow sediments reached by work on these other belts are also analysed a concept of the tectonic development of the ashanti belt kumasi basin area introduced in this article is deemed to be critical to the origin of the ashanti gold deposits it encompasses the role of non carbonate carbon turbidites and the primary sources and secondary repositories of au and as in the genesis of the major ashanti gold deposits it examines the significance of the intimate relationship between calc alkaline volcanism and the basin sediments the occurrences of felsic metasandstones in transition zone sediments and ttg granitic material and fragments of chemical sediments in turbidites all of which are incompatible with one or the other of existing concepts of tectonic development in the area

turbulent mixing induced by upgoing near inertial waves in the seasonal thermocline of the norwegian sea acoustic doppler current profiler and towed thermistor chain measurements made in the seasonal thermocline in the norwegian sea are examined for evidence that near inertial shear leads to small scale turbulent mixing as inferred from meter scale temperature fluctuations for the 1 day of data examined here spatial variability in shear is dominated by near inertial waves having upward energy propagation 30 m vertical wavelength and 5 to 10 km horizontal extent 20 km wavelength repeated samples of one of these waves had high froude number and enhanced small scale variability dominated by 20 m long waveforms which we conjecture are kelvin helmholtz instabilities arising from the near inertial shear

the gounkoto au deposit west africa constraints on ore genesis and volatile sources from petrological fluid inclusion and stable isotope data the loulo gounkoto complex in the kedougou kenieba inlier hosts three multi million ounce orogenic gold deposits situated along the senegal mali shear zone this west malian gold belt represents the largest west african orogenic gold district outside ghana the gounkoto deposit is hosted to the south of the gara and yalea gold mines in the kofi series metasedimentary rocks the ore body is structurally controlled and is characterised by sodic and phyllic alteration as and fe rich ore assemblages with abundant magnetite and overall enrichment in fe as cu au ag w ni co ree minor te pb se cd fluid inclusion analysis indicates that the deposit formed at p t conditions of approximately 1 4 kbar and 340 c and that two end member fluids were involved in mineralisation 1 a moderate temperature 315 340 c low salinity 10 wt nacl equiv low density 1 g cm 3 h2o co2 nacl h2s n2 ch4 fluid 2 a high temperature up to 445 c hypersaline 40 wt nacl equiv high density 1 3 g cm 3 h2o co2 nacl fecl2 fluid partial mixing of these fluids within the jog zone at gounkoto enhanced phase separation in the aqueo carbonic fluid and acted as a precipitation mechanism for au these findings demonstrate the widespread if heterogeneously distributed nature of fluid mixing as an ore forming process in the loulo gounkoto complex operating over at least a 30 km strike length of the shear zone stable isotope analyses of ore components at gounkoto indicate a dominant metamorphic source for h2o h2s and co2 and by extension au it thus can be reasoned that both the aqueo carbonic and the hypersaline fluid at gounkoto are of metamorphic origin and that the high levels of salinity in the brine are likely derived from evaporite dissolution

observations of near inertial waves in acoustic doppler current profiler measurements made during the mixed layer dynamics experiment measurements of upper ocean shear made during the mixed layer dynamics experiment mildex provide evidence of large horizontal scale motion at near inertial frequency the measurements consist of shipboard acoustic doppler current profiles four large scale spatial surveys of 2 4 days duration were made by the r v wecoma as a set of boxes approximately 60 km per side around a drifting current meter buoy velocity time series from the drifting buoy and from sonar measurements made from flip also indicated the presence of motions at near inertial frequency horizontal length and time scales of the motion are estimated from the phase of the shear vector measured during the spatial surveys estimates of the length scale of the waves range from 500 to 1000 km and the frequency is approximately 1 1f the behavior of the phase is found to be consistent with a model of narrow band inertial waves with vertical structure such that there is a zero crossing in velocity at the base of the mixed layer 40 60 m

