emergent long lived gondwanaland vs submergent short lived laurasia supercontinental and pan african heat imparts long term buoyancy by mafic underplating gondwanaland was buoyant as indicated by nonmarine facies and laurasia was depressed as indicated by marine facies as a supercontinent gondwanaland lasted much longer than laurasia and was hotter from internal heat moreover the pan african orogenic cycle confined to gondwanaland augmented the heat supply which possibly generated a permanently buoyant lower crust by underplating a crustal layer in the australian proterozoic shield with subhorizontal reflectors and velocity vp 7 5 km s is interpreted as mafic underplating beneath latest neoproterozoic flood basalt the pan african terrane in east africa also contains evidence of mafic underplating and most of gondwanaland but not laurasia was affected by terminal pan african 0 5 ga uplift and cooling

folded continental and oceanic nappes on the southern side of monte rosa western alps italy anatomy of a double collision suture 1 previous work suggested a double collision suture including ophiolites from two oceanic basins valais and piemont liguria on the southern side of monte rosa penninic alps northern italy this area was studied using field mapping microstructural analysis and neutron texture goniometry after its formation and eclogite facies metamorphism of continental and oceanic units the suture was deformed by four successive folding and shearing events under greenschist facies conditions all of them taking place between 40 and 28 ma after fold retrodeformation the following tectonostratigraphy results from base to top monte rosa gneiss european margin balma serpentinite eclogite unit cretaceous crust of valais ocean stolemberg gneiss iberia brianconnais continent zermatt saas and tsate ophiolites jurassic crust of piemont ligurian ocean sesia nappe continental fragment off the adria margin the preservation of this lithological sequence suggests that deep seated deformation during multiple continent collision produces heterogeneous strain and extreme thinning of nappes but their original stacking order can still be reconstructed using kinematic analysis and overprinting criteria this is due to the ductile nature of the collisional deformation which retains the continuity of tectonic contacts

metamorphic field gradients in the central alps metamorphic field gradients were determined across the entire amphibolite grade central alps c 50 100 km p t were calculated from 116 samples acquired from our own field work from samples provided to us by others and from rocks with mineral compositions described in the literature only fluid conserved equilibria were used to determine p t the use of an internally consistent thermodynamic database and mineral solid solution models makes the results robust and reduces relative errors the results are presented in contour maps temperature increases from 500 to 550 c along the limit of amphibolite grade metamorphism in the north and west to c 675 c toward the south at the insubric line near the town of bellinzona maximum recorded pressures of c 7 kbar are in a central region c 20 km north of the insubric line and decrease both to the north 5 5 kbar and south 4 5 kbar the p t results indicate that there is a relatively large area that reached conditions in the sillimanite stability field but developed neither sillimanite nor fibrolite this is interpreted as a result of kinetic constraints on nucleation and growth because of the small amounts of thermal overstep 40 c of the kyanite sillimanite phase boundary comparison of p t conditions with carbonate isograds in the region indicate that fluids present during metamorphism were not dominated by a homogeneous external source examination of the two dimensional distribution of pressure and temperature in the context of thermal and tectonic models indicates that two thermal pulses aected the central alps during the tertiary in the second heat aected only the southern parts of the area and overprinted the previously established p t gradients

longshore variability of beach states and bar types in a microtidal storm influenced low energy environment beach classification models are widely used in the literature to describe beach states in response to environmental conditions these models were essentially developed for sandy barred to barless beaches in micro to mesotidal environments subject to moderate to high wave energy conditions and have been based on field studies over limited stretches of coast here we further interrogate the performance of the australian beach classification scheme by analysing beach states and corresponding bar types on a regional scale in a storm influenced low wave energy microtidal environment using a large and unique spatial and temporal dataset of supra and subtidal beach morphology and sedimentology the 200 km long coast of the gulf of lions in themediterranean consists of quasi continuous sandy beaches with a well developed double sandbar system all the reported classical beach stateswere observed on this coast from reflective to dissipative alongwith two more unusual states the rock platform constrained beach state which is associated with bedrock outcrops and the non barred dissipative beach statewhich ismore commonly found in large tidal range settings lidar bathymetry shows that the transitions between beach state zones are marked mainly headlands but transitions also occur progressively along stretches of continuous sandy beach the longshore distribution of beach states and associated bar types on a regional scale can be related to the variability of hydrodynamic conditions wave incidence and energy and sediment characteristics particle size however the influence of these parameters on beach state seems to be largely controlled by the geological context such as the presence of a river mouth headland or rock platform finally we assessed the ability of the parameter commonly used to characterise beach states which combines wave characteristics and sediment fall velocity to predict the observed beach states and bar types using a very large set of hydrodynamic and sedimentary data our results based on high frequency spatial sampling show that the fall velocity of the subtidal sediment coupled with wave statistics one month prior the observed beach state strongly improved the predictive power of the parameter

controls on the composition of ni cu sulfide deposits as illustrated by those at noril sk siberia the ni cu pge ore deposits of the noril sk region have developed in feeder channels for permo triassic continental flood basalt volcanism particularly within 100 to 300 m thick elongate stratified intrusions that merge with an extensive system of peripheral sills through which the magma is thought to have continued to surface the mineralization is centered within two ore junctions the noril sk and talnakh ore junctions principal ore types include massive ore which occurs typically below or at the lowest margin of the intrusions disseminated ore in picritic and taxitic gabbrodolerite which constitute the lower part of the intrusions and copper ore which either forms an impregnation in hornfelsic country rock adjacent to massive ore or occupies the matrix of breccia zones that have developed at the front and upper contact of the intrusions although showing a close spatial relationship to the intrusions the massive ore particularly that underlying the northwest talnakh intrusion appears to have been injected separately over 500 samples have been analyzed for ni cu s pt pd rh ru ir os and au by nis fire assay acid dissolution and neutron activation the massive ore of the kharayelakh orebody beneath the northwest talnakh intrusion has fractionated as injection proceeded from east to west with the fractionated liquid moving progressively farther west this liquid has also soaked into the surrounding hornfels to produce the cu rich mantle and above the western part of the kharayelakh orebody where the cu enrichment is most pronounced has also affected the lower part of disseminated ore zones within the intrusion study of the disseminated ore has revealed that this has not fractionated to a great degree and that adequate sampling gives an average composition close to that of the primary sulfide liquid disseminated ore from different parts of the talnakh ore junction are characterized by very different metal tenors with rh ranging from 4 000 to 10 000 ppb the composition of the disseminated ore is modeled as the result of initial low tenor sulfides becoming trapped in the ore bearing intrusions and then interacting with successive surges of new magma passing along the feeder channels represented by their host intrusions on the way to the surface the different tenors of the different ore junctions and parts of ore junctions are the consequence of the effective number of times the magma passing through a particular channel exceeds the amount of sulfide within the channel higher ratios leading to higher tenors

