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

fluid inclusion petrography of sw england granites and its potential in mineral exploration fluid inclusions in granite quartz from sw england provide a record of the complex and protracted hydrothermal history of this important metallogenic province regional variations in terms of the different types of inclusions can be correlated on an inter pluton scale with both the texture of the host granite and the extent to which it is mineralized on an intra granite scale those areas where mineralization is particularly pronounced show a higher overall inclusion abundance than areas where little or no mineralization is known to occur the types of fluid inclusion most commonly related to sn w cu mineralization are halite free moderate temperature inclusions inclusions containing visible co2 at room temperature are restricted to two localities in sw england both of these contain stockwork vein swarm tungsten mineralization these regional fluid inclusion anomalies show that fluid inclusion petrography using a simple petrographic microscope has potential application in the field of mineral exploration

fluid inclusion characteristics and geological significance of the dajinshan w sn polymetallic deposit in yunfu guangdong province abstract the dajinshan tungsten tin polymetallic deposit is a quartz vein type ore deposit located in western guangdong province the ore bodies show a fairly simple shape and mainly occur as tungsten tin polymetallic bearing sulfide quartz veins including quartz vein quartz greisens and sulfide quartz veins and their distribution is spatially related to dajinshan granitoids the formation of the deposit experienced three stages a wolframite molybdenite quartz stage a wolframite cassiterite sulfide quartz stage and a fluorite calcite carbonate stage based on detailed petrographic observations we conducted microthermometric and raman microspectroscopic studies of fluid inclusions formed at different ore forming stages in the dajinshan tungsten tin polymetallic deposit identifying four dominant types of fluid inclusions aqueous two phase inclusions co2 bearing inclusions solid or daughter mineral bearing inclusions and gas rich inclusions the gas compositions of ore forming fluids in the dajinshan tungsten tin polymetallic deposit are mostly co2 ch4 and h2o the hydrogen oxygen and sulfur isotopic data imply that the ore forming fluids in the dajinshan tungsten tin polymetallic deposit were mainly derived from magmatic fluids mixed with meteoric water in the ore formation process these results indicate that the fluid mixing and boiling led to the decomposition of the metal complex in ore forming fluids and ore deposition

subduction collision and exhumation in the ultrahigh pressure qinling dabie orogen c abstract high pressure metamorphism and ophiolite emplacement songshugou ophiolite attended suturing of the yangtze craton to rodinia during the c l o ga grenvillian oro geny the qinling microcontinent then rifted from the yangtze craton at c 750ma the erlangping intraoceanic arc formed in the early ordovician was emplaced onto the qinling microcontinent in the ordovician silurian and then both units were accreted to the sino

groundwater flow and residence times below a meso tidal high energy beach a model based analyses of salinity patterns and 3h 3he groundwater ages abstract in this study 3h 3he ages in the intertidal zone based on both field measurements and numerical simulations are presented to provide insights into the flow and transport behavior within the subterranean estuary of a meso tidal high energy beach in a systematic modelling approach important hydrogeological parameters dispersivity hydraulic conductivity and fresh groundwater flux were varied in a cross shore transect at a beach on spiekeroog island in north western germany both measured and simulated salinity and age distribution within the intertidal zone suggest the existence of two at least temporally occurring saltwater recirculation cells accompanied by two fresh discharge location this is in contrast to the state of the art concept of a ste under tidal influence and is caused by a runnel and ridge system at the study site which is a rather wide spread type of beach morphology with topographical highs and interfering lows in the intertidal zone residence times within the two saline plumes were between weeks and several months freshwater from the island s freshwater lens resided up to 18 years in the brackish beach aquifer before exfiltrating at the discharge points field measurements confirmed the discharge of decade old water at the discharge points model results were highly dependent on the tested model parameters a change between a one and two plume system as well as overlapping conditions at the study site dependent on the change in beach topography are likely

mineral paragenesis fluid inclusions h o isotopes and ore forming processes of the giant dahutang w cu mo deposit south china abstract the newly discovered giant dahutang w cu mo deposit in the central part of the jiangnan orogen hosts an estimated resource of 1 1 million tons mt of wo3 plus a proven resource of 0 65 mt cu and 0 08 mt mo the dahutang deposit is temporally and spatially associated with the late mesozoic s type granites emplaced into the neoproterozoic jiuling granodiorite batholith and the shuangqiaoshan group based on petrographic observations eight hydrothermal alteration mineralization stages have been recognized comprising pegmatitic stage i potassic alteration stage ii albite alteration stage iii greisenization and main mineralization stage iv polymetallic sulfide mineralization stage v late scheelite mineralization stage vi carbonate alteration stage vii and supergene alteration stage viii stage iv can be further divided into the early greisenization stage iv a the main wolframite mineralization stage iv b and the main scheelite mineralization stage iv c fluid inclusion and h o isotope analyses on nine stage iv to vii ore gangue minerals wolframite cassiterite scheelite sphalerite fluorapatite fluorite quartz calcite and chlorite suggest the presence of an early w and a late cu mo ore forming fluid system the early ore forming fluids belong to a medium to high temperature 200 420 c low salinity h2o nacl cacl2 system this primary magmatic hydrothermal fluid 18ofluid 5 4 to 8 8 and d 102 to 75 was likely exsolved from the late jurassic granites at dahutang wolframite and scheelite coexist closely with fluorapatite and fluorite respectively indicating that the volatile rich fluids at dahutang were also rich in tungsten fluorine and phosphorous tungsten was likely transported as tungstate species e g wo42 and hwo4 oxygen fluorine complexes e g wo2f4 2 wo3f2 2 and phosphorous heteropolytungstate e g p w12o40 3 in the fluids fluorapatite and wolframite may have precipitated first when the temperature dropped from 400 to 320 c along with ph increase at an estimated depth of 7 8 km this was likely followed by the extensive scheelite mineralization with fluorite precipitation that formed huge disseminated veinlet type w orebodies when the temperature further dropped to 200 c along with ph increase after the w mineralization extensive cu mo polymetallic mineralization and the associated sericite chlorite alterations may have formed by the granite porphyry and or muscovite granite emplacement the late ore forming fluids belong to a medium to high temperature 200 360 c low salinity h2o nacl cacl2 system molybdenum was likely transported mainly as mo complexes e g h2moo4 moo42 and copper as cu cl complexes molybdenite and chalcopyrite may have begun to precipitate when the fluids ascended and the temperature dropped to 330 c meteoric water incursion may have then occurred 18ofluid 1 9 6 9 and d 99 to 68 and further cooled the fluid system to 250 c forming large cu mo orebodies

tide induced seawater groundwater circulation in shallow beach aquifers summary in this paper we investigated the tide induced seawater groundwater circulation in shallow beach aquifers using the finite element model marun the numerical solutions were generalized using a dimensionless formulation from a dimensionless tidal period and a dimensionless beach slope of 10 we obtained results that apply to a wide range of beach permeabilities from 10 4 m s to 10 3 m s beach slopes from 3 16 to 31 6 tidal amplitude 0 3 m 2 m and period diurnal or semidiurnal the numerical simulations demonstrated the following the maximum darcy velocity always occurs at the intersection of the watertable and the beach surface the offshore beach groundwater is almost stagnant compared with the onshore groundwater flow which may explain the previous observations that the major portion of the seaward groundwater seepage usually occurs in the shallow part of the submerged beach the outflow from the seepage face accounts for 41 97 average 55 of the outflow from the intertidal zone the amount of seawater infiltrating into the intertidal zone in a tidal cycle increases with the beach permeability and decreases when the inland recharge increases and ranges from 35 5 m 3 yr 1 m 1 to 505 8 m 3 yr 1 m 1 for all the cases considered smaller beach slopes smaller inland freshwater recharges and or greater beach permeability lead to larger saltwater plumes in the intertidal zone of the beach the results are in line with the existing results of field observations and numerical simulations by previous researchers a 2008 elsevier b v all rights reserved

ultrahigh pressure metamorphic rocks from the chinese continental scientific drilling project i petrology and geochemistry of the main hole 0 2 050 m the main hole mh of the chinese continental scientific drilling project ccsd in southern sulu has penetrated into an ultrahigh pressure uhp metamorphic rock slice which consists of orthogneiss paragneiss eclogite ultramafic rock and minor schist recovered eclogites have a uhp metamorphic mineral assemblage of garnet omphacite rutile phengite kyanite coesite epidote ultramafic rocks contain garnet olivine clinopyroxene orthopyroxene ti clinohumite phlogopite gneisses and schists contain an amphibolite facies paragenesis but their zircons have coesite garnet omphacite or jadeite and phengite inclusions indicating that eclogites and gneisses have been subjected to in situ uhp metamorphism using available geothermobarometers p t estimates of 3 1 4 4 gpa and 678 816 c for eclogites were obtained if surface outcrops and neighboring shallow drill holes are considered together we suggest that a huge supracrustal rock slab 50 km long 100 km wide 5 km deep was subducted to a depth 100 km and then exhumed to the surface the depth interval 0 2 050 m of the ccsd mh can be divided into six lithological units unit 1 consists of alternating layers of quartz rich and rutile rich eclogites with thin interlayers of gneiss and schist eclogites of unit 1 are characterized by nb ta sr and ti depletions low mg number and general lree enrichment unit 2 comprises rutile and ilmenite rich eclogite and minor normal eclogite and is characterized by high tio2 total fe v co and sr and very low sio2 alkali zr ba nb ta and total ree contents and lree depleted ree patterns with slightly positive eu anomalies unit 3 contains ultramafic rock and minor mgo rich eclogite protoliths of uhp rocks from units 1 2 and 3 represent a layered mafic to ultramafic intrusion at crustal depth units 4 and 6 consist of interlayered eclogite and paragneiss the eclogites are characterized by th u nb ta and ti depletion and k enrichment and lree enriched ree patterns paragneisses show nb ta sr and ti depletions and lree enriched ree patterns occasionally with slightly negative eu anomalies indicating that their protoliths represent metamorphic supracrustal series unit 5 consists mainly of orthogneisses showing distinct nb ta sr and ti depletions and lree enriched ree patterns with pronounced negative eu anomalies suggesting granitic protoliths in conclusion it is proposed that the southern sulu uhp belt consists of a series of meta supracrustal rocks a layered mafic ultramafic complex and granites

tracking the prograde p t path of precambrian eclogite using ti in quartz and zr in rutile geothermobarometry a fe ti rich garnet clinopyroxene and quartz eclogite sample from the 1 0 ga sveconorwegian orogen sw sweden contains abundant quartz rutile and zircon in distinct micro textural sites garnet core garnet rim and matrix constituting an ideal case for investigation of the behavior of zr in rutile and ti in quartz at high pressure and temperature a p t path peaking at 16 5 19 kbar and 850 900 c has been constrained independently for the same rock by pseudosection modelling input pressures from this model were used for trace element geothermometry of each garnet micro textural domain trace element thermo baro metry based on in situ secondary ion mass spectrometry analyses of ti contents in quartz and zr contents in rutile yields p t estimates of progressive crystallization of quartz and rutile along the prograde metamorphic path for inclusions in the garnet cores zr in rutile geothermometry yields 700 715 c and ti in quartz 620 640 c at 7 kbar for inclusions in the garnet rims temperature estimates are 760 790 c zr in rutile and 740 920 c ti in quartz at 12 18 kbar finally matrix rutile records 775 800 c and locally 900 c and quartz records temperatures up to 900 c at 18 kbar ti in quartz estimates for the metamorphic peak inclusions in the garnet rims and matrix conform to the pseudosection but appear too low for the early prograde stage garnet cores possibly due to lack of equilibrium at t 700 c the pseudosection shows that rutile was produced by continuous ilmenite breakdown during the early stages of prograde metamorphism a reaction that was completed at 730 c rutile grains in the garnet rims and the matrix grew subsequently larger by recrystallization of previously produced rutile however recrystallized rutile does not predominantly record peak temperatures but instead yield 745 840 c between 12 and 18 kbar in the pseudosection this temperature range broadly coincides with a stage during which ti bearing hornblende was consumed and clinopyroxene produced i e dehydration the zr contents thus appear to reflect the last stage of efficient rutile recrystallization catalysed by fluids released by the dehydration of hornblende preceding the metamorphic peak concurrently combination of the isopleths for ti content in quartz and zr content in rutile i e independent from pseudosection modelling yields pressure and temperature conditions in almost perfect agreement with the p t path as deduced from the pseudosection the variation in ti concentration in quartz is small regardless of crystal size and the ti in quartz geothermometer provides both precise and accurate peak temperatures of 875 920 c without a significant diffusional reequilibration the lack of significant ti diffusion in quartz is consistent with an inferred short residence time at high temperature this study illustrates that zr in rutile and ti in quartz geothermobarometry can robustly constrain prograde p t conditions and yield further insights into recrystallization processes at high temperature the combination of these methods and integration of the results with pseudosection modelling is a versatile tool for investigating the petrologic history of high grade rocks less

tidal influence on seawater intrusion in unconfined coastal aquifers studies of seawater intrusion in unconfined coastal aquifers typically neglect oceanic oscillations such as tides and assume a static seaward boundary condition defined by the mean sea level laboratory experiments and numerical simulations were conducted to investigate the influence of tidal oscillations on the behavior of the saltwater wedge for the conditions examined the experiments showed that an upper saline plume formed in the intertidal zone due to tide induced seawater circulation the presence of the upper saline plume shifted the fresh groundwater discharge zone seaward to the low tide mark and restricted the intrusion of the saltwater wedge the overall seawater intrusion extent as indicated by the wedge toe location was reduced significantly compared with the nontidal static case results from the numerical model matched these experimental observations and further demonstrated the similar type of tidal influence on the saltwater wedge in a field scale aquifer system the glover 1959 solution for predicting the saltwater wedge was modified to account for the tidal effect by including the tide induced circulation as a recharge to the aquifer the findings highlight the significant impact of the tide in modulating the groundwater behavior and salt freshwater dynamics not only within but also landward of the intertidal zone

