major types and time space distribution of mesozoic ore deposits in south china and their geodynamic settings the ore deposits of the mesozoic age in south china can be divided into three groups each with different metal associations and spatial distributions and each related to major magmatic events the first event occurred in the late triassic 230 210 ma the second in the mid late jurassic 170 150 ma and the third in the early mid cretaceous 120 80 ma the late triassic magmatic event and associated mineralization is characterized by peraluminous granite related w sn nb ta mineral deposits the triassic ore deposits are considerably disturbed or overprinted by the later jurassic and cretaceous tectono thermal episodes the mid late jurassic magmatic and mineralization events consist of 170 160 ma porphyry skarn cu and pb zn ag vein deposits associated with i type granites and 160 150 ma metaluminous granite related polymetallic w sn deposits the late jurassic metaluminous granite related w sn deposits occur in a ne trending cluster in the interior of south china such as in the nanling area in the early mid cretaceous from about 120 to 80 ma but peaking at 100 90 ma subvolcanic related fe deposits developed and i type calc alkaline granitic intrusions formed porphyry cu mo and porphyry epithermal cu au ag mineral systems whereas s type peraluminous and or metaluminous granitic intrusions formed polymetallic sn deposits these cretaceous mineral deposits cluster in distinct areas and are controlled by pull apart basins along the south china continental margin based on mineral assemblage age and space time distribution of these mineral systems integrated with regional geological data and field observations we suggest that the three magmatic mineralization episodes are the result of distinct geodynamic regimes the triassic peraluminous granites and associated w sn nb ta mineralization formed during post collisional processes involving the south china block the north china craton and the indo china block mostly along the dabie sulu and songma sutures jurassic events were initially related to the shallow oblique subduction of the izanagi plate beneath the eurasian continent at about 175 ma but i type granitoids with porphyry cu and vein type pb zn ag deposits only began to form as a result of the breakup of the subducted plate at 170 160 ma along the nne trending qinzhou hangzhou belt also referred to as qin hang or shi hang belt which is the neoproterozoic suture that amalgamates the yangtze craton and cathaysia block a large subduction slab window is assumed to have formed in the nanling and adjacent areas in the interior of south china triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic w sn mineralization a relatively tectonically quiet period followed between 150 and 135 ma in south china from 135 ma onward the angle of convergence of the izanagi plate changed from oblique to parallel to the coastline resulting in continental extensional tectonics and reactivation of regional scale ne trending faults such as the tan lu fault this widespread extension also promoted the development of ne trending pull apart basins and metamorphic core complexes accompanied by volcanism and the formation of epithermal cu au deposits granite related polymetallic sn w deposits and hydrothermal u deposits between 120 and 80 ma with a peak activity at 100 90 ma

origin and evolution of ore forming fluids in a tungsten mineralization system middle jiangnan orogenic belt south china constraints from in situ la icp ms analyses of scheelite abstract the middle jiangnan orogenic belt is a very important tungsten w polymetallic belt in china there are many types of w deposits in the belt including veinlet disseminated and stratabound deposits which have different origins the veinlet disseminated dahutang w deposit has undergone extensive alteration such as biotitization potassic alteration and greisenization scheelite in veinlet disseminated w mineralization displays a zoned texture indicating at least two generations the early generation d1 from the dahutang w deposit exhibits magmatic hydrothermal characteristics with comparatively high nb ta and mo concentrations but a low sr concentration 44 to 95 ppm in contrast the scheelite samples from the xi an w deposit has relatively low nb ta and mo concentrations but a high sr concentration 582 to 861 ppm mainly originating from a metamorphic fluid that mixed with meteoric water the composition of the late generation of scheelite d2 samples from the dahutang deposit are intermediate between the composition of scheelite d1 and scheelite of the xi an depsoit the mineral chemistry of the scheelite samples indicate that the ore forming fluids of the dahutang deposit were dominated by magmatic hydrothermal fluids during the early stage and that meteoric water was added during fluid evolution the rare earth elements rees in the scheelite samples especially the variation of the eu eun smn gdn 0 5 values record the change in oxygen fugacity the ore forming fluids in the early stage of the dahutang deposit were reduced becoming oxidized during the precipitation of the d2 scheelite whereas the ore forming fluids of the xi an deposit were oxidized an increased oxygen fugacity of the ore forming fluids of the dahutang deposit restricted the precipitation of wolframite and promoted the formation of scheelite extensive alteration resulted in the decomposition of plagioclase thus releasing ca and sr for the crystallization of scheelite at the dahutang tungsten deposit

fluid inclusion study of xihuashan tungsten deposit in the southern jiangxi province china the xihuashan tungsten deposit is closely related to a small highly evolved granitic intrusion the fluid phases associated with the wolframite bearing quartz veins have been investigated using microthermometry and the raman microprobe they are highly variable in density and composition the earlier fluids are low density and low salinity co2 bearing aqueous solutions circulating at temperatures up to 420 c and low salinity 2 3 equiv wt nacl aqueous solutions without traces of co2 circulating at high temperatures 280 400 c involved in a specific hydrothermal fracturing event limited unmixing occurs at 380 c and 200 100 bar in response to a sudden pressure drop the second types of fluids related to deposition of idiomorphic drusy quartz are typical co2 bearing aqueous solutions with low salinity 2 5 equiv wt nacl homogenizing at low to moderate temperatures 180 340 c the late fluids characterize the sulfide deposition stage they are aqueous fluids with variable salinities homogenizing in the liquid phase between 100 and 275 c the xihuashan hydrothermal evolution resulted from a discontinuous sequence of specific events occurring between 420 and 150 c and during a continuous hydrothermal evolution of the system during cooling the role played by the co2 rich fluids in the transport and deposition of tungsten in the hydrothermal environment is discussed

thermospheric circulation temperature and compositional structure of the southern hemisphere polar cap during october november 1981 thermospheric temperature composition and winds at f region heights over the southern hemisphere polar cap have been measured by the dynamics explorer 2 de 2 satellite during october november 1981 perigee of the de 2 satellite during this period was over the southern hemisphere polar cap and measurements made along 0900 2100 local time polar passes are used to determine the average universal time dependence of thermospheric properties for this local time slice the f region wind vector is derived from the meridional wind component measured by the fabry perot interferometer fpi and the zonal wind component measured by the wind and temperature spectrometer wats instruments on board de 2 the neutral gas temperature is derived from fpi and wats measurements and the compositional structure is determined from the neutral atmosphere composition spectrometer instrument the measured temperature composition and winds along the 0900 2100 local time polar passes all display a universal time dependence that is due to the displacement between geomagnetic and geographic poles the temperature and molecular nitrogen densities are enhanced and the atomic oxygen density is reduced in the magnetic polar cap in comparison with lower latitude regions the neutral wind pattern follows the pattern of ion drift associated with magnetospheric convection the national center for atmospheric research thermospheric general circulation model tgcm is used to calculate the temperature composition and winds over the southern hemisphere polar cap region for conditions similar to those of october 1981 the tgcm includes displaced geomagnetic poles the temperature composition and winds are determined along the de 2 satellite track for various universal times the calculated winds are in general agreement with the observed winds both having a two cell pattern of magnetospheric convection the calculated and observed composition patterns are also in general agreement with predictions made by the mass spectrometer and incoherent scatter radar 1983 empirical model when models and observations are normalized to the same constant pressure surface the calculated and observed maximum compositional variations in the magnetic polar cap occur near 0900 ut when the dawn sector of the auroral oval passes over the south geographic pole the overall pattern of the calculated temperature variation is similar to that observed except for the period between 1300 and 1500 ut better agreement with temperature in this time range is obtained with the inclusion of auroral particle precipitation within the magnetospheric cusp

geology and molybdenite re os age of the dahutang granite related veinlets disseminated tungsten ore field in the jiangxin province china this is a brief research report about the recently discovered and currently being explored dahutang tungsten deposit or ore field in northwestern jiangxi south central china the deposit is located south of the middle lower yangtze river valley cu au mo fe porphyry skarn belt yrb the mineralization is genetically associated with cretaceous porphyritic biotite granite and fine grained biotite granite and is mainly hosted within a neoproterozoic biotite granodiorite batholith the dahutang ore field comprises veinlets disseminated 95 of the total reserve breccia 4 and wolframite scheelite quartz vein 1 ore styles the mineralization and alteration are close to the pegmatite shell between the cretaceous porphyritic biotite granite and neoproterozoic biotite granodiorite and the three styles of ore bodies mentioned above are related to zoned hydrothermal alteration that includes greisenization k feldspar alteration silicification carbonatization chloritization and fluoritization arranged in time early to late and space bottom to top five samples of molybdenite from the three types of ores have been collected for re os dating the results show re os model ages ranging from 138 4 ma to 143 8 ma with an isochron age of 139 18 0 97 ma mswd 2 9 the quite low re content in molybdenite falls between 0 5 ppm and 7 8 ppm that is indicative of the upper crustal source this is quite different from molybdenites in the yrb cu au mo fe porphyry skarn deposits that contain between 53 ppm and 1169 ppm re indicating a mantle source the dahutang tungsten system is sub parallel with the yrb porphyry skarn cu au mo fe system both are situated in the north margin of the yangtze craton and have a close spatial temporal relationship this possibly indicates a comparable tectonic setting but different metal sources both systems are related to subduction of the paleo pacific plate beneath the eurasian continent in early cretaceous the cu au mo fe porphyry skarn ores are believed genetically related to granitoids derived from the subducting slab whereas the porphyry w deposits are associated with s type granitoids produced by remelting of the upper crust by heat from upwelling asthenoshere

age and genesis of the w bi cu f au nui phao deposit northeast vietnam constrains from u pb and ar ar geochronology fluid inclusions study s o isotope systematic and scheelite geochemistry abstract northeast vietnam comprises several tectonic units which host number of metallic deposits of different types from orogenic gold to intrusion hosted pge deposits the lo gam domain being part of the ne vietnam hosts the lang vai gold district a several pb zn deposits and the recently discovered super large w bi cu f au nui phao deposit the nui phao deposit is 87 9 mt at 0 19 wo3 7 95 caf2 0 18 cu 0 19 g t au and 0 09 bi while the measured resource is 25 1 mt at 0 25 wo3 8 4 caf2 0 23 cu 0 26 g t au and 0 108 bi the nui phao deposit is a very interesting object for research due to location of the orebodies between of two granite massifs of the cretaceous da lien and triassic nui phao age consequently the temporal and genetic relationships of mineralization with a certain magmatic events are unclear here we present mineralogical compositional and geochronological data of the nui phao deposit in conjunction with physical chemical researches to understand the ore genesis and its genetic link to a certain magmatic events according to our observations at least three different mineral associations are distinguished at the nui phao deposit which include greisens skarns and quartz sulfide ore skarn and sulfide ore mineral assemblages generally contain abundant scheelite associated with pyrrhotite chalcopyrite and native bismuth the greisens consist of fluorite muscovite and rare molybdenite the results of fluid inclusions study indicate that at the nui phao deposit the initial ore forming fluid was represented by the reduced co2 ch4 h2o nacl cacl2 system characterized by high temperatures and moderate salinities the fluid boiling is the dominant mechanism for ore deposition at the nui phao deposit relatively homogeneous isotopic compositions of oxygen 18oh2o 6 73 to 9 24 and sulfur 34s 1 6 to 3 5 that closely correspond to magmatic source suggest that the ore forming fluid was generated from cooling granite pluton without contribution meteoric water the systematic studies of scheelite composition show that ree contents decrease from early to late scheelite generations which suggest gradual ree depletion of the ore forming fluid without significant fractionation between lree mree and hree the rees of scheelite are mainly controlled by the substitution mechanisms ca2 w6 ree3 nb5 and 3ca2 2ree3 ca by combining ree features y ho ratios and other characteristics of the nui phao deposit we propose a single magmatic source for hydrothermal ore firming fluids without fluid mixing a significantly contribution of material during fluid rock interaction is also unlikely the combination of mineralogical and geochemical features as well as complex studies of the formation conditions allowed us to conclude that gold at the nui phao deposit occur as impurities in the native bismuth the ages of the da lien and nui phao granite massifs and the nui phao deposit have been estimated to be ca 84 ma ar ar 244 ma u pb and ca 85 ma ar ar respectively indicating a genetic relationship between the mineralization and the cretaceous magmatic event