a crustal scale cross section of the south western alps combining geophysical and geological imagery a geotransect across the south western alps from the pelvoux massif external french alps to the dora maira massif internal italian alps through the monviso ophiolitic complex was investigated in the framework of the geo france 3d alpes programme a new interpretative crustal scale section across the south western alps is proposed combining geological and geophysical 2d 3d data the apulian mantle i e the ivrea body might be divided into two rigid pieces separated by the downward prolongation of the penninic frontal thrust these mantle indenters drive the decoupling of the european crust beneath the high to ultra high pressure metamorphic nappes the deep structure results from the stacking of crustal slices extracted from the european lithosphere the proposed struc tural model provides a basis for discussing the evidence of the crustal scale partitioning of the current strain pattern as well as the location of the seismicity

sand transport processes and bed level changes induced by two alternating laboratory swash events abstract sand transport processes and net transport rates are studied in a large scale laboratory swash zone bichromatic waves with a phase modulation were generated producing two continuously alternating swash events that have similar offshore wave statistics but which differ in terms of wave swash interactions measured sand suspension and sheet flow dynamics show strong temporal and spatial variability related to variations in flow velocity and locations of wave capture and wave backwash interactions suspended and sheet flow layer transport rates in the lower swash zone are generally of same magnitude but sheet flow exceeds the suspended load transport by up to a factor four during the early uprush the bed level near the inner surf zone is relatively steady during a swash cycle but changes of o cm s are measured near the mid swash zone where wave swash interactions lead to strongly non uniform flows the two alternating swash events produce a dynamic equilibrium with bed level changes up to a few mm induced by single swash events but with net morphodynamic change over multiple events that is two orders of magnitude lower most of the intra swash and the single event averaged bed level changes in the swash zone are caused by a redistribution of sediment within the swash the transport of sediment across the surf swash boundary is minor at intra swash time scale but becomes increasingly significant at swash averaged time scales or longer i e averaged over multiple swash events

magnetic fabric and its significance in the sills and lava flows from taimyr fold belt arctic siberia abstract magnetic fabric research on the emplacement of the taimyr fold belt is still absent therefore we have performed magnetic fabric studies on samples collected from 23 sites from mafic igneous rocks 75 n 100 e in south taimyr this study indicates a correlation between the anisotropy of magnetic susceptibility ams magma flow and fold related compression in the rocks ams measurements on 183 unheated and 122 heated samples reveal the magma flow directions the magma flow direction is mainly parallel to the ese wnw and secondarily parallel to the ssw from the nne in the mafic sills the unheated and heated basaltic flows reveal a ne trending flow vector in some of the sills ams shows a tight clustering of the maximum k1 axes close to the bedding pole which is not thought to define the flow direction corresponding ams measurements on igneous rocks allow us to infer the existence of magnetic fabrics of tectonic origin linked to the main folding episode that occurred subsequent to the mid triassic magmatic event in latest triassic early jurassic times in the sills the distribution of most maximum k1 axes is close to ns that corresponds to the maximum compressive stress or folding directions contrarily the minimum k3 axes have an elongated distribution along the ew direction or parallel to the fold axis before exchanging k1 and k3 axes for inverse fabrics but close to the ns stress direction after exchanging k1 and k3 axes for inverse fabrics in the basaltic flows the minimum k3 axes almost parallel to the ns folding direction the structural interpretation of all ams data taken from the igneous bodies is in accordance with a nnw sse stress related folding taking place around 198 ma in the taimyr peninsula arctic siberia the relationship of susceptibility axes to bedding surfaces and magnetic foliation planes is a criterion that permits differentiation of normal magnetic fabrics from inverse fabrics in the igneous samples single domain sd and small pseudo single domain psd magnetite crystals in the sill samples are the main carriers of the ams fabrics implying the abundance of inverse magnetic fabrics psd and multidomain md titanomagnetite tm grains as well as minor hematite are identified in the basalt flows suggesting the occurrence of more normal magnetic fabrics in the basalts than in the sills

process based one dimensional model for cyclic longshore bar evolution abstract a wave averaged process based one dimensional model for beach profile change was developed to predict the cyclic evolution of longshore bars the cross shore sediment transport was assumed to be composed of suspended load due to wave breaking and bed load due to velocity skewness acceleration skewness and beach slope the model s performance was investigated using the beach profile data obtained every weekday during a 12 year period from 1989 to 2000 along a 400 m long pier at the hazaki oceanographical research station located on the hasaki coast of japan where the mean duration of bar evolution is approximately 1 year the model was unable to reproduce bar development from a rather flat profile possibly because some sediment movement process was missing in the model however the model calibrated with a 1 year data set including the bar evolution cycle consisting of bar generation seaward migration decay and new bar generation can be used to predict the first cycles of bar evolution at hasaki

