geochemistry and geochronology of paleozoic intrusions in the nalati narati area in western tianshan xinjiang china implications for paleozoic tectonic evolution abstract the nalati narati area in the chinese western tianshan is characterized by abundant paleozoic intrusions including granites diorites and gabbros they are not only indicators of the interaction between crust and mantle but also useful clues for tracing the tectonic history of the tianshan orogen most early paleozoic granitoids biotite monzonitic granites and muscovite granites of this study are from the yili block the biotite monzonitic granites mixed source derived i type granites have a zircon u pb age of 497 0 5 9 ma indicating the time of the subduction of the terskey oceanic crust in the late cambrian the 427 2 5 7 ma zircon u pb age of the s type muscovite granites let us interpret that these granites may have been formed during the crust thickening process after the collision between the yili block and the nalati block in western tianshan the late paleozoic biotite granites muscovite granites quartz diorites biotite monzonitic granites granodiorites and alkali granites have respectively a la icpms zircon u pb age of 371 8 6 ma 357 2 7 5 ma 313 9 2 5 ma and 296 9 2 4 ma the biotite granites display i type geochemical features and are considered to have been derived from a lower continental crust source the muscovite granites have a pronounced s type affinity and are considered to have been formed by the partial melting of thickened continental crust after the collision between the central tianshan belt and the south tianshan belt the quartz diorites are adakite like and have an i type affinity which are considered to have been formed by partial melting of a delaminated lower crust in a post orogenic extension setting the granodiorites also show some typical geochemical features of adakite their formation is considered to be related to the lower crustal delamination and the ascending of asthenosphere after the collision event the alkali granites show an a type granite affinity they may have been formed in a within plate tectonic setting and possibly related to rifting as a consequence of extension the gabbros can be divided into two groups based on their geochemical characteristics and ages the older gabbros 415 429 ma with lower tio 2 contents are formed in an arc related setting the younger ones 340 318 ma with higher tio 2 content are formed in an intracontinental setting and influenced by crustal contamination magmatic activities recorded by paleozoic intrusions can constrain the tectonic history of the tianshan region from subduction of oceanic crust to intraplate extensional collapse and to rifting and can also corroborate that the final closure of the south tianshan ocean occurred in the late devonian early carboniferous time

the origin and evolution of skarn forming fluids from the phu lon deposit northern loei fold belt thailand evidence from fluid inclusion and sulfur isotope studies abstract the phu lon skarn cu au deposit is located in the northern loei fold belt lfb thailand it is hosted by devonian volcano sedimentary sequences intercalated with limestone and marble units intruded by diorite and quartz monzonite porphyries phu lon is a calcic skarn with both endoskarn and exoskarn facies in both skarn facies andradite and diopside comprise the main prograde skarn minerals whereas epidote chlorite tremolite actinolite and calcite are the principal retrograde skarn minerals four types of fluid inclusions in garnet were distinguished 1 liquid rich inclusions 2 daughter mineral bearing inclusions 3 salt saturated inclusions and 4 vapor rich inclusions epidote contains only one type of fluid inclusion liquid rich inclusions fluid inclusions associated with garnet prograde skarn stage display high homogenization temperatures and moderate salinities 421 6 468 5 c 17 4 23 1 wt nacl equiv by contrast fluid inclusions associated with epidote retrograde skarn stage record lower homogenization temperatures and salinities 350 9 399 8 c 0 5 8 wt nacl equiv these data suggest a possible mixing of saline magmatic fluids with external dilute fluid sources e g meteoric fluids as the system cooled some fluid inclusions in garnet contain hematite daughters suggesting an oxidizing magmatic environment sulfur isotope determinations on sulfide minerals from both the prograde and retrograde stages show a uniform and narrow range of 34 s values 2 6 to 1 1 34 s suggesting that the ore forming fluid contained sulfur of orthomagmatic origin overall the phu lon deposit is interpreted as an oxidized cu au skarn based on the mineralogy and fluid inclusion characteristics

high salinity fluid inclusions in the yinshan polymetallic deposit from the le de metallogenic belt in jiangxi province china their origin and implications for ore genesis a fluid inclusion investigation of the polymetallic mineralization at yinshan from the le de metallogenic belt in jiangxi province of china has been carried out using petrographic and microthermometric techniques the data obtained here indicate that three major types of fluids were involved during the formation of the deposit they are type i vapor rich type ii liquid rich and type iii halite bearing inclusions within the h2o nacl system the high salinity fluids represented by type iii inclusions being unusual to the distal part of an intrusion centered ore forming system such as yinshan have been interpreted as the product of direct exsolution of a crystallizing magma rather than a result of fluid immiscibility from a low salinity fluid evidence used to support such an interpretation includes the mode of homogenization of type iii inclusions exclusively via halite dissolution spatial separation of type i and type iii inclusions on microscopic scale the consistent phase ratios within the inclusions concerned and considerable deviation in homogenization temperature for both type i and type iii inclusions trapping conditions for type i inclusions were estimated to be around 440 degrees c and 260 bars while type iii inclusions were constrained to be trapped at least above 900 bars and 500 degrees c the formation temperatures for type ii inclusions range from 270 to 390 degrees c if a lithostatic pressure of 260 bars is assumed pressure fluctuation determined by this fluid inclusion study coupled with decreases in salinity and temperature as result of the potential fluid mixing are supposed to have played an important role in triggering the precipitation of ore minerals from the hydrothermal solution c 2006 elsevier b v all rights reserved

geological characteristics and metallogenesis of iron deposits in western tianshan china abstract the western tianshan metallogenic belt is one of the most significant polymetallic iron metallogenic belts in china important advances have been achieved recently in iron exploration in the awulale mountain in western tianshan china these newly discovered iron deposits are mainly hosted in the basic medium andesitic lavas and volcaniclastics often comprising a number of high grade ores magnetite is predominated in ore mineral assemblages and pyrite chalcopyrite pyrrhotite or sphalerite increase in certain deposits wallrock alterations are intensively developed exemplified as sodic calcic and potassic alterations which display in different patterns as country rocks and ore controlled structures vary skarn assemblages are commonly developed in ore districts like beizhan dunde and chagangnuoer and pyroxene albite k feldspar epidote actinolite alterations are dominated around ore bodies in zhibo deposit whereas the shikebutai deposit develops alteration assemblages comprising of jasper barite sericite and chlorite thus iron deposits can be divided into three types including volcanic sedimentary type volcanic magmatic hydrothermal type and iron skarn type our preliminary interpretation about the tectonic background of this iron mineralization in this area is in the late stage of a collisional accretional orogenic belt around carboniferous with some extrusional extensional tectonic transition locally iron mineralization is likely to have a close genetic relationship with volcanic subvolcanic activity syn or slightly post the volcanism which took place besides continental arc volcanic eruption contributes to majority of mineralizing iron with minor extracted from hydrothermal replacement from wall rocks

