the mokrsko west gold deposit bohemian massif czech republic mineralogy deposit setting and classification abstract the mokrsko west deposit is unique among european variscan gold deposits from the points of view of both the structure an approx 200 m thick complex of sheeted several mm thick densely spaced quartz veins and the economic viability gold reserves of about 100 t the deposit is hosted mainly by tonalite of the calc alkaline sazava tonalite suite ca 354 ma of the central bohemian plutonic complex mineralization is characterized by quartz dominated gangue no visible hydrothermal alteration low sulfide content high fineness native gold accompanied by maldonite aurostibite native bismuth and numerous bi te s phases five mineralogical stages are described in great detail arsenopyrite and chlorite thermometers mineral phase stabilities and published isotope and fluid inclusion data are used to reconstruct the temperature and compositional evolution of the system the role of liquid bismuth in the sequestration of gold is also discussed the deposit shares the features of both orogenic gold org and intrusion related gold irg deposits the irg model is advocated by close spatial association between the ore zone and the tonalite host intrusion by the absence scarcity of hydrothermal alteration by the au bi te as elemental association and by marked thermal gradients from the early to late mineralization stages the org model is advocated by an approx 15 10 ma gap between the intrusion of the tonalite host and the ore formation by isotope and geochemical evidence for a key role of metamorphic fluids in the mobilization and transfer of many elements species inclusive s and au the apparently ambiguous classification of the deposit can most probably be attributed to deposit formation at a depth of 9 km and to setting of the deposit at inside a large scale plutonic complex with multiple and prolonged tectonic and intrusive activity

copper lead zinc and cobalt mineralization in the english lake district classification conditions of formation and genesis the copper lead zinc and minor cobalt mineralization of the english lake district has been classified on the basis of mineralogy spatial distribution and geological setting of the veins and age of mineralization the two major types of mineralization are 1 chalcopyrite pyrite arsenopyrite of lower devonian caledonian age and 2 galena sphalerite of early carboniferous age when the former is closely associated with granite intrusions more complex mineral assemblages are found involving tungsten or molybdenum bearing phases also distinguished from these two major types are later assemblages which probably result from their alteration a later upper carboniferous permian baryte mineralization is also present minor graphite and stibnite deposits and the major haematite mineralization found in the area are incorporated into the classification but are not discussed since they have been dealt with by other authors using data from fluid inclusions and experimental data on particular mineral assemblages occurring in the major types of mineralization estimates have been made of the temperatures and compositions of the ore forming fluids the lower devonian veins formed at temperatures in the range of 350 200 c with typical a s 2 values of 10 10 l0 16 atm and a o 2 of 10 25 10 45 atm or even less the solutions were probably brines of low to moderate salinity 5 10 equiv wt nacl the lower carboniferous veins formed at temperatures in the region of 110 130 c from highly saline brines 23 equiv wt nacl theories regarding the origins of the mineralization are also discussed the distribution of lower devonian veins shows a clear relationship to the underlying composite granite batholith the lower carboniferous galena sphalerite veins show no such relationship but tensional tectonic activity in the early carboniferous may have provided a mechanism for the opening of fissures the source of the mineralizing fluids forming the lower devonian veins may have been the borrowdale volcanic group with contributions from fluids associated with the granites which are also likely to have provided a source of heat the high salinities of the fluids producing the lower carboniferous veins suggest that seawater may have been involved in leaching the metals from basement rocks

the influence of debris cover and glacial lakes on the recession of glaciers in sikkim himalaya india we investigated area changes in glaciers covering an area of similar to 200 km 2 in the tista basin sikkim eastern indian himalaya between similar to 1990 and 2010 using landsat thematic mapper tm and indian remote sensing satellite irs images and related the changes to debris cover supraglacial lakes and moraine dam lakes the glaciers lost an area of 3 3 0 8 between 1989 90 and 2010 more detailed analysis revealed an area loss of 2 00 0 82 2 56 0 61 and 2 28 2 01 km 2 for the periods 1989 97 1997 2004 05 and 2004 2009 10 respectively this indicates an accelerated retreat of glaciers after 1997 on further analysis we observed 1 the formation and expansion of supraglacial lakes on many debris covered glaciers and 2 the merging of these lakes over time leading to the development of large moraine dam lakes we also observed that debris covered glaciers with lakes lose a greater area than debris covered glaciers without lakes and debris free glaciers the climatic data for 24 years 1987 2011 measured at the gangtok meteorological station 1812 m a s l showed that the region experienced a 1 0 degrees c rise in the summer minimum temperature and a 2 0 degrees c rise in the winter minimum temperature indicating hotter summers and warmer winters there was no significant trend in the total annual precipitation we find that glacier retreat is caused mainly by a temperature increase and that debris covered glaciers can retreat at a faster rate than debris free glaciers if associated with lakes

a gcm investigation into the nature of baroclinic adjustment abstract spindown experiments have been conducted using an atmospheric general circulation model to determine the nature and timescale of adjustment to a baroclinically neutral state the spindown was obtained by turning off the radiative cooling of the atmosphere a procedure the authors argue that retains all the relevant constraints on the atmospheric motions a further experiment with radiation and all other physical parameterizations turned off was performed for comparison the neutral state was characterized by increased static stability but little reduction in meridional temperature gradient in the main baroclinic zones however the zones were observed to narrow and were flanked by regions where the meridional temperature gradient was reduced significantly this pattern was repeated in the no physics spin down experiment but in the absence of surface friction and strong orographic drag the flow also appeared to be stabilized by enhanced barotropic shear the neutral states from these two expe

on the characterization of glacier response by a single time scale glacier response to climate can be characterized by a single time scale when the glacier changes sufficiently slowly then the derivative of volume with respect to area defines a thickness scale similar to that of johannesson and others and the time scale follows from it our version of the time scale is different from theirs because it explicitly includes the effect of surface elevation on mass balance rate which can cause a major increase in the time scale or even lead to unstable response the time constant has a dual role controlling both the rate and magnitude of response to a given climate change data from south cascade glacier washington u s a illustrate the ideas some of the difficulty in obtaining accurate values for the thickness and time scales and the susceptibility of all response models to potentially large errors

geology geochronology geochemistry and ore genesis of the wangu gold deposit in northeastern hunan province jiangnan orogen south china abstract the wangu gold deposit in northeastern hunan south china is one of many structurally controlled gold deposits in the jiangnan orogen the host rocks slates of the lengjiaxi group are of neoproterozoic age but the area is characterized by a number of late jurassic cretaceous granites and ne trending faults the timing of mineralization tectonic setting and ore genesis of this deposit and many similar deposits in the jiangnan orogen are not well understood the orebodies in the wangu deposit include quartz veins and altered slates and breccias and are controlled by wnw trending faults the principal ore minerals are arsenopyrite and pyrite and the major gangue minerals are quartz and calcite alteration is developed around the auriferous veins including silicification pyritic arsenopyritic and carbonate alterations field work and thin section observations indicate that the hydrothermal processes related to the wangu gold mineralization can be divided into five stages 1 quartz 2 scheelite quartz 3 arsenopyrite pyrite quartz 4 poly sulfides quartz and 5 quartz calcite the lianyunshan s type granite which is in an emplacement contact with the ne trending changsha pingjiang fracture zone has a zircon la icpms u pb age of 142 2 ma the dayan gold occurrence in the changsha pingjiang fracture zone which shares similar mineral assemblages with the wangu deposit is crosscut by a silicified rock that contains muscovite with a ca 130 ma 40ar 39ar age the gold mineralization age of the wangu deposit is thus confined between 142 ma and 130 ma this age of mineralization suggests that the deposit was formed simultaneously with or subsequently to the development of ne trending extensional faults the emplacement of late jurassic cretaceous granites and the formation of cretaceous basins filled with red bed clastic rocks in northeastern hunan which forms part of the basin and range like province in south china empa analysis shows that the average as content in arsenopyrite is 28 7 atom and the mineralization temperature of the arsenopyrite pyrite quartz stage is estimated to be 245 20 c from arsenopyrite thermometry the high but variable au as molar ratios 0 02 of pyrite suggest that there are nanoparticles of native au in the sulfides an integration of s pb h o he ar isotope systematics suggests that the ore fluids are mainly metamorphic fluids originated from host rocks possibly driven by hydraulic potential gradient created by reactivation of the wnw trending faults initially formed in paleozoic with possible involvement of magmatic and mantle components channeled through regional fault networks the wangu gold deposit shares many geological and geochemical similarities as well as differences with typical orogenic epithermal and carlin type gold deposits and may be better classified as an intracontinental reactivation type as proposed for many other gold deposits in the jiangnan orogen

east asian gold deciphering the anomaly of phanerozoic gold in precambrian cratons early cretaceous orogenic gold deposits in eastern asia are globally unique in that large phanerozoic lode gold deposits occur in archean paleoproterozoic cratons in the northern pacific region ca 125 ma orogenic gold deposits in the north china yangzte and siberian craton margins as well as in young terranes in california may ultimately relate to the giant cretaceous mantle plume in the southern pacific basin and the relatively rapid tectonic consequences along both continental margins from resulting pacific plate reconfigurations in eastern asia such consequences include reactivation of and fluid flow along major fault systems with fluid focusing into simultaneously forming isolated core complexes of uncertain genesis deposition of gold ores in previously devolatilized high grade precambrian metamorphic rocks requires an exotic source of ore fluid most likely subducted mesozoic oceanic crust and or overlying sediment an implication is that phanerozoic metamorphic core complexes in other destabilized craton margins could host large gold resources

remote sensing of glacier change in west greenland accounting for the occurrence of surge type glaciers automated glacier mapping from thresholded band ratios of multispectral satellite data is a well established technique to update glacier inventories over large and remote regions the local glaciers and ice caps on greenland are of particular interest for such efforts as they have been only partly mapped mainly during the 1940s 60s and their potential contribution to global sea level rise could be large here we use three landsat etm scenes from 2001 covering disko island qeqertarsuaq and the nuussuaq and svartenhuk peninsulas west greenland to map the glacier extent in 2001 of 1172 entities we also manually digitize little ice age lia extents from clearly visible trimlines for a subsample of 500 entities in this region with numerous surge type glaciers the related area change calculation is challenging and we consider different samples with and without known surging glaciers for the three regions the mean area changes are 28 20 and 23 respectively when known surge type glaciers are excluded the glaciers on smaller islands and peninsulas closer to the margin of the ice sheet show a lower mean area change of 15 moreover lower 16 and upper 21 bounds are calculated for the overall area changes in the entire region between the lia and 2001 using different upscaling assumptions cumulative length changes since the lia are found to be slightly lower for surge type glaciers