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

on bar growth and decay during interannual net offshore migration abstract multiple bar systems often show a cyclic net offshore directed migration with return periods on the order of years generally a bar is generated near the shoreline grows in height and width while migrating offshore before finally decaying at the seaward limit of the surf zone based on a three year hindcast of a bar cycle at noordwijk netherlands and on additional synthetic runs using a wave averaged cross shore process model this study identifies the dominant mechanisms that govern the bar amplitude growth and decay during net interannual offshore migration the bar amplitude response is particularly sensitive to the water depth above the bar crest h xb and the angle of wave incidence these variables largely control the amount of waves breaking on the bar and the strength and cross shore distribution of the associated longshore current the longshore current has its maximum landward of the bar crest inducing additional stirring of sediment on the landward bar slope and trough the enhanced sediment concentration in the trough region shifts the cross shore transports peak landward of the bar crest forcing bar amplitude growth during offshore migration for increased h xb values wave breaking becomes less frequent consequently reducing the influence of the longshore current on sediment stirring therefore the resulting dominance of the cross shore current results in a sediment transport peak at the bar crest causing bar amplitude decay all four types of bar response viz all combinations of onshore offshore migration and bar amplitude growth decay can occur for a single wave height and wave period combination depending on h xb and additional hindcast runs in which the wave direction was assumed time invariant confirmed that h xb and largely control the transient bar amplitude response

geochemistry of the siberian trap of the noril sk area ussr with implications for the relative contributions of crust and mantle to flood basalt magmatism the sequence investigated of the siberian trap at noril sk ussr consists of at least 45 flows that have been divided into six lava suites the lower three suites consist of alkalic to subalkalic basalts the ivakinsky suite overlain by nonporphyritic basalts the syverminsky suite and porphyritic and picritic basalts the gudchikhinsky suite the upper three suites are tholeiitic the uppermost 750 m of dominantly non porphyritic basalt belong to the mokulaevsky suite and are characterized by a nearly constant mg number 0 54 0 56 sio2 48 2 49 1 wt ce 12 18 ppm and ce yb 5 8 the underlying 1100 m of dominantly porphyritic basalt belong to the morongovsky and nadezhdinsky suites there is a continuous increase in sio2 48 1 55 2 wt ce 12 41 ppm and ce yb 5 18 from the top of the mokulaevsky to the base of the nadezhdinsky with little change in the mg number 0 53 0 59 mokulaevsky magmas have trace element signatures similar to slightly contaminated transitional type mid ocean ridge basalts the change in major and trace element geochemistry in the upper three suites is consistent with a decline in the degree of anatexis and assimilation of tonalitic upper crust by mokulaevsky magma the nadezhdinsky and underlaying lavas thicken within and thus appear to be related to an elongate basin centred on the noril sk talnakh mining camp the mokulaevsky and morongovsky lavas thicken to the east and appear to be related to a basin centred more than 100 km to the east of the noril sk region these magmas may have risen up out of a different conduit system

remobilisation of the continental lithosphere by a mantle plume major trace element and sr nd and pb isotope evidence from picritic and tholeiitic lavas of the noril sk district siberian trap russia the late permian to early triassic siberian traps have been sampled by drill core core sg 9 and from surface exposure section 1f in the noril sk region of the siberian platform russia combined major trace element and nd sr and pb isotope data on selected samples through the siberia trap offer new chemostratigraphic criteria for the identification and characterisation of two fundamentally different magma types and 9 of the 11 formations of lava developed near noril sk a lower sequence of sub alkalic basalts tholeiites and picritic basalts upwards these are the ivakinsky syverminsky and gudchichinsky formations are overlain by an upper sequence of picritic basalts and tholeiites interbedded with tuffs upwards these are the khakanchansky tuklonsky nadezhdinsky morongovsky mokulaevsky and kharayelakhsky formations the gudchichinsky and tuklonsky formations contain both picritic and tholeiitic lavas the tuklonsky formation tholeiites and picrites have moderate gd yb 1 6 1 8 low tio2 0 45 0 95 wt a significant negative ta and nb anomaly nb la 0 42 0 57 and unradiogenic nd nd chur to 4 6 in contrast both the gudchichinsky formation tholeiites and picrites have high gd yb 2 3 3 1 and tio2 1 2 2 3 wt no significant nb or ta anomaly nb la 0 8 1 1 and radiogenic nd nd chur to 7 3 the low ti and nb la high la sm and unradiogenic nd isotope signatures of the picritic tuklonsky formation lavas and the tholeiitic lavas of the upper sequence are characteristic of magmas strongly influenced by material from the continental lithosphere whereas the high ti and nb la low la sm and radiogenic nd isotope signatures of the lower sequence are more comparable to deeper asthenospheric mantle plume generated lavas similar to oceanic island basalts the lavas overlying the tuklonsky formation have mg numbers of 0 63 to 0 68 and are more evolved than the tuklonsky mg number 0 62 and have more radiogenic nd chur tuklonsky 0 03 to 4 66 mokulaevsky 0 60 to 1 61 but have many of the incompatible trace element features of the tuklonsky sky type magma these lavas show a progressive upwards decline in sio2 55 49 wt la sm 4 6 2 0 and ur sr 67 to 13 which has previously been attributed to a decrease in the proportion of crustal material contributed to the magma this paper explores and alternative model where a component of the crustal contribution might be derived from within an ancient region of the mantle lithosphere as recycled sediment rather than from the overlying continental crust

