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

glacier area shrinkage in eastern nepal himalaya since 1992 using high resolution inventories from aerial photographs and alos satellite images to better understand the recent wide scale changes in glacier coverage we created and compared two glacier inventories covering eastern nepal based on aerial photographs 1992 and high resolution advanced land observing satellite alos imagery 2006 10 the alos derived inventory contained 1034 debris free and 256 debris covered glaciers with total and average areas of 440 2 33 3 and 0 42 km 2 and 1074 4 206 4 and 4 19 km 2 respectively we found that the debris free glaciers have lost 11 2 0 7 0 1 a 1 of their area since 1992 whereas the number of glaciers increased by 5 because of fragmentation the area change was significantly correlated by simple linear regression with minimum elevation r 0 30 maximum elevation r 0 18 altitudinal range r 0 50 glacier area r 0 62 and mean slope r 0 16 confirming that larger glaciers tended to lose a larger area but a smaller percentage than smaller glaciers the intra regional analysis of the glacier changes clearly showed higher shrinkage rates in the western massifs compared with the eastern massifs in addition 61 small glaciers covering an area of 2 4 km 2 have completely disappeared since 1992

glacier changes between 1971 and 2016 in the jankar chhu watershed lahaul himalaya india glacier changes in the jankar chhu watershed jcw of chandrabhaga chenab basin lahaul himalaya were worked out based on corona and sentinel 2a images between 1971 and 2016 the jcw consists of 153 glaciers 0 02 km 2 with a total area of 185 6 3 8 km 2 that include 82 glaciers with debris covered ablation zone comprising 10 9 of the total glacierized area as in 2016 change analysis based on corona 1971 landsat 2000 and sentinel 2a 2016 was restricted to 127 glaciers owing to the presence of cloud cover on 26 glaciers in 1971 a subset of glaciers was also mapped using landsat thematic mapper tm 1989 image the total glacier area decreased by 14 7 4 3 km 2 0 3 0 1 km 2 a the number of glaciers in the jcw increased by four between 1971 and 2016 due to fragmentation more recently 2000 16 recession rate has increased clean ice area decreased by 21 8 3 8 km 2 0 5 0 1 km 2 a while debris covered ice increased by 7 2 0 4 km 2 0 2 0 01 km 2 a field observations of select glaciers also support derived recession trend in the jcw retreat rates in the jcw have been observed to be much lower than previously reported

re os age of the pueblo viejo epithermal deposit dominican republic re os analyses of pyrite from the pueblo viejo high sulfidation epithermal deposit both monte negro and moore ore zones yield an isochron age of 111 9 3 7 ma and initial 187 os 188 os ratio of 0 22 0 18 mean square of weighted deviates 84 n 21 isochrons grouped by pyrite setting layered versus vein or locations yield ages within uncertainty of the overall isochron and with each other and as such do not yield temporally distinguishable ages sphalerite vein samples as well as shale source rocks show evidence of open system behavior and loss of re and therefore are not included in the above regression these results confirm that the pueblo viejo deposit is early cretaceous in age and coeval with the volcanic los ranchos formation which hosts the deposit recent paleontological age assignments for the hatillo formation which overlies the los ranchos formation show that it is only slightly younger opening the possibility that mineralization in the hatillo formation could also be related to late stages of los ranchos magmatism whether these revised los ranchos hatillo relations provide sufficient cover to account for the paragenetically late formation of pyrophyllite at pueblo viejo remains unclear recognition that pueblo viejo is coeval with the los ranchos formation shows that large scale high sulfidation epithermal mineralization can form from basal island arc tholeiitic magmatism a review of available experimental data confirms that these magmas can generate hydrothermal solutions of the necessary composition favorability of the los ranchos formation might have been enhanced by its bimodal composition these results suggest that exploration for epithermal precious metal deposits should include basal island arc tholeiite terranes

microgranular enclaves in island arc andesites a possible link between known epithermal au and potential porphyry cu au deposits in the tulasu ore cluster western tianshan xinjiang china abstract the successful exploration for porphyry copper deposit in western tianshan xinjiang faces great challenge tulasu basin is an important epithermal gold ore cluster in western tianshan which was formed in a southwest pacific type island arc setting during the late paleozoic by the southward subduction of the north tianshan ocean beneath the yili plate porphyry cu au deposits are possibly to be found at depth or adjacent to these epithermal gold deposits some sulfide mineralized microgranular enclaves of monzonite porphyry and microdiorite were found in andesites of the tawuerbieke gold district tulasu basin the enclaves are randomly distributed with generally round or subangular shape and commonly clearly defined within their host andesite and have a chilled surrounding margin of andesite the monzonite porphyry enclaves mpe exhibit porphyritic texture with the phenocrysts of plagioclase and k feldspar the microdiorite enclaves mde are mainly composed of plagioclase and hornblende with an aplitic texture and massive structure the host andesites show porphyritic texture with the phenocrysts major of plagioclase minor of hornblende and clinopyroxene the groundmass consists of short column plagioclase and minor clinopyroxene with a hyalopilitic texture zircon grains from a mpe sample yield a weighted 206pb 238u age of 356 2 4 3 ma n 13 mswd 1 11 which is effectively coincident with the 360 5 3 4 ma n 20 mswd 0 61 of an andesite sample within analytical error indicating that they were coeval in addition the mpe mde and the andesite samples share similar normalized incompatible element and rare earth element patterns that are characterized by a pronounced enrichment of large ion lithophile elements and a deficit of high field strength elements moreover the samples show similar nd isotope compositions to the contemporary andesites and basaltic andesites detailed petrology geochronology and geochemistry studies suggest that these enclaves were captured from an underlying body during the eruption of island arc magma thus unmapped cognate porphyry intrusions associated with cu au mineralization may exist under the andesite strata this evidence in combination with the low and high sulfidation epithermal gold deposits acidic hydrothermal alterations and copper mineralization evidence suggests that a porphyry epithermal cu au metallogenic system might occur in the tulasu basin of western tianshan and that the tawuerbieke district should be an important target for porphyry cu au exploration

re os geochronology of the hitachi volcanogenic massive sulfide deposit the oldest ore deposit in japan the hitachi volcanogenic massive sulfide vms deposit in the hitachi belt is one of the largest cu zn sulfide deposits in japan however its primary formation age has not been precisely determined because regional and contact metamorphism have disturbed some radiometric isotope systems e g k ar ages on wall rocks further metamorphism has greatly reduced the fossil record which has limited the use of biostratigraphy to establish the ore deposit age we applied re os isotope dating to samples from two representative sulfide deposits of the greater hitachi vms deposit the fudotaki and fujimi deposits re os isotope data from the fudotaki deposit yields a model 3 age of 533 13 ma with an initial 187 os 188 os ratio of 0 35 0 20 in contrast re os isotope data from the fujimi sulfide ore did not exhibit a linear correlation suggesting that the re os isotope system there has been disturbed by regional metamorphism of higher grade than the fudotaki deposit as well as contact metamorphism during intrusion of cretaceous granitic rocks although the fudotaki sulfide ores have been metamorphosed to lower epidote amphibolite facies the well defined re os isochron allowed us to interpret the timing of primary sulfide deposition on the paleoseafloor some orebodies of the greater hitachi vms deposit have been estimated to be early carboniferous based on the scarce fossil records and considered to be distributed in the daioin formation but our results revealed that the fudotaki deposit were formed during the cambrian and occurs in the upper akazawa formation which strongly supports the idea that the cambrian beds are widely distributed in the hitachi belt and that a significant unconformity exists between the cambrian and early carboniferous above the fudotaki deposit the cambrian re os date classifies the hitachi vms deposit as the oldest dated ore deposit in japan and in turn provides an insight to understand the geologic framework and genesis of the proto japanese islands and the east asian region

trace element systematics of pyrite from submarine hydrothermal vents abstract submarine hydrothermal sulfide ores occur at mid ocean ridges intra oceanic arcs and in back arc basins associated with host rocks of highly variable composition pyrite is the dominant sulfide mineral in most samples presented within this study and thus the trace element composition of pyrite may reflect the different metal sources and precipitation processes here we report on a systematic study of minor and trace element contents in pyrite from active and inactive submarine hydrothermal vent fields at different plate tectonic settings including the indian and mid atlantic ridges the tonga kermadec intra oceanic arc the lau back arc and the central okinawa trough our results show that the trace element contents of pyrite from different locations vary significantly but for most elements without any systematic correlation to the concentration in the magmatic host rocks only as appears to be depleted in pyrite from ultramafic hosted vent systems that are affected by serpentinization these as depleted pyrites preferentially host au 0 micro or nano particles bismuth is enriched in pyrite from hydrothermal systems that contain a sedimentary component and micro inclusions of sphalerite are either due to fluid sediment interaction or phase separated fluid venting pyrites from individual locations have highly variable concentrations of elements like au co cu se mo ag and sb that are most likely related to fluid evolution and changes in fluid composition sub seafloor hydrothermal fluid seawater mixing influences the distribution of au co cu se and mo in pyrite elements like au ag sb and pb often have a characteristic affinity to as while cd correlates closely with zn a magmatic volatile contribution to the hine hina hydrothermal system may result in the precipitation of cu enriched pyrite our results show that the concentrations of most trace metals in pyrite are a function of the physicochemical parameters of the fluid phase rather than a reflection of the magmatic host rock composition

epithermal au and polymetallic mineralization in the tulasu basin western tianshan nw china potential for the discovery of porphyry cuau deposits abstract the tulasu basin is an important epithermal au mineralization district in western tianshan in northwestern china geochemical and geochronological studies of the volcanic host rocks the dahalajunshan formation and associated intrusive rocks particularly the enrichment of large ion lithophile elements and depletion of high field strength elements suggest that the tulasu basin was located in a magmatic arc setting from late devonian to early carboniferous associated with the southward subduction of the north tianshan ocean beneath the kazakhstan yili plate geologic and geochemical characteristics of the au cu polymetallic deposits in the tulasu basin suggest that the mineralization is related to the late devonian to early carboniferous arc magmatism and is mainly of epithermal nature including both the adularia sericite type axi tawuerbieke and tabei and alunite kaolinite or acid sulfate type jingxi yelmend and tieliekesayi however some evidence of porphyry type mineralization has also been found including the presence of mineralized porphyry enclaves in volcanic rocks hosting the tawuerbieke au prospect and the development of porphyry style cu mineralization overprinted by vein type mineralization at kexiaxi considering the magmatic arc setting that is favorable for both epithermal and porphyry types of mineralization and the development of such mineralization systems in other parts of western tianshan and the altaid belt e g uzbekistan kazakhstan and kyrgyzstan we suggest that major porphyry cu au deposits may have been developed in the tulasu basin probably beneath or adjacent to known epithermal au mineralization

on the accuracy of glacier outlines derived from remote sensing data deriving glacier outlines from satellite data has become increasingly popular in the past decade in particular when glacier outlines are used as a base for change assessment it is important to know how accurate they are calculating the accuracy correctly is challenging as appropriate reference data e g from higher resolution sensors are seldom available moreover after the required manual correction of the raw outlines e g for debris cover such a comparison would only reveal the accuracy of the analyst rather than of the algorithm applied here we compare outlines for clean and debris covered glaciers as derived from single and multiple digitizing by different or the same analysts on very high 1 m and medium resolution 30 m remote sensing data against each other and to glacier outlines derived from automated classification of landsat thematic mapper data results show a high variability in the interpretation of debris covered glacier parts largely independent of the spatial resolution area differences were up to 30 and an overall good agreement for clean ice with sufficient contrast to the surrounding terrain differences 5 the differences of the automatically derived outlines from a reference value are as small as the standard deviation of the manual digitizations from several analysts based on these results we conclude that automated mapping of clean ice is preferable to manual digitization and recommend using the latter method only for required corrections of incorrectly mapped glacier parts e g debris cover shadow

challenges and recommendations in mapping of glacier parameters from space results of the 2008 global land ice measurements from space glims workshop boulder colorado usa on 16 18 june 2008 the us national snow and ice data center held a glims workshop in boulder co usa focusing on formulating procedures and best practices for operational glacier mapping using satellite imagery despite the progress made in recent years there still remain many cases where automatic delineation of glacier boundaries in satellite imagery is difficult error prone or time consuming this workshop identified six themes for consideration by focus groups 1 mapping clean ice and lakes 2 mapping ice divides 3 mapping debris covered glaciers 4 assessing changes in glacier area and elevation through comparisons with older data 5 digital elevation model dem generation from satellite stereo pairs and 6 accuracy and error analysis talks presented examples and work in progress for each of these topics and focus groups worked on compiling a summary of available algorithms and procedures to address and avoid identified hurdles special emphasis was given to establishing standard protocols for glacier delineation and analysis creating illustrated tutorials and providing source code for available methods this paper summarizes the major results of the 2008 glims workshop with an emphasis on definitions methods and recommendations for satellite data processing while the list of proposed methods and recommendations is not comprehensive and is still a work in progress our goal here is to provide a starting point for the glims regional centers as well as for the wider glaciological community in terms of documentation on possible pitfalls along with potential solutions

evaluating glacier dynamics using temporal remote sensing images a case study of hunza valley northern pakistan glaciers are the largest freshwater repository on the earth surface northern pakistan is covered with some of the largest midlatitude glaciers in the world most of the recent studies on the region lead to contradictory results that glaciers in the karakoram ranges have shown either advancement retreat or stable behaviors and therefore coin the term karakoram anomaly in the present study temporal landsat satellite images acquired in the years of 1977 1999 2001 2007 2009 and 2014 were used to evaluate the temporal dynamics of the selected glaciers in the hunza valley northern pakistan including the batura passu ghulkin and gulmit the glaciers outlines were extracted using ndsi and slope gradient followed by manual editing the landsat derived glacier inventories were verified through the fine resolution worldview 2 satellite image and field observations evaluating the temporal glacier inventories reveals that the selected glaciers are retreating however the melting rate is varying depending on the supra glacier debris cover the melting or advancing of glacier is also influenced by the mean annual temperature and precipitation records the study should assist in predicting the future climate of the region

