modeling of the transport and deposition of tungsten in the scheelite bearing calc silicate gneisses of the montagne noire france scheelite bearing calc silicate gneisses csg oceur in the montagne noire within a series of dominant micaschists detailed petrographical and mineralogical studies reveal three successive stages of metamorphism and hydrothermal alteration 1 stage 1 a regional metamorphism at 550 c and 4 5 kb where no mineralization is formed 2 stage 2a a hydrothermal alteration at 500 to 450 c and 4 to 3 kb which is characterized by an intense sericitization of feldpars and deposition of sn in sn bearing cale silicates and 3 stage 2b a hydrothermal alteration characterized by the crystallization of idocrasegrossular in csg with concomittant precipitation of scheelite tungsten was transported through the micaschist environment and deposited as scheelite only in the csg of stage 2b at relatively low pressures to characterize the mechanism of tungsten transport tungsten speciation at high p t and scheelite solubility in aqueous solations buffered by the csg and by the micaschists assemblages were calculated it was found that h2wo 0 4 hwo 4 and wo 2 4 are the dominant tungsten aqueous species in h2o nacl one molal solutions at 500 c and 2 4 kb calculations also indicate that scheelite deposition is controlled by decreasing pressure and increasing activity of aqueous calcium in this system this is consistent with the petrographical and mineralogical observations the consequences of the presence of volatiles n2 ch4 co2 in the regional fluids were examined by determining the effect of n2 on tungsten speciation and scheelite solubility the addition of n2 up to 10 mol to the mineralizing fluids results in a marked increase in h2wo 0 4 and hwo 4 concentrations relative to wo 2 4 and in a large decrease of scheelite solubility this mechanism favours scheelite precipitation and accounts for the commonly observed association of w and sn deposits with graphitic series generating mixed volatiles fluids

analysis and simulation of local and regional conditions for the rainfall over the lago maggiore target area during map iop 2b the mesoscale alpine programme map operational and research network collected a large variety of measurements during the two days of intensive observing period iop 2b 19 and 20 september 1999 which is one of the most intense rainfall episodes during the special observing period over the lago maggiore area the synoptic situation is a typical one of a southerly flow and associated convection over alpine orography simulations with the non hydrostatic meso nh model are used to describe the rainfall conditions and are successfully validated at the different scales allowed by the map data the two types of pre frontal orographically triggered convective episodes are described 1 sporadic and shallow convection occurs over the coastal mountains and propagates over the po valley the chronology and the intensity of these convective episodes are driven by two main features the low level humidity anomalies and the middle troposphere dry anomaly present over the mediterranean sea 2 the lago maggiore orographic convection has a very long duration and is mainly controlled by both the intensity of the easterly low level wind in the north part of the po valley and the upper level clouds of the cold front the different origins of the air masses transported by this easterly barrier wind and the associated local circulations are detailed copyright 2003 royal meteorological society

evidence for aqueous liquid liquid immiscibility in highly evolved tin bearing granites mount pleasant new brunswick canada abstract three distinct types of fluid inclusions i e liquid vapor lv liquid vapor solid lvs and v only co exist within a single primary fluid inclusion assemblage in fluorite crystals that formed prior to and in close association with cassiterite mineralization in an assemblage comprising fluorite arsenopyrite topaz cassiterite in the sn w mo deposit of the north zone mount pleasant new brunswick the mineral assemblage occurs in vugs with late quartz and chlorite filling the remainder of the open space solid bearing inclusions contain up to eight optically different solids which are estimated to occupy up to approximately 70 vol of the fluid inclusions in a given fluid inclusion assemblage each type of fluid inclusion shows consistent l v or l v s phase ratios the results of microthermometric analyses show that lv inclusions have low salinities that vary from 0 to 10 wt nacl eq and homogenization temperatures that vary from 91 to 250 c within a given assemblage the ranges of salinity and homogenization temperatures of lv inclusions are even less in contrast co existing lvs inclusions are highly saline with salinities ranging from 36 to 40 wt nacl eq and have much higher homogenization temperatures that vary from 425 c to 600 c the upper limit of the microthermometric stage the salinity and homogenization temperature ranges of lvs inclusions show a limited range for a given assemblage the solids in lvs inclusions are interpreted as daughter phases due to consistent phase ratios in lvs fluid inclusions and because during heating experiments all solid phases melted prior to liquid vapor homogenization the consistency of phase ratios and the results of microthermometric analysis among lv or among lvs inclusions show that these inclusions were not formed through necking down of larger inclusions in addition the absence of sweat halos and re entrants rules out water loss as a possible mechanism for producing these coexisting fluid inclusions fluid inclusions of highly contrasting salinities and homogenization temperatures are therefore interpreted to be the result of trapping from two immiscible aqueous liquids it is unknown whether the two liquids exsolved from one single aqueous fluid or have different origins but consideration of the nature of inclusion assemblages in samples from other parts of the system suggest the latter topaz and cassiterite within the same mineral assemblage as well as late quartz contain lv fluid inclusion assemblages with microthermometric behaviors that are similar to the lv type inclusions in coexisting fluorite hosted lv and lvs inclusions suggesting that cassiterite deposited from the low salinity and temperature fluid