structural lithological and geochemical constraints on the dynamic magma plumbing system of the jinchuan ni cu sulfide deposit nw china eastern and western portions of the jinchuan ultramafic intrusion have previously been interpreted as dismembered segments of a single elongate intrusion by late faults however the different stratigraphic sequences of the two portions indicate that they are originally two separate intrusions referred to as eastern and western intrusions in this study the eastern intrusion is characterized by a concentric distribution of rock types with a core of sulfide dunite enveloped by lherzolite whereas the western intrusion is composed of the upper and lower units interpreted as magmatic mega cycles with regular variations in lithology and chemistry in the western intrusion the upper unit consists of fine grained dunite lherzolite and pyroxenite from its base to its top the mgo contents decrease upward from the dunites 42 45 wt to the lherzolites 36 41 wt while al2o3 and incompatible elements increase upward in contrast the lower unit consists of coarse grained dunites and lherzolites containing 37 40 and 28 35 wt mgo respectively sharp contacts between the upper and lower units and fine grained dunite xenoliths at the top of the lower unit indicate that the lower unit intruded along the base of the upper unit disseminated and net textured sulfides primarily occur in the lower unit and comprise the no 24 ore body very low s contents 100 ppm of the wall rocks at jinchuan indicate that they were not the source of s causing sulfide immiscibility sulfide segregation more likely occurred in deep seated magma chambers and sulfides were deposited in the western intrusion when sulfide bearing magmas passed through the intrusion in contrast the eastern intrusion was formed by injections of sulfide free and sulfide bearing olivine crystal mushes respectively from another deep seated staging magma chamber the eastern and western intrusions and the deep seated magma chambers comprise a complicated magma plumbing system at jinchuan normal faults played a significant role in the formation of the magma plumbing system and provided pathways for the magmas

modeling cross shore sandbar behavior on the timescale of weeks we compare predictions of a coupled wave averaged cross shore waves currents bathymetric evolution model to observations of onshore and offshore nearshore sandbar migration the observations span a 10 and 44 day period with onshore offshore bar migration at duck north carolina and at hasaki kashima coast japan respectively a 3 5 month period of onshore bar migration at duck and a 22 day period of offshore bar migration at egmond netherlands with best fit parameter values the modeled temporal evolution of the cross shore bed profiles agrees well with the observations model skill defined as 1 minus the ratio of prediction to no change error variances ranges from 0 50 at egmond to 0 88 for the prolonged onshore bar migration at duck localized in time and space reductions in model skill coincide with alongshore variations in the observed morphology consistent with earlier observations simulated offshore bar migration takes place during storms when large waves break on the bar and is due to the feedback between waves undertow suspended sediment transport and the sandbar simulated onshore bar migration is predicted for energetic weakly to nonbreaking conditions and is due to the feedback between near bed wave skewness bedload transport and the sandbar with negligible to small effects of bound infragravity waves and near bed streaming under small waves and conditions when breaking and nonbreaking conditions alternate with the tide the sandbar is predicted to remain stationary the intersite differences in the optimum parameter values are at least partly induced by insensitivity to parameter variations parameter interdependence and errors in the offshore wave forcing

cross shore modelling of multiple nearshore bars at a decadal scale abstract this paper presents a numerical model designed to simulate subaqueous cross shore profile behavior including response of feeder mounds and barred systems the present model development builds on the semi empirical model proposed by larson et al 2013 designed to simulate the evolution of longshore bars exposed to incident waves as well as the exchange of material between the bar and the berm region here efforts are made to expand the theory for the evolution of a single bar to a 2 bar system where the volumes of the individual bars inner and outer and their responses are modeled in order to investigate the predictive capacity of the model this exploratory numerical tool is first calibrated and validated against data from duck north carolina usa where 2 bars typically appear inner and outer field data derived from nearshore sand placement projects silver strand state park california and cocoa beach florida usa involving the construction of artificial longshore bars are also employed to test the model in complex situations with diverse wave climates and typical beach profile shapes the study presented in this paper shows that the equilibrium based model is skilled at predicting the time varying volume of the outer bar e 0 39 nmse 0 24 suggesting that this morphological feature is strongly influenced by offshore wave forcing in a predictable equilibrium forced manner model skill was lower e 0 51 nmse 0 29 when predicting the inner bar evolution at duck remaining questions about the predictability and the equilibrium driven cross shore behavior of more transient features model prediction of the evolution of feeder mounds artificial bars proved to be also successful through description of hypothetical bars characterized by zero equilibrium bar volume leading to a good agreement with the field observations overall the potential for using rather simple models to quantitatively reproduce the main trends of cross shore volume changes in bars in a time perspective from years to decades has been demonstrated

rapid adjustment of shoreline behavior to changing seasonality of storms observations and modelling at an open coast beach an 8 year time series of weekly shoreline data collected at the gold coast australia is used to examine the temporal evolution of a beach focusing on the frequency response of the shoreline to time varying wave height and period intriguingly during 2005 the movement of the shoreline at this site changed from a seasonally dominated mode annual cycle to a storm dominated monthly mode this unexpected observation provides the opportunity to explore the drivers of the observed shoreline response utilizing the calibration of an equilibrium shoreline model to explore the time scales of underlying beach behavior the best fit frequency response days 1 is shown to be an order of magnitude higher post 2004 suggesting that a relatively subtle change in wave forcing can drive a significant change in shoreline response analysis of available wave data reveals a statistically significant change in the seasonality of storms from predominantly occurring at the start of the year pre 2005 to being relatively consistent throughout the year after this time the observed change from one mode of shoreline variability to another suggests that beaches can adapt relatively quickly to subtle changes in the intra annual distribution of wave energy this article is protected by copyright all rights reserved

