intraplate extension prior to continental extrusion along the ailao shan red river shear zone left lateral movement of the ailao shan red river shear zone lends support to the hypothesis of continental extrusion resulting from the collision of india with asia our new observations from northwestern yunnan china and northwestern vietnam on different sides of the shear zone demonstrate that the sinistral offset was 600 km according to correlations of permian triassic flood basalt successions and late paleogene highly potassic mafic magmas we conclude that the shear was propagating on the south china continental margin and does not correspond to a suture between south china and indochina furthermore the highly potassic magmas were emplaced from ca 40 to 30 ma before the shear movement which was caused by the late oligocene to early miocene ca 27 22 ma extrusion activity this suggests that a late eocene to early oligocene intraplate extension possibly induced by delamination of thickened continental lithosphere took place in northwestern yunnan or eastern tibet as a response to the india asia collision this extension and sea floor spreading of the south china sea that began ca 30 ma could have accounted for the initiation of the ailao shan red river shear zone

the western ailaoshan volcanic belts and their se asia connection a new tectonic model for the eastern indochina block the western ailaoshan wal volcanic belts mark the western boundary of the south china indochina suture zone along the ailaoshan fold belt geochronological and geochemical evidence suggests that the wal volcanic belts vary in ages and origins and includes 1 l carboniferous earliest m permian ca 300 270 ma incipient backarc basin magmatism 2 m permian ca 265 ma island arc mature backarc basin magmatism 3 early l permian ca 260 255 ma wal indochina arc continent collision and the associated syn collisional granitic magmatism as well as subsequent 4 e triassic ca 250 245 ma post collisional magmatism regional geological comparison indicates that the post l carboniferous wal tectonic evolution was closely related to the eastern indochina block we present a new g plate geodynamic evolution model for the ailaoshan fold belt and its surrounding south china indochina region based on new and published u pb zircon ages together with whole rock and pb isotope geochemical data

textural control on gold distribution in as free pyrite from the dongping huangtuliang and hougou gold deposits north china craton hebei province china article i nfo pyrite from the dongping huangtuliang and hougou gold deposits hebei province china was investigated using a combination of ore microscopy including back scattered imaging and in situ laser ablation inductively coupled plasma mass spectroscopy la icp ms a range of elements including au te ag pb bi cu co ni and as was analyzed with the aim to constrain the textural controls and influence of superimposed deformation on the distribution of invisible gold in as free pyrite thedatasetshowsexcellentcorrespondence betweenmeasuredhighgoldvaluesandthreekeytexturalcriteria i areasofclusteredtellurideinclusions especiallyindongping ii microshearingandfracturing brecciation dongping and huangtuliang and iii pyrite recrystallization huangtuliang invisible gold is only at trace levels in the hougou and gold bearing telluride minerals are not observed this is considered to result from larger scale remobilization of gold during advanced brecciation and recrystallization of pyrite pyrite grains containing clustered inclusions have by far the highest gold concentrations up to 1 wt with consistent values of thousands of ppm au interpretation of textures and la icp ms data infers that in these areas the distribution of telluride inclusions extends pervasively from micron to nanoscale i e as fields of nanoparticles local employment of coupled dissolution reprecipitation reaction between pyrite and fluids driving the k metasomatic alteration dated at 150 ma is invoked to explain such patterns syn deformational grain scale mobilization of gold and other elements took place leading to a portion of the gold being recrystallized within fractures and microshears the deformational event leads to gold enrichment in the huangtuliang pyrite where brittle fracturing brecciation has been followed by a resorption and recrystallization in the latter case foam textured pyrites again without as can contain up to hundreds of ppm gold theinterpreted sequenceof pyritepost depositional eventsis inaccordancewith the protracted magmaticevolution of the area starting with variscan alkaline intrusions 390 ma and reactivated during the yanshanian orogeny 150 ma thestudyshows i thatas freepyritecanreadilycontainsignificantamountsofinvisiblegold bothasnanoparticles

late permian triassic magmatic evolution in the jinshajiang orogenic belt sw china and implications for orogenic processes following closure of the paleo tethys growth of continental crust involves the complex interplay of subduction zone magmatism to generate the crust followed by stabilization through crustal thickening magmatism and ultimately isolation from the active plate margin the jinshajiang orogenic belt sw china provides an exceptional record of continental development as the result of closure of the paleo tethys seaway and ensuing collision a compilation of u pb age and geochemical data for the plutonic and volcanic rocks within the southern part of the jinshajiang orogenic belt including new high precision ages for the ludian granitoid batholith of 231 to 220 ma enables us to explore the interaction between magmatism and orogeny in the context of the paleo tethys closure and continental amalgamation these age and geochemical constraints in conjunction with other geologic evidence suggest that subduction of the paleo tethys ocean dominated local tectonics prior to the triassic creating a volcano plutonic arc along the eastern margin of the qamdo simao terrane following consumption of the ocean collision zone magmatism dated at 247 to 237 ma was manifested by eruption of voluminous volcanic rocks in a suture parallel zone crustal anatexis was contemporaneous with the earliest phases of collision producing high silica rhyolites of early triassic age ca 247 246 ma between 245 and 237 ma the local tectonic regime switched from compression to extension probably due to strain partitioning caused by oblique convergence which led to the development of rift basins and extensive syn tectonic bimodal volcanism associated with deep water sediments from 234 ma to 214 ma the emplacement of high k calc alkaline granodiorites monzogranites occurred prior to or during isostatic uplift and extension probably caused by breakoff of the subducted slab the resultant exhumation brought deep seated granitoid batholiths to the surface and was contemporaneous with intrusion of ultramafic mafic melts ophiolitic melange ca 362 294 ma and collision related magmatic suites 247 214 ma are unconformably overlain by a late triassic 229 217 ma conglomerate rich sequence that represents an overlap assemblage across the qamdo simao terrane indochina and yangtze block of south china

explosive microfractures induced by k metasomatism abstract ultra fine mineral aggregates in k metasomatic rocks of the hougou area northwestern hebei province china contain peculiar and distinct intergranular and intragranular geometries compositions and textures these features indicate solidification of expanded and enclosed relict fluids within tensile microfractures two basic morphologic types of textures are present saw toothed and wheel shaped and several composite patterns also are present such as x shaped grid and network the appearance of these features indicate explosion from an instantaneous force these microscopic explosive microfractures are directly related to the enclosed relict fluids theoretical estimates show that volume expansion induced by mineral replacements during k metasomatism may have caused the k metasomatic fluids to be confined and strongly compressed in order to build up powerful forces that produced the ultra fine mineral aggregates and explosive microfractures the thick walled texture of k metasomatic rocks confined fractures that propagated only in the replaced rocks with the lowest strength both pumping pressures and the propagation of the k metasomatism were self governed and controlled by introduced chemical elements specially k

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

global glacial isostatic adjustment palaeogeodetic and space geodetic tests of the ice 4g vm2 model analyses of the global process of glacial isostatic adjustment and post glacial relative sea level change continue to deliver important insights into earth system form and process one successful model of the related phenomenology is based upon a spherically symmetric internal viscoelastic structure for the solid earth which has been denoted vm2 and a model of the most recent deglaciation event of the current ice age denoted ice 4g the primary purpose of this paper is to describe several new a posteriori tests that have recently been performed to further investigate the quality of this global solution to the inverse problem for both mantle viscosity and deglaciation history that is posed by the observables associated with this large scale geodynamic phenomenon i focus especially upon the misfits of observations to the theoretical predictions of this model which i am currently using to further refine its properties and upon predictions made using it of geophysical signals that should soon become visible in the context of the gravity recovery and climate experiment grace satellite mission among the required refinements to ice 4g one that is necessary to eliminate a recently revealed misfit to space geodetic constraints on the present day rate of radial motion at the yellowknife location well to the west of hudson bay and a similar misfit to absolute gravity measurements to the southwest of the bay is the insertion of a keewatin dome of thick ice centred over yellowknife with a ridge of ice extending to the south east in the geomorphological literature the existence of such a keewatin dome previously has been hypothesised but chronological control was lacking on the surface features that suggested its former existence an important additional constraint that requires the late glacial existence of this important feature consists of new inferences of the last glacial maximum lowstand of the sea from sites in the far field of the main concentrations of land ice copyright 2002 john wiley sons ltd

sanjiang tethyan metallogenesis in s w china tectonic setting metallogenic epochs and deposit types abstract tectonically the sanjiang tethyan metallogenic domain stmd is located within the eastern himalayan tibetan orogen in the sanjiang tethys southwestern china although this metallogenic domain was initiated in the early palaeozoic extensive metallogenesis occurred in the late palaeozoic late triassic and himalayan tertiary epochs corresponding tectonic settings and environments in the domain are an arc basin system related to the subduction of the palaeo tethyan oceanic slabs a post collision crustal extension setting caused by the lithospheric delamination or slab breakoff underneath the sanjiang tethys during the late triassic large scale strike slip faulting and thrusting systems due to the indo asian continent collision since the palaeocene in this metallogenic domain important gold copper base metals rare metals and tin ore belts incorporating a large number of giant deposits were developed the main types of deposits include 1 porphyry copper deposits controlled by a large scale strike slip fault system 2 vhms deposits mainly occurring in intra arc rift basins and post collision crustal extensional basins 3 shear zone type gold deposits in the ophiolitic melange zone along the thrusting shearing system 4 hydrothermal silver polymetallic deposits in the triassic intra continental rift basins and tertiary strike slip pull apart basins and 5 himalayan granite related greisen type tin and rare metallic deposits within the metallogenic epochs of the late palaeozoic to cenozoic the styles and types of the ore deposits changed from vhms types in the late palaeozoic through exhalative sedimentary type deposits in the late triassic to porphyry type copper deposits shear zone type gold deposits hydrothermal vein type silver polymetallic deposits greisen type tin and rare metal deposits in the cenozoic correspondingly ore forming metals also changed from a pb zn cu ag association through ag cu pb zn fe ag pb and ag au hg associations to ag cu pb zn cu mo au sn and li rb cs nb zr hf y ce sc associations