petrological and zircon evidence for anatexis of uhp quartzite during continental collision in the sulu orogen petrological evidence is provided for anatexis of ultrahigh pressure uhp metamorphic quartzite in the sulu orogen some feldspar grains exhibit elongated highly cuspate shapes or occur as interstitial cuspate phases constituting interconnected networks along grain boundaries elongated veinlets composed of plagioclase quartz k feldspar also occur in grain boundaries these features provide compelling evidence for anatexis of the uhp quartzite zircon grains from impure quartzite are all metamorphic growth with highly irregular shape they contain inclusions of coesite jadeite rutile and lower pressure minerals including multiphase solid inclusions that are composed of two or more phases of muscovite quartz k feldspar and plagioclase all zircon grains exhibit steep ree patterns similar u pb ages and hf isotope compositions with a weighted mean of 218 2 ma most grains have similar 18o values of 0 6 to 0 1 but a few fall in the range 5 2 to 4 3 thus these grains would have grown from anatectic melts at various pressures zircon o isotope differences indicate that anatectic melts were derived from different sources with contrasting o isotopes but similar hf isotopes that is one from the quartzite itself and the other probably from the country rock granitic gneiss zircon grains from pure quartzite contain relict magmatic cores and significant metamorphic overgrowths domains that contain eclogite facies minerals exhibit flat hree patterns no eu anomalies and concordant u pb ages of c 220 ma similar u pb ages are also obtained for domains that contain lower pressure minerals and exhibit steep ree patterns and marked negative eu anomalies these observations indicate that zircon records subsolidus overgrowth at eclogite facies conditions but suprasolidus growth at lower pressures zircon enclosed by garnet gave consistent u pb ages of c 214 ma such garnet is interpreted as a peritectic product of the anatectic reaction that involves felsic minerals and possibly amphibole and titanite the ree patterns of epidote and titanite also record multistage growth and metasomatism by anatectic melts therefore the anatexis of uhp metamorphic rocks is evident during continental collision in the triassic

copper deposition during quartz dissolution by cooling magmatic hydrothermal fluids the bingham porphyry abstract scanning electron microscope cathodoluminescence imaging is used to map successive generations of fluid inclusions in texturally complex quartz veinlets representing the main stage of ore metal introduction into the porphyry cu au mo deposit at bingham utah following conventional fluid inclusion microthermometry laser ablation inductively coupled plasma mass spectrometry la icpms is applied to quantify copper and other major and trace element concentrations in the evolving fluid with the aim of identifying the ore forming processes textures visible in cathodoluminescence consistently show that the bulk of vein quartz q1 characterized by bright luminescence crystallized early in the vein history cu fe sulfides are precipitated later in these veins in a microfracture network finally filled with a second generation of dull luminescing q2 quartz mapping of brine and vapor inclusion assemblages in these successive quartz generations in combination with la icpms microanalysis shows that the fluids trapped before and after cu fe sulfide precipitation are very similar with respect to their major and minor element composition except for copper copper concentrations in inclusions associated with ore formation drop by two orders of magnitude in a tight pressure temperature interval between 21 and 14 mpa and 425 350 c several hundred degrees below the temperature of fluid exsolution from the magma copper deposition occurs within a limited p t region in which sulfide solubility shows strong normal temperature dependence while quartz solubility is retrograde this permits copper sulfide deposition while secondary vein permeability is generated by quartz dissolution the brittle to ductile transition of the quartz feldspar rich host rocks occurs in the same temperature range which further enhances vein reactivation and promotes cooling and expansion of fluids ascending across the transition from lithostatic to hydrostatic conditions

comparison of fluid inclusions in coexisting cogenetic wolframite cassiterite and quartz from st michael s mount and cligga head cornwall england abstract the st michael s mount occurrence and cligga head deposit are typical examples of w sn mineralization in the cornwall district in s w england mineralization consists of quartz wolframite cassiterite and various amounts of base metal sulfides in sheeted veins associated alteration includes greisenization and argillization in both areas textural evidence for contemporaneous deposition of the ore minerals wolframite and cassiterite with quartz is generally ambiguous previous studies state that the quartz and wolframite are intergrown but do not address the genetic relation between them in this study microthermometry was performed on fluid inclusions in wolframite cassiterite and quartz the inclusions in wolframite were observed using an infrared microscope and those in cassiterite and quartz were observed with visible light at st michael s mount th values for primary inclusions in quartz average 311 c and in wolframite average 369 c salinities average 7 3 eq wt nacl in quartz and 4 2 eq wt nacl in wolframite at cligga head the average th values for primary inclusions in the various minerals are cassiterite 352 c wolframite 324 c and quartz 295 c fluid inclusion salinities average 5 3 eq wt nacl in cassiterite 3 9 eq wt in wolframite and 6 0 eq wt nacl in quartz the magnitude of the changes in th measurements between minerals cannot be accounted for by post trapping changes and therefore must be due to actual differences in the temperatures of deposition these data suggest that the ore minerals wolframite and cassiterite were deposited earlier than the associated quartz even though conclusive textural evidence is lacking wolframite and cassiterite were deposited at about the same temperature at st michael s mount but at cligga head cassiterite was deposited at higher temperatures than wolframite certainly in these areas the gangue minerals do not provide reasonable estimates of the depositional conditions of the ore minerals even though they are intimately intergrown

multiphase solid inclusions in zoisite bearing eclogite evidence for partial melting of ultrahigh pressure metamorphic rocks during continental collision abstract multiphase solid ms inclusions in both garnet and omphacite were investigated for zoisite bearing eclogite from the ultrahigh pressure uhp metamorphic zone in the sulu orogen the results provide petrological evidence for local anatexis during exhumation of deeply subducted continental crust there are three types of ms inclusions 1 plagioclase quartz 2 plagioclase quartz k feldspar and 3 barite plagioclase k feldspar zoisite epidote the host minerals mostly exhibit radial fractures surrounding the ms inclusions the first and second types of ms inclusions were analyzed for their bulk compositions yielding high sio 2 and na 2 o but very low feo mgo tio 2 with variable k 2 o for the second type trace element analyses of representative ms inclusions yield generally very low concentrations except such large ion lithophile elements as sr ba and rb these features suggest different origins for the three types of ms inclusions the first type of ms inclusions would be primarily derived from dehydration melting of paragonite whereas the second type of ms inclusions would be derived from dehydration melting of both paragonite and phengite the third type of ms inclusion may result from the interaction between metamorphic fluid and host mineral in view of the occurrence of barite as a filling phase in the fractures of host minerals zoisite breakdown is also indicated by its highly cuspate shape in coexistence with quartz providing components for growth of garnet during the exhumation therefore the anatexis of zoisite bearing uhp eclogite is primarily driven by the breakdown of hydrous minerals such as phengite and paragonite the major and trace element compositions of ms inclusions in the eclogites mainly depend on the species of hydrous minerals involved in the mineralogical reactions of dehydration melting in subduction channel

gold and silver metallogeny of the south china fold belt a consequence of multiple mineralizing events abstract the south china fold belt is part of the south china block that is interpreted to be the result of multiple tectonic and magmatic events that formed a collage of accreted proterozoic and phanerozoic terranes the jurassic to early cretaceous yanshanian period 180 90 ma a time of major tectono thermal events that affected much of eastern and southeastern china is of great metallogenic importance in the fold belt this period is linked to subduction of the pacific plate beneath the eurasian continent and is manifested by voluminous volcano plutonic activity of predominantly calc alkaline affinity the distribution of gold and silver deposits in the south china fold belt indicates the presence of two distinct metallogenic provinces a region of basement uplifts which are controlled by shear zones and form neoproterozoic inliers of metamorphosed iron rich rock types defines the first province in this province orogenic lodes and volcanic related epithermal deposits represent the more significant precious metal mineralization the second province is essentially confined to a belt of yanshanian felsic intermediate volcanic and subvolcanic rocks that extends along most of the southeastern china coast in an area known as the coastal volcanic belt deposits in the coastal volcanic belt are silver and or copper rich volcanic hosted and epithermal in character the precious metal metallogeny of the south china fold belt is interpreted to have developed in at least three stages one as a result of collision events during the caledonian orogeny ca 400 ma the second during the indosinian orogeny ca 200 ma and the third during or soon after the formation of the yanshanian magmatic belt yanshanian orogeny 180 90 ma the latter was responsible for a hydrothermal event that affected large sections of the belt and its proterozoic substrate this may have resulted in the redistribution and enrichment of precious metals from preexisting orogenic gold lodes in neoproterozoic basement rocks which are now exposed as windows in zones of tectonic uplift the yanshanian hydrothermal activity was particularly widespread in the coastal volcanic belt and resulted in the formation of both low and high sulfidation epithermal gold and silver and locally copper and other base metal mineralization it is suggested that the coastal volcanic belt has greater potential for world class epithermal and porphyry deposits than previously realised

tidal influence on behaviour of a coastal aquifer adjacent to a low relief estuary the tidal influence on groundwater hydrodynamics salt water intrusion and submarine groundwater discharge from coastal estuarine aquifers is poorly quantified for systems with a mildly sloping beach in contrast to the case where a vertical beach face is assumed we investigated the effect of beach slope for a coastal aquifer adjacent to a low relief estuary where industrial waste was emplaced over the aquifer the waste was suspected to discharge leachate towards the estuary field observations at various locations showed that tidally induced groundwater head fluctuations were skewed temporally frequency analysis suggested that the fluctuation amplitudes decreased exponentially and the phase lags increased linearly for the primary tidal signals as they propagated inland salinisation zones were observed in the bottom part of the estuary and near the beach surface flow and transport processes in a cross section perpendicular to the estuary were simulated using seawat 2000 which is capable of depicting density dependent flow and multi species transport the simulations showed that the modelled water table fluctuations were in good agreement with the monitored data further simulations were conducted to gain insight into the effects of beach slope in particular the limiting case of a vertical beach face was considered the simulations showed that density difference and tidal forcing drive a more complex hydrodynamic pattern for the mildly sloping beach than the vertical beach as well as a profound asymmetry in tidally induced water table fluctuations and enhanced salt water intrusion the simulation results also indicated that contaminant transport from the aquifer to the estuary was affected by the tide where for the mildly sloping beach the tide tended to intensify the vertical mass exchange in the vicinity of the shoreline

fluid evolution of the qiman tagh w sn ore belt east kunlun orogen nw china abstract the qiman tagh w sn ore belt is located in the westernmost sector of the east kunlun orogen nw china it has been recognized as a unique w sn belt that formed in the early paleozoic and related to closure of the proto tethys to understand the evolution of ore forming fluids and its relationship with the tectonic setting of east kunlun orogen we report the results obtained from fluid inclusion and h o isotopic studies of ores and quartz veins for the qiman tagh w sn ore belt mineralization in qiman tagh includes four stages characterized by quartz cassiterite wolframite assemblage stage 1 quartz scheelite assemblage stage 2 quartz polymetallic sulfides stage 3 and ore barren veins stage 4 the former two stages are conducive to mineralization while the latter two stages are less important the fluid inclusions are distinguished between co 2 h 2 o c type and nacl h 2 o w type in composition containing a trace of ch 4 n 2 c 2 h 6 so 2 and co 3 2 cassiterite and quartz in stage 1 instead of wolframite contain a great deal of c type inclusions all inclusions in minerals of stage 1 yield homogenization temperatures of 230 1 384 1 c peaking at 310 320 c with salinities lower than 14 76 wt nacl equiv and bulk densities of 0 63 0 89 g cm 3 the stage 2 minerals contain both two types of inclusions yielding homogenization temperatures of 183 4 335 9 c peaking at 280 290 c with salinities lower than 14 53 wt nacl equiv and bulk densities of 0 66 0 97 g cm 3 fluid inclusions in minerals of stages 3 and 4 are mainly w type and homogenized at temperatures of 140 6 277 6 c peaking 210 220 c and 116 9 255 1 c peaking 160 170 c respectively the h o isotopic systematics shows that the fluids were dominated by magmatic water in stages 1 and 2 but by meteoric water in stages 3 and 4 integrating all the geological and geochemical data we conclude that the fluids forming the qiman tagh w sn ore belt evolved from granite derived co 2 rich and reducing to meteoric water dominated co 2 poor and oxidizing fluid immiscibility cooling and interaction with rocks are main mechanisms for metallic deposition

tide induced recirculation across the aquifer ocean interface a parametric analysis is conducted to examine the influence of tides inland hydraulic conditions and aquifer properties on the rate of tide induced seawater recirculation through the nearshore aquifer understanding such influence is crucial for accurate prediction of subsurface chemical fluxes to coastal waters via groundwater discharge the analysis is based on numerical simulations of density dependent groundwater flow in a coastal aquifer subject to tidal oscillations across a sloping beach face the results reveal that the amplitude of tidal oscillations and the inland hydraulic gradient are the primary parameters controlling the tide induced recirculation rates significant tidal exchange is expected when the ratio of tidal to inland forcing is large the horizontal tidal shoreline excursion and aquifer depth both display asymptotic behavior influencing recirculation rates for only small values where the exchange process is limited by the potential for infiltration and shallowness of the aquifer respectively the analysis also indicates that tidal effects increase density driven recirculation rates due to enhanced convective flow within the saltwater wedge

