magmatism in the iberian pyrite belt petrological constraints on a metallogenic model igneous formations associated with massive sulphide deposits in the iberian pyrite belt ipb are essentially composed of basic lavas and dolerites and dacitic to rhyolitic volcanites intermediate lavas are subordinate the basic rocks show variable geochemical characteristics lavas and dolerites comparable to recent within plate alkaline basalts seem restricted to the western and southern parts of the ipb whereas basic rocks comparable to continental tholeiites or arc related basalts occur across the whole belt the felsic rocks are classified as calc alkaline and belong to the low al2o3 and high yb type at given sio2 al2o3 and tio2 contents they show variable zr nb and hree contents heavy rare earth element fractionation decreases from the dacites to the rhyolites gd yb n 1 whereas the negative eu anomaly becomes more pronounced the characteristics of the rhyolites are typical of sulphide fertile volcanic packages trace element modelling suggests that the felsic rocks evolved from a dacitic parent magma through fractional crystallization of hornblende and plagioclase partial melting of an amphibolite protolith which appears as the most probable model for the origin of this dacitic magma requires a high t p gradient in the crust the occurrence of alkaline basalts and continental tholeiites is consistent with formation of the ipb in a tensional tectonic setting however the associated island arc tholeiites suggest a location in a domain of plate convergence emplacement in a fore arc basin over a recently accreted crustal segment is envisaged as a possible hypothesis to account for the geological and petrological constraints a high geothermal gradient and eruption in a submarine tensional basin could have been two key ingredients for the development of massive sulphide deposits within the ipb

facies architecture of a silicic intrusion dominated volcanic centre at highway reward queensland australia abstract the highway reward massive sulphide deposit is hosted by a silicic volcanic succession in the cambro ordovician seventy mile range group northeastern australia three principal lithofacies associations have been identified in the host succession the volcanogenic sedimentary facies association the primary volcanic facies association and the resedimented syn eruptive facies association the volcanogenic sedimentary facies association comprises volcanic and non volcanic siltstone and sandstone turbidites that indicate submarine settings below storm wave base lithofacies of the primary volcanic facies association include coherent rhyolite rhyodacite and dacite and associated non stratified breccia facies autoclastic breccia and peperite the resedimented volcaniclastic facies association contains clasts that were initially formed and deposited by volcanic processes but then redeposited by mass flow processes resedimentation was more or less syn eruptive so that the deposits are essentially monomictic and clast shapes are unmodified this facies association includes monomictic rhyolitic to dacitic breccia resedimented autoclastic facies siltstone matrix rhyolitic to dacitic breccia resedimented intrusive hyaloclastite or resedimented peperite and graded lithic crystal pumice breccia and sandstone pumiceous and crystal rich turbidites the graded lithic crystal pumice breccia and sandstone facies is the submarine record of a volcanic centre s that is not preserved or is located outside the study area pumice shards and crystals are pyroclasts that reflect the importance of explosive magmatic and or phreatomagmatic eruptions and suggest that the source vents were in shallow water or subaerial settings the lithofacies associations at highway reward collectively define a submarine shallow intrusion dominated volcanic centre contact relationships and phenocryst populations indicate the presence of more than 13 distinct porphyritic units with a collective volume of 0 5 km 3 single porphyritic units vary from the size and shape of the lavas and intrusions reflect a restricted supply of magma during eruption intrusion the style of emplacement and the subaqueous emplacement environment due to rapid quenching and mixing with unconsolidated clastic facies the sills and cryptodomes did not spread far from their conduits the shape and distribution of the lavas and intrusions were further influenced by the positions of previously or concurrently emplaced units magma preferentially invaded the sediment avoiding the older units or conforming to their margins large intrusions and their dewatered envelope may have formed a barrier to the lateral progression and ascent of subsequent batches of magma

gravity wave characteristics in the southern hemisphere revealed by a high resolution middle atmosphere general circulation model abstractgravity wave characteristics in the middle to high latitude southern hemisphere are analyzed using simulation data over 3 yr from a high resolution middle atmosphere general circulation model without using any gravity wave parameterizations gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere while the gravity wave energy is generally weak in summer the wave energy distribution in winter is not zonally uniform but it is large leeward of the southern andes and antarctic peninsula linear theory in the three dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector results of ray tracing and cross correlation analyses are consistent with this theoretical expectation the leeward energy propagation extends to several thousand kilometers which explains part of the gravity wave distribution aro

general aspects of a t213l256 middle atmosphere general circulation model 1 a high resolution middle atmosphere general circulation model gcm developed for studying small scale atmospheric processes is presented and the general features of the model are discussed the gcm has t213 spectral horizontal resolution and 256 vertical levels extending from the surface to a height of 85 km with a uniform vertical spacing of 300 m gravity waves gws are spontaneously generated by convection topography instability and adjustment processes in the model and the gcm reproduces realistic general circulation in the extratropical stratosphere and mesosphere the oscillations similar to the stratopause semiannual oscillation and the quasi biennial oscillation qbo in the equatorial lower stratosphere are also spontaneously generated in the gcm although the period of the qbo like oscillation is short 15 months the relative roles of planetary waves large scale gws and small scale gws in maintenance of the meridional structures of the zonal wind jets in the middle atmosphere are evaluated by calculating eliassen palm diagnostics separately for each of these three groups of waves small scale gws are found to cause deceleration of the wintertime polar night jet and the summertime easterly jet in the mesosphere while extratropical planetary waves primarily cause deceleration of the polar night jet below a height of approximately 60 km the meridional distribution and propagation of small scale gws are shown to affect the shape of the upper part of mesospheric jets the phase structures of orographic gws over the south andes and gws emitted from the tropospheric jet stream are discussed as examples of realistic gws reproduced by the t213l256 gcm

