geology u pb geochronology and stable isotope geochemistry of the tunca semi massive sulfide mineralization black sea region ne turkey implications for ore genesis abstract upper cretaceous volcano sedimentary sequences of the eastern pontide orogenic belt ne turkey are host to significant vms mineralization including near tunca the initial stages of felsic volcanism within the mineralized area are marked by the eruption of dacitic lavas and breccias of the kizilkaya formation this was accompanied by the emplacement of domelike hematitic dacites autobrecciated and volcaniclastic rocks both in situ and resedimented were likely generated from extrusive portions of these dacite bodies basaltic volcanism is marked by the eruption of the lava flows and pillow lavas of the caglayan formation hiatuses in basaltic activity are marked by thin horizons of volcaniclastics and mudstones the uppermost felsic volcanic units were accompanied by resedimentation of autoclastic facies from previous volcanism and represent the latest phase of upper cretaceous volcanism in the area the semi massive sulfide mineralization is associated with a late stage of the initial felsic volcanism u pb la icp ms zircon dating of a dacitic tuff breccia yielded an age of 88 1 1 2 ma coniacian upper cretaceous which is interpreted to be the age of the sulfide occurrences a concentric zoned alteration pattern is observed in the footwall rocks the alteration pattern is considered to have formed by lateral migration of hydrothermal fluids which had ascended along the discharge conduit fluid inclusion data indicate precipitation or mobilization processes within a relatively narrow temperature range of 152 255 c avg 200 c the low salinity fluids in the fluid inclusions less than 5 9 wt nacl equivalent are consistent with typical modified seawater dominant hydrothermal vent fluids sulfur isotope analysis of the tunca sulfides yields a narrow range of 1 5 4 1 per mil these 34 s values are also typical of many vms deposits most of the recorded 18 o values 7 1 to 14 0 per mil are greater than 9 per mil the most intensely hydrothermally altered rocks tend to have lower 18 o values relative to the less altered rocks collectively the geologic relationships mineralization style and the lack of seafloor ore facies suggest that mineralization is principally of sub seafloor origin the most geologically reasonable interpretation of the genesis of the tunca mineralization is the continuous interaction between the host rocks and seawater derived fluids without significant involvement of a magmatic fluid

from passive margin to continental collision geochemical and isotopic constraints for e morb and oib like magmatism during the neoproterozoic evolution of the southeast brasilia belt abstract metamorphic rocks derived from mafic rocks can be found in metamorphic belts and their geochemical and isotopic characteristics may be valuable sources of information for interpretation of ancient geologic magmatic scenarios the southern brasilia belt between the amazonian and sao francisco cratons in central brazil exhibits different amphibolite rocks that were emplaced into verissimo sequence and araxa group metasedimentary sequences during the neoproterozoic the obtained results indicate that the studied amphibolite rocks from pires do rio catalao area represent three magmatic events associated with three magmatic environments 1 a passive margin development at 979 ma a forearc back arc basin at 819 ma and a continental collision at 651 ma the first magmatic event related to continental extension and passive margin development is represented by the emplacement at 979 17 ma of e morb low k tholeiitic basalts with positive end t values between 4 4 and 2 and tdm between 1 26 and 1 82 ga related with the verissimo metavolcanosedimentary sequence the zircon populations include a high amount of metamorphic inherited grains the second magmatic event related with an forearc back arc extension is represented by e morb basalts with negative nb ta anomalies and slightly positive end t values of 0 78 to 2 71 cogenetic with the araxa group an oib like basalt sample is also related to this stage and has a u pb age of 819 7 6 3 ma end t values of 1 82 to 2 57 ehf t in zircon around zero and tdm ages from 1 03 to 1 18 ga the third event is represented by syn to late tectonic oib like basaltic gabbroic magmatism at 651 6 ma with positive end t value of 2 57 and younger tdm age at 1 18 ga that can be associated to regional continental collision and closure of the neoproterozoic ocean also provenance studies into metasedimentary rocks support that passive and active margins could be successively superposed during the main thrusting tectonic event in the brasiliano orogeny but slices of different stratigraphic units preserve their depositional isotopic signature these findings suggest that the occurrence of main mafic magmatic events over a timespan as long as the entire evolution of the brasilia belt 1 0 0 6 ma might be a key to individualize superposed tectonic basins in central brazil

evolution of a metamorphic fluid and its role in lode gold mineralisation in the central lberian zone the central iberian zone of spain and portugal contains numerous gold deposits of varying size age and host lithology previous work concentrated on single deposits leading to a need to apply a range of techniques to the region as a whole to form a model for metallogenesis throughout the region with this aim a number of occurrences of gold mineralisation in the south western central iberian zone were studied the central iberian zone consists essentially of greenschist facies metasedimentary units intruded by hercynian granitoids hercynian deformation occurred in three main stages the earliest d1 being the most intense quartz veining is common throughout the region and a vein chronology was established relative to these deformation events v1 veins are pre hercynian and may predate the precambrian sardic deformation v2 veins are syndeformational d1 and associated with peak greenschist metamorphism v3 veins are late kinematic syn to post d2 v4 veins are syn to post d3 occurring in the final stages of the hercynian and often associated with or post dating granites reactivation of vein sets by later fluids was common fluid chemistry studies of samples of known chronology indicate three main sources of fluid the dominant fluid throughout the region from v2 to v4 is a dilute aqueo carbonic fluid of varying composition the combination of fluid inclusion analyses and geochemical studies of wallrock alteration indicates that the fluid was the result of devolatilisation and dehydration during prograde metamorphism at varying depths the resulting aqueo carbonic fluids flowed upwards mixing with each other and with meteoric waters contact metamorphism associated with granite intrusions during the d3 deformation released further aqueo carbonic fluids which in some cases unmixed to form separate carbonic and aqueous inclusions circulation of meteoric waters was important during later stages d3 prolonged low temperature fluid rock interaction produced highly saline aqueous fluids which post date all major quartz veining no single set of characteristics exists for gold mineralisation in the central iberian zone deposits cover a wide spectrum but three main types have been identified 1 early d1 v2 syn peak metamorphic gold quartz veins associated with an aqueo carbonic fluid with high n2 and ch4 2 late kinematic d2 v3 veins often associated with late brittle faults again the fluid present at the time of formation was aqueo carbonic but with lower n2 and ch4 3 late v4 low temperature veins formed by a mainly meteoric fluid which was also responsible for remobilisation and concentration of gold in earlier deposits the gold mineralisation in the central iberian zone supports the continuum model for lode gold deposits gold was leached from metasediments during prograde metamorphism transported to shallower crustal levels and deposited wherever suitable traps occurred channelling of fluid from deeper levels resulted in the localisation of deposits close to major shear zones depositional sites were usually dilational zones in faults and more rarely folds but locally lithological controls were important h2o co2 unmixing was common but was not necessarily related to gold deposition

chemical weathering rates and atmospheric soil co2 consumption of igneous and metamorphic rocks under tropical climate in southeastern brazil abstract chemical weathering rates and atmosphere soil co 2 consumption of igneous and metamorphic rocks under tropical climate in southeastern brazil were evaluated using the chemical composition of surface waters and fresh rocks and soil horizon c in the upper sorocaba river basin surface water samples were collected between june 2009 and june 2010 and analyses were performed to assess ph electrical conductivity ec temperature and total dissolved solids tds including na k ca 2 mg 2 cl so 4 2 po 4 3 no 3 and sio 2 fresh rocks and c horizon samples were also collected taking into account their geological context abundance and spatial density to analyze major elements and mineralogy the concentration of tds and dissolved cations anions and silica increased during the dry period in relation to the wet period and the same behavior was observed for ph ec and temperature after corrections of anthropogenic contributions ca 21 t km 2 yr and atmospheric inputs ca 19 t km 2 yr the annual flux due to chemical weathering involving the igneous and metamorphic rocks was ca 29 t km 2 yr the co 2 atmospheric soil consumption in the upper sorocaba river basin was ca 0 2 10 6 mol km 2 yr and when extrapolated to the entire mantiqueira orogenic belt accounted an estimated consumption of 0 07 10 12 mol yr representing 0 6 of the total co 2 consumption flux derived from global average silicate weathering the chemical weathering rates of igneous and metamorphic rocks in the upper sorocaba river basin were estimated at 15 m my respectively the main weathering process in this watershed was the monossialitization with partial hydrolyses of bedrock minerals except quartz which was not weathered and remained in the soil profile the annual specific flux derived from igneous and metamorphic rocks at upper sorocaba river basin could be compared with watersheds in tropical climates however this value is higher than in other north american european asian and african granitoid watersheds and lower than in montane watersheds

new thermochronologic constraints on the evolution of the zaldivar porphyry copper deposit northern chile life spans and thermal evolution of hydrothermal systems are of fundamental metallogenic importance we were able to establish the chronology and cooling history of the zaldivar porphyry copper deposit northern chile by applying a combination of different isotopic dating methods in minerals with different closure temperatures including 40ar 39ar geochronology and zircon fission track thermochronology together with fluid inclusion thermometry and previous published u pb zircon geochronology the hydrothermal mineralization in the zaldivar deposit is genetically related to the llamo porphyry unit samples of igneous biotites from this intrusion yielded 40ar 39ar plateau ages between 35 5 0 7 and 37 7 0 4 ma defining a weighted average of 36 6 0 5 ma 2 in contrast one sample from the zaldivar porphyry one from the andesites and two from the llamo porphyry yielded considerably younger fission track ages of approximately 29 ma with a weighted mean for all ages of 29 1 1 7 ma 2 thermal and compositional constraints for the hydrothermal system in the zaldivar deposit from fluid inclusions thermometry show that at least three fluid types broadly characterize two main hydrothermal episodes during the evolution of the deposit the main mineralization and alteration event is characterized by high temperature above 320 c hypersaline fluids salinity between 30 and 56 wt nacl equivalents coexisting with low density gas rich inclusions salinity less than 17 wt nacl equivalents that homogenizing into the gas phase at temperatures above 350 c the second episode corresponds to a low temperature event which is characterized by liquid rich fluid inclusions that homogenize into the liquid phase at temperatures ranging from 200 c to 300 c with salinities lower than 10 wt nacl equivalents the 40ar 39ar data 36 6 0 5 ma weighted average obtained from igneous biotites represent the minimum age for the last high temperature above 300 c hydrothermal pulse when compared with previously published u pb ages 38 7 1 3 ma in zircons from the llamo porphyry a close temporal relationship between crystallization of the parental intrusion and the thermal collapse of the last high temperature hydrothermal event is evident cooling took place from approximately 800 c crystallization of the intrusive complex defined by zircon u pb ages to below 300 50 c biotite 40ar 39ar closure temperature within approximately 1 5 m y because the thermal annealing of fission tracks in zircons occurs at temperatures of 240 30 the zircon fission track zft ages of 29 1 1 7 ma 2 mark the end of the thermal activity in the zaldivar area specifically the time when the whole area cooled below this temperature well after the collapse of the main hydrothermal event in the zaldivar porphyry copper deposit this cooling age roughly coincides with the age defined for the emplacement of dacitic dikes at 31 2 8 ma 2 published k ar whole rock 5 km south of the zaldivar deposit in the escondida area this late magmatic pulse probably is responsible for high heat flow in the zaldivar deposit as late as 29 ma there is no evidence that the low temperature hydrothermal pulse recognized by fluid inclusion studies is related to this thermal event the zircon fission track cooling ages are interpreted to be related to the time lag required for complete relaxation of the perturbation of the isotherms in the geothermal field imposed by the intrusion of magmatic bodies with or without any association with low temperature hydrothermal activity