a fluid inclusion and stable isotope study at the loulo mining district mali west africa implications for multifluid sources in the generation of orogenic gold deposits the world class loulo mining district 15 5 moz resource in the birimian terrane of western mali contains a range of mineralogically diverse styles of orogenic gold mineralization the district is distinguished by as rich orebodies as at yalea as well as tourmaline bearing fe rich orebodies as at gara new fluid inclusion and stable isotope data presented here constrain the nature of the hydrothermal fluids responsible for these different types of mineralization and point towards the role of multifluid sources metamorphic and magmatic in the formation of orogenic gold deposits microthermometric and laser raman studies from yalea main and two other similar orebodies loulo 3 and baboto reveal the dominance of coexisting co 2 n 2 ch 4 type 1 and h 2 o nacl type 2 fluid inclusions these inclusions show evidence of fluid unmixing from reduced quartz faylite magnetite qfm buffered low salinity 10 wt nacl equiv co 2 rich h 2 o nacl n 2 ch 4 primary ore fluids the combination of microthermometric data and geothermometry based on ore and alteration assemblages indicate trapping temperatures and pressures of 270 to 340 c at 1 4 to 1 8 kbar the p t x state of the yalea style mineralizing fluids along with the 18 o fluid compositions of 8 8 to 10 7 is consistent with the derivation of auriferous fluids during greenschist facies regional metamorphism of the host terrane similar fluid compositions were previously reported elsewhere in the birimian crust of west africa and in other orogenic gold districts worldwide the precipitation of gold from the h 2 s rich metamorphic fluid is primarily linked to phase separation of the ore fluid which is controlled by p t fluctuations and or fluid rock interaction with carbonaceous host sedimentary rocks confirmed by low 13 c values of 21 7 to 15 8 fluid inclusion investigations from gara and a similar style orebody yalea north indicate the presence of coexisting co 2 n 2 ch 4 type 1 and mixed salinity 5 21 wt nacl equiv co 2 rich h 2 o nacl inclusions type 3 inclusion assemblages also contain common oxidized hematite magnetite hm buffered high temperature 400 c hypersaline 35 50 wt total dissolved solids metalliferous na fe ca cu ni w pb zn multiphase h 2 o rich co 2 nacl fecl 2 inclusions type 4 this inclusion type has not been previously reported in other birimian terranes the composition of the brines along with carbon isotope data 13 c of 14 4 to 4 5 suggests a magmatic input to the gara style hydrothermal system the coexistence in the fluid inclusion assemblages of the magmatic brines with yalea style co 2 rich metamorphic fluids and the positive correlation between salinity and homogenization temperatures suggest mineralization was locally controlled by fluid mixing the interaction of these two chemically contrasting fluids explains the distinctive petrographic characteristics of the gara style orebodies this includes the growth of widespread multi stage fe 3 rich tourmaline b rich granite source and sodic alteration and ore assemblages consisting of abundant nickeloan pyrite ree phosphates ni co pb zn minor trace sulfides and scheelite gold deposition in the gara style hydrothermal system is related to physical and chemical changes of the two fluids during mixing e g decreases in f o2 and t in the brines and retrograde boiling of the co 2 component in the metamorphic fluids a salting out effect

the status and decadal change of glaciers in bhutan from the 1980s to 2010 based on satellite data in order to monitor changes in the glaciers in the bhutan himalaya a repeat decadal glacier inventory was carried out from landsat images of 1977 78 1980 1990 2000 and 2010 the base map of glaciers was obtained by the object based image classification method using the multispectral landsat images of 2010 this method is used separately to delineate clean ice and debriscovered glaciers with some manual editing glacier polygons of 2000 1990 and 1980 were obtained by manual editing on 2010 by separately overlaying respective years the 2010 inventory shows 885 glaciers with a total area of 642 16 1 km the glacier area is 1 6 of the total land cover in bhutan the result of a repeat inventory shows 23 3 0 9 glacial area loss between 1980 and 2010 with the highest loss 11 6 1 2 between 1980 and 1990 and the lowest 6 7 0 1 between 2000 and 2010 the trend of glacier area change from the 1980s to 2010 is 6 4 1 6 loss of glacier area was mostly observed below 5600ma s l and was greater for clean ice glaciers the equilibrium line altitude has shifted upward from 5170 110ma s l to 5350 150ma s l in the years 1980 2010

temporal change of glaciers area and geomorphometric parameters in parbati valley himachal pradesh india temporal change in the glacier coverage is analyzed for the period between 1962 and 2003 in parbati valley himachal pradesh it is observed that the total glacier cover has been decreased by 17 ranging between 8 and 100 for individual glacier the pattern of de glaciation shows a high degree of shrinkage in outer zone of parbati valley while least shrinkage is observed in the inner valley the present study is conducted to establish relationship between glacio geomorphic parameters and glaciers shrinkage pattern to predict the future glacier cover in warming scenario a systematic change is observed for glacio geomorphic parameters associated with temporal change in glacier cover it is observed that mean and minimum elevation slope relief and duration of insolation have changed substantially maximum elevation plan profile curvatures and aspect have shown less change from 1962 to 2003 a correlation matrix between glacio geomorphic parameters for glaciers between 1962 and 2003 shows that the recent glaciers are much more controlled by terrain characteristics than that in the recent past

the effect of glacier wastage on the flow of the bow river at banff alberta 1951 1993 a surface area volume relationship was used to estimate total glacier volumes for the highly glacierized hector lake basin 281 km 2 in the canadian rockies in the years 1951 and 1993 the change in volume was calculated and this value then extrapolated up to the bow basin at banff 2230 km 2 based on relative proportions of glacier cover the mean net glacier volume loss estimate of 934 10 6 m 3 was divided into annual proportions of glacier wastage and storage using a local mass balance record collected at peyto glacier in the mistaya valley contiguous to the bow basin unfortunately the record began in 1966 and a hind cast to 1952 hydrological year was necessary banff maximum summer temperature and lake louise snow course data were used as surrogates for summer and winter glacier mass balance respectively monthly wastage proportions were estimated for 1967 1974 by using modelled values of glacial melt as a template glacier wastage inputs to and storage held back from the bow river hydrograph at banff were compared with known basin yields to assess the hydrological effects of glacier volume change for 1952 1993 the average annual wastage basin yield ratio was found to be around 1 8 for the extremely low flow year of 1970 this ratio increased to 13 the proportion of flow derived from glacier wastage in august of this year was estimated to be around 56 although the results tend to confirm the regulatory effect of glaciers on stream flow it was found that in some years of low flow this situation has been aggravated by water being held in glacial storage

archean gold mineralization synchronous with the final stages of cratonization yilgarn craton western australia sm nd ages of pegmatite dikes that crosscut gold bearing structures in the southern yilgarn craton western australia provide minimum age constraints of 2640 6 11 ma 2628 6 10 ma and 2620 6 36 ma for gold mineralization at the westonia and nevoria yellowdine terrane and scotia norseman terrane gold deposits respectively similarly a post gold mineralization dike at westonia has a u pb zircon age of 2637 68 ma theseconstraintsareconsistentwith andprovidefurthersupportfor suggestionsthatthe majority of gold deposits in the yilgarn craton formed during a regionally extensive gold mineralization event at ca 2630 ma i e 2630 6 10 ma in combination with recent geochronological results these data also provide further evidence that although mineralization appears to significantly postdate the majority of magmatic and metamorphic activity at higher crustal levels widespread thermal reworking of the lower middle crust involvingpartialmelting amphibolitetogranulitefaciesmetamorphism andlowercrustal granitoid intrusion occurred concurrently with gold mineralization at ca 2630 ma it is probable that the large scale hydrothermalfluidflow that produced widespread gold deposition was also part of this tectonothermal event models developed for other archean terranes whereby gold mineralization postdates formation and cratonization of host granite greenstone terranes and is therefore unrelated to these processes are not required to explain the timing of the majority of gold deposits in the yilgarn craton

mean flow adjustment during life cycles of baroclinic waves abstract we use a global primitive equation model to study the evolution of waves growing in a zonal mean state that is initially baroclinically unstable the waves produce changes in the zonal mean state that we compare with changes predicted by baroclinic adjustment theories we examine mean state adjustment by representative zonal wavenumbers 3 7 or 12 in the absence of surface processes as the wave grows to its maximum amplitude it reduces the zonal mean state s potential vorticity gradient through the lower troposphere in accord with adjustment theories over the latitudes with largest wave amplitude changes in the static stability and the zonal wind s vertical shear contribute about equally to the potential vorticity gradient adjustment however during the last day of a wave s growth momentum fluxes strengthen the barotropic component of the zonal wind and the potential vorticity gradient in the middle troposphere changes that are not anticipated by adjustment theory the static stability a

present and future states of himalaya and karakoram glaciers a complete glacier inventory of the himalaya and karakoram h k has been created by merging records from the chinese glacier inventory several regional inventories produced by the international centre for integrated mountain development kathmandu nepal and partial inventories from the geological survey of india the only remaining gap the indian part of kashmir has been filled by a reconnaissance inventory based on soviet military maps at 1 200 000 scale representing the late 1970s it contains records for 3526 glaciers covering 9584 km 2 the new h k inventory contains records and outlines for 20 812 glaciers covering 43 178 km 2 the extent of ice in the karakoram is slightly less than in the himalaya but the karakoram glaciers are on average twice as thick 160 m as against 80 m a glacier by glacier analysis relying on estimates of mass balance for the entire mountain range and on an extension of the often used volume area scaling relation suggests that up to about one fifth of the glaciers present in 1985 may have disappeared already if mass loss were to remain constant at the average rate for 1975 2008 from 3000 to 13 000 more glaciers might disappear by 2035 if mass loss were to continue to accelerate as inferred for 1985 2008 only a few thousand to a few hundred glaciers might remain in 2035 total area and total mass would each decrease by about one half constant rate assumption or three quarters constant trend assumption these projections which are uncertain and neglect some possibly important mitigating controls such as variable extents of debris cover and the feedback due to retreat to higher elevations demonstrate the need for more complete analyses to inform public perceptions of and policy decisions relating to the health of h k glaciers

geological and isotopic constraints on ore genesis huangjindong gold deposit jiangnan orogen southern china abstract the huangjindong gold deposit with gold resources of 80 t is hosted in neoproterozoic slates along the chang ping fault in the jiangnan orogen southern china the orebodies are dominated by auriferous arsenopyrite pyrite quartz scheelite veins quartz rich breccias that are cemented by late arsenopyrite pyrite muscovite and quartz auriferous stibnite quartz veins and disseminated gold in arsenopyrite pyrite sericite quartz altered rocks neither significant alteration zoning nor ore element zoning are recognized within the orebodies although the orebodies at shallower crustal levels are slightly more stibnite rich at the regional scale the first order control on the distribution of gold deposits is the nne to ne trending crustal scale sinistral strike slip chang ping fault as in other gold provinces globally this controlling fault is not gold mineralized the gold occurrs in wnw to e w trending zones of thrusts and fracture arrays associated with tight locked up asymmetrical folds the broadly e w trending orebodies formed independently within approximately ne trending fault bounded corridors defined by the first order chang ping and second order ni wan and keng shang chang long faults hydrothermal activity was initiated at the ductile brittle transition but evolved to brittle dominated deformation all within a transpressional environment oxygen and hydrogen isotope compositions of fluids d 44 4 to 34 2 18o 8 6 to 9 5 calculated from gold related hydrothermal quartz and hydrothermal sericite respectively are consistent with a metamorphic source sulfur isotope compositions of the gold bearing arsenopyrite and pyrite median values between 8 0 and 6 0 are generally distinct from 34s of the regional neoproterozoic slates in the jiangnan orogen but overlap the compositions of pyrites in global sediment hosted orogenic gold deposits lead isotope compositions of the gold bearing arsenopyrite and pyrite 206pb 204pb 17 049 to 18 417 207pb 204pb 15 263 to 15 712 208pb 204pb 37 597 to 39 220 suggest that the lead was sourced from metamorphic rocks involved in the orogenic events therefore both the stable and radiogenic isotopic data indicate that ore forming fluids and metals were derived from a metamorphic source although the precise nature of that source is unclear on the basis of these geological and isotopic data huangjindong is interpreted as an orogenic gold deposit the gold ore bodies show classic structural controls being adjacent at the province scale to the crustal scale chang ping fault but located in thrusts and associated tight anticlinal fold hinges that lie in corridors between markedly oblique relatively brittle fault arrays that parallel the chang ping fault