mesozoic magmatism and granitic dome in the wugongshan massif jiangxi province and their genetical relationship to the tectonic events in southeast china abstract in se china a mesozoic granitic dome coeval to extensional tectonics is exposed in the wugongshan massif its center is occupied by mesozoic granitoids and granitic gneisses and the e w trending late paleozoic mesozoic pingxiang and anfu basins are located along its northern and southern sides respectively in this paper the petrological geochemical major incompatible and rare earth elements and isotopic characteristics of the granitoids and granitic gneisses of this dome allow us to constrain their geodynamic evolution the wugongshan mesozoic k feldspar enriched granitoids consist of six granitic bodies and lie within a paleozoic metamorphic basement the caledonian shanzhuang granodiorite containing some dioritic enclaves occurs in the study area and is a calc alkaline type granodiorite characterised by lower sio2 and composed of andesine biotite quartz hornblende magnetite and sphene the mesozoic granitoids either indosinian plutons or yanshanian bodies show a geochemical affinity of peraluminous s type granite having higher sio2 k2o contents al k na 2ca enriched in rb th and depleted in eu they also exhibit lree enriched patterns and marked negative eu anomalies the yanshanian plutons also contain characteristic minerals such as sillimanite garnet and monazite the wugongshan mesozoic granitoids have higher isr values 0 70981 0 72885 and lower end t 10 6 to 14 7 an average of 12 6 than those of the early paleozoic shanzhuang granodiorite the mesozoic granitoids were likely derived from ancient sedimentary rocks by partial melting the wugongshan mesozoic granitoids contain three petrological zones that is an early cretaceous massive granitic zone in the core zone i a foliated granitic zone zone ii and a triassic granitic gneissic zone in the outer rim zone iii the petrological and geochemical features of massive granitoids zone i are similar to those of foliated granites zone ii and of granitic gneisses zone iii in this mesozoic dome moreover geometric and kinematic features within the ductile parts units 2 and 3 are also similar to those within the brittle part unit 1 of the dome all these features show that the geologic evolution of the wugongshan doming is a continuous process lasting from triassic to early cretaceous time published 40ar 39ar and k ar ages in the wugongshan mesozoic granitic rocks fall into two major age fields corresponding to two geodynamic events of intracontinental deformation and magmatic activity the first tectonothermal event dated at 226 259 ma on the granitic gneisses in the outer rim of dome can be linked to indosinian collision between the south china plate and the north china plate during triassic time the second event took place during the early yanshanian dated at 180 120 ma on the granites of the core of dome and are responsible for final doming of the wugongshan plutons this event may be related to a westward subduction of the paleo pacific oceanic plate under the se china continent during late jurassic early cretaceous time

the origin of the tongkeng changpo tin deposit dachang metal district guangxi china clues from fluid inclusions and he isotope systematics tongkeng changpo is the largest tin deposit within the giant dachang polymetallic tin ore field in guangxi southern china which is part of a large skarn system associated with cretaceous granitoids the tongkeng changpo mineralization consists of veins and stockworks in the upper levels and replacement stratiform orebodies mantos at lower levels based on textural relationships three major mineralizing stages can be recognized stage i with cassiterite sulphides stannite tourmaline and quartz stage ii with cassiterite sulphides sulphosalts quartz and calcite and stage iii with calcite as the main phase the study of fluid inclusions has shown that there are two main fluid types co2 and nacl h2o homogenization temperatures are 270 to 365 c 210 to 240 c and 140 to 190 c for stages i ii and iii respectively salinities range from 1 to 7 wt nacl equiv in the early ore stage and 3 to 10 wt nacl equiv in the late stages laser raman spectroscopy indicates that the inclusion fluids in stages i and ii were of carbono aqueous composition with minor amounts of ch4 and h2s whereas those in stage iii were aqueous helium isotopic analyses of inclusion fluids indicate that the 3he 4he ratios in the ore veins are in between 1 2 to 2 9 ra ra 1 4 10 6 modern atmospheric ratio and range from 1 6 to 2 5 ra in the stratiform orebodies this range of 3he 4he ratios is significantly higher than that of crustal fluids 0 01 0 05 ra the similar characteristics of fluid inclusions and their he isotopic composition as well as age constraints indicate that the ore veins and stratiform orebodies of the tongkeng changpo deposit formed from the same hydrothermal system likely related to granite intrusions of the mesozoic yanshanian tectono thermal event in addition the high r ra ratios indicate a mantle contribution in the ore fluids

geochronology and isotopic character of ultrahigh pressure metamorphism with implications for collision of the sino korean and yangtze cratons central china the collision zone between the sino korean and yangtze cratons in central china is marked by subduction related metamorphic rocks composed of crustal protoliths these range in metamorphic grade from ultrahigh pressure eclogite to low greenschist facies the paragenesis of the ultrahigh pressure rocks coesite and diamond bearing indicates subduction to depths greater than 120 km as a result of continental collision despite extreme metamorphic conditions zircons have not undergone pb loss but rather illustrate two periods of growth crystallization between 700 and 800 ma and ultrahigh pressure metamorphism at 218 2 5 ma previous studies have predicted a time transgressive collision but age data presented in this study indicate that the collision was approximately coeval along the length of the suture u pb zircon ages of these ultrahigh pressure metamorphic rocks are 218 4 2 5 ma and 217 1 8 7 ma for the dabie mountains and shandong peninsula respectively the similar ages imply that the tan lu fault which offsets the ultrahigh pressure metamorphic rocks is a secondary feature not related to collision or subduction whole rock isotopic data show that both rb sr and u pb were open systems during metamorphism but that sm nd probably remained closed nd initial isotopes display crustal signatures indicating that the crust subducted as a coherent slab rather than becoming intercalated with mantle material at depth sm nd data in conjunction with u pb zircon dating indicate that the ultrahigh pressure rocks are not typical yangtze craton basement 2 9 ga but that they originally crystallized in a rift environment between 700 and 800 ma discrepancies between 40ar 39ar plateaus sm nd isochrons and u pb zircon ages render calculation of a p t t path unrealistic

near infrared observation and microthermometry of pyrite hosted fluid inclusions pyrite occurs in many types of ore deposits although opaque to visible light some pyrite samples are sufficiently transparent in infrared light to reveal fluid inclusions and other internal features for a reconnaissance study 166 doubly polished thick sections of pyrite from 64 deposits worldwide were examined using an infrared microscope pyrite transparency varies between deposits with low temperature deposits showing the least transparency many samples transparent at room temperature gradually became opaque upon heating pyrite fourier transform infrared ftir spectra taken in the temperature range from 28 to 400 c demonstrate that the degradation of pyrite transparency with an increase in temperature is caused by a gradual shift of the main absorption edge of pyrite towards longer wavelengths recognizable fluid inclusions in pyrite are generally scarcer than fluid inclusions in quartz and microthermometric measurements are more difficult to obtain in the 64 occurrences studied about one quarter contained transparent fluid inclusions of the 37 analyzed fluid inclusions about two thirds yielded salinity measurements and about one quarter yielded homogenization temperatures microthermometric analysis on pyrite hosted fluid inclusions is possible however workable fluid inclusions are limited in occurrence

indium mineralisation in sw england host parageneses and mineralogical relations abstract the sw england ore region contains significant amounts of indium in in early permian granite related skarn and lode parageneses and to a lesser extent triassic epithermal crosscourse veins ore parageneses that predate granite emplacement devonian and lower carboniferous sedimentary exhalative and vein parageneses are largely devoid of in cadmium cd and gallium ga occur widely in all sulphide bearing parageneses across the region with sphalerite concentrations locally reaching 1 74 wt cd and 1750 ppm ga indium displays a strong affinity to sulphide bearing magmatic hydrothermal parageneses it occurs in silicate sulphide skarns polymetallic sulphide lodes and sulphide bearing portions of greisen bordered sheeted vein systems and quartz tourmaline lodes across the region magnetite silicate skarns and quartz tourmaline lodes that are devoid of sulphide in contrast were comparatively unfavourable for in precipitation the highest in concentrations are found in mineral lodes associated with the carnmenellis and st agnes granites which are the districts that had the highest historical production of sn total in concentrations in these areas locally exceed 430 ppm while concentrations elsewhere are systematically below 200 ppm the principal in hosts are chalcopyrite sphalerite and stannite group minerals with local concentrations within cassiterite and tennantite surprisingly chalcopyrite accounts for the majority of the in budget throughout the region although concentrations are highest in sphalerite and stannite group minerals sphalerite locally contains up to 1 42 wt in chalcopyrite has up to 2200 ppm and stannite group minerals up to 6800 ppm no in was detected in lollingite arsenopyrite rutile haematite magnetite tourmaline biotite chlorite galena bornite chalcocite or pyrrhotite scattered concentrations in pyrite relate to impurities rather than incorporation by solid solution roquesite and possibly dzhalindite or native in formed locally where in bearing chalcopyrite or sphalerite has been replaced by bornite and quartz the in partitioning between sphalerite and chalcopyrite varies broadly between 1 1 and 10 1 sporadic in was included in triassic crosscourse veins as a result of interactions between migrating cacl2 rich basinal brines and earlier formed granite related parageneses the interactions involved at least two distinct components 1 incorporation of clasts of magmatic hydrothermal veins in crosscourse veins during faulting and 2 dissolution and re precipitation of magmatic hydrothermal vein minerals in crosscourse fluids local concentrations reach 140 ppm in the magmatic hydrothermal parageneses in sw england are comparable to the south china tin belt mount pleasant as well as erzgebirge krusne hory magmatic hydrothermal fluids associated with peraluminous granites have developed a variety of skarn greisen lode and veins parageneses by interactions with their host rocks and contained fluids crosscourse epithermal mineralisation occurred as in was transported by cacl2 rich basinal brines in a similar manner as in bearing veins in the west shropshire ore field

fluid inclusion studies in opaque ore minerals ii a comparative study of syngenetic synthetic fluid inclusions hosted in quartz and opaque minerals fluid inclusion studies give unique insights into physical conditions and composition of fluids involved in geological processes most studies to date are performed on transparent minerals near infrared nir microscopy allows also microthermometry to be performed on minerals that are opaque to the visible light such as pyrite hematite wolframite enargite and stibnite the main drawback of this technique is the underestimation of the recorded phase change temperatures with increasing light intensity up to several hundred percent in the case of ice melting temperatures although this issue has been known for a decade it is poorly understood we address this problem based on a systematic study of synthetic fluid inclusions in a variety of opaque minerals for the first time fluid inclusions have been co synthetized with success in quartz and opaque minerals fracturing the host minerals by in situ quenching allowed for fluid mineral equilibration prior to fluid inclusion formation in this study we assess the impact of mineral intrinsic parameters mainly absorption and thermal conductivity and experimental settings light source operative power diaphragms aperture and the use of filters on recorded phase change temperatures we show that these are underestimated due to local overheating of the sample caused by radiative heating from the light source it affects all minerals and the extent of the temperature shift of the observed phase changes depends on sample thickness mineral characteristics and the amount of light reaching the sample thus any calibration of the temperature shift as a function of the amount of light is complicated and in most cases impracticable however we demonstrate based on co generated inclusions in opaque minerals and quartz that yield similar values during nir microthermometry that for any mineral there is a range of light power and microscope settings for which no shift is noticeable within the thermal stage accuracy these are defined as ideal measuring conditions ensuring reliability of acquired microthermometry data

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

tide induced salt fingering flow during submarine groundwater discharge this study investigated the stability of the upper saline plume usp within shallow tide affected submarine groundwater discharge sgd zones in contrast to earlier studies numerical modeling revealed a number of realistic hydrological and hydrogeological conditions where the usp becomes unstable and salt fingering flow occurs these conditions were reasonably well identified in a stability diagram based on two dimensionless numbers that characterize the system if fingering flow occurs the sgd pattern is distinctly different from that of stable flow conditions i freshwater discharge zones along the beach face are manifold and change their location with time ii undulating freshwater seawater interface that is extended along the groundwater flow path and iii the total tide averaged fresh sgd rate varies considerably in an irregular pattern this has presumably important implications on reactive transport processes in the subterranean estuary as well as on the interpretation of field data on water and solute fluxes during sgd

ultrahigh pressure metamorphism in the forbidden zone the xugou garnet peridotite sulu terrane eastern china the xugou garnet peridotite body of the southern sulu ultrahigh pressure uhp terrane is enclosed in felsic gneiss bounded by faults and consists of harzburgite and lenses of garnet clinopyroxenite and eclogite the peridotite is composed of variable amounts of olivine fo91 enstatite en92 93 garnet alm20 23prp53 58knr6 9grs12 18 diopside and rare chromite the ultramafic protolith has a depleted residual mantle composition indicated by a high mg number very low cao al2o3 and total ree contents compared to primary mantle and other sulu peridotites most garnet prp44 58 clinopyroxenites are foliated except for rare kyanite bearing eclogitic bands most eclogites contain a simple assemblage of garnet alm29 34prp32 50grs15 39 omphacite jd24 36 minor rutile clinopyroxenite and eclogite exhibit lree depleted and lree enriched patterns respectively but both have flat hree patterns normalized la sm and yb contents indicate that both eclogite and garnet clinopyroxenite formed by high pressure crystal accumulation variable trapped melt from melts resulting from two stage partial melting of a mantle source recrystallized textures and p t estimates of 780 870 c 5 7 gpa and a metamorphic age of 231 11 ma indicate that both mafic and ultramafic protoliths experienced triassic uhp metamorphism in the p t forbidden zone with an extremely low thermal gradient 5 c km 1 and multistage retrograde recrystallization during exhumation develop of prehnite veins in clinopyroxenite eclogite felsic blocks and country rock gneiss and replacements of eclogitic minerals by prehnite albite white mica and k feldspar indicate low temperature metasomatism