ore controls in the charters towers goldfield ne australia constraints from geological geophysical and numerical analyses the approach taken in this paper namely synthesising a wealth of previous information with new data and a genetic model in combination with integrated numerical analyses led to new insights into the geological controls on the localisation of auriferous veins and residual prospectivity of the charters towers goldfield ne australia the method also has implications for the assessment of other mature goldfields worldwide despite a number of different ore controls having operated within the charters towers goldfield the controlling factors can be linked to a single genetic model for orogenic granitoid hosted lode gold mineralisation in a brittle deformation regime d4 of ne sw to nne ssw shortening under conditions of supralithostatic fluid pressure and low stress difference spatial autocorrelation results suggest district scale alignment of the auriferous veins parallel to and overlapping with the ese wnw to e w striking charters towers ravenswood lineament a major crustal boundary in the basement to the ravenswood batholith at the camp scale auriferous veins have abundance and proximity relationships with nw se nnw sse ne sw and ene wsw oriented lineaments suggesting that structures that controlled gold deposition in one camp did not necessarily control mineralisation in other camps fractal dimensions obtained with the box counting method range from 1 02 to 1 10 whereas veins in the charters towers city camp are characterised by a significantly higher fractal dimension of 1 28 this discrepancy may be taken to imply that most or all outcropping and near surface deposits within the charters towers city camp have been found and that new discoveries are more likely to occur at greater levels of depth or outside the boundaries of this camp the new understanding has implications for the assessment of the residual prospectivity of the charters towers goldfield where large areas of prospective rock types and structures e g approximately 40 of the charters towers ravenswood lineament are hidden under cover this parameter space was inaccessible to the historic prospectors and has received relatively little attention from recent explorers the following steps are suggested for the development of a targeting strategy for lode gold exploration in areas of the goldfield under cover 1 identify from geological and geophysical data the ene wsw 15 and nnw sse 15 striking structures and geological boundaries within a 20 km wide corridor parallel to and centred upon the charters towers ravenswood lineament the potential control on gold deposit distribution at the regional to district scale 2 interpret from geological and geophysical data the distribution of pre middle devonian granitoids within these areas that are the preferred host rocks of the payable gold deposits 3 deduce from geophysical data the ene wsw 15 and nnw sse 15 striking structures that cut or bound the intrusions identified in step 2 4 locate segments along the structures identified in step 3 that deviate most from the geometry of a straight line e g potential bends or splays and or intersect other structures or geological contacts or both and 5 define and rank potential targets within the prospective areas identified in step 4 and systematically test the best ones

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

widespread solid particle formation by mountain waves in the arctic stratosphere observations of polar stratospheric clouds pscs by lidar show that the clouds often contain solid particles which are most likely composed of nitric acid hydrates however laboratory experiments indicate that such hydrate particles are not easily formed under arctic synoptic scale conditions suggesting that solid psc particles should be rather rare here we show results from a model study indicating that mountain induced mesoscale temperature perturbations may be an important source of nitric acid hydrate particles in the arctic multiple arctic vortex trajectories were combined with a global mountain wave forecast model to calculate the potential for solid particle formation during december and january 1994 1995 the mountain wave model was used to calculate adiabatic cooling over several thousand ridge elements nitric acid hydrate particles were assumed to form in the mountain waves according to several microphysical mechanisms and were then advected using polar vortex filling synoptic trajectories to generate maps of solid particle occurrence the calculations show that mountain waves may be a significant source of pscs containing solid particles that are observed on the synoptic scale in particular the east coast of greenland the norwegian mountains and the urals are found to be solid particle sources with the pscs often predicted to survive several thousand kilometers downstream

trace element geochemistry and petrogenesis of felsic volcanic rocks associated with volcanogenic massive cu zn pb sulfide deposits volcanogenic massive cu zn pb sulfide vms deposits occur primarily in subaqueous rift related environments e g oceanic fore arc arc back arc continental margin or continental are hosted primarily by bimodal mafic felsic volcanic successions and are typically associated with felsic volcanic rocks with specific geochemical characteristics fi alkalic dacites and rhyodacites despite being abundant in the rock record are typically barren some fii calc alkalic rhyodacites and rhyolites host vms deposits but most are barren fiii tholeiitic and fiv depleted rhyolites and high silica rhyolites are much less abundant in the rock record but commonly host vms deposits regardless of age and fiii rhyolites appear to host the largest deposits most petrogenetic models proposed for the formation of fii and fiii fiv felsic volcanic rocks link felsic magma genesis to fractionation processes in high level magma chambers now represented by associated subvolcanic intrusions where the magma is also interpreted to have supplied the heat and or metals required to generate and sustain the vms forming convective hydrothermal system however the relatively constant compositions of fii and fiii fiv felsic volcanic rocks within individual areas the high eruptive temperatures at or above liquidus of fiii rhyolites and the bimodality of vms hosting volcanic successions indicate that fractional crystallization within subvolcanic intrusions could not have generated or significantly modified the compositions of fii and fiii fiv magmas this coupled with detailed geological geochemical and geochronological studies indicates that many of these subvolcanic intrusions were emplaced in multiple phases and that the later most voluminous phases often cut ore associated hydrothermally altered rocks a reassessment of the physical conditions responsible for producing the geochemistry of ore associated fii and fiii fiv felsic volcanic rocks and a review of the compositions of felsic volcanic rocks associated with vms deposits that range in age from mesoarchean to cenozoic provide important constraints on models for vms associated felsic volcanic rocks and their relationship to mineralization the compositions of felsic volcanic rocks may be explained by low to moderate degrees of partial melting of mafic sources at a range of depths within rift environments where the mineralogy and composition of the source regions modes and degrees of partial melting pressure and temperature of melting and to a lesser extent subsequent fractionation processes account for the compositional variations from fi through fii to fiii fiv long lived enhanced heat flow and structural permeability of rift environments that allows partial melting to form some fii rhyolites at midcrustal levels 10 15 km and fiii fiv rhyolites at shallow crustal levels 10 km both within the zone of brittle fracture permeability are essential to sustain the high temperature convective hydrothermal systems that are required to form large vms deposits and camps rift environments contain long lived thermal magmatic and structural corridors that focus magma ascent heat flow high temperature convective hydrothermal systems and emplacement of subvolcanic intrusions that are favorable environments for the formation of vms deposits and fii and fiii fiv felsic volcanic rocks