package fluids 1 computer programs for analysis of fluid inclusion data and for modelling bulk fluid properties the computer package fluids contains five sets of computer programs written in c for the calculation of fluid properties both model fluids and data from fluid inclusions can be analysed in the programs bulk density molar volume and composition of fluid inclusions are calculated with the program bulk which uses microthermometric data micro raman spectroscopic data cation ratios and volume fraction estimations as input the program offers a broad variety of equations of state which are selected according to the fluid system or the temperature and pressure conditions of interest the isochores that correspond to the output or test v x properties of fluid inclusions are calculated by the program isoc in calculating the isochores this program takes account of the compressibility and expansion of selected host minerals the program test allows different equations of state to be compared directly with experimental data thereby facilitating selection of the most adequate model in the programs bulk and isoc loner is a group of programs that handle individual equations of state eos for all fluid systems presented in the programs bulk and isoc aqso is a group of programs that allows purely empirical modelling of electrolyte bearing aqueous solutions henry s law for dilute gas bearing aqueous solutions and osmotic coefficients for dilute electrolyte bearing aqueous solutions the programs are available on the university of leoben web site at http www unileoben ac at buero62 minpet ronald

nature age and tectonic setting of granitoid hosted orogenic gold deposits of the jiaodong peninsula eastern north china craton china the jiaodong gold province along the southeastern margin of the north china craton has combined production and resources of 900 tonnes of gold more than 95 of the gold in this province is hosted in mesozoic granitoids which intruded late archean metamorphic basement rocks episodically at ca 160 150 and 130 126 ma the deposits of the jiaodong peninsula form one of the largest provinces of granitoid hosted lode gold deposits in the world the jiaodong gold deposits occur as massive auriferous quartz veins hosted in subsidiary second or third order faults and as disseminated and stockwork style mineralization hosted in alteration zones along major regional scale faults mineralization took place during brittle reactivation d3 of pre existing d2 ductile shear zones wall rock alteration is dominated by k feldspar and sericite with also sulfide minerals and extensive silicification closest to the orebodies the alteration was accompanied by the introduction of volatiles fe mg k rb ag as au bi and sb enrichment of base metals in the gold lodes is generally low although locally significant gold deposition took place at temperatures of 250 to 350 c for most gold deposits and the ore fluids are co2 bearing and have calculated salinities of 6 13 wt nacl equiv deposits from the zhao ye xixia and muping rushan belts have similar if not identical structural controls alteration patterns ore mineral assemblages and stable isotope signatures lead isotope data indicate that the ore stage leads were buffered by their host rocks the granitoid hosted gold deposits in the zhao ye belt are most radiogenic the greenstone hosted deposits in the xixia belt is the least radiogenic and the granitoid hosted deposits in the muping rushan belt have intermediate compositions gold mineralization in the zhao ye xixia and muping rushan belts in the jiaodong gold province appears to be broadly contemporaneously at ca 130 120 ma as constrained by shrimp u pb zircon dating on host rocks and a post gold dike as well as by ar ar rb sr and k ar dating of hydrothermal alteration minerals and ores this early cretaceous age is about 100 million years younger than the peak of ultra high pressure metamorphism in the qinling dabie sulu orogen between the north china and yangtze cratons and about 500 km south of the gold province however it overlaps with the extension and exhumation stage of the collisional orogeny and the subduction of the pacific plate beneath the eurasian continental crust whereas the majority of the jiaodong gold deposits occur on the margin of the north china craton some also occur in the suture zone between the two cratons they are significantly landward relative to the subduction zone of the pacific plate compared with typical orogenic lode gold deposits globally lode gold deposits of ca 130 120 ma occurred on both sides of the tan lu fault zone available data favor a temporal link of gold mineralization with pacific plate subduction

surface flux regulation of the coupling between cumulus convection and baroclinic waves abstract the authors examine the role of convection in the dynamics of eddy life cycles through numerical experiments using initial states that are baroclinically and conditionally unstable in midlatitudes the location of wave induced convection and its influence on the growing wave depends on how strongly the wave is coupled to the lower boundary through surface fluxes for all three convective schemes used here emanuel modified grell modified kuo convective destabilization is favored in the wave s warm sector when there are no surface fluxes included in the simulation and in the cold sector when there are convection is also shallower when it occurs in the cold sector though still precipitating for simulations using emanuel convection the relatively shallow convection plays a central role in a water cycle wherein 1 evaporation gives moisture to the cold sector s boundary layer 2 convection pumps some of the moisture into the lower troposphere above the boundary layer 3 the large scale circ

mineralogical and isotopic constraints on the genesis of the jingchong co cu polymetallic ore deposit in northeastern hunan province south china abstract the jingchong co cu polymetallic deposit and a few other co polymetallic ore deposits are located in northeastern hunan province in the central segment of the jiangnan orogen south china these deposits occur along the ne trending changping changsha pingjiang deep fault zone and show a spatial association with the late jurassic early cretaceous lianyunshan granitoids which intruded the archean to paleoproterozoic lianyunshan group comprising metaclastic sedimentary rocks interlayered with mafic intermediate igneous rocks the jingchong deposit is hosted within an altered fracture zone at the footwall of the changping fault zone and comprises an upper pb zn ore zone and a lower co cu ore zone wall rock alteration is dominated by silicification and chloritic alteration three types of ores were identified i e quartz sulfide veins altered structural breccias and altered fractured rocks integrated field work and microscopy observations reveal a three stage hydrothermal process related to mineralization 1 quartz chlorite chli pyrite 2 quartz chlorite chlii pyrite chalcopyrite cobaltite and 3 quartz carbonate galena sphalerite pyrite chalcopyrite la icpms analyses reveal that the co contents are 1315 6473 ppm 76 3866 ppm and 5 435 ppm for pyrite from the first the second and the third stages respectively epma analyses of chlorite show that chli and chlii have fe fe mg ratios of 0 65 0 80 and 0 76 0 92 and aliv contents of 1 30 1 65 apfu atom per formula unit and 1 18 1 48 apfu respectively empirical geothermometry of chlorite yielded temperatures of 256 318 c av 281 c and 239 290 c av 256 c for first and second stage chlorite respectively the 34svcdt values of sulfides 4 9 to 0 2 av 1 6 suggest a magmatic source for the sulfur and the 3he 4he 0 017 0 30 ra and 40ar 36ar 285 306 ratios of fluid inclusions in pyrite suggest that the ore forming fluids were mainly crust derived magmatic hydrothermal fluids with possible meteoric water inputs the 206pb 204pb 18 042 18 746 207pb 204pb 15 592 15 741 and 208pb 204pb 38 237 39 150 ratios of ore sulfides are similar to those of the lianyunshan group suggesting that the metals may have been derived from the latter integrating the geological mineralogical and geochemical data documented in this study we propose that the jingchong co cu polymetallic deposit formed from a hydrothermal system related to the lianyunshan pluton which was derived from crustal anataxis of the lianyunshan group in a back arc extensional setting in the late mesozoic

glacier volume estimation on cascade volcanoes an analysis and comparison with other methods during the 1980 eruption of mount st helens the occurrence of floods and mudflows made apparent a need to assess mudflow hazards on other cascade volcanoes a basic requirement for such analysis is information about the volume and distribution of snow and ice on these volcanoes an analysis was made of the volume estimation methods developed by previous authors and a volume estimation method was developed for use in the cascade range a radio echo sounder carried in a backpack was used to make point measurements of ice thickness on major glaciers of four cascade volcanoes mount rainier washington mount hood and the three sisters oregon and mount shasta california these data were used to generate ice thickness maps and bedrock topographic maps for developing and testing volume estimation methods subsequently the methods were applied to the unmeasured glaciers on those mountains and as a test of the geographical extent of applicability to glaciers beyond the cascades having measured volumes two empirical relationships were required in order to predict volumes for all the glaciers generally for glaciers less than 2 6 km in length volume was found to be estimated best by using glacier area raised to a power for longer glaciers volume was found to be estimated best by using a power law relationship including slope and shear stress the necessary variables can be estimated from topographic maps and aerial photographs

a stand alone co mineral deposit in northeastern hunan province south china its timing origin of ore fluids and metal co and geodynamic setting abstract the hengdong cobalt co deposit located in northeastern hunan province of south china is hosted by the low grade metamorphic volcaniclastic sedimentary rocks of the early neoproterozoic lengjiaxi group the co orebodies strictly controlled by the ne to ene trending changsha pingjiang deep fault zone cpdfz and its secondary structures occurring in altered breccias and cataclasites with similar mineral assemblages co mineralization is characterized by zoned alteration with predominant silicification and chloritization proximal to the orebodies and sericitization and carbonatization distal from the mineralization the integrated field and microscope observations reveal three hydrothermal stages marked by quartz pyrite muscovite chalcopyrite of the early stage mineralization e stage quartz polymetallic sulfides chlorite of the middle stage mineralization m stage and quartz chlorite carbonate of the late stage mineralization l stage muscovite from both the e stage co bearing altered breccia and the cpdfz mylonite yield 40ar 39ar plateau ages of 124 7 0 6 ma 1 and 130 3 1 4 ma 1 respectively indicating an early cretaceous mineralization likely associated with the last movement of cpdfz strike slip shearing the 34s values of pyrite and chalcopyrite ranging from 1 5 to 15 9 with a majority between 7 5 and 15 9 and the lead isotope compositions of the pyrite 206pb 204pb 18 156 18 761 207pb 204pb 15 645 15 662 and 208pb 204pb 38 469 39 172 overlapping with those of upper crust indicate a main crust derived source the chemical compositions of pyrite further indicate the ore fluids and metal co of the hengdong deposit are most likely linked to the meta mafic and volcanic rocks of the neoarchean to paleoproterozoic lianyunshan group but with a contamination by the wall rocks of lengjiaxi group and lianyunshan granitoids fluid inclusion investigations from hengdong deposit reveal the decreasing homogenization temperatures from 250 to 320 c peak of 280 300 c at the e stage through 220 320 c peak of 270 300 c at the m stage and to 150 230 c at the l stage without obviously salinity 7 0 15 wt nacl equiv changed in the m stage the presence of coexisting lv inclusions and v rich inclusions with the similar homogenization temperature consistent with the chlorite geothermometry data is interpreted to be the result of fluid immiscibility which was caused by cyclic pressure release during fault zone movement combined with the late mesozoic tectonism of south china the present data support the hengdong deposit formed under an extension associated tectonic regime most likely induced by slab roll back of the subducted paleo pacific plate during the early cretaceous this extensional event not only caused the reactivation of the pre existing structures as manifested by the cpdfz characteristic of stress transformation from compression to extension but also likely resulted in the release of large amounts of co bearing ore fluids from the proterozoic or older volcanogenic rocks when the ore fluids migrated along the cpdfz and its secondary faults the decompression adiabatic cooling of the hydrothermal fluids shifted the ore fluid to the immiscibility field significantly reduced the degree of cobalt undersaturation and caused cobalt to precipitate which finally formed the hengdong co mineral deposit

structural development of the lower paleozoic belt of south china genesis of an intracontinental orogen abstract an extensive structural study of wuyishan and surrounding areas south china brings data on the structures formed prior to the devonian unconformity building the lower paleozoic belt an ordovician tectonic event was responsible for i south directed structures in the wuyishan proper and its southern border related to both thin and thick skinned tectonics accompanied by metamorphism and crustal thickening ii north directed structures to the west of ganjiang fault and north of jiangshan shaoxing fault where only thin skinned tectonics is visible the southward deformation accommodating the shortening includes emplacement of thrust sheets involving deep crustal material and some mantle peridotite and likely repetition of continental material both responsible for crustal thickening the orogeny was due to the underthrusting of the southern part of the south china block beneath the northern part of this block closing the pre existing nanhua rift created at around 850 800 ma and involving the rift sedimentary fill in the southward thrusting the syn metamorphic tectonic piling was followed by anatexis and granite emplacement at around 440 390 ma our new u th pb epma monazite dating gives ages of 433 9 ma and 437 5 ma early silurian for the main anatectic event and a younger age of 412 5 ma late silurian early devonian for a late re heating process the lower paleozoic belt is an intracontinental orogen without oceanic suture record it shows some similarities with the cenozoic european pyrenees chain with a strong asymmetry

