residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

boninitic magmatism in a continental margin setting yukon tanana terrane southeastern yukon canada mid paleozoic mafic rocks in the finlayson lake region of the yukon tanana terrane southeastern yukon canada have the diagnostic geochemical signatures of boninites high mgo cr ni and co contents intermediate sio 2 contents high mg 9s mgo mgo feo al 2 o 3 tio 2 and zr hf middle rare earth element ree ratios low tio 2 ree and high field strength element contents and u shaped primitive mantle normalized trace element patterns however unlike most modern and ancient boninitic rocks that are typically associated with intraoceanic realms those from the finlayson lake region are part of a mid paleozoic continental margin arc backarc magmatic system we propose a model in which the boninitic rocks from the finlayson lake region formed as a result of spreading ridge propagation into an arc built on composite basement of oceanic and continental crust in the oceanic segment upwelling asthenosphere induced melting of a subducted slab metasomatized refractory mantle source to form boninitic magmatism in the continental sector upwelling asthenospheric mantle and or the melts derived thereof induced crustal melting which explains the large volume of temporally equivalent felsic volcanic and intrusive rocks

evaluation of the role of cambrian granites in the genesis of world class vhms deposits in tasmania abstract an analysis of the distribution composition and alteration zonation of cambrian granites which intrude the mt read volcanics of western tasmania provides evidence that there may have been a direct input of magmatic fluids containing fe cu au and p to form the copper gold volcanic hosted massive sulphide vhms mineralisation in the mt lyell district interpretation of regional gravity and magnetic data indicates that a narrow discontinuous body of cambrian granite 2 4 km wide extends along the eastern margin of the mt read volcanic belt for over 60 km the cambrian granites are altered magnetite series types which show enrichment in barium and potassium and contrast markedly with the fractionated ilmenite series devonian granites related to tin mineralisation elsewhere in the dundas trough copper mineralisation occurs in a linear zone above the apex of the buried cambrian granite body at the southern end of the belt from mt darwin to the mt lyell district over a strike length of 25 km gold and zinc mineralisation are concentrated higher in the volcanic stratigraphy more distant from the granite overlapping zones of alteration extend from the granite into the surrounding volcanic rocks an inner zone of k feldspar alteration is overprinted by chlorite alteration which passes outwards into sericite alteration magnetite pyrite chalcopyrite apatite mineralisation is concentrated in the chlorite alteration zone as veins and low grade disseminations the mt lyell copper gold stringer and disseminated mineralisation is hosted in felsic volcanic rocks 1 to 2 km west of the interpreted buried granite position magnetite apatite pyrite veins in the prince lyell deposit at mt lyell are very similar to the veins in the halo of the granite further south and provide evidence for magmatic fluid input during the formation of the copper gold vhms deposits a model involving deeply penetrating convective seawater mixing with a magmatic fluid released from the cambrian granites best explains the features of vhms mineralisation in the mt lyell district

development of late paleozoic volcanic arcs in the canadian cordillera an example from the klinkit group northern british columbia and southern yukon the late paleozoic volcanic rocks of the northern canadian cordillera lying between ancestral north america to the east and the accreted terranes of the omineca belt to the west record early arc and rift magmatism along the paleo pacific margin of the north american craton the mississippian to permian volcano sedimentary klinkit group extends discontinuously over 250 km in northern british columbia and southern yukon the two stratotype areas are as follows 1 in the englishman range southern yukon the english creek limestone is conformably overlain by the volcano sedimentary mount mccleary formation lower clastic member alkali basalt member and volcaniclastic member and 2 in the stikine ranges northern british columbia the screw creek limestone is conformably overlain by the volcano sedimentary butsih formation volcaniclastic member and upper clastic member the calc alkali nature of the basaltic volcaniclastic members of the klinkit group indicates a volcanic arc setting la yb n 2 77