intermediate sodium potassium mica in hydrothermally altered rocks of the waterloo deposit australia a combined sem emp xrd tem study metastable intermediate na k mica represents a product of hydrothermal alteration in volcanic rocks from the alteration halo of the waterloo massive sulfide deposit australia the xrd pattern of this solid solution between paragonite and muscovite is characterized by a rational series of basal reflections with d values intermediate between the end members transmission electron microscopy revealed that the intermediate na k mica forms thick stacks that belong to a two layer polytype na rich intermediate na k mica typically occurs together with paragonite whereas k rich intermediate na k mica is intergrown with muscovite the intermediate na k mica is interpreted to have formed as a result of the incomplete transformation of k rich mica to na rich mica through dissolution and recrystallization processes driven by compositional changes of the hydrothermal fluids interacting with the volcanic rocks alteration must have proceeded under non equilibrium conditions because the composition of the solid solution falls into the miscibility gap separating paragonite and muscovite

inertia gravity waves spontaneously generated by jets and fronts part i different baroclinic life cycles abstract the spontaneous generation of inertia gravity waves in idealized life cycles of baroclinic instability is investigated using the weather research and forecasting model two substantially different life cycles of baroclinic instability are obtained by varying the initial zonal jet the wave generation depends strongly on the details of the baroclinic wave s development in the life cycle dominated by cyclonic behavior the most conspicuous gravity waves are excited by the upper level jet and are broadly consistent with previous simulations of o sullivan and dunkerton in the life cycle that is dominated by anticyclonic behavior the most conspicuous gravity waves even in the stratosphere are excited by the surface fronts although the fronts are no stronger than in the cyclonic life cycle the anticyclonic life cycle also reveals waves in the lower stratosphere above the upper level trough of the baroclinic wave these waves have not been previously identified in idealized simulations the sensiti

a new geodynamic interpretation for the south portuguese zone sw iberia and the iberian pyrite belt genesis 1 the south portuguese zone spz constitutes the southernmost segment of the variscan iberian massif it is bounded to the north by the beja acebuches ophiolitic complex and related accretionary wedge to the south lie the iberian pyrite belt ipb and flysch deposits forming the southern extent of the zone structural analysis within the spanish side of the spz supports continuous south propagating deformation evolving from early synmetamorphic thrusting in the internal zone to thin skinned tectonics in the southern external domain the accretion of the spz to the ossa morena zone is also witnessed by the presence of various melanges observed throughout the investigated area part of the melanges observed in the ipb are related to the volcanics and mineralizations setting a key point to understand the ipb mineralizations genesis is to constrain the volcanogenic model one underestimated feature is the large amount of submarine calc alkaline ignimbritic facies implying the presence of caldera structures within the province such correlation between caldera environment and ore deposits strongly suggests that the ipb developed in a continental arc our geodynamic model proposes an early north directed subduction associated with the obduction of the oceanic crust toward the south southward this episode is immediately followed by the development of the accretionary prism while farther south a second subduction zone responsible for the arc setting of the ipb initiates subsequent visean continental collision is associated with the deposit of the south propagating flysch and the present geometry of the spz

on the origins of mesospheric gravity waves 1 using hourly data from a three year simulation based on a gravity wave resolving general circulation model we have first inferred a global view of gravity wave sources and propagation affecting significantly the momentum balance in the mesosphere the meridional cross section of momentum fluxes suggests that there are a few dominant propagation paths originating from the subtropics in summer and the middle to high latitudes in winter these gravity waves are focused into the mesospheric jets in their respective seasons acting effectively to decelerate the jets the difference in the source latitudes likely contributes to the hemispheric asymmetries of the jets the horizontal distribution of the momentum fluxes indicates that the dominant sources are steep mountains and tropospheric westerly jets in winter and vigorous monsoon convection in summer the monsoon regions are the most important window to the middle atmosphere in summer because of the easterlies associated with the monsoon circulation

energy enhancements of gravity waves in the antarctic lower stratosphere associated with variations in the polar vortex and tropospheric disturbances 1 gravity waves in the antarctic lower stratosphere are examined using original operational radiosonde data obtained at syowa station 69 0 s 39 6 e with fine vertical resolution in the lower stratosphere the temporal variation in gravity wave energy depends on height in the height region of 13 15 km just above the tropopause the seasonal variation in gravity wave energy is not evident the wave energy is rather enhanced when the absolute value of potential vorticity in the upper troposphere becomes small over syowa station this fact implies that tropospheric disturbances affect the dynamical processes of gravity waves there however the gravity wave energy in the height region of 15 25 km shows clear seasonal variation having a maximum in spring the time variation in gravity wave energy is examined in detail in terms of the polar vortex by using the equivalent latitude coordinate energy enhancements occur when the edge of the polar vortex approaches syowa station and the enhancements are especially large when the polar vortex breaks down in spring these results suggest that height variation in the background atmosphere leads to the difference of wave characteristics between the two height regions the enhancements of wave energy are partly explained as modification of the wave structure by the background wind speed and the static stability but it is also likely that enhancements of wave activity contribute to the energy enhancement at the edge of the polar vortex in spring