fluid inclusions in quartz from oceanic hydrothermal specimens and the bingham utah porphyry cu deposit a study with pixe and sxrf abstract individual natural fluid inclusions in quartz were selected for non destructive microprobe analysis by synchrotron x ray fluorescence sxrf and proton induced x ray emission pixe in order to compare and contrast the compositions of porphyry type ore forming brines and two types of ocean crustal brines the inclusions contained brines with high salt concentrations typically 20 40 wt total and one or more daughter crystals the x ray and proton beams produced detectable characteristic x rays for many elements and allowed the quantification of concentrations for many elements with atomic number z 14 fluid inclusions associated with the core of the bingham ut porphyry cu mo deposit contain nacl brines that also contain element typical range in ppm k 12 000 100 000 ca 17 000 mn 8000 fe 120 000 cu 8000 zn 5000 br 2000 these values are in good agreement with published estimates and results from sxrf and pixe experiments are generally consistent the bingham fluid compositions closely resemble brines from the porphyry mo cu deposit at questa nm inclusions from two suites of oceanic plutonic rock samples gave pixe results consistent with published sxrf analyses from other inclusions in the same samples new inclusion analyses from the mathematician ridge locality indicate the nacl brines also contain on average element ppm k 3500 ca 35 000 mn 4900 cu 400 zn 200 br 1000 new inclusion analyses from the oceanographer transform locality indicate nacl brines that also contain on average k 37 000 ca 35 000 mn 10 000 cu 400 zn 2200 br 1000 these values are calculated on the assumption that fe in the inclusions is 50 000 ppm compared to continental ore forming brines the oceanic brines have higher ca and lower k and cu concentrations

brazilian structural provinces an introduction abstract the territory of brazil coincides almost entirely with the south american platform the crystalline core of the continent its basement is composed of ancient metamorphic and igneous rocks and it has not suffered any tectonic regeneration since the beginning of the phanerozoic sedimentary rocks with almost horizontal bedding cover this crystalline basement this latter shows ages as old as early precambrian although ages between 500 and 1000 m y are conspicuously frequent the cratonic areas became consolidated more than 1700 m y ago whereas the fold belts formed essentially between 500 and 1700 m y ago the sedimentary cover accumulated from the early silurian in three large intracratonic basins until the platform became completely stabilized a late jurassic to early cretaceous reactivation caused by the break up of the ancient gondwana continent created another basin sequence chiefly along the atlantic continental margin based on the nature of the crystalline basement rocks and the sedimentary cover ten structural provinces can be distinguished 1 rio branco province in the north of the country occupied by the guyana shield and still only poorly known with an important fold belt developed during the so called transamazonian cycle 2000 200m y with high grade metamorphic rocks and only slight influence of later events 2 tapajos province in central brazil corresponding to the amazonas or guaporecraton showing chiefly precambrian crystalline rocks and behaving as an cratonic area during the phanerozoic 3 sa o francisco province located on the atlantic shield with its basement covered by rocks of different ages chiefly affected by the brasiliano cycle between 1000 and 500 m y and constituting another cratonic area 4 tocantins province between the amazonas and sa o francisco cratons with the oldest rocks in its centre ages over 2600 m y and at the eastern and western borders metamorphic sequences of various fold belts and almost no phanerozoic deposits 5 mantiqueira province located along the southern part of the atlantic coast affected chiefly by the brasiliano folding cycle 6 borborema province in the northeast brazilian fold belt affected by the brasiliano cycle in a very complex way and with important faulted zones it was reactivated in phanerozoic times when also sedimentary covers accumulated 7 amazonas province represented by the amazonas sedimentary basin syneclise and subdivided into four parts by three important arcs 8 parnaiba province coinciding with the piauf maranha o syneclise and filled with a rather thick sedimentary sequence 9 paranaprovince the sedimentary basin of southern brazil in which the well known late paleozoic glaciation features are found and which possesses an extensive cover of basaltic rocks of late jurassic to early cretaceous age 10 coastal province and continental margin the youngest structural unit developed during the separation of the continent and represented by rift valleys and coastal basins filled with mesozoic cenozoic deposits of various kinds

tectonic evolution of south america during the late proterozoic abstract this paper discusses the evolution and the late proterozoic assembly of the south american continent i e the west gondwana under the light of global tectonics the northern portion of the continent the amazonian craton is a pre brasiliano domain it may be a fragment derived from laurentia this domain behaved as a large continental plate which was accreted to the central and southeastern portions of the continent brasiliano domain the brasiliano domain had a more complex history and composition during the brasiliano cycle middle proterozoic to early paleozoic in the brasiliano domain several late proterozoic continental plates have been identified sao luiz west africa congo kasai sao francisco rio de la plata arequipa antofalla which acted as forelands to the brasiliano orogenic belts that surround and amalgamate these plates smaller fragments of pre brasiliano continental lithosphere are common in the interior of the brasiliano orogenic belts and played diversified roles microplates microcontinents structural highs some of them have acted as true backlands hinterlands flanked by arc magmatism two principal types of brasiliano orogenic belts are recognized between the continental plates a marginal orogenies to the late proterozoic plates with pelitic carbonatic rocks and discrete volcanism which were thrust by collision onto the margin of the plates and which seem to represent final products of previous passive margin sequences b distal orogenics internal belts within the continental masses sometimes a branching system of orogenics that contain varied clastic and minor carbonate sedimentary rocks accompanied by important bimodal volcanism and calc alkaline plutonism for these orogenies a greater variety of basinal scenarios and tectonic settings may be visualized the amalgamation of the continent during the late proterozoic i e the formation of the brasiliano structures indicates the existence of practically synchronous multilateral stresses within lithospheric plates this can be produced by complementary adjustment of the continental plates as a response to major global events elsewhere analogous to modern continental collisions two large and important tectonic zones may be candidates to such a scenario the hijaz mozambique zone site of connection of east and west gondwana and the transbrasiliano lineament which cuts across south america and extends to north africa following the zone of connection between pre brasiliano and brasiliano domains other small ocean openings and closings inside the various brasiliano areas dom feliciano gariep for instance were minor events and complementary to the other two major tectonic zones mentioned above

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

fluid inclusion and h o isotope evidence for immiscibility during mineralization of the yinan au cu fe deposit shandong china abstract the fluid inclusion and h o isotope studies have provided the evidences for the source of ore forming fluids and helped to recognize two types of immiscibility and their relationships with mineralization hydrogen and oxygen isotopic geochemistry shows that the earlier ore forming fluids during the anhydrous skarn stage i and the hydrous skarn magnetite stage ii were mainly derived from magmatic water while the later fluids during the quartz sulfide stage iii and the carbonate stage iv were mainly from magmatic water mixed with small amounts of meteoric water various types of fluid inclusions including abundant vapor or liquid rich two phase aqueous inclusions daughter minerals bearing multiphase inclusions co2 h2o inclusions and less abundant liquid inclusions vapor inclusions and melt inclusions are present in hydrothermal minerals of different stages the liquid vapor fluid inclusions are mainly composed of h2o with significant amounts of co2 and a small amount of ch4 in the opaque bearing fluid inclusions the hematite and fahlore tetrahedrite were identified the homogenization temperature of the aqueous fluid inclusions decreases from stage i 520 410 c through stage ii 430 340 c and iii 250 190 c to stage iv 190 130 c the coexistence of melt inclusions with simultaneously trapped vapor or liquid rich two phase aqueous inclusions and daughter minerals bearing multiphase inclusions in garnet diopside and epidote of stages i and ii suggests an immiscibility between silicate melt and hydrothermal fluid it is an effective mechanism on scavenging and transporting ore forming components from magmas the aqueous fluid inclusions with various vapor liquid ratios from 65 commonly coexist with simultaneously trapped liquid inclusions vapor inclusions daughter minerals bearing multiphase inclusions and co2 h2o inclusions in the quartz of stage iii and the different kinds of the fluid inclusions have similar homogenization temperatures this indicates that the boiling another kind of immiscibility widely took place during stage iii it resulted in the precipitation and enrichment of gold copper and iron

peralkaline granitoid magmatism in the mongolian transbaikalian belt evolution petrogenesis and tectonic significance article i nfo the central asian orogenic belt caob is well known for its massive generation of juvenile crust in the phanerozoic in eastern caob voluminous peralkaline and alkaline alkali feldspar granitoids and genetically related bimodal volcanics were emplaced in three stages from early permian to late mesozoic 295 270 ma 230 190 ma and 150 120 ma they occur as huge granitoid belts in extensional tectonic settings and form a complex network of about 12 million km 2 in area among them the 2500 km long mongolian transbaikalian belt mtb is the most spectacular and it comprises more than 350 granite syenite plutons and stocks with numerous co genetic volcanic fields the three stages of granitoids have similar chemical compositions but show temporal variation in nd isotopic composition initial end t values range from 1t o 5 for the early permian 0 to 4 for the early mesozoic and 2t o 3 5 for the late mesozoic granitoids the negative end t values observed in the mtb are not typical of the caob granitoids which are generally characterized by positive values however several pieces of evidence suggest that the mtb peralkaline and alkali feldspar granitoids were produced from enriched mantle derived sources the evidence includes 1 felsic and mafic rocks formed in the same stage have similar initial nd sr isotopic ratios and sm nd model ages tdm 2 the granitoid belts extend over thousands of kilometers and intersect distinct crustal provinces but no correlation is found in chemical compositions between the granitoids and country rocks 3 the abundant syenites are considered to be cogenetic or in some cases parental to the granites experimental and isotope data argue for the derivation of syenites from an enriched mantle source thus the granites and comendites are regarded as mantle derived 4 a study of melt inclusions in quartz phenocrysts of comendite indicates a high liquidus temperature of 1000 1100 c for the magma generation this suggests that the silicic magma was generated in an unusually high temperature condition which is likely produced by basaltic magma that underplated the lower crust the generation of voluminous peralkaline and alkaline alkali feldspar granitoids and genetically related bimodal volcanic rocks represents an important addition of juvenile crustal mass to the earth s continental crust during a time span of about 150 ma from late paleozoic to late mesozoic