petrology geochemistry and oxygen isotope interpretation of felsic volcanic and related rocks hosting the brunswick 6 and 12 massive sulfide deposits brunswick belt bathurst mining camp new brunswick canada the large brunswick massive sulfide deposits brunswick 6 and 12 and austin brook are hosted in the lower part of the middle ordovician bimodal volcano sedimentary tetagouche group along the autochthonous eastern margin of the bathurst mining camp the footwall rocks of the nepisiguit falls formation are relatively homogeneous quartz and alkali feldspar porphyritic crystal rich and matrix supported tuffs with a cryptocrystalline glassy to granular microcrystalline groundmass the fine to coarse grained crystal rich tuffs and tuffaceous sedimentary rocks are thickest 500 m beneath the deposits possibly due to a basinal accumulation of pyroclastic flow material the brunswick horizon massive sulfide deposits and associated exhalite algoma type iron formation formed after a period of felsic pyroclastic volcanism nepisiguit falls formation and before the onset of the overlying thick succession of intercalated rhyolite flows tuffs tuffites and hyalotuffs flat landing brook formation the footwall and hanging wall felsic volcano sedimentary rocks are variably altered which occurred mainly during the syngenetic mineralizing event rocks with minimal evidence of alteration and or tectonic fabric development however allow some interpretation of the major element variations in the least altered suite the sio 2 contents range from 68 to 72 wt percent with intermediate alkali element contents and low fe and mg contents typical of calc alkaline rhyolites weak regional silicification is irregularly distributed in the upper parts of the nepisiguit falls rocks but also in the flat landing brook rocks however there is considerable mobility of na k fe and mg as well as numerous other minor and trace elements as a result of albitization sericitization chloritization and carbonatization reactions associated with vent related and local seawater related alteration processes as observed in earlier alteration studies in the camp there is an antipathetic relationship between sericite and chlorite with chlorite predominant near the deposits

geochemical and isotopic nd o data from ordovician felsic plutonic and volcanic rocks of the miramichi highlands petrogenetic and metallogenic implications for the bathurst mining camp middle ordovician felsic magmatism contemporaneous with bathurst camp pb zn volcanogenic massive sulphide vms deposits consists of strongly altered volcanic to subvolcanic rocks belonging to the tetagouche group and relativelyunaltered granitoid plutons which are divided into northern central and southern groups within the miramichi highlands calc alkalic felsic volcanic rocks and northern plus central plutons have epsilonnd t values ranging from 8 2 to 1 9 and 4 0 to 0 3 respectively they exhibit within plate type volcanic and transitional i to a type granite geochemical characteristics granitoid rock delta18o values range from 8 0 to 10 1 published granitoid rock pb isotopic compositions overlapunpublished galena data from bathurst vms deposits field geochemical and isotopic evidence indicate that these volcanicand granitoids rocks are consanguineous and mainly derived from proterozoic orolder infracrustal sources alkalic felsic volcanic rocks and associated alkaline basaltic rock

the sylvester allochthon upper paleozoic marginal basin and island arc terranes in northern british columbia the sylvester allochthon is a composite klippe of upper paleozoic ophiolitic island arc and pericratonic assemblages which rests directly on the cassiar terrane a displaced sliver of ancestral north america each tectonic assemblage occurs at a distinct and consistent structural level within the allochthon they are assigned respectively to the slide mountain harper ranch and yukon tanana terranes the sylvester allochthon provides a view of the structural relationships between these terranes prior to early cretaceous early tertiary strike slip dismemberment as well as possible sedimentological links to late paleozoic north america slide mountain terrane assemblages designated divisions i and ii form the lowest structural panels chert quartz sandstones are interbedded with lower mississippian deep water sediments in division i and ocean floor basalts and deep water sediments in division ii they are similar in age and character to sandstones in the autochthonous earn group division ii as

wave theoretical inversion of teleseismic surface waves in a regional network phase velocity maps and a three dimensional upper mantle shear wave velocity model for southern germany summary using teleseimic surface wave data from 110 selected earthquakes recorded at 10broad band stations in southern germany we construct phase velocity maps of rayleigh waves for southern germany in a further step these maps are inverted for a three dimensional model of the sv velocity of the upper 200 km of the mantle we attempt to take into account the effect of heterogeneous structure outside the study region by jointly inverting the data for heterogeneous phase velocity inside the study region and the distortion of the incoming wavefields by the surrounding structure the total wavefield in the study region is computed with a scattering formalism which includes multiple forward scattering and single backscattering since in principle the data can be perfectly fit by the incoming wavefields without any heterogeneous structure inside the study area we impose additional constraints on the incoming wavefields to reduce the non uniqueness the most important constraint is an energy criterion which states that the energy of the modelled wavefield in the study area averaged over many events should be equal to the energy sampled by the stations we demonstrate that enforcing this criterion generates phase velocity maps with heterogeneous structure nevertheless we are able to satisfy the energy criterion without any heterogeneous structure at the price of an only slightly increased data misfit hence it must be concluded that a seismic network of size and station density such as the one used in this study is still insufficient to demonstrate convincingly the existence of heterogeneities in the network area using teleseismic surface waves any reasonable structure combined with the appropriate incoming wavefields would allow an acceptable fit of our data this frustrating conclusion of course applies to all other comparable studies which use teleseismic surface waves although we cannot convincingly show that any phase velocity map we find should be preferred over others we are able to obtain good reconstructions of test structures from realistic synthetic data with the same station and event distribution as the real data moreover we find that the geometric pattern of the phase velocity maps obtained from real data depends only weakly on the constraints applied in the inversion while the amplitude of the phase velocity perturbations is almost completely determined by the constraints for all periods considered the fit to the data is extremely good the reduction of the quadratic misfit relative to the case of plane incoming waves and no structure is dramatic for the shorter periods the 3 d model of vertical shear wave velocity down to a depth of 200 km exhibits a basic division into four quadrants separated by a vertical plane intersecting the surface along a nearly west east line and a horizontal plane at about 130 km depth the northern rants show high velocities in the top 120 km and low velocities below 140 km the opposite is the case for the southern quadrants an exception to this general feature is a pronounced low velocity zone in the northwestern corner of the region