the setting style and role of magmatism in the formation of volcanogenic massive sulfide deposits throughout earth s history all volcanogenic massive sulfide vms hosting environments are associated with specific assemblages of mafic and felsic rocks with distinct petrochemistry petrochemical assemblages indicative of formation at anomalously high temperatures within extensional geodynamic environments in mafic dominated juvenile ophiolitic vms environments there is a preferential association with mafic rocks with boninite and low ti tholeiite mid ocean ridge basalt morb and or back arc basin basalt affinities representing forearc rifting or back arc initiation mid ocean ridges or back arc basin spreading or back arc basins respectively felsic rocks in juvenile oceanic arc environments in archean terrains are high field strength element hfse and rare earth element ree enriched in post archean juvenile oceanic arc terrains felsic rocks are commonly hfse and ree depleted and have boninite like to tholeiitic signatures in vms environments that are associated with continental crust i e continental arc and back arc and dominated by felsic volcanic and or sedimentary rocks evolved environments felsic rocks are the dominant hosts to mineralization and are generally hfse and ree enriched with calc alkalic a type and or peralkalic affinities representing continental arc rifts continental back arcs and continental back arcs to continental rifts respectively coeval mafic rocks in evolved environments have alkalic within plate ocean island basalt like and morb signatures that represent arc to back arc rift versus back arc spreading respectively the high temperature magmatic activity in vms environments is directly related to the upwelling of mafic magma beneath rifts in extensional geodynamic environments e g mid ocean ridges back arc basins and intra arc rifts underplated basaltic magma provides the heat required to drive hydrothermal circulation extensional geodynamic activity also provides accommodation space at the base of the lithosphere that allows for the underplated basalt to drive hydrothermal circulation and induce crustal melting the latter leading to the formation of vms associated rhyolites in felsic dominated and bimodal vms environments rifts also provide extensional faults and the permeability and porosity required for recharge and discharge of vms related hydrothermal fluids rifts are also critical in creating environments conducive to preservation of vms mineralization either through shielding massive sulfides from seafloor weathering and mass wasting or by creating environments conducive to the precipitation of subseafloor replacement style mineralization in sedimented rifts subvolcanic intrusions are also products of the elevated heat flow regime common to vms forming environments shallow level intrusive complexes i e within 1 3 km of the seafloor may not be the main drivers of vms related hydrothermal circulation but are likely the manifestation of deeper seated mantle derived heat i e 3 10 km depth that drives hydrothermal circulation these shallower intrusive complexes are commonly long lived i e millions of years and reflect a sustained thermally anomalous geodynamic environment such a thermally anomalous environment has the potential to drive significant hydrothermal circulation and therefore multi phase long lived subvolcanic intrusive complexes are excellent indicators of a potentially fertile vms environment the absence of intrusive complexes however does not indicate an area of low potential as they may have been moved or removed due to post vms tectonic activity in some cases shallow level intrusive systems contribute metals to the vms hydrothermal system

alteration of felsic volcanics hosting the thalanga massive sulfide deposit northern queensland australia and geochemical proximity indicators to ore thalanga is an early ordovician stratiform zn pb cu ag rich massive sulfide deposit in northern queensland australia with a total resource of 6 6 mt of ore the host rock succession consists of variably altered rhyolite in the footwall and a dacite dominated volcano sedimentary sequence in the hanging wall the sulfide deposit and the enclosing volcanic sequence were metamorphosed under upper greenschist conditions a laterally continuous footwall alteration zone extends beneath the entire deposit 3 000 m and to a stratigraphic depth of at least 300 m below the ore lenses the bulk of this zone is occupied by feldspar destructive muscovite biotite chlorite rich mottled alteration facies with disseminated pyrite representing the metamorphic equivalent of phyllosilicate dominated hydrothermal alteration discordant zones of intense quartz pyrite alteration represent the principal fluid pathways during mineralizing hydrothermal activity locally quartz k feldspar alteration facies exist on the fringes of the system and calcareous alteration and chlorite pyrite alteration facies exist in the upper part of footwall rhyolite proximal to sulfide lenses quartz feldspar porphyritic rhyolite laterally surrounding the footwall alteration zone and feldspar porphyritic dacite in the hanging wall are unaltered or weakly altered the compositional diversity of altered footwall rhyolite implies that hydrothermal alteration at thalanga was a complex processes this paper presents a model for the evolution of the footwall alteration zone calcareous alteration probably represents the initial phase of hydrothermal activity this was followed by diffuse upwelling of acidic seawater dominated fluids causing destruction of primary feldspar precipitation of pyrite and formation of hydrothermal sericite chlorite and clay minerals subsequent intense quartz pyrite alteration was directly associated with mineralization the thalanga footwall alteration zone has several geochemical characteristics that show systematic changes with increasing proximity to ore these include na depletion and elevated mg s alteration index ai chlorite carbonate pyrite index ccpi mo bi and as furthermore the x mg of chlorite and biotite increases systematically from values of 0 45 to 0 5 in least altered rhyolite to values 0 9 immediately below ore these geochemical features can be used in exploration for massive sulfide deposits as vectors to ore at the prospect scale and in discrimination of prospective hydrothermal from unprospective diagenetic alteration systems at the regional scale