mobilization and enrichment of high field strength elements during late and post magmatic processes in the shuiquangou syenitic complex northern china abstract the shuiquangou syenitic complex consists of melasyenite and leucosyenite in the northeastern part there is a small area where the leucosyenite was affected by alteration the altered leucosyenite contains much higher concentrations of high field strength elements hfse especially nb zr ree and y compared to fresh leucosyenite ree patterns of the altered leucosyenite show moderate negative eu anomaly in contrast to the slightly positive to non anomalous eu signature of the fresh syenitic rocks allanite from the hydrothermal mineral assemblage in the altered leucosyenite also contains much higher concentrations of ree and ti than the euhedral magmatic allanites in unaltered leucosyenite the enrichment of hfse in altered leucosyenite was interpreted to be caused by the hydrothermal fluids based on mineral chemistry and whole rock data within the fresh leucosyenite allanite occurs in two habits euhedral ones indicating a primary magmatic origin and anhedral ones suggesting a late magmatic origin the latter has higher concentrations of ree and ti than the former the anhedral allanite was presumed to be formed coeval with the alteration of the euhedral allanite as a result of residual magmatic fluid derived directly from the syenitic magma the alteration of magmatic euhedral allanite and the enrichment of ree and ti in the anhedral late magmatic allanite suggest that these elements were mobilized by the residual magmatic fluid both residual late magmatic and hydrothermal fluids have an inferred composition characterized by high alkalic and f contents suggesting that f may be the most ligand that complexed the high valence cations

structure and evolution of the himalaya tibet orogenic belt the 1981 french chinese expedition to tibet focused on the lhasa block extending earlier coverage 400 km north of the tsangpo suture the lhasa block stood between 10 and 15 n latitude over most of the upper cretaceous and eocene and if gondwanian in origin had detached from gondwana by early permian seismic profiles reveal a complex moho topography resulting both from multiple continental thrusting and large scale strike slip faulting subduction related granitoids representing mixtures of mantle and crustal components and anatectic granitoids have been analysed and dated this study emphasizes the role of smaller blocks in the accretion of the continental mosaic

reply to comment on a vertical exposure of the 1999 surface rupture of the chelungpu fault at wufeng western taiwan structural and paleoseismic implications for an active thrust fault by jian cheng lee yue gau chen kerry sieh karl mueller wen shan chen hao tsu chu yu chang chan charles rubin and robert yeats by yuan hsi lee shih ting lu tung sheng shih and wei yu wu we welcome y h lee et al s interest in our article lee et al 2001 we thank them for their comment which provides a further opportunity for discussing the quantification of the slip amounts including horizontal and vertical components and the fault geometry for an earthquake thrust scarp in wufeng western taiwan during the 1999 m 7 6 earthquake in their comment y h lee et al used restoration of deformed concrete fence across the 1999 scarp to estimate the slip vector of the main fault the estimated slip amount especially the horizontal component is different significantly less from our results presented in the 2001 bssa article they then applied an area balance technique to compare their results with ours they showed that their area balance method favored their estimates including the slip amounts and the fault dip angle they concluded that their estimated slip amounts are more reasonable than ours the fundamental questions in this issue in our opinions include the actual amounts of deformation slip and the associated deformation processes as well as the limitation and uncertainty of the applied techniques on an earthquake formed thrust scarp hereafter we attempt to answer these questions and clarify the related problems

an improved glacial isostatic adjustment model for the british isles the glacial isostatic adjustment gia of the british isles is of interest due to the constraints that can be provided on key model parameters such as the global meltwater signal local ice sheet history and viscoelastic earth structure a number of recent studies have modelled relative sea level rsl data from this region to constrain model parameters as indicated in these studies the sensitivity of these data to both local and global parameters results in a highly non unique problem this study aims to address this inherent non uniqueness by combining a previously published british irish ice model that is based on the most recent geomorphological data with a new global ice sheet model that provides an accurate prediction of eustatic sea level change in addition constraints from global positioning system gps measurements of present day vertical land motion are considered alongside the entirety of rsl data from both great britain and ireland a model solution is found that provides a high quality fit to both the rsl data and the gps data within the range of earth viscosity values considered the optimal data model fits were achieved with a relatively thin lithosphere 71 km upper mantle viscosities in the range 4 6 1020 pa s and lower mantle viscosities 3 1022 pa s copyright 2011 john wiley sons ltd

the boundary between the simao and yangtze blocks and their locations in gondwana and rodinia constraints from detrital and inherited zircons abstract the simao block which is the northern extension of the indochina block and the yangtze block were amalgamated by the closure of a paleo tethys branch ocean commonly referred to as the ailaoshan ocean the exact location of the suture between these two continental blocks has been contested some researchers believed that it is located within the cenozoic ailaoshan shear zone whereas other researchers thought that it is present 50 km farther to the west the detrital and inherited xenocrystic zircons from paleozoic sedimentary rocks and a triassic granite dyke respectively in the laowangzhai mojiang suspect terrane which occurs between the two suggested locations for the same suture show that neither of these previously suggested locations is accurate the age distribution pattern of detrital and inherited xenocrystic zircons from the laowangzhai mojiang suspect terrane is similar to that of detrital zircons from the simao indochina block but different from that of those from the jianshui area in the western margin of the yangtze block this indicates that the laowangzhai mojiang suspect terrane belongs to the simao indochina block the actual location of the suture between the simao indochina and yangtze blocks is suggested to superimpose the ailaoshan late devonian to early carboniferous ophiolite belt within the suspect terrane the new interpretation is also supported by hf isotopes of detrital zircons from the related continental blocks the age distribution pattern of precambrian detrital zircons from the western part of the yangtze block is different from that of those from australia or tethyan himalaya the northern part of the indian continent indicating that the yangtze block was not an integral part of australia or india in rodinia the age distribution pattern of pre carboniferous detrital zircons from the simao indochina block is remarkably similar to that of those from the tethyan himalaya indicating that the simao indochina block was derived from indian gondwana

glacial isostatic adjustment of the british isles new constraints from gps measurements of crustal motion summary we compared estimates of crustal velocities within great britain based on continuous global positioning system cgps measurements to predictions from a model of glacial isostatic adjustment gia the observed and predicted values for vertical motion are highly correlated indicating that gia is the dominant geodynamic process contributing to this field in contrast motion of the eurasian plate dominates the horizontal motion component a model of plate motion was adopted to remove this signal in order to estimate intraplate horizontal motion associated with gia however a coherent pattern of horizontal motion was not evident in the resulting velocity field we adopted a recently published model of the british irish ice sheet to predict vertical crustal motion for a large number of spherically symmetric earth viscosity models our results show that the adopted ice model is capable of producing a high quality fit to the observations the cgps derived estimates of vertical motion provide a useful constraint on the average value of viscosity within the upper mantle values of model lithospheric thickness and lower mantle viscosity are less well resolved however a suite of predictions based on an alternative ice model indicates that the vertical motion data are relatively insensitive to uncertainties in the ice loading history and so the constraints on upper mantle viscosity are robust

gold mineralization in as rich mesothermal gold ores of the bogosu prestea mining district of the ashanti gold belt ghana remobilization of invisible gold the bogosu prestea mining district of southwestern ghana is a 33 km section of the early proterozoic ashanti gold belt greenschist facies carbonaceous and carbonate bearing turbidites and greywackes and mafic dikes host numerous economic mesothermal gold deposits structurally higher ores in the bogosu concession have brittle deformation and consist of disseminated sulphide lodes in tectonically disrupted sedimentary rocks and carbonate altered mafic dikes most gold occurs as micrometre size particles in arsenian pyrite and as invisible gold in arsenian pyrite and arsenopyrite the structurally deeper ores of the adjoining prestea concession are associated with brittle ductile deformation and consist of extensive crack seal quartz veins and graphitic shear zones only minor amounts of invisible gold were detected in these deeper lodes gold occurs dominantly as abundant microscopic and larger particles in sulphide arsenide minerals and in gangue the gold distribution patterns revealed by sims microprobe analysis and ion maps emp and colour staining suggest that most of the primary gold in the bogosu prestea system precipitated in solid solution with sulphide arsenide minerals however post depositional concentration and redistribution occurred in increasing degree with 1 increase in metamorphic hydrothermal gradients in the gold system depth 2 decrease in the refractory properties of the host mineral and 3 increase in the amount of post depositional host mineral recrystallization and deformation gold evolved from primary solid solution within sulphide arsenide minerals to colloidal and micrometre size particles concentrated in voids fractures and internal grain boundaries and finally to microscopic and larger particles at sulphide arsenide grain margins and in the gangue assemblage the general conclusions presented here are applicable to as rich gold deposits of all ages worldwide the presence of gold in late fractures is insufficient evidence for late stage introduction of gold in mesothermal gold systems

tidal evolution of the northwest european shelf seas from the last glacial maximum to the present 1 two dimensional paleotidal simulations have been undertaken to investigate tidal and tide dependent changes tidal amplitudes tidal current velocities seasonal stratification peak bed stress vectors that have occurred in the nw european shelf seas during the last 20 ka the simulations test the effect of shelf wide isostatic changes of sea level by incorporating results from two different crustal rebound models and the effect of the ocean tide variability by setting open boundary values either fixed to the present state or variable according to the results of a global paleotidal model the use of the different crustal rebound models does not affect the overall changes in tidal patterns but the timing of the changes is sensitive to the local isostatic effects that differ between the models the incorporation of ocean tide changes greatly augments the amplitude of tides and tidal currents in the celtic and malin seas before 10 ka bp and has a large impact on the distribution of seasonally stratified conditions magnitude of peak bed stress vectors and tidal dissipation in the shelf seas the predictions on seasonal stratification are supported by well dated evidence on tidal mixing front migration in the celtic sea additional experiments using the global model suggest that the variability of offshore tides has been caused mainly by changes of eustatic sea level and ice sheet extent in particular a large decrease observed at 10 8 ka bp is attributed to the opening of hudson strait accompanied by the retreat of the laurentide ice sheet