genesis of the xiaolonghe quartz vein type sn deposit sw china insights from cathodoluminescence textures and trace elements of quartz fluid inclusions and oxygen isotopes abstract quartz textures revealed by scanning electron microscope cathodoluminescence sem cl images suggest that quartz in the xiaolonghe sn deposit formed in at least three fluid episodes quartz q1 in the pre ore silicification zone has homogeneous texture high cl intensity and high ti content 19 53 ppm fluid inclusions hosted in q1 are vapor rich v1 type and homogenized as supercritical fluid at 570 c quartz q2 in the syn ore topaz cassiterite quartz veins has lower cl intensity and is characterized by euhedral growth zones with lower ti content 1 3 12 ppm fluid inclusions hosted in q2 topaz and cassiterite are liquid rich fluid inclusions of moderate salinity 15 wt nacl equiv l1 type which homogenized at 423 c the post ore quartz q3 closely associated with sericitization of topaz generally crosscuts q2 and has dark cl intensity and much lower ti concentration the upper limits of t p conditions of pre ore and syn ore stage are constrained by the intersection of nacl h2o fluid inclusion isochores and ti in quartz isopleths and the lower limits are based on microthermometry results of fluid inclusions combined with the 18ofluid value 8 3 of q1 it indicates that the pre ore supercritical fluid was directly exsolved from a granitic magma at t 570 600 c and p 0 70 0 77 kbars corresponding to a maximum depth of 2 8 km under lithostatic pressure the syn ore subcritical fluid 8 0 18ofluid 6 3 mixed with some meteoric water was under 423 450 c 0 32 0 45 kbars the transition from the pre ore supercritical fluid to the syn ore subcritical fluid indicates boiling condition probably at 512 c 0 62 kbars which was likely caused by hydraulic fracturing under high pressure both the fluid boiling and fluid mixing contribute to the cassiterite precipitation in xiaolonghe sn deposit in the post ore stage the coexisting s type and v2 type fluid inclusions in q3 indicates a second fluid boiling at 269 c 0 05 kbars which was probably caused by decompression due to rapid denudation of the overlain strata the low salinity 5 5 wt nacl equiv l2 type fluid inclusions hosted in fluorite homogenized at 199 c and

depth of emplacement fluid provenance and metallogeny in granitic terranes a comparison of western thailand with other tin belts the most important tin mineralization in thailand is associated with the late cretaceous to middle tertiary western thai granite belt a variety of deposit types are present in particular pegmatite vein and greisen styles of mineralization a feature common to most of the deposits is that they are associated with granites that were emplaced into the khang krachan group which consists of poorly sorted carbonaceous pelitic metasediments most of the deposits contain low to moderately saline aqueous fluid inclusions and aqueous carbonic inclusions with variable ch4 co2 ratios low salinity aqueous inclusions represent trapped magmatic fluid in at least one case the nong sua pegmatite based on their occurrence as primary inclusions in magmatic garnet aqueous carbonic inclusions are commonly secondary and neither the co2 nor nacl contents of these inclusions decrease in progressively younger inclusions implying that they are not magmatic in origin reduced carbon is depleted in the metasediments adjacent to granites and the d values greisen muscovites are variable but are as low as 134 per mil indicative of fluid interaction with organic graphitic material this suggests that the aqueous carbonic fluid inclusions represent fluids that were produced at least in part during contact metamorphism metasomatism by comparing the western thai belt with other sn w provinces it is evident that there is a strong correlation between fluid composition and pressure in general low to moderately saline aqueous inclusions and aqueous carbonic inclusions are characteristic of mineralization associated with relatively deep plutonic belts mineralized pegmatites are also typically of deeper plutonic belts and pegmatite hosted deposits may contain cassiterite that is magmatic crystallized from granitic melt or is orthomagmatic hydrothermal crystallized from aqueous or aqueous carbonic fluids in origin the magmatic aqueous fluids those that were exsolved from granitic melts are interpreted to have had low salinities as a consequence of the low salinities tin is partitioned in favour of the melt on vapour saturation thus with a high enough degree of fractionation the crystallization of a magmatic cassiterite or different sn phase such as wodginite is inevitable because tin is not partitioned in favour of the vapour phase upon water saturation of the granitic melts it is proposed that relatively deep vein and greisen systems tend to form by remobilization processes in addition many deeper greisen systems are hosted in part by carbonaceous pelitic metasediments and the reduced nature of the metasediments may play a key role in remobilizing tin sub volcanic systems by contrast are characterized by high temperature high salinity fluids owing to the high chlorinity tin is strongly partitioned in favour of the vapour and cassiterite mineralization can form by of orthomagmatic hydrothermal processes similar relationships between the depth of emplacement and fluid composition also appear to apply to other types of granite hosted deposits such as different types of molybdenum deposits

roles of carbonate co2 in the formation of quartz vein wolframite deposits insight from the crystallization experiments of huebnerite in alkali carbonate aqueous solutions in a hydrothermal diamond anvil cell abstract quartz vein type wolframite deposits are a primary type of tungsten deposits traditionally f and cl were considered as important agents in tungsten transportation during ore formation process however ore forming fluids enriched in co2 were commonly observed in natural fluid inclusions associated with quartz vein type wolframite deposits indicating that carbonate or co2 could be important for their formation in this paper we report experiments of the dissolution and crystallization of huebnerite in the mnwo4 li2co3 or na2co3 h2o system using a hydrothermal diamond anvil cell hdac the results showed that mnwo4 dissolved in alkali carbonate aqueous solutions and in some cases in associated carbonate melts during heating and subsequently huebnerite crystallized into needle and column shaped crystals during cooling in situ raman spectra obtained during heating of the experimental charge in the sample chamber of the hdac showed that wo42 was the only tungsten bearing ion detected in the carbonate melt or aqueous solution the dissolution of mnwo4 mainly attributed to the alkaline environment in the alkali carbonate aqueous solution furthermore the weak alkali condition in the carbonate solutions enhanced the crystallization of huebnerite when the temperature and pressure were decreased the experimental results indicate that although the crystallization temperature pressure conditions of huebnerite vary in a wide range conditions lower than approximately 200 mpa and 450 c are not favorable for huebnerite crystallization our experimental results also suggest that the alkali carbonate aqueous solution could serve as a medium for the transport of tungsten in the ore forming process