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

compilation of a glacier inventory for the western himalayas from satellite data methods challenges and results abstract due to their sensitive reaction to changes in climatic conditions glaciers have been selected as an essential climate variable ecv although a large amount of ice is located in the himalayas this region is yet only sparsely represented in global glacier databases accordingly a sound and comprehensive change assessment or determination of water resources was not yet possible in this study we present a new glacier inventory for the western himalayas compiled from landsat etm scenes acquired between 2000 and 2002 coherence images from alos palsar image pairs the srtm digital elevation model dem and the aster global dem gdem several specific challenges for glacier mapping were found in this region and addressed they are related to debris cover orographic clouds locally variable snow conditions and creeping permafrost features in cold dry regions additional to seven topographic parameters that are obtained from the aster gdem for each glacier we also determined the relative amount of debris cover on the glacier surface the inventory contains 11 400 glaciers larger than 0 02 km2 which cover a total area of 9 310 km2 analysis of the inventory data revealed characteristic patterns of mean glacier elevation and relative debris cover amounts that might be related to the governing climatic conditions the full dataset will be freely available in the glims glacier database to foster further analyses and modeling of the glaciers in this region

effect of precipitation seasonality on climatic sensitivity of glacier mass balance abstract numerical calculations are described aimed at evaluating the influence of precipitation seasonality and seasonality concentration on climatic sensitivity of glacier mass balance equilibrium line altitudes elas are modeled using idealized meteorological variables and then a warming test 1 c is performed which revealed that the effects of latitude and the annual precipitation amount are less than those of precipitation seasonality and its concentration calculation shows higher sensitivities for the glaciers located in a summer precipitation climate than for those located within a winter precipitation climate difference due to seasonality is enhanced with the seasonality concentration the present study suggests that the earlier parameterization of glacier mass balance with annual precipitation amount is insufficient to describe the response of glaciers to climate change distribution of precipitation seasonality and its concentration suggest that many parts of the world have a summer precipitation climate but their seasonality concentration is not significant worldwide on the other hand an extensive region of asia and part of the andes are located in the highly concentrated summer precipitation climate this suggests the high sensitivity of glacier mass balance in these regions to climate change

genesis of the giant zijinshan epithermal cu au and luoboling porphyry cu mo deposits in the zijinshan ore district fujian province se china a multi isotope and trace element investigation abstract the zijinshan ore district occurs as one of the largest porphyry epithermal cu au mo ore systems in south china including the giant zijinshan epithermal cu au deposit and the large luoboling porphyry cu mo deposit the mineralization is intimately related to late mesozoic large scale tectono magmatic and hydrothermal events the cu au mo mineralization occurs around intermediate felsic volcanic rocks and hypabyssal porphyry intrusions in this study we summarize previously available re os isotopes zircon u pb age and trace elements and sr nd pb isotope data and present new pb s and re os isotope data and zircon trace elements data for ore related granitoids from the zijinshan high sulfidation epithermal cu au deposit and the luoboling porphyry cu mo deposit in an attempt to explore the relationship between the two ore systems for a better understanding of their geneses the ore bearing porphyritic dacite from the zijinshan deposit shows a zircon u pb age of 108 106 ma and has higher zircon ce4 ce3 ratios 92 1568 average 609 but lower ti in zircon temperatures 588 753 c average 666 c when compared with the barren intrusions in the zijinshan ore district relative to the zijinshan porphyritic dacite the ore bearing granodiorite porphyry from the luoboling deposit show a slightly younger zircon u pb age of 103 ma but has similar or even higher zircon ce4 ce3 ratios 213 2621 average 786 and similar ti in zircon temperatures 595 752 c average 675 c these data suggest that the ore bearing magmatic rocks crystallized from relatively oxidized and hydrous magmas combined with the high rhenium contents 78 6 451 ppm of molybdenites the pb and s isotopic compositions of magmatic feldspars and sulfides suggest that the porphyry and ore forming materials in the luoboling cu mo deposit mainly originated from an enriched mantle source in contrast the ore bearing porphyritic dacite in the zijinshan cu au deposit might be derived from crustal materials mixing with the cathaysia enriched mantle the fact that the zijinshan cu au deposit and the luoboling cu mo deposit show different origin of ore forming materials and slightly different metallogenic timing indicates that these two deposits may have been formed from two separate magmatic hydrothermal systems crustal materials might provide the dominant cu and au in the zijinshan epithermal deposit cu and au show vertical zoning and different fertility because the gold transports at low oxygen fugacity and precipitates during the decreasing of temperature pressure and changing of ph conditions it is suggested that there is a large cu mo potential for the deeper part of the zijinshan epithermal cu au deposit where further deep drilling and exploration are encouraged

osmium isotopes in hydrothermal fluids from the juan de fuca ridge we present os data for axial high temperature and off axial low temperature hydrothermal solutions from the juan de fuca ridge the high temperature h s bearing axial fluids have unradiogenic os isotopes pointing to a nearly complete domination of osmium isotopes from the basalts during hydrothermal circulation the ridge axis fluids typically do not show large enrichment in osmium concentration over seawater although one high temperature fluid has an os concentration enhanced by a factor of 4 above seawater it appears that the os concentration of high temperature hydrothermal fluids is typically buffered at roughly the seawater concentration we suggest that subseafloor precipitation of pyrite from the high temperature hydrothermal fluids controls the osmium transportation the axial hydrothermal activity does not supply significant amounts of unradiogenic osmium to the deep oceans in contrast a low temperature off axis fluid is enriched in non radiogenic osmium over seawater by a factor of 9 showing much less precipitation of osmium at low temperature because a large fraction of the cooling of oceanic lithosphere occurs on ridge flanks os from low temperature ridge flank hydrothermal circulation may be a significant contributor to the balance of os in the oceans a detailed balance between os contributions from dissolution of cosmic dust and hydrothermal fluids is still not possible the low temperature hydrothermal sample gives os os 0 110 0 001 this extremely unradiogenic osmium can only come from a source that underwent depletion of re over 2 6 ga ago assuming no contamination during sample collection this result suggests that the convecting upper mantle contains ancient depleted material that imparted unradiogenic osmium to intruding basaltic melts

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

perspectives on the production of a glacier inventory from multispectral satellite data in arctic canada cumberland peninsula baffin island the consequences of global warming on land ice masses are difficult to assess in detail as two dimensional glacier inventory data are still missing for many remote regions of the world as the largest future temperature increase is expected to occur at high latitudes the glaciers and ice caps in the arctic will be particularly susceptible to the expected warming this study demonstrates the possibilities of space borne glacier inventorying at a remote site on cumberland peninsula a part of baffin island in arctic canada thereby providing glacier inventory data for this region our approach combines landsat etm and terra aster satellite data an aster derived digital elevation model dem and geographic information system based processing we used thresholded ratio images from etm bands 3 and 5 and aster bands 3 and 4 for glacier mapping manual delineation of little ice age trimlines and moraines has been applied to calculate area changes for 225 glaciers yielding an average area loss of 11 a size distribution has been obtained for 770 glaciers that is very different from that for alpine glaciers numerous three dimensional glacier parameters were derived from the aster dem for a subset of 340 glaciers the amount of working time required for the processing has been tracked and resulted in 5 min per glacier or 7 years for all estimated 160 000 glaciers worldwide

diffusion of osmium in pyrrhotite and pyrite implications for closure of the re os isotopic system abstract in order to better constrain the extent to which common sulfide minerals will retain their osmium isotopic composition subsequent to crystallization we have conducted experiments to quantify the diffusion behavior of osmium in pyrite and pyrrhotite experiments consisted of either 1 isothermal soaking of diffusion couples consisting of natural pyrite or pyrrhotite crystals packed against powdered os bearing fe sulfide or 2 relaxation of initially high near surface osmium concentrations produced in the latter experiments pyrite only osmium penetration into samples was characterized by depth profiling using rutherford backscattering spectroscopy rbs pyrite or electron microprobe analyses across sectioned run products pyrrhotite results of the first type of diffusion experiment involving pyrite show only limited osmium penetration into sample surfaces with the extent of penetration uncorrelated with run duration images of pyrite samples using atomic force microscopy show roughening of initially smooth surfaces as a consequence of step formation and suggest that osmium incorporation into the near surface occurred by solute uptake during step growth and not by volume diffusion prolonged 1000 h relaxation experiments revealed no additional osmium penetration into pyrite surfaces and based on the depth resolution for rbs a maximum diffusion coefficient of 2 5 10 23 m2 s at 500 c was calculated experiments involving pyrrhotite over the temperature range of 950 1100 c showed extensive osmium uptake and osmium concentration gradients that conform with fickian diffusion behavior we found that pyrrhotite fe s could be varied by changes in the composition of the starting material and osmium source and over the range of fe s produced in experiments molar fe s 0 83 0 90 we observed no systematic variation in the osmium diffusion coefficient diffusion coefficients measured parallel to the a crystallographic axis were on average 1 4 higher than values measured parallel to c and regression of the c axis data yielded the arrhenius relation d t 1 31 0 16 10 5 m 2 s exp 211 5 14 7 kj mol rt the application of these diffusion data to simple models of diffusive exchange during static or polythermal time temperature histories is used to assess the conditions under which radiogenic osmium will be retained during isothermal annealing calculations indicate that the cores of millimeter sized spherical pyrrhotite crystals undergoing diffusive exchange with an external osmium reservoir will have their initial compositions perturbed in 0 5 ma at temperatures exceeding 400 c pyrite undergoing the same process at 500 c requires in excess of 10 ma before crystal cores are affected the relatively short core retention time scales for pyrrhotite indicates that this mineral may be prone to isotopic resetting following relatively brief crustal thermal events thus possibly accounting for the scatter that commonly occurs in re os isochrons generated from massive sulfide samples calculated closure temperatures tc for osmium exchange in pyrrhotite yielded values of 300 400 c for grain sizes ranging from 10 to 1000 m these values of tc are similar to those calculated for ar retention in biotite and considerably lower than for sr in apatite and plagioclase for example such low closure temperatures for pyrrhotite suggest this mineral will date the final stage in the cooling of a magmatic system and possibly be susceptible to open system osmium exchange in the presence of late stage hydrothermal fluids this latter result infers that caution be applied when interpreting elevated initial osmium isotopic ratios as a product of crustal assimilation at the magmatic stage

role of basement in epithermal deposits the kushikino and hishikari gold deposits southwestern japan abstract the magma ore deposit relationship of most low sulfidation epithermal ore deposits is still unclear partly because many stable isotopic studies of such deposits have indicated the predominance of meteoric waters within hydrothermal fluids however it is certainly true that hydrothermal systems are ultimately driven by magmatic intrusions and epithermal gold deposits might therefore be produced by magmatic activity even in deposits having has no obvious links to a magma we re examine the genesis of two typical low sulfidation epithermal gold deposits the kushikino and hishikari deposits using structural simulations and isotope data many epithermal gold deposits including the kushikino and hishikari deposits have been discovered in kyushu southwestern japan the kushikino deposit comprises fissure filling veins within neogene andesitic volcanics that overlie unconformably cretaceous sedimentary basement the veins consist of gold and silver bearing quartz and calcite with minor amounts of adularia sericite and sulfides although carbon and oxygen isotopic data for the veins indicate a meteoric origin of the ore fluid finite element simulations suggest that the vein system might have formed in direct response to magma intrusion in particular geophysical data suggest that intruding magma has uplifted the basement rocks thereby producing fractures and veins and a positive bouguer anomaly and providing the heat necessary to drive an ore forming hydrothermal system the second component of this study has been to investigate the nature and evolution of the kushikino and hishikari epithermal systems isotope data document the geochemical evolution of the hydrothermal fluids we conclude that the existence of sedimentary basement rocks at depth might have affected the strontium and carbon isotopic ratios of the kushikino and hishikari ore fluids the 87 sr 86 sr ratios and 13 c 18 o trend reveal that major ore veins in the hishikari deposit can be distinguished from shallow barren veins it was suggested isotopically that fluids responsible for the barren veins in nearby shallow and barren circulation systems were only controlled by the shallow host rocks such multi isotope systematics provide a powerful tool with which to determine the center of hydrothermal activity and thereby document the evolution of hydrothermal fluids

two stage gold mineralization of the axi epithermal au deposit western tianshan nw china evidence from re os dating s isotope and trace elements of pyrite the axi gold deposit is one of the largest epithermal deposits in northwestern china and is characterized by multistage generations of pyrite associated with gold mineralization genetic models for superjacent epithermal au and porphyry cu systems involve either contemporaneous or episodic mineralization implying different metal sources and ore forming events nine pyrite separates from disseminated ores associated with pyrite sericite quartz alteration in the axi deposit yield a re os isochron age of 350 10 ma mswd 5 1 initial 187os 188os ios 0 20 0 11 this age likely reflects a mixed contribution of two subtypes of disseminated pyrite py1 based on zoned pyrite crystals the isochron age of 353 6 ma mswd 1 6 ios 0 107 0 021 n 6 excluding samples with pyrite cores overlaps previous ages for andesite from the dahalajunshan formation ca 356 ma indicating that the early mineralization event occurred shortly after the formation of host rocks ca 353 ma pyrite from disseminated ores shows little variation of sulfur isotopic compositions 2 9 to 4 0 and has high cu co ni and v contents which favors a magmatic hydrothermal origin pyrite grains from gray quartz veins yield a younger re os isochron age of 332 8 ma mswd 0 22 n 4 vein hosted pyrite shows characteristics of a mantle derived magma source ios 0 171 0 024 34s 0 10 3 10 which result from the intrusion driven convective hydrothermal circulation accompanying fluid exsolution and metal remobilization from basement and wallrocks our data demonstrate that the axi gold deposit was formed during two temporally separated hydrothermal events this model of ore formation may apply to other epithermal porphyry deposits within the axi tawuerbieke district disseminated au and porphyry style au cu mineralization occurred shortly after magmatic activity 356 353 ma whereas epithermal style au mineralization occurred at ca 332 ma