the early cretaceous yangzhaiyu lode gold deposit north china craton a link between craton reactivation and gold veining the yangzhaiyu gold deposit is one of numerous lode gold deposits in the xiaoqinling district southern margin of the north china craton gold mineralization is hosted in neoarchean to early paleoproterozoic amphibolite facies metamorphic rocks and consists of auriferous quartz veins and subordinate disseminated ores in the vein proximal alteration zone ore related hydrothermal alteration is dominated by sericite quartz sulfide assemblages close to gold veins and biotite quartz pyrite chlorite epidote alteration generally distal from mineralization pyrite is the predominant sulfide mineral locally coexisting with minor amounts of chalcopyrite sphalerite and galena gold occurs mostly as free gold enclosed in or filling microfractures of pyrite and quartz and is also present in equilibrium with au bearing tellurides mainly petzite and calaverite coexisting with hessite tellurobismuthite and altaite fluid inclusion studies suggest that gold veins were deposited at intermediate temperatures 175 313 c from aqueous or aqueous carbonic fluids with moderate salinity 5 14 wt nacl equiv 34s values of sulfide minerals range mainly from 2 0 to 4 4 whereas auriferous quartz vein samples have 18o values of 12 4 to 9 6 with calculated 18oh2o values of 6 0 to 3 2 gold related pyrite grains yield elevated 3he 4he ratios 1 51 0 32 ra relative to crustal reservoirs and mantle like 20ne 22ne and 21ne 22ne ratios 9 90 9 68 and 0 029 respectively the stable and noble gas isotopes thus suggest deep seated most likely magmatic and mantle derived sources for the ore fluids sulfur and by inference other components in the ore system 40ar 39ar dating of ore related sericite and biotite separates indicates two episodes of gold genesis at 134 5 to 132 3 and 124 3 to 123 7 ma the mineralization ages overlap zircon u pb ages of 141 0 1 6 to 125 8 1 4 ma 2 for the wenyu and niangniangshan monzogranite plutons and a number of mafic to intermediate dikes intruding these plutons all being proximal to the yangzhaiyu gold deposit the synchronism of gold genesis and magmatism provides additional weights of evidence for a magmatic derivation of ore fluids and sulfur the geochronologic data also suggest that gold veining took place billions of years after the stabilization of the north china craton and associated metamorphism in the late archean to early paleoproterozoic this contrasts sharply to lode gold deposits in other precambrian cratons that formed predominantly in late archean to paleoproterozoic temporarily and genetically related to regional high grade metamorphism and compressional or transpressional tectonism available data have demonstrated that the north china craton was reactivated in the late mesozoic as marked by voluminous igneous rocks faulted basin formation high crustal heat flow and widespread metamorphic core complexes in the eastern part of the craton it is thus suggested that the yangzhaiyu gold deposit together with other deposits of similar ages in the xiaoqinling district were products of this craton reactivation event lithospheric extension and extensive magmatism related to the craton reactivation may have provided sufficient heat energy fluid and sulfur required for the formation of the gold deposits

an early paleozoic orogenic gold belt along the jiang shao fault south china evidence from fluid inclusions and rb sr dating of quartz in the huangshan and pingshui deposits abstract there are several gold deposits in the eastern section of the regional jiang shao fault between the yangtze and cathaysia blocks in south china auriferous quartz veins in these deposits are strictly hosted in second order ne trending ductile shear zones the ores generally contain low amounts of sulfide minerals

the equilibration of short charney waves implications for potential vorticity homogenization in the extratropical troposphere in this paper the authors discuss the vertical distribution of the interior potential vorticity gradients in the extratropical troposphere in an idealized setting this structure is characterized by large positive gradients at the top of the boundary layer and a narrow homogenized region in the interior to understand this partial homogenization the authors have looked at how charney waves of different scales equilibrate it is shown that when the interior gradients of potential vorticity are small compared to the delta function at the ground the modes can equilibrate without eliminating the lower level shear as is the case in the eady model these neutral states can exist even though they violate the charney stern condition for stability the equilibration process also produces a concentration of the potential vorticity gradients at heights of the order of the rossby depth which can be regarded as a boundary to the interior mixing of potential vorticity the extent of interior potential vorticity mixing required for equilibration depends on the ratio between the boundary and interior potential vorticity gradients it is implicit in the analysis of previous authors that this ratio is close to 1 in midlatitudes which implies that an eady model with full homogenization of the interior potential vorticity gradients is not an appropriate paradigm for the midlatitude troposphere nevertheless it is argued that localized interior potential vorticity mixing could be sufficient for neutralizing the shortest waves

mesozoic large scale magmatism and mineralization in south china preface abstract south china is famous for its polymetallic deposits with more than 50 of the world s w and sb reserves and 20 of the sn reserves as well as abundant cu mo pb zn au ag ta nb hree and u this special issue reports recent progress on the tectonic evolution magmatism and ore deposits of south china which leads to a more comprehensive understanding of the mesozoic large scale magmatism and mineralization events 1 south china has been located in backarc settings during multiple subductions since the paleozoic which may have contributed to pre enrichments of the ore forming materials 2 the pacific plate subduction was a principle factor that controlled the late mesozoic large scale magmatism and mineralization in south china through flat subduction ridge subduction slab tearing and slab rollbacks

intracontinental subduction a possible mechanism for the early palaeozoic orogen of se china the early palaeozoic orogen of se china consists of three lithotectonic elements from top to bottom a sedimentary upper unit a metamorphic lower unit and a gneissic basement the boundaries between these units are flat lying south directed ductile decollements the lower one is coeval with an amphibolite facies metamorphism m1 the belt is reworked by migmatite granite domes high temperature metamorphism m2 and granitic plutons related to post orogenic crustal melting we date here the syn m1 ductile shearing at 453 7 ma by u th pb method on monazite previous ages and our new 40 ar 39 ar ages of biotites and muscovites show that the metamorphic rocks experienced syn m2 exhumation from 440 to 400 ma the early palaeozoic orogen of se china is an intracontinental belt in which decollements accommodated the north directed subduction of the cathaysian continent this orogen is an example of intracontinental subduction that was not preceded by oceanic subduction

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

a century of glacier change in the wind river range wy abstract the wind river range spans roughly 200 km along the continental divide in western wyoming and encompasses at least 269 glaciers and perennial snowfields totaling 34 34 0 13 km 2 2006 including gannett glacier the largest glacier 2 81 km 2 in the continental u s outside of washington state to track changing glacier and perennial snow surface area over the past century we used historic maps aerial photography and geologic evidence evident in said imagery since the end of the little ice age 1900 when the glaciers retreated from their moraines to 2006 the ice covered area shrank by 47 the main driver of surface area change was air temperature with glaciers at lower elevations shrinking faster than those at higher elevations the total contribution of ice wastage to late summer stream flow ranged from 0 4 to 1 5 0 9 to 2 8 1 7 to 5 4 and 3 4 to 10 9 in four different watersheds none of which exceeded 7 glacier cover results from previous studies were difficult to include because of differences in interpretation of glacier boundaries because of poor imagery or to extensive seasonal snow these difficulties highlight potential problems in combining data sets from different studies and underscores the importance of reexamining past observations to ensure consistent interpretation

a new glacier inventory for the svartisen region norway from landsat etm data challenges and change assessment glaciers are widely recognized as key indicators of climate change and their meltwater plays an important role in hydropower production in norway since the last glacier inventory was compiled in northern norway in the 1970s marked fluctuations in glacier length and mass balance have been reported for individual glaciers and the current overall glacier state is thus not well known within the framework of the global land ice measurements from space glims initiative we have created a new inventory for 489 glaciers in the svartisen region northern norway using a landsat enhanced thematic mapper plus etm satellite scene from 7 september 1999 and automated multispectral glacier mapping thresholded band ratios in addition visual inspection and correction of the generated glacier outlines has been applied adverse snow conditions and uncertain drainage divides made glacier mapping challenging in some regions of the study site glacier outlines from 1968 as digitized from a topographic map were used for a quantitative change assessment for a selection of 300 glaciers the overall area change of this sample from 1968 to 1999 was close to zero but with a strongly increasing scatter towards smaller glaciers large area gains 50 for small glaciers 1 km 2 and an unexpected stronger relative area loss towards the wetter coast the overall size changes are small 1 for the three largest ice masses in the study region vestisen ostisen and blamannsisen

landsat based inventory of glaciers in western canada 1985 2005 abstract we report on a glacier inventory for the canadian cordillera south of 60 n across the two western provinces of british columbia and alberta containing 30 000 km2 of glacierized terrain our semi automated method extracted glacier extents from landsat thematic mapper tm scenes for 2005 and 2000 using a band ratio tm3 tm5 we compared these extents with glacier cover for the mid 1980s from high altitude aerial photography for british columbia and from landsat tm imagery for alberta a 25 m digital elevation model dem helped to identify debris covered ice and to split the glaciers into their respective drainage basins the estimated mapping errors are 3 4 and arise primarily from seasonal snow cover glaciers in british columbia and alberta respectively lost 10 8 3 8 and 25 4 4 1 of their area over the period 1985 2005 the region wide annual shrinkage rate of 0 55 a 1 is comparable to rates reported for other mountain ranges in the late twentieth century least glacierized mountain ranges with smaller glaciers lost the largest fraction of ice cover the highest relative ice loss in british columbia 24 0 4 6 occurred in the northern interior ranges while glaciers in the northern coast mountains declined least 7 7 3 4

mesoproterozoic neoproterozoic transition geochemistry provenance and tectonic setting of clastic sedimentary rocks on the se margin of the yangtze block south china abstract the se margin of the yangtze block south china is composed of the mesoproterozoic lengjiaxi group and the neoproterozoic banxi group with sinian and post sinian cover a geochemical study was undertaken on the mesoproterozoic neoproterozoic clastic sediments in order to delineate the characteristics of the sediment source and to constrain the tectonic development and crustal evolution of south china our results show that the mesoproterozoic clastic sediments have a dominant component derived from a metavolcanic plutonic terrane with a large of mafic component there is a minor contribution of mafic rocks and older upper crustal rocks to the provenance strong chemical weathering in the source area occurred before transport and deposition the provenance for the neoproterozoic clastic sediments was most likely old upper continental crust composed of tonalite granodiorite dominated tonalite granodiorite granite source rocks which had undergone strong weathering and or recycling a minor component of older k rich granitic plutonic rocks and younger volcanogenic bimodal rocks is also indicated based on the regional geology the geochemical data and the inferred provenance the mesoproterozoic group is interpreted as a successive sedimentary sequence deposited in an extensional rifting back arc basin adjacent to a 1 80 ga continental margin arc terrane the progressive extension rifting of the back arc basin was followed by increasing subsidence and regional uplift during continental marginal arc continent the cathaysian block collision at 1 0 ga caused the deposition of the neoproterozoic group into back arc to retro arc foreland basin therefore the depositional setting of the proterozoic clastic sediments and associated volcanic rocks within the back arc basin reflected basin development from an active continental margin back arc basin with extension or rifting of the back arc basin to a passive continental margin

the physical basis of glacier volume area scaling ice volumes are known for only a few of the roughly 160 000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates a scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas the relationship requires four closure choices for the scaling behavior of glacier widths slopes side drag and mass balance reasonable closures predict a volume area scaling exponent which is consistent with observations giving a physical and practical basis for estimating ice volumes glacier volume is insensitive to perturbations in the mass balance scaling but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume

