the iberian type of volcano sedimentary massive sulphide deposits the iberian pyrite belt located in the sw iberian peninsula contains many paleozoic giant and supergiant massive sulphide deposits including the largest individual massive sulphide bodies on earth total ore reserves exceed 1500 mt distributed in eight supergiant deposits 100 mt and a number of other smaller deposits commonly with associated stockwork mineralizations and footwall alteration haloes massive sulphide bodies largely consist of pyrite with subordinated sphalerite galena and chalcopyrite and many other minor phases although substantial differences occur between individual deposits both in mineral abundance and spatial distribution these deposits are considered to be volcanogenic roughly similar to volcanic hosted massive sulphides vhms however our major conclusion is that the iberian type of massive sulphides must be considered as a vhms sub type transitional to shms

an experimental study of the mechanism of coal and gas outbursts in the tectonic regions abstract to reveal the mechanism of coal and gas outbursts in tectonic regions a gas driven multi physics coal and gas outbursts experimental apparatus was developed based on the experimental results the damage characteristics and the mechanism of outbursts of tectonic raw coal under different gas pressures and stress conditions are quantitatively investigated the experimental results show that the damage to coal samples increases with the increase in gas pressure when the gas pressure is 2 0 mpa the damage to the coal sample tends to decrease with increases in the confining and axial stress when the gas pressure exceeds the critical value of 2 2 mpa a strong outburst phenomenon occurs in which the pulverized coal is ejected and the outbursts cavern is blocked however when the gas pressure is 2 4 mpa the coal samples are completely broken down after the tests and the outbursts intensity becomes larger as the axial stress or the confining stress increases in addition the evolution of gas pressure and the degree of fragmentation of coal samples are also discussed quantitatively in the process of coal and gas outbursts the present study of the mechanism of coal and gas outbursts in the tectonic regions is helpful for the assessment and forecasting of potential outbursts

modelling of outbursts at 26 colliery glace bay nova scotia part 2 proposed outburst mechanism and model abstract the outbursts experienced at 26 colliery originated from within sandstone river channels just above the coal seam the outburst mechanism proposed here can be used to model the outbursts experienced at this mine quantitatively the mechanism treats an outburst as a series of instantaneous static events driven by tensile failures within the rock mass around a spalling cavity outbursts may terminate simply due to stress re distribution caused by the changing shape of the spalling cavity if a stable shape is achieved alternatively spalling could continue indefinitely unless it is terminated by a change in geology the two main factors affecting the occurrence of an outburst are the gas pressure and the tensile strength of the rock containing the gas the final stable shape of the cavity when not geologically influenced is directly dependent on the in situ stress field sensitivity analyses illustrate the above influences

structure and contents of a new geomorphological gis database linked to a geomorphological map with an example from liden central sweden this paper presents the structure and contents of a standardised geomorphological gis database that stores comprehensive scientific geomorphological data and constitutes the basis for processing and extracting spatial thematic data the geodatabase contains spatial information on morphography morphometry hydrography lithology genesis processes and age a unique characteristic of the gis geodatabase is that it is constructed in parallel with a new comprehensive geomorphological mapping system designed with gis applications in mind this close coupling enables easy digitalisation of the information from the geomorphological map into the gis database for use in both scientific and practical applications the selected platform in which the geomorphological vector raster and tabular data are stored is the esri personal geodatabase additional data such as an image of the original geomorphological map dems or aerial orthographic images are also included in the database the structure of the geomorphological database presented in this paper is exemplified for a study site around liden central sweden

mineralization of an intra oceanic arc in an accretionary orogen insights from the early silurian honghai volcanogenic massive sulfide cu zn deposit and associated adakites of the eastern tianshan nw china the honghai volcanogenic massive sulfide vms deposit occurs in the kalatage inlier of the dananhu haerlik arc eastern tianshan in the southern altaids the deformed deposit hosted in a suite of early paleozoic basic to intermediate volcanic volcaniclastic and sedimentary rocks consists of lenticular massive to semimassive and sulfide silicate stockwork orebodies the orebodies are characterized by zoning of metallogenic elements and sulfide minerals outward from a central stockwork zone as follows fe cu fe cu zn au ag cu zn fe zn cu au ag zn cu and fe cu zn a typical vms hydrothermal alteration zone that formed around the foot of the massive orebodies is several times larger than the lenticular massive orebody the hydrothermally altered rocks contain sericite chlorite and epidote zones from the core outward re os and argon dating of pyrite and sericite shows that the honghai vms deposit formed in the early silurian 436 2 ma and was deformed in the early devonian 410 4 ma this is the first documented early paleozoic vms deposit in the eastern tianshan our multidisciplinary data indicate that the honghai cu zn deposit formed in an immature nascent island arc where early tholeiitic lavas evolved into transitional basic andesitic volcanic rocks and calc alkaline intrusions with relatively high epsilon nd t values 6 2 8 4 and low sr 87 sr 86 i ratios 0 70412 0 70541 the sr nd pb s isotopic and geochemical data suggest that the ore forming melts started in mantle derived volcanic rocks and deep subvolcanic intrusions and some alteration was influenced by seawater the deposit formed in a high level subvolcanic intrusion driven by sub seafloor co2 rich nacl cacl2 h2o hydrothermal fluids temperatures 99 377 degrees c salinities 6 18 nacl equivalent circulating in active extensional faults in a submarine caldera extension of the immature nascent intra oceanic arc was one of the important factors that controlled the development and preservation of the vms deposit future work will benefit from this improved understanding of the vms deposits formed in immature nascent intra oceanic arcs especially in early paleozoic island arcs in the eastern tianshan in the southern altaids

alteration characteristics of the archean golden grove formation at the gossan hill deposit western australia induration as a focusing mechanism for mineralizing hydrothermal fluids the archean golden grove formation is a 550 m thick rhyodacitic tuffaceous volcaniclastic succession that hosts the cu zn rich gossan hill volcanic hosted massive sulfide vhms deposit in the yilgarn craton western australia the golden grove formation consists of volcanic quartz and altered pumice and shards which were deposited during successive episodes of subaqueous mass flow coherent volcanics are absent from the golden grove formation at gossan hill but form the main rock type in the hanging wall scuddles formation a massive dacite dome that overlies its volcanic feeder dike is inferred to occupy a synvolcanic structure that focused mineralizing fluids during the formation of the gossan hill deposit the gossan hill deposit consists of two stratigraphically separate ore zones interconnected by stockwork the cu rich lower ore zone and the zn rich upper ore zone occur in the middle and upper parts of the golden grove formation respectively podiform zones of massive magnetite occur in the cu rich ore zone where the formation of magnetite predates massive sulfide the asymmetry of massive sulfide massive magnetite and alteration zones at the gossan hill deposit attest to synvolcanic structural control during mineralization the principal lithofacies of the golden grove formation are sandstone and pebble breccia which have a regionally extensive quartz fe rich chlorite and lesser muscovite alteration at gossan hill this alteration has resulted in near complete replacement of tuffaceous components causing substantial chemical modification of the primary lithologies quartz chlorite muscovite alteration is characterized by severe k2o na2o and cao depletion with rocks consisting principally of sio2 feo al2o3 and mgo along a quartz chlorite mixing trend widespread preservation of pumice and shard volcanic textures within the golden grove formation indicates that quartz chlorite muscovite alteration occurred soon after or possibly during sedimentation the absence of diagenetic compaction textures further suggests induration of the succession during this early alteration stage with the tuffaceous succession largely sealed from the texturally destructive effects of subsequent hydrothermal alteration except where mineralizing fluids were locally channeled along synvolcanic feeder conduits local intense hydrothermal alteration zones surround the gossan hill deposit and overprint earlier quartz chlorite muscovite alteration these local alteration zones have the same extent as the sulfide vein envelope and represent hydrothermal alteration formed during sulfide magnetite mineralization intense fe rich chlorite ankerite siderite alteration occurs as a strata bound envelope around massive magnetite cu rich veins and massive sulfide in the lower ore zone this chlorite rich alteration has strong feo and mgo enrichment with minor chloritoid and andalusite that reflect intense acid leaching during hydrothermal alteration iron chlorite ankerite siderite alteration grades upward into discordant to strata bound intense quartz alteration intense quartz alteration forms an envelope around zn rich veins and massive sulfide in the stockwork and upper ore zone the trend from fe chlorite ankerite siderite to quartz alteration toward the top of the deposit is consistent with the cooling of hydrothermal mineralizing fluids nearing the sea floor rhyodacite and dacite volcanics of the hanging wall scuddles formation have a pervasive muscovite calcite alteration muscovite calcite alteration led to na2o depletion and cao and k2o enrichment associated with burial of the gossan hill mineralizing system we propose that the gossan hill sulfide magnetite vhms deposit formed during an evolving archean hydrothermal system that began as part of a regional scale low temperature seawater convection alteration system initially this system caused extensive replacement of the golden grove formation by quartz and fe chlorite muscovite a process that sealed and indurated the volcaniclastic rocks by infilling of primary porosity and permeability structures due to subsequent impermeability of the host rock succession later and hotter mineralizing fluids that generated alteration and massive magnetite and sulfide at the gossan hill deposit were constrained to and focused upward along a synvolcanic feeder structure

the archean cu zn magnetite rich gossan hill volcanic hosted massive sulfide deposit western australia genesis of a multistage hydrothermal system the gossan hill volcanic hosted massive sulfide vhms deposit is an archean cu zn magnetite rich deposit located in the warriedar fold belt of the yilgarn craton western australia the deposit is hosted by redeposited rhyodacitic tuffaceous volcaniclastics of the golden grove formation and is overlain by felsic volcanic rocks of the scuddles formation the deposit consists of two separate subvertical ore zones the stratigraphically lower cu rich ore zone 7 0 mt 3 4 cu is strata bound and varies from podiform massive pyrite chalcopyrite pyrrhotite magnetite to sheetlike massive magnetite carbonate chlorite talc the upper zn cu ore zone 2 2 mt 11 3 zn 0 3 cu 1 5 g t au and 102 g t ag contains strata bound massive sphalerite pyrite chalcopyrite that overlies discordant moundlike massive pyrite pyrrhotite chalcopyrite magnetite sulfide stockwork connects the upper and lower ore zones metal zonation varies from cu au in the lower ore zone to zn cu at the base of the upper ore zone which grades upward and laterally to zn ag au cu pb multiphase deformation and greenschist facies metamorphism overprint the deposit the relationship between host rocks and sulfide indicates that mineralization was broadly codepositional with sedimentation of the golden grove formation however gradational and interdigitating contacts between these volcaniclastic rocks and magnetite support the formation of massive magnetite by subsea floor replacement sulfides replace and vein the massive magnetite with inferred synchronous formation of the upper and lower sulfide ore zones although these sulfide ore zones formed mainly by subsea floor replacement stratiform hydrothermal chert sulfide sediment layers within and adjacent to the upper zn rich ore zone attest to some local exhalation the thickest development of massive magnetite massive sulfide and stringer stockwork occurs in the north of the deposit and supports a common feeder during massive magnetite and sulfide formation furthermore local chlorite quartz hydrothermal alteration massive magnetite massive sulfide and stockwork all form asymmetric zones that thin southward these attributes indicate strong synvolcanic structural control during mineralization the relict synvolcanic growth structure is obscured and probably occupied and by a dacite dome of the hanging wall scuddles formation thermodynamic considerations suggest that massive magnetite and sulfide formed from similar high temperature 300 degrees celsius slightly acidic low fo2 hydrothermal fluids massive magnetite formed from h2s poor fluids whereas massive sulfide formed from relatively rich h2s fluids physicochemical changes associated with interaction between upwelling h2s bearing fluids and preexisting massive magnetite may have resulted in the subsea floor precipitation of sulfide in the lower cu rich ore zone the gossan hill vhms deposit represents a multistage hydrothermal system within an environment characterized by rapid volcaniclastic sedimentation and changing structural and magmatic processes the six main stages were as follows 1 initiation of the hydrothermal system 2 sedimentation metasomatism and progressive heating of convecting fluids 3 deposition of massive magnetite from h2s poor fluids by subsea floor replacement above a buried synvolcanic conduit 4 structural reactivation tapping deeper h2s and metalbearing fluids 5 subsea floor replacement and minor exhalative sulfide mineralization with 6 burial and preservation of the deposit resulting from proximal felsic volcanism

automated recognition of valley heads from digital elevation models applications of landform recognition in map making geographical information systems and in improving the storage and representation of earth surface information are described reasons are given for the use of digital elevation models for landform recognition increasing availability of data easier data integration and automation of landform recognition an automated technique for recognizing valley heads from digital elevation models is presented the technique has been developed for valley head recognition because valley heads are known locations of geomorphological activity and because areal features have been largely ignored in the automated landform recognition literature the problem of valley head recognition is divided into valley head location and valley head delineation and the technique is developed using a dem representing a simple artificial landscape two methods are given for valley head location in the first valley heads are located at valley ends in the second valley heads are located at cells which would have water flowing into them from many directions if water was flowing over the terrain the latter method locates all the valley heads on the artificial landscape the cells locating valley heads are iteratively grown to adjacent cells that are concave in plan and not flat to delineate the valley head at best 82 per cent valley head cells on the artificial landscape are correctly recognized with a 43 per cent commission error the method is tested on real data where it is less successful because of the variability of real landscapes and the inadequacy of the methods chosen for valley network delineation machine learning of thresholds and a method involving inspection of profiles across a dem cell are suggested as methods to improve the automated valley head recognition technique