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

evidence for magmatic hydrothermal fluids and ore forming processes in epithermal and porphyry deposits of the baguio district philippines the baguio district contains a diverse array of epithermal porphyry and skarn deposits together with a large broadly strata bound advanced argillic lithocap magmatism mineralization and alteration occurred in response to subduction of the south china sea plate and the scarborough ridge beneath northern luzon over the past 3 m y rapid uplift and exhumation resulted in epithermal veins overprinting several porphyry cu au deposits most of the epithermal au ag deposits of the baguio district including antamok and acupan the two largest au deposits are intermediate sulfidation state quartz carbonate adularia illite base metal sulfide veins that contain electrum and minor au ag tellurides in contrast high sulfidation mineralization at kelly includes enargite tennantite electrum and precious metal tellurides and is associated with advanced argillic alteration although the mineralizing fluids that formed the porphyry and epithermal deposits had distinct temperatures and salinities stable and radiogenic data provide evidence for direct magmatic contributions into each deposit type the epithermal mineralizing fluids were dilute generally 600 c hypersaline brines 30 to 70 wt nacl equiv and low density vapor sulfur isotope compositions of sulfides in the porphyry skarn and intermediate sulfidation epithermal veins of the southern and central baguio district are mostly between 1 and 6 per mil consistent with a predominance of h2s in the mineralizing fluids i e reducing conditions in contrast sulfides from the high sulfidation porphyry and intermediate sulfidation deposits located adjacent to the baguio lithocap mostly have negative sulfur isotope values 6 9 to 0 8 consistent with oxidizing so42 predominant mineralizing fluids intermediate sulfidation epithermal veins at acupan have crosscut a well mineralized porphyry cu au stock work at ampucao the two deposits cannot be distinguished on the basis of radiometric age determinations ampucao 0 51 0 26 ma acupan 0 65 0 07 ma and are interpreted to be cogenetic with telescoping of the two environments caused by the rapid uplift and exhumation associated with ridge subduction measured 34ssulfide 1 1 to 6 6 34ssulfate 10 4 to 31 8 values and initial strontium ratios of anhydrite 0 70378 0 70385 are consistent with identical and predominantly magmatic sources of these components for the ampucao porphyry and acupan epithermal veins helium isotopes provide further evidence of mantle derived components in the epithermal veins r ra values of 6 0 and 6 7 oxygen deuterium and carbon isotopes provide evidence for predominantly magmatic water at ampucao and for hybrid magmatic meteoric waters at acupan that precipitated precious metals due to boiling the proportion of magmatic water relative to meteoric water and precious metal grades both decreased with time during epithermal vein formation at acupan the common observation of cross cutting relationships between porphyry and epithermal veins observed throughout the baguio district imply that the evolution of porphyry style to intermediate sulfidation style mineralization was a common phenomenon in this region and contributed significantly to its rich metal endowment

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

glaciers glacial lakes and glacial lake outburst floods in the mount everest region nepal recent climate changes have had a significant impact on the high mountain glacial environment rapid melting of glaciers has resulted in the formation and expansion of moraine dammed lakes creating a potential danger from glacial lake outburst floods glofs most lakes have formed during the second half of the 20th century glaciers in the mount everest sagamartha region nepal are retreating at an average rate of 10 59 m a 1 from 1976 to 2000 lumding and imja glaciers retreated 42 and 34 m a 1 respectively a rate that increased to 74 m a 1 for both glaciers from 2000 to 2007 during the past decade himalayan glaciers have generally been shrinking and retreating faster while moraine dammed lakes have been proliferating although the number of lakes above 3500 m a s l has decreased the overall area of moraine dammed lakes is increasing understanding the behaviour of glaciers and glacial lakes is a vital aspect of glof disaster management

re os dating of low level highly radiogenic llhr sulfides the harnas gold deposit southwest sweden records continental scale tectonic events to obtain geologically meaningful and precise results on low level sulfides that are highly radiogenic blank corrections that account for the extreme difference in the os isotope composition of sample and blank are necessary and the resulting data is best plotted in 187 re 187 os space much like the approach used for molybdenites we here introduce the acronym llhr as a means of characterizing low level and highly radiogenic sulfides use of the traditional 187 re 188 os vs 187 os 188 os plot for llhr sulfides leads to large analytical uncertainties and highly correlated errors as 188 os is poorly determined and can generally be accounted for by the blank we now recognize that llhr sulfides such as those encountered at the harnas au deposit are a common occurrence and characteristic of many crustally affiliated ore systems the harnas au deposit in southwest sweden is located in the mjosa vanern mineral belt that transects from northwest to southeast the prominent geologic fabric of the sveconorwegian province including the mylonite zone the deposit is hosted in a strongly sheared and locally brecciated sulfide bearing quartz vein that crosscuts the foliation of orthogneisses belonging to the 1600 maa mal granitoid suite a 187 re 187 os isochron of 973 34 ma 2 for samples of pyrite and chalcopyrite from outcrops of the harnas alma and silvergruvan veins was obtained the harnas and subsidiary alma veins are au bearing whereas the silvergruvan 2 5 km to the southeast is not of the au bearing type four replicate analyses of an additional pyrite sample from the harnas vein yield a model age of 616 40 ma 95 c l in all samples re and 187 os concentrations are extremely low 0 35 to 7 1 and 0 005 to 0 074 ppb respectively and total common os 0 002 0 028 ppb is less than half the calculated radiogenic 187 os two samples of galena from the harnas vein yielded blank level re and os neither the 973 nor 616 ma time of mineralization is related to development of the mylonite zone at 920 ma or intrusion of the anorogenic bohus blomskog granites at 920 to 900 ma previously proposed sources for generating mjosa vanern mineral belt ore fluids an age of 973 ma for harnas alma silvergruvan suggests that sulfide deposition was associated with the waning stages 0 97 0 90 ga of the sveconorwegian grenvillian orogeny 1 15 0 90 ga postdating metamorphism and deformation that produced a regionally overthickened crust in the northern part of the sveconorwegian province the vein systems for these and numerous other small deposits in the mjosa vanern mineral belt could have resulted from regional exhumation in the late sveconorwegian with associated extension and the development of fracture systems at cooler middle to upper crustal levels in the southern part of the sveconorwegian province dominated by granulitic facies rocks no mineralization is present perhaps due only to increased exhumation and erosion that has exposed deeper crustal levels the late sveconorwegian age 973 ma records the main period of sulfide deposition for the harnas alma silvergruvan vein systems and indicates the robustness of the chronometer within tectonically complex terranes the late neoproterozoic age 616 ma records a later time of pyrite deposition probably associated with shearing and reopening of the harnas vein system because the au mineralization at harnas has been described as associated with shearing and occurring in fracture fillings in early pyrite we suggest that part or all of the au mineralization could have been introduced at 616 ma during reactivation of the vein system the 616 ma age for pyrite suggests a previously unrecognized and much younger mineralizing episode in the harnas region most likely reflecting continental scale extension and the late neoproterozoic opening of the iapetus ocean

geometallurgy of the pebble porphyry copper gold molybdenum deposit alaska implications for gold distribution and paragenesis the pebble cu au mo deposit in southwest alaska is one of the world s largest porphyry deposits the deposit contains over 80 billion pounds blbs cu 107 million ounces moz au and 5 6 blbs mo in all resource categories copper and gold grades vary across diverse hydrothermal alteration assemblages with higher grades associated with sericite and pyrophyllite rich assemblages in an advanced argillic alteration zone moderate grades are associated with the potassic and sodic potassic alteration assemblages that dominate the deposit and low grades are found in quartz illite pyrite assemblages these variations reflect fluctuations in both the temperature and composition of the magmatic hydrothermal fluids in time and space qemscan scanning electron microscope based mineral mapping and in situ laser ablation inductively coupled plasmamass spectrometry methods designed to document the spatial and temporal variations in metal deportment across alteration zones show that gold occurs as inclusions of electrum and high fineness gold in chalcopyrite and pyrite and as free grains hosted by silicate minerals with the proportion of each related to the principal host alteration assemblage gold associated with the earliest high temperature sodic potassic and potassic assemblages occurs as electrum inclusions in chalcopyrite and to a lesser extent pyrite and pyrite trace element signatures have high gold silver and copper concentrations pyrite 1 during cooling of the hydrothermal system lower temperature illite and illite kaolinite alteration overprinted the earlier assemblages with varying degrees of recrystallization and precipitation of more pyrite rich assemblages with pyrite having a gold poor trace element composition pyrite 2 gold released during recrystallization formed high fineness gold inclusions in newly formed pyrite and narrow gold rich pyrite rims pyrite 3 a second magmatic hydrothermal event resulted in a sericite and pyrophyllite rich advanced argillic overprint which introduced more copper and gold to the system and recrystallized preexisting sulfides into both high and low sulfidation assemblages with high fineness gold inclusions in pyrite and chalcopyrite and solid solution gold in bornite a second generation of pyrite 1 with elevated palladium concentrations is associated with this hydrothermal fluid pulse and also possibly high arsenic pyrite pyrite 4 understanding the controls on gold deportment provides genetic constraints on ore deposit genesis alteration and sulfide assemblages and gold compositions provide information on the hydrothermal fluid compositions ph and temperature evolution of the magmatic hydrothermal system the presence of electrum inclusions in chalcopyrite and pyrite in potassic and sodic potassic alteration is consistent with these zones forming from early high temperature magmatic fluids because both gold and silver are transported together in such fluids high fineness gold inclusions in younger pyrite related to low temperature clay alteration are evidence that the gold in early electrum was partially remobilized and reprecipitated the low temperature clay alteration most likely formed from a mixture of h2s rich vapor with meteoric waters conditions where gold is transported as a bisulfide complex and silver is not resulting in the separation of the two metals a second structurally controlled pulse of magmatic fluids formed a well mineralized advanced argillic alteration assemblage containing high fineness gold inclusions in chalcopyrite and pyrite the only part of the deposit where high fineness gold is hosted by chalcopyrite in the pyrophyllite stability field acidic fluid compositions transport gold and silver as different complexes and gold solubility is significantly lower than silver leading to the precipitation of highfineness gold inclusions palladium is transported by the same complex as gold under these conditions consistent with the elevated palladium content of pyrite in the advanced argillic alteration assemblage the temporal and spatial studies of variations in gold deportment across the pebble deposit provide critical inputs to optimization of mineral processing design the greatest influence on metallurgical gold recovery at pebble is the proportion of gold that is hosted by pyrite pyrite hosted gold may require different mineral processing methodologies compared with gold hosted by chalcopyrite therefore defining domains of consistent hydrothermal alteration and sulfide mineralogy and gold deportment is the key to the geometallurgical characterization of the deposit