evolution of calc alkaline to alkaline magmatism through carboniferous convergence to permian transcurrent tectonics western chinese tianshan continuous magmatic activity occurred in the western chinese tianshan central asia from the carboniferous to the permian i e before and after the late carboniferous amalgamation of junggar and the yili blocks zircon u pb la icpms and ar ar data reveal a coincidence in time between regional wrench faulting and granitoid emplacement permian post collisional granitoids crop out within or at the margins of large scale dextral strike slip shear zones some of them show synkinematic fabrics the whole rock geochemical features of the early middle permian granitoids indicate an evolution from high k calc alkaline towards alkaline series in other places of the north tianshan alkaline magmatism occurred together with deep marine sedimentation within elongated troughs controlled by wrench faults therefore in contrast with previous interpretations that forwarded continental rift or mantle plume hypotheses the coexistence of diverse magmatic sources during the same tectonic episode suggests that post collisional lithosphere scale transcurrent shearing tightly controlled the magmatic activity during the transition from convergent margin to intraplate anorogenic processes

lead isotope variations across terrane boundaries of the tien shan and chinese altay the altaid orogen was formed by aggregation of paleozoic subduction accretion complexes and precambrian basement blocks between the late proterozoic and the early mesozoic because the altaids are the site of abundant granitic plutonism and host some of the largest gold deposits in the world understanding their formation has important implications on the comprehension of phanerozoic crustal growth and metallogeny in this study we present the first extensive lead isotope data on magmatic and metasedimentary rocks as well as ore deposits of the southern part of the altaids including the tien shan tianshan and southern altay altai orogenic belts our results show that each terrane investigated within the tien shan and southern altay is characterized by a distinct pb isotope signature and that there is a sw ne pb isotope gradient suggesting a progressive transition from a continental crust environment in the west the kyzylkum and kokshaal segments of the southern tien shan to an almost 100 juvenile morb type mantle derived crust environment in the east altay the pb isotope signatures of the studied ore deposits follow closely those of magmatic and metasedimentary rocks of the host terranes thus supporting the validity of lead isotopes to discriminate terranes whereas this apparently suggests that no unique reservoir has been responsible for the huge gold concentration in this region masking of a preferential pb poor au bearing reservoir by mixing with pb rich crustal reservoirs during the mineralizing events cannot be excluded

ore genesis and hydrothermal evolution of the kendenggao er copper molybdenum deposit western tianshan evidence from isotopes s pb h o and fluid inclusions abstract the boluokenu range is one of the most important metallogenic belts in northwest china and it contains numerous fe cu mo au etc deposits the kendenggao er cu mo deposit is located in the eastern segment of the boluokenu metallogenic belt within the western tianshan orogeny skarn and cu mo orebodies occur as lamellae or lenses along the contacts between different units of the upper carboniferous dongtujinhe formation and the aimujin granitic intrusions based on field investigations and petrographic observations three main metallogenic stages of skarn formation and ore deposition have been distinguished 1 the pre ore stage is characterized by the formation of garnet wollastonite and diopside and high temperature hypersaline hydrothermal fluids with oxygen isotopic compositions that are similar to those of magmatic fluids these fluids were most likely generated by the separation of brine from the silicate melt due to the immiscibility of primary magmatic fluids that occurred at a depth of approximately 1 km with inferred lithostatic pressure conditions of 300 bars 2 the main ore stage coincides with the replacement of garnet and diopside by vesuvianite epidote sulfides and quartz the hydrothermal fluids of this stage are represented by v type vapor rich fluid inclusions that coexist with l type liquid rich inclusions the oxygen isotope 18oh2o values of the main ore stages are in a narrow range of 7 5 9 9 which indicates that the mineralization related fluid is also of magmatic origin based on the fluid inclusion and stable isotopic data it can be concluded that the ore forming fluid evolved by the boiling of the magmatic fluids that likely occurred at a depth of 1 km and hydrostatic pressure of 100 bars and that this was the predominant mechanism for the large scale precipitation in the kendenggao er cu mo deposit 3 the post ore stage is characterized by the development of calcite quartz and chlorite the fluids during this stage are represented by the l type inclusions which mainly show low salinity and low homogenization temperatures these fluids yield the lowest 18oh2o values 2 8 to 3 7 the above data indicate that the post ore stage fluids originated from the mixing of residual main ore stage fluids with various proportions of external water low salinity low temperature no boiling occurred at this stage at the low temperatures the 34s values of the sulfides range from 4 3 to 1 9 and the 206pb 204pb 207pb 204pb and 208pb 204pb values of the sulfides range from 18 220 to 18 554 15 608 to 15 812 and 38 080 to 39 055 respectively the s and pb isotopic compositions indicate that the ore materials were mainly derived from magmas taken together these geologic geochemical and isotopic data confirm that kendenggao er is a typical skarn deposit

geochronology and fluid inclusion studies of the lailisigaoer and lamasu porphyry skarn cu mo deposits in northwestern tianshan china abstract the lailisigaoer porphyry mo cu and lamasu porphyry skarn cu deposits are located in the northwestern tianshan orogenic belt which is in the northwestern china according to re os analysis of molybdenite the time of mineralization of the lailisigaoer deposit is 377 ma and shrimp zircon u pb analysis dates the ore hosted intrusion of the lamasu deposit to 378 ma five types of fluid inclusions fis have been identified in both deposits h 2 o rich inclusions co 2 bearing inclusions halite bearing inclusions methane rich inclusions and pure co 2 inclusions in the lailisigaoer deposit the early stage fluid of the quartz phenocryst belongs to a nacl h 2 o system with total homogenization temperatures t h ranging from 300 to 395 c with a mean salinity of 9 0 wt nacl in the ore forming stage the fluid develops into a h 2 o nacl co 2 system due to boiling and decarbonation the t h values and salinities cluster between 220 and 370 c and between 0 and 33 0 wt nacl respectively the hydrothermal characteristics of the late quartz calcite stage are similar to those of the meteoric fluid in the lamasu deposit the early stage fluid of the quartz phenocryst belongs to a nacl h 2 o system with t h values ranging from 245 to 459 c and a mean salinity of 6 0 wt nacl in the ore forming stage due to the contact metamorphism between the hydrothermal fluid and wall rock the fluid evolves to a nacl h 2 o ch 4 system the t h values and salinities cluster between 220 and 360 c and between 0 and 17 3 wt nacl respectively the fluid of the late quartz sulfide stage coincides with the meteoric fluid in the mineralizing fluid of the lailisigaoer deposit the captured temperatures and pressures are between 210 and 350 c and between 170 and 600 bars respectively which are consistent with fluctuation between hydrostatic and lithostatic pressure corresponding to the estimated paleodepths of 1 7 2 2 km boiling is the dominant mineralizing mechanism in the lailisigaoer deposit whereas the contact metamorphism between the magmatic hydrothermal fluid and country rocks is the dominant mechanism in the lamasu deposit both deposits are formed in the continental arc setting related to the southward subduction of the north tianshan oceanic slab beneath the yili central tianshan block