in situ sulfur isotope analysis by laser ablation mc icpms and a case study of the erlihe zn pb ore deposit qinling orogenic belt central china abstract sulfur isotopic composition is useful for tracing sources of ore forming materials in situ sulfur isotope analysis by laser ablation coupled with multi collector inductively coupled plasma mass spectrometry la mc icpms has an advantage over traditional bulk analysis in tracing sources of sulfur in an ore deposit that has complex mineral types and multiple ore forming processes however in using this method matrix effects exist widely for sulfides from ore deposits in this work matrix effects of different sulfides were examined by matrix unmatched tests in which the 34s values of different types of sulfides were calibrated against a laboratory pyrite standard the results show that the 34s values of pyrrhotite chalcopyrite molybdenite sphalerite and arsenopyrite are in agreement with the reference values suggesting that the matrix effect was negligible however a significant matrix effect occurred in the analyses of ag2s and galena leading to significant deviations in 34s values of up to 1 2 and 3 2 respectively the matrix effect occurred not only during the laser ablation stage but also during the transition of ions into the mass spectrometer resulting in significant space charge effects caused by heavy mass elements thus pyrite can be used as an external bracketing standard for sulfides that do not have a heavy mass matrix based on our matrix effect study the following available external standards were selected for the in situ sulfur isotope analysis of complex type minerals from the erlihe zn pb deposit the coarse grained sphalerite grains sph1 and euhedral to subhedral pyrite grains py1 from massive ores have 34s values ranging from 9 2 to 18 1 such heavy sulfur isotopic compositions indicate the derivation of sulfur from the deposits of seawater sulfate related to a thermochemical reducing process fine grained sphalerite sph2 and pyrite py2 from vein and disseminated ores coexist with pyrrhotite and chalcopyrite and have relatively light sulfur isotopic compositions with 34s values of about 7 the slightly positive 34s values are similar to those of sulfides from sulfide rich quartz veins which contain 34s values of about 4 and granodiorite rocks with 34s values of about 6 based on previous studies the light sulfur of the late stage sulfides may have resulted from a metamorphic or magmatic hydrothermal event during the indosinian orogeny in situ sulfur analysis by la mc icpms provides new evidence for sources of sulfur from each stage of mineralization in the erlihe deposit suggesting that this is a promising method for studying complex ore deposits

late devensian and holocene relative sea level change in north wales uk deglacial sea level index points defining relative sea level rsl change are critical for testing glacial isostatic adjustment gia model output only a few observations are available from north wales and until recently these provided a poor fit to gia model output for the british irish ice sheet we present results of an integrated offshore geophysical seismic reflection coring drilling rig sedimentological micropalaeontological foraminifera biostratigraphical palynology and geochronological ams 14c investigation into a sequence of multiple peat organic sediment horizons interbedded within a thick estuarine marine sequence of minerogenic clay silts to silty sands from the ne menai strait north wales ten new sea level index points and nine new limiting dates from the devensian late glacial and early holocene are integrated with twelve pre existing holocene sea level index points and one limiting point from north wales to generate a regional rsl record this record is similar to the most recent gia predictions for north wales rsl change supporting either greater ice load and later deglaciation than in the gia predictions generated before 2004 or a modified eustatic function there is no evidence for a mid holocene highstand tidally corrected rsl data indicate initial breaching of the menai strait between 8 8 and 8 4 ka bp to form a tidal causeway with final submergence between 5 8 and 4 6 ka bp final breaching converted the ne menai strait from a flood dominated estuary into a high energy ebb tidal delta with extensive tidal scouring of pre existing late glacial and holocene sequences the study confirms the value of utilising offshore drilling coring technology to recover sea level records which relate to intervals when rates of both eustatic and isostatic change were at their greatest and therefore of most value for constraining gia models copyright 2011 john wiley sons ltd

tidal mixing and the meridional overturning circulation from the last glacial maximum 1 using a global tidal model it is shown that the supply of tidal energy to the deep ocean was larger during the last glacial maximum lgm 18 000 22 000 years bp the results were used to modify the rate of vertical mixing in a coupled ocean atmosphere model set up for the present and lgm oceans the increased levels of mechanical energy during the lgm were countered by a fresher upper north atlantic which led to a reduced circulation and deep water formation in spite of a trebling of the implicit mixing energy this identifies the significance of accurately representing vertical mixing in climate models to estimate the recovery time scales and timings of rapid catastrophic paleoceanographic events from the estimated levels of implicit energy in the vertical mixing scheme an amendment to diffusivity based mixing schemes is suggested

evolution of the miocene ailaoshan orogenic gold deposits southeastern tibet during a complex tectonic history of lithosphere crust interaction the orogenic gold deposits along the nnw trending ailaoshan shear zone are formed during miocene continental collision after a complex history of neoproterozoic subduction late triassic amalgamation between the indochina and south china blocks after closure of the paleo tethyan ocean and oligocene eocene continental scale shearing related to the indian eurasian continental collision as a result the eastern neoproterozoic basement with ductile shear zones was thrust over the western metasedimentary rocks and paleo tethyan ophiolites affected by brittle faulting these tectonically juxtaposed successions were underlain by lithosphere metasomatized in the neoproterozoic the gold hosting western succession is characterized by tightly folded silurian to permian metasedimentary rocks overlain by gently folded late triassic metasedimentary rocks and cut by secondary nw trending shear zones this crustal architecture controlled migration of ore fluid towards the cessation of regional ductile deformation at ca 22 ma with major ductile shear zones serving as the main conduit tight folds and jogs or intersections on subsidiary brittle shear zones as the fluid trap and late triassic rocks as the seal gold rich rims on disseminated gold poor sedimentary pyrite with a limited 34s range from 3 to 3 pyrite he ar isotope ratios and the timing of mineralization within retrograde metamorphism suggest an important metal contribution from mantle lithosphere the auriferous fluid derived from previously metasomatized mantle lithosphere is interpreted to have advected up the ailaoshan shear zone into the metasedimentary sequence during mantle upwelling clearly contrasting with widely accepted crustal metamorphic models for phanerozoic orogenic gold deposits

the use of electron backscatter diffraction and orientation contrast imaging as tools for sulphide textural studies example from the greens creek deposit alaska the greens creek polymetallic massive sulphide deposit is hosted in a typical polyphase deformed lower greenschist facies orogenic setting the structure of the host rocks is well constrained exhibiting a series of three superimposed ductile deformations followed by two brittle episodes the ore is found both in fold hinges where early formed depositional features are preserved and in fold limbs where primary features are typically strongly modified or obliterated samples from both settings have been investigated using electron backscatter diffraction ebsd coupled with forescatter orientation contrast oc imaging in order to observe the effects of deformation and lower greenschist facies metamorphism on pyrite results suggest that colloform pyrite may preserve information relevant to palaeoenvironment that apparently simple textures are generally more complex and that pyrite can deform plastically by dislocation glide and creep processes at lower temperatures and or strain rates than generally accepted this analysis indicates that ebsd and oc imaging provide powerful tools for observing textural relationships in pyrite that are not shown by more traditional methods they should become routine tools for pyrite texture analysis

simultaneous measurement of sulfur and lead isotopes in sulfides using nanosecond laser ablation coupled with two multi collector inductively coupled plasma mass spectrometers abstract we herein report the coupling of a nanosecond laser ablation system with a large scale multi collector inductively coupled plasma mass spectrometer nu1700 mc icpms np 1700 and a conventional nu plasma ii mc icpms np ii for the simultaneous laser ablation and determination of in situ s and pb isotopic compositions of sulfide minerals we found that the required aerosol distribution between the two spectrometers depended on the pb content of the sample for example for a sulfide containing 100 3000 ppm pb the aerosol was distributed between the np 1700 and the np ii spectrometers in a 1 1 ratio while for lead contents 3000 and

pt and pd mobility in hydrothermal fluids evidence from komatiites and from thermodynamic modelling abstract komatiite host rocks and ores provide a natural laboratory for the study of pt and pd during hydration and carbonation of ultramafic rocks the degree of correlation between pt and pd and of those elements with lithophile elements such as ti in komatiitic rocks and ores is strongly dependent on the magmatic sulfide content of the rock pt and pd are typically very strongly correlated within s poor komatiites and in disseminated ores containing 5 volume or less magmatic sulfides in contrast they are almost completely decoupled in sulfide rich ore samples thermodynamic modelling based on the existing body of published experimental data on pt and pd solubilities suggests that pd and pt can be readily transported as bisulfide complexes in acidic neutral solutions under reduced and moderate oxidation condition at 300 c and chloride complexes are only important under extremely acidic oxidised conditions pd is much more soluble than pt in the case of fluids in sulfide rich environments in equilibrium with the characteristic assemblages found within altered and metamorphosed komatiites solubilities of both elements are much lower in sulfide poor environments especially where ph values are constrained to neutral values by the near ubiquitous presence of carbonate minerals in the alteration assemblage this accounts for the evident near immobility of pt and pd in even the most altered silicate host rocks as compared with their wide dispersion in sulfide rich ores

testing the mid holocene relative sea level highstand hypothesis in north wales uk accurate holocene relative sea level curves are vital for modelling future sea level changes particularly in regions where relative sea level changes are dominated by isostatically induced vertica

origin of the daping gold deposit in the ailaoshan metallogenic belt sw china insights from geology isotope geochemistry and geochronology abstract the daping gold deposit the most representative gold deposit in the ailaoshan metallogenic belt is located between the southeast sanjiang region three rivers jinshajiang lancangjiang and nujiang and the western yangtze block ore bodies in the daping gold deposit are mainly vein types hosted in the late proterozoic diorite and silurian limestone and controlled by nw trending faults la icp ms zircon u pb dating of granodiorite yielded a late eocene age of 36 76 0 38 ma constraining the upper limit of the main mineralization quartz has d values ranging from 80 to 50 4 average 63 1 and 18 o fluid values ranging from 7 29 to 8 29 in the early stage of mineralization in the late stage quartz has d values ranging from 87 to 67 average 77 4 and 18 o fluid values ranging from 0 24 to 3 86 carbonate minerals have 13 c pdb and 18 o smow values ranging from 2 3 to 7 6 average 5 1 and 9 to 14 9 mean 12 6 the sulfides have a narrow range of 34 s values 0 2 to 6 7 average 3 51 in the main stages of mineralization the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of the sulfides range from 18 685 to 18 765 15 653 to 15 728 and 39 014 to 39 280 in general according to the h o c s pb isotopic compositions the ore forming fluids are dominated by metamorphic fluids and the ore forming fluids and materials might have been mainly derived from the mantle and lower crust with a small input of wall rock material they were affected by meteoric water in the late stage of mineralization given the regional geology ore geology ore forming fluids material features and ore forming age the daping gold deposit can be classified as a typical orogenic gold deposit