rare metal pegmatites of wamba central nigeria their formation in relationship to late pan african granites he sn nb ta mineralization of the wamba field central nigeria occurs in muscovite quartz microcline pegmatites which are related to the late orogenic pan african f 550 ma older granites the emplacement of granites and pegmatites was controlled by late pan african shear tectonics the granitoid magmatism was multiphase and has produced peraluminous biotite granite biotite muscovite granite and muscovite granite plutons sodic metasomatism has altered highly evolved granite cupolas and many of the pegmatite dikes the pegmatitic mineralization of predominantly cassiterite is closely associated with albitization chemical data of granites and granitic and pegmatitic muscovites show that rb cs sn nb and ta are enriched during both magmatic and postmagmatic evolution with highest contents of these elements in early muscovites of the albitized and mineralized pegmatites trace element chemistry of the pegmatitic muscovites reveals a chemical zonation of the pegmatite field related to the late orogenic shear system

fluid inclusion study in different types of tin deposits associated with the hercynian granites of western spain most of the spanish sn deposits are closely associated with intrusions of syn and late kinematic hercynian granites a fluid inclusion study using microthermometric raman and crushing test analyses has been made of quartz cassiterite scheelite and calcite from greisens and quartz veins in the following types of deposits a disseminated cassiterite in apogranites golpejas and penouta b stanniferous pegmatites la fregeneda and c quartz veins and stockworks with cassiterite teba cassiterite and wolframite san finx and cassiterite and scheelite la parrilla the homogenization temperatures and physico chemical characteristics of the inclusions indicate three stages of fluid circulation the first stage is characterized by the trapping of complex co2 aqueous h2o nacl co2 ch4 n2 h2s complex co2 co2 ch4 n2 h2s and low salinity aqueous h2o nacl inclusions 10 eq wt nacl at temperatures ranging between 500 and 250 c and pressures below 2000 bar the second stage is represented by low salinity aqueous inclusions 10 eq wt nacl trapped at homogenization temperatures between 300 and 60 c and pressures of 200 bar the third stage is characterized by mixed salt aqueous inclusions h2o nacl kcl cacl2 mgcl2 trapped at homogenization temperatures between 170 and 60 c and low pressures the results obtained by this study indicate that in general with descending temperature the chemical evolution of the mineralizing fluids is such that the fluid inclusions are characterized by a progressive increase in the total density and a progressive decrease in the salinity and the co2 and volatile contents however for the fluids trapped at lower temperatures 100 c the salinity is much higher which is presumably due to the sudden increase in ca2 mg2 na and k salt contents

calculation of oxygen isotope fractionation in metal oxides abstract a theoretical model calculating the thermodynamic isotope factors of oxygen in metal oxides of geochemical interest is presented for temperatures between 0 and 1200 c on the basis of the modified increment method the following order of 18o enrichment is obtained cassiterite rutile magnetite ilmenite ulvospinel hematite uraninite chromite corundum spinel the results are expressed as 103 in a 106 t2 b 103 t c which compare well with existing theoretical experimental and empirical calibrations on quartz oxides and oxides water systems the present calculations enable not only estimation of the oxygen isotope composition of fluids from which the metal oxides were precipitated when independent temperature information is available but can also be applied as oxygen isotope geothermometers to igneous and metamorphic rocks

petrogenesis of tourmaline granites and topaz granites the contribution of experimental data abstract fluorine and boron are generally only minor components of granitic rocks but may be found highly concentrated in certain tourmaline granites and topaz granites up to 1 wt b2o3 and 3 2 wt f respectively studies of various examples of these granite types which occur as small bodies emplaced at shallow levels p lithostatic textural and petrographic data indicate that the tourmaline and topaz granite magmas crystallized at low to moderate temperatures below 700 c and that a fluid phase may have been present during the crystallization interval both granites varieties are peraluminous co up to 5 characterized by the presence of white micas lithium micas or muscovite aluminium silicates and other al rich minerals garnet cordierite boron and fluorine are hosted by tourmaline schorl rich member of the schorl dravite series topaz and mica respectively these granites have low ca fe mg and ti contents each the crystallization of tourmaline granite and topaz granite magmas is discussed using experimental data derived from studies of granitic systems with added boron and fluorine both elements act as a flux enabling boron and fluorine enriched melts to persist to temperatures as low as 650 c at 1 kbar in addition the effect of increasing fluorine content displaces the minimum in q ab or at ph2o 1 kbar toward the albite apex plots of fluorine rich topaz granites coincide with this trend suggesting that the role of fluorine in magmatic processes may have affected the rock composition as well as crystallization temperatures boron rich granites plot near the low ph2o minima in qz ab or suggesting that boron has less of an influence on minimum melt compositions the low temperatures of crystallization permits phases such as muscovite or andalusite topaz and two alkali feldspars to crystallize directly from f and b enriched melts at low pressures in addition the limited available experimental data are used to compare the effects of fluorine and boron on major and trace element distribution during melt vapour interaction

effects of moist froude number and cape on a conditionally unstable flow over a mesoscale mountain ridge abstract in this study idealized simulations are performed for a conditionally unstable flow over a two dimensional mountain ridge in order to investigate the propagation and types of cloud precipitation systems controlled by the unsaturated moist froude number fw and the convective available potential energy cape a two dimensional moist flow regime diagram based on fw and cape is proposed for a conditionally unstable flow passing over a two dimensional mesoscale mountain ridge the characteristics of these flow regimes are 1 regime i flow with an upstream propagating convective system and an early slowly moving convective system over the mountain 2 regime ii flow with a long lasting orographic convective system over the mountain peak upslope or lee slope 3 regime iii flow with an orographic convective or mixed convective and stratiform precipitation system over the mountain and a downstream propagating convective system and 4 regime iv flow with an orographic stratiform precipitatio