the composition of hypersaline iron rich granitic fluids based on laser icp and synchrotron xrf microprobe analysis of individual fluid inclusions in topaz mole granite eastern australia abstract high temperature 550 c hypersaline 50 wt salts fluid inclusions representative of the earliest hydrothermal fluids associated with the sn w cu pb zn mineralised mole granite of eastern australia are well developed in topaz from the fielders hill locality methods based on inductively coupled plasma emission spectroscopy following laser ablation and on synchrotron x ray fluorescence microanalysis are described and applied to the semiquantitative point analysis of these inclusions crushleach analysis provides further information as well as highlighting the importance of point methods when several generations of inclusions are present the laser icp results confirm the dominance of fe k and na in these early high temperature fluids the mean fe k na atomic ratios 0 95 0 79 1 00 are entirely in agreement with published experimental data on the composition of chloride brines in equilibrium with synthetic granite at magmatic temperatures and support the view that these fluids are direct products from a cooling granite magma a number of trace and minor elements have also been detected in the inclusions these include ca mg li b be ba sr and several of the ore metals order of magnitude estimates of the ore metal contents of these fluids based on combined xrf microprobe and laser icp analysis are in the percent range for fe mn and zn in the range from several hundred to several thousand ppm in the case of sn cu and pb and less than 600 ppm for mo and w these results have important implications for ore genesis in granitic environments and point to the very high ore carrying potential of high temperature hypersaline chloride rich brines exsolved from cooling granite magmas

exsolution of magmatic volatile phases from cl enriched mineralizing granitic magmas and implications for ore metal transport abstract to understand cl dissolution in aluminosilicate liquids and the exsolution of cl rich magmatic volatile phases experiments were conducted to determine the solubility of nacl kcl and h2o in felsic liquids at 0 5 and 2 kbar the cl content of h2o poor nacl saturated and kcl saturated silicate liquids is low i e 1 3 wt to very low i e 0 2 wt and varies with changes in pressure and composition the cl concentration increases with the f concentration and the molar al na ca mg si ratio of the liquid and decreases with increasing activity of h2o in the system exsolution of a volatile phase depends on the partial pressures of all dissolved volatiles and low cl solubilities in nacl saturated and kcl saturated silicate liquids imply that exsolution of a cl bearing volatile phase will occur early in cl bearing granitic magmas i e prior to extensive melt crystallization and or at comparatively low water fugacities the solubility behavior of h2o and cl is very similar to that of co2 and h2o in felsic liquids small quantities of co2 are known to facilitate volatile phase exsolution holloway 1976 and in a similar manner volatile phases may exsolve early in cl enriched granite magmas whereas 5 to 6 wt dissolved h2o is necessary for volatile phase exsolution from a co2 free and cl free haplogranite liquid at 2 kbar and 800 c a cl rich brine will exsolve if the liquid contains only 1 wt h2o and 0 26 wt cl at the same conditions these new solubility data are interpreted in light of h2o f and cl concentrations in felsic liquids determined from silicate melt inclusions to constrain the exsolution of cl bearing magmatic volatile phases from mineralizing granitic magmas felsic magmas genetically associated with cu porphyry and mo porphyry mineralization contain sufficient h2o and cl to become saturated with respect to a hypersaline brine without strong pressure reduction boiling of the volatile phase i e exsolution of immiscible vapor and brine or strong volatile enrichment resulting from extensive crystal fractionation experiments were also conducted to investigate the solubility of mo in highly saline volatile phases coexisting with granitic liquids at 2 and 0 5 kbar the apparent partition coefficient for mo in the volatile phase s relative to silicate liquid d mo is defined as the computed concentration of mo in a volatile phase or phases the measured concentration of mo in granite glass d mo ranges from 8 to 80 as the nacl and kcl content of the volatile phase s increases from 15 to 90 wt because mo does not complex with cl in aqueous fluids it appears that mo solubility may be a strong function of the activity of na and k in alkali chloride rich volatile phases

characterization and p t evolution of melt bearing ultrahigh temperature granulites an example from the anapolis itaucu complex of the brasilia fold belt brazil between garnet orthopyroxene and sillimanite and coronae or sapphirine quartz ultrahigh temperature metamorphism symplectites involving corundum sapphirine spinel cordierite plagioclase sillimanite orthopyroxene biotite and ilmenite the retrograde segment of the p t path was further constrained by biotite producing reactions a composite p t path was constructed

ages of protolith and neoproterozoic metamorphism of al p bearing quartzites of the veredas formation northern espinhaco brazil la icp ms age determinations on relict and recrystallized zircon and geodynamic consequences abstract the n s running espinhaco fold belt situated in the sao francisco craton in central eastern brazil separates this craton in a western and an eastern part along the paramirim corridor a brasiliano panafrican 650 500 ma deformation zone the meta sediments of the espinhaco basin consist of several synthems with dominantly siliciclastic deposits among them al and p rich lazulite bearing blue quartzite the amphibolite facies equivalent of a phosphatic sandstone of the veredas formation in the northern espinhaco form a conspicuous horizon zircon crystals from these quartzites have been dated using laser ablation inductively coupled plasma mass spectrometry the zircon crystals are both detrital and metamorphic in origin the latter exhibiting highly unusual textures produced by dissolution reprecipitation reaction and concomitant replacement of metamict areas ree y th u zircon fluid zircon xenotime detrital zircons reveal relict age groups of 3 1 3 3 ga 2 6 2 7 ga 2 0 2 3 ga and 1 5 ga the end of sedimentation and erosion of the magmatic and metamorphic rocks of the sao francisco craton can be estimated therefore as 1 5 ga the major metamorphic event recorded by reprecipitated zircon is neoproterozoic and documented by a lower intercept age of 634 19 ma which was calculated from analyses of individual spots on19 grains with a common relict orosirian rhyacian age of 2032 31 ma temporal equivalent to transamazonian the neoproterozoic age of the metamorphosed zircons of the vereda formation corresponds to the brasiliano panafrican remobilization of the sao francisco west congo craton along the eastern side of the espinhaco fold belt in the paramirim corridor

shrimp u pb and sm nd data for the araxa group and associated magmatic rocks constraints for the age of sedimentation and geodynamic context of the southern brasilia belt central brazil abstract shrimp u pb and sm nd isotopic data for araxa group micaschist associated amphibolite and intrusive tonalite were used to estimate the age and tectonic setting of deposition of the original detrital sediments in the southern part of the neoproterozoic brasilia fold belt one amphibolite sample from a layer interleaved tectonically within the metasedimentary rocks has the u pb zircon age of 838 20 ma its tholeiitic composition and depleted mantle isotopic signature e nd 5 1 suggests that it represents a tectonic slice of the former oceanic lithosphere separating the sao francisco and amazon continents u pb ages of detrital zircon grains and t dm model ages of the araxa group micaschists show a bimodal pattern interpreted as the result of provenance from two contrasting sources i young juvenile sources probably represented by igneous rocks of the goias magmatic arc in the west and ii paleoproterozoic sialic sources most probably belonging to the sao francisco craton in the east the detrital population is largely dominated by ca 666 682 ma old zircon grains derived from both mafic and felsic igneous source rocks detrital metamorphic grains and rims dated at ca 715 and 643 ma indicate that the original basin received sediments from neoproterozoic sources with a previous metamorphic overprint implying that young metamorphic rocks have been uplifted exposed and eroded providing sediment for at least part of what is presently mapped as the araxa group the youngest detrital zircon age of ca 643 ma represents the upper limit for deposition of the original detrital sediments their minimum age is constrained by the crystallisation of an intrusive tonalite at 638 11 ma the data suggest therefore that the araxa group metasediments were deposited and metamorphosed within a very short time interval most probably during the tectonic events related with the accretion of the goias magmatic arc to the eastern part of the brasilia belt and final closure of the goias ocean

seismic studies of the brasilia fold belt at the western border of the sao francisco craton central brazil using receiver function surface wave dispersion and teleseismic tomography abstract the tocantins province in central brazil is composed of a series of ssw nne trending terranes of mainly proterozoic ages which stabilized in the neoproterozoic in the final collision between the amazon and sao francisco cratons no previous information on crustal seismic properties was available for this region several broadband stations were used to study the regional patterns of crustal and upper mantle structure extending the results of a recent e w seismic refraction profile receiver functions and surface wave dispersion showed a thin crust 33 37 km in the neoproterozoic magmatic arc terrane high average crustal vp vs ratios 1 74 1 76 were consistently observed in this unit the foreland domain of the brasilia foldbelt on the other hand is characterized by thicker crust 42 43 km low vp vs ratios 1 70 1 72 were observed in the low grade foreland fold and thrust zone of the brasilia belt adjacent to the sao francisco craton teleseismic p wave tomography shows that the lithospheric upper mantle has lower velocities beneath the magmatic arc and goias massif compared with the foreland zone of the belt and sao francisco craton the variations in crustal thickness and upper mantle velocities observed with the broadband stations correlate well with the measurements along the seismic refraction profile the integration of all seismic observations and gravity data indicates a strong lithospheric contrast between the goias massif and the foreland domain of the brasilia belt whereas little variation was found across the foldbelt craton surface boundary these results support the hypothesis that the brasilia foreland domain and the sao francisco craton were part of a larger sao francisco congo continental plate in the final collision with the amazon plate

the influence of oxygen fugacity on tungsten and molybdenum partitioning between silicate melts and ilmenite the partitioning of molybdenum and tungsten between ilmenite ilm and silicic melts has been determined at 800 degrees c 1 kbar of pressure and at two oxygen fugacities at the oxygen fugacity of the graphite methane water buffer d super ilm melt mo 0 42 and d super ilm melt w 0 39 near the nickel nickel oxide buffer d super ilm melt mo 0 22 and d super ilm melt w 0 5 the variations in the partition coefficients with f sub o 2 are significant at the 0 06 and 0 33 levels for molybdenum and tungsten respectively the observed variation with oxygen fugacity is tentatively extrapolated to more complex systems and implies that the oxygen fugacity which prevails during magmatic crystallization may play a role in determining the mo w ratio in porphyry skarn or other hydrothermal mineral deposits examination of the literature on molybdenum and tungsten bearing mineral deposits indicates that systems with high w mo ratios are rather reduced and exhibit high ch 4 co 2 ratios in fluid inclusions low fe super 3 fe super 2 ratios in iron bearing minerals and low oxygen fugacities in associated igneous rocks on the other hand deposits with high mo w ratios are associated with rather oxidized magmatic systems we suggest that f sub o 2 dependent sequestration of molybdenum and tungsten in ferromagnesian phases during plutonic consolidation exerts a control on the relative efficiencies of removal of these metals from magmas into ore forming fluids