discovery of metamorphic diamonds in central china an indication of a 4000 km long zone of deep subduction resulting from multiple continental collisions the central orogenic belt cob of china is a major continental collision zone that contains extensive outcrops of deeply subducted and exhumed rocks at both the eastern and the western end of the belt here we report discovery of microdiamonds from both eclogites and felsic gneisses in the north qinling zone in the central portion of the cob this discovery demonstrates that the country rocks of continental affinity shared in the ultra high pressure metamorphic uhpm event and provides a bridge connecting the two previously recognized uhpm terranes thereby establishing the existence of a uhpm belt extending more than 4000 km geochronological dating yields early palaeozoic ages in the west and early mesozoic ages in the east recording two separate continental collisions overprinted within the cob occurrence of uhp metamorphism during recurrent continental collision here and in the alps suggests that deep subduction of continental material during such collisions is probably common rather than exceptional with significant implications for processes of plate tectonic reorganization and mantle mixing over time

molybdenite re os and albite 40ar 39ar dating of cu au mo and magnetite porphyry systems in the yangtze river valley and metallogenic implications abstract the area of the middle lower yangtze river valley eastern china extending from wuhan hubei province to western zhenjiang jiangsu province hosts an important belt of cu au mo and fe deposits there are two styles of mineralization i e skarn porphyry stratabound cu au mo fe deposits and magnetite porphyry deposits in several nne trending cretaceous fault bound volcanic basins the origin of both deposit systems is much debated we dated 11 molybdenite samples from five skarn porphyry cu au mo deposits and 5 molybdenite samples from the datuanshan stratabound cu au mo deposit by icp ms re os isotope analysis nine samples from the same set were additionally analyzed by ntims on re os results from the two methods are almost identical the re os model ages of 16 molybdenite samples range from 134 7 2 3 to 143 7 1 6 ma 2 the model ages of the five samples from the datuanshan stratabound deposit vary from 138 0 3 2 to 140 8 2 0 ma with a mean of 139 3 2 6 ma their isochron age is 139 1 2 7 ma with an initial os ratio of 0 7 8 1 mswd 0 29 these data indicate that the porphyry skarn systems and the stratabound deposits have the same age and suggest an origin within the same metallogenic system albite 40 ar 39 ar dating of the magnetite porphyry deposits indicates that they formed at 123 to 125 ma i e 10 20 ma later both mineralization styles characterize transitional geodynamic regimes i e the period around 140 ma when the main ns trending compressional regime changed to an ew trending lithospheric extensional regime and the period of 125 115 ma of dramatic ew trending lithospheric extension

genesis of the wurinitu w mo deposit inner mongolia northeast china constraints from geology fluid inclusions and isotope systematics abstract the wurinitu w mo deposit is located in the erlian east ujimqin metallogenic belt in the great xing an range ne china tungsten and molybdenum mineralization generally occurs as veins in quartz hosted by the middle to lower ordovician wall rocks or as disseminations in the early cretaceous monzogranite intrusions fluid inclusion studies and multiple isotope analyses provide systematic evidence to determine the evolution of the hydrothermal fluids the source of metals and fluids as well as mineral precipitation mechanisms which are significant for the magmatic hydrothermal system but are poorly understood three types of fluid inclusion assemblages fias including l liquid rich two phase fias v vapor rich two phase fias and l v liquid vapor two phase fias have been identified in quartz veins from the w mineralization i mo mineralization ii and quartz carbonate iii stages at wurinitu the ore forming fluids evolved from a high to moderate temperature and moderate to low salinity h2o nacl co2 system in the w and mo mineralization stages to a low temperature and low salinity h2o nacl system in the quartz carbonate stage they were trapped at temperatures of 365 c 266 c and 198 c the results of hydrogen and oxygen isotope analyses 18oh2o 4 0 to 7 7 dh2o 116 to 92 indicate that the stage i fluids dominantly originated from magmatic water and the stages ii and iii show addition of meteoric water sulfur 34svcdt 1 9 4 0 and lead isotope values 206pb 204pb 18 099 18 728 207pb 204pb 15 527 15 616 and 208pb 204pb 38 019 38 465 suggest that the ore metals in the hydrothermal fluids were derived from the granitic magma all these observations reveal that 1 the wurinitu w mo deposit is a magmatic hydrothermal ore system 2 w and mo mineralization occurred under lithostatic pressure of 203 294 bars and hydrostatic pressure of 102 bars respectively and 3 fluid boiling and mixing with meteoric water might be the key factors controlling the large scale ore deposition at wurinitu

shrimp u pb dating trace elements and the lu hf isotope system of coesite bearing zircon from amphibolite in the sw sulu uhp terrane eastern china abstract in this study we link mineral inclusion data trace element analyses u pb age and hf isotope composition obtained from distinct zircon domains of complex zircon to unravel the origin and multi stage metamorphic evolution of amphibolites from the sulu ultrahigh pressure uhp terrane eastern china zircon grains separated from amphibolites from the ccsd mh drill hole g12 and niushan outcrop g13 were subdivided into two main types based on cathodoluminescence cl and laser raman spectroscopy big dusty zircons with inherited cores and uhp metamorphic rims and small clear zircons weakly zoned grey white luminescent inherited cores preserve mineral inclusions of cpx pl ap qtz indicative of a mafic igneous protolith dark grey luminescent overgrowth rims contain the coesite eclogite facies mineral inclusion assemblage coe grt omp phe ap and formed at t 732 839 c and p 3 0 4 0 gpa in contrast white luminescent small clear zircons preserve mineral inclusions formed during retrograde hp quartz eclogite to lp amphibolite facies metamorphism t 612 698 c and p 0 70 1 05 gpa inherited zircons from both samples yield shrimp 206 pb 238 u ages of 695 520 ma with an upper intercept age of 800 31 ma the uhp rims yield consistent triassic ages around 236 225 and 239 225 ma for g12 and g13 with weighted means of 229 3 and 231 3 ma respectively small clear zircons from both samples give 206 pb 238 u ages around 219 210 ma with a weighted mean of 214 3 ma interpreted as the age of retrograde quartz eclogite facies metamorphism matrix amphibole from both samples indicate ar ar ages of 209 0 7 and 207 0 7 ma respectively probably dating late amphibolite facies retrogression the data suggest subduction of neoproterozoic mafic igneous rocks to uhp conditions in middle triassic 230 ma times and subsequent exhumation to an early hp 214 ma and a late lp stage 208 ma over a period of 16 and 6 myr respectively thus early exhumation from a mantle depth of 120 100 km to about 60 km occurred at an average rate of 0 3 cm y while subsequent exhumation to a middle crustal level took place at approximately 0 54 cm y these exhumation rates are considerably slower than those obtained for uhp rocks in the dora maira and kokchetav massifs 2 3 cm y based on similar p t estimates and trace element and hf isotope compositions sulu amphibolites can be identified as retrograde uhp eclogites the ehf 800 of 8 implies a significant input from the depleted mantle to the sulu dabie terrane during the middle neoproterozoic overgrown rims are characterized by a distinct trace element composition with low lu hf and th u and significantly higher 176 hf 177 hf ratios than inherited cores consistent with formation during after garnet re crystallization and fractionation of the lu hf system during uhp metamorphism the combined dataset suggests homogenization of the 176 hf 177 hf ratio within the metamorphic mineral assemblage and during protolith formation observed variations are explained by mixing of material from both domains during laser ablation e g due to partial recrystallization of inherited cores

an infrared microthermometric study of fluid inclusions in coexisting quartz and wolframite from late mesozoic tungsten deposits in the gannan metallogenic belt south china abstract numerous wolframite quartz vein type tungsten deposits are present in the gannan metallogenic belt south china including the piaotang and dangping deposits in the chong you yu ore cluster the dajishan deposit in the jiulianshan ore cluster and the pangushan deposit in the yushan ore cluster the ores generally consist of quartz and wolframite with variable amounts of base metal sulfides wolframite and quartz are intergrown but the genetic relationships between them are still ambiguous quartz contains two phase aqueous inclusions type i and two or three phase co 2 bearing inclusions type ii but wolframite only contains two phase aqueous inclusions type iw the homogenization temperatures for primary inclusions in wolframite are generally 40 to 100 c higher than those in quartz in a single deposit moreover there are variable amounts of co 2 in inclusions in quartz but no co 2 rich inclusions are identified in coexisting wolframite type i fluid inclusions in quartz from the piaotang deposit show that fluid mixing is predominant in the formation of quartz veins whereas fluid inclusions from the dangping deposit suggest that simple cooling is the primary factor quartz from the dajishan and pangushan deposits contains both type i and coexisting type ii inclusions indicating a process of fluid immiscibility the homogenization temperatures of two phase aqueous inclusions type iw in wolframite from all of these deposits show a clearly decreasing trend with constant salinities implying a simple cooling process hence simple cooling fluid mixing and fluid immiscibility take place in quartz but only simple cooling happens in wolframite our results show that the gangue and ore minerals from the late mesozoic tungsten deposits in the gannan metallogenic belt have different homogenization temperatures volatile compositions and fluid processes the gangue minerals do not provide reasonable estimates of the depositional conditions of the ore minerals even though they are intimately intergrown

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

tidal effects on sea water intrusion in unconfined aquifers abstract a variable density groundwater model is used to analyse the effects of tidal fluctuations on sea water intrusion in an unconfined aquifer it is shown that the tidal activity forces the sea water to intrude further inland and it also creates a thicker interface than would occur without tidal effects moreover the configuration of the interface is radically changed when the tidal fluctuations are included this is because of the dramatic changes in the flow pattern and velocity of the groundwater near the shoreline for aquifer depths much larger than tidal amplitudes the tidal fluctuation does not have much effect on how far the sea water intrudes into the aquifer nevertheless a significant change in the configuration of concentration contours because of the effect of tidal fluctuations is observed this change is more noticeable at the top of the aquifer near the water table than at the bottom of the aquifer and is caused by the infiltration of salt water into the top of the aquifer at higher tidal levels a flatter beach slope therefore intensifies this phenomenon the interface configurations do not change noticeably over the course of a tidal cycle neglecting tidal fluctuation effects results in an inaccurate evaluation of the water table elevation at the land end of the aquifer although no distinguishable difference is seen between the water tables near the shoreline where the landward boundary condition is a constant head the effects of tidal fluctuations on sea water intrusion are more pronounced than for cases where the landward boundary condition is a specified flux also it is shown that the effects of tidal fluctuations are more significant for a sloping beach than for a vertical shoreline and the salt water intrudes further inland for the sloping case

instabilities of submarine groundwater discharge under tidal forcing we conducted laboratory experiments and numerical modeling to investigate the instability of the freshwater seawater interface and associated submarine groundwater discharge locations under tidal forcing contrary to today s common view of the hydraulic conditions in the intertidal region i e the formation of a stable upper saline plume concurrent with the existence of a so called freshwater discharge tube below which pinches out at the beach surface close to the low tide mark is actually extremely unstable under certain conditions we found that for a gentle beach slope of 1 12 a transient upper freshwater seawater interface develops between the high and low water line characterized by several migrating saltwater fingers that intrude into the aquifer groundwater discharge occurs between these saltwater fingers at various locations in the intertidal region and is not limited to the low tide mark numerous scenarios are possible between the stable and the unstable cases depending on the ambient groundwater flux tidal amplitude beach slope permeability of the sediment heterogeneity and anisotropy

polyphase growth of accessory minerals during continental collision geochemical evidence from ultrahigh pressure metamorphic gneisses in the sulu orogen abstract an integrated study of petrology geochronology and geochemistry was performed for ultrahigh pressure metamorphic gneisses in the sulu orogen the results are used to elucidate the polyphase growth of such metamorphic minerals as zircon titanite and garnet in response to pressure temperature changes and fluid melt action during continental collision this provides insights into the property of metamorphic fluid melt and their effects on trace element mobility a combined result from ree patterns mineral inclusions and ti in zircon temperatures indicates three stages of zircon growth prograde growth occurred at 237 ma primarily at eclogite facies retrograde growth at 222 ma mostly at eclogite facies and the last growth at 205 ma at granulite facies the three stages of zircon growth are deciphered by distinct ree patterns and trace element compositions reflecting the differences in the property of metamorphic fluid melt the episodic growth of metamorphic zircon is primarily dictated by the episodic concentration of zr and si in metamorphic fluid melt relict domains of magmatic titanite are distinguished from metamorphosed and metamorphic domains by their distinctive ree patterns and trace element compositions the metamorphic titanite exhibit variably elevated nb contents and nb ta ratios suggesting nb ta fractionation due to breakdown of amphibole and or biotite during metamorphism polyphase growth of garnet is suggested by an integrated analysis of mineral inclusions and major and trace elements in large garnet grains trace element abundances vary in different zones of garnet which is ascribed to changes in the paragenesis and composition of matrix minerals involved in garnet forming reactions at different p t conditions therefore the metamorphic growth of zircon titanite and garnet would have occurred not only during prograde subduction but also during retrograde exhumation in the continental collision zones both metamorphic dehydration and partial melting would have taken place episodically during the collisional orogeny the breakdown of hydrous minerals at high to ultrahigh pressure conditions is a key to fluid liberation and element supply for the growth of these accessory minerals

distinctive features of late palaeozoic massive sulphide deposits in south china abstract more than 20 sediment hosted massive sulphide deposits occur in late palaeozoic basins in south china these deposits are accompanied by a certain amount of volcanic rocks in the host sequence and are economically important for their cu pb zn au and ag reserves the deposits and their host strata were commonly intruded by mesozoic granitoids remobilisation of sedimentary ores and magmatic hydrothermal overprinting processes resulted in the coexistence of massive sulphides with vein skarn and porphyry type orebodies in the same region or within a single deposit the ore containing basins occur in different tectonic settings the lower yangtze basin occurs on a passive continental margin where the deposits are high in cu and au with minor pb and zn and recoverable ag co and mo the ores have a lower concentration of radiogenic lead and 34s values close to zero fluid inclusions are highly saline and na rich fluids and metals of the lower yangtze region are interpreted to have been derived essentially from deep sources including the precambrian basement by contrast basins of the nanling region formed in an intracontinental setting developed on a folded caledonian basement these deposits are higher in pb zn sn and w as well as cu with recoverable ag sb hg u bi tl and mo the ores are characterised by a higher concentration of radiogenic lead and a wide variation of 34s composition fluid inclusions have lower salinities and higher k na ratios fluids are considered to have been sourced substantially from seawater by convection metals for the nanling deposits were essentially derived from the caledonian basement by leaching the contrast in ore composition between these two regions appears to have been controlled by differences in basement composition of the ore forming basins

contribution of infrared microscopy to studies of fluid inclusions hosted in some opaque ore minerals possibilities limitations and perspectives during the past two decades several studies of fluid inclusions hosted in some opaque ore minerals using near infrared microscopy have been performed results indicated that this method can be applied to several sulfidic ores and metal oxides depending on their electronic band structures and infrared active vibration modes infrared transmittance of individual ore minerals can be best characterized using fourier transform infrared spectroscopy infrared microscopic observations are limited to the near infrared region to about 2 3 m depending on the ir sensitivity of the ir camera the trace element content in ore minerals can be another limiting factor for optical observations in near infrared light still ir transmittance gradually decreases upon heating caused by shifting of ir absorption edges for higher wavelengths possibilities and limitations of studying fluid inclusions hosted in opaque minerals by near infrared light microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms are discussed