small scale rainfall mechanisms for an idealized convective southerly flow over the alps rain producing flows over the south side of the alps are investigated with an idealized high resolution 2 5 km numerical configuration where only three basic ingredients of typical heavy precipitation situations have been retained 1 a uniform and stationary southerly flow far upstream from the alps which drives 2 a conditionally unstable atmosphere towards 3 the real topography of the alps and the surrounding secondary mountains attention is given to small scale mechanisms of rainfall over the po plain and the alpine slopes these are linked with two orographically induced low level wind jets the easterly barrier wind jet along the southern flank of the alps and a south easterly jet formed over the sea along the south western flank of the apennines and continuing over land up to the alps the specific role of the secondary relief upstream from the alps in inducing or influencing these low level flow features and also in triggering organized convection is studied by means of experiments on the sensitivity to topography the idealized configuration also allows the advantages of a convection resolving model for modelling precipitation distributions at the alpine valley scale to be considered copyright 2007 royal meteorological society

formation mechanisms for convection over the ligurian sea during map iop 8 abstract the dynamical impacts of an unusually strong stable layer that developed over the po valley and northern ligurian sea during mesoscale alpine program map intensive observation period 8 iop 8 on the formation of convection over the ligurian sea are explored based on numerically simulated equivalent potential temperature wind vectors and by a trajectory analysis of parcels both beneath and above the stable layer it is shown that the stable layer behaved as a material surface or effective mountain to the airstreams impinging on it from the south additional analyses show that the leading edge of the stable layer was collocated with maxima in upward motion and a strong positive moisture flux hence it was further argued and demonstrated through inspection of soundings upstream of the cold dome and trajectory analyses that lifting by the stable layer enhanced convective activities over the ligurian sea finally processes contributing to the maintenance of the stable layer during iop 8 were

partitioning of sn and w between granitic melt and aqueous fluid abstract hydrothermal granite related sn and w deposits typically show predominance of one metal over the other at the intrusion and deposit scale this separation may reflect contrasting behavior of these elements during late stage magmatic processes in our experimental study we determined fluid melt partition coefficients of sn and w at 750 c 200 mpa as function of the alumina saturation index asi of the melt for nacl kcl hcl fluids two sets of data were obtained one from analysis of fluid inclusions trapped in glass and the other based on analysis of the quenched fluid our data indicate slight partitioning of sn into the melt and at asi of 0 99 1 16 strong partitioning of w into the aqueous fluid the effect of quenching was evident for tungsten which indicates that fluid melt partition coefficients of w reported in the literature are underestimated the contrasting fluid melt partitioning of sn and w implies that hydrothermal sn and w mineralization is rarely cogenetic furthermore contrasting fluid melt partitioning accounts for the separation and zonation of these metals on the deposit scale and the different style of predominant mineralization tin precipitates from the granitic melt as cassiterite or is incorporated in biotite and other minerals later exsolution of hcl bearing magmatic fluids can efficiently mobilize sn from the granite or the wall rock of the intrusion but can transport sn only over relatively short distances due to reaction of the fluid with feldspar greisenization which results in precipitation of cassiterite and formation of tin greisens tungsten is partitioned into the magmatic fluid and will be lost from the intrusion along with this fluid because greisenization reactions do usually not result in tungsten mineralization w can be transported farther away from the intrusion than sn and is deposited in scheelite bearing skarns or upon cooling in quartz wolframite veins

diffusion effects on oxygen isotope temperatures of slowly cooled igneous and metamorphic rocks recently obtained data on oxygen diffusion in feldspars quartz and hornblende permit the prediction of the apparent18o16o temperatures that would be measured in a rock that consisted only of those three minerals and cooled slowly from high temperature the computed temperatures would be based on the differences in the18o16o ratios between coexisting pairs of minerals the present calculation takes into account the diffusion rates for oxygen as a function of temperature the cooling rate of the rock the mineral grain sizes and the mode of the rock for mineral grains 1 mm in radius and a cooling rate of 10 c m y the minimum difference in apparent temperature between quartz feldspar and feldspar hornblende pairs will be 115 c despite the assumption of a normal uneventful slow cooling history to room temperature further the apparent quartz hornblende temperature will range over 30 c 590 620 c depending on the mode of the rock for a cooling rate of 1000 c m y the apparent difference in temperature can be as much as 400 c consequently consistency in temperatures obtained by oxygen isotope analysis should not be expected in most high grade metamorphic rocks or igneous rocks which are cooled slowly departures from the pattern of temperatures obtained in this model would imply a very rapid quench from high temperature or a complex history for the rock for some minerals including hornblende the relation between temperature and the equilibrium fractionation of oxygen isotopes between coexisting phases has been derived from observed relations in natural specimens the choice of the specimens used for such calibrations needs to be re evaluated in light of these findings this may result in a change in the equilibrium equation constants an example from the literature the san jose tonalite baja california mexico was modelled and yields 18o concentrations in the minerals that correspond closely with the measured values this suggests that the model used is appropriate that the rock has had a simple thermal history and that it cooled at 100 200 c m y over the temperature range 800 500 c the set of paleotemperatures obtained for a rock will in general yield neither the mineral closure temperatures nor the formation or crystallization temperatures on the other hand the cooling rate of the rock may be derived from the data this in turn may have important tectonic implications with regard to denudation and uplift rates