gold deposits of the northern margin of the north china craton multiple late paleozoic mesozoic mineralizing events the northern margin of the north china craton is well endowed with lode gold deposits hosting a resource of approximately 900 tonnes t of gold the 1 500 km long region is characterized by east trending blocks of metamorphosed archean and proterozoic strata that were episodically uplifted during variscan indosinian and yanshanian deformational and magmatic events at least 12 gold deposits from the daqinshan yan liao includes the zhangjiakou yanshan and chifeng gold districts and changbaishan gold provinces contain resources of 20 100 t au each most deposits are hosted in uplifted blocks of precambrian metamorphic rocks although felsic paleozoic and mesozoic plutons are typically proximal and host 30 of the deposits the lodes are characterized by sulfide poor quartz veins in brittle structures with low base metal values and high au ag ratios although phyllic alteration is most common intensive alkali feldspar metasomatism characterizes the wulashan dongping and zhongshangou deposits but is apparently coeval with variscan alkalic magmatism only at wulashan stepwise 40ar 39ar geochronology on 16 samples from gangue and alteration phases combined with unpublished shrimp u pb dates on associated granitoids suggest that gold mineralizing events occurred during variscan indosinian and yanshanian orogenies at circa 350 250 200 180 150 and 129 ma however widespread permo triassic 250 ma and early jurassic 180 ma thermal events caused variable resetting of most of the white mica and k feldspar argon spectra as well as previously reported k ar determinations compiled and new stable isotope and fluid inclusion data show that most 18o values for ore stage veins range from 8 to 14 indicating a fluid in equilibrium with the precambrian metamorphic basement rocks d values from fluid inclusions range widely from 64 to 154 which is indicative of a local meteoric component in some veins and highly variable 34s data 7 to 17 even within individual deposits indicate various local country rock sources for sulfur fluid inclusions from all districts show variable homogenization temperatures between 240 and 400 c and are consistently characterized by low salinity h2o co2 ch4 n2 solutions although the data are largely consistent with that from orogenic gold veins intrusion related veins and epithermal veins are also recognized the multiple episodes of mineralization are coincident with episodic tectonic reactivations and associated magmatism along the northern margin of the north china craton electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00126 001 0239 2

magmatic origin for sediment hosted au deposits guizhou province china in situ chemistry and sulfur isotope composition of pyrites shuiyindong and jinfeng deposits

evidence for a magmatic origin for carlin type gold deposits isotopic composition of sulfur in the betze post screamer deposit nevada usa we report here new sulfur isotope analyses from the betze post screamer deposit the largest carlin type gold deposit in the world carlin type deposits contain high concentrations of arsenic antimony mercury tellurium and other elements of environmental interest and are surrounded by large volumes of crust in which these elements are also enriched uncertainty about the source of sulfur and metals in and around carlin type deposits has hampered formulation of models for their origin which are needed for improved mineral exploration and environmental assessment previous studies have concluded that most carlin type deposits formed from sulfide sulfur that is largely of sedimentary origin most of these studies are based on analyses of mineral separates consisting of pre ore diagenetic pyrite with thin overgrowths of ore related arsenian pyrite rather than pure ore related pyrite our sims spot analyses of ore related pyrite overgrowths in the screamer zone of the betze post screamer deposit yield 34s values of about 1 to 4 with one value of about 7 conventional analyses of realgar and orpiment separates from throughout the deposit yield 34s values of about 5 7 with one value of 10 in the screamer zone these results along with results from an earlier sims study in the post zone of the deposit and phase equilibrium constraints indicate that early arsenian pyrite were formed from fluids of magmatic origin with variable contamination from sulfur in paleozoic sedimentary rocks later arsenic sulfides were formed from solutions to which sulfur of sedimentary origin had been added the presence of paleozoic sedimentary sulfur in carlin type deposits does not require direct involvement of hydrothermal solutions of sedimentary origin instead it could have been added by magmatic assimilation of paleozoic sedimentary rocks or by hydrothermal leaching of sulfur from wall rocks to the deposit thus the dominant process delivering sulfur arsenic gold and mineralizing fluids to carlin type systems and their surrounding country rocks was probably separation of fluids from a magmatic source

a vertical exposure of the 1999 surface rupture of the chelungpu fault at wufeng western taiwan structural and paleoseismic implications for an active thrust fault we mapped and analyzed two vertical exposures exposed on the walls of a 3 to 5 m deep 70 m long excavation and a smaller 3 m deep 10 m long excavation across the 1999 rupture of the chelungpu fault the primary exposure revealed a broad anticlinal fold with a 2 5 m high west facing principal thrust scarp contained in fluvial cobbly gravel beds and overlying fine grained overbank deposits sequential restoration of the principal rupture requires initial failure on the basal east dipping thrust plane followed by wedge thrusting and pop up of an overlying symmetrical anticline between two opposing secondary thrust faults net vertical offset is about 2 2 m across the principal fault zone from line length changes we estimate about 3 3 m of horizontal shortening normal to fault strike the ratio of these values yields a total slip of 4 0 m and an estimate of about 34 for the dip of the fault plane below the excavation this value is nearly the same as the 35 average dip of the fault plane from the surface to the hypocenter restoration of the exposed gravelly strata and adjacent overbank sediments deposited prior to the 1999 event around the principal rupture suggests the possible existence of a prior event a buried 30 m wide anticlinal warp beneath the uplifted crest of the 1999 event is associated with three buried reverse faults that we interpret as evidence for an earlier episode of folding and faulting in the site the prior event is also recorded in the smaller excavation which is located 40 m south and is oriented parallel to the larger excavation radiocarbon dating of samples within the exposed section did not place tight constraints on the date of the previous event available data are interpreted as indicating that the previous event occurred before the deposition of the less than 200 14 c yr b p overbank sands and after the deposition of the much older fluvial gravels we interpret the previous event as the penultimate event relative to the 1999 chi chi earthquake we estimated the long term slip rate of the chelungpu fault to be 10 15 mm yr during the last 1 ma based on previously published retrodeformable cross sections this rate is however significantly higher than geodetic rates of shortening across the chelungpu thrust where two pairs of permanent global positioning system stations suggest 7 10 mm yr of shortening across the fault given the 4 m of average slip the long term slip rate yields an interseismic interval of between 267 and 400 yr for the chelungpu fault

glaciation and sea level change for ireland and the irish sea since late devensian midlandian time the sea level change around the coast of ireland and the irish sea for the past 20 000 years is primarily the combined result of the glacio isostatic adjustment of the crust to the removal of ice over the british isles and the total eustatic change from the global ice sheets however the isostatic effects due to the removal of ice from northern europe and north america and the addition of meltwater into the oceans also make a significant contribution predictions of sea level change based on glacio hydro isostatic models are compared with observations to constrain the ice volume over ireland at the time of the last glacial maximum and the maximum ice height appears to have been of the order of 600 m the models predict well the spatial variability in sea level change observed across the region for holocene and lateglacial time with levels above present being predicted only for northeastern ireland and north of about morecambe bay the models do not support suggestions that lateglacial levels along the east coast of ireland or the coast of wales were 50 150 m above their present levels consistent models that would produce such large lateglacial highstands are incompatible with all other sea level and glacial evidence for the british isles palaeobathymetry and palaeoshoreline reconstructions for the irish sea indicates that a tenuous landbridge between britain and ireland developed only across the celtic sea between about 18000 and 14000 years bp

multistage sedimentary and metamorphic origin of pyrite and gold in the giant sukhoi log deposit lena gold province russia gold mineralization at sukhoi log in eastern siberia is hosted in a deformed neoproterozoic organic bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline the deposit contains about 30 million ounces of gold at an average grade of 2 0 g t au and is one of the largest known undeveloped gold resources the high grade gold zone forms a gently dipping tabular body in the core of the anticline the best gold grades occur in narrow bedding parallel pyrite quartz veinlets that have been folded during the main deformation event lower grade gold is associated with disseminated pyrite developed in and around the high grade core of the deposit detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments the two earliest forms of pyrite termed py1 and py2 are commonly developed in stratiform layers of micron sized crystals framboids and fine euhedra which are interpreted as synsedimentary to early diagenetic in origin coarser grained bedding parallel aggregates of inclusion rich pyrite termed py3 contain inclusions of arsenopyrite native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation coarse euhedral pyrite py4 overgrows the earlier pyrite py1 py2 and py3 and the slaty cleavage developed in the host rocks indicating a syndeformation timing late stage inclusion free pyrite py5 overgrows and replaces earlier sulfides and is considered to be syn to late deformation laser ablation inductively coupled plasma mass spectrometry la icpms analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold varying from 0 4 to 12 1 ppm with a mean of 3 22 ppm au and 1 900 ppm as py1 is also enriched in a suite of trace elements mo sb ni co se te ag cu pb zn mn ba cr u v which are similar to those concentrated by organic processes in euxinic sedimentary environments later generations of pyrite from py2 to py5 including pyrite in bedding parallel pyrite quartz veinlets contain progressively lower contents of invisible gold and most other trace elements however this metamorphic and postmetamorphic pyrite contains microinclusions of free gold arsenopyrite pyrrhotite sphalerite and chalcopyrite the paragenetic textural and chemical relationships at sukhoi log suggest that gold was clearly initially introduced prior to cleavage development accompanying sedimentation of the organic rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite subsequently accompanying deformation gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding parallel pyrite quartz veinlets two key processes are considered vital to the formation of the sukhoi log deposit original synsedimentary and early diagenetic concentration of gold dissolved within arsenian pyrite in organic rich black shales and metamorphic processes that liberated gold from the early forms of arsenian pyrite to be concentrated as free gold and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite quartz veinlets in the core of an overturned anticline these ore forming processes are unlikely to be unique to sukhoi log other black shale and turbidite hosted deposits that occur in rifted continental margin environments which have undergone collision and basin inversion may form by similar processes