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

constraining ultrahigh pressure uhp metamorphism and titanium ore formation from an infrared microthermometric study of fluid inclusions in rutile from donghai uhp eclogites eastern china eclogites in the donghai area of the sulu ultrahigh pressure uhp metamorphic belt in eastern china contain both disseminated rutile and rutile deposits the rutile occurs as small inclusions in garnet omphacite phengite and quartz as larger euhedral to subhedral grains in equilibrium with garnet omphacite phengite and kyanite and as discrete veinlets aggregates and megacrysts in cracks and along grain boundaries to investigate the processes of rutile mineralization and its relationship to the evolution of the sulu uhp metamorphic belt we sampled the exposed maobei deposit at donghai and drill core between 100 and 2000 m in the nearby chinese continental scientific drilling project ccsd main hole to carry out a detailed infrared microthermometric fluid inclusion study three types of fluid inclusions were identified aqueous type i co 2 h 2 o type ii and ch 4 type iii type i and type ii inclusions are the most common primary and pseudosecondary type i inclusions which were trapped during recrystallization of the eclogite or early amphibolite facies retrograde metamorphism have a narrow range of homogenization temperatures but a wide range of salinities in contrast secondary type i inclusions which formed entirely during retrograde amphibolite facies metamorphism associated with exhumation of the uhp rocks have higher and more varied homogenization temperatures but medium to low salinities type ii inclusions formed contemporaneously with the type i variety and are characterized by having small amounts of co 2 and n 2 in addition to h 2 o in addition some of the rutile grains contain sparse inclusions composed of ch 4 type iii our results combined with those of previous studies suggest a great diversity of fluid composition in the peak metamorphic to early retrograde stages implying very limited fluid rock interaction during syn to post peak high pressure hp and uhp metamorphism this study shows that infrared microthermometric investigation of fluid inclusions can provide information not only on the composition of titanium ore forming fluids but also on the relationship between mineralization and the evolution of uhp metamorphic belt

significance of zr in rutile thermometry for deducing the decompression p t path of a garnet clinopyroxene granulite in the moldanubian zone of the bohemian massif

combined investigations of fluid inclusions in opaque ore minerals by nir swir microscopy and microthermometry and synchrotron radiation x ray fluorescence abstract an alternative ir microscopy system in the nir near infrared up to 10 m and swir short wavelength infrared up to 1 4 m ranges has been developed for the study of opaque ore minerals the system uses either ir led or ir light bulb sources depending on the degree of opacity of the investigated minerals this paper presents the methodology and the promising results obtained in studies of opaque ore minerals such as ag minerals pyrargyrite from epithermal deposits and nb tantalates columbite from pegmatites it also presents results on the internal features of hematites from fe ore banded formations and tungstates from granite greenstone belt deposits the data obtained on fluid inclusions from pyrargyrite and hematite crystals have been integrated by complementary information from x ray fluorescence analysis using synchrotron radiation sxrf under conditions specifically designed for the study of opaque ore minerals

fluid inclusion and isotopic c h o s and pb constraints on the origin of late mesozoic vein type w mineralization in northern guangdong south china abstract northern guangdong of south china occurs many large tungsten deposits including shirenzhang meiziwo and yaoling quartz vein type wolframite deposits in this study we carried out a detailed study on fluid inclusions and c h o s pb isotopic analyses of mineral separates for these three deposits in order to resolve the origin and evolution of ore forming fluids and the ore deposition mechanism the ore veins in these deposits present a similar mineral paragenesis that could be divided into three stages i pre ore stage ii syn ore stage and iii post ore stage the pre ore stage is the magmatic hydrothermal transition stage which is marked by fluid exsolution from the highly fractionated granites accompanied with potassic alteration and greisenization the syn ore stage can be further divided into two stages silicate oxide stage stage ii 1 that is characterized by significant tin tungsten mineral deposition and sulfide stage stage ii 2 that is characterized by abundant sulfide minerals deposition the post ore stage is dominated by quartz and fluorite the three deposits show similar temperature and salinity variations for syn ore and post ore stages in the shirenzhang deposit the fluid temperature and salinity range from 239 to 301 c and 1 4 to 8 7 wt nacl equiv in stage ii 1 from 206 to 256 c and 1 4 to 7 0 wt nacl equiv in stage ii 2 and from 186 to 236 c and 1 4 to 8 6 wt nacl equiv in stage iii in the meiziwo deposit the fluid temperature and salinity range from 242 to 310 c and 1 1 to 8 6 wt nacl equiv in stage ii 1 from 196 to 252 c and 1 4 to 8 1 wt nacl equiv in stage ii 2 and from 188 to 234 c and 1 2 to 7 3 wt nacl equiv in stage iii in the yaoling deposit the fluid temperature and salinity range from 230 to 304 c and 1 2 to 9 0 wt nacl equiv in stage ii 1 from 203 to 258 c and 1 4 to 6 5 wt nacl equiv in stage ii 2 and from 184 to 231 c and 1 6 to 8 3 wt nacl equiv in stage iii the ore forming fluids in the three deposits belong to a medium temperature low salinity h2o nacl system with trace amounts of volatile components including co2 ch4 and n2 the c h o isotope data 13cco2 18 9 to 6 7 18owater 1 1 to 6 3 dh2o 78 to 55 indicate that the ore forming fluids were mainly magmatic water which might be modified by fluid rock interaction and mixing with meteoric water sulfur 34s 7 0 to 0 3 and pb isotope data 206pb 204pb 18 531 18 693 207pb 204pb 15 728 15 753 208pb 204pb 38 902 39 081 suggest that the ore metal and sulfur are of magmatic origin the involvement of both organic matter in metasedimentary rocks during fluid rock interaction and oxidized meteoric water may have been responsible for the negative 34s and 13c values fluid boiling fluid rock interaction and minor input of meteoric water might have been effective factors for the precipitation of wolframite cassiterite and scheelite the sulfide precipitation may have resulted from cooling and dilution of magmatic fluids by mixing with meteoric water

syn collisional transform faulting of the tan lu fault zone east china origin of the continental scale tan lu fault zone tlfz east china remains controversial about 550 km sinistral offset of the dabie orogenic belt dob and sulu orogenic belt sob is shown along the ne nne striking tlfz syn collisional sinistral ductile shear belts in the tlfz have been identified thirteen phengite bulk separates from the mylonites were dated by the 40ar 39ar method they gave cooling ages of the 198 181 ma for the shear belts along the eastern margin of the dob and 221 210 ma from the western margin of the sob distribution of the foreland basin deposits suggests that sinistral offset of the dob and sob by the tlfz took place prior to deposition of the upper triassic strata the marginal structures around the dob and sob support syn collisional faulting and indicate anticlockwise rotation of the dob during the displacement the folding and thrust faulting related to crustal subduction coeval with the tan lu faulting is older than the foreland basin deposition related to the orogenic exhumation several lines of evidence demonstrate that the tlfz was developed as a syn collisional transform fault during latest middle to earliest late triassic time when the dob and sob experienced crustal subduction of the south china block scb eastward increase of the crustal subduction rates is believed to be responsible for the sinistral transform faulting

geology geochemistry and age of the hukeng tungsten deposit southern china abstract the hukeng tungsten deposit located in the wugongshan area in central part of jiangxi province south china is a large scale quartz vein wolframite deposit it is hosted in the hukeng granitic intrusion based on the mineral assemblage and crosscutting relationship of the veins three mineralization stages are identified including 1 quartz wolframite stage 2 quartz fluorite wolframite stage and 3 quartz pyrite sphalerite wolframite stage the homogenization temperatures of fluid inclusions in vein quartz vary from 220 to 320 c and the salinities are from 0 to 10 wt nacl equiv corresponding densities range from 0 7 to 1 g cm 3 these features indicated that the ore forming fluids in the hukeng tungsten deposit have medium temperature low density and low salinity the 18 osmow values of quartz range from 10 8 to 14 4 with corresponding 18 o fluid values of 3 7 to 7 7 and d values of fluid inclusions of between 70 and 55 the combined isotopic data indicate that the ore forming fluids of the hukeng tungsten deposit were mainly derived from magmatic water with some minor input from meteoric water we have carried out molybdenite re os and muscovite 40 ar 39 ar dating to constrain the timing of mineralization re os dating of six molybdenite samples yielded model ages ranging from 149 1 2 0 to 150 7 3 7 ma with an average of 150 0 ma the re os analyses give a well defined 187 re 187 os isochron with an age of 150 2 2 2 ma mswd 0 60 hydrothermal muscovite yields a plateau 40 ar 39 ar age of 147 2 1 4 ma 40 ar 39 ar age is in good agreement with the re os age these ages show that the timing of tungsten mineralization occurred at about 150 ma our new data when combined with published geochronological results from the other major deposits in this region suggest that widespread w mineralization occurred in the late jurassic throughout south china

shrimp u pb zircon ar ar muscovite and re os molybdenite isotopic dating of the taoxikeng tungsten deposit south china block abstract the taoxikeng tungsten deposit is located in the jiangxi province in the southern part of china and is one of the largest wolframite quartz vein type tungsten deposits in the country the deposit is situated in sinian neoproterozoic to permian strata at the contact with the buried taoxikeng granite sensitive high mass resolution ion microprobe shrimp zircon u pb analysis of the granite has yielded dates of 158 7 3 9 and 157 6 3 5 ma which are interpreted as the emplacement age of the granite molybdenite separated from ore bearing quartz veins yields a re os isochron age of 154 4 3 8 ma and muscovite separated from greisen between the granite and country rocks yields 40ar 39ar plateau ages of 153 4 1 3 and 152 7 1 5 ma these dates obtained from three independent geochronological techniques constrain the ore forming age of the taoxikeng deposit and link the ore genesis to that of the underlying granite the taoxikeng deposit is an example of a jurassic regional scale tungsten tin ore forming event between 160 and 150 ma in the nanling region of the south china block the deposit s strikingly low rhenium contents 4 9 to 13 0 10 3 g g in molybdenite suggests that the ore was derived from a crustal source this conclusion is consistent with previously published constraints from s d and o stable isotopes sr nd systematics and petrogenetic interpretations of spatially related granites

orogeny and relative plate motions example of the japanese islands abstract the paleogeography of the eastern margin of asia near japan for the past 250 ma has been reconstructed on the basis of the relative motions between the oceanic plates and the eurasian plate engebretson et al 1982 and on land geology the relationships between the plate kinematics and orogeny are as follows calc alkaline magmatism is related to the presence of subduction when a plate boundary is a transform fault there is no volcanism very slow convergence rates do not give rise to magmatism migration of rft type triple junctions or ridge subduction produces forearc volcanism near the trench and also a wider volcanic zone uplift of low p t type regional metamorphic belts is related to collision episodes the uplift of the high p t blueschist belts on the contrary is not contemporaneous with them they appear to be related to the start of the subduction of a young plate after the migration of an rft type triple junction because the formation of a voluminous accretionary complex is contemporaneous with this and thrusting of this young accretionary complex beneath the uplifted metamorphic belt is often observed the underplating of the young accretionary complex beneath the older accretionary complex would be the cause of the uplift of the high p t type metamorphic belt the subduction of a young plate would thus be an important factor causing these orogenic events highly oblique convergence also results in formation of a serpentinite melange zone with fragments of blueschists presumably along a mechanical plate boundary in the forearc