glacier and permafrost signals of 20th century warming currently available evidence of 20th century warming from glaciers and permafrost is briefly reviewed the signals are clear and strong warming of polar firn and permafrost and mass losses of glaciers at lower latitudes were most striking towards the middle of the century the easily observable length reduction of mountain glaciers confirms the global character of the evolution a probably intermittent reversal of the trend was observed in places after about 1950

giant mesozoic gold provinces related to the destruction of the north china craton abstract lode gold deposits in precambrian cratons represent the world s major gold source and were mostly generated during formation and stabilization of the cratons however there is an extraordinary exception in the north china craton ncc where lode gold deposits formed after prolonged stabilization of the craton molybdenite re os and hydrothermal sericite and biotite 40 ar 39 ar dating of major gold deposits from the xiaoqinling district southern ncc bracket their emplacement in the range of 154 1 1 1 to 118 9 1 2 ma n 23 postdating formation of the craton by more than 1 7 billion years fluid inclusions extracted from gold bearing pyrite have elevated 3 he 4 he ratios 1 52 0 22 ra and mantle like ne isotopes 20 ne 22 ne 10 02 9 22 and 21 ne 22 ne 0 033 0 027 indicating presence of mantle derived fluids in the ore system measured 34 s of pyrite and d and 18 o of hydrothermal micas and fluid inclusion waters in auriferous quartz further confirm a magmatic mantle source for sulfur and ore fluids gold deposits of similar ages also widely occur in the eastern and northern margins of the ncc which together with those in the xiaoqinling district have a total reserve of 2500 t gold forming the only known giant late mesozoic gold province in the world s precambrian cratons these deposits formed coevally with extensive felsic to mafic magmatism development of intracontinental rift basins and exhumation of metamorphic core complexes across the eastern ncc events interpreted as indicating thinning and destruction of the lithosphere beneath the craton rising of asthenosphere coupled with destruction of the lithosphere has generated voluminous mafic and felsic magmas that provided sufficient fluids sulfur and by inference other ore components to form the giant gold provinces

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

caledonian early paleozoic veins overprinted by yanshanian late mesozoic gold mineralization in the jiangnan orogen a case study on gold deposits in northeastern hunan south china abstract the jiangnan orogen situated between the yangtze and cathaysia blocks in south china is an important gold polymetallic metallogenic belt in china like many gold deposits hosted in precambrian rocks in eastern china the timing of gold mineralization in the jiangnan orogen mostly hosted by neoproterozoic rocks has been controversial a number of previous geochronological studies have suggested that mineralization ages range from neoproterozoic to cretaceous with caledonian early paleozoic and yanshanian jurassic cretaceous being considered most important as caledonian is the most important period of regional metamorphism and yanshanian is the most important period of granitic magmatism the timing of mineralization is closely related to the genetic nature orogenic versus post orogenic of the gold mineralization this paper addresses these problems by studying the ages and characteristics of ore forming fluids of two major gold deposits wangu and huangjindong in the central part of the jiangnan orogen in northeastern hunan muscovite ar ar dating suggests that the bulk of the quartz veins in the wangu and huangjindong deposits were formed at ca 399 397 ma i e during the caledonian orogeny whereas gold mineralization and associated veining took place at ca 142 130 ma i e during the yanshanian orogeny fluid inclusions in the barren caledonian veins are characterized by the h2o nacl co2 system homogenization temperatures of 266 276 c and salinities of 5 5 4 wt nacl equivalent similar to those found in many orogenic type gold deposits whereas the fluid inclusions in the gold bearing yanshanian veins with abundant sulfides overprinting the barren veins have a h2o nacl composition system homogenization temperatures of 169 to 256 c and salinities from 8 7 to 15 2 wt nacl equivalent it is proposed that both the caledonian and yanshanian veining events are controlled by the same fracture systems with the former being formed in a relatively deep orogenic deformation metamorphic environment and the latter in a relatively shallow extensional environment accompanied by extensive granitic magmatism reactivation of the caledonian structures during the yanshanian orogeny together with availability of sulfur and gold possibly associated with granitic intrusions played a key role in the formation of the gold deposits in northeastern hunan and possibly elsewhere in the jiangnan orogen

the archaean mount gibson gold deposits yilgarn craton western australia products of combined synvolcanic and syntectonic alteration and mineralisation abstract the mount gibson gold deposits are sited at the southern tip of the archaean yalgoo singleton greenstone belt in the southern portion of the murchison province yilgarn craton western australia primary gold mineralisation is hosted within an eastward facing dominantly tholeiitic metabasalt sequence which has been metamorphosed to amphibolite facies conditions alteration and mineralisation occurs within the north to north northeast striking steeply east dipping mount gibson shear zone paralleling primary layering within the tholeiitic mine sequence two main styles of wallrock alteration and associated sulphide mineralisation are present the first of these is represented by garnet spessartine almandine gahnite and cordierite muscovite bearing schists these lithologies are unusual for lode gold mineralisation and despite their apparently pelitic nature have mafic precursors and reflect pre metamorphic alteration of tholeiitic basalts the garnet bearing schists form a coherent stratiform horizon which overlies the main ore zone at the orion two deposit and are associated with recrystallised metamorphosed polymetallic sphalerite galena pyrite pyrrhotite chalcopyrite tetrahedrite mineralisation a more typical for archaean lode gold pervasive syn peak metamorphic syn shearing quartz biotite sulphide alteration envelope is associated with pyrrhotite pyrite chalcopyrite mineralisation at mount gibson although free gold is rare there is a strong empirical relationship between enhanced gold grades and the pyrrhotite pyrite chalcopyrite assemblage suggesting that gold was introduced as part of this event mass balance calculations at orion two show enrichment of au ag k rb ba and w and depletion of na ca and sr over mineralised zones which is typical of lode gold mineralisation however the deposit also exhibits strong base metal enrichment particularly within the garnet bearing schists and zonation from the au cu enrichment of the main ore zone to the overlying stratiform pb zn ag mn enrichment which is dominant in the garnet bearing schist horizon these features are typical of vhms mineralisation hornet exhibits similar overall elemental enrichment and depletion to orion two lead isotope data for sulphides from orion two and hornet provide evidence of two discrete mineralising events at mount gibson separated by approximately 300 m y a two stage model best explains the features of the mount gibson gold deposits metamorphism of the aluminous alteration and weak mineralisation associated with an early synvolcanic event resulted in the formation of cordierite muscovite and garnet spessartine almandine gahnite bearing assemblages respectively which were less competent than the surrounding tholeiitic metabasalts and consequently tended to localise shearing shear hosted lode gold mineralisation was synchronous with peak metamorphism and shearing like the shearing hydrothermal alteration was mostly concentrated in and around the less competent rocks which were produced by metamorphism of synvolcanically altered precursors resulting in a fundamental stratigraphic control on gold mineralisation at mount gibson

utilization of pre existing competent and barren quartz veins as hosts to later orogenic gold ores at huangjindong gold deposit jiangnan orogen southern china most if not all orogenic gold deposits form during the late stages of deformation in some cases there is barren pre mineralization hydrothermal alteration which may be part of a single progressive hydrothermal event or a temporally distinct event relative to deposition of gold at the huangjindong orogenic gold deposit in the jiangnan orogen of southern china there are two phases of vein generation the earlier of which is largely barren structural analysis petrography mineralogy and in situ laser ablation inductively coupled plasma mass spectrometry la icp ms gold mapping of different generations of gold bearing sulfides reveal the relationship between different phases of hydrothermal alteration and quartz veins pre existing barren and brittle quartz veins which are controlled by tight folds and thrust faults provide favorable competent hosts for later overprinting by gold bearing ore bearing fluids that infiltrated during ongoing reverse sinistral fault movement these overpressured fluids caused hydrofracturing to complete brecciation of segments of the earlier quartz veins and associated pre existing breccias with deposition of auriferous quartz sulfide veins and breccia cements or matrices within them although fluid inclusion data are non definitive fluid pressure fluctuations are interpreted to have resulted in phase separation within the ore fluid which was primarily responsible for destabilization of gold complexes and deposition of native gold with other invisible gold bearing ore related sulfides formed by sulfidation reactions in hydrofractures and breccia matrices thus competent barren quartz veins in fold thrust belts may locally host superimposed gold mineralization and provide favorable targets for gold resources

geochemistry and geochronology of the banxi sb deposit implications for fluid origin and the evolution of sb mineralization in central western hunan south china abstract central western hunan in south china hosts the largest antimony belt in the world with two types of sb deposits identified sb au woxi type and sb only xikuangshan type banxi is the most representative deposit in the region with vein type sb mineralization hosted in neoproterozoic clastic rocks stibnite developing in ores and arsenopyrite mainly occurring in altered country rocks trace element contents including rare earth elements ree and isotopic ratios s pb sr nd he and ar in stibnite and or arsenopyrite were analyzed to determine the timing of ore formation and to elucidate fluid origin and evolution processes most sulfides have high ree contents 45 103 ppm moderate fractionation between lree and hree lree hree 6 38 11 56 and slightly negative eu anomalies eu eu 0 53 0 72 the 34 s values are 3 88 5 81 for stibnite and 9 25 11 82 for arsenopyrite the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios range from 18 617 to 18 635 15 695 to 15 739 and 38 965 to 38 981 for stibnite and from 18 594 to 18 609 from 15 587 to 15 698 and from 38 893 to 38 926 for arsenopyrite the 87 rb 86 sr and 87 sr 86 sr ratios are 0 3016 3 538 and 0 711463 0 717591 respectively for stibnite and 0 2251 2 214 and 0 711244 0 711565 respectively for arsenopyrite the 147 sm 144 nd and 143 nd 144 nd ratios are 0 1174 0 9816 and 0 511942 0 512768 for stibnite with end t values t 130 ma ranging from 12 4 to 6 6 and two stage model ages t 2dm ranging from 1457 to 1932 ma the 40 ar 36 ar and r ra ratios where ra is the atmospheric 3 he 4 he ratio of 1 4 10 6 are 409 545 and 0 0088 0 0348 respectively for stibnite the rb sr and sm nd isotopic analyses of the sulfides yield isochron ages of 129 4 2 4 ma 2 mswd 1 3 and 130 4 1 9 ma 2 mswd 1 6 respectively the combined trace element and isotopic data set indicates that the ore forming fluids were a mixture of dominantly deep basement derived solute rich parent water and a small amount of dilute heated meteoric water the decreases in ree 34 s 206 pb 204 pb 207 pb 204 pb 208 pb 204 pb 87 rb 86 sr 87 sr 86 sr 147 sm 144 nd and 143 nd 144 nd and increases in 40 ar 36 ar and 4 he contents in the stibnite from the earlier quartz stibnite mineralization stage stage ii through to the later stibnite mineralization stage stage iii indicate that the influx of meteoric water increased during sb mineralization the deep sourced relatively high temperature rock reacted fluid mixed with increasing amounts of more oxidized low temperature meteoric fluids causing the precipitation of arsenopyrite and stibnite sequentially at the banxi deposit a two period genetic model has been proposed for the world class sb mineralization in the central western hunan region the woxi type sb au deposits were derived from orogenic fluids generated from folding and shearing during the caledonian and indosinian orogeny whereas the xikuangshan type sb deposits were formed by mixing heated basement derived hydrothermal fluid circulating during the flare up of magmatism in south china with lower temperature meteoric water