the glacier creek cu zn vms deposit southeast alaska an addition to the alexander triassic metallogenic belt the glacier creek volcanogenic massive sulfide vms deposit alaska is hosted within late triassic oceanic back arc or intraarc rift related bimodal volcanic rocks of the allochthonous alexander terrane known as the alexander triassic metallogenic belt the alexander triassic metallogenic belt is host to the world class greens creek zn pb ag vms deposit near juneau in the south and the giant windy craggy cu co vms deposit in british columbia about 250 km to the north the glacier creek deposit located 80 km southeast of windy craggy consists of four tabular massive sulfide lenses within a bimodal mafic volcaniclastic and rhyolitic sequence the mineralization hosting stratigraphy is folded by a deposit scale anticline and offset by a thrust fault near the axial surface of the fold a resource of 8 13 mt has been inferred from drilling with grades of 1 41 cu 5 25 zn 0 15 pb 0 32 g t au and 31 7 g t ag six main mineralization types are recognized dominated by massive barite sphalerite pyrite which is replaced at the base and center of the main lenses by massive and semimassive chalcopyrite pyrite quartz the flanks and tops of the lenses are carbonate rich and consist of interbedded calcite dolomite barite and sulfide resedimented massive barite sulfide and mineralized massive carbonate rocks tuffaceous hydrothermal sediment with a distinct positive eu anomaly overlies the massive sulfide pyrrhotite and chalcopyrite in stringers constitute the main feeder zone stringer style sphalerite pyrite mineralization occurs above and below the lenses fe poor sphalerite is dominant throughout the lenses whereas fe rich sphalerite occurs at the stratigraphic top and bottom of the lenses in pyrrhotite rich zones galena tennantite tetrahedrite and arsenopyrite are the most important trace minerals within massive barite sphalerite pyrite mineralization which is generally enriched in sb hg and tl mineralization related gangue minerals include barite quartz barian muscovite calcite dolomite albite chlorite hyalophane and celsian four types of alteration are recognized in the dominantly basaltic host rocks pervasive muscovite rich alteration quartz pyrite alteration associated with sulfide stringers stratabound carbonate bearing alteration and background epidote bearing alteration mass balance calculations indicate gains of s fe si and k with coincident losses of ca na and mg in all of the alteration types trace elements tl sb hg ba zn cu and as were added to the rocks whereas sr was lost short wavelength infrared swir spectroscopy shows an increase in the wavelength of the aloh absorption feature toward mineralization at a scale of 30 to 50 m coincident with a general decrease in the na k and al and increase in the fe mg and ba content of muscovite the glacier creek deposit is transitional in character between greens creek which is more zn pb and precious metal rich and the windy craggy deposit which is more cu and co rich reflecting differences in the basement rocks and depositional settings within the alexander triassic metallogenic belt mineral chemical studies and sulfur isotope data suggest that the glacier creek deposit formed under initially oxidized and sulfate rich conditions that evolved to more reduced conditions in the latest stages of mineralization the abundant argillite and presence of hyalophane rather than barite in the immediate hanging wall of the deposit may be an indication of a deepening basin and development of local anoxia similar to greens creek

a new sulphur isotopic study of some iberian pyrite belt deposits evidence of a textural control on sulphur isotope composition the sulphide deposits of the iberian pyrite belt ipb represent an ore province of global importance our study presents 113 new sulphur isotope analyses from deposits selected to represent the textural spectrum of ores measured 34s values range from 26 to 10 mostly for massive and stockwork ores in agreement with data previously published in situ laser 34s analyses reveals a close correlation of 34s with texture primary diagenetic textures are dominated by relatively low 34s 8 to 2 whereas stockwork feeder textures are dominated by higher 34s 3 to 5 intermediate textures mainly coarse textures in stratiform zones have intermediate 34s although they are mostly dominated by the high 34s component rare barite has a homogeneous 34s around 18 which is consistent with direct derivation from lower carboniferous seawater sulphate a dual source of sulphide sulphur in the ipb deposits has been considered a hydrothermal source derived from reduction of coeval seawater sulphate in the convective systems is represented by sulphide in the feeder zones here variations in 34s are caused by variations in the extent of the sulphate reduction which governs the so4 h2s ratio the second end member was derived from the bacterial reduction of coeval seawater sulphate at or near the surface as reflected in the primary textures a distinct geographical variation in 34s and texture from sw more bacteriogenic and primary textures to ne more hydrothermal textures and 34s which reflects a variation in the relative input of each source was likely controlled by local geological environments given that the sulphur isotope characteristics of the ipb deposits are unlike most vms and kuroko deposits and noting the dominance of a mixed reduced sedimentary and volcanic environment we suggest that the ipb could represent an ore style which is intermediate between volcanic and sedimentary hosted massive sulphide types

automated mapping of land components from digital elevation data an algorithm for automating the mapping of land components from digital elevation data is described land components are areas of relatively uniform slope and aspect and often correspond with ridge crests shoulders head slopes back slopes or foot slopes aspect regions which generally span from stream to ridge are first identified by generalizing an aspect map derived from digital elevation data the aspect regions are then split successively into land components by grouping pixels above or below an automatically determined contour of elevation or distance from stream the contour approximates a slope break the land components mapped in this way give a complete polygonization of a hilly landscape and are a reasonable approximation of manually mapped land components

alteration zonation and short wavelength infrared swir characteristics of the honghai vms cu zn deposit eastern tianshan nw china abstract the honghai vms cu zn deposit is located in the dananhu tousuquan arc eastern tianshan northwestern china orebodies of the honghai deposit are buried 300 m underground and hosted by the middle ordovician upper silurian daliugou formation felsic to intermediate volcanic sedimentary rocks at the footwall and hanging wall of the massive sulfide lens intensive and pervasive phyllic alterations were found detailed drill core logging petrographic study and electron microprobe analyses had delineated six alteration mineralization zones namely from top to bottom zone i chlorite albite white mica carbonate ii epidote chlorite albite white mica carbonate iii quartz white mica pyrite iv massive sulfide v chlorite pyrite white mica and vi chlorite quartz white mica our new data supported the sub seafloor replacement influence for the honghai vms deposit as evidenced by the presence of 1 sulfide breccias in the immediate host rocks 2 rapid emplacement of host rocks 3 strong phyllic alteration in the immediate hanging wall 4 replacement textures of the massive sulfides 5 barite as gangue minerals moreover intensive chlorite and epidote alterations and vein mineralization are present in the hanging wall which are comparable with porphyry related propylitic alteration besides different mineralogy and mineral chemistry are present between chlorites from the hanging wall and footwall at honghai which probably suggested porphyry style alteration and mineralization overprinting at honghai short wavelength infrared swir spectral analysis had identified mainly white mica chlorite and epidote and minor montmorillonite calcite gypsum kaolinite and prehnite the wavelengths of the aloh absorption feature for white mica range from 2194 to 2221 nm suggesting compositions from paragonite through muscovite to phengite the wavelengths of feoh absorption feature for chlorite range from 2249 to 2261 nm indicating compositions from mg rich to fe rich chlorite according to swir measurements and electron microprobe analyses empa areas proximal to the massive sulfides are characterized by short wavelength of the aloh absorption feature and high alvi content of white mica petrography and empa showed that chlorite in the ore proximal zones are more mg rich than that in ore distal zones these findings indicated high temperature for the white mica formation and more seawater influx during the chlorite formation in areas near the massive sulfides this study suggested that swir analysis supported by petrographic study and empa can serve as an effective tool in alteration mapping and mineral geochemical variations are potential deposit scale exploration vectoring tools

random forest with semantic tie points for classifying landforms and creating rigorous shaded relief representations abstract in this study we tested random forest rf with semantic tie points to classify discrete landforms which would be ultimately useful for increasing the accuracy of shaded relief representations we therefore focused our efforts on the following landforms rock outcrops screes alluvial fans and low relief areas a characteristic of rf which makes it a good algorithm for geomorphological mapping is its ability to generate thousands of classification trees each tree provides a classification and the value classified by the majority of the trees is the final output of the algorithm furthermore having multiple classifications provides a measure of uncertainty this is very important because it gives practitioners an idea of areas where the method is less accurate which would require more effort in terms of sampling or surveying this method was applied in two mountainous areas of switzerland the first where we trained and calibrated it and the second where we used it for classification the results were validated using existing geomorphological maps and they show that this method can obtain good training accuracy with a relatively small starting dataset moreover both calibration and classification present a percentage of agreement with existing geomorphological maps of over 70 some geomorphological classes alluvial fans and screes present a classification accuracy that is lower than the calibration which is in line with previous tests found in the literature however for other classes i e rock outcrops and low relief areas the accuracy increases suggesting that this method can be employed extensively and relatively securely for these landforms

lithostratigraphic hydrothermal and tectonic setting of the boundary volcanogenic massive sulfide deposit newfoundland appalachians canada formation by subseafloor replacement in a cambrian rifted arc the boundary volcanogenic massive sulfide vms deposit 0 5 mt 3 5 cu 4 zn 1 pb 34 0 g t ag in the tally pond group central newfoundland represents one of the best preserved subseafloor replacement style vms deposits in the northern appalachian orogen the deposit is hosted within a late cambrian 510 ma volcanic sequence consisting predominantly of rhyolitic flows and associated volcaniclastic rocks footwall strata are dominated by rhyolitic lapilli tuff tuffs lesser rhyolite flows and in situ rhyolite breccias the hanging wall consists of massive quartz bearing flow banded lobe and breccia facies rhyolite the deposit occurs at and below the contact between these two units and comprises pyrite chalcopyrite and lesser sphalerite and other minerals massive mineralization contains abundant clasts of the surrounding host rocks including chlorite sericite quartz altered rhyolite lapilli and ash hydrothermally altered rocks consist of variably intense chlorite with lesser sericite and quartz chlorite alteration occurs in a discordant geometry likely representing hydrothermal upflow zones and chlorite sericite quartz occur as blankets that are parallel to the volcanic stratigraphy likely representing alteration associated with replacement the hanging wall rhyolite flows also contain moderate to intense pervasive quartz and sericite alteration both the hanging wall and footwall are characterized by strong na2o sr depletions k2o mgo fe2o3 ba enrichments high alteration index values e g ba sr chlorite carbonate pyrite index ccpi alteration index ai and enrichments in base metals and volatile metals e g cu zn pb hg the presence of abundant remnant wall rock and host rock clasts within the ore intricate sulfide replacement of laminated porous tuff and sand dikes replacement fronts in host lithofacies and intense alteration in both the footwall and hanging wall where the hanging wall is preserved are all features consistent with formation of the bulk of the boundary deposit via subseafloor replacement the deposit likely formed as a result of cooling of metal bearing hydrothermal fluids mixing with ambient seawater and pore water entrained seawater within the volcanic rocks at a permeability interface between young unlithified highly permeable footwall volcaniclastic rocks and relatively impermeable hanging wall rhyolitic flows in our model this permeability boundary was an important feature that promoted subseafloor replacement within the deposit immobile element systematics of rhyolitic rocks from the boundary deposit lack major differences in primary petrochemistry between hanging wall and footwall strata all rocks from the deposit area are subalkalic with transitional zr y ratios 2 8 4 5 la sm ratios 1 normalized to upper crust and primitive mantle normalized signatures with slightly light rare earth element lree enriched patterns with flat heavy ree hree and negative nb ti and eu anomalies these geochemical features coupled with existing nd pb isotope data zircon inheritance patterns and geologic information are consistent with rhyolitic rocks at the boundary deposit having formed by re melting of arc basement with continental crust or recycled continental crust present in the source region it is likely that the deposit and its associated rhyolitic host rocks formed within a cambrian continental or pericontinental rifted arc along the margin of ganderia within the iapetus ocean

ambient redox and hydrothermal environment of the wolverine volcanogenic massive sulfide deposit yukon insights from lithofacies and lithogeochemistry of mississippian host shales the wolverine volcanogenic massive sulfide vms deposit is a polymetallic felsic siliciclastic deposit hosted by 352 to 347 ma volcanic and sedimentary rocks of the yukon tanana terrane yukon canada shales are located at various stratigraphic levels and in various mineralized zones within the wolverine deposit area e g fisher puck and sable zones shales present along the mineralized horizon near the immediate hanging wall and footwall were deposited under anoxic conditions e g low mn anoxic v cr mo u systematics whereas in the stratigraphically deeper footwall and uppermost hanging wall the redox signatures imply deposition under suboxic to oxic conditions the mo u systematics of the shales suggest that during the time of sulfide mineralization the ambient basin was periodically euxinic with aqueous h2s present in the water column that this h2s contributed to the sulfur budget of the deposit furthermore the mo u and corg ni systematics favor deposition in a restricted basin i e nutrient trap where restriction of the water column led to h2s formation via sulfate reduction associated with excess organic carbon preservation there is also evidence of a progressive shift upward in the stratigraphy to more oxygenated conditions in the uppermost hanging wall the shift from euxinic to oxic suboxic conditions is consistent with regional tectonic models that indicate a change from rifting during wolverine deposit formation where the basin was partially restricted with minimal circulation i e restricted depocenter to an incipient back arc basin accompanied by extension and likely ingress of oxygenated seawater the rare earth element and y rey systematics in wolverine shales illustrate that proximal to the mineralized horizon shales have higher y ho 27 and ce ce 1 and negative ce anomalies indicative of oxygenated seawater the ce ce values in the wolverine shales have an inverse correlation with p2o5 content and suggest partial control by detrital apatite it is envisioned that apatite formed in the upper oxygenated portion of the water column inherited the ree signature of oxygenated seawater i e ce ce 1 and was subsequently deposited into deeper waters as detrital grains the ce ce and y ho also correlate with co2 and carbonate content of the shales moreover the shales that have the strongest rey signature of oxygenated seawater also coincide with the strongest euxinic signatures this paradox can be reconciled by enhanced deposition of apatite coincident with deposit formation coupled with a late hydrothermal overprint on the shales from low temperature co2 rich oxygenated hydrothermal fluids i e high y ho and ce ce 1 in a vent proximal environment this model is consistent with the geology stratigraphy and hydrothermal alteration in the immediate footwall and hanging wall of the deposit prospective shales in the wolverine basin and similar sediment rich hydrothermal basins globally should exhibit evidence for deposition under anoxic conditions i e mn 1 000 ppm high v mo u uef moef hydrothermal fe al mn systematics i e high fe al and evidence for hydrothermal alteration i e high ciw values high molar sericite and chlorite identification of samples having these features is useful in targeting prospective vms environments in shale dominated successions and potential targets within shale rich basins

geochemistry and paleotectonic setting of felsic volcanic rocks in the finlayson lake volcanic hosted massive sulfide district yukon canada the finlayson lake volcanic hosted massive sulfide vhms district represents one of canada s most recent vhms discovery regions with 34 million metric tons mt of massive sulfide mineralization found since the mid 1990s felsic volcanic rocks are associated with three units the fire lake unit the kudz ze kayah unit and the wolverine succession significant accumulations of polymetallic felsic vhms deposits kudz ze kayah gp4f and wolverine have only been discovered in the kudz ze kayah unit and wolverine succession to date in the hanging wall of the money creek thrust felsic volcanic and high level intrusive rocks in the fire lake unit have calc alkalic and tholeiitic affinities with low high field strength element hfse contents and intermediate zr sc 9 4 43 4 and zr tio2 254 864 ratios these rocks are interlayered with mafic rocks with arc geochemical signatures to date devoid of significant vhms mineralization and represent bimodal magmatism within an evolving devonian mississippian continental arc system the kudz ze kayah unit in the footwall of the money creek thrust stratigraphically overlies the fire lake unit and consists of felsic volcanic rocks with high hfse contents within plate a type signatures and high zr sc 15 3 190 3 and zr tio2 630 2 185 ratios the kudz ze kayah unit felsic rocks are crosscut and overlain by alkalic mafic rocks are associated with abundant carbonaceous sedimentary rocks and represent magmatism within a devonian mississippian ensialic back arc rift basin environment the wolverine succession unconformably overlies the kudz ze kayah unit felsic rocks below the wolverine deposit have geochemical attributes similar to the kudz ze kayah unit with high hfse contents within plate a type signatures and high zr sc 29 9 84 2 and zr tio2 391 1 220 ratios in contrast aphyric rhyolite flows in the hanging wall of the deposit have much lower hfse contents and the lowest zr sc 3 5 27 7 and zr tio2 181 591 ratios in the district all the felsic rocks of the wolverine succession are interlayered with abundant carbonaceous sedimentary rocks and are overlain by midocean ridge basalt morb like basaltic rocks the wolverine succession is interpreted to have formed within an early mississippian ensialic back arc basin environment that eventually evolved to sea floor spreading the variation in the hfse budgets of the felsic rocks of the finlayson lake district likely reflects variations in the source and or temperature of crustal melting in particular felsic rocks of the fire lake unit have higher nb ta and lower ti sc ratios than other volcanic rocks in the district suggesting possible derivation from mafic crustal sources and or lower crustal fusion temperatures the kudz ze kayah unit and footwall rocks to the wolverine deposit are inferred to have formed from high temperature partial melting of continental crust the hanging wall aphyric rhyolites from the wolverine deposit may have formed from either lower temperature continental crustal melting or may have been derived from the mixing of hfse depleted n morb mafic magmas and evolved continental crust polymetallic felsic volcanic associated vhms deposits within the finlayson lake district are preferentially associated with hfse enriched felsic rocks with high zr sc 15 3 190 3 and zr tio2 391 2 105 ratios the hfse and rare earth element ree systematics of vhms associated felsic rocks of the finlayson lake district are different from prospective felsic rocks from archean vhms environments in the superior province and are displaced toward higher zr y and la ybn ratios their hfse and ree systematics are similar to many phanerozoic vhms environments in particular those at least partially to fully underlain by evolved continental crust the geochemical differences between the felsic rocks of the finlayson lake district and those from archean vhms environments most likely reflect differences in the substrates from which the felsic rocks were derived e g evolved versus juvenile