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

genesis of the oxidized sn ores in the gejiu district yunnan province sw china abstract the gejiu sn ore district one of the largest sn producing area 300mt 1 wt sn in the world is located in the western margin of the cathaysia block sw china there are five types of sn ores in the gejiu district including greisen skarn veined tourmaline massive sulfide and oxidized among these types of sn ores the genesis of the oxidized sn ores is most controversial such as magmatic hydrothermal origin and sedimentary exhalative sedex or hot water deposition red sea type this paper reports u pb ages fluid inclusions trace elements and h o isotopes of cassiterite from the oxidized sn ores aiming to solve this issue la mc icpms cassiterite u pb dating yielded an age of 86 7 2 8 ma which is accordant with the formation ages 86 ma of granitic intrusions in the gejiu district two types of fluid inclusions in cassiterite from the oxidized sn ores were observed one type is co2 rich inclusions type 1 and the other type is aqueous inclusions type 2 the homogenization temperatures range from 220 to 366 c and the salinities range from 10 9 to 21 wt nacl equiv for the two types of fluid inclusions furthermore fluid inclusions in cassiterite from the oxidized sn ores located at 300 m far away from granitic intrusions have higher temperatures 357 366 c than those located at 500 m 273 330 c hence the ore forming temperatures tend to decrease with the distance far away from the magmatic hydrothermal center the vapor components for the two types of fluid inclusions are co2 and h2o respectively and the liquid phase compositions of them are all h2o the co2 in the ore forming fluids may source from marble by decarbonization this indicates that the precipitation of cassiterite is resulted from fluid immiscible the 18o values of fluid inclusions in cassiterite range from 6 1 to 7 7 and the d values range from 135 to 153 indicating a mixture of magmatic and meteoric waters trace elements show that cassiterite is rich in in rb and u but ba nb and ti are depleted in addition the lower sr 0 4 2 1 ppm and higher sc 35 9 53 7 ppm contents reflect that the formation of cassiterite is related to f rich intermediate acid magma cassiterite has a relatively low total ree contents 2 7 9 2 ppm with negative eu eu 0 14 0 76 and ce ce 0 1 0 6 anomalies indicating that the ore forming environment is oxidized this is consistent with the cassiterite precipitation conditions hence all the evidence supports that the oxidized sn ores are genetically associated with the gejiu granitic magmatism

exploration of some convective regimes over the alpine orography a numerical exploration of several airflow regimes is performed by means of the non hydrostatic model meso nh the alpine orography has been selected together with a uniform conditionally unstable profile extracted from the mesoscale alpine programme database the stationary solution is obtained at the fine scale after three successive simulations using three nested levels 40 10 and 2 5 km the variation of the non dimensional height of the alps leads to the following regimes no convection upstream propagating convection and stationary convection over the alps the last two regimes correspond to regimes i and ii of the chu and lin 2000 study the sensitivity of the convective response to the fine scale orography is found to be more important for regime ii than for regime i moisture budgets confirm the importance of the barrier wind to determine the rain distribution in the centre of the alpine orography for regime ii and away from it for regime i the drying ratio is more influenced by the comparative value of the advective time to a characteristic microphysical time scale than by the orographic forcing itself finally for this sounding the diabatic effects change the critical value of the non dimensional height for the transition between the flow over and flow around configurations copyright 2004 royal meteorological society

phase relations of tourmaline leucogranites and the significance of tourmaline in silicic magmas by means of melting and recrystallization tourmaline seeded experiments phase relations of two natural tourmaline bearing fe rich members of the schorl dravite series leucogranites have been determined between 1 and 3 kbar under h2o saturation with fo2 close to ni nio the presence of tourmaline slightly lowers the solidus temperatures of both samples from 5 to 20 c compared to the corresponding tourmaline free solidus quartz k feldspar and plagioclase phase relations are not significantly dependent on the presence of tourmaline tourmaline is the last major phase to disappear for both samples and a demonstrated liquidus phase exists for one in the recrystallization experiments the compositions of the tourmalines growing from the melt change from more mg rich at high temperatures to more fe rich at lower temperatures the tourmalines are always richer in mg than the melt is but fe and mg are not especially partitioned between crystallizing tourmaline and melt melt compositions do not depart

a hydrogen and oxygen isotope study of the san cristobal mine peru implications of the role of water to rock ratio for the genesis of wolframite deposits oxygen and hydrogen isotope ratios were measured from vein minerals and extracted fluid inclusion waters from the san cristobal wolframite base metal deposit in peru oxygen isotope values for quartz range from 9 8 to 14 4 per mil and for wolframite from 0 6 to 4 6 per mil the calculated delta values at 300 degrees c for water in equilibrium with quartz and wolframite are delta 18 o 2 8 to 7 3 per mil for quartz and 1 4 to 5 4 per mil for wolframite hydrogen isotope values show an overall range of delta d 58 to 148 per mil but the range for any given mineral is much smaller these data are interpreted in light of a model which examines the effect of temperature and water to rock ratio on the isotopic compositions of meteoric waters exchanging with granite in a rock dominated system an isotopically exchanged water becomes depleted in delta 18 o and enriched in delta d as the temperature of exchange decreases when the water to rock ratio is also allowed to vary a wide variety of water compositions is generated the isotopic composition of minerals from san cristobal can be interpreted as the result of deposition from a meteoric water which has undergone isotopic exchange with a granite at 400 degrees c with a water to rock ratio ranging from 0 01 to 0 003 isotopic data taken from two other wolframite deposits pasto bueno landis 1972 and panasquiera kelly and rye 1979 are reinterpreted using the model developed for san cristobal both sets of data are consistent with the hypothesis that wolframite deposits are formed by meteoric waters which have experienced exchange at very low water to rock ratios 0 05 the importance of the low water to rock ratio may be related to the way in which tungsten is leached from a crystallized pluton