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

u pb geochronology of tin deposits associated with the cornubian batholith of southwest england direct dating of cassiterite by in situ la icpms the cornwall and devon vein and greisen type copper and tin deposits of southwest england are spatially and genetically related to shallow seated granitic intrusions these late variscan intrusions collectively known as the cornubian batholith extend over 200 km and form a continuous granitic spine from the isles of scilly granite in the west to the dartmoor granite in the east the granitic plutons of the cornubian batholith were intruded from 295 to 270 ma without a major hiatus twelve samples of cassiterite sno2 were obtained from tin deposits associated with seven different plutons within the cornubian batholith for in situ la icpms u pb dating this study of cassiterite was undertaken to obtain the first results of direct dating of ore mineral to refine the geochronology of tin mineralization in this region of the cassiterite samples analyzed the oldest ages were determined within the kit hill and hingston gunnislake granites in the central part of the cornubian batholith the hingston gunnislake cassiterite from drakewalls mine was the oldest sample dated at 291 8 3 4 ma the next oldest dates 290 5 2 8 and 288 5 2 9 ma were from two cassiterite samples extracted from the adjacent kit hill consolidated mines within the kit hill granite at the eastern end of the study area two cassiterite samples within the dartmoor granite produced ages of 286 0 1 8 and 284 1 1 3 ma the youngest sample from this study 275 4 1 6 ma is from the balleswidden mine within the westernmost land s end granite the cassiterite dates do not reveal any readily observable relationship between ore ages and geographic relationship from west to east throughout the cornubian batholith incorporating the associated errors the geochronology does indicate continuous mineralization within the granites for 21 million years from ca 295 to 274 ma this span falls within the established period of granitic magmatism of ca 295 to 270 ma for the cornubian batholith and further confirms the reliability of in situ la icpms u pb dating of cassiterite

polygenetic titanite records the composition of metamorphic fluids during the exhumation of ultrahigh pressure metagranite in the sulu orogen

metamorphic p t conditions and thermal structure of chinese continental scientific drilling main hole eclogites fe mg partitioning thermometer vs zr in rutile thermometer core rocks recovered from the main hole 5158 m deep of the chinese continental scientific drilling ccsd mh project southern sulu uhp terrane east central china consist of eclogites various gneisses and minor metaperidotite cumulates this lithological section underwent subduction zone uhp metamorphism coesite bearing eclogites are mainly present between the depths of 100 2000 m but below 2000 m mafic eclogites are rare selected elements zr nb cr fe si mg al ti in rutile from 39 eclogite cores from 100 to 2774 m and major elements of minerals from representative eclogites were analysed by electron microprobe zirconium and nb concentrations of rutile cluster 100 400 and 200 700 ppm respectively however zr and nb contents in rutile from strongly retrograded eclogites show larger variations than those of fresh or less retrograded eclogites implying that somehow fluid infiltration affected rutile chemistry during retrograde metamorphism zr contents in rutile inclusions in garnet and omphacite are slightly lower than those of the matrix rutile suggesting that the rutile inclusions formed before or close to the peak temperature the p t conditions of the ccsd mh eclogites were estimated by both fe mg exchange and zr in rutile thermometers as well as by the grt cpx phn ky geothermobarometer the maximum temperature range of 700 811 c calculated at 40 kbar using the zr in rutile thermometer is comparable with temperature estimates by the fe mg exchange thermometer the temperature estimates of eclogites in a 3000 m thick section define a continuous gradient and do not show a distinct temperature gap suggesting that the rocks from 100 to 3000 m depth might belong to a single large scale uhp slab these data combined with p t calculations for ccsd mh peridotites yield a low geotherm 5 ck m 1 for the triassic subduction zone between the sino korean and yangtze cratons it lies 30 35 mw m 2 conductive model geotherm

contrasting fluid behavior during two styles of greisen alteration leading to distinct wolframite mineralizations the echassieres district massif central france abstract the echassieres district of central france hosts diverse magmatic and magmatic hydrothermal deposits of rare metals mostly related to the well known beauvoir granite tungsten mineralization crops out at three distinct wolframite occurrences the two most important of which are related to two distinct magmatic bodies emplaced ca 335 and 310 ma monnier et al 2019 the mineralization occurred at 335 ma formed during a hydrothermal episode marked by precipitation of topaz replacing quartz in a stockwork system and as veinlets in the surrounding schist fluid inclusions in topaz and quartz display similar features i e all have low salinity contain significant amount of licl display constant liquid vapor ratios and homogenized within a narrow temperature range th 380 c no evidence for fluid pressure variations was observed and temperature decrease is considered to be the main cause for wolframite deposition the younger w mineralization is related to greisenizing fluids that altered the beauvoir granite and generated several quartz topaz and apatite veins all greisen related fluid inclusions display low salinity however th are spread from ca 190 to 400 c and several populations exhibit heterogeneous liquid vapor ratios while others consist of only vapor rich fluid inclusions respectively these populations are interpreted to have been trapped during boiling or flashing vaporization of the fluid in contrast with the other regional veins flashing was particularly intense in the mazet veins which host the bulk of the last wolframite generation consequently it is proposed that flashing is the key factor that triggered w precipitation this work highlights the role of two physical parameters pressure and temperature whose variations played a preponderant role on wolframite mineralization it documents in depth an example of greisen fluid evolution providing critical information on w behavior in orthomagmatic fluids and on greisen related rare metal deposits

infrared microthermometry of fluid inclusions in transparent to opaque minerals challenges and new insights infrared ir studies of fluid inclusions in opaque minerals provide direct insights into the ore forming fluids however the challenge posed by the warming effect of ir light during microthermometry remains unresolved here we address this problem and show that the deviation in temperature of phase changes within fluid inclusions caused by ir light is more common than what was thought before our results reveal that transparent to translucent minerals e g quartz sphalerite also absorb ir energy since ir absorption is influenced by the host mineral the fluid inclusions hosted by different minerals exhibit different degrees of deviation in temperature during microthermometry the fourier transform infrared ftir spectra do not display a consistent correlation between the band gap energy of a mineral and its absorption of ir energy minerals with low band gap energy such as pyrite absorb limited ir energy resulting in small deviations of fluid inclusion data in contrast this deviation could be significant for fluid inclusions hosted in minerals with a relatively high band gap energy such as iron rich sphalerite and wolframite substitution of iron increases the absorption of ir energy in these minerals the substitution of trace elements may also play a role our quantitative analyses confirm that using the lowest possible ir light intensity with the smallest diaphragm minimizes the warming effect of ir light we also propose an improved cycling method as a better option where high ir light intensity is required

fluid origin and structural enhancement during mineralization of the jinshan orogenic gold deposit south china the jinshan orogenic gold deposit is a world class deposit hosted by a ductile shear zone caused by a transpressional terrane collision during neoproterozoic time ore bodies at the deposit include laminated quartz veins and disseminated pyrite bearing mylonite most quartz veins in the shear zone with and without gold mineralization were boudinaged during progressive shear deformation with three generations of boudinage structures produced at different stages of progressive deformation observations of ore controlling structures at various scales indicate syn deformational mineralization fluid inclusions from pyrite intergrown with auriferous quartz have 3he 4he ratios of 0 15 0 24 ra and 40ar 36ar ratios 575 3 060 18ofluid values calculated from quartz are 5 5 8 4 and d values of fluid inclusions contained in quartz range between 61 and 75 the 13c values of ankerite range from 5 0 to 4 2 and ankerite 18o values from 4 4 to 8 0 the noble gas and stable isotope data suggest a predominant crustal source of ore fluids with less than 5 mantle component data also show that in situ fluids were generated locally by pervasive pressure solution and that widespread dissolution seams acted as pathways of fluid flow migration and precipitation the in situ fluids and fluids derived from deeper levels of the crust were focused by deformation and deformation structures at various scales through solution dissolution creep crack seal slip and cyclic fault valve mechanisms during progressively localized deformation and gold mineralization

synexhumation anatexis of ultrahigh pressure metamorphic rocks petrological evidence from granitic gneiss in the sulu orogen abstract petrological evidence is provided for partial melting of ultrahigh pressure uhp metamorphic granitic gneiss in the sulu orogen petrographic observations show the occurrence of elongated highly cuspate feldspars in grain boundaries interstitial cuspate feldspars in triple junctions felsic veinlets mainly consisting of k feldspar quartz and feldspar crystal faces against quartz these features indicate that the feldspar and quartz would have grown from anatectic melts in the granitic gneiss zircon domains grown from these melts were identified based on cl images mineral inclusions and ree patterns some large zircon grains 100 m contain small relict domains of magmatic origin suggesting nearly complete dissolution of the protolith zircon during the anatexis all newly grown zircon domains are categorized into two groups based on the presence or absence of coesite inclusions one group of domains contain no coesite inclusion and exhibit high u contents but low th u ratios pb ages of 217 2 to 224 2 ma the other group of domains contain coesite inclusions and exhibit low u contents and very low th u ratios pb ages of 221 5 to 226 3 ma the two groups of zircon domains are thus interpreted as growing from the anatectic melts at different pressures because they exhibit marked negative eu anomalies that are absent for metamorphic zircons grown from aqueous fluids the zircon u pb ages of 217 2 to 226 3 ma are close to but slightly younger than known ages for major uhp metamorphism in the sulu orogen therefore the uhp gneiss experienced incipient melting during the initial exhumation subsequent to the peak uhp metamorphism and extensive anatexis later at lower pressures muscovite relicts coexist with cuspate feldspars suggesting that the anatectic melts originate from dehydration melting due to decompression breakdown of phengitic muscovite in the uhp granitic gneiss as the degree of partial melting increases with temperature significant fractions of the anatectic melts would be produced in the regional gneiss provided that the uhp rocks experienced hot exhumation such melts can be gathered together being eventually emplaced as synexhumation granitic intrusions

fluid inclusion study of stibnite using infrared microscopy an example from the brouzils antimony deposit vendee armorican massif france a microthermometric study using infrared microscopy was performed on fluid inclusions hosted in stibnite crystals of the brouzils antimony deposit in order to characterize the fluids responsible for the deposition of the antimony at the end of the variscan metallogenic sequence primary fluid inclusions in stibnite were moderately saline 3 5 4 75 wt nacl equiv with homogenization temperatures varying between 140 and 160 c two generations of later fluids are also contained in the stibnite samples the first generation of secondary fluid inclusions is found exclusively in stibnite and is characterized by low salinities 1 35 2 2 wt nacl equiv homogenization temperatures of approximately 215 c and the presence of one or more solid mineral phases the second generation of fluid inclusions is younger and is found in stibnite along secondary planes as well as in quartz gangue it corresponds to h2o co2 fluid with homogenization temperatures of about 180 c this infrared microscopy study thus shows that the quartz and stibnite of the brouzils veins are not cogenetic and reveals the polyphase character of the vein infill in which three successive episodes of hydrothermal circulation are identified

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

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

fluid inclusions and ore precipitation mechanism in the giant xikuangshan mesothermal antimony deposit south china conventional and infrared microthermometric constraints abstract the giant xikuangshan antimony deposit located in the xiangzhong central hunan basin south china is the largest antimony deposit in the world stibnite is the predominant ore mineral and gangue minerals consist of quartz calcite fluorite and barite the ore mineral assemblages include early stage quartz stibnite fluorite quartz stibnite and barite quartz stibnite and late stage calcite stibnite in spite of numerous research works on the xikuangshan deposit during the past several decades the signatures of the ore forming fluids and the ore precipitation mechanisms are poorly constrained in order to characterize the fluids responsible for antimony mineralization and ascertain the genetic processes in the xikuangshan ore district conventional and infrared microthermometric measurements have been performed in this study on fluid inclusions hosted in transparent minerals quartz fluorite and barite and opaque stibnite respectively four types of fluid inclusions were identified for the early stage mineralization based on their phase assemblages including type i pure liquid inclusions type ii two phase liquid rich aqueous inclusions type iii two phase vapor rich aqueous inclusions and type iv pure vapor inclusions stibnite only contains type i and type ii inclusions while all types of fluid inclusions are common in the gangue minerals the homogenization temperatures and salinities of fluid inclusions in stibnite and associated gangue minerals in this ore district display significant differences fluid inclusions in stibnite exhibit relatively low homogenization temperatures 112 323 c and higher salinities 0 2 15 4 wt nacl equiv than inclusions in coexisting gangue minerals 119 366 c 0 2 4 2 wt nacl equiv usually about 50 c less than the intergrown gangue minerals according to the petrography of fluid inclusions and the relationship between their homogenization temperature and salinity it was concluded that stibnite and gangue minerals in the xikuangshan ore district are not co genetic instead they were deposited from two distinctly different hydrothermal solutions fluid mixing was responsible for stibnite precipitation but the precipitation of gangue minerals resulted from fluid boiling due to an abrupt drop in pressure the xikuangshan deposit is a typical example of mesothermal deposits rather than an epithermal deposit as previously considered

on a test case for density dependent groundwater flow and solute transport models the salt lake problem like any other computer model density dependent mathematical groundwater models must be verified to ascertain that they accurately represent the physics implied by a governing set of equations very few test cases for density dependent groundwater numerical models exist as such there is still a need for new and more robust tests of these modeling codes in this paper a numerical model of an idealized evaporating salt lake is produced using the two dimensional density dependent saturated unsaturated transport sutra model the results of which are compared with an equivalent laboratory hele shaw cell system developed by wooding et al 1997a b evaporation results in dense brine overlying less dense fluid which is hydrodynamically unstable and leads to downward convection of salt fingers or plumes a comparison of experimental and numerical plume growth shows good spatial and temporal agreement the numerically generated plume pattern is sensitive to changes in random noise level applied just below the evaporation surface that serves as a trigger for the growth of instabilities experimental plume patterns were best matched with a noise level corresponding to 1 of the total salinity difference between boundary layer and background fluid concentrations at saturation in a second comparison the stream function based finite difference model described by wooding et al 1997a b which differs significantly in principle from sutra is shown after revision to give good spatial and temporal agreement with experimental results this test for density dependent groundwater models appears to be the most comprehensive and detailed available to date