la icp ms trace element analysis of pyrite from the chang an gold deposit sanjiang region china implication for ore forming process abstract the chang an gold deposit yunnan province is one of five large gold deposits in the ailaoshan gold belt that is the most important ore belt of the sanjiang tethyan metallogenic domain geochemical study of pyrite in the deposit was conducted using laser ablation inductively coupled plasma mass spectroscopy three types of hydrothermal pyrite were identified in the ores and wall rocks i e the coarse euhedral crystals in syenite py1 the coarse grains disseminated in altered sandstones or sandstone ores py2 and the fine grained euhedral pyrite in sandstone ores py3 their trace elements exhibit different concentrations associations and rim core zoning implying different geneses and crystallization processes the cores of py1 were formed by magmatic fluids and have the lowest concentrations of au as cu and zn the cores of py2 were formed by metamorphic fluids and have relatively high au ag ni pb and cu concentrations the py3 grains and the growth rims of py1 and py2 show consistently high contents of au as pb and co suggesting that all of them were rapidly deposited from a mixing fluid system that was probably composed of fluids of metamorphic and magmatic origins this interpretation is supported by the observation that the high grade ores generally contain lots of py2 and py3 hence we consider that the deposit was formed during india asia collision slightly postdate the 33 35 ma tectono magmatism

the central ailaoshan ophiolite and modern analogs abstract the central ailaoshan cal ophiolite represents an important tectonic component of the jinshajiang ailaoshan song ma suture zone separating the south china and indochina blocks in the mainland se asia the cal ophiolite occurs as a complex tectonic melange and preserves the history of the opening and closure of the once vast jinshajiang ailaoshan song ma branch of the paleotethys new and existing geological data indicate that the cal ophiolite contains magmatic rocks generated by 1 l devonian e carboniferous ca 380 330 ma volcanic passive margin breakup development in the nw gondwana margin 2 l permian ca 258 ma emeishan large igneous province related continental rift magmatism together with and intruded by 3 earliest m triassic ca 244 ma continent continent syn collisional s type granitoids the devono carboniferous suites of the cal ophiolite are highly comparable with many continental margin type alpine tethyan ophiolites in addition the various cal magmatic suites have strong south china block affinities with coeval magmatism particularly in the western south china block jinshajiang song ma and song da terranes

modeling of gold scavenging by bismuth melts coexisting with hydrothermal fluids the effect of gold scavenging by bismuth melts is investigated using equilibrium thermodynamic modeling of an aqueous solution mineral melt system the calculations for the au bi na cl s h o system performed at temperatures between 300 and 450 c demonstrate that au concentrations in the melt are several orders of magnitude higher than in the coexisting fluid indicating the possible formation of economic gold deposits from undersaturated aqueous fluids in which mineralization would not be expected in the absence of a bismuth melt the model applies to any deposit where a bi melt is stable and coexists with a hydrothermal fluid examples of such deposits are known from skarn intrusion related orogenic and volcanogenic massive sulfide vms gold systems in sulfur poor systems the partitioning curves presented here can be used directly to correlate the gold concentration in the fluid and the au grade in the ore e g escanaba trough vms deposit these results also illustrate important principles generally applicable to understanding magmatic hydrothermal and metamorphic deposits that may have contained significant volumes of more complex polymetallic melts

glacial rebound and sea level change in the british isles observations of sea levels around the coastline of the british isles for the past 10 000 15 000 years exhibit a major regional variation and provide an important data base for testing models of glacial rebound as well as models of the late devensian ice sheet a high resolution rebound model has been developed which is consistent with both the spatial and temporal patterns of sea level change and which demonstrates that the observations are the result of i the glacio isostatic crustal rebound in response to the unloading of the ice sheet over britain and to a lesser degree of the ice sheet over fennoscandia and ii the rise in sea level from the melting late pleistocene ice sheets including the response of the crust to the water loading the hydro isostatic effect the agreement between model and observations is such that there is no need to invoke vertical crustal movements for great britain and ireland of other than glacio hydro isostatic origin the rebound contributions are important throughout the region and nowhere is it sufficiently small for the sea level change to approximate the eustatic sea level rise the observational data distribution around the periphery as well as from sites near the centre of the former ice sheet is sufficient to permit constraints to be established on both earth model parameters specifying the mantle viscosity and lithospheric thickness and the extent and volume of the ice sheet at the time of the last glaciation preliminary solutions are presented which indicate an upper mantle viscosity of 3 5 1020 pas a lithospheric thickness of about 100 km or less and an ice model that was not confluent with the scandinavian ice sheet during the last glaciation and whose maximum thickness over scotland is unlikely to have exceeded about 1500 m

a discussion of monian supergroup stratigraphy in northwest wales new borehole data and trench exposures in northern anglesey show the gwna group melange resting directly upon disrupted sedimentary rocks of the new harbour group field evidence from anglesey and the ll n peninsula shows that units previously given formal lithostratigraphic status in the higer part of the monian sopergroup occur as clasts within the gwna group melange me wbdivision of the monian supergroup is therefore simplified to comprise only three groups the south stack lowest new har bour and gwna groups highest the disruption of the upper part of the new harbour group is interpreted to have been efferied during emplacement of the gwna group melange

global to local scale parameters determining relative sea level changes and the post glacial isostatic adjustment of great britain abstract observations of relative sea level rsl change in great britain since 16 kyr bp and models of post glacial isostatic adjustment provide constraints on reconstructions of the british and antarctic ice sheets from the last glacial maximum to the present we use the global model from an earlier investigation modified ice 4g vm2 with lithospheric thickness 90 km which gives good rsl fits globally as well as for much of the british data a revised ice model for great britain that fits with recently published observations on ice limits and heights fails to explain all the misfits between rsl observations and predictions much more significant improvements result from models that incorporate a different chronology for the partial deglaciation of antarctica while keeping the total ice melt 17 m the same as in ice 4g vm2 the results suggest antarctic melting of 3 m ice equivalent sea level by 15 kyr bp only 1 m contribution to the 24 m rise of mwp1a with the major melting 12 5 kyr bp and a small amount of melting 1 0 0 3 m between then and 3 or 2 kyr bp these modifications produce rsl predictions for barbados that show the major changes in rate of sea level rise but with an offset up to 1 kyr compared to the observations possible explanations that remain to be investigated further are a delay in the melting of ice from some other region a reduction in the total melt derived from antarctica and a refinement of the 1 kyr temporal resolution assumed in the construction of the theoretical solution

modelling the glacial isostatic adjustment of the uk region the glacial isostatic adjustment of the uk region has been considered in a number of recent studies we have revisited this problem in order to i highlight some key issues with regard to limitations in the ice modelling approach adopted in these studies and ii consider the constraints provided from observations of crustal motion available via continuous global positioning system monitoring with regard to the first aim we have found that i previous studies have significantly overestimated ice thicknesses in regions where trim line field constraints were adopted and ii the duration of the glaciation phase of the uk ice sheet is a critical aspect of the model and that discrepancies in this model component have led to inconsistent inferences of earth model parameters with regard to the second aim we have found that predictions of horizontal velocities relative to a chosen site based on a uk ice model calibrated to fit the regional sea level database capture the geometry of the signal well but only account for 10 of the magnitude for a range of earth models

surface ruptures on the transverse xiaoyudong fault a significant segment boundary breached during the 2008 wenchuan earthquake china abstract the 220 km long rupture of the 2008 mw 7 9 wenchuan earthquake breached several km scale geometric discontinuities along strike including the previously un mapped nw trending xiaoyudong fault connecting between the two major ne trending rupture planes on the beichuan and pengguan faults in this paper we present high resolution mapping of the 8 km long surface breaks and sinistral oblique thrusting coseismic slip on the xiaoyudong fault scarp height is the largest at the nw end reaching 3 5 m and decreases southward in steps to less than 0 2 m with an average slip gradient of 6 10 3 at a few tens of meters length scale but up to 50 10 3 locally left lateral offsets co vary with the vertical component the largest sinistral slip vector we observed is 2 2 m geological and geophysical evidence suggests that the xiaoyudong fault is likely a 30 sw dipping lateral ramp that soles into the pengguan fault and at its northwestern end intersects with the beichuan fault where the latter has a step in the fault plane kinematically the xiaoyudong fault functions as a tear and conjugate fault and coincides with significant coseismic slip rake rotations on both the beichuan and pengguan faults similar correlation of fault bends with sharp changes in faulting style occurs at other steps along the wenchuan rupture the xiaoyudong fault may have played a positive role in linking coseismic slip partitioning between parallel reverse fault planes facilitating the growth of a longer and more destructive rupture this highlights the role of tear faults in bridging ruptures between segments such that reverse type ruptures can breach steps wider than anticipated from strike slip fault examples transfer faults are common and perhaps poorly documented features in reverse fault systems and their roles in ruptures may increase the maximum potential earthquake magnitude for fold and thrust belts