tectonic affinity of nisutlin and anvil assemblage strata from the teslin tectonic zone northern canadian cordillera constraints from neodymium isotope and geochemical evidence we present geochemical and isotopic data for nisutlin assemblage metasedimentary rocks and anvil assemblage greenstones from the teslin tectonic zone of the northern canadian cordillera this study aims to establish the tectonic setting of formation for the sedimentary and basaltic protoliths of these highly deformed and metamorphosed rocks and thereby place constraints on the origin of these enigmatic rocks for which differing tectonic models have been proposed for the nisutlin assemblage metasedimentary rocks the geochemical and isotopic data show that two widely different source regions contributed detritus to the original sediments one source region was felsic upper crustal material with nd isotopic compositions compatible with ultimate derivation from the north american continent depleted mantle model age tdm 2 5 2 8 ga the second source region is deduced to be chemically primitive crust basaltic andesitic with a short crustal residence history 0 9 ga for the anvil assemblage greenstones immobile trace element abundances are dissimilar to within plate oceanic arc and normal mid ocean ridge basalts and similar to calc alkaline basalts in active continental margin settings we interpret the paleosetting for the nisutlin assemblage to be at the outermost margin of the ancestral north american continent in an area which received detrital input from the distal north american craton in the early paleozoic however this area also received detritus from a chemically and isotopically juvenile magmatic arc source a source type not known from paleozoic metasedimentary rocks from the miogeoclinal sequence on the basis of similar nd isotopic relationships recorded elsewhere in deformed paleozoic rocks of the orogen we infer that these geochemical signals reflect tectonic processes of regional extent the trace element geochemistry of the anvil assemblage greenstones does not support a correclation with known paleozoic greenstones of the slide mountain terrane which some tectonic models have advocated

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

mississippian assembly of the nisutlin assemblage evidence from primary contact relationships and mississippian magmatism in the teslin tectonic zone part of the yukon tanana terrane of south central yukon metamorphosed and ductilely deformed sedimentary plutonic and volcanic rocks of the nisutlin and anvil assemblages make up the yukon tanana terrane in the teslin tectonic zone study area the nisutlin assemblage consists of siliceous schist quartzite and graphitic phyllite that share a primary depositional contact and early mississippian tonalite to quartz diorite that intrudes the siliceous schist quartzite and possibly the graphitic phyllite the anvil assemblage includes metagabbro and mafic schist greenstone that share an intrusive contact relationship tonalite to quartz diorite of the nisutlin assemblage is characterized by minor zircon inheritance with an average proterozoic age end 350 ma values of 2 5 to 6 2 and nd model ages of 1 50 1 79 ga these data suggest that the magmatic bodies have inherited a component of continentally derived material primary contact relationships and age data indicate that the nisutlin assemblage had formed by mississippian time and regional correlations sho

sm nd studies of archaean metasediments and metavolcanics from west greenland and their implications for the earth s early history metasedimentary and metavolcanic rocks from the archaean of west greenland have been examined for evidence of crustal components greater than 3 8 ga in age and for their compatibility with the presently adopted bulk earth sm nd parameters sm nd isotopic data have been obtained for the garbenschiefer metagabbro unit metasediments from the isua supracrustal belt gneisses interior to the isua belt and metasediments from the malene supracrustal belt using estimates of emplacement age t of between 3 77 and 3 67 ga for the parental volcanics to the garbenschiefer unit initial143nd 144nd ratios yield positiveendt values between 1 0 and 3 1 relative to the chur parameters for seven out of eight samples model sm nd ages for the isua gneisses and metasediments are only compatible with their estimated stratigraphic ages if their sources were ca 2end relative to chur at those times similarly model sm nd ages for the malene samples are only compatible with stratigraphic age constraints when based on a source evolution with positiveendt implications of these results for the early development of the earth s mantle are discussed