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

direct evolution of w rich brines from crystallizing melt within the mariktikan granite pluton west transbaikalia uneconomic tungsten mineralization associated with the mariktikan granite pluton of the transbaikalian igneous province eastern siberia is confined to a marginal part of the pluton referred to as the andreyevsky body this is composed of rocks similar to those of the main pluton but is likely to be an autonomous although kindred body on the basis of cross cutting relationships between rock varieties and their textural features the crystallization history is subdivided into three stages of unequal duration melt and fluid inclusions related to each of them have been studied using microthermometric and micro analytical procedures including a technique for atomic emission spectroscopy of individual fluid inclusions opened by a laser microprobe during the main crystallization stage 1045 1012 c more than 70 of the parental magma is believed to have crystallized at the level studied resulting in the formation of a crystalline framework rigid enough for the appearance of fractures within which some portion of the intercrystalline melt accumulated giving rise to thin aplite veins almost complete crystallization of intercrystalline and fracture hosted melt occurred during the late stage 1012 990 c whereas during the final stage only small bunches of schlieric sometimes miarolitic pegmatite were formed from a few pockets of residual melt 990 917 c in spite of the low water content of the melt about 1 wt fluid separation took place from the onset of crystallization during the main crystallization stage the exsolved fluid divided into two immiscible phases co2 rich gas and salt rich liquid brine however it was homogeneous thereafter major ore components of the brine mn fe w displayed different behaviour as crystallization progressed w concentration was below 0 1 wt at the main stage attained 1 wt during the late stage and increased to 1 8 wt at the final stage comparison of these data with calculations carried out using estimated parameters for the parental magma enables us to infer that obtained concentration values are reasonable for the special case studied here however they are unlikely to be attainable if the magma is h2o enriched and lacks an anomalously high w content in the andreyevsky body of the mariktikan pluton the following features of the parental magma made possible the generation of w rich solutions 1 high liquidus temperature 1045 c and elevated cl content c 0 15 wt that resulted in enlargement of the fluid melt distribution coefficient c 10 2 low water content c 1 and elevated w content c 0 001 wt that provided a relatively high w h2o ratio within the system at the same time because of the low water content of the magma the total mass of w bearing solutions has proved to be insufficient for the production of large scale mineralization a reduced w content of the great bulk of the exsolved brine may have had an unfavourable effect as well

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

the mara rosa arch in the tocantins province further evidence for neoproterozoic crustal accretion in central brazil the mara rosa volcano sedimentary sequence consists of several nne trending belts of metavolcanic metabasalts to metarhyolites and metasedimentary rocks micaschists quartzites cherts exposed over large areas of the tocantins province a neoproterozoic brasiliano orogenic region in the central part of brazil the supracrustal belts are separated by terrains dominated by metatonalites and metadiorites and intruded by several post orogenic granitic and dioritic bodies these volcano sedimentary and associated metaplutonic rock associations have been previously interpreted as a typical granite greenstone terrain of the archaean basement in this paper we present geochronological and isotopic data for rocks of the metavolcanic metaplutonic rock association samples of a felsic metavolcanic rock from the posse gold mine and a metatonalite yielded u pb zircon ages of 862 8 ma and 856 7 13 ma respectively these are interpreted as crystallization ages of the igneous protoliths titanites from the same metavolcanic rock sample yielded a concordant recrystallization age of 632 4 ma sm nd isotopes for these rocks indicate primitive compositions with nd t of 4 6 and 3 7 and tdm model ages of 1 0 ga a syn tectonic dioritic intrusion has an u pb crystallization age of 630 6 ma and nd t of 1 9 and tdm of 1 0 ga additional sm nd analyses on metasedimentary rocks and post orogenic granites of the mara rosa region yield tdm ages between 1 2 and 1 0 ga the isotopic data combined with preliminary trace element results suggest that the protoliths of the metavolcanic and metaplutonic rocks investigated were formed in an island arc system off the coast of the sao francisco congo continent at around 860 ma recrystallization and deformational ages of 630 ma may represent the timing of final ocean closure and continental collision the rock associations structural pattern geochronological and isotopic characteristics of the rocks from the mara rosa region are very similar to those of neoproterozoic arc terrains exposed 300 km to the southwest in the arenspolis area proving the regional importance of the neoproterozoic crustal accretion event in the central part of brazil

a case study of the mountain lee wave event of january 6 1992 a mountain wave event observed at the southern tip of greenland on january 6 1992 was corroborated by three experiments the meteorological measurement system mms the microwave temperature profiler mtp and the reactive nitrogen instrument no noy gravity wave signatures with classical phase relationship between wind and temperature were observed on both the outbound and inbound legs at different altitudes the waves showed both vertically propagating and evanescent properties characteristics of the dominant wave mode are wavelength 35 km vertical displacement 0 8 km and peak to peak vertical wind 6 ms 1 with the prevailing wind at 37 ms 1 the stratospheric temperature was reduced by 6k to 195 5k within 8 minutes the implication and potential impact of mountain lee waves on the formation of polar stratospheric clouds psc s are discussed

solubility and stability of beryl in granitic melts beryllium contents of granitic melts at saturation in beryl or chrysoberyl phenakite or quartz have been determined by forward and reverse direction experiments at 650 850 degrees c and 200 mpa using natural beryl or the compositionally equivalent mixture of phenakite alumina quartz added to metaluminous haplogranite peraluminous haplogranite and macusanite a peraluminous li b f and p enriched rhyolite obsidian from macusani peru chrysoberyl coexists with beryl or quartz in moderately to strongly peraluminous systems asi approximately or 1 05 the assemblage phenakite beryl chrysoberyl is stable in silica undersaturated bulk composition the beo content of the melts which ranged between 0 03 0 40 wt varies principally with temperature the solubility of beryl falls with decreasing t and with the activity product of beryl alpha beo 3 alpha al2o3 alpha sio2 6 beryllia contents are lowest in strongly peraluminous and quartz saturated haplogranite melts however the highest beo content measured in glass products occurs for the strongly peraluminous macusanite at 850 degrees c 4016 ppm we infer that the greater solubility of beryl in macusanite melt results from melt speciation reactions involving li f b and p for all bulk compositions studied the beo content of melt projects to a narrow range of similar values at low t near the solidus of haplogranite thus metaluminous to peraluminous granitic magmas with and without common volatile and fluxing components will if cooled to subsolidus temperatures have similarly low beo requirements for beryl saturation the small beo content of melt near the solidus of haplogranite results in a minor 10 degrees c depression of the freezing point compared to be free haplogranite melt the mean melt composition at the beryl saturated granite minimum shifts slightly toward quartz beryl is common in peraluminous granitic rocks in part because lower beo contents are required to saturate these melts in beryl and possibly because these melts acquire higher beo contents by mica melting reactions at their sources beryl is also a common constituent of border facies assemblages in granitic pegmatite dikes regardless of their asi values this early crystallization of beryl results from the low beo content required to saturate any granitic melt in beryl at the low t environments in which pegmatite dikes solidify

terrane accretion and upward extrusion of high pressure granulites in the neoproterozoic nappes of southeast brazil petrologic and structural constraints the high grade crystalline nappes exposed southeast of the sao francisco craton comprise two distinct units of mainly granulite facies rocks that represent a composite section of neoproterozoic deep continental crust the socorro guaxupe nappe above derived from an arc terrane and the tres pontas varginha nappe below metamorphism in the tres pontas varginha nappe is characterized by the exceptional preservation of kyanite granulites 700 750 c 15 kbar and followed by limited retrogression maximum temperatures around 900 950 c were reached toward the base of the overlying socorro guaxupe nappe during the intrusion of charnockitic mangeritic magmas lower pressure metamorphism accompanied by anatexis prevailed at shallower crustal levels our petrological results document an inverted thermal structure with isobaric heating of the top of the high pressure granulite nappe both granulite nappes were transported more than 200 km eastward above lower nappes involving reworked basement and passive margin units both metamorphosed to high pressure but lower temperature conditions significant thinning and cooling of the two granulite nappes may have occurred before their emplacement onto the lower nappes the proposed geodynamic scenario considers that continental subduction took place westward underneath neoproterozoic oceanic lithosphere the two granulite units crystallised at 45 km depths under distinct paleogeotherms within this subduction zone around 630 ma the kyanite granulites were rapidely exhumed through the mechanism of low angle forced extrusion whereas syncollisional collapse affected the soft anatectic middle crust of the overlying arc terrane the final emplacement of the thinned nappe pile onto the cold sao francisco craton and its platform cover with at most anchizonal to greenschist facies metamorphism occurred around 600 ma

the geochemical signature of fluid saturated magma determined from silicate melt inclusions in ascension island granite xenoliths abstract silicate glasses in crystal free to crystal poor melt inclusions from two coarse grained granite xenoliths in alkaline volcanic rocks of ascension island were analyzed for 29 major minor and trace elements for most constituents the glass compositions are similar to those of the volcanic whole rocks and the xenoliths we interpret the glasses to be chemically representative of granite melt the melt inclusions are silicic alkaline contain low s and p abundances and are enriched in h 2 o cl f and na relative to k inclusions from one xenolith contain 1 3 wt f on average whereas those from the other xenolith contain half that amount the melt inclusion compositions allow investigation of the means and extent of granite magma evolution the presence of magmatic fluid inclusions in close proximity to melt inclusions in the phenocrysts indicates that the granite melt was saturated in one or more volatile phases roedder and coombs 1967 the cl and h 2 o contents of the melt inclusions are consistent with the exsolution of volatile phase s at pressures of 3000 to 2000 bars the glasses also show trends involving the cl h 2 o ratio and the incompatible trace elements in melt that are indicative of melt evolution via crystal fractionation of volatile phase saturated melt these trends should be useful for recognizing volatile phase saturation in other cl enriched melts

combined raman microprobe spectrometry and microthermometry of fluid inclusions in minerals from igneous rocks of the gardar province south greenland abstract raman microprobe spectrometry has been applied to analysis of the gaseous phase in individual fluid inclusions in minerals from alkalic igneous rock types and associated hydrothermal veins from the gardar province south greenland quantitative analyses are given for co2 ch4 c2h6 h2 and h2s traces of co were observed in one co2 inclusion in conjunction with data from microthermometry the results permit calculation of the bulk chemical composition of entrapped fluids and evaluation of the possible pressure temperature oxygen fugacity and sulphur fugacity during entrapment of the individual fluid inclusions calculated oxygen fugacity values correspond to those of the nno and qfm buffer reactions at temperatures of 300 400 c and pressures of 0 5 1 0 kbar calculated sulphur fugacity values are within the range of normal ore forming solutions log fs2 6 to 10