hydrothermal transport of ag au cu pb te zn and other metals and metalloids in new zealand geothermal systems spatial patterns fluid mineral equilibria and implications for epithermal mineralization in order to analyze the concentrations of ag as au cd cu hg mn mo ni pb se sb te tl w and zn in deep hydrothermal chloride waters at 195 to 320 c and in shallow boiled chloride waters at 160 to 230 c we sampled wells drilled to 3 km depth in geothermal systems of the north island new zealand six of the systems are located in a segment of volcanic arc in the central taupo volcanic zone and the seventh system is associated with an intraplate mafic felsic volcanic center the concentrations of metals range widely from 0 1 to 1 000 g kg with a large degree of intersystem variability some of the largest contrasts in au ag pb and te concentrations are observed in the two nearest systems rotokawa and wairakei which are only 10 km apart the correlations between metals are poor except for ag au pb te and as sb the correlations between metals cl and h2s are also poor with the exception of rotokawa where the highest concentrations of ag au cu and te correlate with the highest concentration of aqueous h2s speciation calculations indicate that the dominant aqueous species of ag au cu pb and zn involve hs complexes the calculations also show that the states of saturation range from undersaturated conditions for acanthite arsenopyrite and gold to oversaturated conditions for chalcopyrite sphalerite and tellurides notably the au and ag transporting capacities of the deep chloride waters are much larger than the measured aqueous concentrations these results suggest that fluid mineral equilibria and the concentrations of ligands exert weak influence on metal concentrations at the temperatures and depths of sampling the complex trends in hydrothermal metal concentrations strongly suggest that the deep seated sources of metals comprising magmatic intrusions deep country rock and their related fluids limit the hydrothermal supplies of metals between the geothermal systems hydrothermal fluxes of ag 6 8 000 kg y au 0 9 66 kg y cu 30 23 500 kg y and te 2 10 400 kg y are variable the highest concentrations and fluxes of ag au and te in rotokawa and mokai are attributed to direct fluid inputs from intrusions of andesitic and basaltic magmas respectively compared to their deep counterparts boiled chloride waters are strongly depleted in ag au cd cu pb and te because these metals deposit in sharp response to gas loss and cooling in the well by comparison the as mn mo ni sb tl and zn concentrations are measurably less depleted in boiled waters making them available to form metal anomalies at shallow depths and in the peripheral parts of the epithermal environment periods of strong metal flux through the geothermal system combined with deep boiling favor epithermal ore formation and the development of large precious metal deposits however even moderate metal fluxes can produce au and ag mineralization as long as the duration of focused fluid flow and boiling can be sustained there is no evidence that the compositions of deep magmatic intrusions mafic or intermediate limit the ore forming potential of a geothermal system

can the snowline be used as an indicator of the equilibrium line and mass balance for glaciers in the outer tropics because the glacier snowline is easy to identify on optical satellite images and because in certain conditions it can be used as an indicator of the equilibrium line it may be a relevant parameter for the study of the relationships between climate and glaciers although several studies have shown that the snowline altitude sla at the end of the hydrological year is a good indicator of the equilibrium line altitude ela for mid latitude glaciers such a relationship remains conjectural for tropical glaciers indeed unlike in mid latitudes tropical climate conditions result in a distinct seasonality of accumulation ablation processes we examine this relationship using direct field ela and mass balance measurements made on glaciar zongo bolivia 168 s and glaciar artesonraju peru 98 s and the sla retrieved from satellite images acquired in the past two decades we show that on glaciers in the outer tropics 1 ablation is reduced during the dry season in austral winter may august the sla does not change much and satellite images acquired between may and august could be used to compute the sla and 2 the highest sla detected on a number of satellite images acquired during the dry season provides a good estimate of the annual ela however as snowfall events can occur during the dry season the sla detected on satellite images tends to underestimate the ela thus we recommend validating the sla computed from satellite images with field data collected on a benchmark glacier before measuring the sla on other glaciers in the same mountain range for which no field data are available this study is a major step towards extending the measurement of glacier parameters ela and mass balance at the scale of a whole mountain range in the outer tropics to better document the relationships between climate and glaciers

reos and s isotopic constraints on the origins of two mineralization events at the tangdan sedimentary rock hosted stratiform cu deposit sw china abstract the tangdan stratiform cu deposit in the kangdian region of south china is hosted in sedimentary rocks of the late paleoproterozoic to early mesoproterozoic dongchuan group orebodies mainly occur in dolostone and black shale above a thick sequence of hematitic sandstone and siltstone mineralization consists mainly of bedding parallel stratiform ores with minor amounts of discordant vein type ores both stratiform and vein type ores are composed of bornite and chalcopyrite with minor chalcocite and digenite associated with gangue minerals including ankerite dolomite calcite and quartz cu sulfides from vein type ores contain 122 293 ppb re much higher than those of stratiform ores 0 6 14 ppb re they have highly radiogenic os with re os model ages ranging from 1413 to 1457 ma and a weighted mean re os model age of 1432 19 ma 2 mswd 0 30 which is within uncertainty in agreement with isochron ages of 1401 30 ma 2 mswd 0 67 and 1397 71 ma 2 mswd 0 22 using 187 re 188 os versus 187 os 188 os and 187 re versus 187 os regression respectively in contrast sulfides from stratiform ores did not yield meaningful model ages due to the extremely low concentrations of re and radiogenic os however early studies have shown that the stratiform ores were likely formed at 1700 ma during the diagenesis of the host strata sulfides from the vein type ores have 34 s values ranging from 15 to 8 significantly lower than those of stratiform ores 3 to 10 suggesting that organic matter may have been involved in the formation of the vein type ores contrasting re os and s isotopes suggest that the two types of ores at the tangdan deposit were likely formed from different ore forming fluids we propose that stratiform ores were precipitated from basinal fluids during the early evolution of the rift basin whereas the vein type ores were formed due to a much younger thermal event during which hydrothermal fluids interacted with overlying black shale to account for the high re and negative 34 s values this study demonstrates that re os isotopes of sulfides can be used to study the origin of hydrothermal system

unraveling the western churchill province paleoproterozoic gold metallotect constraints from re os arsenopyrite and u pb xenotime geochronology and la icp ms arsenopyrite trace element chemistry at the bif hosted meliadine gold district nunavut canada the gold endowment of the western churchill province is conventionally attributed to reworking and attendant metamorphism during the trans hudson orogeny 1 9 1 8 ga the meliadine gold district is regarded as a type example of this inferred paleoproterozoic gold metallotect and also represents one of canada s largest emerging orogenic greenstone and banded iron formation bif hosted gold districts 2 8 moz contained au in reserves and total resource of 5 8 moz au the largest gold deposits are cospatial with the pyke fault and associated quartz ankerite veining which cuts neoarchean ca 2 66 ga plutonic and supracrustal rocks comprising the rankin inlet greenstone belt meliadine gold occurs as inclusions within idioblastic arsenopyrite crystals at sulfide crystal boundaries and or as sulfide fracture fills in hydrothermally altered sulfidized and veined bif clusters of gold bi mo telluride chalcopyrite and galena inclusions characterize high grade ore zones and are spatially associated with sieve textured arsenopyrite domains these microtextural relationships suggest that incipient sulfide recrystallization liberated gold which along with other precious and base metals was redistributed during late fluid assisted and deformation metamorphic driven remobilization late precious and base metal enrichment is also demonstrated by in situ laser ablation inductively coupled plasma mass spectrometry la icp ms arsenopyrite mapping hydrothermal xenotime crystals occur with gold in low strain microtextural sites and yield u pb ages at ca 1 86 ga suggesting that remobilization was concomitant with trans hudson orogenesis new re os arsenopyrite model ages range from 2 3 to 1 8 ga and document a hitherto unrecognized pre 1 86 ga hydrothermal activity the range of re os model ages tends to support partial open system behavior and or mixing of disparate arsenopyrite generations that are evident from microtextural observations and in situ la icp ms element mapping replicate analyses of the two most rhenium rich arsenopyrite samples yield reproducible re os model ages at ca 2 27 and 1 90 ga these rhenium rich samples are also gold poor and likely yield ages that predate gold remobilization and subsequent enrichment along arsenopyrite crystal boundaries and fractures we suggest that pre 1 86 ga hydrothermal activity was likely critical to the gold endowment of the district but is obscured by reworking during the later stages of the trans hudson orogeny at 1 86 ga if correct these new ages imply that the paleoproterozoic gold metallotect which is recorded across the western churchill province in fact comprises multiple temporally distinct gold events differentiating between disparate paleoproterozoic gold events represents a critical step for effective mineral exploration in the western churchill province and at other reworked archean terranes

glacier mass balance in the qinghai tibet plateau and its surroundings from the mid 1970s to 2000 based on hexagon kh 9 and srtm dems abstract in the context of global warming glacier changes in the qinghai tibet plateau qtp and its surroundings have attracted a great amount of public attention to date there have been many studies of glacier mass balance across the qtp however given that most of the previous studies have focused on a short observation period 2000 2015 and that long term mass change measurements are available only for some local regions we utilized declassified kh 9 images and 1 arc second shuttle radar topography mission srtm digital elevation models dems to provide the region wide mass balance from the mid 1970s to 2000 for a larger scale including 11 sample regions across the qtp and its surroundings the final results indicate that the glaciers in the northwest of the qtp have shown a less negative or near zero mass balance ranging from 0 11 0 13 m w e a 1 to 0 02 0 10 m w e a 1 compared to those in the southeast part with a mass balance range of 0 30 0 12 m w e a 1 to 0 11 0 14 m w e a 1 the most serious mass loss has emerged in the central eastern himalaya integrating our results with the observations after 2000 suggests that over the past four decades mid 1970s to the mid 2010s the glaciers in the himalaya nyainqentanglha and tanggula mountains as a whole have exhibited accelerated mass loss and the most significant acceleration has occurred in the eastern nyainqentanglha moreover the hindu raj glaciers have shown a stable rate of continuous mass loss while a nearly stable or slight mass gain state in the western kunlun region can be dated back to at least as far as the mid 1970s

sources of solutes and heat in low enthalpy mineral waters and their relation to tectonic setting new zealand abstract approximately 90 of the low enthalpy spring systems in new zealand are distributed along the present day convergence of the pacific and australian plates which varies from subduction to oblique plate collision forearc subducted waters rising in the hikurangi accretionary prism consist of pore waters containing labile organic material water of hydration from clays and seawater these subducted waters are traceable in the north island axial ranges and the northern marlborough fault system in the south island albeit modified by temperature mixing with surface and heated meteoric waters and protracted interaction with the rock the signature of subducted marine sediments in the hikurangi trench is retained in the chemical and isotopic compositions of the taupo volcanic zone magmatic arc type waters the concentrations of b ba br ca cl i k li mg na rb and sr solutes found in high concentrations in forearc subducted waters increase from northeast to southwest towards the incipient subduction zone in the puysegur trench southwest of south island most thermal mineral waters in the south island are expelled along the alpine fault zone where plate collision results to rapid uplift of the southern alps elevated geothermal gradients and fault shearing of rocks in the alpine fault zone variations in temperatures 175 30 c and mineral water compositions are affected by elevation hydrological gradient intensity of tectonic activity permeability fluid volume and rate of throughput and rates of uplift as the main trace of the alpine fault zone is approached concentrations of cl and other solutes generally increase suggesting increasing contributions from ascending cl rich metamorphic waters outside the active convergent zone low enthalpy springs discharge diagenetically modified ancient forearc waters na cl sedimentary formation waters and heated seawater na hco 3 cl waters and na hco 3 deep circulating heated meteoric waters the total surface heat flow in the north island low enthalpy mineral waters is more than 10 higher than in the south island with projected subsurface temperatures as high as 250 c this is because of the widespread occurrence of shallow magmatic and mantle sources associated with pliocene to holocene volcanism and back arc continental rifting the sources of heat and solutes in low enthalpy mineral waters outside the taupo volcanic zone and ngawha are decoupled except for rapidly ascending hot pore waters in the hikurangi accretionary prism and low temperature serpentinization ca cl waters in fiordland

kinematics of cretaceous subduction and exhumation in the western rhodope chalkidiki block in the chalkidiki peninsula of northern greece a thrust complex made of a basement vertiskos unit a cover circum rhodope belt and arc back arc units chortiatis magmatic suite and eastern vardar ophiolites is exposed in the chalkidiki peninsula of northern greece the complex forms the western part of the rhodope metamorphic province and lies on the hanging wall of the kerdylion detachment the structure responsible for the exhumation of the southern rhodope core complex and the most prominent and visible ductile structure related to the tertiary aegean extension the chalkidiki thrust complex arguably preserves a complete record of cretaceous deformation and related fabrics in this contribution we describe the geometry of foliation stretching lineation and shear sense s on a regional scale the regional foliation strikes nw se and displays different patterns in the three studied units i dominantly dipping at low angle in the vertiskos unit ii affected by upright folding in the circum rhodope belt and iii systematically steeply dipping to the ne in the chortiatis magmatic suite stretching lineation trend dominantly sw ne in the three mentioned units on the basis of new mapping neglecting local perturbations and deformation related to tertiary extension we infer the regional kinematics of cretaceous syn metamorphic thrusting and subsequent exhumation of the metamorphic units thrusting took place toward the sw in present day coordination and the related fabrics are recorded throughout the metamorphic pile on the contrary exhumation related fabrics are related to shear toward the ne and are preferentially recorded in the uppermost part of the metamorphic pile suggesting that extension was more localised and of less finite intensity compared to thrusting

metallogenic features of miocene porphyry cu and porphyry related mineral deposits in ecuador revealed by re os 40ar 39ar and u pb geochronology mineralization and alteration events at ten miocene porphyry cu and porphyry related epithermal mineral deposits in southern central and northern ecuador were dated by means of molybdenite re os biotite and alunite 40ar 39ar and titanite u pb geochronology most of these hydrothermal events show a spatio temporal correlation with porphyry intrusion emplacement as constrained by zircon u pb ages the total age range for these events spans the 23 5 6 1 ma period without displaying systematic along or across arc age distribution trends while epithermal deposits tend to be spatially associated with volcanic rocks of a similar age porphyry cu deposits in ecuador are frequently spatially associated with deeper seated basement units and batholith scale precursor intrusive systems assembled over 5 m y time periods in most cases formation of the porphyry cu deposits is related to the youngest magmatic hydrothermal event in a given area postdating batholith construction at a regional scale the majority of miocene deposits occurs in southern ecuador where areally extensive post mineralization late miocene to recent volcanic sequences with the potential to conceal mineralization at depth are lacking only few miocene deposits occur in northern central ecuador where they mainly crop out in the western cordillera west of the productive present day volcanic arc the surface distribution of post mineralization arc volcanism reflects along arc variations in subducting slab geometry porphyry cu and epithermal deposits in ecuador define a miocene metallogenic belt broadly continuous with its coeval counterpart in northern central peru although both belt segments were formed in an overall similar tectonomagmatic and metallogenic setting their respective metal endowments differ significantly