rapid disintegration of alpine glaciers observed with satellite data analyses of multispectral satellite data indicate accelerated glacier decline around the globe since the 1980s by using digitized glacier outlines inferred from the 1973 inventory and landsat thematic mapper tm satellite data from 1985 to 1999 we obtained area changes of about 930 alpine glaciers the 18 area reduction as observed for the period 1985 to 1999 1 3 a corresponds to a seven times higher loss rate compared to the 1850 1973 decadal mean extrapolation of area change rates and cumulative mass balances to all alpine glaciers yields a corresponding volume loss of about 25 km since 1973 highly individual and non uniform changes in glacier geometry disintegration indicate a massive down wasting rather than a dynamic response to a changed climate our results imply stronger ongoing glacier retreat than assumed so far and a probable further enhancement of glacier disintegration by positive feedbacks

new insights into phanerozoic tectonics of south china early paleozoic sinistral and triassic dextral transpression in the east wuyishan and chencai domains ne cathaysia the northeast cathaysia area is characterized by an archetypical transpressional system with widespread strike slip shear zones whose geometries kinematics and ages are critical for deciphering the phanerozoic tectonic evolution of south china we present new structural geochronological and thermochronological data from the shear zones in the east wuyishan and chencai domains which record two phases of deformation the first phase corresponds to sinistral oblique shearing along arrays of nne oriented steep dipping zones under amphibolite facies conditions the sinistral oblique shearing commenced at 451 ma concurrently with regional nw se directed thrust shearing and folding the coexistence of sinistral and thrust structures indicates nw se transpressive shortening deformation dating by 40ar 39ar shows that such deformation terminated before 400 ma and was followed by cooling through 450 350 c at 400 370 ma our results merged with published data aid in tracing an early paleozoic orogen that extends through the jiangnan domain into the northeast cathaysia with the southeast yangtze acting as a foreland belt the synorogenic shortening was interpreted as resulting from underthrusting of the cathaysia beneath the east yangtze the second phase involved dextral oblique shearing associated with nne ssw transpression under greenschist to amphibolite facies conditions at 245 228 ma which was followed by postkinematic magmatism and cooling at 221 200 ma in the cathaysia similar middle triassic dextral shear zones were widespread and operated with approximately east striking thrusts as mutually complementary structures their kinematic coupling can be explained by a contractional termination model geodynamically we attributed middle triassic dextral transpression to the collisions of south china with north china and indochina

recent changes in glacier area and volume within the southern canadian cordillera net changes in glacier area in the region 50 518 n 116 1258 w which includes the columbia and rocky mountains 1951 52 2001 and the coast mountains 1964 65 2002 were determined through a comparison of historic aerial photography and contemporary landsat 7 etm imagery the volumes of individual glaciers were estimated using an empirical volume area scaling relationship the area of glaciers in the coast mountains decreased by 120 10 km 2 or 5 of the initial ice covered area here the areas of glaciers in the columbia and rocky mountains decreased by 20 and 6k m 2 respectively corresponding to relative changes in total area of 5 and 15 the estimated total ice volume loss from the whole region was 13 3k m 3 in all parts of the study area the relative changes in area of individual glaciers showed considerable variability while the smallest glaciers remained essentially unchanged this suggests that local factors unique to individual glaciers largely determine their sensitivity to climatic change and that the very small glaciers are collectively less sensitive to such change

mass balance of glaciers other than the ice sheets small glaciers appear to have been at equilibrium or shrinking very slightly during 1961 90 according to analysis of an essentially compl ete set of published measurements simple calculations give an average annual mass balance of 195 59 mm a 1 water equivalent but this is too low because of systema tic errors eglect of internal accumulation is respon sible for some tens of millime ters of under esti mate uneven spatial coverage with fewer measurements where mass balances are less negative accounts for about 50 mm a 1 of underestimate this figure derives from spatial interpolati on based on global data on ice extent and on an analysis of correlations between balance time series the eorrelogram shows exponential decay the scale length being about 600 km the largest bias is due to a newly detec ted dependence of mass balance on glacier size among the 231 measured glaciers many arc small and belong to a restricted size range in which balance is negativ e but much of the small glacier extent is accounted for by larger glac iers in a size range where balance is indisti ngui shable from zero correct ing for this size bias increases the average balance to 35 89 mm a i inspection of time series for 1940 95 251 glaciers shows that mass balance was least negative during the 1960s and has varied in broad agreementvith northern hemisphere temperature anomalies smaller small glaciers a 16 km2 appear to be more sensitive than larger small glaciers to changes in thermal forci ng the small glaci er contribution to sea level rise implied by this asse ssment is only 0 06 0 32 mm a i consistent with glaciers in general mak i ng little or no contri bution to sea level change during 1961 90

middle to late jurassic felsic and mafic magmatism in southern hunan province southeast china implications for a continental arc to rifting abstract extensive middle to late jurassic felsic and mafic magmatism occurred in the southern hunan province southeast china shrimp zircon u pb dating mineral chemical element geochemical and sr nd hf isotopic data have been determined for these rocks the results indicate that the middle jurassic 178 170 ma changchengling and ningyuan basaltic rocks belong to tholeiitic series and alkaline series respectively and were formed by fractional crystallization of the parent magmas that were derived from partial melting of asthenospheric mantle triggered by the slab released fluids of the subducted paleo pacific plate the late jurassic 152 146 ma daoxian basalts and guiyang lamprophyre dikes are low ti high mg potassic rocks they were derived directly by partial melting of shallower 60 100 km lithospheric mantle composed of amphibole and phlogopite bearing lherzolite in response to thermal perturbations associated with the rifting of continental arc the middle jurassic 164 ma tongshanling granitic rocks belong to calc alkaline series and are strongly peraluminous they were formed by partial melting of palaeoproterozoic metasedimentary basement in the lower crust plus additional input from coeval basaltic magma the late jurassic 156 ma jinjiling and xishan granitic rocks show a2 subtype affinity they were generated by partial melting of granulitized palaeoproterozoic metamorphic basement in the lower crust in response to injection of coeval low ti high mg potassic magmas a moderate degree 56 58 of fractionation of these pure crustal melts could account for more felsic end member of granitic rocks detailed petrologic and geochemical data for the middle to late jurassic felsic and mafic rocks from the southern hunan imply that during the middle jurassic time se china on the southeast of the shi hang zone was a continental arc coupled with the subduction of the palaeo pacific plate and since the beginning of late jurassic time an intra arc rift has been formed along the shi hang zone as a consequence of slab roll back

an early cretaceous carbonate replacement origin for the xinqiao stratabound massive sulfide deposit middle lower yangtze metallogenic belt china stratabound massive sulfide deposits are widespread along the middle lower yangtze metallogenic belt mlymb and serve as an important copper producer in china two contrasting genetic models have been proposed interpreting the stratabound massive sulfide deposits as a carboniferous sedex protore overprinted by cretaceous magmatic hydrothermal system or an early cretaceous carbonate replacement deposit these two contrasting models have been applied to the xinqiao stratabound cu au sulfide deposit which is dominated by massive sulfide ores hosted in marine carbonates of the carboniferous chuanshan and huanglong formations with minor cu au skarn ores localized in the contact zone between the cretaceous diorite jitou stock and the carboniferous carbonate rocks new sims zircon u pb dating suggests that the jitou stock formed at 138 5 1 1 ma 2 mswd 0 6 pyrite re os dating yields an imprecise date of 142 47 ma 2 mswd 7 8 the geochronological data thus constrain the mineralization of the xinqiao deposit at early cretaceous fluid inclusions in prograde skarn diopside have homogenization temperatures of 450 600 c and calculated salinities of 13 58 wt nacl equiv quartz from the stratabound ores and pyrite quartz vein networks beneath the stratabound ores have homogenization temperatures of 290 360 and 200 300 c with calculated salinities of 5 12 and 2 10 wt nacl equiv respectively quartz from the skarn ores and veins beneath the stratabound ores have 18o values of 12 32 0 55 2 sd n 22 and 15 57 1 92 2 sd n 60 respectively corresponding to calculated 18o values of 6 22 1 59 2 and 6 81 2 76 2 for the equilibrated ore forming fluids the fluid inclusion and oxygen isotope data thus support a magmatic hydrothermal origin rather than a sedex system for the stratabound ores with the hydrothermal fluids most likely being derived from the jitou stock or associated concealed intrusion results from this study have broad implications for the genesis and exploration of other stratabound massive sulfide deposits along the mlymb

insights into the genesis of orogenic gold deposits from the zhengchong gold field northeastern hunan province china abstract the zhengchong gold deposit is located in the central jiangnan orogen belt where gold ore occurs mainly as quartz veins altered slates and minor breccias hosted by shear zones in the lengjiaxi group based on its vein crosscutting relationships mineral assemblages and paragenetic sequences mineralization in this deposit is divided into four stages stage 1 quartz q1 pyrite stage stage 2 quartz q2 pyrite arsenopyrite stage stage 3 quartz q3 pyrite polymetallic sulfide mineral stage and stage 4 quartz q4 carbonate stage two types of fluid inclusions have been recognized in the quartz grains co2 bearing fluid inclusions c type and aqueous fluid inclusions w type fluid inclusions in hydrothermal quartz yield homogeneous temperatures and salinities of 312 406 c and 4 65 9 21 wt naclequiv stage 1 252 324 c and 2 20 8 10 wt naclequiv stage 2 193 296 c and 2 24 14 04 wt naclequiv stage 3 and 127 209 c and 2 57 6 59 wt naclequiv stage 4 the co occurrence of these inclusion types despite their variable fluid salinities can be explained by fluid boiling during stages 2 and 3 of mineralization possibly as a result of episodic pressure decreases linked to fault valve activity laser raman spectroscopic analysis results reveal that small quantities of ch4 and n2 are present in the stage 2 3 fluid inclusions fluid inclusion data and microthermometric results show that the ore fluids were low salinity and co2 rich yielding both co2 inclusions c type and aqueous inclusions w type the trapping pressures estimated from the c type inclusions are 80 180 mpa for stages 2 and 3 yielding gold mineralization depths of 7 8 km the mineralizing fluids had calculated 18oh2o values ranging from 3 7 to 8 2 and d values from 75 2 to 61 8 indicating derivation mainly from metamorphic fluids the sulfide minerals yield 34s values of 8 9 to 0 1 and 206pb 204pb 207pb 204pb and 208pb 204pb ratios of 17 83 18 12 15 67 15 76 and 38 03 38 62 respectively which differ significantly from the isotopic composition of the granodiorite 34s 2 4 to 1 0 206pb 204pb 18 57 19 28 207pb 204pb 15 69 15 76 208pb 204pb 38 97 40 34 however the s pb isotopic compositions of the sulfide minerals are similar to those of slates of the lengjiaxi group in the study area the zhengchong gold deposit probably originated from a metamorphic fluid system characterized by low salinity low density and co2 enrichment with limited admixture of magmatic fluids based on similarities to other orogenic gold deposits we infer that the zhengchong orebody represents an orogenic gold deposit formed during the late ordovician jiangnan orogeny caused by collision of the yangtze and cathaysia blocks

assessing linkages between spatial facies changes and dimensional variations of glaciers in the upper indus basin western himalaya abstract the present study provides an insight into the heterogeneous response of 45 glaciers in the lidder and sindh river basins western himalaya and explores the linkages between glacier facies variability and changing glacier parameters results show that the region has undergone an overall deglaciation of 12 1 5 11 9 1 4 km 2 from 1996 to 2014 fluctuations in the temperature and precipitation patterns seem to be the primary factor controlling the changes in glacier dimensions r 2 0 82 in all cases glacier facies changes suggest depletion in snow ice cover 18 2 3 and an increase in ice mixed debris 4 1 4 supraglacial debris 6 1 5 and periglacial debris 17 1 2 these glacier facies transitions are possibly the result of ice melting however its relative rate and elevation decides the nature of facies conversion an increase in the proportion of supraglacial debris has led to the conversion of 11 clean glaciers to sparsely debris covered glaciers and 5 sparsely debris covered glaciers to debris covered glaciers the size of the glaciers greatly influenced the rate of conversion of glaciers and glaciers 2 dominated the others in this regard the small glaciers also experienced maximum shrinkage further the glaciers with varying supraglacial debris cover respond differently as sparsely debris covered glaciers exhibit the highest rates of retreat 25 7 3 m y followed by clean 23 7 7 3 m y and debris covered glaciers 13 1 7 3 m y thus the findings of this work clearly show that the climate change driven dimensional changes of glaciers and variations in the spatial distribution of glacier facies have strong mutual control on each other