palaeozoic collisional tectonics and magmatism of the chinese tien shan central asia abstract the chinese tien shan range is a palaeozoic orogenic belt which contains two collision zones the older southern collision accreted a north facing passive continental margin on the north side of the tarim block to an active continental margin on the south side of an elongate continental tract the central tien shan collision occurred along the qinbulak qawabulak fault southern tien shan suture the time of the collision is poorly constrained but was probably in in the late devonian early carboniferous we propose this age because of a major disconformity at this time along the north side of the tarim block and because the youshugou ophiolite is imbricated with middle devonian sediments a younger probably late carboniferous early permian collision along the north tien shan fault northern tien shan suture accreted the northern side of the central tien shan to an island arc which lay to its north the north tien shan arc this collision is bracketed by the middle carboniferous termination of arc magmatism and the appearance of late carboniferous or early permian elastics in a foreland basin developed over the extinct arc thrust sheets generated by the collision are proposed as the tectonic load responsible for the subsidence of this basin post collisional but palaeozoic dextral shear occurred along the northern suture zone this was accompanied by the intrusion of basic and acidic magmas in the central tien shan late palaeozoic basic igneous rocks from all three lithospheric blocks represented in the tien shan possess chemical characteristics associated with generation in supra subduction zone environments even though many post date one or both collisions rocks from each block also possess distinctive trace element chemistries which supports the three fold structural division of the orogenic belt it is unclear whether the chemical differences represent different source characteristics or are due to different episodes of magmatism being juxtaposed by later dextral strike slip fault motions because the southern collision zone in the tien shan is the older of the two the tarim block sensu stricto collided not with the eurasian landmass but with a continental block which was itself separated from eurasia by at least one ocean the destruction of this ocean in late carboniferous early permian times represented the final elimination of all oceanic basins from this part of central asia

turbulence burst over four micro topographies in the wind tunnel abstract investigating the mechanisms of wind sand movement is essential to deeply understand sand storm and desertification process and further to control the wind sand hazards it is considered that turbulence burst may have great influence on the motion of sand particles but current theoretical and experimental studies mostly concentrate on the turbulence burst over flat surface or in the water sand dunes and sand ripples are basic forms of desert landscape and the slope gradient will inevitably affect the frequency of turbulence burst in this paper instantaneous velocities over 4 different sand surfaces including smooth flat bed flat sand bed sand bed with ripples and slope bed are measured using one dimensional hot wire detector the results show that for the slope sand surface wind field in leeward slope region is a buffering zone which doesn t obey logarithmic function on the flat sand surface the distribution of turbulence intensity and reynolds normal stress are gradually decreasing along the height of boundary layer on the slope sand surface the stronger turbulence behavior happens near the top of slope based on mu level method analysis it is found that the turbulence bursts on both flat sand surface and sand ripples mainly occur near the surface and gradually decrease with the height compared to flat sand surface the burst frequency is 30 50 higher on the sand ripples surface which indicates that micro topography have an influence on the turbulence burst this work may be helpful in understanding the initiation and transportation of sand storm as well as the desertification process

formation of positive end t granitoids from the alataw mountains xinjiang china by mixing and fractional crystallization implication for phanerozoic crustal growth abstract syn collisional granitic plutons intruded into devonian and carboniferous sedimentary and volcanic rocks along the southern slope of the alataw mountains in the north tianshan fold belt these intrusions are 307 290 ma in age granitoids in the eastern part of the mountain show characteristics similar to i type affinity while those in the western part show s type affinity carboniferous volcanic rocks andesite to rhyolite cover the eastern part of the region they share many common geochemical characteristics with the eastern granitoids intermediate and acid igneous rocks show positive e nd t values ranging from 7 to about 0 and initial sr isotopic ratios of 0 702 0 711 carboniferous basalts exposed in the region give 87 sr 86 sr t 0 701 0 704 and e nd t 7 12 country rock and basement gneisses show 87 sr 86 sr t 0 707 0 715 and e nd t 5 to 8 the positive e nd t suggests that mantle derived material play an important role in petrogenesis of the alataw granitoids a common mantle derived component is much likely to be involved in the petrogenesis of the granites from northern xinjiang since the positive e nd t granites with early paleozoic ages are widespread in the entire central asia mongolia granitic belt our data provide a constraint on the sr and nd isotopic ratios of this mantle derived mafic component which may be similar to those of the carboniferous basalts but can also have lower e nd t of 3 7 positive e nd t values suggest large mantle input representing a contribution of mantle derived materials to the continental crust it is very likely that this event of continental growth took place in very late proterozoic or early paleozoic

geochemical and geochronological studies of granitoid rocks from the western tianshan orogen implications for continental growth in the southwestern central asian orogenic belt abstract the western tianshan orogen in northwestern china is part of the southwestern margin of the central asian orogenic belt caob which represents the largest tectonic assembly of accretionary complexes and the most significant area of phanerozoic continental growth in the world granitoid rocks have a widespread occurrence and occupy about 30 of the whole exposure of the orogen ages obtained for the granitoids vary from 896 ma to 247 ma while initial 87 sr 86 sr ratios vary from 0 70329 to 0 72070 and e nd values from 14 1 to 7 3 the occurrence of neoproterozoic granitic gneisses implies the presence of precambrian basement in this area during oceanic subduction continental growth occurred as a result of several combined processes i e by addition of oceanic crustal melts adakites the intrusion of basaltic magmas derived by partial melting of the metasomatized depleted mantle wedge and the upwelling of granitic magma derived from a mixed source of basaltic magmas and old continental basement however during the post collisional period vertical accretion of underplated juvenile mantle material may have been accomplished during slab breakoff delamination this study suggests a two stage model of continental growth of syn subduction lateral accretion of arc complexes and post collisional vertical accretion of underplated mantle material which may also be relevant for the western segment of the caob in the phanerozoic the reworking and involvement of old crust are more obvious in the western tianshan orogen compared to other parts of the caob comprising the western junggar eastern junggar alataw and altay terranes

tectonic evolution of the south tianshan orogen and adjacent regions nw china geochemical and age constraints of granitoid rocks geochemical and geochronological evidence was obtained from granitoids of the south tianshan orogen and adjacent regions which consist of three individual tectonic domains the kazakhstan yili plate the central tianshan terrane and the tarim plate from north to south the central tianshan terrane is structurally bounded by the early paleozoic nikolaev line north nalati fault and late paleozoic atbashy inyl chek south nalati qawabulak fault zones against the kazakhstan yili and tarim plates respectively the meta aluminous to weakly peraluminous granitic rocks which are exposed along the kekesu river and the bikai river across the central tianshan terrane have a tholeiitic calc alkaline or high potassium calc alkaline composition i type geochemical trace element characteristics and the y versus rb nb or y versus nb discrimination diagrams favor a continental arc setting for these granitoid rocks shrimp u pb and la icp ms u pb zircon age data indicate that the magmatism started at about 480 ma continued from 460 to 330 ma and ended at about 275 ma the earlier magmatism 470 ma is considered to be the result of a simultaneous southward and northward subduction of the terskey ocean beneath the northern margin of the tarim plate and the kazakhstan yili plate respectively the later magmatism 460 330 ma is related to the northward subduction of the south tianshan ocean beneath the southern margin of the kazakhstan yili central tianshan plate the dataset presented here in conjunction with previously published data support a late paleozoic tectonic evolution of the south tianshan orogen not a triassic one as recently suggested by shrimp u pb zircon dating for eclogites