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

recent expansions of glacial lakes in the bhutan himalayas current conditions and secular changes in ice contact lakes in the bhutan china border region were investigated using satellite imagery more than 50 moraine dammed ice contact or ice proximal lakes were identified of which 14 were evidently growing in debris covered areas of valley glaciers lake growth is characterised by the initial appearance of supraglacial lakes and subsequent upstream expansion by a coalesced lake in small debris free or partially debris covered glaciers lake growth begins from a single lake lake growth has continued over a period ranging from 20 to 70 years with a growth rate of 70 m year in length and 0 04 km2 year in area these values observed at the northern side of the main himalayan range are smaller than those observed at the southern side the initial appearance year estimated from the expansion rate of most of the lakes in the southern and northern sides ranges from the 1950s to the 1970s and before the 1950s respectively

sulfur isotopic zonation in the cadia district southeastern australia exploration significance and implications for the genesis of alkalic porphyry gold copper deposits the alkalic porphyry gold copper deposits of the cadia district occur in the eastern lachlan fold belt of new south wales australia the district comprises four porphyry deposits ridgeway cadia quarry cadia hill and cadia east and two iron copper gold skarn deposits big cadia and little cadia almost 1 000 tonnes of contained gold and more than four million tonnes of copper have been discovered in these systems making cadia the world s largest known alkalic porphyry district in terms of contained gold porphyry gold copper ore at cadia is associated with quartz monzonite intrusive complexes and is hosted by central stockwork and sheeted quartz sulfide carbonate vein systems the cadia porphyry deposits are characterized by cores of potassic and or calc potassic alteration assemblages and peripheral halos of propylitic alteration with late stage phyllic alteration mostly restricted to fault zones hematite dusting is an important component of the propylitic alteration assemblage and has produced a distinctive reddening of feldspar minerals in the volcanic wall rocks around the mineralized centers sulfide mineralization is strongly zoned at ridgeway and cadia east with bornite rich cores surrounded by chalcopyrite rich halos and peripheral zones of pyrite mineralization the cadia hill and cadia quarry deposits have chalcopyrite rich cores and pyrite rich halos and cadia hill contains a high level bornite rich zone distinctive sulfur isotopic zonation patterns have been identified at ridgeway cadia hill and cadia east the deposit cores are characterized by low 34ssulfide values 10 to 4 consistent with sulfide precipitation from an oxidized sulfate predominant magmatic fluid at 450 to 400 c pyrite grains that occur in the propylitic alteration halos typically have 34ssulfide values near 0 there is a gradual increase in 34ssulfide values outwards from the deposit cores through the propylitic halos water rock interaction during propylitic alteration caused magmatic sulfate reduction and concomitant oxidation of ferrous iron bearing minerals resulting in enrichment of 34s in pyrite and also producing the distinctive reddened hematite rich alteration halos to the cadia deposits these results show that sulfur isotope analyses have potential applications in the exploration of alkalic porphyry style deposits with zones of depleted 34ssulfide values most prospective for high grade mineralization

isotopic geochemistry of the sawayaerdun orogenic type gold deposit tianshan northwest china implications for ore genesis and mineral exploration the sawayaerdun gold deposit is hosted by carbonaceous metasediments and is considered to be the largest muruntau type gold deposit in the chinese tianshan metallogenic belt gold mineralization at sawayaerdun occurs in quartz veins associated with three major hydrothermal events an early barren quartz vein stage middle stage mineralized quartz veins with pyrite and late carbonate quartz veins the isotopic compositions of quartz and sulfides from the sawayaerdun gold deposit show some variation but are generally comparable to those of other orogenic type gold deposits fluids trapped in early stage quartz have a 18o range of 13 6 to 15 4 d of 48 to 75 13c of 0 5 to 4 2 and 30si of 0 2 to 0 in contrast isotopic compositions of fluids trapped in middle stage quartz have 18o values of 6 7 to 14 7 d of 56 to 110 13c of 0 4 to 10 1 and 30si of 0 3 to 0 diagenetic and hydrothermal pyrite have similar sulfur 1 8 to 0 9 and pb isotopic values that are associated with host rock compositions the early stage 18o and 13c rich fluids are probably derived from metamorphic decarbonation of the sedimentary host rock at depth leading to the precipitation of early barren quartz veins in the middle stage a decrease in the regional pressure and temperature regime could have resulted in the incorporation of external fluids into the ore forming system these external fluids with isotopic signatures similar to that of the host rock and generally rich in 34s and radiogenic pb mixed with original ore forming fluids to generate extensive metal precipitation late stage fluids trapped by calcite veins show isotopic compositions similar to meteoric water indicating the cessation of hydrothermal fluid circulation at sawayaerdun occurred at this time the metallogenetic model illustrated by stable and pb isotopes is also consistent with fluid inclusion studies in sawayaerdun the development of mineralization at sawayaerdun is strongly linked to fluid mixing as witnessed by the isotopic signatures of fluids from identified ore bearing zones the isotopic compositions of other anomalous zones at sawayaerdun are similar to those of the mineralized zones suggesting a high potential for further exploration 2012 elsevier b v

trace element signature of pyrite from the los colorados iron oxide apatite ioa deposit chile a missing link between andean ioa and iron oxide copper gold systems although studies have proposed that iron oxide apatite ioa deposits may represent the deeper roots of some andean iron oxide copper gold iocg systems their genetic links remain obscure and controversial a key question when considering an integrated genetic model is whether a magmatic hydrothermal fluid that precipitates massive magnetite will continue transporting significant amounts of dissolved fe cu and au after ioa precipitation here we provide new geochemical data for accessory pyrite from the los colorados ioa deposit in the chilean iron belt that confirm the role of this sulfide as a relevant repository for economic metals in ioa deposits pyrite occurs at los colorados as disseminated grains and as veinlets associated with magnetite and actinolite that postdate the main igneous magnetite stage electron probe microanalysis epma data for pyrite show anomalously high co and ni concentrations up 3 9 and 1 5 wt respectively and relatively high as contents 100s of ppm to a maximum of 2 000 ppm when combined with results from secondary ion mass spectrometry sims spot analyses pyrite data show significant amounts of cu that range from sub ppm values 100 ppb up to 1 000s of ppm plus nonnegligible concentrations of zn pb cd sb se and te up to 100 ppm the highest contents of cu measured wt level most likely record the presence of cu bearing submicron sized mineral inclusions contents of au and ag are up to 1 and 10 ppm respectively with maximum concentrations that can rise up to 800 ppm au and 300 ppm ag due to the presence of submicron sized inclusions the high co ni ratios of pyrite from los colorados are consistent with a magmatic hydrothermal origin associated with a greater mafic affinity compared to pyrite from porphyry cu deposits furthermore the geochemical signature of los colorados pyrite shares important similarities of composition and microtexture with the few published data for pyrite from iocg deposits e g ernest henry australia and manto verde chile these findings combined with recent geochemical and isotopic studies that support an igneous origin for the dike shaped magnetite orebodies at los colorados point to a magmatic source of mafic to intermediate composition for the contained metals and support the hypothesis that ioa systems can source fe cu au rich fluids based on experimental studies these ioa derived fluids may continue transporting significant amounts of metals to form iocg mineralization at shallower levels in the crust

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

genesis of middle miocene yellowstone hotspot related bonanza epithermal au ag deposits northern great basin usa epithermal deposits with bonanza au ag veins in the northern great basin ngb are spatially and temporally associated with middle miocene bimodal volcanism that was related to a mantle plume that has now migrated to the yellowstone national park area the au ag deposits formed between 16 5 and 14 ma but exhibit different mineralogical compositions the latter due to the nature of the country rocks hosting the deposits where host rocks were primarily of meta sedimentary or granitic origin adularia rich gold mineralization formed where glassy rhyolitic country rocks host veins colloidal silica textures and precious metal colloid aggregation textures resulted where basalts are the country rocks clay rich mineralization with silica minerals adularia and carbonate developed oxygen isotope data from quartz originally amorphous silica and gels from super high grade banded ores from the sleeper deposit show that ore forming solutions had 18o values up to 10 heavier than mid miocene meteoric water the geochemical signature of the ores including their se rich nature is interpreted here to reflect a mantle source for the epithermal suite elements au ag se te as sb hg and that signature is preserved to shallow crustal levels because of the similar volatility and aqueous geochemical behavior of the epithermal suite elements a mantle source for the gold in the deposits is further supported by the pb isotopic signature of the gold ores apparently the host rocks control the mineralization style and gangue mineralogy of ores however all deposits are considered to have derived precious metals and metalloids from mafic magmas related to the initial emergence of the yellowstone hotspot basalt derived volatiles and metal loid s are inferred to have been absorbed by meteoric water dominated geothermal systems heated by shallow rhyolitic magma chambers episodic discharge of volatiles and metal loid s from deep basaltic magmas mixed with heated meteoric water to create precious metal ore forming fluids colloidal nanoparticles of au ag alloy electrum naumannite ag2se silica and adularia likely nucleated at depth traveled upward and deposited where they grew large enough to aggregate along vein walls silica and gold colloids have been reported in hot springs from yellowstone national park suggesting that such processes may continue to some extent to the present however it is possible that the initial development of the mantle plume led to a major but short lived distillation process which led to the mid miocene bonanza ore forming event

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

the new remote sensing derived swiss glacier inventory ii first results complete swiss glacier inventories are available for 1850 reconstructed and 1973 from aerial photography connected to the global land ice measurements from space project a new swiss glacier inventory for approximately the year 2000 sgi 2000 is compiled mainly based on satellite imagery the developed and applied remotesensing and geographical information system gis methods are described in part i of the contribution in part ii the inventory design first result analyses and comparisons with former glacial conditions are presented as basic entries sgi 2000 contains the individual glacier identification planimetric glacier boundaries as derived from image analysis digitized central flowlines and polygonal glacier basin maps all other parameters are automatically deduced from the above entries and a digital elevation model within a gis here we analyze a set of small bernese and valais glaciers of area 2 these glaciers lost about 21 of area from 1973 to 1998 in addition to about 80 during 1850 1973 both with respect to the 1973 area in order to track the latest trend in more detail anintermediate glacier condition has been compiled from satellite imagery of 1985 this analysis gave an increasing speed of area loss 19 for 1985 98

epithermal deposits in north xinjiang nw china the north xinjiang region nw china is an important part of the central asia orogenic belt situated at the junction of siberia tarim and kazakhstan plates it is an area characterized by multiple stages of phanerozoic continental growth during which several porphyry and epithermal systems were formed the relationship of these mineral systems to the geodynamic evolution of the region has not yet been well understood in this paper we list the main geological characteristics of 21 significant epithermal precious and base metal deposits in north xinjiang and classify them into high sulfidation and low sulfidation styles with the latter being predominant we have selected seven epithermal deposits representing different styles formed under different tectonic regimes and discuss their geology and geochemistry in some detail the deposit scale geology and geochemistry of epithermal systems in north xinjiang are essentially similar to those in other parts of the world all epithermal deposits in north xinjiang are hosted in volcanic rocks with ages ranging from devonian to triassic with the early carboniferous volcanic sequences being the most important followed by the permian and triassic the devonian early carboniferous host rocks belong to the calc alkaline series that developed in pre collisional arc back arc basin systems whereas the permian triassic host volcanic rocks of shoshonite series formed in post subduction regimes available isotopic ages of these epithermal systems cluster in two periods early carboniferous 320 ma and late carboniferous triassic 320 220 ma reflecting two metallogenic episodes that occurred during subduction related accretion and post subduction collision regimes respectively accordingly three groups of epithermal deposits in north xinjiang can be recognized as 1 pre collisional deposits without or with negligible collisional related modification 2 deposits formed in collision regime and 3 ore systems strongly overprinted by fluid flow in post subduction collision regime

the timing of epigenetic gold mineralization on the baie verte peninsula newfoundland canada new evidence from re os pyrite geochronology the absolute timing of epigenetic mineralization including most types of gold deposits is difficult to resolve due to the absence of suitable minerals in veins and replacement zones however gold is commonly closely associated with pyrite and arsenopyrite which may be amenable to re os geochronology providing sufficient re and os are present within them this short paper outlines the use of this method to date two gold deposits in newfoundland using pyrite although the os contents of the pyrites are extremely low 0 1 ppb the os is almost exclusively radiogenic 187os and data are amenable to model age calculations as used in re os molybdenite dating the pyrites from these deposits correspond to low level highly radiogenic sulphides as defined by other studies the stog er tight and pine cove gold deposits yield mean re os model ages of 411 7 ma n 4 and 420 7 ma n 5 respectively which agree with isochron regression of 187os against 187re the re os age for stog er tight is within uncertainty of a previous u pb age from hydrothermal zircon 420 5 ma in spatially related alteration a latest silurian earliest devonian age for the mineralization is consistent with indirect age constraints from some other gold deposits in central newfoundland and suggests a broad temporal link to the mid silurian salinic orogeny however the gold mineralization appears to be younger than most plutonic activity associated with this event the results illustrate the potential value of re os pyrite geochronology in understanding the temporal framework of epigenetic mineralization especially if future improvements in analytical precision and reductions in procedural blanks allow wider application to material with similarly low re and os concentrations