structure and strain variation at mid crustal levels in a transpressional orogen a review of kaoko belt structure and the character of west gondwana amalgamation and dispersal abstract the neoproterozoic cambrian kaoko belt is an orogen scale 800 180 km transpressional system important in the amalgamation of west gondwana mid crustal transpression at amphibolite to granulite facies conditions is dominated by two major 400 km exposed strike slip shear zones bounding a 20 40 km wide high grade orogen core to the east a deeply buried nappe dominated escape zone has inverted metamorphic sequence and verges outwards onto a platformal foreland to the west an arc like neoproterozoic coastal terrane was amalgamated and variably reworked during transpression the major purros and three palms mylonite zones have calculated shear displacements on the order of 120 180 km these shear zones are moderately to steeply dipping mylonite zones of 1 5 km width are arcuate and curvilinear in map view and show along strike variation in slip kinematics also highly curved in vertical section the shear zones define a flower to half flower geometry for the orogen core an oblique network of mylonitic shear zones akin to riedel shears links the major shear zones and defines regional scale shear lozenges internally deformed by tight upright folding and shear fabrics these shear zones create domains in the orogen core with varying dominance of pure shear in shear lozenges and simple shear in shear zones however absence of dip slip domains and the smoothly continuous traces of sub horizontal to shallow and acute oblique stretching lineations across all parts of the belt preclude marked kinematic partitioning and the internal part of the belt resembles large scale triclinic shear clast aspect ratios boudin train extension sheath fold aspect geometry degree of rotation of planes producing flanking folds composite s c foliations pressure fringes on pyrite and garnet porphyroclasts provide a semi quantitative measure of strain intensity average strain ratios are x z 40 1 for the major shear zones x z 12 1 for the orogen core x z 8 1 for the escape zone and x z 3 1 for the coastal terrane a more continuous pattern of strain intensity across the whole belt is mapped using a qualitative foliation intensity index foliation traces have a sigmoidal pattern in the orogen core swinging from sub parallel to the boundary shear zones to higher acute angles in the internal parts deformation character also varies from upright open folding in amphibolite facies domains in the north upright tight chevron folding in a low grade central domain to a high grade domain of tight to isoclinal inter folded basement and cover with inclination decreasing towards the south the kaoko belt is a well exposed sector of an extensive 3000 km long broad 400 km arcuate orogenic system adamastor orogen that amalgamated west gondwana bringing the south american sao francisco and rio de la plata cratons and african kalahari and congo cratons components together though a complex system most sectors involved oblique collision and accretion of magmatic arcs of 660 610 ma age followed by peak metamorphism and main phase transpressional orogenesis between 585 and 560 ma with shear zones remaining active until 530 ma this e w amalgamation immediately pre dates the final n s amalgamation of gondwana along the kuunga orogen between 535 and 510 ma the large scale adamastor orogen consisting of kaoko dom feliciano ribeira aracuai and west congo mobile belts also shows broadly similar and symmetric structural architecture throughout the high grade thermally softened core partitioned intense wrench dominated strains and networks of transcurrent shear zones that dip inwards with listric form either side of the internal zone containing amalgamated arcs and high grade core are nappe fold and thrust belts that rework attenuated passive margin basement and adamastor ocean sediments and structures verge outward at moderate to high angles onto both foreland margins the kaoko belt well illustrates the highly partitioned nature of transpressional systems in general and patterns in common throughout the greater adamastor orogen such as metamorphic zonation and heterogeneous distribution of deformation style flow regime and highly variable degrees of reworking strain and recrystallization this highly partitioned and steep structural grain localized lithospheric extension and rifting 415 ma later during breakup and dispersal of gondwana

the touquoy zone deposit an example of unusual orogenic gold mineralisation in the meguma terrane nova scotia canada the touquoy zone deposit is host to disseminated gold mineralisation in metasiltstones of lower palaeozoic age from the close correlation between ore grades and the intersection of favourable stratigraphy and bounding faults it is apparent that mineralisation is controlled by both structural and lithological influences within the ore zone disseminated gold arsenopyrite pyrite and rare base metal sulphides are associated with a network of widely spaced millimetre scale quartz carbonate veinlets quasi pervasive fluid flow and prolonged interaction with the host rocks resulted in a diffuse but pronounced halo of wall rock alteration that is characterized by the breakdown of detrital feldspar and metamorphic chlorite and the development of hydrothermal carbonate phases k mica and disseminated sulphides these mineralogical changes are accompanied by enrichment in co2 k au as and s and depletion in na across the ore zone vein formation occurred at between 250 and 350 c and pressures of less than 1 2 kbar 1 kbar 100 mpa corresponding to an estimated depth of between 2 8 and 6 km mineralisation resulted from the unmixing of an overpressured low salinity co2 rich fluid in response to decreasing pressure during its ascent and penetration into permeable host rocks geological and geochemical features of mineralisation in the touquoy zone deposit are seen as convincing evidence for a close genetic association between disseminated style and lode gold mineralisation in orogenic terrains with the resulting style of mineralisation largely controlled by the overall structural geometry of the mineralising site rheological properties permeability and chemical receptiveness of the host rock and structural level of emplacement

influences of gravity waves on convectively induced turbulence cit a review thunderstorms are known to produce turbulence such turbulence is commonly referred to as convectively induced turbulence or cit and can be hazardous to aviation although this turbulence can occur both within and outside the convection out of cloud cit is particularly hazardous since it occurs in clear air and cannot be seen by eye or onboard radar furthermore due to its small scale and its ties to the underlying convection it is very difficult to forecast guidelines for out of cloud cit avoidance are available but they are oversimplified and can be misleading in the search for more appropriate and physically based avoidance guidelines considerable research has been conducted in recent years on the nature of the phenomenon and in particular its connection to gravity waves generated by the convection this paper reviews the advances in our understanding of out of cloud cit and its relation to convective gravity waves and provides several detailed examples of observed cases to elucidate some of the underlying dynamics

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

climatology of high cloud dynamics using profiling arm doppler radar observations abstractice cloud properties are influenced by cloud scale vertical air motion dynamical properties of ice clouds can be determined via doppler measurements from ground based profiling cloud radars here the decomposition of the doppler velocities into reflectivity weighted particle velocity vt and vertical air motion w is described the methodology is applied to high clouds observations from 35 ghz profiling millimeter wavelength radars at the atmospheric radiation measurement program arm southern great plains sgp climate research facility in oklahoma january 1997 december 2010 and the arm tropical western pacific twp site in manus july 1999 december 2010 the doppler velocity measurements are used to detect gravity waves gw whose correlation with high cloud macrophysical properties is investigated cloud turbulence is studied in the absence and presence of gw high clouds are less turbulent when gw are observed probability density functions of vt w and high cloud macrophysical propert

aluminous granite as a source magma of hydrothermal ore deposits an experimental study partition ratios of zinc and lead between synthetic granitic melts and aqueous phase were determined at 800 degrees c and under p sub h 2 o 3 5 or 0 25 kb two starting glasses in the system sio 2 al 2 o 3 cao na 2 o were prepared their bulk chemical compositions are similar i e sio 2 content of 75 65 percent in glass 1 and of 74 68 percent in glass 2 glass 1 is prepared to be slightly alkaline with 1 89 percent normative wollastonite and glass 2 is slightly aluminous with 2 42 percent normative corundum the partition ratio of sodium between aqueous fluid and melt k p na can be expressed by the following equation over the whole range of chloride concentrations in the aqueous solution m v cl mole kg regardless of the normative composition of the melt k p na 0 468 x m v cl however the partition ratio of zinc k p zn for the aluminous melt is more than two orders of magnitude larger than that for the alkaline melt k p zn varies with the square of the chloride concentration in the aqueous phase and is satisfied by the following two equations k p zn 9 40 x m v cl 2 aluminous melt 2 and k p zn 0 0833 x m v cl 2 alkaline melt 1 a similar contrast was also observed in the partition ratios of lead between aqueous phase and melts k p pb 2 26 x m v cl 2 aluminous melt 2 and k p pb 0 0474 x m v cl 2 alkaline melt 1 the log of the partition ratio shows an excellent inversely proportional relation with the ph at 25 degrees c of the aqueous solution which was equilibrated with granitic melts and quenched a slope of 2 is obtained for alkaline melt and is reasonably explained by the equation pbo melt 2h super vapor 2cl super vapor pbcl sub 2 vapor h 2 o the slope for the aluminous melt 1 2 may be explained only by complex reactions involving silicate ligands in the melt the results indicate that only aluminous granite is capable of producing hydrothermal fluids which would contain a significant amount of ore metals in other words aluminous granite can be ore bearing by postmagmatic processes this is likely to happen when a granitie magma which originally was slightly alkaline changed its composition to slightly aluminous during diapiric uplift by assimilation of pelitic sediments if this compositional evolution happened then granitic magma would tend to store up base metals during the early stages of its evolution and release them very efficiently in the later stages to form a hydrothermal ore solution

microthermometric study of silicate melt inclusions in variscan granites from se germany volatile contents and entrapment conditions melt inclusions in granitic rocks are generally crystalline and must oberpfalz regions along the northern margin of the be homogenized to glass before analysis we employ a simple kinetic bohemian massif some of these granites particularly in technique with microthermometry to estimate total volatile contents the german erzgebirge are highly evolved geochemically and p t conditions of trapping of the melts from their hoand famous for the tin and uranium mineralization mogenization behaviour this information complements chemical associated with them several publications have condata from microprobe or ion probe analysis and can be obtained centrated on the geology geochemistry and ore from inclusions too small for direct analysis we present here values associations of the granites forster tischendorf 1994 for volatile contents as equivalent wt h2o trapping temperatures seltmann 1994 tischendorf forster 1994 hecht et and trapping pressures derived from studies of melt inclusions in some al 1997 siebel et al 1997 but their magmatic volatile variscan granites of the erzgebirge fichtelgebirge and oberpfalz contents and emplacement level are difficult to determine germany the volatile concentrations range from 3 to 10 equiv wt and have not often been addressed the granites from h2o microprobe analysis shows that the most volatile rich these regions contain abundant melt inclusions and these inclusions contain up to 8 wt f estimates of trapping offer the potential of constraining melt water contents pressures and temperatures suggest that crystallization began at an and conditions of trapping emplacement level of 3 6 5 km near 700 c with normal biotite all three regions contain composite plutons or plutonic and two mica granites and ended with topaz albite granite complexes which range in composition from un 650 c and pegmatitic phases down to 520 c this wide differentiated biotite granites to more highly evolved tworange of trapping temperatures and volatile contents is a general mica granites and finally to extremely evolved granites feature of melt inclusions in granites many of the granites studied containing li micas and topaz in some cases this comare highly evolved geochemically but the extreme volatile enrichment positional range is covered by different units of a single typical for these also occurs locally in the unspecialized granites pluton e g falkenberg granite oberpfalz whereas in other places individual plutons are more restricted in composition the erzgebirge region is particularly rich