middle cambrian to permian subduction related accretionary orogenesis of northern xinjiang nw china implications for the tectonic evolution of central asia abstract middle cambrian to permian subduction related records are widely distributed in northern xinjiang which can be grouped into the chinese altay east junggar eastern tien shan west junggar yili and tarim domains by integrating paleogeographic and geological data we suppose that the chinese altay east junggar eastern tien shan domain was more closely located to siberia while the west junggar and yili domains occupied an intermediate position near the kazakhstan block in the early paleozoic paleoasian ocean distribution of andean type magmatic arcs island arcs accretionary wedges ophiolitic slices and or microcontinents shows an archipelago paleogeography forming a huge accretionary active margin sequences the tarim domain was on the opposite side of the early paleozoic paleoasian ocean remaining passive margin these tectonic units drifted northwards and approached the southern active margin of the siberian craton in the late paleozoic leading to termination of the paleoasian ocean and formation of a complicated orogenic collage between siberian craton and the tarim block between the end permian and triassic these multiple accretion processes significantly contributed to the lateral growth of central asia

wind forces and related saltation transport the effect of several wind characteristics on sand transport was studied in three experiments in north burkina faso west africa the first experiment is used to analyse the relation between wind speed and shear stress fluctuations across height the second experiment is used to study the relation of these wind characteristics with saltation transport for fourteen convective storms registered during the rainy seasons of 2002 and 2003 the effect of sampling time is studied for two of these convective storms the third experiment relates the turbulent structures of four convective storms to saltation transport wind speed measurements were undertaken with two sonic anemometers and sediment transport was measured by two saltiphones the sampling frequency was either 8 or 16 hz the sonic frame of reference was rotated according to a triple rotation horizontal fluctuations showed a fairly good correlation with height because the wind speed at both sensors was affected by the same vortices the correlation coefficients ranged from 0 42 when the distance between the sensors was 1 75 m to 0 92 when the distance was 0 25 m the instantaneous reynolds stress had the weakest correlation correlation coefficient of 0 05 at 1 75 m between the sensors and 0 56 at 0 25 m between the sensors because the momentum at 2 m above the soil surface is transported by different eddies than those close to the ground this also explains the fairly good correlation coefficients between the horizontal components of the wind and saltation compared to the poor correlations between instantaneous reynolds stress and saltation an increase in sampling time did not have much impact on these correlation coefficients up to sampling periods of about 30 s however this sampling interval would be too coarse to describe the vertical wind component adequately the classification of the moments of shear stress into the turbulent structures sweeps ejections inward and outward interactions showed that the mean saltation flux is higher at sweeps and outward interactions than at ejections and inward interactions also saltation occurred more often during sweeps and outward interactions than during ejections and inward interactions

reconciling fluid inclusion types fluid processes and fluid sources in skarns an example from the bismark deposit mexico the bismark deposit 8 5 mt at 8 zn 0 5 pb 0 2 cu and 50 g t ag located in northern mexico is an example of a stock contact skarn end member of a continuum of deposit types collectively called high temperature carbonate replacement deposits the deposit is hosted by massive sulfide within altered limestone adjacent to the bismark quartz monzonite stock 42 ma and the bismark fault alteration concurrently developed in both the intrusion and limestone the former contains early potassic alteration comprising k feldspar and biotite which was overprinted by kaolinite rich veins and alteration and later quartz sericite and pyrite with minor sphalerite and chalcopyrite prograde exoskarn alteration in the limestone consists of green andradite and diopside and transitional skarn comprising red brown andradite green hedenbergite and minor vesuvinite calcite fluorite and quartz the main ore stage post dates calc silicate minerals and comprises sphalerite and galena with gangue pyrite pyrrhotite calcite fluorite and quartz the entire hydrothermal system developed synchronously with faulting fluid inclusion studies reveal several distinct temporal compositional and thermal populations in pre syn and post ore quartz fluorite and calcite the earliest primary fluid inclusions are coexisting vapor rich type 2a and halite bearing type 3a type 3b contain sylvite brine inclusions 32 to 60 total wt salts that occur in pre ore fluorite trapping temperatures are estimated to have been in excess of 400 c under lithostatic pressures of 450 bar 1 5 km depth primary fluid inclusions trapped in syn ore quartz display critical to near critical behavior type 1c have moderate salinity 8 4 to 10 9 wt nacl equiv and homogenization temperatures th ranging from 351 to 438 c liquid rich type 1a and 1b calcite bearing inclusions occur as primary to secondary inclusions predominantly in fluorite and show a range in th 104 336 c and salinity 2 7 11 8 wt nacl equiv which at the higher th and salinity ranges overlap with type 1c inclusions oxygen isotope analysis was carried out on garnet quartz and calcite plus carbon isotopes in pre syn post ore and peripheral veins pre ore skarn related garnets have a 18omineral range between 3 9 and 8 4 quartz from the main ore stage range between 13 6 and 16 0 calcite from the main ore stage has 13c values of 2 9 to 5 1 and 18o values of 12 3 to 14 1 which are clearly distinct from post ore veins and peripheral prospects that have much higher 18o 16 6 27 3 and 13c 1 3 3 1 values despite the numerous fluid inclusion types only two fluid sources can be inferred namely a magmatic fluid and an external fluid that equilibrated with limestone furthermore isotopic data does not indicate any significant mixing between the two fluids although fluid inclusion data may be interpreted otherwise thus the various fluid types were likely to have formed from varying pressure temperature conditions through faulting during exsolution of magmatic fluids late stage hydrothermal fluid activity was dominated by the non magmatic fluids and was post ore

magmatic dominated fluid evolution in the jurassic nambija gold skarn deposits southeastern ecuador the jurassic approximately 145 ma nambija oxidized gold skarns are hosted by the triassic volcanosedimentary piuntza unit in the sub andean zone of southeastern ecuador the skarns consist dominantly of granditic garnet ad20 98 with subordinate pyroxene di46 92hd17 42jo0 19 and epidote and are spatially associated with porphyritic quartz diorite to granodiorite intrusions endoskarn is developed at the intrusion margins and grades inwards into a potassic alteration zone exoskarn has an outer k and na enriched zone in the volcanosedimentary unit gold mineralization is associated with the weakly developed retrograde alteration of the exoskarn and occurs mainly in sulfide poor vugs and milky quartz veins and veinlets in association with hematite fluid inclusion data for the main part of the prograde stage indicate the coexistence of high temperature 500 c to 600 c high salinity up to 65 wt eq nacl and moderate to low salinity aqueous carbonic fluids interpreted to have been trapped at pressures around 100 120 mpa corresponding to about 4 km depth lower temperature 510 300 c and moderate to low salinity 23 2 wt eq nacl aqueous fluids are recorded in garnet and epidote of the end of the prograde stage the microthermometric data th from 513 c to 318 c and salinity from 1 0 to 23 wt eq nacl and 18o values between 6 2 and 11 5 for gold bearing milky quartz from the retrograde stage suggest that the ore forming fluid was dominantly magmatic pressures during the early retrograde stage were in the range of 50 100 mpa in line with the evidence for co2 effervescence and probable local boiling the dominance of magmatic low saline to moderately saline oxidizing fluids during the retrograde stage is consistent with the depth of the skarn system which could have delayed the ingression of external fluids until relatively low temperatures were reached the resulting low water to rock ratios explain the weak retrograde alteration and the compositional variability of chlorite essentially controlled by host rock compositions gold was precipitated at this stage as a result of cooling and ph increase related to co2 effervescence which both result in destabilization of gold bearing chloride complexes significant ingression of external fluids took place after gold deposition only as recorded by 18o values of 0 4 to 6 2 for fluids depositing quartz below 350 c in sulfide rich barren veins low temperature 300 c meteoric fluids 18owater between 10 0 and 2 0 are responsible for the precipitation of late comb quartz and calcite in cavities and veins and indicate mixing with cooler fluids of higher salinities about 100 c and 25 wt eq nacl the latter are similar to low temperature fluids 202 74 5 c with 18o values of 0 5 to 3 1 and salinities in the range of 21 1 to 17 3 wt eq cacl2 trapped in calcite of late veins and interpreted as basinal brines nambija represents a deep equivalent of the oxidized gold skarn class the presence of co2 in the fluids being partly a consequence of the relatively deep setting at about 4 km depth as in other au bearing skarn deposits not only the prograde stage but also the gold precipitating retrograde stage is dominated by fluids of magmatic origin