near surface frontal zone trapping and deep upward propagation of internal wave energy in the japan east sea the full depth current structure in the japan east sea was investigated using direct velocity measurements performed with lowered and shipboard acoustic current doppler profilers rotary spectral analysis was used to investigate the three dimensional energy distribution as well as wave polarization with respect to vertical wavenumbers yielding information about the net energy propagation direction highly energetic near inertial downward propagating waves were found in localized patches along the southern edge of the subpolar front between 500 and 2500 m depth the basin average energy propagation was found to be upward with the maximum of relative difference between upward and downward propagating energy lying at about 1500 m depth this difference was most pronounced in the southeastern part of the basin

near inertial wave wake of hurricanes katrina and rita over mesoscale oceanic eddies abstract tropical cyclones tcs katrina and rita moved as major hurricanes over energetic geostrophic ocean features in the gulf of mexico increased and reduced oceanic mixed layer oml cooling was measured following the passage of both storms over cyclonic and anticyclonic geostrophic relative vorticity g respectively this contrasting thermal response is investigated here in terms of the evolution of the storms near inertial wave wake in geostrophic eddies observational data and ray tracing techniques in realistic geostrophic flow indicate that tc forced oml near inertial waves are trapped in regions of negative g where they rapidly propagate into the thermocline these anticyclonic rotating regimes coincided with the distribution of reduced oml cooling because rapid downward dispersion of near inertial energy reduced the amount of kinetic energy available to increase vertical shears at the oml base by contrast tc forced oml near inertial waves were stalled in upper layers of cyclonic circula

fluid immiscibility in natural processes use and misuse of fluid inclusion data abstract many occurrences of fluid immiscibility in natural geologic systems have been reported recently most often from fluid inclusion studies however the interpretation of fluid inclusion data in terms of immiscibility sometimes suffers from ambiguity of the vocabulary insufficient knowledge of the immiscibility constraints and insufficient knowledge of the topology in the tpx space of natural fluid systems for such reasons some authors have been misled to erroneous interpretations the term chemical immiscibility is unambiguously redefined as a multiphase multicomponent equilibrium the consequences of this definition are directly derived from the phase rule and concern the possible equations that relate the various parameters temperature pressure volumes compositions to each other these equations already put constraints on the topology of the phase equilibria in fluid systems a particular expression of the phase rule is proposed which takes into account the multiphase constant bulk volume constant bulk composition constraints in fluid inclusions the consequences of such an expression are of major importance in fluid inclusion studies the phase relations of some simple systems that approximate quite efficiently the natural complex fluids are then detailed h2o nacl co2 ch4 h2o co2 h2o co2 nacl the effects of these topologies and of the supplementary constraints constant bulk composition and constant bulk volume assumed for fluid inclusions isopleth isochoric systems are discussed

metallogenesis of the paleoproterozoic piaba orogenic gold deposit sao luis cratonic fragment brazil piaba is an orogenic gold deposit 3 5 moz of the sao luis cratonic fragment in north northeastern brazil the deposit is epizonal mesozonal and associated with the development of a subvertical strike slip fault that cut across rhyacian metavolcano sedimentary rocks and granitoids the metavolcano sedimentary sequence comprises carbon bearing schists andesite dacite ultramafic rocks and felsic tuffs formed at 2240 5 ma to 2227 33 ma that were intruded at 2214 3 ma by fine grained subvolcanic granophyric granodiorite whole rock geochemistry indicates that the hosting metavolcano sedimentary sequence formed in a subduction related arc back arc setting which has previously been interpreted as the early arc stage of an accretionary orogen 2240 2214 ma that was followed by voluminous subduction related calc alkaline arc magmatism 2168 2145 ma and by a collisional phase 2100 15 ma that produced several bodies of peraluminous granites the hydrothermal alteration of the host rocks produced early distal carbonization and hematitization and proximal ore related chlorite sericite carbonate sulfide alteration two styles of mineralization occurring in association are present 1 a network of thin quartz sulfide veinlets and subordinate narrow breccia veins with refractory to free milling gold dissemination in hydrothermally altered host rocks and 2 subordinate low sulfide au quartz veins with free milling gold fluid inclusions and stable isotopes characterize the mineralizing solution as a relatively reduced log fo2 30 to 35 neutral to slightly alkaline ph 5 to 6 2 low salinity average 5 nacl aqueous carbonic xco2 5 to 59 mol xh2o 40 to 93 mol xn2 and xch4 1 mol metamorphic fluid 18oh2o 5 5 to 8 9 dh2o 8 to 69 and suggest that gold mineralization occurred at 250 to 330 c and 1 25 to 2 8 kbar in response to phase separation and fluid rock interactions that produced sulfidation and minor carbonatization sulfur 34s 2 7 to 3 8 is from an undetermined source probably magmatic oxidized or sedimentary lead isotope compositions of gold ore related pyrite and k feldspar from regional rocks suggest that collision related granitoids of ca 2100 15 ma are the most likely sources for pb in the ore although mantle and lower crustal sources are also observed 40ar 39ar in hydrothermal sericite yielded a plateau age of 1980 13 ma which is similar to the pb pb model age of gold of 1959 ma these are considered the minimum age for gold mineralization whereas the maximum age of 2009 11 ma is given by a small gold hosting intrusion in the same region