changes in clemenceau icefield and chaba group glaciers canada related to hypsometry tributary detachment length slope and area aspect relations we compiled a detailed glacier inventory of 176 glaciers in the clemenceau icefield group cig and adjacent chaba group ch canada based on 2001 landsat 7 and 2000 03 aster satellite imagery and natural resources canada digital elevation models we used this inventory to measure length and mass balance changes and their possible controls a classification of glacier hypsometry in the form of a hypsometric index was used to assess the sensitivity of different glacier systems to a unit rise in snowline the altitude and aar of possible steady state elas was derived using several methods and was compared to late summer snowlines of 2001 we further compared planar glacier area to slope corrected area and compared the effects on the shape of the hypsometric curves on the total glacier area and on the aspect area distribution in 2001 cig had a glaciated area of 271 km 2 and had lost 42 km 2 since the mid 1980s ch had a total area of 69 km 2 and had lost 28 km 2 average retreat rates are 14 m a 1 for the period 1850 2001 n 39 and 21 m a 1 for 1986 87 2001 n 23 indicating accelerated retreat larger glaciers and those that experience tributary detachment tend to retreat faster the difference between planar and slope corrected glacier areas ranges from 5 to 20 with a 6 increase for the entire cig ch region the area increase does not change the shape of the hypsometric curves

ore forming epoch of gold deposits in northeastern hunan gold deposits in northeastern hunan are mainly hosted in epimetamorphic clastic rocks of middle proterozoic lengjiaxi group it was thought by some earlier researchers that gold mineralization took place in caledonian or yanshanian epoch which however was not supported by high quality age data in this paper the rb sr isochron of fluid inclusions trapped in quartz was used to date the ore forming epochs of gold deposits the huangjindong wangu and tuanshanbei gold deposits are dated at 462 18 ma mswd 1 6 425 33 ma mswd 0 14 and 222 4 9 4 ma mswd 2 6 respectively with 87sr 86sr i being 0 7589 0 0005 0 7517 0 0004 and 0 7335 0 0009 dating results show that gold mineralization in northeastern hunan mainly occurred in caledonian with indosinian probably being the other metallogenic epoch in addition gold ore forming epochs of western hunan and northeastern hunan were likely concentrated in caledonian and indosinian implying that caledonian and indosinian were the two main ore forming epochs in jiangnan terrain

fluid zircon interaction during low temperature hydrothermal processes implications for the genesis of the banxi antimony deposit south china abstract fluid zircon interaction in hydrothermal systems may provide key information on fluid characterization and ore precipitation in this study in situ analyses of hf isotopes in zircon combined with u pb ages and major and trace element data provide new insights into fluid genesis at the banxi antimony deposit the zircons separated from typical quartz stibnite ores and altered wall rocks have undergone fluid modification to different degrees showing hydrothermal overprints in reflected transmitted light back scattered electron bse and cathodoluminescence cl images and variable concentrations of si zr hf u th pb ti nb ta p f y and rare earth elements they possess identical u pb ages to the banxi group and underlying lengjiaxi group clastic rocks but distinct 176hf 177hf 176lu 177hf and 176yb 177hf ratios indicating the possible changing of lu hf systematics during the hydrothermal alteration the evidence suggests a contribution of ore material from the banxi group and a deeper fluid source derived from the lengjiaxi group and the crystalline basement beneath it a fluid mixing model is proposed wherein the deep sourced high radiogenic hf fluid mixed with circulating near surface meteoric component dominated fluid triggering antimony precipitation the u pb chronometer was not reset during this low temperature mineralization event whereas the lu hf systematics in the fluid altered zircons show evidence of lattice breakdown of the old zircons during fluid mixing coupled with external input of highly radiogenic hf from the crystalline basement this research highlights the potential to use zircon structure and geochemistry in tracing complex fluid evolutionary processes

application of arsenopyrite geothermometry and sphalerite geobarometry to the taebaek pb zn ag deposit at yeonhwa i mine republic of korea the taebaek pb zn ag deposit of the yeonhwa i mine republic of korea occurs in a broadly folded and reverse faulted terrain of paleozoic sedimentary rocks the taebaeksan basin the orebodies consist of several thin tabular orebodies of hydrothermal replacement type where they are hosted by carbonate rocks the pb zn ag mineralization can be divided into four distinct stages based upon the mode of occurrence of ore minerals ore textural relationships and their composition based on temperatures inferred from arsenopyrite compositions by means of electron microprobe and fluid inclusions the estimated temperatures for the stages i ii iii and iv reach 330 to 350 c 270 to 340 c 230 to 250 c and 220 c respectively the sulphur activity atm of ore formation at the taebaek deposit was estimated for each stage as 10 11 to 10 11 5 10 9 5 to 10 13 10 13 5 to 10 15 and 10 15 respectively even though application of sphalerite geobarometry is problematic because of the absence of good mineral assemblages sphalerite coexisting with pyrite but not with pyrrhotite was used to estimate the minimum mineralization pressure about 1 kbar

formation of the campbell red lake gold deposit by h 2 o poor co 2 dominated fluids the campbell red lake gold deposit in the red lake greenstone belt with a total of approximately 840 t of gold past production reserves and an average grade of 21 g t au is one of the largest and richest archean gold deposits in canada gold mineralization is mainly associated with silicification and arsenopyrite that replace carbonate veins breccias and wallrock selvages the carbonate veins and breccias which are composed of ankerite quartz and characterized by crustiform cockade textures were formed before and or in the early stage of penetrative ductile deformation whereas silicification arsenopyrite replacement and gold mineralization were coeval with deformation microthermometry and laser raman spectroscopy indicate that fluid inclusions in ankerite and associated quartz q1 and main ore stage quartz q2 are predominantly carbonic composed mainly of co2 with minor ch4 and n2 aqueous and aqueous carbonic inclusions are extremely rare in both ankerite and quartz h2o was not detected by laser raman spectroscopic analyses of individual carbonic inclusions and by gas chromatographic analyses of bulk samples of ankerite and main ore stage quartz q2 fluid inclusions in post mineralization quartz q3 are also mainly carbonic but proportions of aqueous and aqueous carbonic inclusions are present trace amounts of h2s were detected by laser raman spectroscopy in some carbonic inclusions in q2 and q3 and by gas chromatographic analyses of bulk samples of ankerite and q2 3he 4he ratios of bulk fluid inclusions range from 0 008 to 0 016 ra in samples of arsenopyrite and gold homogenization temperatures th co2 of carbonic inclusions are highly variable from 4 1 to 30 4 c mostly to liquid some to vapor but the spreads within individual fluid inclusion assemblages fias are relatively small within 0 5 to 10 3 c carbonic inclusions occur both in fias with narrow th co2 ranges and in those with relatively large th co2 variations the predominance of carbonic fluid inclusions has been previously reported in a few other gold deposits and its significance for gold metallogeny has been debated some authors have proposed that formation of the carbonic fluid inclusions and their predominance is due to post trapping leakage of water from aqueous carbonic inclusions h2o leakage model whereas others have proposed that they reflect preferential trapping of the co2 dominated vapor in an immiscible aqueous carbonic mixture fluid unmixing model or represent an unusually h2o poor co2 dominated fluid single carbonic fluid model based on the fia analysis reported in this study we argue that although post trapping modifications and host mineral deformation may have altered the fluid inclusions in varying degrees these processes were not solely responsible for the formation of the carbonic inclusions the single carbonic fluid model best explains the extreme rarity of aqueous inclusions but lacks the support of experimental data that might indicate the viability of significant transport of silica and gold in a carbonic fluid in contrast the weakness of the unmixing model is that it lacks unequivocal petrographic evidence of phase separation if the unmixing model were to be applied the fluid prior to unmixing would have to be much more enriched in carbonic species and poorer in water than in most orogenic gold deposits in order to explain the predominance of carbonic inclusions the h2o poor co2 dominated fluid may have been the product of high grade metamorphism or early degassing of magmatic intrusions or could have resulted from the accumulation of vapor produced by phase separation external to the site of mineralization

transport of passive tracers in baroclinic wave life cycles abstract the transport of passive tracers in idealized baroclinic wave life cycles is studied using output from the national center for atmospheric research community climate model ccm2 two life cycles lcn and lcs are simulated starting with baroclinically unstable initial conditions similar to those used by thorncroft et al in their study of two life cycle paradigms the two life cycles lcn and lcs have different initial horizontal wind shear structures that result in distinctive nonlinear development in terms of potential vorticity potential temperature pv theta diagnostics the lcn case is characterized by thinning troughs that are advected anticyclonically and equatorward while the lcs case has broadening troughs that wrap up cyclonically and poleward four idealized passive tracers are included in the model to be advected by the semi lagrangian transport scheme of the ccm2 and their evolutions are investigated throughout the life cycles tracer budgets are analyzed in terms of the transfo

ore forming fluids in archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec canada archean gold bearing quartz veins at the sigma mine occur in deformed metavolcanics intruded by two generations of preore porphyries the veins were emplaced during a late compressional tectonic event and they consist primarily of quartz tourmaline carbonates pyrite and scheelite vein minerals have been deformed and are also cut by abundant healed fractures outlined by fluid inclusions in the veins gold typically occurs in late fractures and in recrystallized quartz microthermometric sem eda leachate analysis and gas chromatographic techniques were used to study fluid inclusions in quartz most fluid inclusions at sigma occur in late fractures and are secondary the fluid inclusions are commonly found in fractures parallel to or less commonly within gold bearing fractures and are genetically related to the gold three types of fluid inclusions are identified 1 high salinity na ca cl aqueous inclusions 25 34 wt salt with small amounts of co 2 some containing halite calcite and nahcolite as daughter minerals 2 co 2 rich inclusions containing small amounts of h 2 o and ch 4 and 3 low salinity h 2 o co 2 inclusions 10 equiv wt nacl with co 2 contents which are variable but commonly in the range of 15 to 30 mole percent co 2 leachate analyses show that in addition to na and ca the aqueous fluids contain minor amounts of k fe mg and li homogenization temperatures of h 2 o co 2 inclusions with constant phase ratios range from 285 degrees to 395 degrees c those of aqueous inclusions range from 60 degrees to 295 degrees c the aqueous and co 2 rich inclusions are interpreted to have trapped two coexisting fluids resulting from the unmixing of a homogeneous h 2 o co 2 parent fluid itself occasionally trapped in late fractures the ore bearing fluid is interpreted to be a low salinity 10 equiv wt nacl fluid containing 15 to 30 mole percent co 2 at minimum temperatures in the range of 285 degrees to 395 degrees c the relatively low homogenization temperatures of aqueous inclusions are interpreted to be the result of co 2 effervescence from a co 2 saturated aqueous fluid due to pressure fluctuations at the time of entrapment it is also proposed that the onset of gold deposition is related to the onset of fluid unmixing