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

middle and late holocene sea level changes in eastern maine reconstructed from foraminiferal saltmarsh stratigraphy and ams 14c dates on basal peat abstract a relative sea level history is reconstructed for machiasport maine spanning the past 6000 calendar years and combining two different methods the first method establishes the long term 10 3 yr trend of sea level rise by dating the base of the holocene saltmarsh peat overlying a pleistocene substrate the second method uses detailed analyses of the foraminiferal stratigraphy of two saltmarsh peat cores to quantify fluctuations superimposed on the long term trend the indicative meaning of the peat the height at which the peat was deposited relative to mean tide level is calculated by a transfer function based on vertical distributions of modern foraminiferal assemblages the chronology is determined from ams 14 c dates on saltmarsh plant fragments embedded in the peat the combination of the two different approaches produces a high resolution replicable sea level record which takes into account the autocompaction of the peat sequence long term mean rates of sea level rise corrected for changes in tidal range are 0 75 mm yr between 6000 and 1500 cal yr b p and 0 43 mm yr during the past 1500 years the foraminiferal stratigraphy reveals several low amplitude fluctuations during a relatively stable period between 1100 and 400 cal yr b p and a sea level rise of 0 5 m during the past 300 years

metallogenic model of the jinchang au ni deposit in the ailaoshan belt sw china determined on the basis of pyrite trace element contents in situ sulfur isotope composition and pge geochemistry abstract the ailaoshan metallogenic belt in southwestern china contains numerous shear zone related au deposits with au reserves greater than 200 tonnes however the source of ore forming fluids and metals is controversial hampering the construction of genetic models in this study we selected the jinchang au ni deposit in the northern segment of the ailaoshan belt for detailed investigation of pyrite chemistry and in situ sulfur isotope compositions using laser ablation inductively coupled plasma mass spectrometry la icp ms the petrographic and pyrite chemistry analyses revealed four types of hydrothermal pyrite py1 pyrite is euhedral to subhedral and has in situ sulfur isotope 34s values of 5 30 to 6 26 median 2 93 and low concentrations of au ni as sb cu zn pb and ag py1 is interpreted to have formed during the early hydrothermal stage py2 pyrite is subhedral to anhedral and porous with variable size although py2 and py3 show different textural relationships we conclude that both of them formed during the intermediate hydrothermal stage as evidenced by similar sulfur isotope compositions and trace element contents and common intergrowth textures py2 and py3 pyrite have in situ 34s values ranging from 11 6 to 1 29 median 4 45 and relatively elevated concentrations of au ni as sb cu zn pb and ag in py2 and py3 pyrite ni concentrations correlate with co concentration whereas au exhibits moderate positive correlations with ni co and as indicating that au ni and other metals were predominantly sourced from the jinchang ultramafic rocks py4 pyrite is euhedral in shape and has relatively low in situ 34s values of 23 5 to 4 34 median 8 33 the metal concentrations in py4 pyrite are lower than those in py2 and py3 pyrite in general the metal concentrations in the different pyrite populations display systematic changes with low levels in py1 higher levels in py2 andpy3 and low levels again in py4 the average total platinum group element pge concentration of the jinchang ni bearing ultramafic rocks is 26 3 ppb similar to the average value of the primitive mantle of 22 0 ppb the au ni ores from the jinchang deposit have an average pd pt ratio of 5 98 similar to that of hydrothermal ni ores but higher than that of typical magmatic ni ores in contrast the jinchang ultramafic rocks have low pd pt ratios between 0 57 and 1 13 suggesting that the pges in the jinchang intrusion are of magmatic origin similarly the rh ir ratios of au ni ores are consistent with those of hydrothermal ni ores but differ from those of magmatic ni ores the pyrite chemistry in situ sulfur isotope compositions and pge geochemistry suggest that the ore forming fluids and metals associated with the jinchang au ni deposit were dominantly derived from the jinchang ultramafic intrusion mesozoic felsic magmatism or cenozoic regional strike slip activity may have triggered migration of the ore forming fluids leaching of metals from the jinchang intrusion and precipitation of these metals at the boundary between the intrusions and carbonaceous rocks

representative styles of deformation along the chelungpu fault from the 1999 chi chi taiwan earthquake geomorphic characteristics and responses of man made structures the chi chi earthquake provides dramatic evidence of the damaging effects of surface ground deformation to buildings lifelines and other facilities much of the building damage is associated with surface faulting and folding along the chelungpu thrust fault our detailed surveying at representative sites along the fault shows that the rupture commonly is a relatively simple 1 to 4 m high scarp with minor hanging wall deformation and localized but severe uplift folding and graben formation along the scarp crest for individual scarps the width of deformation is about 10 to 20 times the net vertical displacement distributed secondary faulting and folding on the hanging wall occurred as much as 350 m from the primary fault near the northern end of the rupture growth of a pre existing 1 km wide late quaternary anticline produced severe ground rupture along multiple thrusts and backthrusts but only minor tilting between fault strands the pattern of building damage coincides with the pattern of geologic deformation with severe damage along large fault scarps and lesser but still significant damage attributable to distributed secondary surface deformation on the hanging wall rupture related building damage on the footwall occurred next to the prerupture fault trace where the hanging wall bulldozed onto the footwall the width of this damage zone is related to the local horizontal shortening along the fault and generally is less than 10 m building zonation along reverse faults should account for this pattern of surface deformation in addition buildings with massive foundations locally influenced the style and location of near surface deformation producing variations in fault strike or accentuated secondary deformation on the hanging wall manuscript received 15 january 2001

in situ sulfur isotope analysis by laser ablation mc icpms abstract a new method for in situ s isotopic analysis was tested using a laser ablation system together with a multi collector mc icpms the method was tested for the analysis of pyrite pyrrhotite chalcopyrite and pentlandite using a large pyrite crystal as an in house standard repeated measurements of py pn po and cpy provide an average internal precision of less than 0 1 2 the method was also applied to a pyrite bearing orogenic au deposit to display the ability of the method to resolve minor variations in 34s across growth zoning in pyrite

source of ore forming fluids of the yangshan gold field western qinling orogen china evidence from microthermometry noble gas isotopes and in situ sulfur isotopes of au carrying pyrite abstract the yangshan gold ore belt contains a series of sediment hosted disseminated gold deposits in the southern subzone of the western qinling orogen the ore deposits formed in the middle devonian carbonaceous clastic carbonate sequences that underwent strong deformation and low greenschist facies regional metamorphism the shapes and distribution of the ore bodies are strictly confined by the e w trending anchanghe guanyinba thrust fault zone pyrite and arsenopyrite are the major au carrying minerals microthermometric results show that the ore forming fluids are co2 rich aqueous solutions the homogenization temperatures range from 221 to 303 5 c and salinities range from 2 0 to 7 2 wt nacl equiv these characteristics are consistent with orogenic gold deposit noble gas isotopic measurement shows that 3he 4he ratios of pyrite and quartz grains inherited from the mineralized carbonaceous phyllite ranging from 0 033 to 0 081 ra implying that the origins of ore fluids are restricted within the crustal regime the 40ar 36ar ratios range from 434 to 863 indicating 34 to 68 crust derived radiogenic 40ar in the ore fluids based on the backscattered electron bse maps of pyrite three generations i e core mantle rim are distinguished pre ore pyrite including framboidal pyrites and the cores of zoned pyrites both in the phyllite and plagiogranite dikes ore stage pyrites including the middle zones of the three zoned pyrites in the granitic dikes and the outer zones of the zoned pyrites in the phyllite post ore pyrites i e the outermost rims of the zoned pyrites in the dikes the arsenopyrite in the phyllite has similar texture to the pyrite and is regarded as the peak of the mineralization due to its highest au concentrations high spatial resolution nanosims multi elemental maps of the pyrites reveal that i gold is distributed heterogeneously as lattice bounded au in the zoned pyrites with higher au as in the middle zones and lower au as in the inner and outermost zones no nano particles of native gold was identified in pyrite ii gold mineralization occurred in a single event instead of multistage ore formation iii gold precipitation event is followed by an overgrown zone with low au and as concentrations in situ sulfur isotopes of au bearing pyrite identified two types of sulfur sources one is framboidal pyrite and the barren core of pyrite in the carbonaceous phyllite which have very negative 34s values combining au concentrations with the corresponding 34s values in the pyrites reveals that the zones with high au have lower 34s values and vice versa this coupling relation between au and s isotope has been also identified in other orogenic and carlin type gold deposits the oxidation of ore fluid is taken as the key for gold precipitation during formation of orogenic gold deposit however the oxidation of ore fluids accompanied by the escape of reduced gas e g h2s should result in high au coupled with high 34s therefore we propose that the yangshan gold deposit forms through partitioning aqueous vapor with high au as and lower 34s from a deep magma chamber under the ore field which leads to overgrowth of the pre existing pyrites based on the geological features texture of pyrite and sulfur isotopic characteristics we suggested that the yangshan gold deposits have the characteristics between carlin type and orogenic gold deposits they are the product of the western qinling orogeny during the late triassic

residual flow bedforms and sediment transport in a tidal channel modelled with variable bed roughness abstract the frictional influence of the seabed on the tidal flow in shelf seas and estuaries is usually modelled via a prescribed spatially temporally invariant drag coefficient in practice the seabed exhibits considerable variability particularly spatially that should in principle be included in simulations local variations in the seabed roughness k s alter the flow strength and hence local sediment transport rates the effect of using a spatially temporally varying k s is assessed here with reference to a tidal channel menai strait n wales in which the variability of the bedforms has been monitored using multi beam surveying the channel not only exhibits strong tidal flow but also a residual induced flow that is used here as diagnostic to assess various bed roughness formulations tested in a telemac model tidal simulations have been carried out with both constant and temporally spatially variable k s and the predicted residual flow is shown to be sensitive to these representations for a mean spring neap sn cycle with variable k s the average residual flow is calculated to be 525 m 3 s 1 consistent with observations this residual flow can be recovered using imposed constant values of k s in the range 0 15 m to 0 3 m the results suggest that the overall effective roughness of the seabed is less than half of the maximum local roughness due to the dunes in mid channel but more than the spatially averaged k s value in the channel as a whole by about 50 simulations carried out with an m 2 alone tide using variable k s produce a somewhat smaller by 7 residual flow of 491 m 3 s 1 the use of an equivalent m 2 tide of amplitude enhanced by 7 3 reconciles these estimates the main contribution to k s is made by dunes which are modelled using van rijn s 2007 formulation subject to an additional history effect the modelled k s is found to equal approximately the observed height of the dunes along mid channel transects rather than half the height as expected this is attributed to the non equilibrium nature of the bedforms in the reversing tidal flow which exhibited shorter wavelength and more symmetrical profiles than dunes in steady flow