a comparison of jiaojia and linglong type gold deposit ore forming fluids do they differ abstract the jiaodong peninsula contains the most important concentration of gold deposits in china which can be divided into jiaojia type and linglong type deposits based on mineralization style the former is characterized by disseminated and stockwork style mineralization hosted in first order regional faults with relatively larger tonnages and lower gold grades the latter is characterized by massive auriferous quartz veins commonly hosted in subsidiary second or third order faults with smaller tonnage but higher grade orebodies despite these differences both groups of deposits have the same alteration assemblages mineral paragenesis element concentrations and ore forming ages the mainly jiaojia type luoshan gold deposit and the mainly linglong type fushan gold deposit are characterized by h o s pb isotope data that indicate the ore forming fluids have a dominantly metamorphic source the fluids were derived during the yanshanian orogenic event and were most likely associated with dehydration and decarbonization processes near the top of the subducting paleo pacific plate the linglong type ores have relatively lighter calculated 18 o compositions 3 9 to 2 3 than the jiaojia type ores 0 3 8 0 possibly because of a greater degree of mixing with meteoric water petrographic cathodoluminescence microthermometric and laser raman spectroscopic analyses of fluid inclusion assemblages in quartz from the two types of ores indicate fluids were similar in both cases characterized by medium high homogenization temperatures 211 393 c significant co 2 15 mol minor ch 4 18 in the carbonic phase and low salinity 11 2 wt nacl eq the linglong type ores however have a wider range of co 2 and ch 4 concentration and salinity than the jiaojia type ores fluid immiscibility occurred in main ore stage of both ore types with the trapping conditions of 77 185 mpa and 284 328 c although the unmixing is more intense and widespread in the linglong type ores both fluid wallrock interaction and fluid immiscibility are important gold deposition processes in the two types but immiscibility is more important in the linglong type ores and that has led to the typical higher gold grade in general there is little geochemical differences between the ore forming fluids for jiaojia and linglong type gold deposits both jiaojia and linglong type ores can exist in a single deposit and form in the same metallogenic event the linglong type ores developed as more massive veins because of their location in zones of more extensive extension and they lack significant post ore cataclastic deformation