age geochemistry and tectonic implications of a late paleozoic stitching pluton in the north tian shan suture zone western china the central asian orogenic belt is the largest tectonic assembly of continental and oceanic terranes on earth due to closure of the paleo asian ocean in the phanerozoic among major suture zones in the north xinjiang region of western china the north tian shan suture zone because of collision between the yili terrane in the south and the junggar terrane in the north contains the youngest ophiolitic rocks and may represent the terminal stage of development of the central asian orogenic belt in western china but the timing of the suture zone remains poorly constrained a sensitive high resolution ion microprobe shrimp zircon u pb age of 316 3 ma i e the beginning of the late carboniferous from the undeformed sikeshu pluton which crosscuts the suture zone places a crucial upperage bound for the time of collision between the yili and junggar terranes this event occurred later than or nearly concurrent with other accretion collision events in the north xinjiang region implying that fi nal terrane amalgamation was completed in the late carboniferous the sikeshu pluton shares geochemical characteristics of the widespread late carboniferous to permian postcollisional a type and i type granitoids with depleted mantle like sr nd isotopic signatures in the north xinjiang region they all occurred during a protracted ca 320 270 ma episode of postcollisional magmatism that may have been induced by basaltic under plating due to either slab breakoff or delamination of thickened mantle lithosphere beneath the central asian orogenic belt the same postcollisional magmatism also generated cu ni sulfi de bearing mafi c ultramafi c magmatic complexes adakites and porphyry type coppermolybdenum bearing magmatic rocks in the north xinjiang region

fluid evolution in the formation of the fenghuangshan cu fe au deposit tongling anhui china the fenghuangshan cu fe au deposit is located in tongling anhui province in central east china within the middle lower yangtze river polymetallic belt the mineralization is related to late yanshanian magmatic intrusions emplaced in lower triassic limestones and is divided into two episodes the first and more important episode a is related to granodiorite granodiorite porphyry and characterized by massive disseminated veinlet and breccia style mineralization in skarn formed at the contact zone whereas the second episode b is related to a quartz monzodiorite porphyry stock which crosscuts the previous skarn and is characterized by disseminated and veinlet style mineralization within the porphyry based on mineral assemblages and their crosscutting relationships the hydrothermal evolution of episode a is further divided into five substages a1 a5 and that of episode b into four b1 b4 among which a4 a5 and b3 are the main copper mineralization stages this paper focuses on microthermometric studies of fluid inclusions in the various stages with an aim to characterize the thermal and compositional evolution of hydrothermal fluids and to discuss their implications for mineralization in terms of fluid sources and metal deposition mechanisms fluid inclusions were studied in garnet quartz and calcite from stages a1 a4 a5 b1 b2 b3 and b4 four types and 13 subtypes of fluid inclusions were distinguished based on fluid composition and phase assemblages type i fluid inclusions contain one or more salt daughter minerals halite and sylvite and homogenize into the liquid phase whereas type ii inclusions homogenize into the vapor phase both commonly containing an opaque daughter mineral type iii fluid inclusions are aqueous inclusions that do not contain daughter minerals and homogenize into the liquid phase and type iv inclusions are co2 bearing homogenize to the co2 or the aqueous phase and commonly contain an opaque daughter mineral primary fluid inclusions in stage a1 are of type i and ii interpreted to represent two immiscible phases resulting from boiling and those in stages a4 and a5 are of type iii stages b1 and b2 are characterized by type i primary inclusions and stages b3 and b4 by type iii type iv inclusions occur as secondary inclusions in b1 quartz and are interpreted to be related locally to b3 stage mineralization microthermometric data indicate a trend of decreasing temperatures and salinities from early to late stages for both mineralization episodes reflecting a change from a magmatic fluid dominated system to one invaded by fluids from the country rocks and meteoric water the fact that the main stages of mineralization a4 a5 b3 coincided with the development of fluid inclusions without daughter minerals of salt suggests that sulfide precipitation did not take place until the system was diluted by cooler fluids with lower salinities however the observation that the fluid inclusions hosted in minerals before sulfide mineralization i e stages a1 b1 and b2 commonly contain opaque daughter minerals inferred to be sulfides suggests that the ore forming components were likely derived from the higher temperature magmatic fluids and the fluids derived from the country rocks mainly contributed to the precipitation of sulfides through mixing and cooling