volume self diffusion of oxygen in biotite muscovite and phlogopite micas the kinetics of oxygen self diffusion have been measured in natural samples of biotite muscovite and phlogopite micas under hydrothermal conditions using both bulk exchange and profiling analyses all experiments were run at 1000 bars 100 mpa water pressure except those designed to measure water pressure dependence which ranged from 200 to 2000 bars the arrhenius relations obtained for layer parallel diffusive transport in the three micas by bulk exchange experiments fit to an infinite cylinder model are mineral biotite muscovite phlogopite 34 2 39 5 42 3 9 1 10 6 7 7 10 5 1 4 10 4 t c 500 800 512 700 600 900 the results of ion microprobe sims depth profiling perpendicular to the layers parallel to c axis yield diffusion coefficients 3 to 4 orders of magnitude lower than for transport parallel to the layers a single layer parallel step profiling experiment yields a diffusion coefficient identical within uncertainty to those obtained from bulk exchange experiments a slight dependence of diffusion rate on water pressure may obtain in phlogopite however the difference is approximately within the uncertainty of the measurement diffusion rates are similar within about a half an order of magnitude for a range of biotite composition from annite4 to annite63 as well as for muscovite comparison of oxygen diffusion rates in biotite from this study with ar k and rb diffusion from published data supports the idea that water is the oxygen bearing species in hydrothermal diffusion experiments the implication of these results for natural systems is that the micas especially biotite will continue to exchange oxygen isotopes via volume diffusion down to temperatures as low as 300 c the rapid diffusion kinetics may explain biotite oxygen isotope disequilibrium which is commonly observed even in rocks where other mineral phases preserve equilibrium compositions full size table table options view in workspace download as csv

fluid regime and ore formation in the tungsten yttrium deposits of kyzyltau mongolian altai evidence for fluid variability in tungsten tin ore systems abstract the kyzyltau ore field is located in the northern part of the mongolian altai mountains w y be mo mineralization occurs in veins and stockworks in granites felsic volcanics basaltic flows and conglomerates the main ore minerals in the veins are wolframite fluorite beryl and minor molybdenite inclusions in hydrothermal quartz fluorite and beryl from veins as well as in magmatic quartz in vein hosting granites of the ulaan uul buraat uul and tsunkheg deposits were investigated using microthermometry and laser raman spectroscopy pseudosecondary primary inclusions in the kyzyltau ore veins are predominantly liquid rich aqueous inclusions containing variable amounts of co 2 as the main gas component and showing n 2 ch 4 ratios 1 secondary inclusions contain no or only trace concentrations of gases as indicated by clathrate melting the t h values of pseudosecondary primary inclusions in veins are between 180 and 433 c fluid inclusion data indicate that phase separation processes leading to fluid immiscibility occurred in vuggy quartz ii and green fluorite ii in the ulaan uul and buraat uul ore veins phase separation pressures of 100 350 bars were estimated fluorite i from the kyzyltau ore field shows a strong enrichment of hree and a strong negative eu anomaly common for rare metal bearing ore systems fluorite ii from buraat uul and tsunkheg is characterized by a change in the incorporation of rare earth elements ree with decreasing hree contents and a decreasing eu anomaly the ree distribution patterns in fluorite ii from ulaan uul remained unchanged compared with fluorite i despite a strong increase in the total ree content a review of the literature shows that from high temperature fe rich k dominated brines cassiterite ores can precipitate in quartz veins together with fe chlorite and fe tourmaline bolivian type if phase separation of a gas rich low salinity and fe rich fluid occurs cassiterite wolframite ores may be deposited cornwall devon type the deposits of kyzyltau are characterized by low fe alteration assemblages a predominance of sodium over potassium high contents of ree and y and a lack of extended tin mineralization despite the tin potential of the ore systems fluid inclusion data as well as geochemical and geological indications suggest formation of the tungsten deposits near the tops of li f rich sub volcanic intrusions we interpret the ph of the mineralizing fluid to be the main factor controlling wolframite precipitation in the kyzyltau ore field fluid wall rock interactions a lowering of the temperature and unmixing processes in the ore fluid generated contributions to neutralization and buffering of the acid co 2 bearing fluid into a ph range where tungstates were precipitated it can be inferred that formation of tungsten ores without precipitation of extended tin mineralization is possible in deposits characterized by high potential tin and tungsten according to this inference tin mineralization may be found in a more favourable setting in the vicinity of the kyzyltau deposits

fluid inclusion microthermometry in be ta li sn bearing pegmatites from the borborema province northeast brazil abstract fluid inclusions in be ta li sn bearing pegmatites have been reported in the literature as hypersaline aqueous brines or low salinity aqueous or aqueous carbonic fluids the evolution paths of volatile fluids in equilibrium with the different crystallizing phases of rare element pegmatites do not seem to be unique the aim of this work is to contribute to this discussion on the basis of fluid inclusion information from the borborema pegmatite province bpp in northeast brazil some well known heterogeneous be ta li sn mineralized pegmatites of this province were systematically sampled along cross sections with the purpose of studying the fluid inclusions in the different pegmatite zones i muscovite rich contact zone ii homogeneous or graphic pegmatite iii blocky feldspar zone and iv quartz core the observed fluid inclusions mainly in quartz were almost always secondary or pseudosecondary grouped along healed fractures with random orientation even some trails paralleling quartz grain limits were not undoubtedly primary almost all these fluid inclusions were filled with low salinity aqueous or aqueous carbonic fluids primary inclusions were recognized only in some well formed crystals from druses with erratic distribution in the pegmatites microthermometric data from these samples confirm that the various crystallizing phases of the pegmatites were in equilibrium with low salinity aqueous or aqueous carbonic fluids with insignificant n 2 or ch 4 contents with frequent accidentally trapped solids the various types of primary inclusions found in these crystals compare well with the types of secondary inclusions of the samples from the systematic cross sections the relative age of the crystals hosting primary fluid inclusions the relative age of primary inclusion types in successive crystal growth zones the relative age of secondary fluid inclusion trails and the corresponding microthermometric data allowed to establish the most probable evolution of the fluid characteristics during pegmatite crystallization an early low salinity aqueous carbonic fluid with co 2 contents of 20 mol was present during the crystallization of early minerals such as garnet and tourmaline of the border zone and graphic quartz beryl manganotantalite and blue tourmaline of zones ii and iii the end of zone iii crystallization occurred in the presence of a low salinity aqueous fluid with very low co 2 contents as indicated by inclusions in the smoky core of quartz crystals at the limit between zones iii and iv later aqueous fluids barren in co 2 and with salinities increasing from 5 to 20 coexisted with the formation of the pegmatite nucleus and replacement bodies as indicated by inclusions in the border of these crystals and in euclase the estimated trapping conditions of 3 5 kbar and 580 c for the earliest inclusion types agree with the regional metamorphic conditions and with the known liquidus conditions of rare element bearing pegmatite crystallization the trapping conditions of inclusions in euclase and coexisting quartz crystal rims in the pegmatitic core at 3 5 kbar and 400 c are slightly below the conditions admitted for the solidus of rare element pegmatites and indicate an isobaric cooling during pegmatite crystallization