morphodynamics of prograding beaches a synthesis of seasonal to century scale observations of the columbia river littoral cell abstract findings from nearly two decades of research focused on the columbia river littoral cell crlc a set of rapidly prograding coastal barriers and strand plains in the u s pacific northwest are synthesized to investigate the morphodynamics associated with prograding beaches due to a large sediment supply from the columbia river the crlc is the only extensive stretch of shoreline on the u s west coast to have advanced significantly seaward during the late holocene since the last cascadia subduction zone csz earthquake in 1700 with associated co seismic subsidence and tsunami much of the crlc has prograded hundreds of meters however the rates of progradation and the processes most responsible for sediment accumulation vary depending on time scale and the morphological unit in question remarkably the 20th and early 21st century shoreline change rates were more than double the late prehistoric rates that include recovery from the last major csz event most likely due to an increase in sediment supply resulting from inlet jetty construction in some locations detailed beach morphology monitoring reveals that at interannual to decadal scale the upper shoreface aggraded about 2 cm yr subtidal sandbars migrated offshore and decayed while intertidal bars migrated onshore and welded to the shoreline the shoreline prograded about 4 m yr and 1 to 2 new foredune ridges were generated a detailed meso scale sediment budget analysis in one location within the littoral cell shows that approximately 100 m3 m yr accumulated between 12 m seaward limit of data and 9 m crest of landward most foredune gradients in alongshore sediment transport net onshore directed cross shore sediment transport within the surf zone and cross shore feeding from a shoreface out of equilibrium with forcing conditions are each partially responsible for the significant rates of sediment supplied to the beaches and dunes of the crlc during the observational period direct observations of beach progradation at seasonal to decadal scale are put in context of measured or inferred changes over time scales of decades to centuries

a simple equilibrium model for predicting shoreline change abstract this contribution describes the development calibration and verification of a 1 d behaviour orientated shoreline prediction model the model primarily encapsulates shoreline displacement forced by wave driven cross shore sediment transport hysteresis effects are shown to be important and are included in the model whereby present shoreline change is influenced by past hydro morpho dynamic conditions the potential magnitude of shoreline change increases with incident wave power and the degree of disequilibrium the latter disequilibrium term eq is expressed in terms of the time evolving equilibrium eq and instantaneous dimensionless fall velocities and dictates the direction of shoreline movement following wright et al 1985 the equilibrium fall velocity is defined as a function of the weighted antecedent conditions and is a proxy for the evolving beach state the decay rate of the weighting function used to compute eq is a model free parameter determined by calibration against measured data which physically reflects the degree of observed memory of the system the decay in amplitude of this weighting function with time is controlled by a memory decay term where the weighting reaches 10 1 and 0 1 at 2 and 3 days prior to the current calculation time the model is applied to two multi year 6 years data sets incorporating hourly wave and weekly shoreline measurements from two contrasting energetic sites in se australia the first is the relatively dissipative straight gold coast qld and the second is a more intermediate embayed beach at narrabeen nsw the model shows significant skill at hindcasting shoreline change at both sites predicting approximately 60 of the total shoreline variability the gold coast shoreline is dominated by a strong seasonal signal conversely at the narrabeen embayment shoreline variability and morphology is more dynamic responding at storm frequency evidence suggests that there is a strong coherence between the shoreline position and morphodynamic state and that both have response times characterised by it is hypothesised that optimised values in the shoreline model physically relate to the efficiency of sediment exchanges between the shoreface and offshore bars and the prevalence of one or two dimensional horizontal circulation the general success of this new shoreline model for hindcasting the observed shoreline behaviour at two distinctly different open coast sites suggests that this approach may be suitable for broader application

bedload and suspended load contributions to breaker bar morphodynamics abstract this study presents measurements of sheet flow processes grain sorting and bedload plus suspended load transport rates around a medium sand breaker bar in a large scale wave flume the results offer insights in effects of wave breaking on bedload and grain sorting processes and in the quantitative contributions by bedload and suspended transport to breaker bar morphodynamics sheet flow layer dynamics are highly similar to observations under non breaking waves revealing clear effects by velocity asymmetry but no evident effects by breaking generated turbulence bed slope or the cross shore non uniform flow the sheet flow layer thickness can be predicted using existing empirical formulations based on local hydrodynamic forcing at locations covering the shoaling region up to the bar crest the cross shore variation in bedload transport rates is explained by variations in wave shape i e velocity skewness and asymmetry at locations between bar crest and bar trough bedload transport rate magnitudes correlate positively with bed slope and turbulent kinetic energy bedload and suspended load transport rates are of similar magnitude but of opposite sign bedload transport is onshore directed and dominates in the shoaling zone but after wave breaking the offshore directed suspended sediment transport increases in magnitude and exceeds bedload transport rates in the breaking and inner surf zones bedload and suspended load transport contribute notably differently to bed profile evolution bedload transfers sand grains from the offshore slope to the bar crest and additionally leads to erosion of the shoreward bar slope and deposition at the bar trough while suspended load transport induces an opposite pattern of erosion at the bar trough and accretion at the bar crest grain size analysis of suspended sediment samples reveals size selective entrainment and vertical size segregation in the inner surf zone but suggest size indifferent entrainment and vertical mixing by energetic vortices in the breaking region size selective transport by bedload and suspended load leads to a cross shore coarsening of the bed from shoaling to inner surf zone with local additional sorting mechanisms around the breaker bar due to bed slope effects

breaker bar morphodynamics under erosive and accretive wave conditions in large scale experiments abstract differences between breaker bar evolution under high energy erosive and subsequent mild energy accretive wave conditions are studied based on three data sets from large scale morphodynamic experiments under erosive wave conditions a clear linear relationship between the height and the cross shore location of the breaker bar is observed the similar cross shore shape of the sediment transport magnitudes underlines the similarity of the bar evolution under erosive wave conditions under the subsequent accretive wave conditions two major evolution patterns are observed during onshore migration decaying or non decaying breaker bar in the presented data the feedback between the wave conditions and the beach morphology determines if a bar decays during onshore migration this feedback involves that the wave breaking location depends on the morphology and on the wave conditions resulting in differences in sediment transport patterns between the two types of onshore bar migration a comparison against numerous other experimental beach profile data sets strongly supports the linear relationship between bar height and bar location under erosive wave conditions for accretive wave conditions the number of comparable data sets is very limited the comparison underlines that breaker bar evolution under accretive wave conditions cannot be condensed to a single pattern as under erosive wave conditions