a gis based study of earthquake hazard as a tool for the microzonation of bucharest abstract bucharest the capital of romania is situated close to one of the most seismically active areas in europe the vrancea region in the eastern carpathians the necessity of a well documented microzonation of the city and its immediate surroundings is clearly evident due to this seismic risk in the absence of a sufficient dense network of ground motion recording stations in bucharest the only possible way to realise a comprehensive microzonation is to correlate detailed subsurface geological data at instrumented sites with the macroseismic intensities and to extrapolate the results to non instrumented areas in this regards the geology of bucharest is relatively well known based on a great number of geotechnical drillings about 1200 for the first time a digital geological model dgm of the subsurface of bucharest was obtained based on the integration of numerous borehole data with a geographic information system gis transfer functions and dynamic ground responses were calculated with the linear modelling software proshake using soil profiles taken from discrete locations in the developed model and shear wave velocities and densities characteristic for each quaternary unit the distribution of computed spectral amplifications and spectral accelerations were generated for the ground surface of bucharest by interpolation important insights were made concerning the primary geological influencing factors on the observed historical damages to buildings which resulted from earthquakes through statistical regression analyses between various geotechnical properties and parameters associated with the historical damages

the shear wave velocity underneath bucharest city romania from the analysis of love waves summary from the dispersion of love waves we infer models of shear wave velocity structure underneath bucharest romania at depths down to 2 km that can contribute to seismic hazard estimation waves from eight regional events recorded during 10 months with a network of 34 seismic broad band stations of the urban seismology urs experiment are used although these events provide poor azimuthal coverage the data reliably constrain a shear wave velocity model with an interface between the neogene and the cretaceous sediments that is dipping northwards towards the carpathian mountains array processing techniques that account for non uniform wave propagation are used to estimate the dispersion of structural phase velocity from this we infer subsurface structure at three different latitudes the neogene sediments are represented by a gradient layer with no significant lateral variation shear wave velocity increases from approximately 400 m s 1 near the surface to 1 km s 1 at 1 km depth and 5 km in the south and to 1 35 km s 1 at 1 5 km depth and 5 km in the north from the centre of bucharest respectively for the half space representing the cretaceous sediments we obtain shear wave velocities of 2 7 2 9 km s 1 the results are consistent with results from boreholes and shallow seismics for the near surface structure and results from receiver function studies and crustal refraction seismic studies for the deeper structure the details of the neogene layer comprising a vertical gradient fill a gap in existing models of the subsurface structure of bucharest and can contribute to modelling of seismic hazard for the city since the signalto noise ratio restricted useful data to the frequency range from 90 to 290 mhz the inversion could not constrain the near surface velocity independently due to strong trade off between near surface velocity and depth of half space the latter had to be introduced as ap rioridata from previous studies

trace element geochemistry of ore associated and barren felsic metavolcanic rocks in the superior province canada reply archaean felsic metavolcanic rocks in the superior province of the canadian shield may be divided into three major groups on the basis of trace element abundances and ratios 1 fi felsic metavolcanic rocks are dacites and rhyodacites characterized by steep ree patterns with weakly negative to moderately positive eu anomalies high zr y low abundances of high field strength elements e g hree y zr hf and high abundances of sr examples occur in the bowman subgroup and skead group in the abitibi belt in the kakagi lake lake of the woods shoal lake and sturgeon lake areas of the wabigoon belt and in the confederation lake area of the uchi belt none of these horizons as known hosts base metal sulphide deposits 2 fii felsic metavolcanic rocks are rhyodacites and rhyolites characterized by gently sloping ree patterns with variable eu anomalies moderate zr y and intermediate abundances of hfs elements and sr examples occur in the misema subgroup of the abitibi belt in the wabigoon lake a

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

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

lead isotope geochemistry of shales from the wolverine volcanogenic massive sulfide deposit yukon implications for pb isotope vectoring in exhalative ore systems combined whole rock lead isotope and high precision trace element data are reported for shales from the wolverine deposit and surrounding prospects e g puck fisher sable to elucidate the source of pb in the shales and their potential utility as an exploration vector shales exhibit distinct variations in time integrated u th pb evolution with proximity to mineralization distal samples resemble the local crustal pb isotope composition of the northern cordilleran continental crust i e shale curve more proximal samples exhibit evidence for hydrothermal activity but were not significantly mineralized they have very high u th and u pb and anomalous present day 206 pb 204pb 20 coincident with elevated y ho zr hf and carbonate alteration these signatures were derived from oxygenated seawater and imprinted on the shales by oxygenated co2 rich hydrothermal fluids that contained uranyl carbonate ions e g uo2 co3 3 4 it is envisioned that this was due to shallow level within 50 m of the seafloor near vent ingress of oxygenated seawater associated with hydrothermal venting a third population of samples is most proximal to mineralization these too have trace element signatures i e high y ho zr hf co2 u enrichment inherited from seawater but they do not exhibit anomalous present day 206pb 204 pb being more juvenile in 206 pb 204 pb 207 pb 204 pb and 208pb 204pb this isotope composition coincides with enrichments in pb zn cu tl sb w and sn cu mo the pb enrichment associated with mineralization effectively buffered these samples from appreciable pb isotope evolution despite overprinting by uranyl carbonate the juvenile pb associated with the shales proximal to mineralization argues for deep penetrative circulation of hydrothermal fluids and leaching of pb from mafic igneous rocks at depth and or influence from juvenile magmas at depth i e magmatic fluids both of these processes were likely critical for the genesis of mineralization at wolverine this study illustrates the utility of quadrupole inductively coupled plasma mass spectrometry icp ms for providing sufficiently precise and accurate pb isotope determinations for district scale metallogenic evaluations furthermore the coupling of solution icp ms pb isotopes with high precision trace element geochemistry from the same digest provides a powerful tool for regional exploration studies for hydrothermal mineralization in shale basins