geology geochemistry and genesis of axi a paleozoic low sulfidation type epithermal gold deposit in xinjiang china abstract axi is a low sulfidation type epithermal gold deposit hosted in paleozoic subaerial volcanic rocks in the western tianshan orogenic belt xinjiang china the resource is more than 50 t gold at an average grade of 4 4 ppm the deposit occurs in the tulasu volcanic fault basin in the paleozoic active continental margin on the northern side of the yili central tianshan plate the host rocks are andesitic volcaniclastic rocks of the paleozoic dahalajunshan formation and the orebodies occur as veins in annular faults of a paleocaldera mineralization at axi can be subdivided into five stages quartz and or chalcedony vein quartz vein quartz carbonate vein sulfide vein and carbonate vein there are two types of ore host quartz vein and altered rocks ore minerals are native gold electrum pyrite marcasite arsenopyrite hematite limonite and trace amounts of pyrargyrite polybasite naumannite cerargyrite sphalerite chalcopyrite tetrahedrite galena pyrrhotite and clausthalite gangue minerals are mainly quartz chalcedony illite calcite siderite dolomite adularia and laumontite the main wall rock alteration is silicification and phyllic alteration carbonatization and propylitization the deposit is characterized by an enrichment relative to crustal abundance of au ag as sb bi hg se te and mo depletion in base metals cu pb and zn and a low ag au ratio 0 5 3 7 three types of fluid inclusions were recognized in quartz from the major mineralization stages liquid aqueous inclusions liquid rich two phase inclusions and small amounts of vapor rich two phase inclusions microthermometric measurements indicate that the final ice melting temperatures are 0 3 to 4 4 c corresponding to salinities of 0 5 6 9 wt nacl equiv 2 2 wt nacl equiv in average the peak temperatures of ice melting varies from 0 4 to 1 9 c corresponding to salinities of 0 7 3 1 wt nacl equiv homogenization temperatures range mainly between 120 and 240 c with an average of 190 c and a maximum of 335 c the fluid density is 0 73 to 0 95 g cm 3 and thus the estimated maximum mineralization depth is about 700 m hydrogen and oxygen isotopic compositions of the ore fluids lie within a narrow range d h2o is 98 to 116 and 18 o h2o 1 8 to 0 4 3 he 4 he ranges from 0 0218 to 0 138 ra with an average of 0 044 ra indicating that he derived predominantly from crust with negligible mantle he in the ore fluids by contrast the 40 ar 36 ar ranges from 317 7 to 866 0 suggesting that crust derived radioactive 40 ar accounts for 7 0 to 66 and atmospheric 40 ar about 43 to 93 in the ore fluids hydrogen oxygen carbon sulfur and noble gas isotopes indicate that the ore forming fluids of the axi gold deposit consisted predominantly of circulating meteoric water ore forming metals may have derived mainly from the host volcaniclastic rocks of the dahalajunshan formation and basement rocks the occurrence of adularia platy calcite and quartz or sulfide aggregates as pseudomorphs after bladed calcite in ore veins and occurrence of aqueous liquid and liquid rich and vapor rich two phase inclusions indicates that boiling of the ore forming fluid have occurred leading to supersaturation of the hydrothermal solution and deposition of ore metals this is the main mineralization mechanism for quartz vein type ores in axi the ore forming fluid was buffered to a near neutral ph in a reduced environment during mineralization the preservation of this paleozoic axi deposit and its discovery required a rapid accumulation of sediments in the basin after formation of the deposit and minimal amount of erosion after late cenozoic uplift

formation of anhydrous and hydrous skarn in cu au ore deposits by magmatic fluids most skarn ore deposits are characterized by two distinctly different alteration styles an early prograde stage with anhydrous minerals such as garnet and pyroxene forms from relatively high temperature hypersaline liquid a later retrograde stage with hydrous minerals such as epidote amphibole and chlorite plus sulfide ore minerals forms from lower temperature lower salinity fluids these two alteration stages commonly have been thought to reflect a dominance of magmatic and meteoric water respectively with relevance to the source of ore metals we report data from two different skarn systems one being part of the world s largest cu au resource stable isotope compositions of anhydrous and hydrous alteration minerals from both deposits indicate a magmatic source for both the prograde and retrograde stages 18o averages 5 0 per mil for garnet range 3 4 7 2 6 5 per mil for pyroxene 4 3 8 2 and 7 1 per mil for amphibole 4 3 8 7 the d values of late amphibole are more complex with magmatic values 77 to 78 for one deposit and both magmatic and lighter values for another deposit that could be explained either by magmatic degassing or by limited mixing with meteoric water we conclude that the differences in fluid composition prograde versus retrograde stages resulted from a magmatic fluid that intersected its solvus during the early stage creating vapor and hypersaline liquid whereas in the later stage this magmatic fluid did not intersect its solvus because it followed a different cooling path this late low salinity liquid only boiled once its vapor pressure curve was reached causing sulfide ore to precipitate during the retrograde stage

paleozoic early mesozoic gold deposits of the xinjiang autonomous region northwestern china the late paleozoic early mesozoic tectonic evolution of xinjiang autonomous region northwestern china provided a favorable geological setting for the formation of lode gold deposits along the sutures between a number of the major eastern asia cratonic blocks these sutures are now represented by the altay shan tian shan and kunlun shan ranges with the former two separated by the junggar basin and the latter two by the immense tarim basin in northernmost xinjiang final growth of the altaid orogen southward from the angara craton is now recorded in the remote mid to late paleozoic altay shan accreted early to middle devonian oceanic rock sequences contain typically small precious metal bearing fe cu zn vms deposits e g ashele orogenic gold deposits are widespread along the major irtysh e g duyolanasayi saidi taerde kabenbulake akexike shaerbulake and tuergen hongshanzui e g hongshanzui fault systems as well as in structurally displaced terrane slivers of the western junggar e g hatu and eastern junggar areas geological and geochronological constraints indicate a generally late carboniferous to early permian episode of gold deposition which was coeval with the final stages of altaid magmatism and large scale right lateral translation along older terrane bounding faults the tian shan an exceptionally gold rich mountain range to the west in the central asian republics is only beginning to be recognized for its gold potential in xinjiang in this easternmost part to the range northerly and southerly directed subduction accretion of early to mid paleozoic and mid to late paleozoic oceanic terranes respectively to the precambrian yili block central tian shan was associated with 400 to 250 ma arc magmatism and carboniferous through early permian gold forming hydrothermal events the more significant resulting deposits in the terranes of the southern tian shan include the sawayaerdun orogenic deposit along the kyrgyzstan border and the epithermal and replacement deposits of the kanggurtag belt to the east in the chol tagh range gold deposits of approximately the same age in the yili block include the axi hot springs epithermal deposit near the kazakhstan border and a series of small orogenic gold deposits south of urumqi e g wangfeng gold rich porphyry copper deposits e g tuwu define important new exploration targets in the northern tian shan of xinjiang the northern foothills of the kunlun shan of southern xinjiang host scattered small placer gold deposits sources for the gold have not been identified but are hypothesized to be orogenic gold veins beneath the icefields to the south they are predicted to have formed in the tianshuihai terrane during its early mesozoic accretion to the amalgamated tarim qaidam kunlun cratonic block

paleozoic tectonic evolution of the tianshan orogen northwestern china abstract the chinese tianshan orogenic belt which extends west east for about 1500 km is one of the most important paleozoic orogenic belts in central asia it includes parts of the tarim yili central tianshan and junggar plates which are microcontinental blocks with precambrian basements and meso cenozoic depositional covers the tarim plate is separated from the yili central tianshan plate by the southern central tianshan suture early carboniferous ophiolitic melanges and blueschists are widespread in this suture and are believed to be produced by the collision between a passive continental margin on the north side of the tarim plate and an active continental margin on the south side of the yili central tianshan plate the collision occurred at the end of early carboniferous the yili central tianshan and the junggar plates are separated by the northern central tianshan suture also considered as an early carboniferous collisional zone along which the middle ordovician ophiolitic melanges blueschists and late devonian early carboniferous ophiolites are exposed in early paleozoic times the subduction of the paleo junggar ocean took place in an active margin on the north side of the yili central tianshan plate along the northern central tianshan suture at the end of early carboniferous the north side of the yili central tianshan plate collided with the north tianshan arc along this suture the paleo oceanic crust in the tianshan and adjacent region was entirely consumed at the end of early carboniferous meanwhile the tarim yili central tianshan and junggar plates were accreted to eurasia epicontinental sediments were then deposited throughout the tianshan region during the middle late carboniferous times in the early permian tianshan began to uplift with accompanying volcanic eruption and granitic intrusion the uplift was accelerated in the late permian and continental molasse was extensively deposited