geochemistry and geochronology of the chatree epithermal gold silver deposit implications for the tectonic setting of the loei fold belt central thailand abstract the chatree deposit is the largest epithermal au deposit in mainland se asia despite its economic significance the stratigraphy age geochemistry and tectonic setting of the host volcanic sequence is poorly documented in the literature the chatree deposit is located between phichit and phetchabun provinces central thailand and is hosted by late permian to early triassic volcaniclastic and volcanogenic sedimentary rocks detailed field mapping u pb zircon dating geochemistry and stratigraphy suggest that the volcanic sequence can be subdivided into four stratigraphic units and two volcanic suites the late permian suite 1 volcanic units are sourced from a more depleted mantle relative to the overlying early triassic suite 2 volcanic units the late permian suite 1 units probably formed immediately after the beginning of subduction and at the creation of a new island arc the less depleted early triassic suite 2 units were erupted during ongoing subduction once the system had achieved a steady state the chatree au mineralization appears to have occurred during the switch between the two mantle sources and this switch of magma source is marked by a mixed volcano plutonic magmatism at the permo triassic boundary ca 250 ma

the origin of chlorite tremolite carbonate rocks associated with the thalanga volcanic hosted massive sulfide deposit north queensland australia the thalanga polymetallic massive sulfide deposit is hosted by felsic volcanics of the cambro ordovician mount windsor subprovince in north queensland the sheetlike sulfide deposit consists of several semiconnected lenses totaling 6 6 million metric tons mt which lie at a single stratigraphic level between underlying subaqueously emplaced rhyolite and overlying dacitic to andesitic lavas sills and volcaniclastic rocks the ores and host rocks have been deformed and metamorphosed to upper greenschist facies associated with the west thalanga orebody are strata bound lenses composed of chlorite tremolite dolomite and calcite that previously have been interpreted as exhalites they extend up to a few hundred meters along the mineralized horizon and locally also exist in the stratigraphic footwall around the fringes of the deposit rhyolitic volcanics beneath the deposit are extensively altered a pervasive sericite chlorite pyrite zone that extends greater than 200 m into the footwall envelops semistratiform proximal quartz pyrite chlorite stringer zones major and trace element geochemical data indicate that zr ti and al remained essentially immobile in the footwall rocks despite intense hydrothermal alteration involving significant mass transfers of mobile elements the chlorite tremolite carbonate assemblages associated with ore lenses have immobile element ratios identical to those of the altered rhyolites carbonate rich assemblages retain some relict spheroidal and rhombic textures in dolomite which suggest formation at an early hydrothermal stage in a matrix of chlorite or in open spaces the chlorite tremolite carbonate rocks probably represent metamorphic equivalents of hydrothermal chlorite quartz dolomite calcite or mg smectite quartz dolomite calcite assemblages the formation of tremolite by metamorphic reaction of quartz and dolomite is consistent with regional metamorphic conditions with allowance for metamorphic decarbonation carbon and oxygen isotope data from dolomite and calcite are consistent with precipitation of primary dolomite at 170 to 250 c from seawater dominated fluid the chlorite tremolite carbonate rocks at thalanga are consequently reinterpreted as altered rhyolitic volcaniclastics containing variable proportions of hydrothermal carbonate they probably formed in a zone of mixing of hydrothermal fluid and seawater in a permeable substrate close to the paleosea floor siliceous ironstones that are present in distal parts of some thalanga ore lenses have very low immobile element contents and are probably true exhalites

detrital zircon ages in neoproterozoic to ordovician siliciclastic rocks northeastern australia implications for the tectonic history of the east gondwana continental margin u pb detrital zircon ages in variably metamorphosed dominantly fine grained clastic successions are used in northeastern australia to identify two major successions along the east gondwana margin the older succession is of probable late neoproterozoic age and is considered part of a passive margin associated with rifting at c 600 ma most detrital zircons have ages in the range 1000 1300 ma and were probably derived from an extension of a late mesoproterozoic 1050 1200 ma orogenic belt from the central australian musgrave complex located 1500 km to the west no evidence has been found for 600 800 ma rifting of a rodinian supercontinent and therefore it is suggested that breakup must have occurred well outboard of the present early palaeozoic east gondwana margin the younger succession is of early palaeozoic age and contains the distinctive 500 600 ma detrital zircon signature that is widespread in east gondwana in addition to some samples with ages in the range 460 510 ma consistent with local igneous sources the younger succession is related to the active margin of gondwana that developed on the former passive margin in a back arc setting and the source of 510 600 ma zircons is considered to be a composite of rift related and back arc volcanic sources