hydrothermal evolution of the copler porphyry epithermal au deposit erzincan province central eastern turkey the copler au deposit measured and indicated resource of 122 8 million tonnes at 1 7 g t au 4 8 g t ag and 0 1 wt cu is centered around shallow level dioritic to granodioritic intrusive rocks of the middle eocene copler kabatas magmatic complex which have been emplaced into a succession of regionally metamorphosed late paleozoic mesozoic sedimentary and carbonate rocks the deposit comprises a centrally located subeconomic porphyry cu au system characterized by a potassically altered biotite k feldspar magnetite core overprinted by a more extensive phyllic quartz sericite alteration zone the potassic alteration zone is associated with early m type hairline magnetite and crosscutting b type quartz magnetite sulfide veinlets whereas the enveloping phyllic altered rocks contain abundant d type quartz pyrite and lesser polymetallic quartz sulfide veinlets intermediate sulfidation epithermal au mineralization that overprints the porphyry occurred in two stages main stage epithermal mineralization is characterized by carbonate sulfide veinlets consisting of manganocalcite arsenical pyrite arsenopyrite marcasite chalcopyrite tennantite tetrahedrite galena and sphalerite late stage sooty pyrite veinlets contain some realgar and orpiment and are associated with zones of extensive carbonate alteration in the carbonate sulfide veinlets invisible gold is primarily hosted within arsenical pyrite and to a lesser extent by arsenopyrite tetrahedrite and tennantite in sooty pyrite veinlets invisible gold is associated with fine grained arsenical pyrite manto type carbonate replacement zones occur in the distal portions of the porphyry system and constitute a significant gold resource these carbonate replacement bodies display a mineral paragenesis similar to that of the epithermal carbonate sulfide veinlets in that they contain abundant arsenical pyrite together with lesser chalcopyrite arsenopyrite and marcasite and sparse sphalerite galena tennantite and tetrahedrite invisible gold in these ores is contained mainly within pyrite and chalcopyrite and to a lesser extent in arsenopyrite tetrahedrite and tennantite polyphase brine inclusions 47 62 wt nacl equiv in early b type quartz magnetite sulfide veinlets were trapped together with low salinity 3 5 5 wt nacl equiv vapor rich inclusions at temperatures 390 c and at a depth of 1 5 km under lithostatic conditions fluids associated with the overprinting phyllic alteration were slightly cooler 370 c and less saline 37 42 wt nacl equiv fluid inclusions in manganocalcite and sphalerite from epithermal carbonate sulfide veinlets trapped moderate salinity 4 15 wt nacl equiv fluids at 290 c whereas fluid inclusions hosted in barite and realgar from sooty pyrite veinlets were formed from low temperature 100 c and low to moderate salinity 1 14 wt nacl equiv fluids these data indicate that the au mineralizing system at copler progressed from a high temperature porphyry system to a relatively low temperature intermediate sulfidation epithermal system deposition of gold in the early stages of epithermal mineralization resulted from cooling sulfidation and neutralization of predominantly magmatic sourced hydrothermal fluids whereas a meteoric water component is evident in the latest stage of mineralization deposit scale geologic observations combined with fluid inclusion and stable isotope evidence suggest that mineralization at copler records activity of a relatively deep epithermal system and that its formation was structurally and lithologically controlled specifically the thick premineralization carbonate sequence once overlying the deposit acted as a pressure seal and also as a neutralizing agent during the build up of the magmatic hydrothermal system the weakening of this carbonate cover by igneous intrusion and subsequent hydrothermal activity may have contributed to later selective erosion of the alteration zone thereby telescoping the intermediate sulfidation epithermal system onto the earlier porphyry system and creating the copler window

re os molybdenite pyrite and chalcopyrite geochronology lupa goldfield southwestern tanzania tracing metallogenic time scales at midcrustal shear zones hosting orogenic au deposits a detailed re os molybdenite pyrite and chalcopyrite geochronology at five shear hosted au occurrences kenge mbenge porcupine konokono and dubwana in the lupa goldfield southwestern tanzania is reported in this paper au occurrences within the lupa goldfield share many geologic similarities with the orogenic au deposit type and are situated within a paleoproterozoic magmatic arc that intruded the archean tanzanian cratonic margin pyrite chalcopyrite molybdenite bearing fault fill veins and mylonitic shear zones crosscut granitic host rocks and are associated with the highest au grades re os sulfide ages are deemed a suitable proxy to constrain the timing of au based on the occurrence of au bearing minerals as inclusions within pyrite and chalcopyrite whereas au bearing minerals filling pyrite fractures may represent a younger and undated metallogenic event molybdenite at kenge occurs as ultrafine disseminations within fault fill veins 1953 6 ma n 3 that possess nominally older weighted average re os ages than molybdenite hosted by stylolite like veins 1937 8 ma n 7 both sample sets are ca 70 m y older than a weighted average re os pyrite age from the mylonitic shear zones at kenge and mbenge 1876 10 ma n 13 which contain fault fill veins and record the timing of mylonitization molybdenite at porcupine occurs as ultrafine disseminations within quartz veins and mylonitized granite samples 1886 6 ma n 4 that are broadly equivalent in age to weighted average re os ages of molybdenite occurring as stylolite like veins 1873 5 ma n 6 and pyrite within oblique extension veins 1894 45 ma n 2 weighted average re os pyrite model ages at konokono 1880 14 ma n 9 and dubwana 1905 25 ma n 2 are also consistent with the ca 1 88 ga event observed at kenge mbenge and porcupine gold occurrences in the lupa goldfield therefore record a protracted hydrothermal history 1 95 1 87 ga comprising at least three temporally distinct hydrothermal events ca 1 95 1 94 and 1 88 ga which are each represented in detail by a complex vein history that occurred at a time scale less than the resolution of the re os method the sampling of broadly contemporaneous sulfides from five shear zones suggest that mylonitic shear zones represented an interconnected network of midcrustal permeable fluid conduits at ca 1 88 ga that permitted the transportation and deposition of gold comparison between re os sulfide and high precision u pb zircon ages for the granitic host rocks provides unequivocal evidence for sulfidation concomitant with magmatism however the range of re os ages argues against an intrusion related deposit model whereby metallogenic fluids are solely derived from an individual intrusion the regional ca 1 88 ga metallogenic event identified as part of this study occurred concurrently with eclogite facies metamorphism during the ubendian orogenic cycle and provides one of earth s earliest temporal links between subduction zone processes and orogenic au deposit formation during the paleoproterozoic

automated classification of debris covered glaciers combining optical sar and topographic data in an object based environment abstract satellite imagery is increasingly used to monitor glacier area changes and create glacier inventories robust and efficient pixel based band ratios have proven to be accurate for automatically delineating clean glacier ice however such classifications are restricted on debris covered ice due to its spectral similarity with surrounding terrain object based image analysis obia has emerged as a new analysis technique within remote sensing it offers many advantages over pixel based classification techniques due to the ability to work with multiple data sources and handle data contextually and hierarchically by making use of obia capabilities we automatically classify clean ice and debris covered ice in the challenging area surrounding mount manaslu in nepal using optical landsat 8 topographic void filled srtm and sar coherence alos palsar data clean ice was classified with a mean accuracy of 93 whilst debris covered ice was classified with an accuracy of 83 when compared to manually corrected outlines providing a total glacier accuracy of 91 with further developments in the classification steep tributary sections of ice could be contextually included raising the accuracy to over 94 one prominent advantage of obia is that it allows some post processing and correction of the glacier outlines automatically reducing the amount of manual correction needed obia incorporating sar coherence data is recommended for future mapping of debris covered ice

re os geochronology of the iimori besshi type massive sulfide deposit in the sanbagawa metamorphic belt japan abstract besshi type cu deposits are strata bound volcanogenic massive sulfide deposits usually associated with mafic volcanic rocks or their metamorphic equivalents although there are numerous besshi type deposits in the sanbagawa metamorphic belt japan their tectonic settings and depositional environments remain controversial because of a lack of depositional age constraints we report re os data for the iimori deposit one of the largest besshi type deposits in western kii peninsula in order to examine the robustness of the re os isotope system for dating sulfide minerals in the high p t metamorphic belt and to elucidate the primary depositional environment of the iimori sulfide ores an 11 point re os isochron plot yields an age of 156 8 3 6 ma as this re os isochron age is significantly older than the timing of the sanbagawa peak metamorphism 110 120 or 90 ma and a well defined isochron was obtained the re os age determined here is most likely the primary depositional age despite high grade metamorphism at up to 520 25 c and 8 9 5 kbar the re os isotope system of the iimori sulfides was not disturbed hence we consider that the whole rock re os closure temperature for the iimori sulfide ores was probably higher than 500 c as the accretion age of the sanbagawa metamorphic belt is considered to be 120 130 or 65 90 ma on the basis of radiolarian and radiometric ages we estimated the time from the iimori sulfide deposition on the paleo seafloor to its accretion at the convergent plate boundary to be greater than 25 myr consequently the depositional environment of the iimori sulfide ores was not in the marginal sea but was truly pelagic

pyrite re os isotope systematics at the zijinshan deposit of sw fujian china constraints on the timing and source of cu au mineralization abstract zijinshan is the largest high sulfidation epithermal cu au deposit on mainland china the primary mineralization at the deposit is characterized by pyrite digenite and covellite although some rb sr isochron ages of the fluid inclusions in quartz and the apparent k ar age of the cu bearing alunite alteration zone have been previously interpreted as the ore forming age the rb sr and k ar dating systems are usually readily reset due to their closure temperature and thus document the latest thermal event in order to precisely determine the age of the cu mineralization eight pyrite separates were re os dated and seven yielded an isochron age of 103 4 ma with an initial 187 os 188 os ratio of 0 45 0 14 this date is interpreted as the age of cu mineralization which is in agreement with geochronological data from molybdenite and the porphyritic granodiorite that hosts cu mo mineralization at luoboling located 2 km ne of zijinshan suggesting that these two deposits were formed during the same metallogenic event the relatively low initial 187 os 188 os ratio indicates that the source of the cu at zijinshan is predominantly the crust with input from the mantle

glacial cover mapping 1987 1996 of the cordillera blanca peru using satellite imagery multitemporal glacier area mapping is a key element in accurately determining fresh water reserves as well as providing an indicator of climate change in peru the first glacier inventory was based on visual interpretation of aerial photos requiring several years of effort landsat thematic mapper satellite imagery on the other hand provides an increasingly employed alternative for the monitoring of changes in glacier area and in other glaciological parameters by means of normalized difference snow index ndsi computations on tm images an estimate of the glacierized area in cordillera blanca peru was carried out for 1987 643 63 km2 and 1996 600 61 km2 compared to an estimate of 721 km2 in 1970 it can be concluded that the glacier area has retreated in this massif by more than 15 in 25 years

petrogenesis of the kekesai composite intrusion western tianshan nw china implications for tectonic evolution during late paleozoic time abstract the late carboniferous to permian is a critical period for final amalgamation of the central asian orogenic belt caob which is characterized by voluminous igneous rocks particularly granitoids the kekesai composite granitoid porphyry intrusion situated in the chinese western tianshan southwest part of caob includes two intrusive phases a monzogranite phase intruded by a granodiorite phase la icpms u pb zircon analyses suggest that the monzogranitic rocks were formed at 305 5 1 1 ma with a wide age range of inherited zircons 358 488 ma and 1208 1391 ma whereas the granodioritic rocks formed at 288 7 1 5 ma the monzogranitic and granodioritic phases have similar geochemical features and sr nd hf isotopic compositions they exhibit high and variable sio 2 66 71 wt and mgo 0 41 2 14 wt contents with some arc like geochemical characteristics e g enrichment of large ion lithophile elements and negative anomalies of nb ta and ti and relatively high initial 87 sr 86 sr ratios i sr 0 7055 0 7059 low positive e nd t 0 84 to 1 03 as well as a large variation in hf isotopic compositions with e hf t between 3 43 and 14 8 implying both of them were derived from similar source materials these geochemical characteristics suggest that they might be mainly derived from the partial melting of arc derived mesoproterozoic mafic lower crust with involvement of a mantle derived component in variable proportions by mantle derived magma underplating the presence of late ordovician to earliest early carboniferous inherited zircons and the hf isotopic compositions in the monzogranitic sample similar to that of the widespread juvenile arc rocks indicates some crust contamination during magma emplacement our new data combined with previous studies imply that extensive post collisional magmatism due to underplating of mantle derived magma could plausibly be explained by slab break off regime