direct evolution of brine from a crystallizing silicic melt at the questa new mexico molybdenum deposit molybdenum mineralization in the southwest orebody at the questa deposit is associated with crystallization of aplite porphyry explosive brecciation and exsolution of magmatic hydrothermal fluids quartz k feldspar fluorophlogopite and molybdenite precipitated from exsolving aqueous fluids and cemented aplite porphyry and andesite wall rock clasts forming a magmatic hydrothermal breccia ore fluid inclusions in quartz in the breccia matrix trapped aqueous fluids that transported and precipitated molybdenum two fluid inclusion populations associated with molybdenite mineralization were identified the largest population commonly contains liquid vapor halite sylvite and one or more opaque daughter crystals these inclusions homogenize between 200 degrees and 500 degrees c and have a prominent mode at 360 degrees to 400 degrees c salinities vary from 31 to 57 wt percent nacl equiv low first ice melting temperatures suggest that additional fluid components possibly calcium or magnesium chlorides may be present approximately 80 percent of these inclusions homogenize by halite dissolution phase equilibria constraints require that these inclusions trapped fluids in the vapor absent field the remaining saline inclusions homogenize to liquid at temperatures above halite dissolution temperatures significantly the saline fluid did not coexist with a low density aqueous fluid a second population of inclusions contains fluids with salinities of 2 7 to 25 0 wt percent nacl equiv and homogenizes by vapor bubble disappearance vapor bubble expansion or critical behavior textural relationships and phase behavior during microthermometry indicate that these inclusions constitute a single population which formed as pressure and temperature fluctuated at near critical conditions pressure changes related to brecciation followed by crystallization and system resealing produced the observed fluids saline fluids were trapped as the system sealed following a major brecciation event these high salinity fluids were produced as the melt under pressure that increased from hydrostatic to lithostatic partitioned increasing amounts of chlorine into the exsolving aqueous fluid renewed fracturing and abrupt pressure decrease to hydrostatic conditions reduced the mass of chlorine partitioning to the exsolving fluid lower salinity fluids exsolved at near critical conditions and were trapped by inclusions that homogenize to liquid to vapor or by critical behavior the lack of cogenetic liquid and vapor rich fluid inclusions and phase equilibria constraints indicate that high salinity fluids or 57 wt nacl equiv were generated directly by the crystallizing magma and were not a product of aqueous fluid immiscibility

volatile exsolution at the dinkidi cu au porphyry deposit philippines a melt inclusion record of the initial ore forming process immiscible phases derived from degassing silicate magmas are considered to be precursors of metal bearing hydrothermal fluids in porphyry deposits the development of melt inclusion techniques provides a window into this critical period of porphyry formation when the cooling decompression and crystallization of silicate melts result in the formation of immiscible phases the record of magmatic to hydrothermal evolution is presented using inclusions in clinopyroxene phenocrysts from the syenitic balut dike one of the host rock lithologies for mineralization at the dinkidi cu au porphyry deposit philippines primary inclusions include silicate glass multiphase aggregates comprising salts silicates sulfates carbonates sulfides and oxides and highly saline aqueous fluids various analyses including in situ laser ablation inductively coupled plasma mass spectrometry of the multiphase inclusions determined elevated concentrations of cl s as tl k na and a number of metals including those that form ore grade deposits e g cu and those that do not e g mo pb zn and w at the dinkidi porphyry deposit silicate melt and multiphase salt rich inclusions in clinopyroxene are interpreted as having originally formed as immiscible phases at magmatic temperatures

sr nd elements and isotopes as tracers of dust input in a tropical soil chronosequence abstract although hainan island is located in one of the relative least dusty regions in china asian dust has been identified in hainan soils we used sr and nd isotopes of soils saprolite bedrocks and asian dust to not only identify long range transported dust but also quantify the dust contribution to hainan soils sr and nd isotopic compositions of the soils are clearly affected by dust deposition the soils in near surface horizons have 87 sr 86 sr values as high as 0 7193 that are more radiogenic than the basalts indicating involvement of asian dust whereas deep horizons show a dominantly basaltic signature 87 sr 86 sr 0 7038 the e nd 0 values for hainan soils range from 6 46 to 1 85 the higher value closely approximates the values measured for the hainan lava and the lower value indicates the fingerprint of the asian dust the 87 sr 86 sr and e nd 0 values for soils also show a progressive trend with time which implies that dust accumulates with soil age we calculated the dust accretion rates for sr based and nd based to quantify the dust contributions to soils the estimate of dust accreted shows an approximate increasing trend with the ages of soils for sr based and nd based methods the soils in the old sites are likely to have undergone long term dust input and accumulated high dust levels we also find excellent agreement in the amount of dust present and dust accretion rates based on the two tracers at the 300 ka site and the 1120 ka site respectively besides lower dust deposition in the pliocene epoch than the late quaternary over eastern eurasian the loss of mineralogical and geochemical tracers over million year time scales also may lead to underestimates of time averaged dust deposition rates in the old sites therefore the young sites 180 ka and 300 ka should provide more realistic estimates of average dust accretion rates the importance of dust in the tropical hainan soil chronosequence highlights the significance of dust accretion to soils globally

the empire cu zn mine idaho exploration implications of unusual skarn features related to high fluorine activity the empire cu zn skarn deposit is unusual because of the proximal position of zn mineralization abundance of endoskarn and the extremely vermicular texture of quartz phenocrysts in the related intrusive rocks cu zn skarn occurs at the contact between upper mississippian white knob limestone and the granite porphyry phase of the mackay stock which consists from early to late of quartz monzodiorite granophyre granite porphyry porphyritic granite and many dikes the late phases have high f and also extremely vermicular quartz phenocrysts endoskarn is more abundant than exoskarn the earliest alteration of the intrusive rocks consists of disseminated diopsidic pyroxene di64hd36 to di88hd12 actinolite and titanite this assemblage was cut by early scapolite me18 to me35 mostly me18 26 and or green pyroxene di14hd80 to di20hd77 veinlets with or without wollastonite halos these early veins were then cut by main stage endoskarn veins that typically have a garnet minor pyroxene inner zone a wollastonite and or pyroxene ca rich plagioclase an56 to an89 envelope and a halo containing disseminated fine grained alteration minerals of the same assemblage as the envelope some veins contain only the envelope assemblage and are interpreted to represent the alteration front the inner zone locally contains vesuvianite where many veins intersect endoskarn is massive pyroxene is zoned around fluid conduits the distal pyroxene is fe rich hedenbergitic whereas the proximal pyroxene is fe poor diopsidic the garnet changes in the opposite way being fe poor al rich grossularitic in locations distal to the fluid conduits and fe rich andraditic in proximal locations in contrast in the exoskarn all pyroxene is diopsidic and garnet is andraditic weak retrograde alteration composed of quartz calcite chlorite with minor fluorite talc and epidote overprinted both endoskarn and exoskarn magnetite precipitated after garnet pyroxene in both endoskarn and exoskarn sphalerite precipitated together with chalcopyrite in proximal locations and is associated with retrograde alteration other ore minerals include minor molybdenite bornite pyrite galena arsenopyrite native au as well as supergene minerals such as chrysocolla malachite azurite native cu and limonite fluid xenoliths from pyroxene in early endoskarn veinlets homogenize at 600 c massive endoskarn and exoskarn replacing limestone inclusions in granite porphyry formed at 500 to 700 c whereas the highest temperature inclusions 700 c occur in narrow garnet minor pyroxene veins fluid inclusions in exoskarn replacing wall rock have homogenization temperatures of 500 to 650 c retrograde alteration and cu zn mineralization occurred at 250 to 300 c fluid inclusions in prograde minerals contain daughter minerals whereas fluid inclusions in retrograde minerals do not indicating a decrease in salinity with time late stage fluids have low eutectic temperatures indicating the possible presence of kcl nacl fecl2 cacl2 mgcl2 k2co3 and or na2co3 formation of the unusually abundant endoskarn the proximal position of zn mineralization and the extremely vermicular texture of quartz phenocrysts are all believed to have been promoted by the high f content of the magmatic fluid these features may serve as exploration indicators of associated high f mineralization such as buried porphyry mo deposits