climatology and latitudinal gradients of quiet time thermospheric neutral winds over millstone hill from fabry perot interferometer measurements 1 midlatitude nighttime thermospheric neutral winds are strongly dependent on season solar activity and latitude we use an extensive database of wind measurements made during 1989 2001 by the millstone hill fabry perot interferometer to study the detailed climatology of quiet time neutral winds near an altitude of 250 km to facilitate the analysis of these data we develop a local time day of year solar flux and latitude dependent empirical model with the latitude dependence obtained by considering north looking and south looking observations separately our results show that the zonal winds are predominantly eastward after dusk and westward before dawn with the strongest eastward winds occurring in the winter and with an east to west transition that occurs earliest in the summer the zonal winds exhibit weak to moderate latitudinal gradients with more westward values to the north the zonal wind magnitudes decrease with increasing solar flux the strongest trends occur during winter the meridional winds are predominantly equatorward in all cases and exhibit strong latitudinal gradients with larger values to the north the maximum nighttime equatorward winds decrease with increasing solar flux except during summer when there is no significant solar activity variation they are largest during the summer except at solar minimum when a semiannual variation is observed and the peak winds occur during the equinoxes earlier studies of midlatitude wind measurements are generally consistent with our data with our results providing a considerably more detailed description of the nighttime wind climatology at midlatitudes

rare earth element systematics in scheelite from hydrothermal gold deposits in the kalgoorlie norseman region western australia scheelite cawo 4 is a widespread accessory mineral associated with hydrothermal veins in the archean gold deposits of the kalgoorlie norseman region of western australia rare earth element ree and other trace element abundances in scheelite have been determined in situ by excimer laser ablation inductively coupled plasma mass spectrometry ela icp ms in order to constrain the composition and sources of the mineralizing fluids the scheelites can be grouped according to the two distinct types of chondrite normalized ree ree n patterns which they exhibit hump shaped type i and flat type ii type i scheelites have higher total and na concentrations than type ii samples and can be further subdivided into type ia which has maximum ree n concentrations between sm and gd and type ib which has maximum ree n concentrations displaced toward dy type i scheelites are dominant at coolgardie kalgoorlie and kambalda whereas type ii samples are most abundant at norseman a few scheelite grains exhibit both type i and type ii characteristics the two types of ree n patterns with different na abundances suggest that the trivalent ree substituted into the ca site of scheelite by two different mechanisms 2ca super 2 ree super 3 na super for the type i scheelites and 3ca super 2 2ree super 3 ca where ca is a ca site vacancy for the type ii samples the parabolic shape of ree n patterns in the type i scheelites can be used to calculate the ionic radius of the ree super 3 that preferentially substitutes into the scheelite structure when type i ree patterns are normalized to account for variations in light ree abundance the average value obtained is 1 060 aa for type ia and 1 055 aa for type ib scheelites these values are smaller than the value of 1 12 aa for the ca site but are in excellent agreement with the value of 1 06 aa predicted by the coupled na super ree super 3 substitution mechanism assuming size as well as charge compensation this result implies that na super and ree super 3 substitute into adjacent sites in the crystal structure of type i scheelites in contrast the incorporation of ree into type ii scheelites appears to be independent of size it is suggested that in this type of scheelite involvement of a ca site vacancy relaxes the size constraint on the substitution of the ree super 3 the influence of ree speciation in the hydrothermal fluid on the systematic difference between scheelite fluid partition coefficients for type i and ii scheelites is of secondary importance compared with crystal chemistry effects the distinctive ree n patterns and high na contents of type i scheelites imply that they crystallized from hydrothermal fluids with higher na activities than those that formed type ii samples type i scheelites exhibit no changes in the size of the eu anomaly with ree concentration implying a predominance of eu super 3 and crystallization under relatively oxidized conditions type ii scheelites have variable eu anomalies and trivalent ree concentrations and thus appear to contain mostly eu super 2 and to have formed under reduced conditions type ia and ii scheelites have ce lu n 1 and are interpreted to have crystallized from light ree enriched fluids whereas type ib scheelites with ce ln n 1 formed from light ree depleted fluids the fluid characteristics inferred from the ree and trace element systematics in the scheelites can be attributed to the rock types and estimated physical conditions in the kalgoorlie norseman region at the time of hydrothermal activity high na activities are consistent with buffering of fluids by greenschist facies mafic rocks whereas low fluid na activities are a product of fluid rock reactions at higher metamorphic grades oxidized fluids are consistent with near surface derivation whereas reduced fluids are indicative of generation at elevated temperatures and pressures the range and distribution of fluid ce ln n ratios are similar to those of the major rock types in the region

double vein ore bearing vs ore free structures in the xitian ore field south china implications for fluid evolution and mineral exploration abstract two types of spatially and temporally associated hydrothermal veins ore bearing and ore free occur as double vein structures in the xitian ore field south china here we investigated the genetic relationship material provenance fluid properties and prospecting significance of the co developed veins in the granite related fault controlled vein type xiangdong w goudanlan w chaling pb zn and xinggao fluorite deposits of the xitian ore field focusing on two common minerals quartz and zircon petrographic cl microthermometric and h o isotopic analyses of stage i and stage ii quartz in both the ore bearing and ore free veins of these deposits document two episodes of hydrothermal activity the first episode involved a high temperature up to 370 high salinity up to 28 nacl equiv high 18o 2 1 to 7 2 and high 2h 82 to 54 mean 68 n 13 fluid that corresponds to the main magmatic hydrothermal stage of the deposits and the second episode involved a low temperature down to 90 low salinity down to 1 nacl equiv low 18o 8 8 to 5 3 and low 2h 83 to 60 mean 73 n 6 fluid that represents an accessary mineralization stage variations in fluid inclusion types and compositions indicate that the processes of fluid mixing boiling cooling and degassing played important roles in mineralization and that magmatic fluid became less important than meteoric water along during the formation of ore free veins la icpms u pb dating reveals totally different age populations for these veins zircons from the ore bearing quartz veins yield older and more variable ages pre devonian 400 ma n 68 that are similar to that of the local basement sedimentary rocks whereas zircons from the ore free quartz veins yield younger and less variable ages triassic 250 200 ma n 31 and jurassic 170 140 ma n 13 that are identical to those of the host granite zircons in addition the ore free veins show lower temperatures salinities and total rees as recorded by quartz but greater alteration as reflected by cl and trace element features of hydrothermally altered zircons and wider vein size than the ore bearing veins we propose a mineral water separation model to explain the formation of the double vein structures in this model ore bearing veins and ore free veins formed in succession during faulting events ore bearing veins formed first in the smaller fractures and were the dominant sites of mineralization whereas the ore free veins served as dissipating passageways for residual water and silica in larger fractures we suggest that the mineral water separation model has good application prospects in mineral exploration and that zircons can be applied as an indicative mineral to differentiate the mineralization potential of different types of quartz veins

genesis of the vein type tungsten mineralization at nyakabingo rwanda in the karagwe ankole belt central africa the vein type tungsten deposit at nyakabingo in the central tungsten belt of rwanda is located in the eastern flank of the complex bumbogo anticlinal structure the host rock is composed of alternating sequences of sandstones quartzites and black pyritiferous metapelitic rocks two types of w mineralized quartz veins have been observed bedding parallel and quartz veins that are at high angle to the bedding which are termed crosscutting veins both vein types have been interpreted to have been formed in a late stage of a compressional deformation event both vein types are associated with small alteration zones comprising silicification tourmalinization and muscovitization dating of muscovite crystals at the border of the veins resulted in a maximum age of 992 4 1 5 ma this age is within error similar to the ages obtained for the specialized g4 granites i e 986 10 ma the w bearing minerals formed during two different phases the first phase is characterized by scheelite and massive wolframite while the second phase is formed by ferberite pseudomorphs after scheelite these minerals occur late in the evolution of the massive quartz veins sometimes even in fractures that crosscut the veins the ore minerals precipitated from a h2o co2 ch4 n2 nacl kcl fluid with low to moderate salinity 0 6 13 8 eq wt nacl and minimal trapping temperatures between 247 and 344 c the quartz veins have been crosscut by sulfide rich veins based on the similar setting mineralogy stable isotope and fluid composition it is considered that both types of w mineralized quartz veins formed during the same mineralizing event given the overlap in age between the g4 granites and the mineralized quartz veins and the typical association of the w deposits in rwanda but also worldwide with granite intrusions w originated from the geochemically specialized g4 granites intense water rock interaction and mixing with metamorphic fluids largely overprinted the original magmatic hydrothermal signature

the h f ratio as an indicator of contrasted wolframite deposition mechanisms abstract understanding wolframite deposition mechanisms is a key to develop reliable exploration guides for w in quartz veins from the variscan belt of europe and elsewhere wolframites have a wide range of compositions from hubnerite mnwo4 to ferberite rich fewo4 deposition style source of mn and fe distance from the heat fluid source and temperature have been proposed to govern the wolframite h f hubnerite ferberite ratio defined as 100 at mn fe mn the argemela mineralized district located near the world class panasqueira w mine in portugal exposes a quartz wolframite vein system in close spatial and genetic association with a rare metal granite wolframite is absent as a magmatic phase but w rich whole rock chemical data suggest that the granite magma is the source of w wolframite occurs as large homogeneous hubnerites h f 64 75 coexisting with montebrasite k feldspar and cassiterite in the latest generation of intragranitic veins corresponding to magmatic fluids exsolved from the granite locally early hubnerites evolve to late more fe rich compositions h f 45 55 in a country rock vein an early generation of fe rich hubnerites h f 50 63 is followed by late ferberites h f 6 23 most argemela wolframites have h f ratios higher than at panasqueira and other variscan quartz vein deposits which dominantly host ferberites in greisens or pegmatitic veins wolframites generally have intermediate h f ratios in those deposits fluid rock interactions either involving country rocks quartz veins or granite greisens control w deposition in contrast at argemela wolframite from intragranitic veins was deposited from a magmatic fluid differentiation of highly evolved peraluminous crustal magmas led to high mn fe in the fluid which promoted the deposition of hubnerite therefore the h f ratio can be used to distinguish between contrasted deposition environments in perigranitic w ore forming systems hubnerite is a simple mineralogical indicator for a strong magmatic control on w deposition

geological characteristics of shimensi tungsten polymetallic deposit in northern jiangxi province the ore bodies in the shimensi deposit are stratiform pipelike and veinlike in form and occur in the upper part of the yanshanian acidic granitic body and also along the external contact zone of the biotite granodioritesof late jinning period wolframite sheelite chalcopyrite and molybdenite are the main ore minerals the ore is mainly in crystallization replacement and solid separation texture and in vein dissemination patch and massive structure the alterations of the host rock are mainly alkali feldspathization greisenization chloritization and silicification genetically the deposit belongs to the postmagmatic hydrothermal w cu mo deposit according to characteristics of the ore body mineral assemblage ore fabric metallogenic zoning and host rock alteration the main ore bodies can be further divided into veinlet dissemination type hydrothermal crypto explosion breccia type and thick vein type these kinds of ore bodies which surround the host rock of yanshanian acidic granite body form the shimensi one area three ore types tungsten polymetallic deposit the prospecting for the veinlet dissemination type scheelite in the shimensi deposit changes the previous prospecting which focused only onthe thick vein type of wolframite and provides a new direction for the main breakthrough in the prospecting for tungsten polymetallic ore bodies in the shimensi deposit and also in the jiuling ore concentration area