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

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

on homogeneous ice formation in liquid clouds primary ice formation by homogeneous freezing of supercooled cloud droplets in moist adiabatic air parcels is investigated theoretically and by means of numerical simulations dependencies of nucleated ice crystal number and size and associated freezing temperatures are systematically studied as functions of updraught speed and cloud droplet number and size droplet freezing temperatures range between 235 and 239 k depending on dynamical forcing and liquid water content vertical resolutions on the order of 10 m are required in numerical cloud models to resolve the thin layers in which homogeneous ice formation processes unfold only a fraction of droplets freeze in weakly forced clouds small scale variability in updraught speeds encountered by air parcels containing supercooled cloud droplets results in broad ice crystal number distributions when sampled across a parcel ensemble the strong dynamical control of ice initiation in tropospheric clouds initiates homogeneous freezing in the presence of heterogeneous ice nuclei even at moderate mean updraught speeds suggesting that such particles play a limited role in affecting droplet freezing in cold convective cloud outflow regions these findings have important implications for microphysical and optical properties of condensed phase convective detrainment setting the stage for the evolution of anvil cirrus

zircon and rutile upb geochronology of the niquelândia layered mafic and ultramafic intrusion brazil constraints for the timing of magmatism and high grade metamorphism abstract the niquel ndia intrusion is among the largest layered intrusions in the world it is part of a 350 km long belt of large mafic ultramafic complexes in central brazil both intrusion and country rocks were subjected to highgrade metamorphism ranging from amphibolite to granulite facies and associated ductile deformation the first u pb zircon and rutile ages for this region are presented zircon fractions from a meta anorthosite from the upper gabbro anorthositic unit are variably discordant 0 28 with regard to the lower intercept along a mixing line from 777 10 ma lower intercept and 1583 25 ma upper intercept zircon fractions from a later quartz diorite within the central mafic unit are variably discordant 0 14 with regard to the lower intercept along a mixing line from 794 6 4 lower intercept and 1565 22 upper intercept the upper intercepts for both rocks interpreted to be the magmatic age overlap and suggest a mesoproterozoic age for the intrusion the lower intercept is interpreted to be the high grade metamorphic event zircons from two quartz rich blastomylonites representing different metamorphic domains and cutting through the layered intrusions were analyzed a single zircon from the amphibolite facies domain blastomylonite gives a concordant 0 3 207 pb 206 pb age of 777 3 ma and a single zircon from the granulite facies blastomylonite gives a 207 pb 206 pb age of 786 5 ma 0 8 discordance both results are consistent with the lower intercept ages and set the 770 795 ma interval for the high grade metamorphic event rutile ages 650 ma are considerably younger than zircon metamorphic ages and suggest a milder regional tectonomagmatic episode or a complex and long lasting cooling history for the region the u pb data provide evidence for an important mesoproterozoic extensional tectonic event in central brazil it also sets the 770 795 ma interval for the high grade amphibolite to granulite facies prograde metamorphism interpreted to represent the timing of a continental collision event

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

origin of the fluids associated with granodiorite hosted sb as au w mineralisation at dubrava nizke tatry mts western carpathians mineral parageneses of the polymetallic sbrich deposit at dubrava has been formed during five separated stages a fluid inclusion study demonstrates that the earliest stages with scheelite molybdenite and arsenopyrite have been associated with immiscible co2 ch4 rich low saline fluids at temperatures between 300 and 400 c and pressures as much as 2 kbar deposition of the main superimposed ores stibnite and zinckenite has been intimately connected with circulation of aqeuous moderately saline fluids 15 5 23 5 wt nacl equiv upon epithermal conditions salinity of the aqueous fluids associated with tetrahedrite is clustered around 10 wt nacl equiv quartz from the latest barite stage has precipitated from aqueous fluids enriched in divalent cations these fluids are believed to be genetically linked with triassic evaporite formations preserved in the region temperature salinity diagrams constructed from microthermometry data indicate influx of diluted meteorite water in the stibnite tetrahedrite and barite stages isotopic data are in accordance with model the 18o values between 9 3 and 1 5 have been derived for water in equilibrium with quartz coexisting with sphalerite tetrahedrite and barite thus confirming the participation of isotopically lighter meteoric waters in the mineral forming solutions the 18o values between 3 3 and 8 5 estimated for the water associated with the scheelite and arsenopyrite stages are suggestive for the majority of metamorphic and or magmatic water in the mineral forming co2 rich solutions

first application of titanium in zircon thermometry to ultrahigh temperature metamorphism titanium in zircon thermometry has been applied to evaluate the temperatures of metamorphism for two ultrahigh temperature uht granulite localities the neoproterozoic anapolis itaucu complex in central brazil and lower crustal xenoliths from the neo archean kaapvaal craton in south africa uht metamorphism in the anapolis itaucu complex occurred ca 640 ma ti in zircon thermometry on metamorphic zircon yields temperatures of 965 811 c a population of late zircon that formed from ilmenite and rutile breakdown records temperatures of 780 c maximum temperatures are less than those inferred from quantitative phase equilibria modeling based on textural setting inclusions in peak phases and as matrix grains these zircons likely record growth during the pro grade and or postpeak evolution in contrast the kaapvaal xenoliths record two phases of zircon growth during uht metamorphism at 2720 2715 ma followed by growth during isobaric cooling in kyanite bearing leucosomes ca 2690 ma temperatures recorded by the two phases of growth are 1024 878 c and 936 839 c respectively suggesting that zircon growth occurred during uht conditions and continued throughout the postpeak evolution over a 200 c interval these examples demonstrate that the ti in zircon thermometer is a powerful new tool with the potential to determine crystallization temperatures of zircon during granulite facies metamorphism throughout the prograde to postpeak evolution of such terranes

immiscible phases of magmatic fluid and their relation to be and mo mineralization at the yermakovka f be deposit transbaikalia russia abstract melt and fluid inclusions in minerals from the peralkaline granite intrusion and associated mineralized country rocks from the yermakovka f be deposit were studied to characterize the behaviour of trace elements and exsolved fluids in the transition from magmatic to hydrothermal processes ore mineralization was mostly due to volatile release from a deep seated pluton for which crystallization history and fluid exsolution can be tracked by three batches of magma gr1 gr3 intruded at the level of the ore deposition to form the yermakovka stock each batch of the sequential granite group is found to intrude at decreasing temperature from 840 to 730 c and progressively increasing extent of crystallization of magma in the parental pluton this resulted in the enrichment of the ascending melts in h2o 3 9 to 6 1 wt f 2 6 to 4 1 wt and some incompatible elements zr nb th rb pb although the earliest evidence for the exsolution of homogeneous fluoride sulphate brine correlates with the final stage of the gr2 ascent the most intensive volatile s release from the emplaced magmas is shown to occur during their in situ crystallization which was associated with the separation of exsolved fluid into immiscible phases brine and low salinity solution compositions of these fluid phases are determined using atomic emission spectroscopy of the appropriate fluid inclusions opened by a laser microprobe and empa and sem eds analyses of daughter crystals the brine phase is enriched in mo mn be up to 17 8 and 0 3 g kg respectively and contains perceptible abundances of ce la pb zn whereas the low salinity phase is enriched only in be up to 0 6 g kg the selective mobilization of the metals from the melt into fluids is considered to result from the oxidized state of the melt and fluids peralkalinity of the melt during crystallization and high f content of the melt the immiscible fluid phases are shown to migrate together through the solidifying stock giving rise to the albitized granite that is enriched in molybdenite but devoid of be minerals in the country rocks solutions similar to the brine and low salinity phases of the magmatic fluid made up separate fluid flows which produced be and mo mineralization and were issued predominantly from the parental pluton both types of mineralization are nearly monometallic which suggests that of the metals jointly transported by the brine only mo and in part ce and la precipitated separately at the level where the low salinity solutions deposited be ores

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

high density co2 inclusions in the colorado front range a fluid density in an inclusion is commonly observed to be too low for the p t estimates for the postulated time of trapping and is generally attributed to a fluid loss during the uplift process it is more difficult to explain a fluid density which is too high in the 1700 m y front range migmatites such high densities occur in some of co2 inclusions which were deduced to have formed during the migmatization episode the peak p t estimates for migmatization in the front range are 4 6 kb and 650 700 c in sillimanite field but pressures required to form the most dense inclusions are 7 6 kb in kyanite field the high density is not likely to be a relic of a higher pressure condition earlier than the main migmatization episode for the following reasons a no kyanite or any other relic high pressure phase has been found in the precambrian front range b the high density inclusions are rare in zones with least signs of deformation and melting paleosomes and quartz inclusions within feldspar grains which instead contain relatively undisturbed early inclusions c high density inclusions with th 30 c are associated with heavily altered plagioclase caused by hydrothermal activity which was a late event in leucosome formation further there is evidence for post entrapment change s in density an intragranular trail in quartz contains co2 inclusions that exhibit almost the whole range in th 40 to 24 c as displayed by the entire population of the early co2 inclusions 66 to 30 c the density of an inclusion in the trail is not related to inclusion size but to the position of the inclusion relative to apparent micro shear zones crossing the co2 trail a change to a higher density a smaller volume could have resulted from an initially isobaric cooling path which intersects co2 isochores with increasingly higher densities additional excess pressure may have resulted from overthrusting however because high density inclusions occur selectively in the zones in which plagioclase shows alteration indicating a high a h 2 o and because there is a correlation between shear zones and high density inclusions it is postulated that local hydrolytic weakening of quartz was necessary for the decrease of inclusion volume which occurred during deformation the localized deformation may also result in an excess pressure however the introduction of a small amount of h2o into these inclusions as a possible cause of high density inclusions cannot be ruled out

resorption growth solid state recrystallisation and annealing of granulite facies zircon a case study from the central erzgebirge bohemian massif zircon crystals have been investigated from a gneiss area in the central erzgebirge bohemian massif where small occurrences lenses of granulites and sometimes eclogites are located within amphibolite facies gneisses geological relationships indicate that leucocratic quartzofeldspathic rocks within the granulite boudins represent melts whereas garnet rich melanocratic rocks are considered restites derived through multiple extraction of the leucocratic melts the morphology of zircon crystals is quite different in these two types of granulites with rounding pointing to higher zircon resorption in garnet rich rocks due to multiple interaction with melts extensive new zircon growth can be demonstrated within granulitic boudins on the basis of zircon morphology internal zircon textures and age data the newly formed zircon grains and rims are non cathodoluminescent and yield an age of about 340 ma secondary ionisation mass spectrometry sims and zircon evaporation raman microprobe investigations revealed heterogeneous metamictisation within zircon grains and pronounced damage of the zircon structure in u rich non cathodoluminescent zircon rims the common reverse discordance of such non cathodoluminescent zircon rims may be explained as a result of preferential pb sputtering during sims analysis leading to apparent pb excess which seems to occur principally in the most damaged zircon domains it is proposed from field relationships that surrounding gneisses although equilibrated under amphibolite facies conditions experienced the same metamorphic pt history as the granulites these amphibolite facies rocks contain zircon distinct from the granulite zircon populations with morphologies and internal textures typical for their protolith rocks implying only slight zircon changes due to hp overprint new zircon growth is here mostly limited to the appearance of very rare new grains or more commonly to formation of thin overgrowths the internal texture of these zircon crystals shows clear signs of solid state recrystallisation leading in most cases to a partial resetting of their u pb ages mainly due to pb loss in addition u contents are slightly higher in cl dark rims that we interpret to have formed mainly due to solid state recrystallisation most evaporation and sims ages vary between protolith rock age and 340 ma so that the interpretation of the 340 ma age is not unambiguous it could be explained as the age of zircon crystallisation from a u rich and th depleted melt or alternatively as a resetting age due to solid state recrystallisation resulting from melt or fluid interaction with old zircon it is difficult to determine at which stage of metamorphic evolution new zircon growth occurred in the granulitic boudins and remains unclear that zircon growth occurred at peak metamorphic conditions