integration of spectral spatial and morphometric data into lithological mapping a comparison of different machine learning algorithms in the kurdistan region ne iraq abstract lithological mapping in mountainous regions is often impeded by limited accessibility due to relief this study aims to evaluate 1 the performance of different supervised classification approaches using remote sensing data and 2 the use of additional information such as geomorphology we exemplify the methodology in the bardi zard area in ne iraq a part of the zagros fold thrust belt known for its chromite deposits we highlighted the improvement of remote sensing geological classification by integrating geomorphic features and spatial information in the classification scheme we performed a maximum likelihood ml classification method besides two machine learning algorithms mla support vector machine svm and random forest rf to allow the joint use of geomorphic features band ratio br principal component analysis pca spatial information spatial coordinates and multispectral data of the advanced space borne thermal emission and reflection radiometer aster satellite the rf algorithm showed reliable results and discriminated serpentinite talus and terrace deposits red argillites with conglomerates and limestone limy conglomerates and limestone conglomerates tuffites interbedded with basic lavas limestone and metamorphosed limestone and reddish green shales the best overall accuracy 80 was achieved by random forest rf algorithms in the majority of the sixteen tested combination datasets

reply sulphur isotope composition of the brunswick no 12 massive sulphide deposit bathurst mining camp new brunswick implications for ambient environment sulphur source and ore genesis the brunswick no 12 massive sulphide deposit occurs within a middle ordovician bimodal volcanic and sedimentary sequence that is thought to have formed in a continental back arc rift covered with a thick succession of carbonaceous hemipelagic and turbiditic sedimentary rocks the deposit consists of three en echelon lenses that are zoned from vent complex to bedded ore and bedded pyrite facies the bedded ore facies has the lowest average 34s values 14 2 but are only slightly less positive than laminated pyrite in footwall sedimentary rocks 34smean 15 1 34s values for the bedded sulphides show an upward increase from 14 2 in bedded ore to 16 5 in bedded pyrite average 34s values for vent complex 15 8 and underlying stringer sulphides 16 1 are consistently more positive than those for bedded ore in carbonaceous shales and siltstone of the patrick brook formation that underlie the deposit 34s values that range between 13 8 and 25 6 and the similarity of these values to those of the bru

machine learning based mapping of micro topographic earthquake induced paleo pulju moraines and liquefaction spreads from a digital elevation model acquired through laser scanning abstract the advent of public open source airborne laser scanning produced digital elevation models als dem has provided new perspectives on glacial geomorphology in the nordic countries seismically induced micro topographic paleo landforms can now be identified and mapped throughout the former fennoscandian ice sheet allowing spatial safety assessment for nuclear waste disposal automated machine learning techniques enable recognition of these fine scale geomorphological features efficiently and in a consistent way nationwide the current study focuses on automated recognition of paleo liquefaction spreads and pulju moraines in northern finland geomorphometric variables in different cell sizes were first derived from the 2 m als dem by gabor and principal curvature filtering to emphasize the elevational multi scale texture of these paleo seismic landforms the gabor textural variables were considered as a baseline method and the principal curvature features including maximum and minimum curvature were used because they have previously been proven critical in recognition of concave and convex elongated features both sets of raster variables were then turned into histogram based features and input into a non linear supervised multilayer perceptron early stop committee which is a neural network classifier the leave one out cross validation performance results indicated principal curvature features to be highly successful with 94 accuracy principal curvatures provided a clear improvement to gabor based features which provided significantly lower accuracies between 83 and 85 the study demonstrates the high success of supervised neural network based classification of als dem data and derived textural features capturing the multi scale nature of the micro topographic liquefaction spreads and pulju moraines the approach could be utilized for time efficient mapping of these paleo seismic geomorphologies to complete paleo seismic databases in formerly glaciated regions

application of self organizing map and srtm data to characterize yardangs in the lut desert iran abstract yardangs an exclusive landform due to intensive wind erosion cover a large area in the hyper arid lut desert of iran this paper presents a new approach using self organizing map som as unsupervised algorithm of artificial neural networks for analysis and characterization of yardangs nowadays the shuttle radar topography mission srtm with 3 arc sec data approximately 90 m resolution and nearly world wide coverage provides uniform good quality data the srtm 3 arc sec data were re projected to a 90 m utm grid bivariate quadratic surfaces with moving window size of 5 5 were fitted to this dem the first derivative slope steepness and the second derivatives minimum maximum curvature and cross sectional curvatures were calculated as geomorphometric parameters used as input to the soms 42 soms with different learning parameter settings e g initial and final radius number of iterations and the effect of random initial weights on average quantization error were investigated a som with a low average quantization error 0 1040 was used for further analysis feature space analysis morphometric signatures three dimensional inspection auxiliary data like landsat etm and high resolution satellite imagery from quickbird facilitated the assignment of semantic meaning to the output classes in terms of geomorphometric features results are provided in a geographic information system as thematic maps of landform entities based on form and slope e g yardangs ridge corridors valley or planar areas the results showed that all yardangs and corridors were clearly recognized and classified by this method when their width was larger than the dem resolution but became unrecognizable if their width is much smaller than the grid resolution the identified yardangs and corridors are aligned nnw sse parallel to the prevailing direction of the strong local 120 days wind and cover about 31 and 42 of the study area respectively the results demonstrate that som is a very efficient tool for analyzing aeolian landforms in hyper arid environments that provides very useful information for terrain feature analysis in remote regions

evolution of the subseafloor hydrothermal system associated with the ming vms deposit newfoundland appalachians and its controls on base and precious metal distribution the 487 ma ming volcanogenic massive sulfide vms deposit consists of four subparallel elongated semi massive to massive sulfides lenses the 1807 1806 ming north and ming south zones hosted in rhyodacite of the rambler rhyolite formation newfoundland appalachians a discordant cu rich lower footwall zone underlies the semi massive to massive sulfide lenses alteration associated with mineralization can be divided into nine facies that formed in three paragenetic stages 1 weak quartz calcite spessartine quartz sericite and quartz sericite chlorite alteration stage 1 2 quartz chlorite quartz chlorite sulfide and quartz chlorite sericite assemblages stage 2 and 3 quartz sericite sulfide and localized mn rich carbonate assemblages stage 3 a thin syngenetic silica rich layer immediately overlies part of the vms deposit and likely formed during the early stages the volcanic architecture and synvolcanic faults controlled the lateral distribution of extrusive rocks and hydrothermal alteration precipitation of the high temperature discordant to semi conformable cu rich chloritic assemblages stockwork was laterally restricted to one of these synvolcanic faults and the transition from coherent to volcaniclastic dominated lithofacies lower temperature sericitic assemblages stages 1 and 3 are controlled by the distribution of volcaniclastic rocks and generally form the immediate footwall to the semi massive to massive sulfide lenses lithogeochemical mass balance calculations illustrate the alteration minerals and mineralization chlorite rich assemblages gains in sio2 fe2o3t mgo cr ni and cu and losses in na2o mno and cao and sericite rich assemblages gains in k2o zn and ag and losses in mno mgo cao na2o and y calcium and magnesium rich alteration assemblages are restricted to the northwest fringe of the deposit distal to the main chloritic and sericitic alteration and have elemental gains in p2o5 y and losses in k2o the late stage 3 quartz sericite sulfide assemblage overprints most assemblages hosts sphalerite galena sulfosalt ag au rich veins and is spatially associated with coherent volcanic rocks the less permeable nature of these rocks is interpreted to have acted as a physical barrier for ascending metal rich hydrothermal fluids results from the detailed reconstruction of the hydrothermal architecture and paragenetic evolution of the ming deposit suggest that precious metals were introduced during the waning stage of the hydrothermal system associated with decreases in temperature and ph of the hydrothermal fluids

formation of volcanogenic massive sulfide deposits the kuroko perspective abstract the main objective of this paper is to identify the geochemical hydrological igneous and tectonic processes that led to the variations in the physical size geometry and chemical mineralogy metal ratios and zoning characteristics of volcanogenic massive sulfide deposits with respect to space from a scale of mining district size area to a global scale and time from a all volcanogenic massive sulfide deposits vmsds appear to have formed in extensional tectonic settings such as at mid ocean spreading centers backarc spreading centers and intracontinental rifts and failed rifts all vmsds appear to have formed in submarine depressions by seawater that became ore forming fluids through interactions with the heated upper crustal rocks submarine depressions especially those created by submarine caldera formation and or by large scale tectonic activities e g rifting become most favorable sites for the formation of large vmsds because of hydrological physical and chemical reasons the fundamental processes leading to the formation of vmsds include the following six processes 1 1 intrusion of a heat source typically a 10 3 km size pluton into an oceanic crust or a submarine continental crust causes deep convective circulation of seawater around the pluton the radius of a circulation cell is typically 5 km the temperature of fluids that discharge on the seafloor increases with time from the ambient temperature to a typical maximum of 350 c and then decreases gradually to the ambient temperatures in a time scale of 100 to 10 000 years the majority of sulfide and sulfate mineralization occurs during the waxing stage of hydrothermal activity 2 2 reactions between low temperature t 2 4 as disseminated gypsum and anhydrite in the country rocks 3 3 reactions of the modified seawater with higher temperature rocks at depths during the waxing stage cause the transformation of the seawater to metal and h 2 s rich ore forming fluids the metals and sulfide sulfur are leached from the county rocks the previously formed gypsum and anhydrite are reduced by fe 2 bearing minerals and organic matter providing additional h 2 s the mass of high temperature rocks that provide the metals and reduced sulfur is typically 10 11 tons 40 km 3 in volume the roles of magmatic fluids or gases are minor in most massive sulfide systems except for so 2 to produce acid type alteration in some systems 4 4 reactions between the ore forming fluids and cooler rocks in the discharge zone cause alteration of rocks and precipitation of some ore minerals in the stockwork ores 5 5 mixing of the ore forming fluids with local seawater within unconsolidated sediments and or on the seafloor causes precipitation of primitive ores with the black ore mineralogy sphalerite galena pyrite barite anhydrite 6 6 reactions between the primitive ores with later and hotter hydrothermal fluids cause transformation of primitive ores to matured ores that are enriched in chalcopyrite and pyrite variations in the mineralogical and elemental characteristics the geometry and the size of submarine hydrothermal deposits are controlled by the following four parameters 1 a the chemical and physical characteristics of seawater composition temperature density which depend largely on the geographical settings e g equatorial evaporating basins 2 b the chemical and physical characteristics of the plumbing system lithology fractures 3 c the thermal structure of the plumbing system which is determined largely by the ambient geothermal gradient and the size and temperature of the intrusive and 4 d the physical characteristics of the seafloor depth basin topography for example the submarine hydrothermal deposits developed in basaltic plumbing systems are generally poor in pb and ba compared to those developed in felsic plumbing systems the lower temperature systems are generally poorer in sulfides but richer in iron oxides and sulfates the higher temperature and larger hydrothermal systems tend to produce chalcopyrite and pyrite rich ores contrasts in the metal ratios between the noranda type archean vmsds and the younger vmsds reflect the differences in the geothermal gradient of the plumbing systems the submarine hydrothermal deposits developed in the near equatorial regions tend to form large continuous bedded type ores because of the likeliness of creating large stratified basins the basic processes of submarine hydrothermal mineralization have remained essentially the same throughout the geologic history from at least 3 5 billion year ago to the present