macflincor and its application to fluids in archean lode gold deposits abstract macflincor was developed to process laboratory data gathered on fluid inclusions and to calculate isochores for geologically important fluids composed of h2o c02 ch4 nacl and n2 within the program interactive diagrams are available to describe those chemical systems which cannot be adequately constrained numerically the user can choose from various published equations of state describing fluid behavior and can easily compare the results obtained by using different equations the program once the basic fluid parameters have been established allows the data to be used to determine the p t trapping conditions to evaluate possible pressure corrections and to compare different depths of formation based on the pressure calculations and given geothermal gradients for illustrative purposes macflincor has been utilized here to constrain different physical chemical parameters of fluid inclusions trapped in ore related quartz veins and breccias of archean lode gold deposits in western australia inferred pressures from individual deposits show a wide range of values which may be due to post entrapment modifications and or observational uncertainties including estimation of liquid vapor ratios

geochronology and fluid inclusion study of the yinjiagou porphyry skarn mo cu pyrite deposit in the east qinling orogenic belt china abstract the yinjiagou mo cu pyrite deposit of henan province is located in the huaxiong block on the southern margin of the north china craton it differs from other mo deposits in the east qingling area because of its large pyrite resource and complex associated elements the deposit s mineralization process can be divided into skarn sulfide and supergene episodes with five stages marking formation of magnetite in the skarn episode quartz molybdenite quartz calcite pyrite chalcopyrite bornite sphalerite and calcite galena sphalerite in the sulfide episode and chalcedony limonite in the supergene episode re os and 40 ar 39 ar dating indicates that both the skarn type and porphyry type orebodies of the yinjiagou deposit formed approximately 143 ma ago during the early cretaceous four types of fluid inclusions fis have been distinguished in quartz phenocryst various quartz veins and calcite vein based on petrographic observations and microthermometric criteria the fis include liquid rich gas rich h 2 o co 2 and daughter mineral bearing inclusions the homogenization temperature of fis in quartz phenocrysts of k feldspar granite porphyry ranges from 341 c to 550 c and the salinity is 0 4 44 0 wt nacl eqv the homogenization temperature of fis in quartz molybdenite veins is 382 416 c and the salinity is 3 6 40 8 wt nacl eqv the homogenization temperature of fis in quartz calcite pyrite chalcopyrite bornite sphalerite ranges from 318 c to 436 c and the salinity is 5 6 42 4 wt nacl eqv the homogenization temperature of fis in quartz molybdenite stockworks is in a range of 321 411 c and the salinity is 6 3 16 4 wt nacl eqv the homogenization temperature of fis in quartz sericite pyrite is in a range of 326 419 c and the salinity is 4 7 49 4 wt nacl eqv the ore forming fluids of the yinjiagou deposit are mainly high temperature high salinity fluids generally with affinities to an h 2 o nacl kcl co 2 system the 18 o h2o values of ore forming hydrothermal fluids are 4 0 8 6 and the d v smow values are between 64 and 52 indicating that the ore forming fluids were primarily magmatic the 34 s v cdt values of sulfides range between 0 2 and 6 3 with a mean of 1 6 sharing similar features with deeply sourced sulfur implying that the sulfur mainly came from the lower crust composed of poorly differentiated igneous materials but part of the heavy sulfur came from the guandaokou group dolostone the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of sulfides are in the range of 17 331 18 043 15 444 15 575 and 37 783 38 236 respectively which is generally consistent with the pb isotopic signature of the yinjiagou intrusion suggesting that the pb chiefly originated from the felsic intermediate intrusive rocks in the mine area with a small amount of lead from strata the yinjiagou deposit is a porphyry skarn deposit formed during the mesozoic transition of a tectonic regime that is ew trending to nne trending and the multiepisode boiling of ore forming fluids was the primary mechanism for mineral deposition

modeling saltation intermittency 1 in order to investigate the intermittency of the aeolian saltation a saltation model forced with instantaneous velocity fields has been introduced in a large eddy simulation airflow model the coupled model is evaluated on a flat erodible surface under various wind conditions and soil particle size distribution it is first shown that the model is able to simulate a well developed saltation layer in equilibrium with the turbulent flow the main characteristics of the saltation layer and their sensitivity to wind conditions are in good agreement with previous data set then the saltation intermittency is visualized through the presence of blowing sand structures near the surface known as aeolian streamers this is the first time that such structures are reproduced numerically from a correlation analysis we confirm previous thoughts that these sand structures are a visual footprint of past turbulent eddies propagating in the surface boundary layer the streamers appear to be embedded in larger saltation structures with increasing wind conditions the spatial scales of these streamers change with wind conditions and soil particle size distribution this is explained by two mechanisms 1 the modification of eddy structures with the main characteristics of the saltation layer and 2 the reduction of saltating particle sensitivity to the near surface eddies with increasing wind condition and soil median particle diameter as the eddy lifetime decreases within the saltation layer and the particle response time increases respectively the standard deviation of the saltation flux associated to these saltation patterns represents about 10 to 20 of the mean saltation flux

palaeozoic late collisional strike slip deformations in tianshan and altay eastern xinjiang nw china in central asia thrusts and shear zones resulting from palaeozoic accretional events were reworked by e w trending ductile strike slip faults during late palaeozoic early mesozoic time in the tianshan range microstructures and quartz c axis fabrics show a main dextral shearing associated with sinistral localized shear zones the relationship between these conjugate structures indicates a nnw sse trending bulk shortening in the chinese altay mountains the existence of type microstructures in an important sinistral mylonitic zone infers high rates of deformation this shear zone is bordered by a late dextral ductile fault synchronous with a granite emplacement field evidence and datings from the literature provide chronological constraints in the late carboniferous the sinistral mylonitic deformation took place in the erqishi irtysh shear zone in the northeastern part of xinjiang and in kazakhstan during the early permian a regional dextral event occurred in the tianshan range and under the whole of northern xinjiang