geological setting and tectonic significance of mississippian felsic metavolcanic rocks in the pelly mountains southeastern yukon territory the central pelly mountains in southeastern yukon territory consist of imbricate thrust sheets which have undergone syn and post thrusting deformation and metamorphism the local geology is further complicated by the intrusion of late cretaceous batholiths and by strike slip faulting related to the tintina fault a major northwest trending transcurrent fault of latest cretaceous or early tertiary age this faulting disrupts the northeast edge of the study area upper devonian and mississippian strata are present in at least two of the structural packages but the mississippian metavolcanic rocks occur only in the lowermost package rb sr geochronology indicates a mid mississippian age for the igneous suite the volcanic rocks consist of volcaniclastic material with minor interbedded flows and were deposited in a submarine environment several coeval and cogenetic syenite and trachyte domes and small stocks are the remains of vent areas although the volcanic rocks are all highly altered and show eviden

urban shakemap methodology for bucharest 1 we develop a methodology for a shakemap for the romanian capital bucharest that can be rapidly computed and delivered to the public once real time data access is available to a sufficient extent the methodology with which the californian shakemaps are generated cannot be transferred to bucharest due to a missing understanding of the relationship between the geological near surface structure and the ground motion amplification however a systematic incorporation of previous seismological observations using fourier amplitude spectra of weak and strong ground motion and a recent urban broadband experiment in bucharest allows us to interpolate computed seismic intensities from 11 sites where accelerometers measure the actual motion of a specific earthquake to 31 additional locations in the city so that a reasonably reliable distribution of ground motion in the city can be determined we demonstrate this methodology using the mw 6 0 intermediate depth earthquake of october 27 2004

antler elastics in the canadian cordillera during late devonian through mid mississippian time thick sequences of elastics flooded the canadian cordilleran miogeocline chert conglomerate chert quartz sandstone and pebbly mudstone of the westerly derived earn sequence formed local massive channel deposits up to 200 m thick on submarine fans and in narrow grabens within a broad region of shale deposition extension and local contraction of the miogeocline during rifting or strike slip outboard of present preserved limits can explain 1 the derivation of earn elastics from older miogeoclinal units 2 local alkaline volcanism 3 exhalite mineralization and 4 tremendous thickness variations related to steep syndepositional faults

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

vrancea99 the crustal structure beneath the southeastern carpathians and the moesian platform from a seismic refraction profile in romania the vrancea99 seismic refraction experiment is part of an international and multidisciplinary project to study the intermediate depth earthquakes of the eastern carpathians in romania as part of the seismic experiment a 300 km long refraction profile was recorded between the cities of bacau and bucharest traversing the vrancea epicentral region in nne ssw direction the results deduced using forward and inverse ray trace modelling indicate a multi layered crust the sedimentary succession comprises two to four seismic layers of variable thickness and with velocities ranging from 2 0 to 5 8 km s the seismic basement coincides with a velocity step up to 5 9 km s velocities in the upper crystalline crust are 5 9 6 2 km s an intra crustal discontinuity at 18 31 km divides the crust into an upper and a lower layer velocities within the lower crust are 6 7 7 0 km s strong wide angle pmp reflections indicate the existence of a first order moho at a depth of 30 km near the southern end of the line and 41 km near the centre constraints on upper mantle seismic velocities 7 9 km s are provided by pn arrival times from two shot points only within the upper mantle a low velocity zone is interpreted travel times of a plp reflection define the bottom of this low velocity layer at a depth of 55 km the velocity beneath this interface must be at least 8 5 km s geologic interpretation of the seismic data suggests that the neogene tectonic convergence of the eastern carpathians resulted in thin skinned shortening of the sedimentary cover and in thick skinned shortening in the crystalline crust on the autochthonous cover of the moesian platform several blocks can be recognised which are characterised by different lithological compositions this could indicate a pre structuring of the platform at mesozoic and or palaeozoic times with a probable active involvement of the intramoesian and the capidava ovidiu faults especially the intramoesian fault is clearly recognisable on the refraction line no clear indications of the important trotus fault in the north of the profile could be found in the central part of the seismic line a thinned lower crust and the low velocity zone in the uppermost mantle point to the possibility of crustal delamination and partial melting in the upper mantle