petrogenetic evolution of felsic volcanic sequences associated with phanerozoic volcanic hosted massive sulphide systems the role of extensional geodynamics abstract felsic volcanic hosted massive sulphide deposits form in many different geotectonic environments usually associated with episodes of extension however empirical geochemical links between felsic volcanism geotectonic environment and extensional geodynamics have not been adequately documented so as to distill the fundamental relationships between these features and formation of volcanic hosted massive sulphide vhms mineralization which is important considering most vhms deposits are hosted in felsic volcanic bearing sequences using felsic geochemical data from six different vhms mineralized phanerozoic geotectonic settings it seems that the felsic geochemical data are consistent with the overall geotectonic interpretations for these areas which in turn helps in stratigraphic and geotectonic interpretations for detailed vhms exploration in extensional geodynamic settings bimodal volcanism is common compared to the continuum of compositions observed under compressional to neutral high stress regimes in calc alkaline arc building environments the empirical geochemical metallogenic vhms relationships evident in the archean felsic volcanic rocks in particular the low zr y n yb n 2 o conditions in different source areas and geotectonic environments they seem to be the predominant controls on the compositional evolution of felsic magmas in extensional settings because of the limited degree of assimilation and fractional crystallization afc affecting their compositions with rapid intrusion into the uppermost crust to positions were they achieve neutral buoyancy in the volcanic to subvolcanic environment within plate felsic or a type anorogenic type and anomalous ocean ridge or type felsic magmas that have tholeiitic affinities relatively low alkali elements are common within parts of the volcanic sequences hosting massive sulphide deposits reflecting in part a relationship to extension the high contents of high field strength elements zr ga lree hree y nb etc and other lines of evidence indicate they are relatively high temperature relatively reduced magmas probably derived from previously dehydrated granulitic or melted oceanic simatic or continental sialic crust low p granulites or amphibolites but also in some cases possibly mantle rocks such that they are significantly water undersaturated during melting i e a h 2 o 1 reduced viscosities typical of high temperature melts enable rapid intrusion to higher levels diking vs diapirism higher rates of heat advection from mantle mafic magmas into the thickened oceanic and or continental crust during lithospheric extension are needed to facilitate melting of these rock to form a type and or or type partial melts tholeiitic felsic this usually results in bimodal magmatism as magma mixing is not favored in extensional settings especially at high magma production intrusion and extrusion rates i e high heat flow this would inhibit ferromagnesian phase in particular hornblende and magnetite fractionation especially at low f o 2 in the felsic magmas that would deplete the melt in y hree as well as ore related elements particularly zn which is 2 to 3 times higher in a type and or type rocks compared to other magma types therefore the empirical felsic igneous geochemical metallogenic relationships observed by others low zr y n yb n

microwave limb sounder observations of gravity waves in the stratosphere a climatology and interpretation high horizontal resolution temperature data from the microwave limb sounder mls are analyzed to obtain information about high intrinsic frequency gravity waves in the stratosphere global climatologies of temperature variance at solstice are computed using six years of data a linear gravity wave model is used to interpret the satellite measurements and to infer information about tropospheric wave sources globally uniform sources having several different spectral shapes are examined and the computed variances are filtered in three dimensional space in a manner that simulates the mls weighting functions the model is able to reproduce the observed zonal mean structure thus indicating that the observations reflect changes in background wind speeds and provide little information about the latitudinal variation of wave sources longitudinal variations in the summer hemisphere do reflect source variations since the modeled variances exhibit much less variation in this direction as a consequence of the zonal symmetry of the background winds a close correspondence between the mls variances and satellite observations of outgoing longwave radiation suggests that deep convection is the probable source for these waves the large variances observed over the tip of south america in winter are most certainly linked to orographic forcing but inferences about wave sources in northern hemisphere winter are difficult to make as a result of the high degree of longitudinal and temporal variability in the stratospheric winds comparisons of model results using different source spectra suggest that the tropospheric sources in the subtropics in summer have a broader phase speed spectrum than do sources at middle latitudes in winter

truncated fractal frequency distribution of element abundance data a dynamic model for the metasomatic enrichment of base and precious metals abstract the frequency distributions of elements in rocks and ore deposits do not conform to a universal scaling law but vary in dependence of the mechanism of element enrichment in the present contribution a dynamic model is proposed that describes element enrichments taking place by metasomatic processes causing the formation of hydrothermal ore deposits it is shown that metasomatic element enrichment can result in a fractal distribution of element abundance data in the low concentration region with a smooth truncation at higher concentration values due to the existence of physical upper concentration limits imposed by the mineralogical nature of the ore the developed model is tested on the basis of base and precious metal concentration data determined on diamond drill core samples collected from the waterloo massive sulfide deposit australia it is shown that the frequency distributions of zn pb cu and ag conform relatively well to truncated power law relationships as predicted by the model in contrast the frequency distribution of the au data was found to be better described by the log normal law presumably due to syn genetic processes of element redistribution that have not been modeled by the proposed dynamic model

fluidal clast breccia generated by submarine fire fountaining trooper creek formation queensland australia abstract a distinctive monomictic breccia composed of fluidal and blocky basaltic andesite clasts occurs in a cambro ordovician submarine volcanic succession in northern queensland australia associated with this fluvial clast buccia facies are coherent facies and coarse and fine breccia facies of the same composition the fluidal clast breccia facies is internally massive and 250 m thick varying only in the ratio of fluidal clasts to blocky clasts fluidal clasts range in size from 2 cm to 170 cm and have moderately to highly vesicular cores and thick up to 1 cm non vesicular formerly glassy rims blocky clasts are highly vesicular to non vesicular subaqueous fire fountain breccias are distinguished from subaerial fire fountain breccias by thick glassy margins on fluidal clasts the lack of welding and agglutination and the distinctive association of highly vesicular fluidal clasts with non vesicular angular blocky clasts recognition of submarine fire fountain breccias in volcanic successions constrains the eruption style proximity tens of metres to source and environment of deposition