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

pb zn cu accumulation from seafloor sedimentation to metamorphism constraints from ore textures coupled with elemental and isotopic geochemistry of the tiemurt in chinese altay orogen nw china abstract the tiemurt pb zn cu deposit metal reserve 0 29 mt pb zn and 0 14 mt cu is hosted in the kangbutiebao formation volcanic sedimentary rocks in the chinese altay orogen nw china although some geological and geochemical characteristics of primary seafloor sedimentary mineralization are preserved major fault controlled pb zn cu orebodies are adjacent to the sarekbuobu orogenic gold deposit and therefore it is also interpreted to be closely related to regional deformational metamorphic processes the seafloor sedimentary mineralization is evidenced by the occurrence of the banded ores and marine sulfate originated sulfur isotopic compositions of the sulfides bimodal 34s values of 17 29 18 67 and 25 03 to 17 58 the lead isotope compositions accord with the evolution line of mantle implying that the pb were chiefly sourced from the mantle reservoir the later deformational and metamorphic overprinting are recorded by the fault controlled lodes with ore textures of epigenetic infilling and replacement besides well developed co2 rich fluid inclusions the d o isotopic data of the overprinting fluids fall into the area between metamorphic fluids and meteoric water line indicative of metamorphic fluids origin with meteoric water involvement to further trace the pb zn cu accumulation and remobilization processes systematic in situ trace elements in sulfides of different generations are analyzed using la icp ms ti mn cu pb zn bi concentrations in pyrite show a trend of progressive decrease from early to late generations similar decreasing trends of trace element concentrations are also present in sphalerite galena chalcopyrite and pyrrhotite although the combinations of trace element are slightly different this indicates that the ore forming metals esp cu pb and zn were initially locked up in the crystal lattice of the vms sulfides especially pyrite deformational and metamorphic processes of the primary ores during the permian triassic collisional orogeny have likely led to trace element remobilization and sulfides purification which redistributed the metals and upgraded the ores combined with previous studies we proposed that the pb zn cu of tiemurt had been accumulated from seafloor sedimentation ca 400 ma to deformation metamorphism processes ca 240 ma

towards a definition of topographic divisions for italy abstract the study has divided italy into eight major topographic divisions provinces and 30 minor divisions sections that are similar to n fenneman s units of the united states provinces and sections are generally consistent with observed morphology the new units were defined step wise in a semi quantitative approach that combined an unsupervised three class cluster analysis of four derivatives of altitude visual interpretation of morphometric maps including shaded relief and comparative inspection of small scale geological and structural maps the four variables are altitude slope curvature frequency of slope reversal and elevation relief ratio highland upland and lowland topographic types were identified the variables were computed from a 230 m resolution digital terrain model regridded from the original 230 m dem obtained by mosaicking the entire italian mean elevation archive

a coupled approach to simulate initiation of outbursts of coal and gas model development an outburst of coal and gas is a major hazard in underground coal mining it occurs when certain conditions of coal stress strength and gassiness are met the outburst is recognized as a two step process i e initiation and development each step has its own characteristics and requires different approaches in numerical modeling as a first step the initiation process of the outburst is numerically simulated with a coupled simulator the simulator models the deformation and failure of a coal seam adsorption and desorption of gas and flow of gas and water in coal the simulator is developed by linking and sequentially executing two numerical codes flac3d and comet3 flac3d is a widely used commercial code designed for engineering mechanics computation while comet3 is a well established code to model gas and water production from desorption controlled reservoirs in this paper these two codes are linked and sequentially executed through coupling modules including a user designed c module and several modules developed with the build in fish language in flac3d these coupling modules are used to transfer relevant data between the codes a simple example to simulate the initiation of the outburst is also presented in this paper to demonstrate the capability of the coupled simulator

permeability enhancements of borehole outburst cavitation in outburst prone coal seams abstract borehole outbursts eject coal power create cavities and relieve in situ stress while drilling cross measure boreholes into outburst coal seams for pre drainage this paper highlights the borehole outburst cavitation to enhance the permeability of coal for the first time borehole outburst is a mechanical behavior and the outburst trigger and development depend on the status of gas pressure gradient near the opening coal wall it was testified that the high pressure water with 10 15 mpa in pressure and 20 30 m3 h in flow was feasible to remove the failure coal near the opening wall and stimulate a new set of outbursts thus creating bigger cavities and better permeability enhancement furthermore an outburst control system was designed for borehole outburst cavitation the system contains an outburst stimulation subsystem a gas drainage subsystem and a separation subsystem thus ensuring the flow and the separation of outburst ejections within a relatively closed environment the outburst cavity reconstitutes the in situ stress and permeability of the surrounding coal mass leading to a failure zone a plastic zone and a visco elastic zone the failure zone and the plastic zone due to borehole outburst cavitation are both effective in permeability enhancement finally a field test in the no 10 coal seam at the luling mine proved that the sufficient permeability enhancement scope is approximately twelve times of the cavity radius the permeability enhancement promotes the increase of borehole distance from 5 m to 12 m thus reducing 78 7 of boreholes in number for the pre drainage of the no 10 coal seam

alteration mineralogy lithochemistry and stable isotope geochemistry of the murgul artvin ne turkey volcanic hosted massive sulfide deposit implications for the alteration age and ore forming fluids abstract the murgul artvin ne turkey massive sulfide deposit is hosted dominantly by late cretaceous calc alkaline to transitional felsic volcanics the footwall rocks are represented by dacitic flows and pyroclastics whereas the hanging wall rocks consist of epiclastic rocks chemical exhalative rocks gypsum bearing vitric tuff purple vitric tuff and dacitic flows multi element variation diagrams of the hanging wall and footwall rocks exhibit similar patterns with considerable enrichment in k rb and ba and depletion in nb sr ti and p the chondrite normalized rare earth element rees patterns of all the rocks are characterized by pronounced positive negative eu anomalies as a result of different degrees of hydrothermal alteration and the semi protected effects of plagioclase fractionation mineralogical results suggest illite illite smectite chlorite kaolinite and chlorite in the footwall rocks and illite smectite kaolinite and chlorite illite in the hanging wall rocks overall the alteration pattern is represented by silica sericite chlorite and chlorite carbonate epidote sericite and quartz albite zones increments of ishikawa alteration indexes resulting from gains in k 2 o and losses in na 2 o and the chlorite carbonate pyrite index towards to the center of the stringer zone indicate the inner parts of the alteration zones calculations of the changes in the chemical mass imply a general volume increase in the footwall rocks abnormal volume increases are explained by silica and iron enrichments and a total depletion of alkalis in silica zone relative k increments are linked to the sericitization of plagioclase and glass shards and the formation of illite smectite in the sericite zone in addition fe enrichment is always met by pyrite formation accompanied by quartz and chlorite illite is favored over chlorite smectite and kaolinite in the central part of the ore body due to the increase in the al k na ca ratio although the rees were enriched in the silicification zone light rees show depletion in the silicification zone and enrichment in the other zones in contrast to the heavy rees behavior hydrothermal alteration within the hanging wall rocks apart from the gypsum bearing vitric tuffs is primarily controlled by chloritization with proportional fe and mg enrichments and sericitization the 18 o and d values of clay minerals systematically change with increasing formation temperature from 6 6 to 8 7 and 42 to 50 for illites and 8 6 and 52 for chlorite respectively the o and h stable isotopic data imply that hydrothermal alteration processes occurred at 253 332 c for illites and 136 c for chlorite with a temperature decrease outward from the center of the deposit the positive 34 s values 20 3 to 20 4 for gypsum suggest contributions from seawater sulfate reduced by fe oxide hydroxide phases within altered volcanic units thus the hydrothermal alteration possibly formed via a dissolution precipitation mechanism that operated under acidic conditions the k ar dating 73 62 ma of the illites indicates an illitization process from the maastrichtian to early danian period

petrology and u pb geochronology of footwall porphyritic rhyolites from the wolverine volcanogenic massive sulfide deposit yukon canada implications for the genesis of massive sulfide deposits in continental margin environments porphyritic rhyolite sills form an important component of the footwall of the wolverine volcanogenic massive sulfide vms deposit yukon canada and occur proximal to mineralization in the immediate deposit area wolverine lynx zone and at similar stratigraphic levels along strike fisher puck and sable zones porphyritic rhyolites are of two types an older quartz feldspar porphyritic qfp rhyolite suite and a younger feldspar porphyritic fp suite both the qfp and fp suites of intrusions are semiconcordant suggesting a silllike morphology and are altered and crosscut by veinlet mineralization suggesting that they are pre to synmineralization the margins of qfp suite of intrusions contain minor xenoliths of surrounding shales and poorly developed chilled margins suggesting emplacement into partially consolidated sedimentary rocks whereas the fp suite of intrusions shows well developed chilled margins indicative of emplacement into fully solidified sedimentary rock these features suggest that the qfp suite of intrusions represents an older phase of rhyolitic magmatism whereas the fp suite represents a younger event this is supported by u pb zircon ages which indicate a 352 4 1 5 ma emplacement age for the fp suite and a 347 to 346 ma emplacement for the fp suite two ages at 347 8 1 3 and 346 0 2 2 ma both suites of porphyries have inherited proterozoic zircon and have ratios of la smucn 1 and nb thucn 1 ucn upper continental crust normalized indicating derivation from and or extensive interaction with ancient upper continental crustal materials the fp suite however has elevated high field strength element hfse and rare earth element ree contents high zircon saturation temperatures and higher nb ta ratios and lower ti sc ratios than the qfp suite these features are interpreted to reflect that the fp suite of magmas was hotter 900 c melts with a greater mantle component in their genesis both suites however are interpreted to have formed due to basaltic upwelling crustal melting and crust mantle mixing during ensialic back arc basin activity the presence of mantle heat within the wolverine basin from 352 to 347 to 346 ma a minimum of 5 m y suggests that sustained mantle heat flow was critical to the genesis of the wolverine porphyries it is also suggested that this sustained mantle heat was responsible for the wolverine hydrothermal system and that upwelling mantle may be essential in providing the heat to drive hydrothermal systems even in continental margin type vms environments e g bathurst iberian pyrite belt the wolverine porphyries are among the most hfse and ree enriched felsic rocks associated with vms mineralization globally the high hfse and ree concentrations in these rocks are interpreted to be due to

distribution mineralogy and geochemistry of selenium in felsic volcanic hosted massive sulfide deposits of the finlayson lake district yukon territory canada three significant base metal deposits were recently discovered in the finlayson lake district yukon territory canada however widely varying selenium contents e g 1 100 ppm avg se at wolverine 200 ppm avg se at kudz ze kayah and 7 ppm avg se at gp4f have hindered their rapid exploitation observations and data from the deposits in the finlayson lake district show a strong positive correlation between high temperature 300 c copper rich sulfide assemblages at the base of volcanic hosted massive sulfide vhms and the selenium content of all sulfide minerals thermodynamic calculations for selenide and sulfide minerals indicate significantly higher temperatures of formation and lower solubilities of selenide versus sulfide minerals which is consistent with petrographic observations and can explain the distribution of selenium in zone refined vhms and volcanic sediment hosted massive sulfide deposits volumetric mass balance calculations indicate that some selenium could be sourced from contemporaneous volatile degassing of seo 4 its rapid reduction to h 2 se and subsequent entrainment into hydrothermal ore fluid however estimates for the kudz ze kayah and wolverine deposits suggest an additional large se reservoir volumetric mass balance estimates indicate that contemporaneous volcanic rocks and black shales are likely selenium reservoirs for the kudz ze kayah and wolverine deposits respectively

the gold content of volcanogenic massive sulfide deposits volcanogenic massive sulfide deposits contain variable amounts of gold both in terms of average grade and total gold content with some vms deposits hosting world class gold mines with more than 100 t au previous studies have identified gold rich vms as having an average gold grade expressed in g t exceeding the total abundance of base metals expressed in wt however statistically meaningful criteria for the identification of truly anomalous deposits have not been established this paper presents a more extensive analysis of gold grades and tonnages of 513 vms deposits worldwide revealing a number of important features in the distribution of the data a large proportion of deposits are characterized by a relatively low gold grade 2 g t with a gradual decrease in frequency towards maximum gold grades defining a log normal distribution in the analysis presented in this paper the geometric mean and geometric standard deviation appear to be the simplest metric for identifying subclasses of vms deposits based on gold grade especially when comparing deposits within individual belts and districts the geometric mean gold grade of 513 vms deposits worldwide is 0 76 g t the geometric standard deviation is 2 70 g t au in this analysis deposits with more than 3 46 g t au geometric mean plus one geometric standard deviation are considered auriferous the geometric mean gold content is 4 7 t au with a geometric standard deviation of 26 3 t au deposits containing 31 t au or more geometric mean plus one geometric standard deviation are also considered to be anomalous in terms of gold content irrespective of the gold grade deposits with more than 3 46 g t au and 31 t au are considered gold rich vms a large proportion of the total gold hosted in vms worldwide is found in a relatively small number of such deposits the identification of these truly anomalous systems helps shed light on the geological parameters that control unusual enrichment of gold in vms at the district scale the gold rich deposits occupy a stratigraphic position and volcanic setting that commonly differs from other deposits of the district possibly due to a step change in the geodynamic and magmatic evolution of local volcanic complexes the gold rich vms are commonly associated with transitional to calc alkaline intermediate to felsic volcanic rocks which may reflect a particularly fertile geodynamic setting and or timing e g early arc rifting or rifting front at the deposit scale uncommon alteration assemblages e g advanced argillic aluminous strongly siliceous or potassium feldspar alteration and trace element signatures may be recognized e g au ag as sb bi hg te suggesting a direct magmatic input in some systems

a special issue devoted to continental margin massive sulfide deposits and their geodynamic environments the papers in this issue arise from a special session held at the may 2003 geological association of canada gac mineralogical association of canada mac society of economic geologists seg meeting in vancouver british columbia canada entitled massive sulfides on the edge the formation of vms and sedex deposits within evolving continental margins continental margin environments e g continental arcs arc rifts and back arc basins host some of the world s largest volcanogenic massive sulfide vms and sedimentary exhalative sedex deposits e g bathurst iberian pyrite belt yet there remains an incomplete understanding of the regional to local scale controls on their setting and genesis the purpose of this issue is to explore and better understand the setting styles and continent to deposit scale controls on the localization of these deposits within and along continental margins the papers here build on recent multidisciplinary projects such as those on the bathurst camp goodfellow et al 2003 on australian vms environments large et al 2001 and the ongoing international geological correlation program igcp project 502 on global comparison of volcanic hosted massive sulfide districts the controls on the distribution and timing of vms deposits allen et al 2002 the results presented here contribute new data and observations from both well known camps e g iberian pyrite belt and new camps and deposits for which little published information is available e g finlayson lake in the yukon tanana terrane greens creek in the alexander terrane baiyinchang in gansu province china la plata in western ecuador and cuale in the gurrerro terrane mexico the papers in the volume range from those that are regional in scope e g bissig et al 2008 mortensen et al 2008 taylor et al 2008 to new deposit descriptions e g bradshaw et al 2008 chiaradia et al 2008 to new information on known deposits e g barrett et al 2008

hydrothermal alteration and volatile element halos for the rosebery k lens volcanic hosted massive sulfide deposit western tasmania a detailed study of alteration mineralogy mineral chemistry and lithogeochemistry in the host rocks surrounding the a b and k lenses at the north end of the rosebery mine has revealed a series of overlapping alteration halos with characteristic mineralogy and geochemistry the study involved logging and sampling from nine drill holes spaced at varying distances from the a b and k lenses the stratiform zn pb cu ore lenses have a sheetlike morphology and are hosted by a mixed sequence of rhyolitic to dacitic massive mediumgrained quartz porphyritic pumice breccia black mudstone and crystal rich volcaniclastic sandstone overlying a thick homogeneous sequence of rhyolitic pumice breccia the major alteration minerals at rosebery are arranged in a complex series of zones passing away from the deposit quartz sericite zone mn carbonate zone chlorite zone and outer sericite zone the chlorite zone is best developed in the immediate footwall below the copper pyrite rich ore lenses whereas the strongest mn carbonate alteration occurs in the immediate hanging wall volcanics or lateral to the ore lenses the outermost visible sericitic alteration extends about 60 to 100 m into the footwall 10 to 20 m into the hanging wall and over 500 m along the upper contact of the footwall pumice breccias thallium and antimony form the most extensive trace element halos related to the mineralization thallium forms a halo that extends 200 to 300 m into the overlying volcanics and 60 to 100 m into the footwall anomalously high thallium also occurs over 500 m along strike marking the contact between the footwall pumice breccias and the overlying volcaniclastic sandstones proximal to the ore lenses tl and sb values range from 10 to 100 ppm compared to the halo zone where they vary from around 1 to 10 ppm studies of alteration mineral chemistry at rosebery have revealed some important relationships that may assist exploration the mn content of alteration carbonate increases toward ore both along strike and across strike close to ore alteration carbonates contain 20 mole percent mnco3 kutnahorite rhodochrosite mn siderite and mn ankerite whereas at distances of 40 to 60 m across strike the mole percent mnco3 in carbonate drops to below 10 percent at greater than 80 m the carbonates are mn poor calcites and are commonly located in synmetamorphic structures white mica composition changes with stratigraphy and alteration assemblages and may be related to the mineralizing event although this has not been convincingly demonstrated proximal white mica contains minor ba substituting for octahedral al however except for their ba content these phengetic white micas are similar to those found in nonmineralized areas of the mount read volcanics sodic white mica with up to 0 35 na na k and a low phengite content 0 5 fe mg cations occurs in a zone of volcanic sandstones and black slates overlying the ore deposit this research has lead to the development of a series of proximal medial and distal vectors useful for both regional and mine scale exploration the most useful vectors listed from proximal to distal include zn ba content of white mica na2o k2o ishikawa alteration index ai s na2o ba sr mn content of carbonate tl and sb