using remote sensing data to determine equilibrium line altitude and mass balance time series validation on three french glaciers 1994 2002 alpine glaciers are very sensitive to climate fluctuations and their mass balance can be used as an indicator of regional scale climate change here we present a method to calculate glacier mass balance using remote sensing data snowline measurements from remotely sensed images recorded at the end of the hydrological year provide an effective proxy of the equilibrium line mass balance can be deduced from the equilibrium line altitude ela variations three well documented glaciers in the french alps where the mass balance is measured at ground level with a stake network were selected to assess the accuracy of the method over the 1994 2002 period eight mass balance cycles results obtained by ground measurements and remote sensing are compared and show excellent correlation r 2 0 89 both for the ela and for the mass balance indicating that the remote sensing method can be applied to glaciers where no ground data exist on the scale of a mountain range or a given climatic area the main differences can be attributed to discrepancies between the dates of image acquisition and field measurements cloud cover and recent snowfalls constitute the main restrictions of the image based method

a carbonaceous sedimentary source rock model for carlin type and orogenic gold deposits this paper presents evidence and arguments that carbonaceous sedimentary rocks were a source for au and as in sediment hosted orogenic and carlin type gold deposits and develops a corresponding genetic model in this two stage basin scale model gold and arsenic are introduced early into black shale and turbidite basins during sedimentation and diagenesis stage 1 and concentrated to ore grades by later hydrothermal structural or magmatic processes stage 2 in reduced continental margin basin settings organic matter sedimented under anoxic to euxinic conditions immobilizes and concentrates gold arsenic and a range of trace elements particularly v ni se ag zn mo cu u present in marine bottom waters into fine grained black mudstone and siltstone of slope and basin facies during early diagenesis gold and certain other trace elements ni se te ag mo cu pge are preferentially partitioned into arsenian pyrite that grows in the muds these processes produce regionally extensive black shale and turbidite sequences enriched in syngenetic gold and arsenic commonly from 5 to 100 ppb au and 10 to 200 ppm as rare organic and sulfide rich metalliferous black shales may contain up to 1 to 2 ppm au and over 1 000 ppm as present as refractory gold in arsenian pyrite and nanoparticles of free gold during late diagenesis and early metamorphism stage 2 the diagenetic arsenian pyrite is recrystallized to form coarser grained pyrite generations and the organic matter is cooked to bitumen under higher grade metamorphism lower greenschist facies and above arsenian pyrite in carbonaceous shales is converted to pyrrhotite these processes release gold arsenic sulfur and other elements sb te cu zn mo bi tl and pb from the source rocks to become concentrated by hydrothermal processes locally to produce gold ores in structural sites such as fold hinge zones shear or breccia zones within or above the black shale sequence la icp ms analyses of diagenetic pyrite in carbonaceous sediments both associated and not associated with gold deposits suggests that invisible gold contents of greater than 250 ppb in diagenetic pyrite are indicative of carbonaceous shale source rocks with the potential to produce economic gold deposits application of this sedimentary source rock model enables a systematic exploration approach for sediment hosted gold deposits based on the distribution composition and structure of carbonaceous shale sequences and their contained diagenetic pyrite

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

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

miocene landscape evolution and geomorphologic controls on epithermal processes in the el indio pascua au ag cu belt chile and argentina the world class breccia stockwork and vein hosted epithermal au ag cu deposits of the central andean el indio pascua belt latitudes 29 20 to 30 30 s were emplaced between 6 2 and 9 4 ma immediately beneath the shoulders of an actively uplifting north south tectonic block along the axis of the cordillera principal the deposits of the pascua lama veladero el indio and tambo districts are hosted by largely felsic volcanic units of late oligocene early miocene and late paleozoic age but were associated with small hypabyssal bodies of dacitic porphyry the pascua formation there is no evidence that the epithermal centers were overlain by substantial volcanic edifices the preglacial miocene landscape previously undocumented incorporates three planar erosional landforms of regional extent 1 the ca 15 to 17 ma frontera deidad surface 2 the ca 12 5 to 14 ma azufreras torta surface and 3 the ca 6 to 10 ma los rios surface these pediplains are each vertically separated by 200 to 400 m and by analogy with the enormous erosion surfaces of the atacama desert of northern chile and southern peru are considered to have formed in a semi arid climate in direct response to uplift events although the azufreras torta surface immediately overlies most of the major hydrothermal systems and hence influenced their evolution ore formation was contemporaneous with the development of the younger los rios pediplain and was almost entirely focused around the upper extremities of stage iii valley pediments in contrast precursor high sulfidation hydrothermal alteration zones in the main mineralized districts ranging in age from 10 0 to 13 6 ma and associated with vacas heladas formation dacitic magmatism developed before incision of the los rios pediments and are barren the areal and temporal relationships between economic epithermal centers and the heads of upper miocene valley pediments provide at the least clear empirical exploration guidelines for the el indio pascua belt however it is further proposed that changes in the surficial hydrodynamic environment including the rapid lowering of the water table increased lateral ground water flow and fluid boiling and mixing all favoring ore deposition may have been directly induced by pediment incision in this and other semi arid cordilleran environments in which epithermal mineralization was not associated with significant volcanic edifices

six hundred thirty eight years of summer temperature variability over the bhutanese himalaya high resolution tree ring reconstructions from the himalaya provide essential context for assessing impacts of future climate change on regional water reserves and downstream agriculture here we e

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

combining satellite multispectral image data and a digital elevation model for mapping debris covered glaciers automated glacier mapping from satellite multispectral image data is hampered by debris cover on glacier surfaces supraglacial debris exhibits the same spectral properties as lateral and terminal moraines fluvioglacial deposits and bedrock outside the glacier margin and is thus not detectable by means of multispectral classification alone based on the observation of low slope angles for debris covered glacier tongues we developed a multisource method for mapping supraglacial debris the method combines the advantages of automated multispectral classification for clean glacier ice and vegetation with slope information derived from a digital elevation model dem neighbourhood analysis and change detection is applied for further improvement of the resulting glacier debris map a significant percentage of the processing can be done automatically in order to test the sensitivity of our method against different dem qualities it was also applied to a dem obtained from aster stereo data additionally we compared our multisource approach to an artificial neural network ann classification of debris using only multispectral data while the combination with an aster derived dem revealed promising results the ann classification without dem data does not

the osmium isotopic composition of the continental crust osmium isotopic compositions and concentrations have been determined for deltaic and continental shelf sediments from three major rivers the amazon changjiang and mississippi and for two loesses from the upper mississippi river valley the loesses have heavy mineral and clay compositions characteristic of mississippi river and delta sediment concentrations range from 15 to 120 pg os g and 187os 186os ratios range from 8 2 to 10 9 sediments which are polluted surface sediment from the changjiang estuary or which have scavenged metals from seawater gulf of mexico slope surface sediment and distal amazon shelf sediment have high osmium concentrations and less radiogenic isotopic compositions purely terrigenous sediments have 15 90 pg os g and 187os 186os 10 0 10 9 north american loess and mississippi delta sediment osmium isotopic compositions are indistinguishable we believe that 187os 186os 10 11 is a good average for currently eroding upper continental crust these sediments have neodymium isotopic compositions close to the global mean for river sediment terrigenous 187os 186os is significantly more radiogenic than seawater 187os 186os 8 6 requiring a nonriverine source of osmium to seawater terrigenous osmium is also significantly more radiogenic than bulk pelagic clay osmium we use the improved estimate of terrigenous 187os 186os to recalculate the flux of extraterrestrial osmium to pacific marine sediment if the residence age of osmium in an upper crustal region is similar to the neodymium model age of a sediment derived from that region a model dependent upper crustal 187re 186os ratio can be calculated for the model ages of the sediments analyzed in this study tdm 1 5 1 7 ga model 187re 186os ratios are 340 360 and can be used to correct for bias resulting from the preferential erosion of young crust the 187os 186os ratio of 2 2 ga crust with 187re 186os 400 is 14 2 we have also used the data from this study to estimate upper crustal osmium and rhenium concentrations of 50 pg g and 390 pg g respectively

the new remote sensing derived swiss glacier inventory i methods a new swiss glacier inventory is to be compiled from satellite data for the year 2000 the study presented here describes two major tasks 1 an accuracy assessment of different methods for glacier classification with landsat thematic mapper tm data and a digital elevation model dem 2 the geographical information system gis based methods for automatic extraction of individual glaciers from classified satellite data and the computation of three dimensional glacier parameters such as minimum maximum and median elevation or slope and orientation by fusion with a dem first results obtained by these methods are presented in part ii of this paper kaab and others 2002 thresholding of a ratio image from tm4 and tm5 reveals the best suited glacier map the computation of glacier parameters in a gis environment is efficient and suitable for worldwide application the methods developed contribute to the u s geological survey led global land ice measurements from space glims project which is currently compiling a global inventory of land ice masses within the framework of global glacier monitoring haeberli and others 2000

giant porphyry deposits characteristics distribution and tectonic controls more than half of the 25 largest known porphyry copper deposits defined in terms of contained copper metal formed during three time periods the paleocene to eocene eocene to oligocene and middle miocene to pliocene these giant deposits are clustered within three provinces central chile northern chile and southwest arizona northern mexico other giant deposits occur in montana utah panama peru argentina irian jaya mongolia and iran compressive tectonic environments thickened continental crust and active uplift and erosion were associated with the formation of many of these deposits calc alkalic magmas are most favorable for the formation of giant porphyry copper deposits although several of the largest systems are associated with high k calc alkalic intrusions the 25 largest gold rich porphyry deposits are concentrated in the southwest pacific and south america with other occurrences in eurasia british columbia alaska and new south wales many of the deposits formed in the last 13 m y the largest of the deposits are associated with high k calc alkalic intrusions many calc alkalic porphyritic intrusions have also produced giant gold rich porphyries in the last 20 m y the formation of giant porphyry copper molybdenum and copper gold deposits in the circum pacific region has been closely associated with subduction of aseismic ridges seamount chains and oceanic plateaus beneath oceanic island and continental arcs in several examples these tectonic perturbations have promoted flat slab subduction crustal thickening uplift and erosion and adakitic magmatism coeval with the formation of well endowed porphyry and or epithermal mineral provinces similar tectonic features are inferred to be associated with the giant porphyry copper molybdenum provinces of northern chile eocene oligocene and southwest united states cretaceous paleocene topographic and thermal anomalies on the downgoing slab appear to act as tectonic triggers for porphyry ore formation other factors such as sutures in the overriding plate permeability architecture of the upper crust efficient processes of ore transport and deposition and in some cases formation and preservation of supergene enrichment blankets are also vital for the development of high grade giant ore deposits a low grade geochemical anomaly may be the final product of mineralization if ore forming processes do not operate efficiently even in the most favorable geodynamic settings

the role of sulfur in the formation of magmatic hydrothermal copper gold deposits abstract essential resources of many rare metals including copper zinc molybdenum silver and gold occur in natural sulfide mineral deposits understanding the origin of these metal resources has been limited by a lack of data about the geochemistry of sulfur the most important and abundant element of ore deposits we report the first directly measured sulfur concentrations in high temperature fluids together with their ore metal contents using a new method for sulfur quantification in fluid inclusions by laser ablation inductively coupled plasma mass spectrometry la icp ms co genetic brine and vapor inclusions from magmatic hydrothermal ore deposits and granitic intrusions show an excess of sulfur over ore metals as required for efficient ore mineral precipitation the results demonstrate that s cu and au are highly enriched in vapor like magmatic fluids implying that such low salinity fluids are the key agent for the formation of porphyry copper and epithermal gold deposits

fault charged mantle fluid contamination of united kingdom north sea oils insights from re os isotopes 187 os 188 os as expected from a kimmer idge clay formation source however oils from the viking graben with which the brent fi eld is associated and main east shetland basin display unradiogenic 187 os 188 os in this study we seek to demonstrate that these anomalous results are due to interaction with a mantle like fl uid that propagated through the main fault zone of the viking graben and east shetland basin this study enhances our understanding of the re os oil systematics and supports cur rent ideas regarding fault architecture crustal thinning and associated fl uid fl ow and interac tion in the north sea oil system abstract united kingdom north sea oils sourced from the kimmeridge clay formation contain unradiogenic 0 17 to 0 48 and radiogenic 1 04 to 3 34 187 os 188 os values the unra diogenic 187 os 188 os values are spatially associated with the main basin bounding faults of the viking graben and east shetland basin in contrast the radiogenic 187 os 188 os values are associated with north sea basins located farther away from the basin boundary faults we suggest that crustal thinning and strain localization within the viking graben and east shetland basin are suffi cient to have allowed basin bounding faults to propagate to suffi cient depth to act as conduits for mantle derived fl uids to interact with oil this hypothesis is sup ported by previous geochemical data for north sea oil fi elds furthermore we demonstrate the use of os isotopes as an important tracker of crustal scale fl uid dynamics and petroleum migration pathways in extensional basins