geochemistry of the mount windsor volcanics implications for the tectonic setting of cambro ordovician volcanic hosted massive sulfide mineralization in northeastern australia the mount windsor subprovince is an important relic of upper cambrian to lower ordovician sedimentation and volcanism in the northern part of the tasman orogenic zone volcanic hosted massive sulfide mineralization occurs at several stratigraphic horizons within the volcano sedimentary package and one major mine is operational within the belt major and trace element data and nd isotope ratios are presented for the least altered coherent units from the three major volcanic bearing formations in the mount windsor subprovince the data are used to discriminate four major phases of volcanism and related intrusive activity derived from three isotopically discrete sources and to assess the geodynamic setting in which the volcanism occurred the earliest phase of mafic volcanism has minor and trace element characteristics suggesting an alkaline intraplate or rift association and it was probably produced by partial melting of attenuated subcontinental lithospheric mantle the overlying mount windsor formation silicic volcanics have nd isotope characteristics epsilon sub nd 480 ma 4 7 to 12 8 that suggest they were produced by partial melting of underlying precambrian crustal rocks mafic volcanics of the overlying trooper creek formation include a low tio 2 suite and a high tio 2 suite with a range of distinguishing chemical characteristics but similar nd isotope ratios epsilon sub nd 480 ma 3 8 2 3 which indicate derivation from relatively depleted asthenospheric mantle variably modified by subduction processes the high tio 2 suite is also represented by abundant intrusions within the underlying volcanic package the more silicic volcanics in the trooper creek formation appear to be cogenetic with their mafic associates but have varying nd isotope ratios which suggest progressive crustal interaction with increasing sio 2 content comparisons with modern volcanic compositions and ore depositional environments suggest that the volcanic and sedimentary units within the mount windsor subprovince were deposited in a back arc basin developed by extension of continental lithosphere along the eastern australian margin in the late cambrian and early ordovician mineralization and volcanic deposits of similar age farther north in the tasman orogenic zone suggest that this basin may have had a north south orientation although there is no clear evidence remaining of the original arc front deposits

geology and volcanic facies architecture of the lower ordovician waterloo massive sufide deposit australia the waterloo massive sulfide deposit occurs in the cambro ordovician seventy mile range group in the charters towers district in northern queensland one of the principal submarine successions in eastern australia that contains abundant volcanic hosted base metal deposits the deposit consists of several small dismembered stratiform blanketlike pyrite chalcopyrite sphalerite galena massive sulfide lenses hosted by intensely altered volcanic rocks the deposit and its host rocks have been deformed during regional deformation of the middle to late ordovcian and were affected by two subsequent events of brittle deformation the waterloo deposit formed on top of a lava dominated andesite succession comprising coherent volcanic units and related juvenile volcaniclastic rocks the hydrothermal activity leading to the deposition of massive sulfides commenced during the waning stages or after the cessation of the andesite volcanism the blanketlike mineralization is interpreted to have formed largely at or very close to the sea floor in a moderately deep to deep marine environment formation of the massive sulfides was accompanied by the mass flow deposition of coarse quartz feldspar crystal rich volcanic debris that records broadly contemporaneous probably explosive rhyolitic volcanism occurring outside the immediate study area this resedimented volcaniclastic unit retains a record of hanging wall alteration indicating that the waterloo hydrothermal system was operative during and after burial by the coarse volcaniclastic material the deposition of the coarse volcaniclastic rocks was followed by the intrusion of a feldspar porphyritic dacite cryptodome that was also subject to hydrothermal alteration associated with the massive sulfide formation facies relationships suggest that the cryptodome locally breached the wet and unconsolidated coarse volcaniclastic material to emerge on the sea floor the emplacement of the partially extrusive dacite cryptodome coincided with the waning of the waterloo hydrothermal system the subsequent period of relatively quiet sedimentation was occasionally interrupted by the emplacement of synsedimentary basalt and andesite sills as volcanism at waterloo shifted back to more mafic compositions this period was followed by the mass flow deposition of coarse feldspar quartz vitric volcanic debris and the onset of another period of intense basalt to andesite dominated volcanism geochemical analyses of volcanic rocks from the host rock succession of the waterloo deposit and correlation with regional data suggest that the massive sulfide deposits in the charters towers district formed during a specific period of cambro ordovician back arc basin development dominated by mantle derived volcanism comparison with the volcanic architecture of other known massive sulfide deposits in the district indicates that massive sulfide mineralization at charters towers is mainly associated with silicic shallow intrusion dominated volcanic centers and occurrences of this volcanic facies should be considered prospective for other deposits in the belt

observation and analysis of a large amplitude mountain wave event over the antarctic peninsula 1 we use measurements from the atmospheric infrared sounder airs on the aqua satellite to observe the 3 dimensional structure of a gravity wave event over the antarctic peninsula and determine the horizontal and vertical wavelengths propagation direction and temperature amplitude and from these we estimate wave momentum flux using theoretical knowledge of the weighting functions and radiative transfer for airs radiance measurements at temperature sensitive channels in the infrared we derive a method of estimating wave temperature amplitude directly from the radiance measurements comparison of the radiance based temperature amplitudes to the temperature amplitude in airs retrieved temperature fields shows close agreement because the radiances have 3 times better horizontal resolution than the retrievals our analysis suggests we can routinely observe important geophysical properties of waves with horizontal wavelengths as short as 80 km using airs radiances we further analyze a nearly identical wave event appearing in the european centre for medium range forecasts ecmwf temperature and wind fields from both assimilation and forecast data analysis of the ecmwf data and nearby radiosonde wind profiles allows the interpretation as a mountain wave event forced by flow over the topography of the antarctic peninsula