the behaviour of a multiple bar system in the nearshore zone of terschelling the netherlands 1965 1993 abstract the behaviour of a multiple bar system in the nearshore zone of the island of terschelling the netherlands is investigated on the time scale of years using a data set of soundings the data set covers the period from 1965 to 1993 the behaviour is analysed in terms of bar crest position and in terms of morphometric parameters such as bar crest depth height width and volume two or three breaker bars are permanently present in the study area each individual bar passes through three stages during its existence 1 generation close to the shore 2 seaward migration and 3 degeneration at the outer margin of the nearshore bar zone the key factor controlling the behaviour of the inner bars is the crest depth of the outer bar three different couplings between the behaviour of the individual bars have been observed 1 bar stage changes due to the degeneration of the outer bar 2 prevention of the transition of an inner bar from the first to the second stage caused by the appearance from alongshore of a new outer bar having a small crest depth and 3 difference in mean annual seaward migration rate caused by the possible presence of a more seaward positioned bar it is hypothesized that the crest depth of the outer bar governs the relative importance of processes inducing shoreward and seaward migration in the inner nearshore bar zone and therefore controls the behaviour of the nearshore bar zone on the time scale of years

oxygen hafnium neodymium isotope constraints on the origin of the talnakh ultramafic mafic intrusion norilsk province russia

nearshore placement of a sand dredged mound abstract as a part of the dredging operations and environmental research doer program movable bed physical model experiments were performed at the u s army engineer research and development centre s erdc large scale sediment transport facility lstf to investigate the fate and evaluate the benefits of nearshore placed dredged material the resulting bathymetry was measured with detailed surveys the migration of the mound was quantified and comprehensive observations of hydrodynamics were obtained the potential suitability of dredged material placement in the nearshore surf zone was demonstrated after 10 h of oblique wave attacks it has been shown that as the mound was located at the edge of the surf zone very likely wave breaking induced horizontal circulation may be dominant a downdrift accretion of the submerged beach was observed which is due to the transport of part of the sediment suspended by breakers at the mound and captured by the longshore currents the experiments provided useful validation data for numerical morphological models

geology and geochemistry of intrusions and flood basalts of the noril sk region ussr with implications for the origin of the ni cu ores geochemical studies indicate that five principal magma types characterize the 3 8 km vertical thickness of flood basalt of the noril9sk region from base to top these are 1 a fractionated type with alkalic affiliations ivakinsky and syverminsky 2 an ni rich suite including picritic basalt gudchichinsky 3 a primitive but ni depleted suite with fiat rare earth element ree profiles and also including picritic basalts tuklonsky 4 a light ree enriched crustally contaminated suite lower nadezhdinsky nd 1 above 4 there is a transitional suite upper nadezhdinsky nd 2 and morongovsky mr 1 and mr 2 which is overlain by the fifth type a second primitive suite without picrites mokulaevsky similar but not identical in its chemistry to the tuklonsky type this is followed by tuffs and basalts of the kharayelakhsky kumginsky and samoyedsky suites which are largely composed of similar uncontaminated tholeiitic magma the latter three suites have not been studied by us intrusions of the region fall into five main groups 1 alkalic intrusions 2 ti rich dolerite dikes 3 dolerite sills and dikes 4 differentiated bodies not related to ore junctions and 5 differentiated bodies related to ore junctions the ni cu ores are associated with ni and cr rich type 5 olivine rich intrusions with flat ree profiles that are geochemicaly similar to the mokulaevsky magma light ree enriched ni and cr poor olivine rich type 5 intrusions with uneconomic mineralization occur closely associated with the strongly mineralized variants and resemble geochemically the basalts transitional between the lower nadezhdinsky and upper morongovsky they are cut by the strongly mineralized bodies indicating that the latter are of late morongovsky to mokulaevsky age the mineralized intrusions are associated with about 1 5 to 1 10 of their mass in sulfides this is a factor of 25 to 50 more than could have been carried in solution and deposited by in situ liquation from the magma of these intrusions the platinum group element pge concentrations in the ores require that the sulfides giving rise to them equilibrated with 15 to 200 times more magma than is represented by the intrusions much of the ore is very massive and crosscuts the host intrusions the sequence of igneous activity and mineralization in the immediate vicinity of noril9sk and talnakh from the base of the nadezhdinsky upward is thus interpreted to be 1 extrusion of highly crustally contaminated ni and cu poor basalt 2 extrusion of a series of basalt flows each progressively less contaminated and less ni and cu depleted than the preceding one accompanied by intrusion of contaminated ni depleted magma with weak mineralization 3 extrusion of uncontaminated ni and cu rich basalt accompanied by intrusion of uncontaminated ni rich magma with strong mineralization followed very closely by introduction of associated massive ore and 4 continued extrusion of ni and cu rich basalt it is proposed that crustal contamination of the original ni and cu rich magma occurred at the top of a vertically extensive fault controlled magma chamber and caused segregation of immiscible sulfides with a low r factor these depleted this magma in chalcophile elements and settled deeper in the chamber as they settled they reacted with less contaminated magma scavenging additional chalcophile elements they finally came to rest near the base of the chamber to form a zone of sulfide and thus chalcophile element enriched magma eruption and in some instances intrusion of progressively stratigraphically lower less contaminated and thus less depleted layers in the chamber gave rise to the observed sequence of basalts and intrusions the answer to the strong enrichment in ni cu and pge associated with the ore bearing intrusions is that these metals came from the magma that is now represented by the depleted basalts