fluid inclusion study of the ballinglen w sn sulphide mineralization se ireland scheelite mineralized microtonalite sheets occur on the se margin of the end caledonian leinster granite in se ireland scheelite polymetallic sulphides and minor cassiterite occur in veins in the microtonalites disseminated throughout the greisened microtonalite sheets and in the adjacent wallrocks two major mineralized vein types occur in the microtonalite sheets 1 scheelite arsenopyrite pyrrhotite occur in quartz fluorite veins generally without a muscovite selvage 2 sphalerite chalcopyrite pyrite galena cassiterite stannite occur in quartz fluorite veins with a coarse muscovite selvage and are often intergrown with the muscovite quartz hosted fluid inclusions were examined from representative samples of both vein types using petrographic microthermometric and laser raman spectroscopic techniques three distinct types of fluid inclusions have been recognized primary vapour rich type 1 inclusions in quartz from the scheelite mineralized veins are of h2o co2 ch4 n2 h2s nacl composition and formed between 360 530 c primary and secondary liquid rich type 2 fluid inclusions in the base metal sulphide mineralized veins are of h2o ch4 n2 h2s nacl composition and formed between 340 480 c they also occur as pseudosecondary and secondary inclusions in scheelite mineralized veins late dilute low temperature h2o nacl kcl fluid inclusions may be related to late caledonian convection of meteoric waters around the cooling leinster granite batholith

in situ la icp ms trace element analyses of scheelite and wolframite constraints on the genesis of veinlet disseminated and vein type tungsten deposits south china abstract veinlet disseminated and vein type tungsten deposits are important tungsten resources in south china and show remarkable diversity in dominant tungsten minerals to better understand their genesis scheelite from the shimensi veinlet disseminated deposit and wolframite from the xihuashan and piaotang vein type deposits were selected to conduct in situ laser ablation inductively coupled plasma mass spectrometry trace element analyses the shimensi tungsten mineralization occurs in intensively altered granitic rocks and is characterized by scheelite two generations of scheelite in a single grain can be identified by cathodoluminescence cl imaging the early scheelite dark domains in cl images is characterized by nearly flat chondrite normalized ree ree n patterns with significantly negative eu anomalies whereas the late one bright domains in cl images shows light rare earth element lree enriched ree n patterns and obviously positive eu anomalies the former has higher ree na nb and ta and lower sr contents than the latter the xihuashan and piaotang wolframite quartz veins are developed in greisenized granite type i and metasedimentary rocks type ii both types of wolframite show lree depleted patterns but type i exhibits strongly negative eu anomalies and type ii positive eu anomalies type i contains higher ree nb and ta concentrations and lower feo mno ratios than type ii variations of eu anomalies and trace element compositions in both scheelite and wolframite can be used to decipher the origin and processes of tungsten mineralization both the early scheelite and wolframite type i display significantly negative eu anomalies and have high ree nb and ta contents suggesting that the initial ore forming fluids were of magmatic origin precipitation of tungsten minerals and alteration would effectively modify the composition of ore forming fluids deposition of the early tungsten minerals would lower ree nb and ta in the mineralizing fluids leading to depletion of these elements in the late ones although both the type i and ii wolframite have different ree contents and eu anomalies they show similar left dipped ree n patterns implying that compositional variation of fluids is likely driven by crystallization of wolframite during the processes of fluid evolution in contrast the elevated lree hree heavy rare earth element ratios eu eu n eu n values and sr abundances in the late scheelite are possibly caused by the decomposition of plagioclase and k feldspar alteration plays an important role in the formation of veinlet disseminated scheelite deposits it can be concluded that vein type wolframite mineralization is mainly formed by filling and that veinlet disseminated scheelite mineralization is associated with metasomatism

horizontal structures and dynamics of titan s thermosphere 1 the cassini ion neutral mass spectrometer inms measures densities of gases including n2 and ch4 in situ in titan s upper atmosphere we have used data from 13 targeted flybys of titan t5 t32 to construct an empirical model that describes the mean state of the thermosphere in the northern hemisphere giving the n2 and ch4 densities between 1000 and 1600 km as a function of latitude and height the principal features in the inms data are well reproduced by this simple model we find a pronounced oblateness in the thermosphere with densities above 1100 km altitude increasing by around 70 from the northern winter pole to the equator resulting in isobaric surfaces being 45 km higher over the equator than at the northern pole thermospheric temperatures derived from the densities tend to decrease with height from 149 10 k to 140 13 k near 1600 km considerable latitude differences are present in the temperatures below 1200 km near 1000 km altitude temperatures reach 164 6 k at 20 n and 131 6 k near 80 n using our thermosphere general circulation model with this thermal structure imposed we derive thermospheric horizontal wind speeds reaching 150 m s 1 with primarily poleward flow at equatorial latitudes which northward of around 60 n is accompanied by a band of prograde zonal winds of up to 50 m s 1 at high latitudes converging horizontal winds generate regions of strong subsistence we find thermospheric dynamics to be sensitive to coupling from below ch4 abundances are enhanced in the northern polar region which may result from transport by thermospheric winds

in situ la icp ms trace elemental analyses of magnetite the mesozoic tengtie skarn fe deposit in the nanling range south china abstract the nanling range in south china hosts numerous world class w sn deposits and some fe deposits the mesozoic tengtie fe skarn deposit in the southern nanling range is contemporaneous with the regional sn mineralization the deposit is composed of numerous ore bodies along the contacts between the late paleozoic or mesozoic carbonate rocks and the yanshanian lianyang granitic complex interaction of the magma with hosting dolomitic limestone and limestone formed calcic ca rich and magnesian mg rich skarns respectively the tengtie deposit has a paragenetic sequence of the prograde stage of anhydrous skarn minerals followed by the retrograde stage of hydrous skarn minerals and the final sulfide stage magnetite in the prograde and retrograde skarn stages is associated with diopside garnet chlorite epidote and phlogopite whereas magnetite of the final stage is associated with chalcopyrite and pyrite massive magnetite ores crosscut by quartz and calcite veins are present mainly in the retrograde skarn stage laser ablation icp ms was used to determine trace elements of magnetite from different stages some magnetite grains have unusually high ca na k and si possibly due to the presence of silicate mineral inclusions magnetite of the prograde stage has the highest co contents but that of the sulfide stage is extremely poor in co which partitions in sulfides magnetite of magnesian skarns contains more mg mn and al than that of calcic skarns attributed to the interaction of the magma with compositionally different host rocks magnetite from calcic and magnesian skarns contains 6 185 ppm sn and 61 1246 ppm sn respectively the high sn contents are not due to the presence of cassiterite inclusions which are not identified in magnetite instead we believe that sn resides in the magnetite structure regionally intensive mesozoic sn mineralization in south china indicates that concurrent magmatic hydrothermal fluids may be rich in sn and contribute to the formation of high sn magnetite our study demonstrates that trace elements of magnetite can be a sensitive indicator for the skarn stages and wall rock compositions and as such trace elemental chemistry of magnetite can be a potentially powerful fingerprint for sediment provenance and regional mineralization

fluid rock interaction is decisive for the formation of tungsten deposits tungsten mineralization is typically associated with reduced granitic magmas of crustal origin while this type of magmatism is widespread economic tungsten deposits are highly localized with 90 produced from only three countries worldwide therefore the occurrence of reduced magmatism while necessary for tungsten enrichment seems to be insufficient to form such rare deposits here we explore the mechanisms that lead to wolframite precipitation and evaluate whether they may exert a decisive control on tungsten global distribution tungsten differs from other rare metals enriched in magmatic hydrothermal ore deposits because it is transported as an anionic species precipitation of the main tungstate minerals scheelite cawo 4 and wolframite fe mn wo 4 thus depends on the availability of calcium iron or manganese we demonstrate quantitatively that magmatic fluids at panasqueira portugal provide tungsten in solution whereas the host rock contributes the iron required to precipitate wolframite the combination of special source conditions with specific reactive host rocks explains why major wolframite deposits are rare and confined to a few ore provinces globally

molybdenite re os and muscovite 40ar 39ar dating of the xihuashan tungsten deposit central nanling district south china abstract the xihuashan tungsten deposit in the central nanling region south china is an important vein type ore deposit hosted in cambrian strata and mesozoic granitic intrusions wolframite and molybdenite are the principal ore minerals the gangue minerals are mainly quartz and muscovite wolframite and molybdenite are products of the first stage hydrothermal activity whereas muscovite formed dominantly at the second stage molybdenite re os and muscovite 40ar 39ar dating have been carried out to investigate the age of mineralization re os isotopic dating for molybdenite associated with wolframite yield a precise well constrained isochron age of 157 8 0 9 ma mswd 1 5 ar ar isotopic analyses of muscovite yield a plateau age of 152 8 1 6 ma in agreement with an inverse isochron age of 152 8 1 6 ma which is 5 mys younger than the re os age the molybdenite re os age is interpreted as the age of tungsten mineralization this age coincides well with the zircon u pb age of the host granitic intrusion reported previously the 5 mys difference between molybdenite re os and muscovite 40ar 39ar ages probably represents the duration of hydrothermal activity the results show that the xihuashan tungsten deposit is one of many important tungsten tin deposits formed during 150 to 160 ma associated with large scale lithospheric extension in south china

origin and evolution of ore forming fluids of the larong w mo deposit eastern tibet constraints from fluid inclusions h o isotopes and scheelite geochemistry abstract the larong porphyry w mo deposit formed in the main collisional orogenic stage of lhasa and qiangtang terranes is the first discovered giant w mo deposit in the leiwuqi zogang metallogenic belt sanjiang region the w mo mineralization occurs as veins and stock works mainly hosted in the granodiorite porphyry monzogranite porphyry biotite granite porphyry and surrounding schist four types of fluid inclusions fis including pc type pure vapor co2 c type co2 h2o w type aqueous two phase and l type pure liquid h2o fis have been identified from stage i quartz scheelite alkaline feldspar veins stage ii including three sub stages quartz molybdenite pyrite chalcopyrite veins and stage iii quartz calcite pyrite veins the total homogenization temperatures of fis vary widely 187 437 c with multiple peaks indicating multistage fluid activities the ore forming fluids of the main mineralization stages are characterized by co2 enrichment high medium temperature 270 440 c and medium low salinity 2 4 14 4 wt nacl equiv the homogenization temperature of w type inclusions is obviously higher than that of c type inclusions and the salinity is relatively lower implying multiple immiscibility of fluids with continuous escape of co2 h o isotopic compositions suggest that the primary ore forming fluids dominantly originated from magma water mo concentrations and eu values in scheelite indicate a decreasing trend of redox state of ore fluids from stage i to stage ii to stage iii the relatively higher temperature co2 rich and oxidized fluids gradually evolved into relatively lower temperature co2 poor and reduced fluids here we propose that the decrease of temperature and oxygen fugacity and increase of s2 activity and ph values of the ore fluids caused by continuous fluid rock interaction and loss of co2 could account for the successive mineralization of w and mo at the larong deposit

scheelite geochemistry in porphyry skarn w mo systems a case study from the gaojiabang deposit east china abstract scheelite cawo4 a hydrothermal mineral commonly displaying enrichment in mo up to 16 and or rare earth elements ree is the main economic mineral in the gaojiabang porphyry skarn type w mo deposit east china based on microscopic observations and in situ la icp ms and la mc icp ms analysis three groups of scheelite each with different geochemical characteristics can be recognized this evidence provides a good basis for considering the behavior of some trace elements in scheelite and how they may constrain ore genesis in porphyry skarn systems p group scheelite occurs inside the porphyry rocks in the form of vein hosted or disseminated scheelite these have the lowest 87sr 86sr i values 0 7089 0 7108 lowest mo concentration mean 213 ppm n 51 lree hree ratios of 16 33 84 91 and highest ree concentration 191 405 ppm with downwards sloping ree fractionation trends s group scheelite occurs in skarns coexists with skarn minerals garnet diopside epidote etc and has the highest 87sr 86sr i values 0 7103 0 7113 highest mo concentration mean 1 323 ppm n 29 highest lree hree ratio 62 6 164 and lowest ree concentrations 68 5 112 ppm also with strongly downwards sloping ree fractionation trends h group scheelite occurs within veins hosted by hornfels and displays moderate 87sr 86sr i 0 70104 0 70122 mo mean 806 ppm n 17 lree hree ratio 16 32 42 55 and ree concentration 98 3 167 6 ppm during hydrothermal precipitation of scheelite changing redox state plays a major role in controlling mo behavior both the precipitation of early skarn minerals and changing redox states of ore forming fluids likely result in an increase in mo and corresponding decrease of hree in scheelite particularly in s group scheelite the sr isotope study indicates that crustal materials provided the main source for w mo bearing ore forming fluids furthermore both fluid mixing and fluid rock interaction played an important role in the evolution of ore forming fluids formation water or groundwater was likely involved in ore formation a geochemical model is described combining data for the different types of scheelite and the behavior of mo rees and sr isotopes to constrain the evolution of ore forming fluids and constrain ore genesis in the porphyry skarn system at gaojiabang this study contributes to the fingerprinting of ore deposits using scheelite geochemistry