hydrothermal biogenic and seawater components in metalliferous black shales of the brooks range alaska synsedimentary metal enrichment in a carbonate ramp setting trace element and os isotope data for lisburne group metalliferous black shales of middle mississippian early chesterian age in the brooks range of northern alaska suggest that metals were sourced chiefly from local seawater including biogenic detritus but also from externally derived hydrothermal fluids these black shales are interbedded with phosphorites and limestones in sequences 3 to 35 m thick deposition occurred mainly on a carbonate ramp during intermittent upwelling under varying redox conditions from suboxic to anoxic to sulfidic deposition of the black shales at 335 ma was broadly contemporaneous with sulfide mineralization in the red dog and drenchwater zn pb ag deposits which formed in a distal marginal basin relative to the composition of average black shale the metalliferous black shales n 29 display large average enrichment factors 10 for zn 10 1 cd 11 0 and ag 20 1 small enrichments 2 10 are shown by v cr ni cu mo pd pt u se y and all rare earth elements except ce nd and sm a detailed stratigraphic profile over 23 m in the skimo creek area central brooks range indicates that samples from at and near the top of the section which accumulated during a period of major upwelling and is broadly correlative with the stratigraphic levels of the red dog and drenchwater zn pb ag deposits have the highest zn toc total organic carbon cu toc and tl toc ratios for calculated marine fractions no detrital component of these three metals average authigenic detrital free contents of mo v u ni cu cd pb ge re se as sb tl pd and au show enrichment factors of 4 3 103 to 1 2 106 relative to modern seawater such moderate enrichments which are common in other metalliferous black shales suggest wholly marine sources seawater and biogenic material for these metals given similar trends for enrichment factors in organic rich sediments of modern upwelling zones on the namibian peruvian and chilean shelves the largest enrichment factors for zn and ag are much higher 1 4 107 and 2 9 107 respectively consistent with an appreciable hydrothermal component other metals such as cu pb and tl that are concentrated in several black shale samples and are locally abundant in the red dog and drenchwater zn pb ag deposits may have a partly hydrothermal origin but this cannot be fully established with the available data enrichments in cr up to 7 8 106 are attributed to marine and not hydrothermal processes the presence in some samples of large enrichments in eu up to 6 1 107 relative to modern seawater and of small positive eu anomalies eu eu up to 1 12 are considered unrelated to hydrothermal activity instead being linked to early diagenetic processes within sulfidic pore fluids initial os isotope ratios 187os 188os calculated for a paleontologically based depositional age of 335 ma reveal moderately unradiogenic values of 0 24 to 0 88 for four samples of metalliferous black shale a proxy for the ratio of coeval early chesterian seawater is provided by initial 187os 188os 335 ma ratios of four unaltered black shales of the coeval kuna formation that average 1 08 nearly identical to the initial ratio of 1 06 for modern seawater evaluation of possible sources of unradiogenic os in the metalliferous black shales suggests that the most likely source was mafic igneous rocks that were leached by externally derived hydrothermal fluids this unradiogenic os is interpreted to have been leached by deeply circulating hydrothermal fluids in the kuna basin followed by venting of the fluids into overlying seawater we propose that metal bearing hydrothermal fluids that formed zn pb ag deposits such as red dog or drenchwater vented into seawater in a marginal basin were carried by upwelling currents onto the margins of a shallow water carbonate platform and were then deposited in organic rich muds together with seawater and biogenically derived components by syngenetic sedimentary processes metal concentration in the black shales was promoted by high biologic productivity sorption onto organic matter diffusion across redox boundaries a low sedimentation rate and availability of h2s in bottom waters and pore fluids

holocene glacier fluctuations and migration of neolithic yak pastoralists into the high valleys of northwest bhutan abstract here we present geomorphologic palaeoenvironmental and archaeo botanical data which elucidate the late pleistocene and holocene glacial history of the high mountain locked himalayan valleys in northwest bhutan and provide one of the earliest proofs of human activity yet known for the high himalaya range in this area difficult to access close linkage between climatic change glacier fluctuations and human migration patterns has been discovered glacier systems in the studied area are characterized by avalanching and debris mantled glacier snouts with the significant local influence of the indian summer monsoon causing decoupling of glacier responses from temperature changes but supporting the idea of monsoonal forcing geomorphologic mapping together with optically stimulated luminescence osl and radiocarbon dating of ice proximal sediments has been used to construct a local glacial chronology local ice stream networks developed during the early holocene ca 10 000 9000 a ago and during the early part of the mid holocene 6710 90 4680 155 cal a bp at which times there were ice advances of about 5 km from the modern glacier termini at such times the intensity of pro and periglacial processes would have intensified and ice dammed lakes were probably common as well rendering human colonization of the high valleys in northwest bhutan impossible an abrupt shift to dry climatic conditions on the tibetan plateau between 5000 and 4500 a bp coincided with glacial decay and the onset of morphodynamically stable conditions on the broad valley floors of the high valleys in this part of the himalaya palynological data suggest that the sudden disappearance of juniper and rhododendron pollen the immediate onset of pollen input from cereals confirmed by detailed sem analysis and a clear pattern of over grazing trampling and peat deterioration can be linked to human arrival in the valleys at ca 4280 130 cal a bp extensive charcoal horizons dating to 4745 250 and 4680 155 cal a bp are interpreted as evidence for human use of fire and forest clearances and agree spatially and temporally with the pollen based picture charcoal occurrences as old as 6710 90 cal a bp might be linked to yet earlier exploration of these himalayan valleys during phases of low glacial activity we provide an account of the colonization of these high valleys in response to glacial and monsoonal change and argue that the most likely founder societies come from the tibetan plateau where yak and barley based pastoralism and neolithic settlements are known to have existed since the mid holocene

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

consideration of the errors inherent in mapping historical glacier positions in austria from the ground and space 1893 2001 the historical record of in situ measurements of the terminus positions of the pasterze and kleines fleiskees glaciers in the eastern alps of austria is used to assess uncertainties in the measurement of decadal scale changes using satellite data topographic maps beginning in 1893 and satellite data from 1976 to 2001 were studied in concert with ground measurements to measure glacier changes ground measurements show that the tongue of the pasterze glacier receded f1150 m from 1893 to 2001 while satellite derived measurements using august 2001 landsat enhanced thematic mapper plus etm data registered to an 1893 topographic map show a recession of 1300 1800 m with an unknown error the measurement accuracy depends on the registration technique and the pixel resolution of the sensor when two satellite images are used when using topographic maps an additional source of error is the accuracy of the glacier position shown on the map between 1976 and 2001 landsat derived measurements show a recession of the terminus of the pasterze glacier of 479f136 m at an average rate of 19 1 m a 1 while measurements from the ground showed a recession of 428 m at an average rate of 17 1 ma 1 four meter resolution ikonos satellite images from 2000 and 2001 reveal a shrinkage of 22 096f46 m 2 in the pasterze tongue the nearby kleines fleiskees glacier lost 30 of its area between 1984 and 2001 and the area of exposed ice increased by 0 44f0 0023 km 2 according to landsat satellite measurements as more recent satellite images are utilized especially data that are geocoded the uncertainty associated with measuring glacier changes has decreased it is not possible to assess the uncertainty when an old topographic map and a satellite image are coregistered

first in situ record of decadal glacier mass balance 2003 2014 from the bhutan himalaya this study presents the first decadal mass balance record of a small debris free glacier in the bhutan himalaya where few in situ measurements have been reported to date since 2003 we have measured the mass balance of gangju la glacier which covers an area of 0 3km 2 and extends from 4900 to 5200ma s l using both differential gps surveys geodetic method and stake measurements direct method the observed mass balance ranged from 1 12 to 2 04mw e a 1 between 2003 and 2014 the glacier exhibited much greater mass loss than neighbouring glaciers in the eastern himalaya and southeastern tibet which are expected to be sensitive to climate change due to the monsooninfluenced humid climate observed mass balance profiles suggest that the equilibrium line altitude has been higher than gangju la glacier since 2003 implying that the entire glacier has experienced net ablation for at least the past decade

planimetric and volumetric glacier changes in the khumbu himal nepal since 1962 using corona landsat tm and aster data multitemporal space imagery from 1962 corona kh 4 1992 landsat tm 2001 and 2005 terra aster was used to investigate the glacier changes in the khumbu himal nepal the ice coverage in the investigation area decreased by about 5 between 1962 and 2005 with the highest retreat rates occurring between 1992 and 2001 the debris coverage increased concomitantly with the decrease in total glacier area the clean ice area decreased by 10 digital terrain model dtm generation from the early corona kh 4 stereo data in this high relief terrain is time consuming and the results still contain some elevation errors however these are minor in the snow free areas with gentle slopes thus comparison of the surfaces of the debris covered glacier tongues based on the corona dtm and an aster dtm is feasible and shows the downwasting of the debris covered glaciers the highest downwasting rates more than 20 m 0 5 m a 1 can be found near the transition zone between the active and the stagnant glacier parts of the debris covered glacier tongues the downwasting is lower but still evident in the active ice areas and at the snout with thick debris cover all investigated debris covered glaciers in the study area show similar behaviour the estimated volume loss for the investigated debris covered glacier tongues is 0 19 km 3

glacier changes on the tibetan plateau derived from landsat imagery mid 1970s 2000 13 glacier area changes on the tibetan plateau were studied in different drainage basins based on landsat satellite images from three epochs 263 in the mid 1970s 150 in 1999 2002 and 148 in 2013 14 three mosaics m1976 m2001 and m2013 with minimal cloud and snow cover were constructed and the uncertainty due to each epoch having a finite span was accounted for glacier outlines tpg1976 tpg2001 and tpg2013 were digitized manually with guidance from the srtm dem v4 1 and google earth imagery to achieve complete multi temporal coverage in a reasonable time only debris free ice was delineated area mapping uncertainty was evaluated at three study sites mount qomolangma everest mount naimona nyi mount geladandong where the largest differences between present and earlier measurements were within similar to 4 area differences with previous inventories ranged from 19 6 tpg1976 minus the first chinese glacier inventory to 3 6 and 1 1 tpg2013 and tpg2001 respectively minus the second chinese glacier inventory while the difference tpg2001 minus the gamdam glacier inventory was 10 4 glacier area on the plateau decreased from 44 366 2827 km 2 1 7 of the study area in the 1970s to 42 210 1621 km2 in 2001 and 41 137 1616 km2 in 2013 shrinkage was faster in external drainage basins of the southeast than in the interior basins of the northwest from a maximum of 0 43 a 1 1 60 a 1 during 19942013 in the mekong catchment down to a minimum of 0 12 a 1 in the tarim interior drainage

topographic controls on the debris cover extent of glaciers in the eastern himalayas regional analysis using a novel high resolution glacier inventory abstract to better understand the influence of topography on the formation of himalayan debris covered glaciers we manually digitized 5301 glaciers covering an area of 5691 893 km2 from high resolution advanced land observing satellite imagery and identified 842 debris covered glaciers with a debris covered area of 3839 753 km2 this estimation of the debris covered area of these glaciers is a novel approach in the eastern himalayas we investigated the relationship between the debris covered area and the corresponding potential debris supply pds slopes for the debris covered glaciers across the region the pds slopes on the southern side show better correlation with their debris covered area formation than those situated on the northern side of the himalayan barrier with this correlation weakening toward the western massifs further investigation showed that pds slopes oriented se to w exert a stronger control on the formation of debris covered areas which is related to the diurnal freeze thaw cycle on the southern slope of the mountain barrier

copper arsenic decoupling in an active geothermal system a link between pyrite and fluid composition abstract over the past few decades several studies have reported that pyrite hosts appreciable amounts of trace elements which commonly occur forming complex zoning patterns within a single mineral grain these chemical zonations in pyrite have been recognized in a variety of hydrothermal ore deposit types e g porphyry cu mo au epithermal au deposits iron oxide copper gold carlin type and archean lode au deposits among others showing in some cases marked oscillatory alternation of metals and metalloids in pyrite growth zones e g of cu rich as au ag depleted zones and as au ag rich cu depleted zones this decoupled geochemical behavior of cu and as has been interpreted as a result of chemical changes in ore forming fluids although direct evidence connecting fluctuations in hydrothermal fluid composition with metal partitioning into pyrite growth zones is still lacking in this study we report a comprehensive trace element database of pyrite from the tolhuaca geothermal system tgs in southern chile a young and active hydrothermal system where fewer pyrite growth rims and mineralization events are present and the reservoir fluid i e ore forming fluid is accessible we combined the high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capacity of secondary ion mass spectrometry sims in a suite of pyrite samples retrieved from a 1 km drill hole that crosses the argillic 20 450 m and propylitic 650 1000 m alteration zones of the geothermal system we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and base and heavy metals e g cu co ni pb in pyrite at the tgs are significant among the elements analyzed as and cu are the most abundant with concentrations that vary from sub ppm levels to a few wt i e up to 5 wt as 1 5 wt cu detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrites from the tgs are characterized by chemical zoning where the studied elements occur in different mineralogical forms arsenic and co occur as structurally bound elements in pyrite cu and au in pyrite can occur as both solid solution and submicron sized particles of chalcopyrite and native au or au tellurides respectively pyrites from the deeper propylitic zone do not show significant zonation and high cu co as concentrations correlate with each other in contrast well developed zonations were detected in pyrite from the shallow argillic alteration zone where cu co rich as depleted cores alternate with cu co depleted as rich rims these microanalytical data were contrasted with chemical data of fluid inclusions in quartz and calcite veins high cu as ratios and borehole fluid low cu as ratios reported at the tgs showing a clear correspondence between cu and as concentrations in pyrite forming fluids and chemical zonation in pyrite these observations provide direct evidence supporting the selective partitioning of metals into pyrite as a result of changes in ore forming fluid composition most likely due to separation of a single phase fluid into a low density vapor and a denser brine capable of fractionating cu and as