impact of additional dead carbon on the circulation estimation of thermal springs exposed from deep seated faults in the dongguan basin southern china abstract in hydrothermal systems the dissolved carbon of thermal groundwater may contain components derived from mineral alterations under high temperatures metamorphic source and or from magmatic gases additionally from carbonate dissolution most common these components are known as additional dead carbon which dilutes the modern carbon used for dating leading to the overestimation of 14c ages four typical geothermal springs hosted by deep seated faults and eighteen non thermal springs and wells from the dongguan basin of southern china were investigated to assess the circulation times of the hydrothermal system based on their radiocarbon contents for the thermal springs the circulation depth approximately 3648 m the apparent 14c ages 20 15 to 12 97 ka and the 13c calibrated 14c ages 16 02 to 8 55 ka were estimated the circulation speed of the thermal groundwater was as low as 0 46 m a which was too slow for a fracture hydrothermal system hosted by deep faults the analysis of the helium and carbon isotopes in the thermal groundwater revealed the existence of mantle derived carbon and thermally altered carbon from limestones a 13c 3he 4he illustration was proposed to correct for the additional dead carbon content according to the reassessed 14c ages the groundwater circulation time was overestimated and the circulation speed of the thermal groundwater was underestimated in hydrothermal system the reassessed 14c ages can provide a more reasonable result than the initial slow estimate in the context of a fracture hydrothermal system hosted by deep faults we conclude that measured 14c contents should be reassessed during the use of radiocarbon dating for thermal groundwater if additional dead carbon exists in the water

zr in rutile thermometry in eclogite and vein from southwestern tianshan china abstract trace element la icpms analyses of rutile from eclogites and veins from southwestern tianshan china are carried out for testing the validity of zr in rutile thermometry in low t uhp eclogites mineral inclusions in rutile and time resolved mass spectrometer data are carefully examined to identify and reject contaminated data the zr contents vary between individual grains from the same sample rutile inclusions in garnet amphibole and paragonite have a narrower range of zr contents than matrix rutiles that always show the highest zr contents which reflects the progressive rutile growth in the eclogites average zr concentrations in rutile from all six investigated eclogite samples statistically belong to one well defined population 34 5 ppm 33 11 ppm 26 7 ppm 36 17 ppm 22 6 ppm 40 17 ppm while average zr concentration in rutile from the three veins belong to a second well defined population 55 7 ppm 66 6 ppm 55 5 ppm the peak temperature of eclogite can be estimated as 535 570 c at a pressure of 2 7 gpa inverted from the discovery of well preserved coesite in an increasing number of rocks from southwestern tianshan the mineral assemblage of the veins suggests their retrograde formation in the epidote amphibolite facies the growth temperature of vein rutile is 530 540 c at 1 0 gpa a robust p t path constructed by zr in rutile thermometry in eclogites and veins indicates that the rocks underwent a rapid uplift involving an early isothermal decompression from eclogite to epidote amphibolite facies zr in rutile from eclogites and veins can serve as a pressure indicator in study area that suggests the pressure has a significant effect to the zr in rutile thermometry

tectonics of south china key to understanding west pacific geology abstract south china is not a post caledonian platform but a composite of orogenic belts this late proterozoic mesozoic orogen is a collage of three continental fragments the three blocks are yangzi huanan and dongnanya and they are separated by the banxi nanpanjiang formerly xianggangzhe and gunanhai suture zones yangzi was separated from gondwanaland during late precambrian when an open ocean called banxi was present between the two continents tectonic processes at an active margin during sinian and early paleozoic time led to the genesis of an accretionary wedge complex the banxi melange and the huanan flysch nappes on the northern margin of huanan which was then the northern margin of the gondwana continent reorganization of plates during the devonian suspended subduction at the huanan active margin huanan was uplifted and unconformably overlain by transgressive deposits of devonian and or carboniferous age a remnant ocean the nanpanjiang sea still existed between yangzi and huanan and deep water sedimentation continued both at the southern margin of yangzi and at the northwestern margin of huanan the latter again became an active margin during late paleozoic when permian and triassic flysch sediments were deposited in foredeeps ahead of advancing nappes huanan and yangzi collided during the triassic and resulted in the deformation of the passive margin of the latter to form the yangzi deformed belt huanan was separated from a more southerly continent dongnanya in the devonian by seafloor spreading which created a late paleozoic and early mesozoic ocean gunanhai ocean a continuously deposited sequence ranging in age from devonian to triassic was laid down on the southern passive margin of huanan on the other side of the ocean the dongnanya permian strata include glacial marine deposits of gondwanaland affinity dongnanya became separated from gondwanaland during the late permian when it marched northward to be reunited with huanan the huanan passive margin sequence was deformed by folding and overthrusting after the late mesozoic collision of huanan and dongnanya scattered outcrops of the suture melange resulting from this collision occur at a few localities in coastal fujian dongnanya in our model was the mesozoic continent of southeast asia peripheral to mainland asia this may or may not have been the eastern continuation of the microcontinent sibumasu siam thailand burma malaysia sumatra the collision of dongnanya and asia gave rise not only to the gunanhai melange of coastal fujian but also to the ophiolite melanges parts of which are present in taiwan tailuko the philippines and western malaysia

origin and evolution of w mo producing fluids in a granitic hydrothermal system geochemical studies of quartz vein deposits around the susan granite hwanggangri district republic of korea the hwanggangri mineralized district is located approximately 130 km southeast of seoul within the paleozoic ogcheon belt of south korea the jungbo suri and deogman mines in the district occur around the late cretaceous whole rock k ar age 89 0 or 2 0 ma susan granite and are located on w mo bearing quartz veins these veins fill fractures in the granite and its host rocks which comprise early paleozoic limestone rich sedimentary rocks the k ar date of vein muscovite 88 58 or 1 95 ma is very similar to that of the susan granite 89 04 or 1 95 ma indicating that w mo mineralization was associated with intrusion of the granite molybdenite and wolframite rich deposits occur within or near 285 degrees c from h 2 o co 2 fluids with salinities of 0 4 to 9 7 wt percent nacl equiv probably in response to ph increase due to boiling including co 2 unmixing of the hydrothermal fluid at pressures between 150 and 220 bars following w mo deposition the high temperature fluids gave way to progressively cooler more dilute fluids associated with scheelite base metal sulfide deposition 200 degrees 320 degrees c 0 7 7 2 wt nacl equiv and carbonate fluorite deposition 105 degrees 225 degrees c 0 0 3 2 wt nacl equiv these trends are interpreted as the result of progressive mixing of magmatic fluids with cooler more dilute meteoric waters there is a systematic decrease in the measured and calculated isotopic compositions of hydrothermal waters with increasing paragenetic time and decreasing temperature stage i delta 18 o water 8 0 to 1 5 per mil and delta d water 56 to 74 per mil stage ii delta 18 o water 1 9 to 5 6 per mil and delta d water 88 to 95 per mil stage iii delta 18 o water 0 9 to 3 0 per mil and delta d water 93 to 97 per mil the trend reflects the progressive increase of meteoric water involvement in the mineralizing system during the cooling history of the susan granite stock molybdenum and tungsten were partitioned preferentially into a coexisting magmatic hydrothermal fluid delta 18 o 8ppm delta d 56 to 72ppm sulfur isotope analyses of hydrothermal sulfide minerals suggest an igneous source of sulfur with a delta 34 s sub sigma s value near 4 per mil following deposition of molybdenite and wolframite from magmatic fluids wolframite was dissolved or replaced by scheelite in the outer and or shallower portions of the hydrothermal system this remobilization of tungsten and later redeposition as scheelite at temperatures of 200 degrees 280 degrees c from fluids with delta 18 o 1 2ppm accompanied mixing with low temperature meteoric fluids increasing involvement of progressively larger volumes of meteoric water resulted in successive deposition of base metal sulfides fluorite and carbonates

ore forming fluids and metallogenesis of nanyangtian tungsten deposit in laojunshan southeastern yunnan province the nanyangtian tungsten deposit is located in the tungsten tin polymetallic ore forming area in laojunshan southeastern yunnan province ore bodies fairly simple in shape are largely concordant with the bedding of the strata and the distribution of the ore bodies is spatially related to skarn the formation of tungsten deposit experienced a period composed of skarn phase and quartz sulfide phase the skarn phase is divided into skarn stage and retrogressive alteration stage whereas the quartz sulfide phase consists of two stages called respectively quartz sulfide stage and calcite sulfide stage tungsten mineralization probably occurred at the retrogressive alteration stage there are three dominant types of fluid inclusions as evidenced by petrographic characteristics of fluid inclusions of garnet epidote quartz fluorite and calcite formed at different oreforming stages in the nanyangtian tungsten deposit they are liquid rich inclusions gas rich two phase inclusions and daughter minerals bearing polyphase inclusions systemmatic measurement of homogeneous and freezing temperatures as well as salinities and laser raman spectroscopic analysis of fluid inclusions were conducted the gas compositions of ore forming fluids in the nanyangtian tungsten deposit are mostly h2o ch4 and n2 with a small amount of co2 whereas the liquid composition is primarily h2o fluid inclusions in the skarn phase show homogenization temperatures and salinities w nacleq from 260 to 420 and from 6 45 to 53 26 respectively with the densities ranging from 0 83 g cm3 to 1 15 g cm3 homogenization temperatures and salinities w nacleq of fluid inclusions in the quartz sulfide phase mainly vary from 160 to 300 and from 4 to 8 respectively and the densities of the fluids are 0 67 0 96 g cm3 which are obviously lower than the data of the fluid inclusions in the skarn phase the 18osmow values of garnet quartz and calcite range from 3 78 to 16 23 with the corresponding 18oh2o values between 4 52 and 10 28 and d values of fluid inclusions between 83 and 59 the combined isotopic data imply that the ore forming fluids in the nanyangtian tungsten deposit were mainly derived from magmatic fluids the 34s values of pyrite from the nanyangtian tungsten deposit vary in a narrow range of 4 2 8 1 reflecting the derivation of sulfur from deep magma source tungsten mineralization in the nanyangtian ore deposit took place in late triassic with its metallogenesis related to the magmatic activity during the indosinian period

mesozoic molybdenum deposits in the east qinling dabie orogenic belt characteristics and tectonic settings abstract the east qinling dabie orogenic belt accommodates the largest mo ore district in the world it contains 8 43 mt of proven mo metal reserves which accounts for 66 of the total proven chinese mo reserves the mo ore district includes 24 deposits and 12 occurrences with four major types of mo mineral systems i e porphyry porphyry skarn skarn and hydrothermal veins the latter can be further subdivided into quartz vein and carbonatite vein types although mo mineralization in the belt began in the paleoproterozoic 1680 24 to 2044 14 ma all economically significant deposits were formed during the mesozoic re os dating of molybdenite has shown that there are three episodes of mo mineralization i e late triassic 233 221 ma late jurassic to early cretaceous 148 138 ma and early to middle cretaceous 131 112 ma late triassic mo deposits developed as molybdenite quartz veins and carbonatite vein types stable isotope systematics c o s and high contents of re and sr indicate that the carbonatite mo veins are mantle derived porphyry and porphyry skarn mo mineral deposits were formed in the late jurassic to early cretaceous and early to middle cretaceous the late jurassic to early cretaceous granite porphyries that are associated with the mo deposits usually occupy less than 1 5 km2 at the surface and are situated in the east qinling area far west of china s continental margin on the other hand the early to middle cretaceous batholiths and granite porphyries with associated mo deposits are located in the dabieshan area and eastern part of the east qinling area the late jurassic to early creataceous granitoids and related mo deposits possibly formed in a back arc extensional setting of the eurasian continental margin which was probably triggered by the oblique subduction of the izanagi plate the early to middle cretaceous batholiths and granite porphyries are linked to the tectonic regime of lithospheric thinning asthenospheric upwelling and partial melting of the crust induced by a change in izanagi plate motion parallel to the continent margin in the east qinling dabie belt there are vein type pb zn ag deposits surrounding porphyry and or porphyry skarn mo w deposits forming well defined ore clusters the same spatial arrangement i e porphyry mo stockworks and outlying pb zn ag ore veins is also observed at the deposit scale thus mo porphyry stockworks and distal polymetallic veins belong to the same ore system and may reflect an outward temperature decrease from the highly fractionated granite plutons both porphyry stockworks and polymetallic veins can be used as vectors for further prospecting

possibilities and limits of infrared light microthermometry applied to studies of pyrite hosted fluid inclusions pyrites from various occurrences and of different origin have been examined for fluid inclusions using an infrared microscope additionally fourier transform infrared spectroscopy was performed in order to characterize the infrared transmittance of individual samples in the spectral range of the ir tv camera l f 2 5 mm used studied samples of sedimentary pyrite are always opaque for near infrared light whereas pyrite from metamorphic rocks hydrothermal ore deposits and pegmatites shows infrared transmittance of varying degree pyrite hosted fluid inclusions are often opaque and only a few samples contain fluid inclusions which are suitable for microthermometric investigations ice melting temperatures of fluid inclusions in pyrite from three different occurrences were measured by direct observation on a monitor screen when heating the infrared transparency of pyrite decreases with increasing temperature due to shifting of the absorption edge to higher wavelengths therefore most of the pyrites became opaque prior to reaching l v homogeniza tion the only combined salinity and homogenization temperature data for fluid inclusions were obtained from pyrite samples from an argillic altered shear zone within the murgul cu depositrne turkey these pyrite crystals show up to 40 transmittance for infrared radiation in the wavelength range l s 0 8 to 2 5 mm homogenization temperatures th were measured visually up to temperatures of about 2508c at higher temperatures the pyrite samples became completely opaque and th values of fluid inclusions were obtained by a cycling technique the data obtained from fluid inclusions as well as observed small fractionation of sulfur isotopic composition indicate that pyrite crystals with different morphologies octahedrons pentagondodecahedrons and combinations of both from murgul were deposited at different temperatures q 1999 elsevier science b v all rights reserved