scheelite elemental and isotopic signatures implications for the genesis of skarn type w mo deposits in the chizhou area anhui province eastern china scheelite is well developed in hydrothermal deposits providing a window into genetic processes and facilitating comparative studies however few studies have focused on characterizing scheelite in skarn type w mo deposits the primary ore mineral in the jitoushan and baizhangyan skarn type w mo deposits anhui province eastern china scheelite was analyzed for major trace and rare earth element ree abundance and for sr nd isotopes the analysis revealed two unique geochemical characteristics that distinguish the scheelite from skarn type w mo deposits to that from vein type au w and porphyry type w mo deposits higher mo content with a negative correlation between moo 3 and wo 3 and a strong hree depletion skarn type scheelite mainly inherited ree signatures from ore forming fluids and the early precipitation of skarn minerals e g garnet diopside and amphibole has most likely resulted in the observed strong hree depletion in scheelite and the decoupling of lrees and hrees of the numerous substitution mechanisms suggested by previous workers 3ca 2 2ree 3 ca where ca is a ca site vacancy is preferred for the substitution of ree 3 for ca 2 and in this study particularly given the low salinity of ore fluids as the scheelite eu anomalies were inherited from ore forming fluids with variable redox conditions and ph the complex deu mo correlation indicates that mo increasingly entered the scheelite under oxidizing conditions and reached a maxim at deu values of 0 8 to 1 in contrast under reducing conditions mo contents in scheelite decrease gradually and mo is precipitated as molybdenite as a result of the change in dominant valence state unlike the sr nd isotope compositions of scheelite from vein type au w and w sb au deposits the scheelite from skarn type w mo deposits has low 143 nd 144 nd t most 87 sr 86 sr t values most between 0 708 and 0 715 the end t values of the scheelite varied from 16 to 12 3 in the baizhangyan deposit and from 9 5 to 9 1 in the jitoushan deposit indicating that the ore forming materials in the two w mo deposits were mainly derived from crustal sources

magmatic hydrothermal rare element mineralization in the songshugang granite northeastern jiangxi china insights from an electron microprobe study of nb ta zr minerals abstract the songshugang granite hidden in the sinian metasedimentary stratum is a highly evolved rare element granite in northeastern jiangxi province south china the samples were systematically taken from the ck 102 drill hole at the depth of 171 423 m four types of rocks were divided from the bottom upwards topaz albite granite as the main body greisen nodules topaz k feldspar granite and pegmatite layer electron microprobe study reveals that the rare element minerals of the songshugang granite are very different from those of other rare element granites mn mn fe mn and ta ta nb ta of columbite group minerals and hf hf zr hf of zircon are nearly constant within each type of rocks however back scattered electron imaging revealed that nb ta oxides and zircon of the songshugang granite especially those of topaz albite granite topaz k feldspar granite and greisen are commonly characterized by a specific two stage texture on the crystal scale the early stage nb ta oxide is simply subhedral shaped columbite fe cgm i with low mn 0 16 0 37 and ta 0 05 0 29 columbite fe is penetrated by the later stage tantalite veinlets cgm ii or surrounded by complex nb ta sn w mineral assemblages including tantalite fe wodginite sl cassiterite and ferberite tantalite has wide range of mn values 0 15 0 88 from fe dominance to mn dominance wodginite with ta nb has large variable concentrations of w sn and ti cassiterite and ferberite are all enriched in nb and ta nb 2 o 5 ta 2 o 5 up to 20 12 wt and 31 42 wt respectively with high ta 0 5 similar to nb ta oxides and nb ta sn w mineral assemblages the early stage zircon is commonly included by the later stage zircon with sharply boundary they have contrasting hf contents and hfo 2 of the later stage zircon is up to 28 13 wt petrographic features indicate that the early stage of columbite and zircon were formed in magmatic environment however the later stage of rare element minerals were influenced by fluxes enriched fluids tantalite together with wodginite cassiterite and ferberite implies a ta dominant media an interstitial fluid rich melt enriched in ta and flux at the magmatic hydrothermal transitional stage is currently a favored model for explaining the later stage of rare element mineralization

wolframite solubility and precipitation in hydrothermal fluids insight from thermodynamic modeling abstract wolframite a solid solution series between hubnerite mnwo4 and ferberite fewo4 is the main tungsten bearing ore mineral in vein type tungsten deposits much progress has been made on characterizing the mineralizing fluids precipitating wolframite but it remains poorly understood what are the mechanisms depositing wolframite effectively and the variables controlling mn fe ratios in wolframite this study examines chemical controls on wolframite solubility in hydrothermal fluids and mn fe ratios in wolframite using thermodynamic models for fluids in the systems of w mn cl na o h and w fe cl na o h the fluid buffered models are established based on the characteristics of vein type tungsten deposits the modeling results indicate that solubilities of hubnerite and ferberite in hydrothermal fluids at typical w mineralizing conditions 300 400 c 500 1500 bars 5 15 wt nacl equivalent ph 4 6 reach up to hundreds of ppm the predominant tungsten manganese and iron species in fluids are h w o 4 m n c l 2 0 and f e c l 4 2 respectively an increase in ph and a decrease in fluid temperature and salinity are efficient mechanisms precipitating hubnerite and ferberite from acidic hydrothermal fluids hubnerite and ferberite are also significantly dissolved in alkaline hydrothermal fluids but their solubilities in alkaline fluids are insensitive to fluid temperature and salinity this may affect w mineralization at stages with different ph levels e g the greisen stage and the alkaline stage the mn fe ratio of mineralizing fluids is the principal variable controlling mn fe ratios in wolframite more supply of fe than mn from the fertile magma tends to produce fe rich mineralizing fluids this may be one of reasons why ferberite is more common than hubnerite in tungsten deposits and why hubnerite is more likely to precipitate at an early stage

in situ sr isotopic measurement of scheelite using fs la mc icpms abstract scheelite is one of the main ore minerals in tungsten deposits and sr isotopic compositions of scheelite can be used to examine the petrogenesis of igneous rocks and fluid metasomatism in mineralization processes both thermal ionization mass spectrometer tims and femsecond laser ablation multi collector inductively coupled plasma mass spectrometer fs la mc icp ms have been applied to analyze sr isotopic compositions in scheelite here we describe a la mc icp ms technique which can obtain in situ accurate high precision 87sr 86sr ratios from 20 to 50 m scheelite in line mode without requiring time consuming mineral separation and pre chemical procedures we found that ca dimers and ca argides do not detectably affect the obtained 87sr 86sr ratios and the adopted protocol overcomes interferences from kr rb er2 and yb2 the results of three mpi ding reference glasses kl2 g ml3b g and sths6 80 g are consistent with the recommended values here we show that the values of 87sr 86sr are relatively homogeneous for two scheelites from quartz veins and are comparable to the values determined by a traditional solution method hence these two scheelite samples have the potential to be reference materials for sr isotopic determination by la mc icp ms to illustrate the utility of the technique sr isotopes of scheelites from three different types of tungsten deposits of south china are documented the 87sr 86sr of scheelite from granite related veinlet disseminated and porphyry tungsten deposits varies systematically showing a positive correlation between sr content and 87sr 86sr ratios these micrometer scale inhomogeneities could be explained by mixing of two components reflecting intense fluid metasomatism during mineralization processes high 87sr 86sr ratios were obtained for the scheelite samples from a quartz vein type tungsten deposit indicating that the late stage ore forming fluid was mainly derived from the surrounding strata these examples show that in situ sr isotopic measurement of scheelite is a powerful tool to decipher the degree of fluid rock interaction in ore forming processes

assessment of the non hydrostatic effect on the upper atmosphere using a general circulation model gcm 1 under hydrostatic equilibrium a typical assumption used in global thermosphere ionosphere models the pressure gradient in the vertical direction is exactly balanced by the gravity force using the non hydrostatic global ionosphere thermosphere model gitm which solves the complete vertical momentum equation the primary characteristics of non hydrostatic effects on the upper atmosphere are investigated our results show that after a sudden intense enhancement of high latitude joule heating the vertical pressure gradient force can locally be 25 larger than the gravity force resulting in a significant disturbance away from hydrostatic equilibrium this disturbance is transported from the lower altitude source region to high altitudes through an acoustic wave which has beensimulated inaglobal circulation model forthefirst time due to the conservation of perturbation energy the magnitude of the vertical wind perturbation increases with altitude andreaches 150 250 m sat300 430 kmduringthe disturbance the upward neutral wind lifts the atmosphere and raises the neutral density at high altitudes by more than 100 these large vertical winds are not typically reproduced by hydrostatic models of the thermosphere and ionosphere our results give an explanation of the cause of such strong vertical winds reported in many observations citation deng y a d richmond a j ridley and h l liu 2008 assessment of the non hydrostatic effect on the upper atmosphere using a general circulation model gcm geophys res lett 35 l01104 doi 10 1029 2007gl032182

sm nd dating and ree composition of scheelite for the honghuaerji scheelite deposit inner mongolia northeast china abstract sm nd analyses of seven scheelite samples from scheelite quartz veins in the honghuaerji scheelite deposit produce a well defined linear array on an isochron diagram with a mean square weighted deviation mswd of 0 87 corresponding to an age of 178 4 2 9 ma with end t 1 50 this age is interpreted to represent the age of scheelite mineralization the scheelite sm nd age is in good agreement with u pb ages obtained from a mineralization related granite 179 4 178 6 ma indicating that there is no apparent age gap between granite crystallization and ore formation rare earth element ree abundances in the scheelite were determined by in situ laser ablation inductively coupled plasma mass spectrometry la icp ms and the scheelite samples contain elevated ree concentrations with total ree y contents in the range of 3339 to 6321 ppm the chondrite normalized ree distribution patterns of all scheelites are middle ree mree enriched with strong negative eu anomalies eu eu 0 09 0 23 the ree characteristics of the honghuaerji scheelite suggest that ree 3 substituted into the ca site along with na and nb dominated by na whereas eu is predominantly present as eu 2 in the scheelite and may have crystallized from relatively reduced fluids all sulfur isotope data 34 s for sulfide separates range from 2 0 to 3 8 with an average of 3 2 measured 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios vary from 18 243 to 18 451 15 494 to 15 574 and 37 933 to 38 340 respectively on the basis of common sr nd pb hf isotopic characteristics between the scheelite and the host granite and the positive initial nd isotope ratios 1 46 1 52 low 87 sr 86 sr ratios 0 704983 0 705297 in the scheelites it is inferred that the hydrothermal fluids responsible for tungsten mineralization at honghuaerji were of magmatic origin with a mantle derived signature based on the regional geology tectonic evolution and geochemical evidence the honghuaerji granite is thought to have been derived from the partial melting of thickened lower crust produced during post collisional orogenic events associated with the closure of the mongol okhotsk ocean

evaluation of statistical convection patterns for real time ionospheric specifications and forecasts 1 statistical models of high latitude plasma convection have been used in a wide range of studies pertaining to the ionosphere and thermosphere and they are beginning to be used in various space weather applications however the statistical convection models only provide average not instantaneous convection patterns and it is not clear if they are real convection patterns or blurred images of convection it is also unclear how reliable these convection models are for applications involving ionosphere thermosphere specifications and forecasts to address these issues a quantitative analysis was conducted of the weimer 2001 empirical convection model which is the most comprehensive model of high latitude convection that has been constructed to date first criteria were established to determine whether or not a modeled convection pattern was correct for a given set of geophysical conditions the criteria adopted were reasonable but stringent then the cross track ion drift velocities obtained from weimer 2001 were compared with the corresponding velocities measured by the dmsp f13 satellite the comparisons were done for nearly a year 1998 of satellite crossings of the northern polar region 4430 successive crossings the results indicate that the weimer 2001 model is able to produce the gross structure in the convection pattern i e it is good in a statistical sense however it does not adequately capture the mesoscale spatial structure and convection magnitudes observed by the dmsp satellite typically it was able to capture real instantaneous convection features in only about 6 of the satellite crossings although empirical convection patterns are invaluable for scientific applications these results have important implications for using empirical convection models in space weather applications