gravity wave variations during the 2009 stratospheric sudden warming as revealed by ecmwf t799 and observations 1 ecmwf t799 is used to study gravity wave gw variations during the 2009 stratospheric sudden warming ssw in the arctic the magnitude and occurrence of gws correlate with the location and strength of the polar vortex that is strongly disturbed by planetary wave pw growth this location dependence on pw phase explains the observed gw variability during ssws during the development and the onset of ssw the zonal mean gw potential energy density gw ep increases on january 5 and 15 22 in association with the growth of pw wavenumber 1 and wavenumber 2 respectively as the initial prominent pw magnitude in the lower mesosphere progresses downward gw ep enhancement also seems to show a corresponding descent from january 5 22 gw ep peaks before the wind reversal occurrence and significantly weakens after the ssw these variations are confirmed by cosmic gps observations lidar data from antarctica are also used to validate gws as derived in ecmwf

volcanism sedimentation and massive sulfide mineralization in a late cretaceous arc related basin eastern taurides turkey abstract late cretaceous arc volcanism and associated massive sulfide mineralizations occur in the eastern taurus mountains the mineralizations are related to felsic dacitic rhyolitic volcanic rocks which together with basement rocks form the lowermost levels of a 5000 m thick volcano sedimentary sequence and are restricted to a few levels within the sequence basaltic rocks which are intruded by tonalite and dacite form the base of the volcano sedimentary sequence the dacitic rhyolitic rocks are overlain by a volcano sedimentary succession with andesitic dacitic flows the flows do not contain any mineralization this succession starts with volcanic breccia and tuffs at the base passing into crystal rich sandstone and pelagic mudstone with tuffite intercalations and ends with marls intercalated with sandstones basalt and peridotite olistoliths the felsic rocks bear stockwork and disseminated types of mineralization the massive sulfide mineralization has a simple mineral assemblage of pyrite chalcopyrite bornite and sphalerite optical microscopic examination of pyrites from derince massive sulfide deposits reveals that the pyrites are commonly seen in framboidal and cubic forms the geochemistry of the magmatic rocks and sedimentary facies associations indicate that the mineralizations in the derince were developed in an intra arc environment

magmatic evolution and tectonic setting of the iberian pyrite belt volcanism rocks has been carried out to determine the primary magmatic aynity tectonics iberian pyrite belt and tectonic setting of the iberian pyrite belt volcanism most of the basaltic rocks are continental tholeiites but a few samples show an alkaline aynity the origin of the basaltic rocks and their diversity of compositions are explained by a single mixing model between e and n morb mid ocean ridge basalt and as introduction similation of crustal material calc alkaline intermediate and silicic volcanic hosted massive sulphide deposits are mainly rocks include basaltic andesites andesites dacites and rhyolites associated world wide with calc alkaline submarine volvolumetrically dacites and rhyolites are the most abundant inter canism petrological and geochemical data together with mediate and silicic rocks are not related by fractional crystallization stratigraphic and structural studies have been of major nor is there a relationship between the basaltic and calc alkaline importance in constraining geological models of the volrocks by the same process we suggest that in the iberian pyrite canism associated with massive sulphide deposits inbelt silicic calc alkaline magmas were generated on a large scale tegrated studies in areas such as the kuroko province in by the invasion of continental crust by mafic magmas generated in japan ohmoto 1983 the mount read volcanics in the underlying upper mantle the diversity of compositions shown tasmania crawford et al 1992 and the mount windsor by dacites and rhyolites can mainly be explained either by diverences volcanics in northwestern australia stolz 1995 have in the composition of the source rocks or by diverent degrees of revealed that this volcanism may be developed during partial melting of upper crust rocks andesites however formed by diverent stages of the subduction process always being mixing between basaltic magmas and upper crust material the new located on the overriding plate geochemical data agree with previously published tectonostratigraphic this paper documents the petrology and geochemistry data which suggest that the iberian pyrite belt volcanism formed of the volcanism of the iberian pyrite belt an early on the south portuguese plate owing to strike slip tectonics this carboniferous metallogenic province that extends from portugal to spain in southwest iberia and constitutes local extensional tectonic setting was related to transtension as a

textural and chemical characteristics of diagenetic and hydrothermal alteration in glassy volcanic rocks examples from the mount read volcanics tasmania the mount black and sterling valley volcanics comprise a complex cambrian succession of originally glassy felsic to mafic submarine volcanic facies in western tasmania the mount black and sterling valley volcanics have been modified by the combined effects of diagenesis hydrothermal alteration and regional metamorphism metamorphosed diagenetic and hydrothermal alteration facies have been distinguished using a combination of alteration mineralogy overprinting relationships texture distribution intensity and whole rock geochemistry alteration facies that are interpreted to be the regionally metamorphosed equivalents of diagenetic clays and zeolites are regionally extensive and overprinted by the regional cleavage although widespread their distribution is patchy and their intensities are highly variable reflecting the complexity of the original textures in glassy volcanic rocks thin films of sericite carbonate and chlorite sericite hematite replace clays that coated original glassy surfaces at the onset of diagenesis prior to compaction feldspar quartz sericite chlorite sericite and chlorite sericite hematite alteration facies replace zeolites and clays that filled pore space and altered glass prior to and synchronous with compaction the final diagenetic alteration facies chlorite epidote began after compaction and continued during metamorphism diagenetic alteration involved significant mineralogical and textural changes but only minor changes in chemistry the chemical changes associated with diagenetic alteration facies are consistent with the interaction of rhyolitic and basaltic glass with seawater during burial alteration facies that are interpreted to be hydrothermal are local in distribution crosscut stratigraphic boundaries and involve significant changes in texture mineralogy and composition early hydrothermal alteration facies quartz sericite and calcite quartz hematite predated compaction and were synchronous with diagenesis chlorite calcite magnetite and chlorite pyrite alteration facies were synchronous with regional deformation and are associated with tectonic breccias faults and shear zones chlorite quartz calcite alteration facies postdated regional deformation