spatial and temporal evolution of an avulsion on the taquari river distributive fluvial system from satellite image analysis avulsion processes have been observed and analyzed using field based studies however they have rarely been analyzed through use of satellite imagery even though such an approach allows documentation of spatial and temporal variations of the resulting deposits in order to document changes that are occurring at the caronal avulsion on the taquari river brazil a time series of landsat imagery from 1985 to present 2010 was compiled as of july 2010 the imagery shows that the avulsion is not yet complete with discharge being routed to both the parent channel and the avulsion channel in the floodbasin the avulsion was initiated as flow was diverted from the parent channel to the floodbasin through two small crevasses allowing the development and evolution of splays with a single splay stabilizing only since 1999 the avulsion area is marked by the growth of new splays the formation of an avulsion belt and progradation of avulsion deposits into the floodbasin the parent channel downstream of the avulsion site has experienced decreasing width through time associated with the higher volumes of water and sediment being captured by the avulsion channel because this avulsion is not yet complete we expect more morphological changes to occur as the avulsion belt evolves into the primary channel rapid sedimentation caused by this avulsion and the 24 year time series of imagery that captured this change allowed us to construct a 3d block representing the evolution of depositional environments associated with avulsion using time in the vertical dimension thus we could represent the evolution of geomorphological patterns including floodbasin proximal levee distal levee and channel deposits and project their distributions through time this block of evolving sedimentary settings can be used as a guide for future sedimentologic studies by offering visual clues regarding the way which depositional systems track avulsion initiated changes

the generation of a stratiform skarn and volcanic exhalative pb zn deposit sawusi in the southern chinese altay mountains the constraints from petrography mineral assemblage and chemistry abstract numerous pb zn and fe ore deposits occur in the volcanic sedimentary basins along the southern chinese altay mountains the mineralization of these deposits is hosted by early middle devonian volcanics and sedimentary rocks and is directly associated with skarns the genesis of these deposits is uncertain or hotly debated this study considers the sawusi pb zn deposit from the southern chinese altay the host rock of the sawusi deposit is rhyolitic crystal tuff with intercalated bands of fe mn calcic carbonates and a small amount of rhyolite within the upper section of the early devonian kangbutiebao formation on the basis of a field investigation the petrographic features of the skarn were described detailed electron microprobe analysis was performed on the skarn minerals and the o h and c isotopic compositions of quartz and its fluid inclusions were determined petrographic observation revealed a progressively intensifying alteration from the tuff and its intercalated bands to the stratiform skarn characterized by alternate bands of dark garnet biotite skarn and light grunerite biotite skarn mineral chemical analysis shows that the stratiform skarn of the sawusi deposit consists mainly of spessartine almandine mn rich grunerite biotite and fe mn calcic carbonate minerals a mass balance consideration of the cations in the skarn minerals suggests that the stratiform skarn formed through dimetasomatism between the tuff and intercalated bands of sedimentary fe mn calcic carbonates however the scale of the metasomatism is limited to a few centimeters laser 40 ar 39 ar dating was performed on the skarn grunerite yielding an isochron age of 412 15 ma the 40 ar 39 ar age is identical within analytical error to the zircon u pb age 401 2 7 ma of the rhyolite from the kangbutiebao formation that hosts the skarn and pb zn mineralization and the age 401 3 1 ma of the biesisala porphyry sawusi deposit the o h and c isotopic compositions show that the ore forming fluid includes two components one is h 2 o co 2 which has volatilized from carbonate and dehydrated from tuff and the other is meteoric derived surface water carrying minor meteoric co 2 or organic matter derived co 2 therefore the stratiform skarn and pb zn mineralization of the sawusi deposit are quite different from the contact metasomatic skarn and related deposits and suggest a volcanic exhalation sedimentation origin instead this study has broad relevance to the pb zn and fe deposits along the southern altay mountains in the areas of ore genesis study and ore prospecting

multiple sources of selenium in ancient seafloor hydrothermal systems compositional and se s and pb isotopic evidence from volcanic hosted and volcanic sediment hosted massive sulfide deposits of the finlayson lake district yukon canada volcanic hosted massive sulfide vhms and volcanic sediment hosted massive sulfide vshms i e hosted by both volcanic and sedimentary rocks deposits in the finlayson lake district yukon canada provide a unique opportunity to study the influence of seafloor and sub seafloor hydrothermal processes on the formation of se poor gp4f vhms deposit 7 ppm se average intermediate kudz ze kayah kzk vhms deposit 200 ppm se average and se enriched wolverine vshms deposit 1100 ppm se average mineralization all three deposits are hosted by mid paleozoic 360 346 ma felsic volcanic rocks but only the wolverine deposit has voluminous coeval carbonaceous argillites black shales in the host rock package here we report the first application of se isotope analyses to ancient seafloor mineralization and use these data in conjunction with pb and s isotope analyses to better understand the source s and depositional process es of se within vhms and vshms systems the wide range of 82se 10 2 to 1 3 relative to nist 3149 34s 2 0 to 12 8 cdt and elevated se contents up to 5865 ppm within the wolverine deposit contrast with the narrower range of 82se 3 8 to 0 5 34s 9 8 to 13 0 and lower se contents 200 ppm average of the kzk deposit the wolverine and kzk deposits have similar sulfide depositional histories i e deposition at the seafloor with concomitant zone refining the se in the kzk deposit is magmatic leaching or degassing in origin whereas the wolverine deposit requires an additional large isotopically negative se source i e 15 82se the negative 82se values for the wolverine deposit are at the extreme light end for measured terrestrial samples and the lightest observed for hypogene sulfide minerals but are within calculated equilibrium values of 82se relative to nist 3149 30 at 25 c between seo4 and se2 we propose that the most negative se isotope values at the wolverine deposit record the 82se of the se source and that the wide range in 82se values results from the combined effects of thermal and chemical degradation and se loss from the carbonaceous argillite source to a hydrothermal fluid including magmatic se i e leached and or magmatic hydrothermal with deposition at or near the paleoseafloor pristine unaltered black shales show little variation in 82se relative to bulk earth se accumulation and fractionation to more negative isotopic values is interpreted to have been produced by post sediment deposition but pre ore stage reduction of seawater se within the black shales

mechanism of instantaneous coal outbursts thousands of mine workers die every year from mining accidents and instantaneous coal outbursts in underground coal mines are one of the major killers various models for these outbursts have been proposed but the precise mechanism is still unknown we hypothesize that the mechanism of coal outbursts is similar to magma fragmentation during explosive volcanic eruptions i e it is caused by high gas pressure inside coal but low ambient pressure on it breaking coal into pieces and releasing the high pressure gas in a shock wave hence coal outbursts may be regarded as another type of gas driven eruption in addition to explosive volcanic lake and possible ocean eruptions we verify the hypothesis by experiments using a shock tube apparatus knowing the mechanism of coal outbursts is the first step in developing prediction and mitigation measures the new concept of gas driven solid eruption is also important to a better understanding of salt gas outbursts rock gas outbursts and mud volcano eruptions

a method for combining srtm dem and aster gdem2 to improve topography estimation in regions without reference data abstract digital elevation models dems such as advanced spaceborne thermal emission and reflection radiometer global digital elevation models aster gdem or shuttle radar topography mission dem srtm are widely used in remote areas and non industrial countries because of their availability rather than their accuracy although a global dem can be considerably enhanced using additional reference information such as higher resolution dems or ground truth points improving accuracy in areas without reference data remains a challenge this paper develops an approach to improve the accuracy of the estimated topography by combining two complementary dems aster gdem 1 arc second and srtm dem 1 arc second in regions missing reference data the combination approach is based on formulating relationships between slopes and weights in sites with reference data then the developed relationships are applied to sites with similar geomorphology to determine the combination weight for each dem without using reference data the results indicate that combined dems offer significant improvements of 47 and 20 in mean bias over a mountainous site and 16 and 58 at a low relief site when compared with the srtm and aster gdem products respectively dem derived drainages were also found to be more accurate for the combined dems than the near global dems in areas where reference data is not available

carbonic fluid overprints in volcanogenic massive sulfide deposits examples from the kelan volcanosedimentary basin altaides china the tiemurte and the dadonggou zn pb cu volcanogenic massive sulfide vms deposits situated in the devonian kelan volcanosedmentary basin of the south margin of the chinese altaides were metamorphosed and overprinted by metamorphic sulfide quartz veins during early carboniferous to early permian two mineralizing periods of ore mineral growth can be identified 1 disseminated banded and massive sulfide ores related to a primary depositional sea floor volcanic hydrothermal activity and 2 the foliated sulfide quartz veins q1 related to synorogenic metamorphism and late chalcopyrite bearing quartz veins q2 cutting the schist related to a younger metamorphic overprinting event carbonic co 2 ch 4 n 2 fluid inclusions are ubiquitous in q1 and q2 veins a few carbonic fluid inclusions may be primary and some may be pseudosecondary whereas the vast number of carbonic fluid inclusions are secondary representing later events a microthermometry study shows that primary carbonic fluid inclusions in q1 and q2 have tm co2 ranging from 64 5 to about 59 4 c with th co2 13 4 to about 18 6 c the secondary carbonic fluid inclusions exhibit two behaviors when cooling and heating the tm co2 of the first group l co2 ranges from 63 3 to 57 7 c and that of the second group l co2 ch4 n2 ranges from 83 4 to 61 c the second group of carbonic fluids has much higher ch 4 and or n 2 proportions than the first group the trapping temperatures for the carbonic inclusions have been estimated to be 243 1 to 412 1 c for tiemurte and 216 to 430 c for dadonggou on the basis of some l co2 l h2o inclusions associated with carbonic inclusions and the trapping pressures have been estimated to be 120 to 340 mpa which are consistent with deformation p t conditions of quartz and slightly less than the p t conditions of the biotite and garnet metamorphic zones these abundant carbonic inclusions at the tiemurte and the dadonggou deposits were not a part of a volcanogenic ore producing system but represent a much younger event possibly having originated from a synorogenic metamorphism which may have contributed to orogenic gold

origin of the eskay creek precious metal rich volcanogenic massive sulfide deposit fluid inclusion and stable isotope evidence the eskay creek deposit is an unusual polymetallic au ag rich volcanogenic sulfide sulfosalt deposit located in the iskut river area of northwestern british columbia canada economic concentrations of precious and base metals are contained in the 21 zone which is divided into a number of subzones as of december 31 1998 total production and proven probable reserves are 1 9 million tons mt at 60 2 g t au 2 652 g t ag 3 2 percent pb 5 2 percent zn and 0 7 percent cu the 21b zone which contains the bulk of the reserves began production in 1995 the mineralization occurs mainly as well preserved stratiform clastic beds of sulfide sulfosalt debris and also as discordant footwall quartz sulfide veins the hydrothermal system that formed the eskay deposit was low temperature

discussion sulphur isotope composition of the brunswick no 12 massive sulphide deposit bathurst mining camp new brunswick implications for ambient environment sulphur source and ore genesis the authors w d goodfellow and j m peter report an impressive amount of chemical data on the brunswick no 12 orebody one of the world s largest volcanic associated massive sulphide deposits they have proposed that most of the sulphur in the massive sulphide ore and the pyrites in adjoining sediments of the patrick brook formation was probably derived from an overlying anoxic seawater column in which sulphate reduction had taken place the resulting h2s having mixed with venting metal rich fluids the principal lines of evidence brought in to support this idea are 1 the sediments of the patrick brook formation underlying the footwall sedimentary and volcanic rocks of the nepisiguit falls formation which hosts the orebody have s c values and mn and fe contents that indicate anoxic conditions in the seawater during sedimentation 2 the 34s values of the sulphides in the ore types and the underlying feeder zone are similar to those of pyrites in the patrick brook formation and to coeval pyrites in the selwyn basin and 3 there is no alternative source of reduced sulphur because there would be inadequate sulphate remaining in deep circulating seawater to provide sufficient reduced sulphur for ore formation and there is little evidence for the presence of evaporite sulphate in the deep footwall sequence the significance of their major lines of evidence and also those of lentz et al 1996 is discussed below

sulfur isotope variability in sediment hosted massive sulfide deposits as determined using the ion microprobe shrimp i an example from the rammelsberg orebody discussion

australian volcanic hosted massive sulfide deposits features styles and genetic models the cambro ordovician period has yielded the major development of volcanic hosted massive sulfide vhms deposits in australia resulting in about 12 million metric tons of contained metal copper lead and zinc concentrated in the mount read volcanics tasmania and the mount windsor volcanics queensland the archean 4 million metric tons of metal and the silurian 3 5 million metric tons of metal constitute the next important episodes while the devonian and permian have produced isolated deposits the deposits range from cu type to zn cu type to zn pb cu type the zn cu type deposits are restricted to the archean and silurian whereas the cu type and zn pb cu type occur sporadically throughout the time span from early archean to permian in general terms the major vhms bearing districts are calc alkaline in character and display a thick basal pile of rhyolitic volcanics 1 3 km thick including lavas epiclastics and subvolcanic intrusions which is overlain by a polymodal sequence containing various proportions of rhyolite dacite andesite basalt and sediments the major deposits are commonly located at the top contact of the rhyolite pile or within the lower part of the overlying polymodal sequence there is a wide range in variability of styles of australian vhms deposits including mounds pipes sheets layered deposits stacked deposits stockwork and disseminated deposits distal reworked deposits and cyclic layered deposits although these various styles show a range of features there is a consistent theme across the spectrum of metal zonation alteration mineralogy alteration chemistry sulfur isotopes macrotextures microtextures and host volcanic relationships which strongly suggests that they all belong to the one genetic group of ore deposit the classic mound style deposits such as hellyer have a series of key features subsets of which are represented in the other deposit styles the mound deposits are considered to form from deposition of metal sulfides on the sea floor immediately around the hydrothermal vent growth of the mound occurs by upward replacement of sulfide assemblages stable at higher fluid temperatures leading to zone refining and lead zinc silver gold enrichment in the outer and upper parts of the mound departure from the classic mound style of deposit is related principally to three key factors the chemistry of the ore fluid salinity temperature f02 and ah2s the nature permeability and chemistry of the volcanic pile and the sea hoor environment sea hoor topography and seawater depth these factors control the aspect ratio of the deposit the extent of stringer zone development the degree of subsea floor replacement mineralization the nature and spatial development of footwall alteration and the development and style of related distal mineralization sulfur isotope studies of australian vhms deposits indicate that reduced seawater sulfate is a major source of sulfur in the deposit whereas lead and strontium isotope results are compatible with the metals being derived by seawater convection and leaching from the volcanic pile and basement rocks this conclusion is supported by the application of various leaching models which demonstrate the availability of an adequate source of both base and precious metals in the footwall volcanic sequences the input of metals directly from volcanic magma chambers is not precluded by the available data and one likely scenario involves the contribution of gold and copper from a magmatic vapor plume rising to mix with convective seawater fluids which contribute lead zinc silver and gold leached from the footwall volcanics and basement rocks the relative importance of the magmatic input compared with the seawater convective input may help to explain the spectrum of deposit styles arid their spatial relationship to volcanic centers or adjacent sedimentary basins