mechanisms of intense alpine rainfall abstract numerical studies by the authors and others of the 1994 piedmont flood show that the orographically modified flow was a critical element for the production of extraordinary rainfall to uncover the precise mechanism of orographic rainfall occurring in full physics mm5 simulations of the 1994 piedmont flood the authors carried out simulations with the same real data initial and boundary conditions but with the real orography replaced by an idealized one with excellent agreement between real and idealized orography on the rainfall rate versus time in the piedmont area analysis of the idealized orography simulation provides a clear picture of the model s mechanism of orographically induced rainfall as noted in previous studies of the 1994 piedmont case a moist saturated airflow has a reduced effective static stability and tends to flow over the mountains while an unsaturated airstream is stable and tries to flow around toward the left in the northern hemisphere in the 1994 piedmont case t

extrusion vs duplexing models of himalayan mountain building 2 the south tibet detachment at the dadeldhura klippe abstract himalayan mountain building has been dominantly explained by two types of models extrusion and duplexing to elucidate possible roles of these mechanisms during emplacement of the himalayan crystalline core we investigate an area speculated to contain the southern leading edge of the crystalline core the northeastern margin of the dadeldhura klippe western nepal we found an 700 m thick primarily top to the north shear zone within the klippe we term this as the tila shear zone the shear zone occurs within a right way up metamorphic field gradient and separates footwall gneiss from hanging wall schist similarly deformation temperatures estimated from quartz and feldspar microstructures and quartz c axis fabrics indicate a right way up thermal gradient of 77 189 c km u pb zircon dating of post kinematic leucogranite dikes suggests that ductile shearing along the tila shear zone occurred prior to 17 14 ma we correlate the tila shear zone to the south tibet detachment std on the basis of consistent structural fabrics shear sense lithologies metamorphism and deformation timing this interpretation in combination with regional constraints indicates southwards increasing proximity of the std tila shear zone and the main central thrust mct these two shear zones are separated by 3 km of structural section in the northern portion of our study area and become close to within 1 km of separation in the southern portion interpolation suggests that the std tila shear zone and mct merge 15 10 km southwest of our study area the increasing to south proximity and potential merger of the two shear zones suggest that the std formed as a backthrust from the mct this interpretation contrasts with the long standing normal fault interpretation of the std because the std and mct bound the himalayan crystalline core these findings document crystalline core emplacement at depth via tectonic wedging this kinematic evolution is consistent with duplexing but not extrusion to the surface

the evolution of pegmatite hosted sn w mineralization at nong sua thailand evidence from fluid inclusions and stable isotopes abstract the nong sua aplite pergmatite complex contains two dominant styles of sn w ta nb mineralization cassiterite nb ta ti oxide minerals are disseminated in the pegmatite and cassiterite and wolframite are hosted by quartz tourmaline veins which are contained solely within aplite the orthomagmatic fluid at nong sua is preserved as primary fluid inclusions in the cores of magmatic garnet crystals that have high tin concentrations garnet cores without fluid inclusions do not contain elevated tin concentrations these fluid inclusions have a composition of 3 wt nacl eq the low salinity suggests that at vapor saturation tin was partitioned in favour of the melt which allowed cassiterite to initially crystallize directly from the melt primary pseudosecondary and secondary fluid inclusions in cassiterite tourmaline and quartz record three component mixing of the orthomagmatic fluid with high salinity aqueous and with co2 rich fluids the orthomagmatic water is interpreted to have had 18 o value of 8 7 to 9 9 per mil and a d value of 72 to 78 per mil from 18o analyses of muscovite and quartz and d of muscovite the 18o composition of muscovite decreased from 10 1 to 8 0 per mil and d increased from 106 to 85 per mil from the magmatic to the hydrothermal stages of pegmatite evolution these changes are consistent with an influx of metamorphic fluids or evolved meteoric waters we consider that the saturation of the melt with vapor caused the pressure in the pegmatite to rise to approximately 3 8 kbar at a temperature of 650 c fluid overpressure caused the aplite to fracture and veins to form from fluids which migrated into the fracture induced low pressure zones this event can be modeled by an isothermal decompression to 2 7 kbar cassiterite deposition was probably controlled by increasing fo2 whereas wolframite deposition resulted from the mixing of w rich with fe mn rich fluids in both cases decompression cooling and addition of volatiles may have also contributed to mineralization

the impact of upstream blocking drainage flow and the geostrophic pressure gradient on the persistence of cold air pools idealized numerical simulations are performed to investigate dynamical mechanisms affecting the persistence of cold air pools in basins and valleys the first orography type considered is a shallow elongated basin located upstream of a mountain ridge for sensitivity tests the mountain ridge is removed the second type is a basin embedded in a plateau like mountain ridge in part of the simulations this basin has an outflow towards the lee side plain so as to assess the impact of the drainage flow the large scale flow is taken to be in geostrophic balance in the standard setting it is perpendicular to the basin and the ridge the main effect of a large scale pressure gradient is to induce a circulation within a cold air pool until the upper boundary of the cold pool is inclined such as to compensate for the ambient pressure gradient the cold air accumulates where the ambient pressure is lowest for a shallow basin this means that part of the cold air may be lost due to advection out of the basin the upstream influence of a mountain ridge in the lee of a shallow basin is found to be twofold it tends to deflect the low level flow towards the lower pressure leading to an additional ridge parallel force on the cold air pool on the other hand the absolute wind speed is reduced diminishing the turbulent mixing near the top of the cold pool the simulations show that the first effect prevails for ridge normal flow while second effect may dominate for other flow directions drainage flow out of a valley is found to be very important as it promotes the penetration of warm air into valleys very effectively it may cause a cold pool in a deep valley to disappear more quickly than a cold pool in a shallow basin sensitivity tests show that the persistence of a cold pool depends on its depth on its vertically integrated heat deficit and on the maximum heat deficit at the bottom of the cold pool copyright 2003 royal meteorological society