geochronology fluid inclusions and isotopic characteristics of the chaganbulagen pb zn ag deposit inner mongolia china abstract the large chaganbulagen pb zn ag deposit is located in the derbugan metallogenic belt of the northern great xing an range the vein style orebodies of the deposit occur in the nww trending fault zones the ore forming process at the deposit can be divided into three stages an early quartz pyrite arsenopyrite pyrrhotite sphalerite galena chalcopyrite stage a middle quartz carbonate pyrite sphalerite galena silver bearing minerals stage and a late quartz carbonate pyrite stage the sericite sample yielded a 40 ar 39 ar plateau age of 138 1 ma and an isochron age of 137 3 ma and the zircon la icp ms u pb age of monzogranite porphyry was 143 2 ma indicating that the ages of mineralization and monzogranite porphyry in the chaganbulagen deposit should be the early cretaceous and that the mineralization should be slightly later than the intrusion of monzogranite porphyry there are only liquid inclusions in quartz veins of the chaganbulagen deposit homogenization temperatures densities and salinities of the fluid inclusions from the early stage are 261 340 c 0 65 0 81 g cm 3 and 0 7 6 3 wt nacl eqv respectively fluid inclusions of the middle stage have homogenization temperatures densities and salinities of 209 265 c 0 75 0 86 g cm 3 and 0 5 5 7 wt nacl eqv respectively for fluid inclusions of the late stage their homogenization temperatures densities and salinities are 173 219 c 0 85 0 91 g cm 3 and 0 4 2 7 wt nacl eqv respectively the ore forming fluids of the deposit are generally characterized by moderate temperature and low salinity and density and belong to an h 2 o nacl co 2 ch 4 system the 18 o water values calculated for ore bearing quartz vary from 17 9 to 10 8 and the d v smow values from bulk extraction of fluid inclusion waters vary from 166 to 127 suggesting that the ore forming fluids consist dominantly of meteoric water the 34 s v cdt values range from 1 4 to 4 1 the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of the ore minerals are in the ranges of 18 302 19 037 15 473 15 593 and 38 110 38 945 respectively the data for the s and pb isotopic systems indicate that the ore forming metals and sulfur came from mesozoic magma the chaganbulagen deposit is a low sulfidation epithermal pb zn ag deposit and the temperature decrease is the dominant mechanism for the deposition of ore forming materials

the inertial chimney the near inertial energy drainage from the ocean surface to the deep layer a three dimensional primitive equation numerical model is used to study the behavior of near inertial waves generated by surface wind stress on an plane the model is fixed depth with a rigid lid on the surface and is horizontally periodic this study shows the behaviors of the wind generated near inertial waves for four different eddies 1 a subtropical cold core eddy 2 a subtropical warm core eddy 3 a california subsurface warm core eddy and 4 the gulf stream warm core ring the mean secondary circulation generated by the wind eddy interaction has magnitude to comparable to that of the ekman current and its characteristics are determined by the relative angle between wind and current the propagation characteristics of near inertial waves are quite different depending upon the sign of the relative vorticity in a cyclonic eddy near inertial wave propagation is outward from the core of the eddy the propagation direction in an anticyclonic eddy is downward and toward the core vertically propagating waves inside the eddy are trapped above a critical layer and slowly dissipated by parameterized viscous effects the model shows that anticyclones efficiently drain near inertial energy from the surface to the deep layer below the thermocline

evolution of brines and co2 rich fluids and hydrothermal overprinting in the genesis of the borrachudo copper deposit carajas province abstract the carajas province is one of the world s major domains of iron oxide copper gold iocg deposits which formed during the neoarchean ca 2 70 2 68 ga and ca 2 57 ga the province also hosts other copper gold deposits of paleoproterozoic age ca 1 88 ga the borrachudo copper deposit is located about 6 km southwest of the world class cristalino iocg deposit porphyritic rhyolite and amygdaloidal andesite of the ca 2 76 2 74 ga grao para group formed in a volcano plutonic event during the neoarchean are the main host to the borrachudo deposit copper mineralization was related to two distinct hydrothermal events the first controlled by the development of ductile structures was likely linked to the carajas ca 2 70 ga iocg system it evolved from sodic alteration silicification and iron metasomatism through to calcic and potassic alteration chalcopyrite strings along foliation breccias and massive ore represent early copper mineralization during the early hydrothermal event aqueous 165 to 400 c 0 23 to 38 32 wt nacl equiv aqueous carbonic and carbonic fluid inclusions tmco2 60 1 to 59 4 c co2 density of 0 82 to 0 97 g cm3 were trapped in quartz formed during the silicification immiscibility of a magmatic fluid or heterogeneous trapping of brines and co2 bearing fluids followed by mixing with diluted colder fluids are suggested the late event controlled by brittle structures records recurrence of hydrothermal alteration stages such as silicification sodic alteration and potassic alteration as well as chlorite and carbonate alteration the copper mineralization is represented by chalcopyrite in branched breccia pipes and veins with minor magnetite pyrite siegenite cobaltite galena anglesite uraninite and thorite titanite in veins of albite chalcopyrite apatite yielded an la icp ms u pb titanite age of 2011 6 8 ma during the late hydrothermal event aqueous fluids 140 to 320 c 6 7 to 40 wt nacl equiv reflected a more advanced mixing process involving diluted external fluids the borrachudo deposit points to the recurrence of multiple hydrothermal events responsible for the copper metallogenesis which were intrinsically controlled by the magmatic and tectonic evolution of the carajas province