u pb ages of detrital zircon grains for the canastra group and passos nappe units and u pb and lu hf isotope analyses from orthogneisses provenance and tectonic implications southern brasilia belt brazil abstract the age and tectonic setting of mesoproterozoic to neoproterozoic covers that occur along the southwestern margins of the sao francisco craton sfc are still uncertain this study reports new 207 pb 206 pb la icpms ages of detrital zircon grains from metasedimentary rocks of the passos nappe units and canastra group and combined u pb and lu hf analyses on igneous zircon from orthogneisses within the metasedimentary units the u pb age spectra of detrital zircon grains of the canastra group comprises a wide range from 1 30 2 71 ga with a significant rhyacian component source 2 1 ga the second major source is represented by statherian grains 1 6 1 7 ga and are similar to the statherian interval at espinhaco basin the youngest ages fall around 1 30 ga this peak age is compatible with the initial extension and sedimentation of the carandai and middle espinhaco basins which mark the second intracratonic rifting of the sao francisco craton zircon grains from the metasedimentary rocks the passos nappe yielded a very prominent rhyacian peak at ca 2 10 ga with some statherian and neoarchean contributions all samples from the metasedimentary units show a prominent peaks at ca 2 10 ga suggesting that most sedimentary sources derived from a rhyacian substratum similar to the mineiro belt natividade cavalcanti block campinorte complex and juiz de fora complex rhyacian age is compatible with u pb crystallization ages of felsic orthogneisses 2122 67 and 2117 23 enclosed as tectonic lenses in the passos nappe and the canastra group these rocks show initial e hf t values between 2 1 to 13 0 and 10 0 and 1 8 indicating that these orthogneisses are derived from rhyacian granitic rocks which were formed either by fractionation or re melting of juvenile magmas and by the reworking of more ancient mainly archean crust the new data and regional geologic correlations suggest evidence of paleoproterozoic terrain in the southwestern margin of the sfc

contrasting fluid chemistries alteration characteristics and metamorphic timing relationships recorded in hybridized orebodies of the missanabie renabie gold district archean wawa subprovince ontario canada

neoproterozoic granulite facies metamorphism and coeval granitic magmatism in the brasilia belt central brazil regional implications of new shrimp u pb and sm nd data abstract new shrimp u pb zircon ages combined with sm nd isotopic characteristics of granulites and associated granitic rocks of the anapolis itaucu complex in the central southern part of the brasilia belt are presented and discussed in this study igneous crystallization ages obtained in zircon grains of orthogranulite and granites vary between 760 and 650 ma growth of new zircon at ca 650 640 ma dates the high grade metamorphism zircon cores from paragranulites and granites give u pb ages between 2 0 and 0 8 ga tdm model ages of the granulitic rocks fall into two age intervals 2 3 1 9 and 1 7 1 4 ga end t values are negative varying between 9 29 and 1 42 shrimp u pb ages of zircon cores indicate that the granulite sedimentary protoliths were deposited after 800 ma ago contradicting previous models which assigned paleoproterozoic or archean ages for these rocks their nd isotopic signature indicate that paleoproterozoic sources within the sao francisco craton as well as younger sources such as the goias magmatic arc contributed to the sediment infilling of the former basin the intrusive granites display nd model age pattern similar to that of the granulitic rocks with most tdm model ages ranging between 1 45 and 1 2 ga end t values are between 2 61 and 7 96 indicative of assimilation of older material by the original magma shrimp u pb data for the granite intrusions indicate that granitoids metamorphosed under amphibolite facies show strong inheritance between 2 1 and 0 8 ga and magmatic metamorphic age at ca 660 650 ma the syn granulite facies granitoid ana 1 gave magmatic and metamorphic ages of ca 650 ma without any discernible inheritance the growth of new zircon occurred at the same time of the high grade metamorphism probably related with the collision event between the goias magmatic arc to the west southwest and the sao francisco craton to the east the data suggest that the anapolis itaucu complex instead of representing the ancient sialic basement of the supracrustal rock units of the brasilia belt constitutes a neoproterozoic high grade metamorphic complex related with the evolution of the brasiliano orogen

vertical velocities and turbulence in midlatitude anvil cirrus a comparison between in situ aircraft measurements and ground based doppler cloud radar retrievals this study introduces a statistical comparison of vertical velocity observations within cirrus from aircraft and ground based doppler cloud radar two cases of midlatitude anvil cirrus forming under very similar environmental conditions are examined the case studies benefit from simultaneous observations of vertical velocities in cirrus collected at and around the atmospheric radiation measurement southern great plains site during the u s department of energy small particles in cirrus field campaign observations from both platforms suggest that the majority of vertical velocities in the examined midlatitude anvil cirrus cases are roughly within 1 m s 1 although higher vertical velocities are occasionally observed the quality of the vertical velocity comparison between in situ aircraft measurements and ground based doppler radar retrievals depends on the case for the first case on 23 april 2010 the comparison suggests that the radar retrieval may underestimate vertical velocities in the range between roughly 50 cm s 1 and 1 m s 1 for the second case on 14 june 2010 the agreement between radar and aircraft is excellent and the differences are largely within the observed variability of vertical velocities within cirrus differences in the spatial scales of vertical velocities and turbulence sampled by the aircraft and doppler radar which arise due to differences in the temporal resolution of the observational platforms are not found to explain the observed discrepancies estimates for the dissipation rate of turbulent kinetic energy agree to within 1 order of magnitude between the two observational platforms

trapped gravity waves and their association with turbulence in a large thunderstorm anvil during pecan abstractgeostationary operational environmental satellite 14 goes 14 1 km visible satellite data with 1 min frequency revealed horizontally propagating internal gravity waves emanating from tropo

immiscibility of magmatic fluids and their relation to mo and cu mineralization at the bangpu porphyry deposit tibet china abstract the coexistence of aqueous fluid inclusions and silicate melt inclusions in quartz phenocrysts from porphyrites at the bangpu porphyry mo cu deposit tibet china were examined to characterize the immiscibility processes during the magmatic to hydrothermal transition the physical and chemical environment during crystallization of the magmas has been reconstructed on the basis of microthermometric experiments and trace element microanalysis compositions of melt and brine fluid phases are determined using synchrotron radiation x ray fluorescence analysis sem eds and laser raman spectroscopy analyses brine fluids were directly exsolved by a crystallizing melt and the simultaneous entrapment of volatile rich brine fluid and volatile poor immiscible phases silicate melt occurred at 670 700 c and 1 6 1 95 kbar when the magma had h2o contents between 5 and 6 wt and crystal contents of 60 80 a later low density fluid with a higher mo concentration exsolved after about 80 90 crystallization had occurred this fluid contained significant concentrations of cl na k ca fe cu zn rb and small amounts of mn br and pb immiscibility of magmatic fluids can lead to different metal partitioning behaviors between residual melt and volatile phases which generate variable metal ratios copper was partitioned preferentially into the brine phase in contrast to the behavior observed in other porphyry cu deposits ore deposition by a dense brine could explain the partially deep cu mineralization condensation of brine from a later low density parental fluid could be an efficient mechanism to concentrate shallow cu mineralization and broadly distributed mo mineralization the source of the mo mineralizing fluids probably was a particularly large magma chamber that crystallized and fractionated at depth greater than upper continental crust level

fluid regimes fault valve behavior and formation of gold quartz veins the morro do ouro mine ribeira belt brazil abstract fluid inclusion studies petrographic analyses and structural analyses for neoproterozoic auriferous veins from the morro do ouro mine ribeira belt southeastern brazil are presented the deposit is classified as an orogenic gold deposit the vein type au mineralization at the mine is restricted to structurally controlled domains in a low grade calymmian ca 1500 1450 ma metasedimentary sequence that also hosts syngenetic au mineralization two main auriferous quartz vein systems are present i nw trending subvertical extensional veins and ii ne trending subvertical veins parallel to the axial surface of tight folds the mineralized veins are adjacent to a major dextral transcurrent fault zone and their structural relationships indicate that this fault is severely misoriented for frictional reactivation the nw trending veins present a fluid inclusion assemblage dominated by co 2 n 2 ch 4 inclusions h 2 o co 2 n 2 ch 4 nacl cacl 2 inclusions and h 2 o nacl cacl 2 inclusions both with highly variable salinities 0 5 to 52 wt nacl equivalent while the ne trending veins are dominated by h 2 o co 2 n 2 ch 4 nacl cacl 2 and h 2 o nacl cacl 2 inclusions also of highly variable salinities 1 to 45 wt nacl equivalent the entrapment of fluids occurred at temperatures between 225 and 240 c in the nw trending veins and at approximately 208 c in the ne trending veins involving processes of fluid immiscibility and mixing between fluids of contrasting compositions the nw trending extensional veins were formed predominantly under pressure fluctuating between near lithostatic and strongly supralithostatic conditions 100 250 mpa during pre seismic failure stages the ne trending veins precipitated predominantly under subhydrostatic to lithostatic pressure conditions 10 150 mpa following the discharge of fluids from different reservoirs along the ruptured zone after earthquake rupture stages the hydrothermal fluids were probably enriched with gold through interactions with the host rocks and its precipitation is attributed to changes in physicochemical properties due to fluid immiscibility and mixing between fluids of highly contrasting salinities as a consequence of cyclic fluctuations in the values of fluid pressure and tectonic stresses accompanying episodes of seismogenic fault activity

neoproterozoic crustal accretion in central brazil recent geochronological studies have demonstrated the existence of several neoproterozoic orthogneiss and metavolcanic are suites ca 900 to 600 ma in the southern part of the tocantins province a major neoproterozoic orogenic area in central brazil exposed between the amazon and sao francisco cratons nd and sr isotopic characteristics of these metamorphic suites are primitive initial 87 sr 87 sr ratios vary from 0 7024 to 0 7042 and initial nd values are positive varying between 0 2 and 6 9 the most primitive initial sr and nd isotopic compositions are very similar to model depleted mantle compositions at the time of formation of the original magmas the mantle like characteristics of these are suites in western goias contradict previous ensialic evolution models for the tocantins province and reveal that crustal accretion processes were important in large areas of central brazil during neoproterozoic time

the compositional limits of fluid immiscibility in the system h2onaclco2 as determined with the use of synthetic fluid inclusions in conjunction with mass spectrometry abstract the compositional limits of fluid immiscibility in the system nacl h2o co2 were investigated from 500 to 700 c at pressures of 1 2 and 3 kbar synthetic fluid inclusions formed in quartz prisms were equilibrated with high temperature high pressure fluids in hydrothermal pressure vessels the inclusions were analyzed optically by mass spectrometry and by microthermometry the fields of immiscibility were defined as a function of temperature and pressure mass spectrometry was used to validate the existence of the immiscible fluids and to determine the co 2 h 2 o ratios of the two coexisting phases microthermometry i e the measurement of the melting temperature of solid sodium chloride was used in conjunction with the results of the mass spectrometry measurements to define the tie lines within the two phase fields isochores and the location of a portion of the isopleth were determined for composition nacl8 9 h2o76 1 co215 0