a revised stratigraphic and tectonic framework for the ashele volcanogenic massive sulfide deposit in the southern chinese altay evidence from stratigraphic relationships and zircon geochronology abstract the ashele volcanogenic massive sulfide vms deposit is the largest and most representative vms deposit in the chinese altay metallogenic belt but its stratigraphic sequence tectonic framework and morphology are debated in this paper on the basis of previous research field investigations excavation pits drill core sampling and new la icp ms u pb analyses of zircons from mafic and felsic volcanic rocks we show that the main structure of the ashele deposit is an overturned tightly closed syncline and that the primary orebody is controlled by this structure moreover we show that the ashele vms deposit displays a double layer structure made up of a feeder zone of veinlet disseminated and stockwork orebodies overlain by massive stratiform orebodies that are folded we revise the stratigraphy of the ashele formation into five conformable sedimentary subsequences based on new field investigations and the zircon geochronology of each subsequence from bottom to top we divide the formation into a siliceous tuff layer 405 1 1 8 ma a dacitic layer 395 9 403 ma a rhyolitic layer 390 9 0 83 ma an orebody layer ca 387 ma and a basalt layer 387 377 ma the early to middle devonian ashele formation unconformably underlies the late devonian qiye formation

genesis of the wolverine volcanic sediment hosted massive sulfide deposit finlayson lake district yukon canada mineralogical mineral chemical fluid inclusion and sulfur isotope evidence the wolverine deposit is a high grade 6 2 mt at 12 7 zn 1 3 cu 1 6 pb 370 9 g t ag and 1 8 g t au volcanic and sedimentary rock hosted massive sulfide deposit in the finlayson lake area yukon territory the area has the potential to become an important mining camp and currently contains more than 30 million tons mt of massive sulfide ore in five deposits a succession of metamorphosed early mississippian felsic volcanic and sedimentary rocks that are interpreted to have formed on the margin of an ensialic back arc ocean basin between the yukon tanana terrane and the ancestral north american craton hosts the wolverine deposit the massive sulfide ore occurs at a single horizon that marks a significant change in the character of the volcanism from quartz and feldspar phyric rhyolite of the footwall to aphyric rhyolite and chemical sedimentary exhalative rock of the hanging wall the deposit consists of two discrete zn pb ag massive sulfide lenses situated at the same stratigraphic level connected by strata bound semimassive replacement style zn pb ag mineralization copper rich massive sulfide commonly replaces the zn pb ag massive sulfide at the base of the lenses and in the footwall replacement zones beneath the massive mineralization several zones of sulfide stringer veins and chlorite sericite carbonate alteration occur within permeable footwall volcaniclastic rocks alteration minerals preferentially associated with massive sulfide mineralization include ba rich phengitic mica biotite mg rich chlorite and siderite microthermometric measurements of fluid inclusions in the massive sulfide bodies and accompanying stringer zones indicate formation at temperatures of 235 to 353 c primary aqueous liquid rich fluid inclusions in hydrothermal quartz from quartz sulfide stringer veins contain low salinity fluids 2 1 8 5 wt nacl equiv mean 6 0 there is no evidence of fluid boiling in the inclusions and based on the average fluid salinity and temperature of homogenization mineralization took place under a minimum water depth of 1 000 m in situ analyses of 34sv cdt in sulfide minerals from massive sulfide lenses means 0 8 and sulfide stringer veins mean 12 0 display a bimodal distribution lower 34s values characterize sulfides near the top of the lenses versus higher more positive values in underlying veins may reflect different processes of reduction of seawater sulfate sulfur in sulfides from the tops of the lenses was likely derived mainly from bacterial reduction of seawater sulfate whereas sulfur in the stringer veins and at the base of the lenses was mainly from inorganic reduction of seawater sulfate sulfide minerals precipitated both on the sea floor and in the subsea floor from hydrothermal fluids that vented from multiple mounds the presence of black shales and the strongly positive sulfur isotope compositions of the sulfides provide evidence that the ambient bottom water in the basin in which the wolverine deposit formed was likely anoxic this environment may have contributed to the preservation of the sulfide mounds based on its tectonic setting host rock types local geologic setting metal grades age and source s of sulfur the wolverine deposit best exemplifies the volcanic sediment hosted massive sulfide vshms class of syngenetic massive sulfide deposits in the district

fluid inclusion and stable isotopic constraints on fluid sources and evolution of the luojiahe cu deposit in the southern margin of the north china craton abstract the luojiahe cu deposit in the zhongtiaoshan region is located in the southern margin of the north china craton the orebodies are hosted in the mafic volcanic sedimentary sequences of the metamorphosed greenschist facies neoarchean songjiashan group the luojiahe cu mineralization can be divided into the primary volcanogenic massive sulfide vms mineralization stage stage i banded or stockwork ores and the subsequent metamorphic remobilization stage stage ii coarse vein ores three types of quartz selected for fluid inclusion fi studies were collected from the stage i banded q1 and stockwork q2 ores and stage ii coarse vein q3 ores four types of fis were identified 1 liquid rich fis l type 2 pure vapor and vapor rich fis v type 3 daughter mineral bearing fis s type and 4 ch4 h2o fis c type systematical microthermometric and h o isotopic studies show that the stage i ore forming fluids consist predominantly of high salinity evolved seawater 125 220 c 23 9 27 9 wt nacl equiv and some magmatic hydrothermal fluids 249 339 c 34 5 42 2 wt nacl equiv the two fluid end members are represented by the l type fis in q1 and the s and v type fis in q2 the temperature and salinity variation trends of the l type fis in q1 indicate a mixing process between the hot evolved seawater and cold seawater at stage i furthermore the v and s type fi coexistence in q2 and their microthermometric data suggest that fluid unmixing has occurred in original magmatic fluids at stage i in contrast the stage ii ore forming fluids consist of ch4 rich metamorphic fluids 192 350 c 10 6 43 2 wt nacl equiv carbon isotopic analysis of the stage ii calcite 4 58 to 10 83 and graphite 32 01 to 39 16 in the ore hosting chlorite schist indicates that the metamorphic ore forming fluids had exchanged carbon isotope with graphite the generation of ch4 may have resulted from the interaction between h2o released by metamorphic devolatilization and graphite the continuous consumption of h2o in the hydrothermal fluid system may have increased the fluid salinity and triggered fluid unmixing in the ch4 nacl h2o system in addition the vms metallogenic environment is generally favorable for microbial communities it is considered that the graphite at luojiahe may have been derived from sedimentary organic matter formed in seafloor hydrothermal vent systems as also supported by carbon isotopic data we propose that at stage i the main mineralization may have been resulted from 1 fluid mixing of hot evolved seawater and cold seawater in the near surface environment and 2 fluid unmixing caused by the percolation of magmatic fluids into syn volcanic faults forming the stockwork ores at stage ii the interaction between h2o and graphite may have resulted in the reduction of ore forming fluids and cu precipitation and fluid unmixing in the ch4 nacl h2o system may have further promoted the cu mineralization

drumlins and the dynamics of the subglacial environment abstract this volume contains a selection of papers presented at the vii international drumlin symposium westport ireland in may 2009 this introduction to the volume first outlines the significance of drumlins as a key subglacial bedform gives a brief history of drumlin research and identifies the major themes of subglacial research namely mapping and morphometry sedimentary and ice bed processes and glacier dynamics it then summarises in turn the major findings of the papers in this volume linking them to each other and to the wider literature finally this introductory paper considers future developments in studies of drumlins and the subglacial environment

erratum to variations of sulphur isotope signatures in sulphides from the metamorphosed ming cu au volcanogenic massive sulphide deposit newfoundland appalachians canada the ming deposit is an early ordovician bimodal mafic cu au volcanogenic massive sulphide vms deposit in the newfoundland appalachians that was metamorphosed to upper greenschist lower amphibolite facies conditions and deformed in the silurian and devonian the ming deposit consists of several spatially proximal ore bodies of which the 1806 zone 1807 zone ming south up plunge and down plunge and the lower footwall zone are the focus of this paper the ore bodies have similar stratigraphic sequences the ore bodies can be divided into 1 a silicified horizon that caps the massive sulphides 2 semi massive to massive sulphides and 3 sulphide mineralization in a rhyodacitic footwall sulphide mineralization in a rhyodacitic footwall includes a sulphide stringers immediately below the semi massive to massive sulphides and b chalcopyrite pyrrhotite pyrite stringers distally from semi massive to massive sulphides in the lower footwall zone pyrite chalcopyrite pyrrhotite arsenopyrite and galena were analysed by in situ secondary ion mass spectrometry sims for sulphur isotope compositions the isotopic signatures of pyrite chalcopyrite pyrrhotite and arsenopyrite fall within a limited range of 2 8 to 12 0 for semi massive to massive sulphides and sulphide mineralization in the footwall the silicified horizon capping the semi massive to massive sulphides has higher 34s 5 8 19 6 especially for pyrrhotite mean 17 2 2 2 n 8 the sulphur isotope composition of galena is more heterogeneous especially within semi massive to massive sulphides and sulphide stringers ranging from 0 8 to 17 3 mean 6 1 4 3 n 35 and 7 6 to 17 1 mean 13 7 5 3 n 3 respectively geothermometric calculations give insufficient formation and metamorphism temperatures for neighbouring mineral pairs because sulphides were not in isotopic equilibrium while deposited in early ordovician or re equilibrated during silurian devonian metamorphism respectively therefore original isotopic compositions of sulphides at the ming deposit have been preserved modelling of the source of sulphur shows that 1 reduced seawater sulphate and 2 sulphur leached from igneous wall rock and or derived from magmatic fluids are the main sources of sulphur in the ming deposit the influence of igneous sulphur igneous wall rock magmatic fluids increases with temperature and is an important sulphur source for the semi massive to massive sulphides and footwall mineralization in addition to a contribution from thermochemical sulphate reduction tsr of seawater it is difficult to distinguish between sulphur leached from igneous rocks and magmatic fluid related sulphur and it is possible that both sources contributed to the ores at the ming deposit in addition to igneous sulphur the heavy isotopes of the silicified horizon are consistent with the sulphur in this horizon being derived only from thermochemical sulphate reduction of early ordovician seawater sulphate

lithological mapping of the troodos ophiolite cyprus using airborne lidar topographic data traditional field based lithological mapping can be a time consuming costly and challenging endeavour when large areas need to be investigated where terrain is remote and difficult to access and where the geology is highly variable over short distances consequently rock units are often mapped at coarse scales resulting in lithological maps that have generalised contacts which in many cases are inaccurately located remote sensing data such as aerial photographs and satellite imagery are commonly incorporated into geological mapping programmes to obtain geological information that is best revealed by overhead perspectives however spatial and spectral limitations of the imagery and dense vegetation cover can limit the utility of traditional remote sensing products the advent of airborne light detection and ranging lidar as a remote sensing tool offers the potential to provide a novel solution to these problems because accurate and high resolution topographic data can be acquired in either forested or non forested terrain allowing discrimination of individual rock types that typically have distinct topographic characteristics this study assesses the efficacy of airborne lidar as a tool for detailed lithological mapping in the upper section of the troodos ophiolite cyprus morphometric variables including slope curvature and surface roughness were derived from a 4 m digital terrain model in order to quantify the topographic characteristics of four principal lithologies found in the area an artificial neural network the kohonen self organizing map was then employed to classify the lithological units based upon these variables the algorithm presented here was used to generate a detailed lithological map which defines lithological contacts much more accurately than the best existing geological map in addition a separate map of classification uncertainty highlights potential follow up targets for ground based verification the results of this study demonstrate the significant potential of airborne lidar for lithological discrimination and rapid generation of detailed lithological maps as a contribution to conventional geological mapping programmes

automatic relief classification versus expert and field based landform classification for the medium altitude mountain range the sudetes sw poland abstract the main purpose of the study is to compare the results of automatic classification of landforms performed as unsupervised classification and manual expert morphographic landform classification derived from field mapping and recognition of long term trends in landform evolution two test areas in the sudetes mountains sw poland were selected each representing a different type of relief the jelenia gora basin is an example of denudational hilly granite topography with inselbergs other residual hills and basins whereas the northern part of the bystrzyckie mountains is a faulted plateau underlain by sedimentary and metamorphic rocks the setup of the classification involved a dem derived from digitalization of 1 25 000 maps a filter mask of 20 20 pixels 500 500 m k median cluster analysis and consideration of four dimensions relative height slope combined curvature and aspect we used a statistical criterion to decide the level of classification i e the number of homogeneous groups returned output maps show the results of classification into five jelenia gora basin or six groups bystrzyckie mountains later confronted with nine group classification in both areas automatic classification for k 5 6 performed well and the principal features of relief are well captured despite very different landform patterns and long term geomorphic histories slope and curvature are the main variables to differentiate individual terrain units landforms with an additional role of aspect in the faulted and tilted plateau for k 6 aspect becomes the main variable in the hilly relief and the pattern of terrain units becomes more fragmented adversely impacting on the clarity of interpretation while surfaces in the faulted plateau setting are further subdivided according to slope and curvature the match between expert maps and the results of automatic classification varies depending on the landforms considered while certain landforms are clearly associated with one particular group yielded by automatic classification others fall into a number of groups and do not have distinctive signatures despite different origins

the critical point and two phase boundary of seawater 200 500 c abstract the two phase boundary of seawater was determined by isothermal decompression of fully condensed seawater in the range of 200 500 c the pressure at which phase separation occurred for each isotherm was determined by a comparison of the refractive index of fluid removed from the top and bottom of the reaction vessel the critical point was determined to be in the range of 403 406 c 285 302 bar and was located by the inflection in the two phase boundary and by the relative volume of fluid and vapor as a function of temperature the two phase boundary of 3 2 nacl solution was found to coincide exactly with that of seawater over the range tested in the present study the boundary for both is described by a single seventh order polynomial equation the two phase boundary defines the maximum temperature of seawater circulating at depth in the oceanic crust thus the boundary puts a limit of about 390 c for seawater circulating near the seafloor at active ocean ridges 2 5 km water depth and about 465 c at the top of a magma chamber occurring at 2 km below the seafloor