chemical and boron isotopic composition of hydrothermal tourmaline from the panasqueira w sn cu deposit portugal abstract tourmaline is a locally abundant hydrothermal mineral in the wallrocks surrounding the w sn cu mineralized veins in the panasqueira deposit portugal and a minor phase within the veins themselves tourmaline chemical and boron isotope compositions have been determined from three settings 1 pervasive fine grained tourmalinization zones in wallrocks within 10 cm of the veins 2 coarser tourmaline in wallrock hosted fault zones and 3 needle shaped tourmaline from late stage vugs in the quartz veins all tourmalines from panasqueira have ferromagnesian compositions with significant octahedral aluminum contents and variable x site vacancies tourmaline compositions show significant chemical variations at the grain and sample scale but are homogeneous on the deposit scale tourmaline is typically optically and chemically zoned showing significant increases in fe and f and decrease in mg ca and al from core to rim moreover as a general trend al increases and mg decreases with proximity to the vein contact the observed chemical variation seems to have been controlled mainly by the vectors femg 1 x alna 1 r2 1 x al oh na 1 r2 1f 1 r2 oh f al 1o 1 and x al2o na 1 r2 2 oh f 1 the total range in tourmaline 11b values from the panasqueira w sn cu deposit is from 3 7 to 12 7 including tourmaline from the three settings the calculated b isotope composition of the hydrothermal fluid based on the average tourmaline composition of 9 and an estimated alteration temperature in the wallrocks based on ti in quartz thermometry of 500 c is 7 1 this isotopic composition is permissive of a boron source from local metasediments or an s type granite but the high boron concentration in the wallrocks with 50 vol tourmaline along with the typical element association of panasqueira w sn f nb ta rb makes a granitic source more likely late stage tourmaline needles in vugs within the mineralized veins show the same patterns and ranges in both chemical and boron isotope composition suggesting that exsolved magmatic fluids were injected in at least two pulses the variations in chemical and boron isotopic compositions of tourmaline combined with estimates from ti in quartz thermometry suggest that hydrothermal ore formation is associated with fluid cooling and geochemical fluid rock interactions

fault fluid evolution in the xitian w sn ore field south china constraints from scheelite texture and composition abstract understanding fault fluid evolutionary processes is crucial for understanding the genesis of vein type deposits scheelite and quartz are common hydrothermal minerals in w sn ore field faults in the xitan ore field nanling range south china scheelite textural and compositional features were studied and two types of scheelite were identified type i represented by scheelite in the xihu fault is intergrown with quartz has oscillatory zonation variable zonation band width and is homogeneous light grey color in cathodoluminescence images and type ii represented by scheelite in the goudalan fault is intergrown with quartz that shows multi stage growth has oscillatory zonation and each zonation band is the same width scheelite grains of both types have homogeneous major element distribution e g w and ca however trace element contents e g mg nb are slightly variable and rare earth element ree and y contents gradually decrease by an order of magnitude from the core to the rim in both types of scheelite from core to rim the chondrite normalized ree patterns of type i scheelite change from flat curves with no or slightly positive eu anomalies to intense concave shapes with intense positive eu anomalies the middle rees gradually become depleted indicating the mree fractionation associated with early scheelite precipitation in a relatively closed fault fluid system in contrast the chondrite normalized ree patterns of type ii scheelite grains are similar all showing weak mree depletion from the core to rim implying recurrent fluid pulses in an open fault fluid system the ree patterns in the cores of the type i scheelite are similar to those of the scheelite from jurassic granites related to the w sn mineralization suggesting that the initial ore forming fluids were exsolved from the jurassic magma the ree patterns in the rims of type ii scheelite are consistent with those of scheelite from the goudalan w deposit suggesting that the fault fluid system experienced a similar evolution to the ore forming fluid system combining the results of this work with previous quartz h o isotopic and fluid inclusion studies it can be concluded that fluid mixing occurred in both the fault fluid system and the ore forming fluid system triggering large scale w precipitation

the earth s thermospheric superrotation from dynamics explorer 2 neutral thermospheric zonal winds measured from the wind and temperature experiment on dynamics explorer 2 have been analyzed to provide a measure of the superrotation of the neutral thermosphere the data were averaged in local time in 10 degree bands from the equator to 40 degrees latitude the results show an average wind velocity on the order of 18 m s to the east at the equator and a westward wind of the same magnitude at mid latitudes within the range of altitudes of the data base 200 to 700 km no evidence of any significant altitude dependence was found averaging our data over the latitude bands studied indicates a net corotation of the thermosphere this result is not in agreement with the superrotation value reported by king hele and walker on the basis of satellite drag analysis

simultaneous thermospheric observations during the geomagnetic storm of april 2002 from south pole and arrival heights antarctica 1 simultaneous ground based optical measurements of the response of the thermosphere to the geomagnetic storm of april 2002 were made at south pole 90 s and arrival heights 78 s large meridional and zonal winds were observed with values reaching 600 m s the kinetic temperature during the storm showed an increase nearly 3 fold from the normal values during the time of peak wind while the emission of the 630 nm increased over 20 fold simulation of the storm with the time gcm model including low energy electron precipitation observed by the dmsp satellites shows good agreement with the measurements without low energy electron precipitation the model simulation underestimates the kinetic temperature and emission

the thermosphere of titan simulated by a global three dimensional time dependent model we present three dimensional numerical simulations for dynamics and energetics of titan s thermosphere in so doing we distinguish between the dynamics driven by solar insolation and those driven by vertical coupling to winds in titan s middle atmosphere our calculations reveal that the solar driven thermospheric dynamics are characterized by the balance between pressure gradients and viscosity while the super rotating zonal winds detected in titan s stratosphere set up a balance between the pressure gradients curvature and coriolis forces the day to night temperature gradients in the upper thermosphere around 1300 km typically lie around 20 10 k for solar maximum minimum with peak solar driven winds of around 60 30 m s this difference decreases with height and virtually disappears below 1000 km as a result of dayside adiabatic cooling and nightside adiabatic heating the model highlights unique features about the thermosphere on titan such as the important nighttime heating from mid latitudes to high latitudes caused by the relatively small size of the planet s shadow leading to features in the wind profiles which are not found on earth although the lack of measurement constraints prevents us from making predictions of actual wind profiles on titan the model does illustrate the physical processes driving the dynamics and suggests that anticipated thermospheric measurements from the cassini spacecraft may provide constraints also for the dynamics at lower altitudes

the molybdenite re os isotope chronology in situ scheelite and wolframite trace elements and sr isotope characteristics of the chuankou tungsten ore field south china abstract the chuankou tungsten ore field situated in the central area of the qing hang ancient suture zone in south china is characterized by predominantly quartz vein type tungsten mineralization that formed near the contact between the chuankou granite and slightly metamorphosed silt bearing sericite slate based on field work cathodoluminescence molybdenite re os dating and in situ laser ablation inductively coupled plasma mass spectrometry la icp ms analysis the chuankou tungsten ore was formed at 230 6 2 9 ma to 229 4 2 6 ma in a typical indosinian metallogenic event in addition three distinct generations of scheelite and two types of wolframite can be clearly distinguished type 1 wolframite has a semiautomorphic grain or brecciated vein structure with a high heavy rare earth element hree content and an obvious negative eu anomaly type 2 wolframite grains are strongly altered as residual pseudomorphic structures by ore forming fluids and have relatively low ree contents sch 1 scheelite is present in the interior of the type 2 wolframite grains the sch 1 scheelite grains have an elevated ree content and low 87sr 86sr ratios with a strongly negative eu anomaly which suggests an inheritance signal of the host rocks comparatively sch 2 and the altered sch 1 scheelite have characteristic extremely low ree contents and remarkably strong positive eu anomalies these scheelites also have increased 87sr 86sr ratios and low 88sr signals sch 3 is idiomorphic with perfect oscillating zoning the ree content of sch 3 which typically has the lowest 87sr 86sr ratios is higher than those in sch 1 and sch 2 and the extremely high 88sr signals indicate a distinct thermal fluid event that was directly derived from the host rock the correlations between the ree and nb of scheelite imply a type b substitution of sch 1 and sch 2 but a type c substitution for sch 3 the correlation of eun and eun shows an eu3 substitution process for stages sch 1 and sch 2 and an eu2 substitution process for stage sch 3 thus we confirm that ore bearing hydrothermal rocks must undergo early stage metasomatism and filling middle stage fluid mixing between wall rocks and magmatic hydrothermal activity and refilling of late stage magmatic hydrothermal activity during the metallogenic process during the indosinian period the mineralization stages of polymetallic deposits in the indosinian were composed of stage 1 240 to 220 ma and stage 2 220 to 200 ma the chuankou tungsten ore field can be considered as the typical representation of the stage 1 metallogenic event in south china this ore field is derived from remelting of the ancient basement and was reduced by regional extension under the dominant compression regime in the south china block

infrared microthermometric and stable isotopic study of fluid inclusions in wolframite at the xihuashan tungsten deposit jiangxi province china the xihuashan tungsten deposit jiangxi province china is a world class vein type ore deposit hosted in cambrian strata and mesozoic granitic intrusions there are two major sets of subparallel ore bearing quartz veins the ore mineral assemblage includes wolframite and molybdenite with minor amounts of arsenopyrite chalcopyrite and pyrite there are only two phase aqueous rich inclusions in wolframite but at least three major types of inclusions in quartz two or three phase co2 rich inclusions two phase pure co2 inclusions and two phase aqueous inclusions indicating boiling fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities 239 380 c 3 8 13 7 wt nacl equiv compared with those in quartz 177 329 c 0 9 8 1 wt nacl equiv these distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process enthalpy salinity plot shows a linear relationship implying mixing of different sources of fluids although boiling occurred during vein type mineralization it seems negligible for wolframite deposition mixing is the dominant mechanism of wolframite precipitation in xihuashan 34s values of the sulfides range from 1 6 to 0 1 indicative of a magmatic source of sulfur 18o values of wolframite are relatively homogeneous ranging from 4 8 to 6 3 oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite

ore forming mechanism of quartz vein type w sn deposits of the xitian district in se china implications from the trace element analysis of wolframite and investigation of fluid inclusions abstract the xitian w sn district is located in eastern hunan province of se china and comprises the heshuxia goudalan and longshang w sn deposits our study on the occurrence mineral assemblage and geochemistry of the orebodies shows that quartz vein orebodies are dominant mode of mineralization and can be divided into three stages stage i quartz molybdenite wolframite i stage ii quartz wolframite ii polymetallic sulfides and stage iii quartz pyrite fluorite the elements nb ta sc sn zn cr v mo cu and zr are abundant in both wolframite i and wolframite ii wolframite i contains higher concentrations of nb 1408 9245 ppm ta 241 2407 ppm and sc 123 521 ppm than wolframite ii nb 144 1080 ppm ta 3 76 315 ppm and sc 1 86 11 44 ppm these results indicate that wolframite i was formed closer to the host rock and at a greater ore forming depth than wolframite ii the total ree concentrations of wolframite i and ii range from 34 96 to 133 36 ppm and 21 30 to 43 73 ppm respectively both wolframite i and wolframite ii have low lree concentrations 0 00 0 05 and 0 08 8 18 ppm respectively and high hree concentrations 34 96 133 31 and 21 23 41 87 ppm respectively the enrichment of hrees in wolframite may be due to the fact that the sizes of the hrees3 0 94 1 02 a in combination with nb5 or ta5 0 72 a are closer to that of w6 0 68 a in combination with ca2 1 08 a or mg2 0 80 a than that of the lrees3 1 03 1 13 a making the coupled substitution easier a study of fluid inclusions in the coexisting gangue minerals shows that the homogenization temperatures of the fluid inclusions decrease from stage i to stage iii stage i 187 382 c average 275 c stage ii 122 278 c average 175 c stage iii 92 172 c average 139 c whereas the salinities of the fluid inclusions increase from stages i to ii and decrease from stages ii to iii stage i 1 8 18 2 wt nacleqv average 10 3 wt nacleqv stage ii 7 3 24 4 wt nacleqv average 14 9 wt nacleqv stage iii 0 2 5 3 wt nacleqv average 1 5 wt nacleqv raman spectroscopy reveals that the fluid inclusions mainly contain h2o co2 is minor and h2s ch4 and n2 are rare we conclude that the formation of wolframite was driven by post magmatic thermodynamic processes the ore forming fluid flowed through a multi fractured low pressure zone in the fault system in the district and a temperature pressure decrease led to fluid immiscibility characterized by co2 escaping in a low ph and high eh environment in stage i crust mantle mixed fluid and meteoric water mixing in stage ii and natural cooling of the fluid system in stage iii