evolution of polycyclic basement complexes in the aracuai orogen based on u pb shrimp data implications for brazil africa links in paleoproterozoic time paleoproterozoic basement of the aracuaorogen is composed of amphibolite and granulite facies orthogneiss units known as mantiqueira and juiz de fora complexes six u pb shrimp crystallization ages for the mantiqueira complex range from 2137 19 to 2041 7 ma studied samples are characterized by the abundance of inherited archean zircon grains tdm model ages ranging from 2 9 to 3 2 ga and strongly negative end t 9t o 13 gneiss protholits were mainly generated by partial melting of older continental material and the mantiqueira complex is related to active margin and syn collisional magmatism high grade gneiss samples of the juiz de fora complex yields crystallization ages of 2119 16 and 2084 13 and inherited zircon grains are absent this plutonic unit much probably evolved within an oceanic magmatic arc setting or on a very stretched continental crust the mantiqueira and juiz de fora complexes together with the kimezian basement of the west congo belt were parts of a paleoproterozoic orogenic system disrupted and deeply reworked during the evolution of the aracuacongo orogen neoproterozoic metamorphic overprint is dated at ca 590 574 ma 2007 elsevier b v all rights reserved

partitioning of f between h2o and co2 fluids and topaz rhyolite melt implications for mineralizing magmatic hydrothermal fluids in f rich granitic systems fluid melt distribution coefficients for f have been determined in experiments conducted with peraluminous topaz rhyolite melts and fluids consisting of h2o and h2o co2 at pressures of 0 5 to 5 kbar temperatures of 775 1000 c and concentrations of f in the melt ranging from 0 5 to 6 9 wt the major element f and cl concentrations of the starting material and run product glasses were determined by electron microprobe and the concentration of f in the fluid was calculated by mass balance the h2o concentrations of some run product glasses were determined by ion microprobe sims the solubility of melt in the fluid phase increases with increasing f in the system the solubility of h2o in the melt is independent of the f concentration of the system with up to 6 3 wt f in the melt no evidence of immiscible silica and fluoriderich liquids was detected in the hydrous but water undersaturated starting material glasses 8 5 wt f in melt or in the water saturated run product glasses f concentrates in topaz rhyolite melts relative to coexisting fluids at most conditions studied however df wt f in fluid wt f in melt increases strongly with increasing f in the system maximum values of df in this study are significantly larger than those previously reported in the literature linear extrapolation of the data suggests that df is greater than one for water saturated peraluminous granitic melts containing 8 wt f at 800 c and 2 kbar df increases as temperature and as h2o h2o co2 of the fluid increase for topaz rhyolite melts containing 1 wt f and with h2o rich fluids df is independent of changes in pressure from 2 to 5 kbar at 800 c for melts containing 1 wt f and in equilibrium with co2 bearing fluids the concentrations of f in fluid increases with increasing pressure f and lithophile element enriched granites may evolve to compositions containing extreme concentrations of f during the final stages of crystallization if f in the melt exceeds 8 wt df is greater than one and the associated magmatic hydrothermal fluid contains 4 molal f such f enriched fluids may be important in the mass transport of ore constituents i e f mo w sn li be rb cs u th nb ta and b from the magma

dynamical structure and turbulence in cirrus clouds aircraft observations during fire abstract aircraft data collected during the first international satellite cloud climatology project regional experiment fire i are used to examine dynamical processes operating in cirrus cloud systems observed on 19 and 28 october 1986 measurements from lagrangian spiral soundings and constant altitude flight legs are analyzed comparisons are made with observations in clear air each cirrus case contained a statically stable layer a conditionally unstable or neutrally stratified layer ice pseudoadiabatic in which convection was prevalent and a neutral layer in which convection was intermittent the analysis indicates that a mixture of phenomena occurred including small scale convective cells gravity waves 2 9 km quasi two dimensional waves 10 20 km and larger two dimensional mesoscale waves 100 km the intermediate scale waves observed both in clear air and in the cloud systems likely played an important role in the development of the cloud systems given the magnitude of the associ

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

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

sulfide and platinum mineralization in the merensky reef evidence from hydrous silicates and fluid inclusions the base metal sulfides of the merensky reef are associated with hydrous silicates and intense deuteric hydrous alteration of cumulus and postcumulus silicates biotite and phlogopite crystallized in the vicinity of sulfides from a volatile enriched highly fractionated intercumulus melt amphibole chlorite and talc are later alteration phases of cumulus pyroxene and intercumulus plagioclase biotite is often accompanied by zircon rutile and quartz accessory quartz hosts a complex suite of h2o nacl cacl2 co2 ch4 fluid inclusions which have thus far not been described from the merensky reef the earliest fluid inclusion compositions are nacl h2o with less than 10 vol water co2 coexisting with a halite daughter crystal and brine and polyphase inclusions with up to six daughter and accidental phases and high contents of divalent cations the maximum trapping temperature is around 730 c at 4 to 5 kb pressure later inclusion generations are h2o nacl co2 h2o and pure co2 and ch4 the presence of cl rich fluids during the intercumulus stage of the crystallizing merensky reef is directly related to the mode of sulfide precipitation prior to sulfide unmixing in a hydrous magma sulfur is likely to be present as h2s sulfur saturation causes reaction of h2s with oxides of the silicate melt to form a sulfide melt plus water during reaction the magma is enriched in water until a separate fluid unmixes it carries all compounds with high fluid melt partition coefficients as well as metals capable of forming oh and cl complexes precious metals are assumed to have fractionated into the cl rich fluid as cl complexes rather than being dissolved in the sulfide melt during the cooling evolution of the fluid the precious elements precipitate around the periphery of sulfide melt droplets the model proposed explains the distribution pattern of platinum group minerals in the merensky reef better than any orthomagmatic mineralization concept offered so far

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids

partitioning of lithophile trace elements between h 2 o and h 2 o co 2 fluids and topaz rhyolite melt experiments have been conducted with h 2 o and h 2 o co 2 bearing fluids and melts of a cl f and lithophile trace element enriched vitrophyre associated with topaz rhyolite from spor mountain utah the starting material is mildly peraluminous and contains 1 25 wt percent f and 1 500 ppm cl the experiments were conducted with f sub o 2 controlled near ni nio at pressures of 0 5 to 4 kbars and at temperatures of 770 degrees to 950 degrees c fluid melt trace element distribution coefficients d i were calculated for li be b rb sr y zr nb cs ba ce th and u after ion microprobe analysis of starting material and run product glasses the concentration of element i in the fluid was calculated by mass balance and the fluid melt distribution coefficient d i was calculated as ppm by weight of i in fluid ppm by weight of i in melt the partitioning of li rb sr y nb cs and ce between aqueous fluids and melts of topaz rhyolite composition depends strongly on temperature and pressure at 0 5 kbars li rb sr y nb cs and ce concentrate in the fluid at temperatures or 900 degrees c at 2 kbars this same group of lithophile elements except for sr concentrate in the fluid at t or 900 degrees c be b and ba partition in favor of the melt at 0 5 and 2 kbars and at all temperatures of this study in the presence of co 2 free aqueous fluids at 4 kbars and at temperatures of 770 degrees to 950 degrees c all lithophile elements partition in favor of the melt this behavior for lithophile elements mimics that of published data on the partitioning of pb and zn between rhyolitic melts and cl bearing fluids previous studies have demonstrated an equivalent effect of pressure on the distribution of chalcophile trace elements between granitic melts and cl bearing aqueous fluids fluid melt distribution coefficients for the lithophile trace elements are significantly smaller for topaz rhyolite melts in equilibrium with mixed co 2 h 2 o fluids than for topaz rhyolite melts plus co 2 free aqueous fluids there is no evidence for co 2 complexing with the lithophile trace elements at pressures 6 m the data imply that the alkali elements m dissolve into the fluid as mcl 0 complexes and that ce dissolves into the fluid as a cecl 0 3 complex water saturated magmas of topaz rhyolite composition may become differentiated with respect to li cs and rb or ce y and nb if an aqueous fluid phase is evolved and moves through the magma under the influence of a temperature gradient that has a maximum temperature of at least 850 degrees to 900 degrees c

high density co2 n2 inclusions in eclogite facies metasediments of the munchberg gneiss complex se germany the eclogite facies metasedimentary rocks in the munchberg gneiss complex t 630 30 c p 17 24 kbar locally contain co2 n2 rich fluid inclusions of extremely low molar volumes 32 cm3 mol in quartz these fluid compositions are mainly found in rocks intercalated with calcsilicate bands densities were determined from low temperature phase transitions like stable or metastable homogenization l v l partial homogenization s l v s l and the transition s l l l liquid v vapour s solid the high fluid densities are in agreement with eclogite facies pressure and temperature and subsequent amphibolite facies co2 n2 inclusions were not observed in adjacent eclogites nor in non calcareous metasediments these rock types contain predominantly h2o rich inclusions correlating with amphibolite facies conditions the variation of fluid composition with lithological differences indicates local fluid gradients and speaks against a pervasive fluid flow during eclogite facies metamorphism

gravity wave momentum flux in the lower stratosphere over convection this work describes a method for estimating vertical fluxes of horizontal momentum carried by short horizontal scale gravity waves lambda sub x 10 100 km using aircraft measured winds in the lower stratosphere we utilize in situ wind vector and pressure altitude measurements provided by the meteorological measurement system mms on board the er 2 aircraft to compute the momentum flux vectors at the flight level above deep convection during the tropical experiment of the stratosphere troposphere exchange project step tropical data from flight 9 are presented here for illustration the vertical flux of horizontal momentum these observations points in opposite directions on either side of the location of a strong convective updraft in the cloud shield this property of internal gravity waves propagating from a central source compares favorably with previously described model results

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

granites and the geodynamic history of the neoproterozoic brasilia belt central brazil a review abstract recent field and geochronological studies have demonstrated the importance of granitic magmatism in the evolution of the neoproterozoic brasilia belt in central brazil this is an orogenic belt developed in response to the convergence between the amazon sao francisco congo and parana continental blocks the presence of neoproterozoic juvenile arc rocks and syn collisional peraluminous granites challenged previous intracontinental evolution models for the belt the granitoid intrusions reviewed in this paper record the different stages of evolution of the orogen and their field and isotopic characteristics can be used to reconstruct the tectonic history of the belt the main field and isotopic characteristics of four granite suites associated with the brasilia belt are reviewed i 1 77 1 58 ga old rift related a type granite intrusions ii ca 0 8 0 7 syn collisional granitoids iii arc metatonalites and metagranodiorites ca 0 9 to 0 63 ga and iv bimodal post orogenic suite ranging in age from ca 0 59 to 0 48 ga these rocks suggest that during most of the neoproterozoic the western margin of the sao francisco continent faced a large oceanic basin where subduction and oceanic lithosphere consumption started at ca 0 9 ga roughly coeval with the initial stages of the break up of rodinia final ocean closure happened at ca 0 63 0 60 ga with crustal thickening uplift and erosion post orogenic extension related magmatism took place between ca 0 6 and 0 5 ga and was partially contemporaneous with the deposition of the paraguay and tucavaca sedimentary successions resulting from the rifting event related to the break up of laurentia from southwestern gondwana