alongshore variability of the multiple barred coast of terschelling the netherlands abstract the alongshore variability of the behaviour of a multiple bar system in the nearshore zone along the barrier island of terschelling the netherlands is investigated using a bathymetric data set with an alongshore extent of 12 km sampled annually for 28 yr the spatial and temporal variability of bar behaviour is quantified in terms of bar crest position in relation to morphometric parameters such as bar depth height width and volume along the entire study area the bars were generated close to the shore migrated seaward and eventually degenerated at the outer margin of the nearshore the interannual migrational patterns of the nearshore sandbars are analysed in terms of time of residence migration rates and return periods within the life cycle of a bar the cross shore nearshore bar behaviour was found to vary alongshore for instance cross shore migration rates gradually increased from 35 to 70 m yr from one end of the study area to the other concurrently the duration of net seaward migration increased from 9 to 15 yr the return period and total life span of bars were however found to be alongshore uniform on the order of 10 12 yr and 22 yr respectively morphological characteristics of the nearshore bar zone such as slope and width also exhibit gradually alongshore varying patterns a strong causal association is established between nearshore slope and both bar migration rates and duration of net seaward migration it is hypothesised that alongshore increasing wave heights at the seaward end of the bar zone is coupled with a corresponding increase in nearshore slope the presence of an important updrift ebb tidal shoal is identified as key controlling factor in the variability of bar behaviour along the adjacent shoreline of terschelling

statistical analysis of coastal morphological data sets over seasonal to decadal time scales statistical analysis of long term morphological data on coastal sedimentary features provides important information on the processes governing these features and their evolution in space and time in this paper seasonal yearly and decadal i e long term behavior of coastal morphological features is derived from field data by using both simple and advanced statistical techniques the sedimentary features which we are especially focusing on are a nearshore bars and b large scale shoreline undulations for example longshore sand waves and nesses high quality bathymetric field data of regularly sampled cross shore profiles and shorelines were the basis of the available data sets at noordwijk beach the netherlands duck north carolina usa sylt germany lubiatowo poland and winterton uk additional data sets from argus video images see holman r a stanley j 2007 the history capabilities and future of argus coastal engineering special issue of the coastview project doi 10 1016 j coastaleng 2007 01 003 and aerial photographs were used to increase the temporal and spatial resolution of the data sets where possible the statistical methods applied include some linear and non linear techniques described by larson et al larson m capobianco m jansen h rozyfiski g southgate h n stive m wijnberg k m hulscher s 2003 analysis and modeling of field data on coastal morphological evolution over yearly and decadal time scales part 1 background and linear techniques journal of coastal research 19 4 760 775 and southgate et al southgate h n wijnberg k m larson m capobianco m jansen h 2003 analysis of field data of coastal morphological evolution over yearly to decadal timescales part 2 non linear techniques journal of coastal research 19 4 776 789 the methods proved to be useful for extracting characteristics of the coastal sedimentary features concerning length scales e g spacing and rhythmicity and temporal scales e g migration rates and evolutionary patterns however the success of the statistical analysis strongly depends on the total size of the data set characterized by the specific spatial coverage spatial resolution temporal resolution and overall length in time recent data sets from remote sensing video systems like argus often meet these requirements and are of major importance for the formulation of conceptual behavior models c 2007 elsevier b v all rights reserved less

noril sk talnakh cu ni pge deposits a revised tectonic model the noril sk mining district is located at the northwest margin of the tunguska basin in the centre of the 3 000 4 000 km siberian continental flood basalt cfb province this cfb province was formed at the permo triassic boundary from a superplume that ascended into the geometric centre of the laurasian continent which was surrounded by subducting slabs of oceanic crust we suggest that these slabs could have reached the core mantle boundary and they may have controlled the geometric focus of the superplume the resulting voluminous magma intruded and erupted in continental rifts and related extensive flood basalt events over a 2 4 ma period cu ni pge sulfide mineralization is found in olivine bearing differentiated mafic intrusions beneath the flood basalts at the northwestern margin of the siberian craton and also in the taimyr peninsula some 300 km east of a triple junction of continental rifts now buried beneath the mesozoic cenozoic sedimentary basin of western siberia the noril sk i and talnakh oktyabr sky deposits occur in the noril sk kharaelakh trough of the tunguska cfb basin the cu ni pge bearing mineralized intrusions are 2 3 km wide and 20 km long differentiated chonoliths previous studies suggested that parts of the magma remained in intermediate level crustal chambers where sulfide saturation and accumulation took place before emplacement the 5 7 km thick neoproterozoic to palaeozoic country rocks containing sedimentary cu mineralization and evaporites may have contributed additional metal and sulfur to this magma classic tectonomagmatic models for these deposits proposed that subvertical crustal faults such as the northeast trending noril sk kharaelakh fault were major trough parallel conduits providing access for magmas to the final chambers however geological maps of the noril sk region show that the noril sk kharaelakh fault offsets the mineralization which was deformed into folds and offset by related reverse faults indicating compressional deformation after mineralization in the late triassic to early jurassic in addition most of the intrusions are sills not dykes as should be expected if the vertical faults were major conduits a revised tectonic model for the noril sk region takes into account the fold structure and sill morphology of the dominant intrusions indicating a lateral rather than vertical emplacement direction for the magma into final chambers taking into account the fold structure of the country rocks the present distribution of the differentiated intrusions hosting the noril sk i and talnakh oktyabr sky deposits may represent the remnants of a single 60 km long deformed and eroded palm shaped cluster of mineralized intrusions which are perceived as separate intrusions at the present erosional level the original direction of sill emplacement may have been controlled by a northeast trending paleo rise which we suggest is present at the southeastern border of the noril sk kharaelakh trough based on analysis of the unconformity at the base of the cfb the mineralized intrusions extend along this rise which we interpret as a structure that formed above the extensionally tilted block in the metamorphic basement geophysical data indicate the presence of an intermediate magma chamber that could be linked with the talnakh intrusion in turn this t shaped flat chamber may link with the yenisei khatanga rift along the northwest trending pyasina transform fault which may have served as the principal magma conduit to the intermediate chamber it then produced the differentiated mineralized intrusions that melted through the evaporites with in situ precipitation of massive disseminated and copper sulfide ore the noril sk kharaelakh crustal fault may not relate to mineralization and possibly formed in response to late mesozoic spreading in the arctic ocean