fluid inclusion and stable isotope o h c and s constraints on the genesis of the serrinha gold deposit gurupi belt northern brazil the serrinha gold deposit of the gurupi belt northern brazil belongs to the class of orogenic gold deposits the deposit is hosted in highly strained graphitic schist belonging to a paleoproterozoic 2 160 ma metavolcano sedimentary sequence the ore zones are up to 11 m thick parallel to the regional nw se schistosity and characterized by quartz carbonate sulfide veinlets and minor disseminations textural and structural data indicate that mineralization was syn to late tectonic and post metamorphic fluid inclusion studies identified early co2 ch4 n2 and co2 ch4 n2 h2o nacl inclusions that show highly variable phase ratios co2 homogenization and total homogenization temperatures both to liquid and vapor interpreted as the product of fluid immiscibility under fluctuating pressure conditions more or less asso ciated with postentrapment modifications the ore bearing fluid typically has 18 33mol of co2 up to 4mol of n2 and less than 2mol of ch4 and displays moderate to high densities with salinity around 4 5wt nacl equiv mineralization occurred around 310 to 335 c and 1 3 to 3 0 kbar based on fluid inclusion homogenization temperatures and oxygen isotope thermometry with estimated oxygen fugacity indicating relatively reduced conditions stable isotope data on quartz carbonate and fluid inclusions suggest that veins formed from fluids with 18 oh2o and dh2o 310 335 c values of 6 2 to 8 4

a comparative fluid inclusion study of the waterville and sangerville vassalboro formations south central maine petrologic and oxygen isotope data indicate that water rich fluids infiltrated metasedimentary rocks of the waterville and sangerville formally vassalboro formations south central maine during peak metamorphism and depleted sangerville rocks in alkalis but not equivalent waterville rocks fluid inclusion data from two outcrops 1 km apart one of the waterville and the other of the sangerville formations suggest a cause for the geochemical difference between the two units postulated peak metamorphic inclusions the texturally earliest of aqueous inclusions in the metasediments approximate the water rich compositions of peak fluids predicted by mineral fluid equilibria and have average salinity in the sangerville formation three times that of equivalent waterville inclusions the higher salinity in the sangerville fluids could explain the greater alkali depletion in these rocks probable pre peak or prograde inclusions are preserved in metasediments as the texturally earliest carbonic inclusions which contain co2 ch4 n2 h2o as determined by microthermometry and raman spectrometry they may have formed by breakdown of organic matter probable retrograde inclusions occur as texturally late aqucous inclusions in healed fractures with salinity ranges indistinguishable between the two formations synmetamorphic granitic dikes present in the two outcrops were ruled out as a source for fluids in metasediments because composition and density ranges of inclusions in dikes and metasediments are fundamentally different and because there is no correlation between the abundance or composition of inclusions in a sample and proximity to dikes isochores for many of the inclusions in both metasediments and dikes are not consistent with the inferred p t conditions of their trapping but intersect at 300 to 400 c and 1 to 2 kbar the intersections probably resulted because inclusion densities continued to equilibrate during uplift and cooling until quartz became rigid the present densities are those at the last equilibration not the time of trapping in contrast the clear distinctions in inclusion compositions between dikes and between dike and country rock show that the original compositional differences generally have been preserved