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

volatile production during contact metamorphism the role of organic matter in pelites elemental analyses of palaeozoic mudrocks from south cornwall indicate the presence of 0 04 0 74 wt carbon primarily in an elemental and or organic form in addition to 0 04 0 10 wt nitrogen as nh 4 in micas and in organic material both elements are depleted in samples from the lithologically homogeneous mylor slate formation next to the tregonning granite an offshoot of the cornubian batholith the depletions are due to an h 2 o co 2 n 2 ch 4 fluid formed during contact metamorphic devolatilization of the pelitic country rocks fluids of this type have been reported from a number of hercynian sn w provinces and may play an important role in mobilizing metals in pelitic rocks during granite related contact metamorphism and hence in the metallogenic evolution of such regions

orographic effects on rainfall in map cases iop 2b and iop 8 although the large scale flow was similar important differences in mesoscale atmospheric structure made the difference between moderately intense rain in intensive observing period iop 2b and relatively light rain in iop 8 in the lago maggiore target area lmta this conclusion is supported here through analysis of data from and numerical simulations of these two cases analysis of the large scale data shows that there was in both cases a moist tongue of southerly flow moving from the west to the east of the alpine south side mesoscale data analysis and numerical simulations suggest that the most important difference between the two cases was the presence of a cold stable air mass in the po valley in iop 8 which persisted through the period in which the large scale moist tongue was progressing eastward and prevented the most humid air from reaching the lmta another difference contributing to the greater rainfall in the lmta in iop 2b was the development of conditional instability with associated convective rain due to the effect of the alps on the eastward passage of the moist tongue in iop 8 the atmosphere remained locally stable throughout the period copyright 2003 royal meteorological society

fluid inclusions in the system h2o ch4 nacl co2 from metasomatic tourmaline within the border unit of the tanco zoned granitic pegmatite s e manitoba abstract fluid inclusions from the tourmaline phase of alteration of the footwall amphibolite from the tanco zoned granitic pegmatite lie in the system h2o ch4 nacl co2 these inclusions contain a liquid and vapour phase at room temperature and develop a second liquid phase on cooling in the range 77 to 95 c the second liquid and the vapour are methane isochores for inclusions showing vapour phase ch4 homogenisation were constructed from the equations of jacobs and kerrick 1981 the intersections of these isochores with the univariant melting curves for methane clathrate hydrates give estimates of salinity for the inclusions of between 7 and 10 equivalent wt nacl which are lower than those derived from measurement of the depression of the melting point of ice a result consistent with salt exclusion by clathrate the bulk composition of the fluid is estimated to be 91 mol h2o 6 mol ch4 2 equiv mol nacl and calculation of fo2 from the bulk inclusion composition gives values near wi at these conditions which is unreasonably low for fluids derived from the pegmatite which were probably between qfm and hm the metasomatic fluids may have resulted from fluid mixing in the wall rock immediately adjacent to the pegmatite the fluid derived from the pegmatite a h2o co2 fluid introduced the b necessary to form tourmaline in the amphibolite on the other hand it is suggested that ch4 h2o may have been derived from a metamorphic fluid which formed in equilibrium with graphite at lower oxygen fugacities at 400 600 c and which was present in the wall rock at the time of pegmatite emplacement supporting evidence is provided by pegmatite wall zone fluids with higher ch4 5 equiv mol in co2 than the bulk of the pegmatite h2o co2 fluids 0 8 mol in co2 suggesting marginal fluid contamination

can economic porphyry copper mineralization be generated by a typical calc alkaline melt numerical simulation of chlorine and copper partitioning between a crystallizing melt and exsolving aqueous fluids indicates that typical calc alkaline magmas contain sufficient copper chlorine and water to produce economic porphyry copper mineralization neither an elevated copper content in the magma nor an additional large volume of magma are required to provide metals or volatiles the most important variables that determine the volume of melt necessary to produce sufficient copper are the degree of compatible behavior displayed by copper the ratio of initial water in the melt to the water saturation level and the initial chlorine water ratio of the melt the absolute values for initial water in the melt and water content at saturation are relatively unimportant in determining the required melt volume the bulk salinity of the exsolved fluid may vary from 2 0 wt nacl to saturation levels 84 wt nacl at 700 c indicating that boiling is not necessary to produce high salinity brines at appropriate p t xnacl conditions the magmatic aqueous fluid separates into a saline liquid which transports most of the copper and a low salinity vapor the salinities of the two immiscible phases are governed by the p t conditions while the bulk fluid salinity determines the mass fractions of liquid and vapor formed pressure quenching causes rapid crystallization of the aplitic groundmass in porphyritic rocks associated with copper mineralization and significantly reduces the amount of chlorine and copper partitioning to the aqueous fluid this results in abrupt and possibly large reductions in fluid salinity and causes copper to become concentrated in the melt as copper is transported from the melt by the earliest exsolving fluids in deep 2 0 kbar systems and by late exsolving fluids in shallow 0 5 kbar systems the relative timing of pressure quenching aplite formation and fluid transport of copper from the melt can vary significantly in systems produced under different confining pressures model results incorporating petrologic constraints determined for yerington nevada are in good agreement with observed mineralization