crustal properties from s wave and gravity data along a seismic refraction profile in romania vrancea 99 is a seismic refraction line that was carried out in 1999 to investigate the deep structure and physical properties of the upper lithosphere of the southeastern carpathians and its foreland it runs from the city of bacau to the danube river traversing the vrancea epicentral area of strong intermediate depth seismicity and the city of bucharest interpretation of p wave arrivals led to a velocity model that displays a multi layered crust with velocities increasing with depth the range of p wave velocities in the sedimentary cover increases from n to s and a structuring of the autochthonous basement of the moesian platform is observed the crystalline crust displays thickness variations but at the same time the lateral velocity structure along the seismic line remains almost constant an intra crustal boundary separates an upper crust from the lower crust within the upper mantle a low velocity zone is detected at a depth of about 55 km the interpretation of observable s waves resulted in a velocity model that shows the same multi layered crust with s velocities increasing similarly with depth as the p waves the corresponding poisson s ratio is highly variable throughout the crust and ranges from 0 20 0 35 for the sedimentary cover to 0 22 0 25 for the crystalline crust the interpretation of the vp vs and poisson s ratio in petrological terms suggests a large variety of rocks from sand and clay to sandstone limestone and dolomite within the sedimentary cover within the crystalline crust the most probably rock types are granite granodiorite granite gneiss and or felsic amphibolite gneiss in the upper part and gneiss and or amphibolite in the lower part based on the 2 d seismic velocity model a density model is developed density values are assigned to each layer in agreement with the p wave velocity model and with values accepted for the geological units in the area after several iterations a good fit between the computed and observed bouguer anomalies was obtained along the seismic line

mid paleozoic initiation of the northern cordilleran marginal backarc basin geologic geochemical and neodymium isotope evidence from the oldest mafic magmatic rocks in the yukon tanana terrane finlayson lake district southeast yukon canada the fire lake formation of the yukon tanana terrane in the finlayson lake region yukon canada consists primarily of late devonian ca 365 360 ma mafic metavolcanic rocks and smaller volumes of mafic and ultramafic subvolcanic metamorphosed intrusions in this paper field geochemical and nd isotope attributes of these rocks are presented in an attempt to understand their tectonic setting the magmatic processes involved in their formation and their roles in cordil leran crustal growth the mafic rocks of the fire lake formation exhibit a wide diversity of geochemical signatures and are classified into seven chemically defined suites 1 back arc basin basalt 2 enriched mid oceanic ridge basalt e morb 3 oceanic island basalt oib 4 th rich oib 5 boninite 6 island arc tholeiite and 7 light rare earth element lree enriched island arc tholeiite the diversity of geochemical signatures is interpreted to represent variable mixtures of asthenospheric morb type mantle subarc mantle wedge and lithospheric oib type mantle with or without elemental contributions from the subducted slab and or continental crust these suites of rocks are also associated with fine grained basinal sedimentary facies variations in metavolcanic and metasedimentary unit thickness extensional synvolcanic faults and apparent extensional fault controlled emplacement of mafic intrusive rocks and hydrothermal volcanic hosted massive sulfide mineralization the suites also exhibit a broad spatial distribution those with arc signatures nb thmn 1 mn normalized to primitive mantle values are located primarily in the western parts of the formation and suites with nonarc signatures nb thmn 1 are located primarily within the eastern parts of the formation collectively these geologic and geochemical attributes are interpreted to stem from the transition from arc magmatism to the initiation of an extensional backarc basinal environment associated with an east dipping subduction zone the initiation of backarc basin magmatism recorded in the fire lake formation was part of a much larger late devonian backarc basinal system forming along the western edge of the margin of north america the fire lake formation is interpreted to represent 1 the commencement of yukon tanana arc rifting and separation from the north american cratonic margin and 2 the initiation of a marginal backarc basin now the slide mountain terrane inboard of the yukon tanana arc system this tectonic evolution likely occurred either as a result of slab rollback toward the west within the convergent margin responsible for yukon tanana arc activity or as a result of the propagation of the slide mountain backarc basin spreading ridges into the yukon tanana arc system this yukon tanana arc rifting episode was also broadly coincident with rifting and hydrothermal activity within rocks of the north american craton the geochemical and isotopic signatures of magmatic rocks in the fire lake formation have some features similar to intraoceanic arc rocks e g boninites island arc tholei ites and many have juvenile nd isotope signatures i e nd t 0 most have nd t 5 suggesting that the pericratonic terranes of the northern cordillera have a significant juvenile component if this is the case throughout the yukon tanana terrane then the pericratonic terranes may have contributed much more juvenile material to cordil leran crustal growth in the phanerozoic than has previously been considered