altitude dependence of middle and low latitude daytime thermospheric disturbance winds measured by windii 1 thermospheric neutral winds exhibit strong altitudinal and latitudinal variation during geomagnetically quiet and active times we use daytime middle and low latitude neutral winds measured by the wind imaging interferometer windii instrument on board the upper atmosphere research satellite uars over the 90 275 km height range to study the altitude and season dependent climatology of disturbance winds i e with quiet time patterns removed in magnetic coordinates the daytime perturbations winds are generally equatorward and westward and decrease toward the magnetic equator both the zonal and meridional components decrease sharply below 120 km and are essentially insignificant below 100 km the seasonal dependence of the disturbance winds is strongest in the early morning sector the zonal disturbance winds are predominantly westward with largest magnitudes near 150 km at late afternoon upper midlatitudes magnetic latitudes 50 60 and near 120 km in the early morning winter between 25 and 45 at upper midlatitudes in the early morning sector the zonal perturbation winds are eastward above 120 km in the summer hemisphere and between 120 and 180 km in the winter hemisphere eastward perturbations are also observed near the magnetic equator with largest values near noon at 250 km the meridional perturbation winds are mostly equatorward and nearly height independent above 150 km with the largest magnitudes occurring in the early morning winter hemisphere in the late afternoon sector the upper midlatitude meridional disturbance winds are poleward and there is a small winter to summer flow at lower latitudes in general the storm time dependence of the disturbance winds is quite complex the perturbation winds begin to develop after 0 9 hours and tend to saturate 12 24 hours after storm onset the development does not change much with altitude and the seasonal dependence is generally important only at storm times greater than 6 12 hours

tracing metal sources in peribatholitic hydrothermal w deposits based on the chemical composition of wolframite the example of the variscan french massif central abstract we present a complete dataset for major minor and trace elements in wolframite fe mn wo4 based on the example of several peribatholitic hydrothermal w deposits located in the variscan french massif central fmc the wolframite samples were characterized down to the micrometer scale by combining scanning electron microscopy observations and in situ chemical analysis by electron probe microanalyzer and laser ablation inductively coupled plasma mass spectrometry most samples are fe dominated wolframites and are characterized by variable fe fe mn values for the studied deposits from 0 36 to 0 86 without significant alteration features wolframites present intracrystalline variations for concentrations of several minor and trace elements principally for nb ta and sn which reflect growth zoning the minor and trace element compositions of the different wolframite samples show at first order similar enrichments in ta nb sn zn and in as well as depletions in lree li th ti zr hf pb v co and mg compared to the upper continental crust second order compositional variations are observed between the studied deposits which can be separated in four main regional geochemical groups this work highlights that the chemical composition of wolframite is controlled by both the crystallochemical parameters and the composition of the primary hydrothermal fluid the regional variations observed in the geochemical signatures of wolframite reflect local variations in the composition of the hydrothermal fluid i e variable metal sources therefore this suggests that the minor and trace element contents in wolframite likely represent direct markers of the source of the hydrothermal fluid and ultimately of the metals the comparison between the trace element compositions of wolframite with the compositions of regional granitic rocks and worldwide shales suggests that evolved peraluminous granites represent the main source of metals in peribatholitic hydrothermal w deposits from the fmc whereas metasedimentary rocks have a limited to no influence on the metal budget

oxygen isotope and trace element zoning in hydrothermal garnets windows into large scale fluid flow behavior single garnet crystals from a large multicyclic hydrothermal system in far east russia are strongly growth zoned microscale ion microprobe analysis reveals consistent intracrystalline patterns in oxygen isotope composition and boron and iron contents reflecting evolution of the hydrothermal system from magmatic to meteoric dominated conditions and repetitive influx of magmatic fluids large intracrystalline variations in oxygen isotope composition 12 18 o delimit temporal evolution of magmatic and meteoric fluid input within different portions of the hydrothermal system and suggest that fluid flow regimes differed between central and distal portions of the system these results provide compelling evidence that microanalytical data can be extrapolated from intracrystalline scales to study macroscale processes in complex large scale fluid rock systems

titan s middle atmospheric temperatures and dynamics observed by the cassini composite infrared spectrometer the composite infrared radiometer spectrometer cirs instrument on the nasa cassini saturn orbiter has been acquiring thermal emission spectra from the atmosphere of titan since orbit insertion in 2004 observation sequences for measuring stratospheric temperatures have been obtained using both a nadir mapping mode and a limb viewing mode the limb observations give better vertical resolution and give information from higher altitudes while the nadir observations provide more complete longitude coverage because the scale height of titan s atmosphere is large enough so that emission from a grazing ray is influenced by horizontal temperature variations in the atmosphere we have developed a twodimensional temperature retrieval algorithm for reducing the limb spectra which solves simultaneously for meridional and vertical temperature variations the analyzed nadir mapping data have sampled nearly all longitudes at latitudes from about 90 st o 60 n providing temperatures between pressure levels of about 5 to 0 2 mbar the limb data covers latitudes between about 75 s and 85 n and yields temperatures between about 1 and 0 005 mbar at a small number of longitudes the retrieved temperatures are consistent with early results from nadir observations flasar f m and 44 colleagues 2005 science 308 975 978 between 0 5 and 5 mbar where both results are valid with the warmest temperatures at the equator and much stronger meridional temperature gradients in the northern winter hemisphere than in the southern at higher altitudes not probed by nadir viewing the limb data reveal that the stratopause is nearly 20 k warmer in the northern polar regions than at the equator and southern hemisphere and that the altitude of the stratopause shifts from 0 1 mbar 300 km near the equator to 0 01 mbar 400 km poleward of about 40 n when the gradient wind equation is used to construct a zonal mean wind the reversal in sign of the temperature leads to capping of the winter westerly flow the core of the resulting jet is about 190 m s 1 in magnitude spans between 30 n and 60 n and peaks near 0 1 mbar estimates of the radiative heating associated with the radiative disequilibrium lead to a meridional overturning timescale of about three earth years

winds in the high latitude lower thermosphere dependence on the interplanetary magnetic field 1 wind observations in the summertime lower thermosphere at high southern latitudes measured by the wind imaging interferometer windii on the upper atmosphere research satellite are statistically analyzed in magnetic coordinates and correlated with the interplanetary magnetic field imf to determine influences of imf dependent ionospheric convection on the winds effects are clearly detectable down to 105 km altitude above 125 km the wind patterns show considerable similarity with ionospheric convection patterns and the speed of the averaged neutral wind in the polar cap often exceeds 300 m s the correlation between the imf bz component and the diurnal harmonic of the winds is generally best when the imf is averaged over the preceding 1 4 5 hours the magnetic zonal mean zonal wind below 120 km correlates best with the imf by component when the latter is averaged over approximately the preceding 20 hours the wind has a significantly stronger rotational than divergent component around and above 120 km a dusk side anticyclonic wind vortex is prominent consistent with earlier findings around 140 km and higher the dusk side vortex intensifies for negative bz but around 120 km it is the dawn side cyclonic vortex that responds more strongly to bz variations the dependence of the wind on the imf is nonlinear especially with respect to imf bz for positive bz the difference winds are largely confined to the polar cap while for negative bz the difference winds extend to subauroral latitudes a significant correlation between the diurnal bz dependent neutral and convection velocity components exists above 108 km when the convection velocity is suitably rotated in magnetic local time mlt with respect to the wind the rotation that maximizes the correlation ranges from 1 5 hours at 130 km wind preceding convection to nearly 6 hours at 108 km wind lagging convection the rotated diurnal bz dependent wind pattern projects onto the diurnal bz dependent ionospheric convection pattern with about 60 the amplitude of the latter above 125 km decreasing to about 17 at 108 km on timescales of 20 hours a by dependent magnetic zonal mean zonal wind generally exists with maximum wind speeds at 80 magnetic latitude typically 10 m s at 105 km increasing to about 60 m s at 123 km and 80 m s at 200 km in the southern hemisphere the wind is cyclonic when the time averaged by is positive and anticyclonic when by is negative the wind direction is expected to be opposite in the northern hemisphere

textural and chemical variations of micas as indicators for tungsten mineralization evidence from highly evolved granites in the dahutang tungsten deposit south china

microfracturing and fluid mixing in granites w sn ore deposition at vaulry nw french massif central abstract the vaulry w sn mineralisation located at the eastern boundary of the blond rare metal leucogranite is contained in a set of subvertical quartz veins locally with muscovite and minor quartz selvages the sequence of deposition was 1 milky quartz predominantly as fracture filling generally affected by subsequent ductile deformation 2 hyaline quartz wolframite cassiterite 3 minor sulphides other sets of quartz veinlets although generally barren are observed in the blond massif fluid migration at the microscopic scale within the granite and in the vicinity of quartz fractures was constrained by studying the geometry of fluid inclusion planes and fluid inclusion chemistry in and outside the mineralised area three major sets of subvertical fluid inclusion planes are recognised a n050 060 e set mostly developed in the veins and in the immediate vicinity a n110 130 e set regionally developed in the granite and a n140 160 e set of local extent as a whole the density of fip decreases from the mineralised zones toward the barren part of the pluton except for the n140 160 e set these are locally abundant around quartz veinlets with similar orientations that form a broad n s band near the blond locality mineralising fluids observed as primary inclusions in cassiterite and in undeformed hyaline quartz are mostly aqueous with moderate salinity and a minor volatile component at variance with many other w sn deposits in the variscan belt ore deposition occurred around 315 c at an estimated depth of 5 5 km under hydrostatic to slightly suprahydrostatic pressures it resulted from fluid mixing in the central part of a large hydrothermal system between two end members i a hot 425 430 c moderately saline fluid that contained a diluted volatile component and although na dominated minor amounts of li and ca the estimated 18o indicates that this fluid was completely equilibrated with the tectono magmatic pile pseudo metamorphic fluid ii a cold 230 c low salinity fluid evolved meteoric water that mixed with and eventually overprinted the early moderately saline fluid responsible for granite muscovitization at 425 430 c later a second hydrothermal system was initiated by the percolation of heated meteoric water with very low salinity the system was by then at least 3 5 km deep and the fluid was heated to 300 c these characteristics are reminiscent of the ca 305 ma episyenitic hydrothermal system known elsewhere in the n limousin

global and temporal variations in hydrocarbons and nitriles in titan s stratosphere for northern winter observed by cassini cirs mid infrared spectra measured by cassini s composite infrared spectrometer cirs between july 2004 and january 2007 ls 293 328 have been used to determine stratospheric temperature and abundances of c2h2 c 3h4 c 4h2 h cn and hc3n over 65 000 nadir spectra with spectral resolutions of 0 5 and 2 5 cm 1 were used to probe spatial and temporal composition variations in titan s stratosphere cassini s 180 orbital transfer in mid 2006 allowed low emission angle observations of the north polar region for the first time in the mission and allowed us to probe the full latitude range we present the first measurements of composition variations within the polar vortex which display increasing abundances right up to 90 n the lack of a homogeneous abundance latitude variation within the vortex indicates limited horizontal mixing and suggests that subsidence is greatest at the vortex core contrary to numerical model predictions and tropospheric cloud observations we do not see any evidence for a secondary circulation cell near the south pole which suggests a single hadley type circulation in the stratosphere at this epoch this difference can be reconciled if the secondary cell is restricted to altitudes below 100 km where there is no sensitivity in our data temporal variations in composition were observed in the south with volatile species becoming less abundant as the season progressed the observed variations are compared to numerical model predictions and observations from voyager