reconstruction of fault slip of the september 21st 1999 taiwan earthquake in the asphalted surface of a car park and co seismic slip partitioning abstract the deformation in the asphalted surface of a car park near wufeng 24 1 n 120 41 e reveals the three dimensional behaviour of the surface rupture of the september 21st 1999 taiwan earthquake the n s striking fault dips 30 e and is reverse almost dip slip it accounts for about one half of the total nw se shortening of the whole fault zone the remaining deformation occurred inside the upthrust block in a damaged zone less than 3 km wide and is dominated by n s left lateral shear this distribution of co seismic deformation highlights fault slip partitioning along an oblique fault zone at a depth shallower than 1 7 km

fluid inclusion and noble gas studies of the dongping gold deposit hebei province china a mantle connection for mineralization the dongping gold deposit 100 t au occurs about 200 km inboard of the northern margin of the north china craton the deposit is mainly hosted by syenite of a middle paleozoic alkalic intrusive complex that was emplaced into late archean basement rocks both groups of rocks are intruded by late jurassic to early cretaceous crustal melt granite dikes and stocks some within a few kilometers of the deposit the gold ores were deposited during this latter magmatic period at about 150 ma a time that was characterized by widespread regional north south compression that formed the east west trending yanshan deformational belt the ores include both the telluride mineral bearing low sulfide quartz veins and the highly k feldspar altered syenite with most of the resource concentrated in two orebodies 1 and 70 fluid inclusion microthermometry indicates heterogeneous trapping of low salinity e g 5 7 wt nacl equiv fluids that varied from a few to 60 mole percent nonaqueous volatile species laser raman spectroscopy confirms that the vapor phase in these inclusions is dominated by co2 but may be comprised of as much as 9 mole percent h2s and 20 mole percent n2 methane concentrations in the vapor phase are consistently 1 mole percent the variable phase ratios are consistent with fluid immiscibility during ore formation fluid inclusion trapping conditions are estimated to be 250 to 375 c and 0 6 to 1 0 kbar helium isotope studies of fluid inclusions in ore stage pyrites indicate 3he 4he ratios of 2 1 to 5 2 ra ra 1 4 10 6 for air for orebody 1 and 0 3 to 0 8 ra for orebody 70 the former data suggest that at least 26 to 65 percent mantle helium occurs in the fluids that deposited the veins in orebody 1 the lower values for orebody 70 which is characterized by a more disseminated style of gold mineralization are interpreted to reflect an increased interaction of ore fluids with surrounding crustal rocks which may have contributed additional 4he to the fluids a mantle source for at least some of the components of the gold forming fluid is consistent with upwelling of hot asthenosphere and erosion of as much as 100 to 150 km of cool archean lithosphere beneath the craton during this time the dongping deposit is located along the 100 km wide north south gravity lineament which marks the western border of the thinned crust as both regional metamorphism of mesoproterozoic and younger cover rocks and widespread granite magmatism also occurred at ca 150 ma it is unclear as to whether one or both of these also contributed fluid and or metals to the hydrothermal system importantly these new data suggest that economically significant gold deposits of similar mineral style and fluid composition which are scattered along the margins of the craton may all be products of a fluid originally partly sourced within the mantle

on the postglacial isostatic adjustment of the british isles and the shallow viscoelastic structure of the earth summary observations of postglacial relative sea level rsl history at sites beyond the margins of the main accumulations of wu rm wisconsin devensian ice may be invoked to test the accuracy of global models of the glacial isostatic adjustment process the existing database of rsl time series for the british isles forms a continuous network of sites that sample the coasts of scotland england and wales fairly uniformly and which may be especially important in this regard not only are these 14c data for the holocene epoch of very high quality in terms of our knowledge of the coastal environment and relationship to palaeo sea level of each age measurement but they are especially numerous and relate to an island that was itself partly glaciated in the north essentially ice free in the south and located well outboard of the massive ice sheet that covered fennoscandia at the last glacial maximum lgm taken together the time series from 55 distinct locations allow us to perform a fairly stringent test of the recently formulated ice 4g vm2 global model of the isostatic adjustment process even without modification this model has been shown to fit most of the time series in the uk data set rather well in order to satisfy very recently published a priori constraints on the maximum thickness of the scottish ice sheet however we find that the lithospheric thickness the feature of the radial viscoelastic structure to which the rebound data from scotland are most sensitive must be somewhat reduced whereas the assumed thickness of the lithosphere in ice 4g vm2 was near to 120 km best fits to the scottish data require a lithospheric thickness near to 90 km this reduced value for lithospheric thickness agrees exceedingly well with the latest estimates of this earth property based on the inversion of oceanic geoid and topography data as the asymptotic thickness characteristic of the oldest ocean floor this would appear to be the best possible a priori estimate for the thickness of the cratonic lithospheres upon which the largest ice sheets of the late pleistocene are known to have rested we also demonstrate explicitly that inferences of the shallow viscoelastic structure beneath the british isles are strongly influenced by the details of the history of deglaciation at remote locations at antarctica in particular

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

pge distribution in massive sulfides from the pacmanus hydrothermal field eastern manus basin papua new guinea implications for pge enrichment in some ancient volcanogenic massive sulfide deposits the distribution of platinum group elements pge in cu and zn rich samples from the roman ruins and satanic mills vent sites in the pacmanus hydrothermal field papua new guinea was studied and compared to that from selected ancient volcanogenic massive sulfide vms deposits samples from the satanic mills site are enriched in pd and rh when compared to samples from roman ruins and reach highest values in active and inactive cu rich black smoker chimneys and chalcopyrite cemented dacite breccias up to 356 ppb pd and up to 145 ppb rh a significant positive correlation was established between cu and pd and rh in samples from both vent sites comparisons of chondrite normalized patterns and values of pd pt and pd ir ratios in cu rich sulfides and probable source rocks felsic volcanic rocks morb along with the evidence for a magmatic component in the pacmanus hydrothermal system indicate that leaching of back arc volcanic rocks together with addition of magmatic volatiles to the convecting hydrothermal system was the most important factor for pge enrichment at pacmanus and likely at some pge enriched ancient vms deposits

postglacial relative sea level observations from ireland and their role in glacial rebound modelling the british isles have been the focus of a number of recent modelling studies owing to the existence of a high quality sea level dataset for this region and the suitability of these data for constraining shallow earth viscosity structure local to regional ice sheet histories and the magnitude timing of global meltwater signals until recently the paucity of both glaciological and relative sea level rsl data from ireland has meant that the majority of these glacial isostatic adjustment gia modelling studies of the british isles region have tended to concentrate on reconstructing ice cover over britain however the recent development of a sea level database for ireland along with emergence of new glaciological data on the spatial extent thickness and deglacial chronology of the irish ice sheet means it is now possible to revisit this region of the british isles here we employ these new data to constrain the evolution of the irish ice sheet we find that in order to reconcile differences between model predictions and rsl evidence a thick spatially extensive ice sheet of 600 700 m over much of north and central ireland is required at the lgm with very rapid deglaciation after 21 k cal yr bp copyright 2007 john wiley sons ltd

mantle crustal and atmospheric noble gases in ailaoshan gold deposits yunnan province china abstract helium and argon isotopic and elemental compositions of fluids released by crushing pyrite grains are reported from the ailaoshan gold province china the province is a series of gold deposits hosted on a 200 km segment of a major normal fault formed during eocene extension the deposits have been well characterised using conventional geochemical and microthermometric techniques the results of which are consistent with a predominantly high temperature magmatic fluid present in the ore minerals in contrast analyses of noble gases from three gold deposits demonstrate the palaeofluids were a mixture between a mantle derived magmatic fluid and two different low temperature fluids similar to modern groundwaters the specific isotopic and abundance characteristics of helium and argon allow unequivocal identification of both a mantle derived component and a surface derived component to these fluids the magmatic fluid dominates deposits from the northern end of the fault the second groundwater is present only in deposits in the south of the province by assuming fluid inclusion homogenisation temperatures in coexisting quartz are representative of fluid temperature 3he heat ratios can be estimated the 3he heat ratios vary systematically along the fault from 30 10 12 cm3 stp j 1 in the northern deposits to

quantitative analysis of movement along an earthquake thrust scarp a case study of a vertical exposure of the 1999 surface rupture of the chelungpu fault at wufeng western taiwan a vertical exposure across the principal thrust scarp of the 1999 mw 7 6 earthquake allows quantification offault slip the exposure is located on the active chelungpu fault near wufeng along the range front of the fold and thrust belt in western taiwan the 1999 surface ruptures at the wufeng site are characterized by a west facing 2 to 3 m high principal thrust scarp and an east facing lesser backthrust scarp we mapped a 15 mlong 5 m deep exposure across the principal thrust scarp and characterized complex deformation structures which include a main basal thrust fault a wedge thrust and a pop up anticlinal fold with two secondary opposing thrust faults the vertical displacement across the principal thrust scarp is measured directly from the offsets of the same sedimentary horizons between the hangingwall and the footwall the average vertical displacement is 2 2 0 1 m and the maximum displacement is 2 5 m at the crest of the small pop up fold horizontal displacement estimates were determined using line and area balancing methods with line length methods we estimated a horizontal displacement of 3 3 0 3 m across the principal scarp for four sedimentary horizons for area balancing first we selected three horizontal soil sand deposits with a total thickness of about 0 5 m the estimate yields an average horizontal displacement of 4 8 1 0 m using these individual and relatively thin stratigraphic layers yielded significant standard deviations in displacement estimates as a result of thickness variations second we used the 3 mthick overbank soil sand and the lower part offluvial pebble cobble to calculate a horizontal displacement of 2 6 0 2 m with the area balancing technique according to the geometry of the dip angle 35 408 of the basal thrust the line length measurement and the 3 m thick package area balancing both providedreasonable results of horizontal displacement by comparing thedifferent deposits applied to theline and area balancing methods we interpret that decoupling of deformation occurred between the lower fluvial gravels and the upper overbank sand and mud deposits due to lesser confining pressure at the surface additional deformation occurred in the upper 1 2 m thick overbank deposits this additional deformation yielded further vertical uplift of 0 3 0 5 m and horizontal displacement of 0 2 0 8 m around the core of the pop up fold our work suggests that determination of slip across surface thrust ruptures varies as a function of the mechanical behavior of young late quaternary deposits q 2003 elsevier ltd all rights reserved