oceanic restratification forced by surface frontogenesis potential vorticity pv conservation implies a strong constraint on the time evolution of the mean density at a given depth the authors show that on an f plane and in the absence of sources and sinks of pv it only depends on two terms namely the time evolution of the product between density anomaly and relative vorticity and the vertical pv flux this primitive equation result which applies at any depth suggests that the ageostrophic dynamics induced by baroclinic eddies strongly affect the mean oceanic stratification profile this result is illustrated for two simple initial value simulations of a baroclinic balanced jet for initial situations propitious to surface frontogenesis the simulations show a restratification over the whole water column characterized by the amplification in time of the brunt vaisala frequency in the upper oceanic layers in the absence of surface frontogenesis such as when the jet is initialized at the middepth of the water column the restratification is much weaker and slower because both simulations have similar kinetic energy and growth rate of baroclinic instability the results clearly reveal that the restratification is driven by surface frontogenesis in the first case and by vertical pv flux in the interior in the second case the authors also point out that the dynamics of the interior pv is tightly related to the surface dynamics because of total mass conservation

arsenopyrite compositional variation over variable temperatures of mineralization otago schist new zealand compositions of arsenopyrite coexisting with pyrite from eight different mesothermal gold bearing systems in the otago schist fall mainly into a narrow band of 30 or 1 at percent as intragrain and intergrain compositional variations combined with analytical uncertainty preclude resolution of differences in arsenopyrite compositions between samples of less than 1 at percent as only one of the vein systems has an arsenopyrite compositional range that extends below 28 at percent as arsenopyrite from a pyrrhotite bearing assemblage has compositional range extending above 32 at percent as the vein systems have formed over a wide range of temperatures between about 200 degrees and 400 degrees c it is not possible to resolve the influence of temperature on arsenopyrite compositions for most samples sulfur and oxygen activity of the hydrothermal fluid may be responsible for the low degree of arsenopyrite compositional variation

synchronous vertical and horizontal tectonism at late stages of archean cratonization and genesis of hemlo gold deposit superior craton ontario canada the hemlo gold deposit 700 t au northwestern ontario canada is hosted in a shear zone in the hemlo greenstone belt which is a synclinal keel between two granitoid domes the dome and keel structure formed by diapirism and sagduction vertical tectonism that was synchronous with regional horizontal shearing horizontal tectonism mineralization occurred during shearing and mineralizing fluids probably had a magmatic source that is interpreted to be related to syntectonic mantle derived granodiorite sanukitoid intrusions the gold deposit the intrusions and the hosting shear zone all developed within a regime characterized by synchronous vertical and horizontal tectonism they were all possibly linked to a range of processes associated with the accretionary growth and stabilization of the craton in particular slab breakoff and the associated extensional orogenic collapse following terrane accretion

the use of hypsometry to indicate long term stability and response of valley glaciers to changes in mass transfer a simple equation is derived relating the net mass balance and hypsometric curves of a steady state valley glacier it is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions examples are given which show that area based indices e g aar for estimating the equilibrium line altitude ela may be subject to a substantial built in variance because they implicitly rely upon similarity of glacier shape and regimen over a region if accurate topographic maps are available the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass balance gradients alternatively if similar information is available concerning regional glacier regimen disparate extents and responses may be collectively utilized to estimate values of ela or to infer climatic influence taking glacier hypsometry into account

sustained rapid shrinkage of yukon glaciers since the 1957 1958 international geophysical year 1 glaciers in the yukon nw canada lost 22 of their surface area during the 50 years following the 1957 58 international geophysical year coincident with increases in average winter and summer air temperatures and decreases in winter precipitation scaling these results to ice volume change we obtain a total mass loss of 406 177 gt which accounts for 1 12 0 49 mm of global sea level rise yukon glaciers thinned by 0 78 0 34 m yr 1 water equivalent a regional thinning rate exceeded only by mountain glaciers in patagonia and alaska our scaling analysis suggests the remaining glaciers have the capacity to contribute a further 5 02 mm to global sea level rise

topographic influences on recent changes of very small glaciers in the monashee mountains british columbia canada an analysis of the local topographic setting of very small 0 4 km 2 glaciers within a small region of the monashee mountains british columbia was conducted to investigate its influence on recent changes in the extent of these glaciers net changes in glacier extent were determined from a detailed manual comparison of remotely sensed imagery acquired in 1951 2001 and 2004 most of the 86 glaciers included in the study showed no observable net change in area over the study period while six glaciers retreated four disappeared entirely and only one advanced indices derived to characterize elements of the local topographic setting that might affect the local mass balance suggest that most of the glaciers are situated in locations that favor ice preservation by enhancing mass input and or reducing ablation rates glaciers situated in less favorable settings generally either decreased in area or disappeared the results suggest that most of the glaciers studied have retreated as far as they are likely to under the climatic conditions of the late 20th century

phanerozoic tectonothermal events of the xuefengshan belt central south china implications from upb age and luhf determinations of granites the xuefengshan belt characterized by large scale fold and thrust structures and widespread granites is a key area to decipher the tectonic evolution of the south china block in this belt two magmatic episodes are recorded by early paleozoic and early mesozoic granites in this paper we carried out precise sims zircon usingle bondpb dating and in situ lusingle bondhf isotopes measurements on these granitic plutons our study indicates that the early paleozoic and the early mesozoic granites are late orogenic products of the early paleozoic orogen and the middle triassic xuefengshan orogen respectively in the xuefengshan belt the early paleozoic event is poorly registered since this area corresponds to the outer zone of the early paleozoic orogen the silurian early devonian granites are late orogenic plutons emplaced after the main tectonic and metamorphic stage in the wuyi baiyun yunkai belt coeval with a widespread subsequent extensional event in eastern and southern south china on the other hand triassic granites are formed in an intracontinental environment with weakly to strongly peraluminous signatures zircon usingle bondpb ages presented here associated with a summary of newly acquired data in the same region suggest that the emplacement of anatectic granites occurred around 225 215 ma not in a rather wide range of ca 245 200 ma in situ zircon ehf t values indicate a crust derived source without a mantle derived input for the two generations of granites combining our data with recent studies we infer that the central area of the south china block has experienced two tectonothermal events the early paleozoic magmatism developed as a result of the collapse of the early paleozoic orogen while these early mesozoic granites can be the late orogenic products of the intracontinental xuefengshan orogen most likely manifesting the far field effect by the

late neoproterozoic early paleozoic evolution of the south china block as a retroarc thrust wedge foreland basin system the early paleozoic wuyi yunkai fold belt of south china represents a major orogenic belt in east asia however its formation is not well understood this paper evaluates the origins of the neoproterozoic early paleozoic basin and the southern margin of the south china block scb based on a compilation of the spatiotemporal evolution of the late neoproterozoic early paleozoic strata and their depositional environments these data are combined with high resolution structural geochronologic metamorphic and petrologic data that are published from the region a new model of a retroarc thrust wedge foreland basin system is proposed for the succession based on the following 1 the nature of the basal unconformity 2 the wedge shaped basin fill geometry bounded by the mountain belt to the south 3 basinward propagation of the thrust front with time and 4 the presence of a typical underfilled stratigraphic trinity of the foreland basin the proposed model suggests two major cycles of evolution of the retroarc thrust wedge foreland basin system 725 635 and ca 564 446 ma which record two periods of northwestward subduction of the oceanic slab beneath the southern margin of the scb terrane accretion is inferred to have taken place during the late stage of these cycles

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

neoproterozoic to early paleozoic polyorogenic deformation in the southeastern margin of the yangtze block constraints from structural analysis and 40ar 39ar geochronology abstract the southeastern margin of the yangtze block is a suitable region to decipher neoproterozoic to early paleozoic polyorogenic deformation of the south china block based on 1 50 000 scale geological mapping four deformational phases were identified through structural analysis and 40 ar 39 ar dating the earliest event d 1 corresponds to nearly e w striking folding and top to the south thrusting developed during neoproterozoic orogeny caused by the collision between the yangtze block and the cathaysia block the d 2 event is characterized by the nearly e w striking top to the north thrusting the d 3 deformation is marked by the nne striking folding thrusting and dextral shearing the d 3 structures constitute a positive flower pattern with opposing kinematics rooted in the jiangwan dextral shear zone the d 4 event is the nearly e w striking ductile dextral shearing 40 ar 39 ar geochronology shows that the nne trending dextral shearing and the nearly e w striking dextral shearing occurred at 449 4 ma and 429 3 ma respectively combining with previous geochronology all the d 2 d 3 d 4 events are related to the early paleozoic orogeny both the d 2 top to the north thrusts and d 3 nne striking positive flower structures are syn orogenic products these incompatible syn orogenic structures indicate that the orientation of the principal stress changed from the n s striking to e w striking at 450 ma the nearly e w striking ductile dextral shearing d 4 is the outcome of post orogeny

the crustal continuum model for late archaean lode gold deposits of the yilgarn block western australia most archaean gold ores belong to a coherent genetic group of structurally controlled lode deposits that are characteristically enriched in au with variable enrichments in ag as w sb bi te b and pb but rarely cu or zn and are surrounded by wallrock alteration haloes enriched in k lile and co2 with variable na and or ca addition evidence from the yilgarn block of western australia combined with similar evidence from canada and elsewhere indicates that such deposits represent a crustal continuum that formed under a variety of crustal regimes over at least a 15 km crustal profile at pt conditions ranging from 180 c at 1 kb to 700 c at 5 kb individual deposits separated by tens to hundreds of kilometres collectively show transitional variations in structural style of mineralisation vein textures and mineralogy of wallrock alteration that relate to the pt conditions of their formation at varying crustal depths specific transitions within the total spectrum may be shown also by deposits within gold camps although nowhere is the entire continuum of deposits recorded from a single gold camp or even greenstone belt

the gold carbonate association source of co2 and co2 fixation reactions in archaean lode deposits abstract abundant carbonate is a ubiquitous feature of archaean lode gold deposits both in domains of alteration enveloping veins and in rocks enclosing auriferous sediments detailed studies of chemical mass balance in metabasalts progressively altered towards gold bearing quartz carbonate veins disposed within shear zones at yellowknife reveal massive additions of co2 k si and fe accompanying mineralisation with concomitant depletions of na coherent behaviour of al sc zr also v and nb provides a reference for constraining the volume relations during hydrothermal alteration in the peripheral regions of alteration depletions of ca and mg result in overall volume reduction but these elements are added to veins and their immediate alteration envelopes where there is a large positive volume change precious metals together with cr ni cu zn pb rb cd and ba have been added to the veins and altered wall rocks whereas quartz noble metals and other trace elements have been precipitated from hydrothermal fluids solution of ca mg and some fe indigenous to peripheral alteration regions combining with co2 from the mineralising reservoir appears to be the process for forming the abundant ferri dolomite gangue observations of many archaean au deposits reveals that carbonate chemistry reflects the nature of wall rocks with wall rocks donating the bivalent metal cations and hydrothermal fluids the co2 alteration reactions at yellowknife involved hydrolysis of albite accompanied by fixation of kaqueous to produce muscovite with na loss and hydrolysis of chlorite epidote with co2 fixation to form ferri dolomite studies of oxygen isotopes fe 2 fe 2 fe 3 and structure reveal that au quartz and carbonate were precipitated in the presence of fluids of probable metamorphic origin 18 o 8 9 at low redox potential and at ambient temperatures of 400 450 c during episodes of hydrofracturing the abundant co2 and k required for extensive carbonate muscovite replacement alteration could be supplied by fluids released during prograde metamorphism under greenschist or greenschist amphibolite facies conditions where the relative proportion of co 2 h 2 o is in the order of 0 2 to 0 5 and k na 1 given high co2 co in the hydrothermal reservoir these molecules may act as complexing agents for transport of au and other rare elements e g w pd ni cr