brine pool deposition for the zn pb cu massive sulphide deposits of the bathurst mining camp new brunswick canada i comparisons with the iberian pyrite belt abstract the ordovician zn pb cu massive sulphide ore deposits of the bathurst mining camp share many features with those of the devonian carboniferous iberian pyrite belt particularly the tendency to large size tonnage and metal content shape as far as can be determined after allowing for deformation metal content particularly fe cu pb zn and sn mineral assemblages pyrite arsenopyrite pyrrhotite and lack or rarity of sulphates sulphide textures particularly framboidal pyrite lack of chimney structures and rubble mounds irregular metal or mineral zoning and the low degree of zone refining compared to hokuroku ores the major differences between the provinces are the lack of vent complexes and the presence of sn cu ores in the iberian pyrite belt there are also similarities in the geological setting of the two camps both lie within continental terranes undergoing arc continent and continent continent collision and in each case massive sulphide mineralisation followed ophiolite obduction the ore deposits are associated with bimodal volcanic rocks derived from morb and continental crust and marine shales and mineralisation was locally accompanied or followed by deposition of iron formations fluid inclusion data from veins in stockworks from at least six of the iberian massive sulphide deposits point to sulphide deposition having taken place in basins containing mostly spent saline ore forming fluids brine pools and it is suggested that most of the major features of the bathurst deposits can be explained by similar processes the proposed model is largely independent of ocean sulphate and o 2 content whereas low values of each are requisites for the current spreading plume model of sulphide deposition in the bathurst camp

biogenic and thermogenic sulfate reduction in the sullivan pb zn ag deposit british columbia canada evidence from micro isotopic analysis of carbonate and sulfide in bedded ores abstract the layered clastic hosted sedex type proterozoic ca 1475 ma sullivan pb zn ag deposit was metamorphosed by several episodes of metamorphic recrystallization that have extensively modified or erased primary grain to grain textural relationships yet genetically significant variations of sulfur and carbon isotope ratios have been preserved at the millimeter and greater scale whereas sulfur isotope fractionations on a grain to grain scale cannot distinguish between likely formation temperatures and post peak metamorphic cooling the preserved fine scale and deposit scale stratigraphic variations of 34 s and 13 c bear on the origin and formational history of this deposit high spatial resolution documentation of accurate grain to grain and stratigraphic sulfur isotope variations in selected portions of bedded ore from the sullivan deposit was made possible by use of a cold stage during in situ laser assisted isotopic analysis pyrrhotite formed from biogenic sulfate reduction in the water column can be distinguished from sulfides e g sphalerite with higher 34 s values that formed in response to hydrothermal fluids in a brine pool isotopic analysis of carbonates in the presence of abundant sulfides was facilitated by development of a gas chromatographic carbonate extraction system with a high efficiency cryogenic trap calcite present in interlayered massive sulfide and siliciclastic layers in the bedded ore zone in trace amounts to a few weight percent records a carbon isotopic stratigraphy that suggests variable thermogenic sulfate reduction stratigraphic curves illustrating the variation in carbon and sulfur isotopes from the base of the main band to above the hu bands mine stratigraphic names in the bedded ore zone are similar in shape values of 13 c decrease abruptly at the base of the main band decrease slightly to the c band then increase to pre ore values the values of 34 s decrease from the base of the main band to the c band and then increase to pre ore values this similarity suggests some linkage between carbon and sulfur isotopic systematics and a sulfur budget dominated in the early stages of massive sulfide precipitation by hydrothermal processes involving thermogenic sulfate reduction giving way to bacteriogenic sulfate reduction in a closed then finally open marine basin

bacteria were responsible for the magnitude of the world class hydrothermal base metal sulfide orebody at navan ireland we report sulfur and lead isotope analyses of mine concentrates from navan the largest zinc deposit in ireland these samples each representing up to a million tonnes of ore show very limited isotopic variation with mean 34 s 13 6 2 per mil n 20 and galena concentrate mean 206 pb 204 pb 18 19 0 03 n 7 calculations suggest 90 percent of the navan sulfides were derived through bacteriogenic reduction of mississippian seawater sulfate whereas metals were acquired from a local orogenic crustal source beneath the orebody enhanced bacterial activity was fundamental to ore deposition at navan no bacteria no giant ore deposit

volcanic and structural reconstruction of the deformed and metamorphosed ming volcanogenic massive sulfide deposit canada implications for ore zone geometry and metal distribution

sphalerite geobarometry and arsenopyrite geothermometry applied to metamorphosed sulfide ores in the swedish caledonides metamorphosed massive sulfide deposits in the swedish caledonides were investigated using sphalerite geobarometry and arsenopyrite geothermometry the sphalerite investigations yield pressure estimates of 3 to 5 kb for six deposits from host rocks of greenschist lower amphibolite facies a bimodal fes distribution is apparent for the chlorite grade deposits whereas the fes distribution in biotite grade deposits is unimodal the arsenopyrite geothermometry is apparently sensitive to high contents 0 2 wt of either of the trace elements co and ni and possibly also of sb temperature estimates for six deposits from the chlorite zone of greenschist facies yield 371 degrees or 45 degrees c whereas one deposit from the biotite zone gives a temperature of 422 degrees or 25 degrees c the pressure and temperature data obtained for the deposits correspond excellently with the metamorphic grade of the host rocks thus sphalerite geobarometry and arsenopyrite geothermometry can be applied successfully to metamorphosed sulfide orebodies if attention is paid to textural relationships and minor element distribution in the minerals investigated

isotope geochemistry tracks the maturation of submarine massive sulfide mounds iberian pyrite belt the massive sulfide deposits of the southern iberian pyrite belt ipb occur as shale hosted exhalative mounds or shallow sub seafloor replacive bodies that formed at the devonian carboniferous boundary in anoxic bottoms the geochemistry of the mineralization and the host shale from some of the major deposits including a detailed 50 m thick section through the migollas orebody shows a marked textural and vertical zonation that is also reflected in the chemical textural and isotopic variations of pyrite and carbonates pyrite evolves from primary framboids and colloform aggregates to late euhedral crystals which accompanies a redistribution of the contained base metals and grain coarsening sims analyses depict an extreme variability of 34s values from 42 3 to 4 4 with a gradual increase that is related to the textural maturation there is also a systematic rise in the 87sr 86sr ratios 0 70846 to 0 71354 13c 12 2 to 5 2 and 18o values 14 1 to 27 8 of the associated carbonates which evolve from early dolomite to late siderite this evolution evidences the maturation of the exhalative mineralization during mixing between two fluids modified seawater enriched in biogenically derived reduced sulfur and upflowing hydrothermal fluids early sulfides precipitated in the seawater mound interface towards the core of the mounds there was an increasing influence of deep fluids that modified the early mineral textures and the isotopic signatures this evolution is similar to that observed in modern submarine hydrothermal systems and confirms the importance of mound refining in the evolution of fossil exhalative mounds and the formation of economic ores

supervised classification of types of glaciated landscapes using digital elevation data abstract automated approaches for identifying different types of glaciated landscapes using digitally processed elevation data were evaluated we tested the ability of geomorphic measures e g elevation relative relief roughness and slope gradient derived from digital elevation models dems to differentiate glaciated landscapes using maximum likelihood classification and artificial neural networks ann the automated methods were trained and validated using an existing quaternary geology map and a manual interpretation of the contour data portrayed on topographic quadrangles the need for such methods arises from efforts to classify types of landscapes e g ecoregions in michigan one fundamental control of the landscape structure in michigan including soil type and vegetation is the underlying sedimentary and landform assemblages produced by an array of glacial processes during the waning phase of the pleistocene traditional methods for identifying different landscapes e g ice contact landscapes stagnation landscapes have relied on printed topographic maps and have been very effective but time consuming the maps resulting from the four supervised classification trials had between 51 and 61 agreement with the original quaternary geology map the output from the maximum likelihood classification had slightly higher agreements than the output from the neural net which is attributed to the generalization inherent in the quaternary geology map compared with the nature of the classifier for the neural net the neural net however identifies significant detail and non linear relationships between classification inputs and output classes future work should incorporate a map of soils into the classification

evaluation of current statistical approaches for predictive geomorphological mapping abstract predictive models are increasingly used in geomorphology but systematic evaluations of novel statistical techniques are still limited the aim of this study was to compare the accuracy of generalized linear models glm generalized additive models gam classification tree analysis cta neural networks ann and multiple adaptive regression splines mars in predictive geomorphological modelling five different distribution models both for non sorted and sorted patterned ground were constructed on the basis of four terrain parameters and four soil variables to evaluate the models the original data set of 9997 squares of 1 ha in size was randomly divided into model training 70 n 6998 and model evaluation sets 30 n 2999 in general active sorted patterned ground is clearly defined in upper fell areas with high slope angle and till soils active non sorted patterned ground is more common in valleys with higher soil moisture and fine scale concave topography the predictive performance of each model was evaluated using the area under the receiver operating characteristic curve auc and the kappa value the relatively high discrimination capacity of all models auc 0 85 0 88 and kappa 0 49 0 56 implies that the model s predictions provide an acceptable index of sorted and non sorted patterned ground occurrence the best performance for model calibration data for both data sets was achieved by the cta however when the predictive mapping ability was explored through the evaluation data set the model accuracies of cta decreased clearly compared to the other modelling techniques for model evaluation data mars performed marginally best our results show that the digital elevation model and soil data can be used to predict relatively robustly the activity of patterned ground in fine scale in a subarctic landscape this indicates that predictive geomorphological modelling has the advantage of providing relevant and useful information on earth surface processes over extensive areas such data being unavailable through more conventional survey methods

numerical modeling of valley glacier stagnation as a paleoclimatic indicator stagnation of the terminal region of a glacier occurs in response to sufficiently large and rapid climatic warming so the presence of stagnation deposits provides quantitative information on the climate change that forced retreat here we use a simple flow line glacier model to investigate the relationship between stagnation climate forcing and aspects of the glacier bed for climatic warming greater than the threshold to cause stagnation larger or faster warming events cause longer regions of a glacier to stagnate smaller or slower warming episodes below the threshold for stagnation cause retreat while active flow persists along the entire glacier length the threshold for stagnation depends not only on the climatic forcing but also on many other aspects of the glacier with stagnation favored by factors including a lower mean bed slope with greater roughness quantitative determination of the climatic forcing consistent with the occurrence or absence of stagnation deposits requires that these site specific characteristics be incorporated in modeling

a semipermeable interface model for the genesis of subseafloor replacement type volcanogenic massive sulfide vms deposits subseafloor replacement style volcanogenic massive sulfide vms deposits are a subset of vms deposits where sulfides have replaced unconsolidated volcanic volcano sedimentary and sedimentary material these deposits are anomalously large and are important global sources of metals they have distinct textures at the sulfide ore interface including bed by bed replacement of sedimentary layers and typically fill void space between unconsolidated volcaniclastic detritus or fractures in flows or intrusions at the microscale metalbearing sulfides have partially to fully replaced framboidal bacteriogenic sulfides or the framboidal sulfides have acted as nuclei upon which additional metalliferous massive sulfide is deposited the textures presented are reconciled within a semipermeable interface model for replacement in this model unconsolidated sediment volcaniclastic rocks or fractured coherent volcanic rocks provide a permeable to semipermeable interface that allowed ingress of cold seawater into the pore spaces of the stratigraphic sequence prior to and during lulls in hydrothermal activity seawater sulfate in the pore water is partially reduced by bacteria to provide reduced sulfur h2s as well as framboidal pyrite in the host sequence s the reduced sulfur and framboidal pyrite as well as the cool pore water provided a thermal redox and chemical gradient in which upwelling hydrothermal fluids interact in such an environment rising hydrothermal fluids mix with cold water not only at the seawater interface leading to exhalative sulfide deposition but also in the subseafloor leading to sulfide precipitation via replacement the upwelling hydrothermal fluids can also interact with bacterial h2s in the pore spaces of the unconsolidated material resulting in additional subseafloor precipitation of metal sulfides the fluids also result in replacement of framboidal pyrite nuclei pseudomorphous after the original framboidal masses this semipermeable interface also favors enhanced zone refining assuming the hydrothermal system is sufficiently long lived leading to upgrading of the tenor of the sulfides with well developed metal zoning as observed in many ancient replacement type deposits furthermore the precipitation of a significant subseafloor sulfide mineralization results in greater trapping of metals from upwelling fluids and larger tonnage deposits with greater contained metal this model may also be applicable to other replacement type deposits in broadly similar geologic and hydrothermal environments e g sediment hosted and irish type zn pb deposits additional critical tests are required to validate and refute the model and potential tests are presented herein

influence of method selection on clustering analyses of point like features examples from three zones of distributed volcanism abstract most regions that have experienced spatially distributed volcanism also present a clustered structure of eruptive vents attempts to identify patterns from the spatial distribution of vents have resorted to various methods the influence that specific methods might have on the identified patterns however has remained largely unexplored in this work i assess the ability of common out of the box algorithms to yield consistent results the geological significance of those groupings is also tested the results of those tests indicate that method selection exerts a strong influence and therefore introduces undesired biases on the identification of groups on zones of distributed volcanism the results reported below indicate that it is almost impossible to capture the fine structure of volcanic clusters by focusing on a single value that best describes spatial distribution nevertheless an alternative approach that could reduce the negative influence of such method dependence is outlined this method searches for core groups as the membership identified on each group by more than one algorithm despite the limited ability of this method to reproduce pre existing geologic or tectonic partitions it provides grounds for a more robust interpretation of results than the use of only one out of the box method in isolation

extreme sulfur isotope fractionation in the late devonian dry creek volcanogenic massive sulfide deposit central alaska abstract the dry creek zn pb cu ag au volcanogenic massive sulfide vms deposit in east central alaska occurs in a late devonian sequence of peralkaline rhyolite tuff minor graphitic argillite and local peralkaline quartz porphyry rhyolite intrusions principal mineralized facies are semi massive and massive sulfide in variably silicified and graphitic rhyolite tuff massive sulfide in graphitic argillite disseminated sulfides in graphitic and non graphitic rhyolite tuff and vein hosted sulfides in a subvolcanic peralkaline quartz porphyry intrusion in situ analysis of the sulfur isotope composition of sulfide minerals from all facies of the deposit shows a total range in 34s values from 48 0 to 23 1 this remarkable 71 1 variation is more than twice the largest range known for sulfides in nearly all individual vms deposits both modern and ancient which typically is high precision ca id tims u pb geochronology of zircons from a synvolcanic peralkaline quartz porphyry intrusion yields a weighted mean 206pb 238u date of 363 02 0 43 ma 2 total uncertainty this date indicates that the formation of graphitic and sulfidic sediments at dry creek and contemporaneous vms mineralization occurred at least 3 6 m y before and hence are unrelated to widespread black shale deposition during the hangenberg event at ca 359 ma