fluid inclusion studies in quartz veinlets in the porphyry copper deposit at sungun east azarbaidjan iran abstract the porphyry copper deposit pcd at sungun is located in east azarbaidjan in the nw of iran the sungun porphyries occur as stocks and dikes ranging in composition from quartz monzodiorite through quartz monzonite and granodiorite to granite the stocks are divided into two groups 1 porphyry stocks i and 2 porphyry stock ii porphyry stock ii hosting the copper ore experienced intense hydro fracturing leading to the formation of stockwork type and anastomozing veinlets and micro veinlets of quartz sulfides carbonates and sulfates three distinct types of hydrothermal alteration and sulfide mineralization are recognized at sungun 1 hypogene 2 contact metasomatic skarn and 3 supergene four types of hypogene alteration are developed at sungun potassic propylitic potassic phyllic and phyllic four types of inclusion are common at sungun based upon their phase content 1 mono phase vapor 2 vapor rich 2 phase 3 liquid rich 2 phase and 4 multi phase solid halite is the principal solid phase the distribution pattern shape and phase contents of fluid inclusions in quartz veinlets at sungun are analogous to those from bingham and globe miami in western usa the fluid inclusion data at sungun showed that the liquid vapor homogenization temperature t h l v values for liquid rich 2 phase vapor rich 2 phase and halite bearing inclusions vary from 160 to 580 c from 200 to 600 c and from 160 to 580 c respectively the ascending unboiled fluid at the onset of the phyllic alteration episode had temperatures 580 c and was moderately saline 15 wt with the gradual decrease in temperature the salinity of this fluid gradually decreased so that its salinity at temperatures of 370 and 350 c the residual fluid remained undersaturated with respect to nacl however at temperatures t s nacl t h l v showed that they were developed under the maximum hydrostatic pressure head of 1500 m during the boiling events

pb diffusion in rutile diffusion of pb was measured in natural and synthetic rutile under dry 1 atmosphere conditions using mixtures of pb titanate or pb sulfide and tio2 as the sources of diffusant pb depth profiles were then measured with rutherford backscattering spectrometry rbs over the temperature range 700 1100 c the following arrhenius relation was obtained for the synthetic rutile d 3 9 10 10exp 250 12 kj mol 1 rt m2s 1 results for diffusion in natural and synthetic rutile were quite similar despite significant differences in trace element compositions mean closure temperatures calculated from the diffusion parameters are around 600 c for rutile grains of 100 m size this is about 100 c higher than rutile closure temperature determinations from past field based studies suggesting that rutile is more resistant to pb loss through volume diffusion than previously thought

analysis of tide and offshore storm induced water table fluctuations for structural characterization of a coastal island aquifer analysis of water table fluctuations can provide important insight into the hydraulic properties and structure of a coastal aquifer system including the connectivity between the aquifer and ocean this study presents an improved approach for characterizing a permeable heterogeneous coastal aquifer system through analysis of the propagation of the tidal signal as well as offshore storm pulse signals through a coastal aquifer offshore storms produce high wave activity but are not necessarily linked to significant onshore precipitation in this study we focused on offshore storm events during which no onshore precipitation occurred extensive groundwater level data collected on a sand barrier island sable island ns canada show nonuniform discontinuous propagation of the tide and offshore storm pulse signals through the aquifer with isolated inland areas showing enhanced response to both oceanic forcing signals propagation analysis suggests that isolated inland water table fluctuations may be caused by localized leakage from a confined aquifer that is connected to the ocean offshore but within the wave setup zone two dimensional groundwater flow simulations were conducted to test the leaky confined unconfined aquifer conceptualization and to identify the effect of key parameters on tidal signal propagation in leaky confined unconfined coastal aquifers this study illustrates that analysis of offshore storm signal propagation in addition to tidal signal propagation provides a valuable and low resource approach for large scale characterization of permeable heterogeneous coastal aquifers such an approach is needed for the effective management of coastal environments where water resources are threatened by human activities and the changing climate

fluid evolution in the w cu zn pb san cristobal vein peru fluid inclusion and stable isotope evidence abstract the zn pb ag cu san cristobal district is located 100 km east of lima in the western cordillera of peru it is centred around the chumpe intrusion and is composed of vein and carbonate replacement ore types the main san cristobal vein presents a paragenesis that can be divided into three stages a an early wolframite quartz pyrite stage b a quartz base metal stage and c a late quartz carbonate barite stage fluid inclusions in quartz from the tungsten stage are biphase lv at room temperature and homogenise to the liquid phase between 146 and 257 c their salinities range between 2 1 and 5 1 wt nacl equiv rare inclusions contain an additional crystal of halite and have salinities of 46 54 wt nacl equiv data of the first two stages show a decrease in homogenisation temperatures concomitant with a salinity decline fluid inclusions in quartz from the late stage homogenise at higher temperatures between 252 and 323 c with salinities ranging between 4 6 and 6 7 wt nacl equiv hydrogen and oxygen isotope data indicate a two stage evolution isotopic compositions of the fluid associated with the first two stages define a trend with constant 18 o values and decreasing d values 18 o 3 2 to 5 0 v smow and d 60 to 112 v smow which is interpreted as mixing of a dominantly magmatic component with minor meteoric water that had equilibrated with the host rocks this interpretation is supported by sulphur and lead isotopic data from previous studies by contrast the quartz carbonate barite stage bears isotopic characteristics defining a trend with a coupled decrease of 18 o and d 18 o 8 1 to 2 5 v smow and d 57 to 91 v smow and is explained by addition of meteoric water to the system and subsequent mixing with a less important magmatic component different fluid origins are confirmed by laser ablation icp ms analyses of the triphase lvh and biphase lv primary inclusions the concentrations of the major ore elements i e w cu zn and pb decrease throughout the paragenesis w and to a lesser extent cu show significant variations associated with a steep decrease in their concentration the decreasing concentrations can be explained by mineral deposition and dilution by the meteoric fluid differences in the rate of decrease indicate selective precipitation of w fluid inclusions of the quartz carbonate stages show an abrupt increase in ba and sr concentrations this is interpreted to reflect a higher volume of host rock silicate alteration probably due to the increasing size of the fluid flow cell and is explained by the input of a third fluid of unknown origin la icp ms analyses show that the fluids were already depleted in w and cu before reaching the emplacement of carbonate replacement ore type whereas zn and pb were still present in considerable amounts this is again due to selective precipitation and is consistent with the interpretation that the economically interesting metals were dominantly introduced by magmatic fluids

freshwater lens formation below juvenile dunes on a barrier island spiekeroog northwest germany abstract morphodynamic changes of barrier islands and the consequences for underlying freshwater reservoirs are of major interest for coastal environments and drinking water supply in coastal areas here a geomorphological and hydrological reconstruction of dune formation on a barrier island and their freshwater reservoirs is presented the aim was to provide an integrated analysis of the co evolution of dunes and freshwater resources during the development of a barrier island the study area is the eastern part of spiekeroog island the so called ostplate at the northwest german coast that expanded significantly in the last 360 years due to coastal land reclamation the first dune growth was initiated in the 1940s at the newly formed sand flat and dune freshening started around 1970 pore water measurements in november 2011 march and august 2012 confirm the existence of freshwater below the dune area and indicate a landward movement of the freshwater saltwater interface in winter and a seaward movement in summer respectively in response to storms and corresponding coastal flooding a density dependent groundwater flow model was used to estimate the present thickness and shape of the lenses as well as to reconstruct the evolution of the freshwater reservoirs the simulations suggest an asymmetric lens shape with a freshwater discharge tube below the beach to the sea and an extended brackish transition zone below the salt marsh area towards the tidal flat the simulation results also indicate that the freshwater reservoirs are still in a stage of development after 40 years of simulation time and are estimated to reach steady state after about 300 500 years under the given conditions without taking into account possible impacts of climate change

u pb zircon geochemical and sr nd hf isotopic constraints on age and origin of jurassic i and a type granites from central guangdong se china a major igneous event in response to foundering of a subducted flat slab abstract the mesozoic geology of se china is characterized by widespread jurassic to cretaceous igneous rocks consisting predominantly of granites and rhyolites and subordinate mafic lithologies however the tectonic regime responsible for the inland jurassic granites remains controversial we report here u pb zircon ages geochemical and sr nd hf isotopic data for the nankunshan alkaline granite and the fogang granitic batholith in central guangdong mineralogical and geochemical features suggest that the fogang and nankunshan rocks are i and aluminous a type granites respectively shrimp u pb zircon analyses yield consistent ages ranging from 159 3 ma to 165 2 ma for four samples from the fogang batholith and an age of 158 5 ma for the nankunshan granite the fogang granites having i sr 0 7098 0 7136 e nd t 4 3 to 12 2 and e hf t 11 5 to 3 1 for the magmatic zircons were derived from paleoproterozoic mafic intermediate igneous protolith with minor addition of mantle derived magmas the nankunshan rocks have relatively lower i sr 0 706 0 708 higher e nd t 0 3 to 2 4 and e hf t 5 7 to 1 1 for the magmatic zircons and some oib like trace element ratios they were likely generated through extensive fractional crystallization of mantle derived alkaline parental magma associated with crustal assimilation these 160 ma i and a type granites in central guangdong were emplaced coeval with the widespread 165 155 ma i and a type granites and syenites following the initiation of intraplate basaltic and or bimodal igneous magmatism at 180 170 ma in the adjacent regions we interpret these jurassic igneous rocks as anorogenic magmatism formed during a major igneous event in response to foundering of an early mesozoic subducted flat slab beneath se china continent

porphyry cu au mo epithermal ag pb zn distal hydrothermal au deposits in the dexing area jiangxi province east china a linked ore system abstract based on previous studies and detailed field investigations of the dexing porphyry copper deposit the yinshan ag pb zn deposit and the jinshan shear zone hosted gold deposit in the dele jurassic volcanic basin in the northeastern jiangxi province east china we propose that the three deposits share spatial temporal and genetic relationships and belong to the same metallogenic system dexing is a typical porphyry cu au mo deposit in which both ore forming fluid and metals are derived from the granite porphyry the yinshan deposit consists of a porphyry copper ore located in the cupola of a quartz porphyry stock in the lower part and ag pb zn ore veins in the upper part the hydrothermal fluids were mainly derived from the magma in the early stages of the mineralizing event and became mixed with meteoric waters in the late stages its ore metals are magma derived both the jinshan base metal veins and the hamashi dongjie and naikeng quartz vein type gold deposit are hosted by brittle ductile structures which are distal in relation to the porphyry intrusions and were formed by mixed magmatic fluids and meteoric water whereas the gold was mainly leached from the country rocks mesoproterozoic shuangqiaoshan group phyllite and schist the deposits show a distinct spatial arrangement from porphyry cu to epithermal ag pb zn and distal au we suggest a porphyry epithermal distal vein ore system model for this group of genetically related mineral deposits they were formed in a back arc setting in a middle jurassic active continental margin with magmas derived from the subducted slab

petrology of ultrahigh pressure rocks from the southern su lu region eastern china abstract in the su lu ultrahigh p terrane eastern china many coesite bearing eclogite pods and layers within biotite gneiss occur together with interlayered metasediments now represented by garnet quartz jadeite rock and kyanite quartzite in addition to garnet omphacite rutile coesite other peak stage minerals in some eclogites include kyanite phengite epidote zoisite talc nyboite and high al titanite the garnet quartz jadeite rock and kyanite quartzite contain jadeite quartz garnet rutile zoisite apatite and quartz kyanite garnet epidote phengite rutile omphacite assemblages respectively coesite and quartz pseudomorphs after coesite occur as inclusions in garnet omphacite jadeite kyanite and epidote from both eclogites and metasediments study of major elements indicates that the protolith of the garnet quartz jadeite rock and the kyanite quartzite was supracrustal sediments most eclogites have basaltic composition some have experienced variable crustal contamination or metasomatism and others may have had a basaltic tuff or pyroclastic rock protolith the su lu ultrahigh p rocks have been subjected to multi stage recrystallization and exhibit a clockwise p t path inclusion assemblages within garnet record a pre eclogite epidote amphibolite facies metamorphic event ultrahigh p peak metamorphism took place at 700 890 c and p 28 kbar at c 210 230 ma the symplectitic assemblage plagioclase hornblende epidote biotite titanite implies amphibolite facies retrogressive metamorphism during exhumation at c 180 200 ma metasedimentary and metamafic lithologies have similar p t paths several lines of evidence indicate that the supracrustal rocks were subducted to mantle depths and experienced in situ ultrahigh p metamorphism during the triassic collision between the sino korean and yangtze cratons

trace element and sr nd isotope geochemistry of fluorite from the xiangshan uranium deposit southeast china the trace element and sr nd isotope geochemistry of fluorite have been investigated in the xiangshan volcanic rock hosted uranium deposit in southeast china detailed sr nd isotope data of the hydrothermal fluorite closely associated with the uranium mineralization suggest that ore forming fluids were a combination of mantle derived fluid and fluids equilibrated with basement metamorphic rocks this model is consistent with previously published h o isotope data and is incompatible with meteoric water as the only ore forming fluid trace element geochemical profiles across the uranium orebody can be interpreted to reflect reaction between the host rocks and a mantle derived fluid containing high u and th with low th u ratios the mantle derived fluid is considered to have been u f and carbonate rich mixing with shallowly circulated meteoric water within the fractures of the host volcanic rocks caused dilution and cooling of the ore forming fluid and subsequent precipitation of fluorite and uranium ore