geology and fluid characteristics of the ulu sokor gold deposit kelantan malaysia implications for ore genesis and classification of the deposit abstract the ulu sokor gold deposit is one of the most famous and largest gold deposits in malaysia and is located in the central gold belt this deposit consists of three major orebodies that are related to ns and ne striking fractures within fault zones in permian triassic meta sedimentary and volcanic rocks of the east malaya block the faulting events represent different episodes that are related to each orebody and are correlated well with the mineralogy and paragenesis the gold mineralization consists of quartz dominant vein systems with sulfides and carbonates the hydrothermal alteration and mineralization occurred during three stages that were characterized by i silicification and brecciation ii carbonatization sericitization and chloritization and iii quartz carbonate veins fluid inclusions in the hydrothermal quartz and calcite of the three stages were studied the primary co 2 ch 4 h 2 o nacl fluid inclusions in stage i are mostly related to gold mineralization and display homogenization temperatures of 269 389 c salinities of 2 77 11 89 wt nacl equivalent variable co 2 contents typically 5 29 mol and up to 15 mol ch 4 in stage ii gold was deposited at 235 398 c from a co 2 ch 4 h 2 o nacl fluid with a salinity of 0 83 9 28 wt nacl equivalent variable co 2 contents typically 5 63 mol and up to 4 mol ch 4 the 18 o h 2 o and d values of the ore forming fluids from the stage ii quartz veins are 4 5 to 4 8 and 44 to 42 respectively and indicate a metamorphic hydrothermal origin oxygen fugacities calculated for the entire range of t p x co 2 conditions yielded log f o 2 values between 28 95 and 36 73 for stage i and between 28 32 and 39 18 for stage ii these values indicate reduced conditions for these fluids which are consistent with the mineral paragenesis fluid inclusion compositions and isotope values the presence of daughter mineral bearing aqueous inclusions is interpreted to be a magmatic signature of stage iiia combined with the oxygen and hydrogen isotopic compositions 18 o h 2 o 6 8 to 11 9 d 77 to 62 these inclusions indicate that the initial fluid was likely derived from a magmatic source in stage iiib the gold was deposited at 263 to 347 c from a co 2 ch 4 h 2 o nacl fluid with a salinity of 5 33 to 11 05 wt nacl equivalent variable co 2 contents typically 9 15 mol and little ch 4 the oxygen and hydrogen isotopic compositions of this fluid 18 o h 2 o 8 1 to 8 8 d 44 to 32 indicate that it was mainly derived from a metamorphic hydrothermal source the co 2 h 2 o ch 4 nacl fluids that were responsible for gold deposition in the stage iiic veins had a wide range of temperatures 214 483 c salinities of 1 02 to 21 34 wt nacl equivalent variable co 2 contents typically 4 53 mol and up to 7 mol ch 4 the oxygen and hydrogen isotopic compositions 18 o h 2 o 8 5 to 9 8 d 70 to 58 were probably acquired at the site of deposition by mixing of the metamorphic hydrothermal fluid with deep seated magmatic water and then evolved by degassing at the site of deposition during mineralization the log f o 2 values from 28 26 to 35 51 also indicate reduced conditions for this fluid in stage iiic moreover this fluid had a near neutral ph and 34 s values of h 2 s of 2 32 to 0 83 which may reflect the derivation of sulfur from the subducted oceanic lithospheric materials the three orebodies represent different gold transportation and precipitation models and the conditions of ore formation are related to distinct events of hydrothermal alteration and gold mineralization the gold mineralization of the ulu sokor deposit occurred in response to complex and concurrent processes involving fluid immiscibility fluid rock reactions and fluid mixing however fluid immiscibility was the most important mechanism for gold deposition and occurred in these orebodies which have corresponding fluid properties structural controls geologic characteristics tectonic settings and origins of the ore forming matter these characteristics of the ulu sokor deposit are consistent with its classification as an orogenic gold deposit while some of the veins are genetically related to intrusions