pyrite as a record of hydrothermal fluid evolution in a porphyry copper system a sims empa trace element study porphyry copper deposits are currently the world s largest source of copper and molybdenum and are also among the largest reservoirs of gold in the upper crust despite the fact that pyrite is a ubiquitous mineral phase in these deposits and secondary cu enrichment processes are commonly controlled by the abundance of this sulfide the major and trace element chemistry of pyrite from porphyry systems remains unconstrained in this study we report the first comprehensive trace element database of pyrite from the dexing deposit china s largest porphyry cu deposit by combining high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capabilities of secondary ion mass spectrometry sims in a suite of samples from the dexing deposit we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and heavy metals e g cu co ni zn hg in pyrite from porphyry systems are more significant than previously thought among the elements analyzed cu as au and ni are the most abundant with concentrations that vary from sub ppm levels to a few wt i e 6 wt cu 3 wt as 0 25 wt au and 0 2 wt ni detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrite from the dexing deposit is characterized by complex chemical zoning where the studied elements occur in different mineralogical forms while as occurs as a structurally bound element in pyrite cu and au can occur as both solid solution and micro to nano sized particles of chalcopyrite and native au or au tellurides respectively indicating that pyrite can control metal speciation and partitioning during porphyry cu mineralization the well developed oscillatory zoning detected in pyrite where cu rich as depleted growth zones alternate with cu depleted as rich layers indicates that cu is geochemically decoupled from as suggesting that this selective partitioning of metals into pyrite is most likely the result of changes in hydrothermal fluid composition

geochronology and geochemistry of granitoids related to the giant dahutang tungsten deposit middle yangtze river region china implications for petrogenesis geodynamic setting and mineralization abstract porphyry and skarn deposits in the middle yangtze valley within the northern yangtze craton have a combined tungsten resource of 3 million tonnes mt and represent one of the most important tungsten regions in the world the dahutang porphyry tungsten deposit with reserves of 1 mt is one of the largest deposits uranium pb analyses for the ore related granitoids yield ages of 147 4 0 58 ma 148 3 1 9 ma for porphyritic biotite granite 144 7 0 47 ma 146 1 0 64 ma for fine grained granite and 143 0 0 76 ma 143 1 1 2 ma for granite porphyry a progressive youngling of ages that is consistent with field observations geochemical data show that the three types of granite are characterized by enrichments in rb pb and u and depletion in ba nb p and ti with asi molar al 2 o 3 cao na 2 o k 2 o 1 1 that is characteristic of a peraluminous melt the p 2 o 5 contents of the granites are 0 13 0 37 and have a positive correlation with sio 2 and they are thus s type intrusions they exhibit initial 87 sr 86 sr of 0 721 to 0 731 and e nd t of 5 06 to 7 99 for porphyritic biotite granite 0 7196 to 0 7289 and 6 29 to 6 74 for fine grained granite and 0 7153 to 0 7365 and 5 09 to 7 64 for granite porphyry chondrite normalized rare earth element ree patterns for the granites are characterized by enrichment in the light ree and a strong negative eu anomaly indicating that they were derived from the proterozoic pelitic and psammitic basement strata and experienced strong fractional crystallization of plagioclase our ca 150 140 ma age for the dahutang s type magmatism and w mineralization is identical to that of the i type magmatism related to cu au mo fe bearing porphyry and skarn deposits along the middle to lower yangtze river valley we propose that the latest jurassic to earliest cretaceous granitoids and ores formed during a tearing of the subducting izanagi slab which caused the upwelling of asthenosphere and resulting mantle crust interaction the s type granitoids and related w ore systems resulted from the re melting of the proterozoic crust whereas the i type granitic rocks and related ores are attributed to the partial melting of the subducted slab

trace elements and sr nd isotopes of scheelite implications for the w cu mo polymetallic mineralization of the shimensi deposit south china the shimensi deposit south china is a newly discovered w cu mo polymetallic deposit with a reserve of 0 76 million tones wo 3 one of the largest tungsten deposits in the world we report elemental and sr nd isotopic data for scheelites from the giant deposit to determine the source region and genesis of the deposit scheelite is the most important ore mineral in the shimensi deposit trace elements including rees and nd sr isotopic compositions of scheelites were used to constrain the origin of the mineralizing fluids and metals our data reveal that the rees of scheelite are mainly controlled by the substitution mechanism 3ca 2 2ree 3 ca where ca is a ca site vacancy scheelites from the shimensi deposit show negative eu anomalies in some samples but positive eu anomalies in others in the chondrite normalized ree patterns the variation of eu anomalies recorded the ore forming processes considering the close spatial and temporal relationship between the mineralization and porphyritic granite we think the negative eu anomalies were inherited from the porphyritic granite and the positive ones from destruction of plagioclase of country rock during fluid rock interaction the variation of cathodeluminescence cl color of a single scheelite from red to blue and to yellow was likely associated with the increase of ree contents the scheelites hosted in the mesozoic porphyritic granite with negative eu anomalies formed in a primitive ore forming fluid whereas the scheelites hosted in neoproterozoic granite with positive eu anomalies precipitated in an evolved ore forming fluid the high nb ta lree contents and lree enriched ree patterns of scheelites from the shimensi deposit reveal a close relationship with magmatic hydrothermal fluids the scheelites from the shimensi deposit are characterized by low e nd t values 6 1 8 1 and unusually high and varied initial 87 sr 86 sr ratios 0 7230 0 7657 the e nd t values of scheelites are consistent with those of the mesozoic porphyritic granite but the sr isotopic ratios are significantly higher than those of the granites and importantly beyond the sr isotopic range of normal granites this suggests that the ore forming fluids and metals cannot be attributed to the mesozoic porphyritic granites alone the local neoproterozoic shuangqiaoshan group schists gneisses with high rb sr ratios and thus radiogenic sr isotopic compositions should have contributed to the ore forming fluids and metals particularly in a later stage of ore forming process by intense fluid rock interaction this is different from a commonly accepted model that the ore forming fluids and metals were exsolved exclusively from the granite plutons

mantle derived and crustal he and ar in the ore forming fluids of the xihuashan granite associated tungsten ore deposit south china abstract the xihuashan tungsten ore deposit in the central nanling region south china is a vein type hydrothermal deposit associated with the late jurassic granitoids that were previously thought to be the products of crustal anatexis alone in this study we use helium he and argon ar isotopes of fluid inclusions entrapped in pyrite and arsenopyrite to determine the origin of the ore forming fluids the 3he 4he ratios of the crushed fluid inclusions vary from 0 15 to 1 16 ra with a mean of 0 72 ra ra the atmospheric 3he 4he ratio of 1 4 10 6 indicating the presence of mantle derived noble gasses in the fluids the amounts of the mantle derived noble gasses are estimated to be between 2 and 17 the 40ar 36ar ratios of the fluid inclusions vary from 306 to 1023 with an average of 440 these ratios are significantly higher than the average crustal value indicating the presence of air saturated water in the volatiles released from the mineral separates the results from this study indicate that the associated coeval granitoids which is believed to provide the ore forming fluids during magma evolution are not the products of pure crustal melts mantle derived volatiles and heat was also involved in the genesis of the host granite pluton

inhomogeneous distribution of ree in scheelite and dynamics of archaean hydrothermal systems mt charlotte and drysdale gold deposits western australia scheelite is a widespread accessory mineral in hydrothermal gold deposits and its rare earth element ree patterns and nd and sr isotopic compositions can be used to constrain the path and origin of the mineralising fluids and the age of the hydrothermal activity micro analyses by laser ablation high resolution inductively coupled mass spectroscopy and cathodoluminescence imaging reveal a very inhomogeneous distribution of the ree in single scheelite grains from the mt charlotte and drysdale archaean gold deposits in western australia two end member ree patterns are distinguished type i is middle ree mree enriched with no or minor positive eu anomaly whereas type ii is flat or mree depleted with a strong positive eu anomaly the chemical inhomogeneity of these scheelites is related to oscillatory zoning involving type i and type ii patterns with zone widths varying from below 1 to 200 m intra sectorial growth discontinuities syn crystallisation brittle deformation and variations in the relative growth velocities of crystallographically equivalent faces suggest a complex crystallisation history under dynamic hydraulic conditions the co existence of mree enriched and mree depleted patterns within single scheelite crystals can be explained by the precipitation of a mineral which strongly partitions mree relative to light and heavy ree scheelite itself has such characteristics as does fluorapatite which is locally abundant and has ree contents similar to that of scheelite in this context the systematic increase of the eu anomaly between type i and type ii patterns is produced by the difference between the partition coefficients of eu2 and eu3 and not by fluid mixing or redox reactions consequently the high positive eu anomaly typical of scheelite from gold ores may not necessarily be inherited from the hydrothermal fluid but may reflect processes occurring during ore deposition this case study demonstrates that in hydrothermal systems characterised by low ree concentrations in the fluid and by the precipitation of a ree rich mineral which strongly fractionates the ree the ree patterns of such a mineral will be highly sensitive to the dynamics of the hydrothermal system

simulating the one dimensional structure of titan s upper atmosphere 1 formulation of the titan global ionosphere thermosphere model and benchmark simulations 1 we employ a newly developed navier stokes model the titan global ionosphere thermosphere model t gitm to address the one dimensional 1 d coupled composition dynamics and energetics of titan s upper atmosphere our main goals are to delineate the details of this new theoretical tool and to present benchmark calibration simulations compared against the ion neutral mass spectrometer inms neutral density measurements first we outline the key physical routines contained in t gitm and their computational formulation then we compare a series of model simulations against recent 1 d work by cui et al 2008 strobel 2008 2009 and yelle et al 2008 in order to provide a fiducial for calibrating this new model in paper 2 and a future paper we explore the uncertainties in our knowledge of titan s atmosphere between 500 km and 1000 km in order to determine how the present measurements constrain our theoretical understanding of atmospheric structures and processes

combined zircon and cassiterite u pb dating of the piaotang granite related tungsten tin deposit southern jiangxi tungsten district china abstract the large low grade piaotang w sn deposit in the southern jiangxi tungsten district of the eastern nanling range south china is related to a hidden granite pluton of jurassic age the magmatic hydrothermal system displays a zonation from an inner greisen zone to quartz veins and to peripheral veinlets stringers five floor zonation model most mineralization is in quartz veins with wolframite cassiterite the hidden granite pluton in underground exposures comprises three intrusive units i e biotite granite two mica granite and muscovite granite the latter unit is spatially associated with the w sn deposit combined la mc icp ms u pb dating of igneous zircon and la icp ms u pb dating of hydrothermal cassiterite are used to constrain the timing of granitic magmatism and hydrothermal mineralization zircon from the three granite units has a weighted average 206pb 238u age of 159 8 0 3 ma 2 mswd 0 3 the cathodoluminescence cl textures indicate that some of the cassiterite crystals from the wolframite cassiterite quartz vein system have growth zonations i e zone i in the core and zone ii in the rim dating on cassiterite zone ii yields a weighted average 206pb 238u age of 159 5 1 5 ma 2 mswd 0 4 i e the magmatic and hydrothermal systems are synchronous this confirms the classical model of granite related tin tungsten mineralization and is against the view of a broader time gap of 6 myr between granite magmatism and w sn mineralization which has been previously proposed for the southern jiangxi tungsten district the elevated trace element concentrations of zr u nb ta w and ti suggest that cassiterite zone ii formed in a high temperature quartz vein system related to the piaotang granite pluton

climatologies of nighttime upper thermospheric winds measured by ground based fabry perot interferometers during geomagnetically quiet conditions 1 local time latitudinal seasonal and solar cycle dependence 1 we analyze ground based fabry perot interferometer observations of upper thermospheric 250 km horizontal neutral winds derived from doppler shifts in the 630 0 nm red line nightglow the winds were measured over the following locations south pole 90 s halley 76 s 27 w arequipa 17 s 72 w arecibo 18 n 67 w millstone hill 43 n 72 w sondre stromfjord 67 n 51 w and thule 77 n 68 w we derive climatological quiet time kp 150 the seasonal dependence of the winds is generally annual but there are isolated cases in which a semiannual variation is observed within the austral winter winds measured from the south pole show a substantial intraseasonal variation only along longitudes directed toward the magnetic pole imf effects are described in a companion paper