geomorphometric feature analysis using morphometric parameterization and artificial neural networks this paper presents a semi automatic method using an unsupervised neural network to analyze geomorphometric features as landform elements the shuttle radar topography mission srtm provided detai

late pleistocene glaciation of the kleiner arbersee area in the bavarian forest south germany abstract during pleistocene mountain glaciation of the bavarian forest south germany the wurmian kleiner arbersee glacier left behind glacial landforms and sediments which are described classified and interpreted using a combination of geomorphological sedimentological pedological surveying and absolute dating methods the latest kleiner arbersee glacier with a maximum length of 2600 m a minimum width of 800 m and a thickness of 115 m formed an elongated cirque four lateral moraines one divided end moraine one recessional moraine a proglacial lake and a basin in which lake kleiner arbersee was established after deglaciation beyond the glacial limit the landscape is denuded by periglacial slope deposits which are differentiated from the glacigenic sediments based upon clast fabrics clast shapes and sediment consolidation within the glacial limit sandy gravelly to silty gravelly tills are widely distributed whereas glaciolacustrine sediments are restricted to a small area north of the lake small variations in the sand and silt fraction of the tills are explained by melt out processes quartz mica and chlorite derived from gneiss bedrock are dominant in the clay mineral spectrum of tills but also gibbsite as a product of pre pleistocene weathering is present giving evidence of glacially entrained saprolites an irsl date of glaciolacustrine sediments 32 4 9 4 ka bp confirms the wurmian age for the glaciation and radiocarbon ages of the basal sediments 12 3 0 4 and 12 5 0 2 ka bp uncalibrated in the lake kleiner arbersee prove that the basin was ice free before the younger dryas

supervised landform classification of northeast honshu from dem derived thematic maps this paper proposes a quantitative method to classify landforms using four morphometric parameters from dem derived thematic raster maps of slope and topographic openness because the different surficial processes and stages in the evolution of slopes create landscapes with different shapes these parameters may lead to a genetic interpretation of topography the raster maps of slope and topographic openness were constructed for northeast honshu japan from 50 m dems the mean and standard deviation of morphometric parameters within a 3050m by 3050m moving window on the raster maps were calculated the results for some training areas show that constructional depositional and erosional landforms with different relief have different morphometric characteristics a supervised landform classification for northeast honshu using the knowledge from the training areas revealed a ladder geomorphological structure composed of high mountains ranges and volcanoes the close relationship between the ladder geomorphological structure and volcano distribution indicates that the structure reflects the magmatic plumbing system from the upper mantle to the crust of the northeast honshu arc

integrating airborne multispectral imagery and airborne lidar data for enhanced lithological mapping in vegetated terrain practical and financial constraints associated with traditional field based lithological mapping are often responsible for the generation of maps with insufficient detail and inaccurately located contacts in arid areas with well exposed rocks and soils high resolution multi and hyperspectral imagery is a valuable mapping aid as lithological units can be readily discriminated and mapped by automatically matching image pixel spectra to a set of reference spectra however the use of spectral imagery in all but the most barren terrain is problematic because just small amounts of vegetation cover can obscure or mask the spectra of underlying geological substrates the use of ancillary information may help to improve lithological discrimination especially where geobotanical relationships are absent or where distinct lithologies exhibit inherent spectral similarity this study assesses the efficacy of airborne multispectral imagery for detailed lithological mapping in a vegetated section of the troodos ophiolite cyprus and investigates whether the mapping performance can be enhanced through the integration of lidar derived topographic data in each case a number of algorithms involving different combinations of input variables and classification routine were employed to maximise the mapping performance despite the potential problems posed by vegetation cover geobotanical associations aided the generation of a lithological map with a satisfactory overall accuracy of 65 5 and kappa of 0 54 using only spectral information moreover owing to the correlation between topography and lithology in the study area the integration of lidar derived topographic variables led to significant improvements of up to 22 5 in the overall mapping accuracy compared to spectral only approaches the improvements were found to be considerably greater for algorithms involving classification with an artificial neural network the kohonen self organizing map than the parametric maximum likelihood classifier the results of this study demonstrate the enhanced capability of data integration for detailed lithological mapping in areas where spectral discrimination is complicated by the presence of vegetation or inherent spectral similarities

remote sensing and gis investigation of glacial features in the region of devil s lake state park south central wisconsin usa abstract this study utilizes landsat tm aster and synthetic aperture radar sar derived dems in conjunction with geographic information systems gis in order to reevaluate previously published interpretations of glacial landforms in and around devil s lake state park south central wisconsin usa devil s lake sits in a gorge carved into the southern flank of a doubly plunging syncline known as the baraboo hills through which the wisconsin or some other river flowed prior to the last ice age during the last glacial maximum about 18 000 b p an outlet glacier of the laurentide ice sheet called the green bay lobe extended southward into south central wisconsin and left behind extensive glacial landforms such as moraines drumlins and eskers during advance of the green bay lobe into the region devil s lake gorge was plugged at both ends by glacial deposits and resulted in formation of devil s lake the wisconsin river if it originally flowed through devil s lake gorge found a new course to the east of the baraboo hills syncline this study utilizes the aforementioned remote sensing data to spatially image the following features 1 original extent of the green bay lobe 2 moraines and streamlined glacial landforms as indicators of ice flow directions and 3 former path of the old wisconsin or some other river prior to being rerouted by the green bay lobe gis analysis is also performed in order to test published interpretations of the regional glacial history this study confirms that glacial features observed today are consistent with the former advance of the green bay lobe into the area formation of glacial lake wisconsin plugging of devil s lake gorge by a moraine to form devil s lake and subsequent glacial retreat leading to the breaching of an ice dam and catastrophic flooding by 14 000 years ago the large aerial coverage of satellite imagery with resolutions up to 15 m are valuable for reevaluating regional interpretations previously based on local field mapping and aerial photography of limited extent

the interplay of evolved seawater and magmatic hydrothermal fluids in the 3 24 ga panorama volcanic hosted massive sulfide hydrothermal system north pilbara craton western australia the 3240 ma panorama volcanic hosted massive sulfide vhms district is unusual for its high degree of exposure and low degree of postdepositional modification in addition to typical seafloor vhms deposits this district contains greisen and vein hosted mo cu zn sn mineral occurrences that are contemporaneous with vhms orebodies and are hosted by the strelley granite complex which also drove vhms circulation hence the panorama district is a natural laboratory to investigate the role of magmatic hydrothermal fluids in vhms hydrothermal systems regional and proximal high temperature alteration zones in volcanic rocks underlying the vhms deposits are dominated by chlorite quartz albite assemblages with lesser low temperature sericite quartz k feldspar assemblages these assemblages are typical of vhms hydrothermal systems in contrast the alteration assemblages associated with granite hosted greisens and veins include quartz topaz muscovite fluorite and quartz muscovite sericite chlorite ankerite these vein systems generally do not extend into the overlying volcanic pile fluid inclusion and stable isotope studies suggest that the greisens were produced by high temperature 590 c high salinity 38 56 wt nacl equiv fluids with high densities 1 3 g cm3 and high 18o 9 3 0 6 these fluids are compatible with the measured characteristics of magmatic fluids evolved from the strelley granite complex in contrast fluids in the volcanic pile including the vhms ore forming fluids were of lower temperature 90 270 c lower salinity 5 0 11 2 wt nacl equiv with lower densities 0 88 1 01 g cm3 and lower 18o 0 8 2 6 these fluids are compatible with evolved paleoarchean seawater fluids that formed the quartz chalcopyrite sphalerite cassiterite veins which are present within the granite complex near the contact with the volcanic pile were intermediate in temperature and isotopic composition between the greisen and volcanic pile fluids t 240 315 c 18o 4 3 1 5 and are interpreted to indicate mixing between the two end member fluids evidence of mixing between evolved seawater and magmatic hydrothermal fluid within the granite complex together with the lack of evidence for a magmatic component in fluids from the volcanic pile suggest partitioning of magmatic hydrothermal from evolved seawater hydrothermal systems in the panorama vhms system this separation is interpreted to result from either the swamping of a relatively small magmatic hydro thermal system by evolved seawater or density contrasts precluding movement of magmatic hydrothermal fluids into the volcanic pile variability in the salinity of fluids in the volcanic pile combined with evidence for mixing of low and high salinity fluids in the massive sulfide lens is interpreted to indicate that phase separation occurred within the panorama hydrothermal system although we consider this phase separation to have most likely occurred at depth within the system as has been documented in modern vhms systems the data do not allow the location of the inferred phase separation to be determined

gold in the brunswick no 12 volcanogenic massive sulfide deposit bathurst mining camp canada evidence from bulk ore analysis and laser ablation icp ms data on sulfide phases the 329 mt brunswick no 12 volcanogenic massive sulfide deposit total resource of 163 mt at 10 4 zn 4 2 pb 0 34 cu and 115 g t ag is hosted within a middle ordovician bimodal volcanic and sedimentary sequence massive sulfides are for the most part syngenetic and the bulk of the sulfide ore occurs as a zn pb rich banded sulfide facies that forms an intimate relationship with a laterally extensive algoma type iron formation and defines the brunswick horizon zone refining of stratiform sulfides is considered to have resulted in the development of a large replacement style cu rich basal sulfide facies which is generally confined between the banded sulfide facies and an underlying stringer sulfide zone complex polyphase deformation and associated lower to upper greenschist facies regional metamorphism is responsible for the present geometry of the deposit textural modification has resulted in a general increase in grain size through the development of pyrite and arsenopyrite porphyroblasts which tend to overprint primary mineral assemblages despite the heterogeneous ductile deformation primary features have locally been preserved such as fine grained colloform pyrite and base and precious metal zonation within the main zone base metal and trace element abundances in massive sulfides from the brunswick no 12 deposit indicate two distinct geochemical associations the basal sulfide facies characterized by a proximal high temperature hydrothermal signature cu co bi se contains generally low au contents averaging 0 39 ppm n 34 conversely au is enriched in the banded sulfide facies averaging 1 1 ppm au n 21 and is associated with an exhalative suite of elements zn pb as sb ag sn finely laminated sulfide lenses hosted by iron formation at the north end of the main zone are further enriched in au averaging 1 7 ppm n 41 and ranging up to 8 2 ppm laser ablation inductively coupled plasma mass spectrometry icp ms analyses of pyrite n 97 from the north end of the main zone average 2 6 ppm au and range from the detection limit 0 015 ppm to 21 ppm overall these analyses reveal a distinct au sb as ag hg mn association within pyrite grains gold is strongly enriched in large pseudo primary masses of pyrite that exhibit relict banding and fine grained cores smaller euhedral pyrite porphyroblasts and euhedral rims of metamorphic origin surrounding the pyrite masses contain much less au sb ag as and sn arsenopyrite occurring chiefly as late porphyroblasts contains less au averaging 1 0 ppm and ranging from the detection limit 0 027 ppm to 6 9 ppm depth profiles for single spot laser ablation icp ms analyses of pyrite and arsenopyrite display uniform values of au and an absence of discrete microscopic inclusions of au bearing minerals which is consistent with chemically bonded au in the sulfide structure the pervasive correlation of au with sn in the zn pb rich banded sulfide facies suggests similar hydrothermal behavior during the waxing stages of deposition on the seafloor under high temperature 350oc and moderate to low ph conditions au and sn in hydrothermal fluids would be transported as chlorocomplexes an abrupt decrease in temperature and ah2s accompanied by an increase in fo2 and ph during mixing with seawater would lead to the simultaneous destabilization of both au and sn chlorocomplexes the enrichment of au in fine grained laminated sulfides on the periphery of the deposit accompanied by sporadic occurrences of barite and fe poor sphalerite supports lower hydrothermal fluid temperatures analogous to white smoker activity on the flanks of a large volcanogenic massive sulfide system in lower temperature 350oc and mildly acidic hydrothermal fluids au would be transported by thiocomplexes which exhibit multifunctional retrograde prograde solubility and a capacity to mobilize au to the outer parts of the sulfide mound the sluggish nature of this low temperature venting together with larger variations in ambient fo2 could lead to a sharp enrichment of au towards the stratigraphic hanging wall of massive sulfide deposits

geomorphons a pattern recognition approach to classification and mapping of landforms abstract we introduce a novel method for classification and mapping of landform elements from a dem based on the principle of pattern recognition rather than differential geometry at the core of the method is the concept of geomorphon geomorphologic phonotypes a simple ternary pattern that serves as an archetype of a particular terrain morphology a finite number of 498 geomorphons constitute a comprehensive and exhaustive set of all possible morphological terrain types including standard elements of landscape as well as unfamiliar forms rarely found in natural terrestrial surfaces a single scan of a dem assigns an appropriate geomorphon to every cell in the raster using a procedure that self adapts to identify the most suitable spatial scale at each location as a result the method classifies landform elements at a range of different spatial scales with unprecedented computational efficiency a general purpose geomorphometric map an interpreted map of topography is obtained by generalizing allgeomorphons to a small number of the most common landform elements due to the robustness and high computational efficiency of the method high resolution geomorphometric maps having continental and even global extents can be generated from giga cell dems such maps are a valuable new resource for both manual and automated geomorphometric analyses in order to demonstrate a practical application of this new method a 30 m cell 1 geomorphometric map of the entire country of poland is generated and the features and potential usage of this map are briefly discussed the computer implementation of the method is outlined the code is available in the public domain

elementary forms for land surface segmentation the theoretical basis of terrain analysis and geomorphological mapping abstract land surface morphology is fundamental to geomorphological mapping and many gis applications review and comparison of various approaches to segmentation of the land surface reveals common features and permits development of a broad theoretical basis for segmentation and for characterization of segments and their boundaries within the context of defining landform units that maximise internal homogeneity and external differences this paper introduces the concept of elementary forms segments units defined by constant values of fundamental morphometric properties and limited by discontinuities of the properties the basic system of form defining properties represents altitude and its derivatives constant values of which provide elementary forms with various types of homogeneity every geometric type of elementary form can be characterized by a defining function which is a specific case of the general polynomial fitted function various types of boundary discontinuity and their connections and transformations into other types of morphological unit boundaries are analysed the wealth of types of elementary forms and their boundaries is potentially unbounded and thus is sufficient to cover the real variety of landforms elementary forms in the basic set proposed here have clear potential for genetic and dynamic interpretation a brief worked example documents the possibility of analytical computation of various models of ideal elementary forms for particular segments of landform ideal elementary forms can be considered as attractors to which the affinity of surface segments can be measured by multivariate statistical methods the use of the concept of elementary forms in landscape segmentation is promising and it could be adapted for elementary segmentation of various other spatial fields