average lead isotope growth curves for shale hosted zinc lead deposits canadian cordillera average lead isotope growth curves for shale hosted zinc lead deposits have been constructed empirically for a large but well defined tectonic segment of the canadian cordillera the model defined is applicable to the dating of galena lead from shale hosted deposits in the selwyn basin and in the ogilvie richardson wernecke and mackenzie mountains in the eastern fold belt and in much of the omineca crystalline belt this area of the cordillera generally had a coherent geochemical evolution lead for deposits was extracted from sediments which had been deposited along the western margin of the north american craton and which were derived largely from upper crustal crystalline rocks that formed the western part of the canadian shield the average shale growth curves involve three stages of evolution the third most recent stage of the three stage model starts at 1 89 m y and evolves to 0 m y with mu of 12 16 and omega of 49 09 the first two stages follow the two stage model of stacey and kramers 1975 the model allows precise model age estimates with an error generally less than 0 05 m y to be made for deposits of known age this is particularly useful in property evaluation during exploration because in many cases the certainty of a syngenetic or epigenetic origin can control future philosophy about exploration and or evolution of a deposit or an area model ages in concert with stratigraphic information commonly indicate the likelihood of epigenetic or syngenetic origins

paleomagnetic aspects of plate tectonics in the carpatho pannonian region paleomagnetic data available from the carpatho pannonian region are unevenly distributed at some places observations are sporadic at others the concentration is high in the latter case it is possible to decide whether the movements indicated are related to plate microplate displacements or are of local significance the paleomagnetically best known parts of the carpatho pannonian region belong to the transdanubian central range to the cserhat matra bukk area and to the mecsek villany zone comparison among paleomagnetic data sets characterizing each of them reveals fundamental differences i e points to their independent displacements during the mesozoic and cenozoic most of the isolated observations can be tied to one of the above mentioned paleomagnetic units via coeval mostly late cretaceous cenozoic data thus further subdivision of the carpatho pannonian area at least in the cenozoic does not seem required by available paleomagnetic observations

geochemical and nd isotopic constraints for the origin of eclogite protoliths northern cordillera implications for the paleozoic tectonic evolution of the yukon tanana terrane on the basis of trace element data basaltic protoliths for paleozoic eclogites from the yukon tanana terrane ytt have diverse origins eclogites from stewart lake and the simpson range have char

age constraints on the devonian shale hosted zn pb ba deposits gataga district northeastern british columbia canada sedimentary exhalative barite and barite sulfide deposits occur in upper devonian basinal clastic sedimentary rocks of the earn group of the gataga district northern canadian cordillera the deposits formed in a stratigraphic sequence from which conodont species and assemblages range in age from the upper triangularis zone to the lower praesulcata zone of the early to late famennian a time span of no more than 7 m y at the driftpile deposit which is the best constrained example conodonts bracket at least two distinct mineralization events during the middle famennian the older event is the lower upper marginifera zone or north trench zone and east zone and the younger event is the uppermost marginifera trachytera zone or main zone the other gataga deposits although somewhat less well defined are roughly of these ages or somewhat younger one barite pyrite unit at cirque is late famennian postera and expansa zones the youngest unit so far recognized in the gataga district exhalation of metalliferous brines into the gataga basin was of relatively short duration and episodic and the sites of active venting probably migrated along extensional faults through time this data allow temporal correlation of these sedimentary exhalative deposits with other devonian mississippian mineralization events on the north american margin such as other sedimentary exhalative sulfide deposits and volcanogenic sulfide deposits located on the outermost western margin of the miogeocline the sedimentary exhalative deposits of the kechika trough formed during a brief geologic episode within a much longer lived time span of are and back arc rifting and sea floor hydrothermal mineralization

neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the yukon tanana terrane in the finlayson lake region yukon canada devonian mississippian felsic rocks from the finlayson lake region have variable geochemical and nd isotopic characteristics that provide insights into the tectonic and metallogenic evolution of the yukon tanana terrane ytt and the northern cordillera late devonian 365 360 ma calc alkaline and tholeiitic arc felsic rocks in the mafic dominated fire lake unit yield end350 4 8 and 0 1 respectively and have 1 49 1 94 ga depleted mantle model ages tdm devonian mississippian 360 356 ma felsic volcanic kudz ze kayah unit wolverine succession and intrusive rocks grass lakes suite associated with volcanogenic massive sulphide vms deposits have end350 7 8 to 9 5 with tdm 1 59 2 25 ga a granitoid sample from the early mississippian 350 345 ma simpson range plutonic suite has end350 12 9 and tdm 2 01 ga similar to previously reported values for this suite the vms associated grass lakes suite of granitoids has higher high field strength element hfse and rare earth element ree contents and higher zr sc zr tio2 nb la and zr la values relative to the simpson range plutonic suite these geochemical features are similar to coeval vms associated felsic volcanic rocks in the kudz ze kayah unit the identification of similar hfse ree enriched felsic volcanic and subvolcanic intrusive rocks may aid in delineating prospective regions for vms mineralization in the ytt and other continental margin arc to back arc environments the geochemical and nd isotopic data for these ytt felsic rocks suggest that they reflect episodic mid paleozoic arc fire lake unit simpson range plutonic suite and back arc magmatism kudz ze kudz unit wolverine succession built upon a transitional basement with variable but significant influence from evolved proterozoic crustal materials

synvolcanic and younger plutonic rocks from the blake river group implications for regional metallogenesis the blake river group of the abitibi greenstone belt is host to the well known volcanogenic massive sulfide vms deposits of the noranda camp quebec canada in the noranda camp massive sulfide deposits are spatially associated with the coeval flavrian powell intrusive complex which is interpreted to have driven hydrothermal circulation that formed the deposits in the camp in the western blake river group in ontario there are also abundant intrusive rocks yet relatively insignificant accumulations of vms deposits these intrusive rocks are younger 2686 9 1 2 and 2688 5 2 3 ma and are associated with porphyry style cu mo au mineralization with re os molybdenite ages of 2682 4 5 ma the intrusions are also smaller in areal extent and do not have a temporally extended polyphase history like the flavrian powell intrusive complex the intrusions of the western blake river group can also be distinguished by lithogeochemical attributes and a distinct petrological history compared to the flavrian powell intrusive complex they have lower total y yb th hfse and ree with higher zr y la yb sm yb al2o3 yb and la smucn ratios and lower zr nb zr th zr la zr tio2 and nb thucn ratios petrologic modeling is consistent with the western blake river group intrusive rocks being generated as relatively low temperature melts 40 km in the crust where garnet is stable in the residue e g garnet amphibolite residue in contrast modeling of the flavrian powell intrusive complex is consistent with melting at shallower levels in the crust e g 800o to 850oc the occurrence of high temperature magmatism at high levels within this crust that is coeval with volcanic activity explains the occurrence of numerous vms deposits with the flavrian powell intrusive complex as this intrusive complex would have generated abundant heat at high levels in the crust to drive hydrothermal circulation in contrast the intrusions of the western blake river group were generated at depth and at lower temperature increasing the probability of heat loss upon emplacement from depth hence decreasing the probability of hydrothermal circulation at high levels in the crust and likely explaining the paucity of vms mineralization associated with these intrusive rocks the petrological attributes of the flavrian powell intrusive complex and western blake river group may be useful in delineating potentially fertile versus less prospective intrusive complexes in greenfields exploration areas notably the western blake river group intrusions have geochemical features similar to some phanerozoic porphyry cu mo au associated intrusive systems consistent with the observed mineralization and highlighting the potential of porphyry cu mo au systems of late archean age elsewhere in the abitibi

surface wave dispersion and upper mantle structure beneath southern germany from joint inversion of network recorded teleseismic events we have determined the dispersion of fundamental mode rayleigh waves in southern germany in the frequency range 4 50 mhz by simultaneously inverting data from 66 teleseismic events recorded at a network of up to 9 broadband stations three different inversion experiments were performed determination of 1 isotropic phase velocity of 2 azimuthally anisotropic phase velocity assuming a plane wave traveling across the network and 3 isotropic phase velocity but now allowing for non plane properties of the wavefield in experiments 1 and 2 for each event amplitude phase and deviation from the great circle azimuth were estimated as well we have obtained remarkably stable results for phase velocity over the whole frequency range between 7 and 25 mhz azimuthal anisotropy is definitely below 0 5 percent below 7 and above 25 mhz we found up to 3 percent anisotropy but with negligible variance reduction compared to the isotropic inversion experiment 1 admitting non plane wavefields in the inversion still yields nearly identical phase velocities on inversion of the phase velocity curve in terms of shear wave velocity we obtained a rather shallow asthenosphere with minimum s of 4 28 km s at about 130 km depth covered by a thin lid with s of 4 63 km s