dwm07 global empirical model of upper thermospheric storm induced disturbance winds 1 we present a global empirical disturbance wind model dwm07 that represents average geospace storm induced perturbations of upper thermospheric 200 600 km altitude neutral winds dwm07 depends on the following three parameters magnetic latitude magnetic local time and the 3 h kp geomagnetic activity index the latitude and local time dependences are represented by vector spherical harmonic functions up to degree 10 in latitude and order 3 in local time and the kp dependence is represented by quadratic b splines dwm07 is the storm time thermospheric component of the new horizontal wind model hwm07 which is described in a companion paper dwm07 is based on data from the wind imaging interferometer on board the upper atmosphere research satellite the wind and temperature spectrometer on board dynamics explorer 2 and seven ground based fabry perot interferometers the perturbation winds derived from the three data sets are in good mutual agreement under most conditions and the model captures most of the climatological variations evident in the data

vertical profiles of hcn hc3n and c2h2 in titan s atmosphere derived from cassini cirs data mid infrared limb spectra in the range 600 1400 cm 1 taken with the composite infrared spectrometer cirs on board the cassini spacecraft were used to determine vertical profiles of hcn hc3n c2h2 and temperature in titan s atmosphere both high 0 5 cm 1 and low 13 5 cm 1 spectral resolution data were used the 0 5 cm 1 data gave profiles at four latitudes and the 13 5 cm 1 data gave almost complete latitudinal coverage of the atmosphere both datasets were found to be consistent with each other high temperatures in the upper stratosphere and mesosphere were observed at titan s northern winter pole and were attributed to adiabatic heating in the subsiding branch of a meridional circulation cell on the other hand the lower stratosphere was much colder in the north than at the equator which can be explained by the lack of solar radiation and increased ir emission from volatile enriched air hc3n had a vertical profile consistent with previous ground based observations at southern and equatorial latitudes but was massively enriched near the north pole this can also be explained in terms of subsidence at the winter pole a boundary observed at 60 n between enriched and un enriched air is consistent with a confining polar vortex at 60 na nd hc 3n s short lifetime in the far north layers were observed in the hc3n profile that were reminiscent of haze layers observed by cassini s imaging cameras hcn was also enriched over the north pole which gives further evidence for subsidence however the atmospheric cross section obtained from 13 5 cm 1 data indicated a hcn enriched layer at 200 250 km extending into the southern hemisphere this could be interpreted as advection of polar enriched air towards the south by a meridional circulation cell this is observed for hcn but not for hc3n due to hcn s longer photochemical lifetime c2h2 appears to have a uniform abundance with altitude and is not significantly enriched in the north this is consistent with observations from previous cirs analysis that show increased abundances of nitriles and hydrocarbons but not c2h2 towards the north pole

wolframite deposition in a hydrothermal vein system the grey river tungsten prospect newfoundland canada mineralization in the grey river tungsten prospect newfoundland is contained within a sheared devonian k feldspar megacrystic granite and metamorphic rocks which are typical of the gneissic terrain of the gander zone the mineralization is genetically related to a suite of post tectonic highly differentiated alkali rich leucogranite dikes the tungsten bearing hydrothermal veins range from tensional veinlets to lodes containing several injections of quartz major composite lodes have greisen alteration envelopes which are characterized by enrichment in volatiles k 2 o al 2 o 3 rb li f heavy rare earth elements and w the heavy rare earth elements enrichment appears to be related to deposition of carbonate and fluorite in the greisen the mineralization is divided into four stages stage i characterized by quartz feldspar molybdenite veins stage ii composite lode formation consisting of five vein types in paragenetic order quartz bismuthinite iia quartz fe rich wolframite iib greisen iic quartz sulfide iid and quartz fe poor wolframite veins iie stage iii characterized by silver bearing quartz galena sphalerite veins and stage iv composed of fluorite calcite barite veins a spatial mineral zonation from south to north matches the temporal sequence outlined above with the exception of the stage iv veins which crosscut stage ii veins fluid inclusion data indicate a complex evolutionary history for the hydrothermal fluid the simultaneous trapping of co 2 rich and h 2 o rich fluid inclusions as well as solid inclusions of calcite in quartz of the quartz feldspar molybdenite and quartz bismuthinite vein types is evidence for the existence of a heterogeneous fluid during stage i and early stage ii mineralization fluid phase equilibria indicate that the inclusions were trapped at temperatures of 330 degrees to 360 degrees c and fluid pressures of less than 500 bars in composite lodes quartz sulfide and quartz fe poor wolframite veins were deposited in open spaces created by normal faulting these movements prompted rapid decrease in fluid pressure and temperature and caused retrograde boiling of the hydrothermal fluid at 200 bars and 300 degrees to 330 degrees c during deposition of quartz sulfide veins deposition of wolframite in quartz fe poor wolframite veins occurred at 270 degrees to 300 degrees c from an aqueous fluid of low salinity 0 5 wt nacl and low co 2 content 1 0 wt co 2 and after separation of a co 2 vapor phase by retrograde boiling isotopic and fluid inclusion data suggest that deposition of fe rich wolframite may have occurred at a slightly higher temperature 330 degrees c and from a fluid of higher co 2 content than the bulk of the wolframite which has an fe poor composition progressive co 2 loss from the hydrothermal fluid by immiscibility and retrograde boiling had a marked effect on the solution ph which shifted from 5 weakly acid to 6 weakly alkaline at 300 degrees to 350 degrees c during tungsten deposition thermodynamic data on the solubility of wolframite suggest that a ph increase would provide an effective mechanism for tungsten deposition and explain the variation in wolframite composition from fe rich to fe poor with time the association of hematite fe rich wolframite and muscovite in the greisen suggests high f sub o 2 10 super 20 10 super 30 conditions and is supported by eu behavior during alteration sulfides formed after tungsten deposition at temperatures less than 300 degrees c and under f sub s 2 conditions of less than 10 super 11 co 2 rich fluids are commonly associated with tungsten deposits from a variety of environments and the evidence from the grey river tungsten prospect shows that co 2 plays an important role in the transport and deposition of tungsten in the hydrothermal environment

cathodoluminescence and trace elements of scheelite constraints on ore forming processes of the dabaoshan porphyry mo w deposit south china abstract scheelite a good proxy to record the complex history of hydrothermal evolution has been investigated in the dabaoshan porphyry mo w deposit south china based on cathodoluminescence cl textures mineral paragenesis and chemical characterization three generations of scheelite were identified sch1 sch3 sch1 is disseminated in porphyry rocks or occasionally occurs in early quartz molybdenite veins it is cl dark and contains high concentrations of v sr mo nb ta and rare earth elements ree low u th ratios 0 37 mean and light ree lree enriched patterns with negative eu anomalies sch2 and sch3 mainly occur in late quartz pyrite scheelite chalcopyrite veins sch2 is cl bright and commonly rims sch1 and or is overgrown by late oscillatory sch3 compared with sch1 sch2 shows depletion in v sr mo nb and ta but slight enrichment in u and th and is characterized by middle ree mree enriched patterns with negative eu anomalies sch3 grains show reddish brown color under transmitted light and exhibit oscillatory zonation under cl sch3 has elevated concentrations of mn u up to 4484 ppm and th up to 18 8 ppm contents and high u th ratios 1175 mean chemical mapping reveals a negative correlation between u concentrations and cl intensity which is attributed to the radiation damage caused by the radioactive decay of u based on the ree patterns sch3 is subdivided into sch3a and sch3b sch3a shows mree enriched patterns with slight negative to positive eu anomalies while sch3b is lree enriched and shows gradual depletion in mree and hree with increasing positive eu anomalies in consecutive growth zones the dabaoshan porphyry and all generations of scheelites show similar y ho ratios indicating that ore forming fluids were mainly derived from the dabaoshan porphyry our results reveal that ree chiefly substitute into scheelite by the mechanism ca2 ree3 na while u substitutes for w into scheelite sch1 containing the highest concentrations of mo v nb and ta precipitates from the magmatic fluids at high temperature it inherits the lree enriched patterns and negative eu anomalies from the causative porphyry from early to late generations the gradual depletion of mo nb ta and v in scheelite is ascribed to the precipitation of molybdenite rutile and scheelite whereas the increasing concentrations of u and th in scheelite indicates the gradual enrichment of u and th in ore forming fluids the increasing u th ratios in scheelites may result from not only the differential solubility between u and th in fluids but also the preferential incorporation of u relative to th in scheelite compared with sch1 sch2 and sch3a are depleted in lree which is interpreted to reflect the precipitation of apatite sch3b with various ree patterns within single grains is interpreted as precipitation from a closed system accompanied by intermittent fluid replenishment this study demonstrates that ree patterns of scheelite are controlled by multiple factors including substitution mechanism fluid composition hydrothermal alteration precipitation of ree rich minerals and hydrothermal dynamics during scheelite growth the systematic variation of trace elements in scheelite suggests that scheelite chemistry can be used to monitor the evolution of ore forming fluids in the dabaoshan deposit

genetic types mineralization styles and geodynamic settings of mesozoic tungsten deposits in south china abstract south china hosts the most abundant and largest tungsten w deposits in the world being a famous w metallogenic region located at the eastern part of the south china block which was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic these w deposits were mainly formed during the mesozoic the w mineralization is dominanted by greisen quartz vein skarn and porphyry types all of which are genetically related to the evolution of highly fractionated granitoids four episodes of w mineralization are recognized 1 late triassic 230 210 ma in the central and western parts of south china 2 middle jurassic ca 170 ma to early cretaceous ca 140 ma in the interior of south china with the mineralization being concentrated in southern jiangxi province between 165 and 150 ma 3 early cretaceous 136 120 ma with deposits across south china and 4 late cretaceous 100 80 ma mainly in the southwestern parts of south china these four periods of mineralization are closely related to the closure of paleo tethys and subduction of the paleo pacific plate in the late triassic these two events caused local extensional environments facilitating emplacement of the peraluminous granitoids and formation of the w deposits in the middle jurassic break off of the subducting oceanic plate resulted in emplacement of highly fractionated granites in the nanling region later anticlockwise rotation of the paleo pacific plate created widespread s type granitoids and associated middle jurassic to early cretaceous w mineralization in the interior of south china since 136 ma rollback of the subducting pacific plate resulted in weak w mineralization across south china finally a change of direction in the retreating plate from se to ese resulted in intensive mineralization of the southwestern part of south china

direct dating of hydrothermal tungsten mineralization using in situ wolframite u pb chronology by laser ablation icp ms abstract the wolframite series may contain relatively high u and low common pb contents and thus has been used for direct u pb dating of hydrothermal w mineralization in this paper we present in situ laser ablation inductively coupled plasma mass spectrometry la icpms analysis of u pb isotopes and trace elements of wolframite crystals from the giant yaogangxian and piaotang w deposits in the extensive nanling metallogenic belt south china the objective of this work is to directly constrain the timing of hydrothermal w mineralization in these two deposits wolframite crystals from both deposits show textural evidence for two generations early wolframite wol 1 has higher fe and lower mn contents relative to those in the late wolframite wol 2 uranium is correlated positively with nb5 tetravalent ti sn zr hf and trivalent sc v y rees cations in all wolframite samples suggesting that the incorporation of u into wolframite is controlled by the coupled substitution mechanisms the early and late wolframite domains from the yaogangxian deposit yielded u pb ages of 159 1 2 0 ma 2 mswd 0 7 and 153 7 0 7 ma 2 mswd 0 5 respectively similarly two wolframite generations from the piaotang deposits yielded u pb ages of 159 5 1 3 ma 2 mswd 0 3 and 152 1 0 9 ma 2 mswd 0 5 the obtained u pb ages confirm two successive episodes of hydrothermal w mineralization at 159 ma and 153 ma in the yaogangxian and piaotang deposits this study demonstrates the potential of u pb dating of wolframite by la icpms and highlights its importance for directly dating hydrothermal ore forming processes