pyrite and pyrrhotite textures and composition in sediments laminated quartz veins and reefs at bendigo gold mine australia insights for ore genesis the various types textures and compositional zoning of pyrite in the gold bearing saddle reefs quartz veins and surrounding sedimentary rocks provide new information on the potential source and timing of gold and arsenic and related fluid processes responsible for mineralization at bendigo nodular diagenetic pyrite in the black shale tops to sandstone turbidites is enriched in invisible gold and arsenic with mean values of 0 61 ppm au 1 300 ppm as and au ag 1 based on la icpms analyses other elements enriched in the diagenetic pyrite within the organic rich shales are mn zn mo cu v ba ag cd tl co ni bi pb and te in contrast euhedral and growth zoned hydrothermal pyrite in the turbidites and bedding parallel laminated quartz veins contains lower contents of most trace elements but has higher contents of invisible au and as especially on the outermost rim of the pyrite the gold rich pyrite rims generally become thicker a few to hundreds of microns in proximity to the gold bearing saddle reefs pyrite in the reef commonly has the highest levels of invisible au and as and the lowest levels of other trace elements it is characterized by au ag 1 and au pb 0 01 in the deepest stratigraphic levels below known productive gold reefs diagenetic pyrite in the most carbonaceous shales has been replaced by pyrrhotite during metamorphism la icpms analyses reveal that the disseminated pyrrhotite contains similar levels of ni and co to the diagenetic pyrite but is strongly depleted in as and au the spatial relationships between organic rich shales folded bedding parallel laminated quartz veins and gold arsenic bearing saddle reefs combined with the consistent trends in the trace element composition of pyrite hosted by these three geological elements is interpreted to indicate that the black shales were an initial source of au and as and the laminated quartz veins acted as the initial pathways for hydrothermal fluid flow carrying au and as from the source shales to the saddle reefs maximum gold and arsenic input into the reefs principally as free gold plus arsenopyrite occurred late during deformation toward the end of the hydrothermal cycle and is expressed by the au as rich rims to hydrothermal pyrite in the sedimentary host rocks laminated quartz veins and reefs this corresponds with final fold lockup and the development of through going fault arrays linking adjacent anticlines the source of au and as for this final and most economically important fluid flow event is considered to be from carbonaceous shales deeper in the basin where original gold bearing diagenetic arsenian pyrite reacts with organic matter and is converted to pyrrhotite with release of au as and s to the metamorphic fluid

invisible gold in ore and mineral concentrates from the hillgrove gold antimony deposits nsw australia vein hosted mesothermal stibnite gold mineralisation at the hillgrove au sb mine in northeastern new south wales has a halo of veinlet and disseminated auriferous arsenopyrite and arsenian pyrite in metasedimentary and granitic host rocks about 50 55 of the gold produced at hillgrove occurs invisibly in arsenopyrite and pyrite gold losses of 20 into tailings are due to this mineral chemical factor from pixe probe analyses it has been found that arsenopyrite contains 255 1500 ppm au and pyrite 24 223 ppm au with au contents of each mineral correlating moderately with as content arsenopyrite and pyrite also contain anomalous values of cu ag and sb whereas paragenetically later stibnite contains little invisible gold but minor fe as ag cu and pb the precipitation of invisible gold in arsenopyrite and pyrite by a possible fe au 3 as s 3 substitution mechanism may have been facilitated by rapid non equilibrium conditions involving pressure decreases and wall rock reaction sulphidation carbonatisation as a prelude to the main stage of stibnite and gold deposition

impact of sea level rise over the last deglacial transition on the strength of the continental shelf co2 pump 1 although shelf seas account for only 7 of the oceanic surface area recent observations demonstrate that they host significant ocean atmosphere co2 fluxes a mechanism implicated in driving a significant co2 sink in the temperate shelf seas is the continental shelf pump here we present an analysis of the impact of sea level rise and the consequent flooding of continental shelves on the growth of the continental shelf co2 pump over the last deglacial transition we combine reconstructions of shelf palaeogeography bathymetry and tides with contemporary shelf sea atmosphere co2 flux estimates to demonstrate the potential of the expanding shelf seas to have impacted on the global carbon cycle via the continental shelf co2 pump over the past 21 000 years and by inference earlier glacial interglacial cycles

a review of the geodynamic setting of large scale late mesozoic gold mineralization in the north china craton an association with lithospheric thinning abstract abundant gold deposits are distributed along the margins of the north china craton ncc occurring throughout the precambrian basement and located in or proximal to mesozoic granitoids these deposits show a consistent spatial temporal association with late jurassic early cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock their ages are mainly early cretaceous 130 110 ma and constrain a very short period of metallogenesis sr nd pb isotopic tracers of ores minerals and associated rocks indicate that gold and associated metals mainly were derived from multi sources i e the wall rocks precambrian basement and mesozoic granites and associated mafic rocks previous studies including high surface heat flow uplift and later basin development slow seismic wave speeds in the upper mantle and a change in the character of mantle xenoliths sampled by paleozoic to cenozoic magmas have been used to suggest that ancient cratonic mantle lithosphere was removed from the base of the ncc some time after the ordovician and replaced by younger less refractory lithospheric mantle the geochemistry and isotopic compositions of the mafic rocks associated with gold mineralization 130 110 ma indicate that they were derived from an ancient enriched lithospheric mantle source whereas the mafic dikes and volcanic rocks younger than 110 ma were derived from a relatively depleted mantle source i e asthenospheric mantle according to their age and sources relation to magmatism and geodynamic framework the gold deposits were formed during lithospheric thinning the removal of lithospheric mantle and the upwelling of new asthenospheric mantle induced partial melting and dehydration of the lithospheric mantle and lower crust due to an increase of temperature the fluids derived from the lower crust were mixed with magmatic and meteoric waters and resulted in the deposition of gold and associated metals

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene

relative sea level changes glacial isostatic modelling and ice sheet reconstructions from the british isles since the last glacial maximum while contributing 1 m equivalent eustatic sea level rise the british isles ice sheet produced glacio isostatic rebound in northern britain of similar magnitude to eustatic sea level change or global meltwater influx over the last 18 000 years the resulting spatially variable relative sea level changes combine with observations from far field locations to produce a rigorous test for quantitative models of glacial isostatic adjustment local ice sheet history and global meltwater influx after a review of the attributes of relative sea level observations significant for constraining large scale models of the isostatic adjustment process we summarise long records of relative sea level change from the british isles and far field locations we give an overview of different global theoretical models of the isostatic adjustment process before presenting intercomparisons of observed and predicted relative sea levels at sites in the british isles and far field for a range of earth and ice model parameters in order to demonstrate model sensitivity and the resolving power available from using evidence from the british isles for the first time we show a good degree of fit between relative sea level observations and predictions that are based upon global earth and ice model parameters independently derived from analysis of far field data with a terrain corrected model of the british isles ice sheet that includes extensive glaciation of the north sea and western continental shelf that does not assume isostatic equilibrium at the last glacial maximum and keeps to trimline constraints of ice surface elevation we do not attempt to identify a unique solution for the model lithosphere thickness parameter or the local scale detail of the ice model in order to provide a fit for all sites but argue that the next stage should be to incorporate an ice sheet model that is based on quantitative glaciological model simulations we hope that this paper will stimulate this debate and help to integrate research in glacial geomorphology glaciology sea level change earth rheology and quantitative modelling copyright 2006 john wiley sons ltd

development of framboidal pyrite during diagenesis low grade regional metamorphism and hydrothermal alteration distribution patterns microstructural relationships and compositional variations for framboidal pyrite in the paleozoic sedimentary host rocks to gold deposits on the northern carlin trend nevada and at fosterville in central victoria collectively demonstrate that it is not all of synsedimentary early diagenetic origin framboidal pyrite also nucleated in hydrothermal veins formed at several kilometers depth and along dissolution surfaces stylolites and crenulation cleavages formed during metamorphism at up to anchizonal grade i e prehnitepumpellyite facies there are no obvious differences in either the size range or internal morphology of framboids formed in these various settings suggesting that a single relatively simple crystallization path may operate over a wide depth range in the upper crust at fosterville anomalously metal rich including au framboidal pyrite is most abundant adjacent to laminated shear veins that developed by slip along bedding surfaces during folding of the sedimentary host rocks microstructural relationships and pb isotope compositions for the framboidal pyrite and other similarly distributed early formed sulfides support development in response to the localized episodic influx of metal enriched h 2s bearing hydrothermal fluids during regional deformation between 440 and 400 ma these findings may have implications for other similarly deformed metasedimentary successions where the discovery of au bearing framboidal pyrite has recently been cited as evidence for significant au enrichment during sedimentation 2009 society of economic geologists inc

sea level change in the irish sea since the last glacial maximum constraints from isostatic modelling models of glacio hydroisostatic sea level change have been published for the british isles that are broadly consistent with the observational evidence as well as with glaciological constraints it has been argued however that the models fail to represent sea level change along the irish sea margins and in southern ireland for the post deglaciation period the argument rests on the interpretation of the depositional environment of the elevated irish sea drift on both sides of the irish sea whether this is terrestrial or glaciomarine the isostatic models for the british isles are consistent with the former interpretation in that sea levels on either side of the irish sea south of about the isle of man are not predicted to have risen above present sea level at any time since the deglaciation of the irish sea this implies that ice over both the irish sea and ireland was relatively thin ca 600 700 m over ireland if the glaciomarine interpretation of the elevated irish sea drift is correct then the maximum ice thickness over central and southern ireland would have to reach 2000 m exceeding that over scotland furthermore for the resulting sea level change to be consistent with the holocene evidence this thick ice sheet could not have extended to the eastern side of the irish sea nor could it have been very thick at its northern and western limits if such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the irish sea drift as terrestrial in origin copyright 2001 john wiley sons ltd