sudoite a rock forming mineral in verrucano of the northern apennines italy and the sudoite chloritoid pyrophyllite assemblage in prograde metamorphism sudoite the di trioctahedral chlorite with ideal composition mg2al al2 si3al o10 oh 8 is a widespread rock forming mineral in meta siltstones and psammites of the verrucano sequence of the northern apennines sub ellipsoidal aggregates probably derived from muscovite clasts consisting of sudoite pyrophyllite and muscovite are common sudoite may also occur as thin blades in the rock matrix the co existence of sudoite ferich chloritoid and pyrophyllite reported here for the first time has been observed in specimens from the m argentario and monticiano roccastrada areas this three phase assemblage diagnostic of a specific metamorphic facies may be a tool for detailed zonation of low grade terranes

metamorphism of metasediments at the scale of an orogen a key to the tertiary geodynamic evolution of the alps major discoveries in metamorphic petrology as well as other geological disciplines have been made in the alps the regional distribution of late cretaceous tertiary metamorphic conditions documented in post hercynian metasediments across the entire alpine belt from corsica tuscany in the west to vienna in the east is presented in this paper in view of the uneven distribution of information we concentrate on type and grade of metamorphism and we elected to distinguish between metamorphic paths where either pressure and temperature peaked simultaneously or where the maximum temperature was reached at lower pressures after a significant temperature increase on the decompression path the results show which types of process caused the main metamorphic imprint a subduction process in the western alps a collision process in the central alps and complex metamorphic structures in the eastern alps owing to a complex geodynamic and metamorphic history involving the succession of the two types of process the western alps clearly show a relatively simple picture with an internal high pressure dominated part thrust over an external greenschist to low grade domain although both metamorphic domains are structurally very complex such a metamorphic pattern is generally produced by subduction followed by exhumation along a cool decompression path in contrast the central alps document conditions typical of subduction and partial accretion followed by an intensely evolved collision process often resulting in a heating event during the decompression path of the early subducted units subduction related relics and collisional decompressional heating phenomena in different tectonic edifices charac terize the tertiary evolution of the eastern alps the tuscan and corsica terrains show two differ ent kinds of evolution with corsica resembling the western alps whereas the metamorphic history in the tuscan domain is complex owing to the late evolution of the apennines this study confirms that careful analysis of the metamorphic evolution of metasediments at the scale of an entire orogen may change the geodynamic interpretation of mountain belts

the gyroscopic earth and its role in supercontinent and metallogenic cycles abstract compilation and analysis of the paleomagnetically constrained plate tectonic reconstructions for the last 2 5 ga of earth s history reveal that continental and oceanic hemispheres are principal and stable first order divisions on the earth with cyclical breakup and reassembly of the continental crust into supercontinents although the breakup of the supercontinent rodinia at 0 75 ga marked important reorganization of the plate tectonic pattern the movements of large continental masses both before and after the breakup of rodinia show remarkable synchronism albeit in significantly rearranged combinations the patterns with disassembled continents coincided with periods when substantially more than 50 of the continental masses occurred either in the northern during palaeoproterozoic and cenozoic times or southern during neoproterozoic to middle palaeozoic times hemispheres whereas the reassembled supercontinents were always symmetrically centred near the equator it is proposed that such regularity might be governed by a convection driven move of the continental fragments towards a pole after the breakup of the supercontinent followed by gyroscopic rebalancing or shift of all earth s solid shells e g entire mantle lithosphere towards the equator relative to the more stable oriented magnetic currents in the liquid core this process is somewhat similar to the true polar wander concept but it takes into account the spinning forces of the earth mantle convection is considered as an important force constantly driving the plates in the oceanic hemisphere and keeping the continental hemisphere intact the periods of gyroscopic rebalancing correspond to the reassembly of the supercontinents at 2 7 2 5 ga kenorland 2 0 0 75 ga columbia and its modification into rodinia and 0 32 0 18 ga pangaea the main reassembly mechanism in addition to rifting spreading and collision is large scale strike slip translation of not only relatively small lithotectonic terranes but also of major cratons these cycles govern changes from the dominantly extension to collision and plume related mineral deposit types in the internal orogens in the continental hemisphere whereas subduction related to collision related mineral deposit types remain persistent through the metallogenic cycles at the oceanic continental hemisphere transition zone just migrating oceanward in time

alpine thermal and structural evolution of the highest external crystalline massif the mont blanc 1 the alpine structural evolution of the mont blanc highest point of the alps 4810 m and of the surrounding area has been reexamined the mont blanc and the aiguilles rouges external crystalline massifs are windows of variscan basement within the penninic and helvetic nappes new structural 40ar 39ar and fission track data combined with a compilation of earlier p t estimates and geochronological data give constraints on the amount and timing of the mont blanc and aiguilles rouges massifs exhumation alpine exhumation of the aiguilles rouges was limited to the thickness of the overlying nappes 10 km while rocks now outcropping in the mont blanc have been exhumed from 15 to 20 km depth uplift of the two massifs started 22 myr ago probably above an incipient thrust the alpine sole thrust at 12 ma the ne sw trending mont blanc shear zone mbsz initiated it is a major steep reverse fault with a dextral component whose existence has been overlooked by most authors that brings the mont blanc above the aiguilles rouges total vertical throw on the mbsz is estimated to be between 4 and 8 km fission track data suggest that relative motion between the aiguilles rouges and the mont blanc stopped 4 myr ago since that time uplift of the mont blanc has mostly taken place along the mont blanc back thrust a steep north dipping fault bounding the southern flank of the range the european roof is located where the back thrust intersects the mbsz uplift of the mont blanc and aiguilles rouges occurred toward the end of motion on the helvetic basal decollement hbd at the base of the helvetic nappes but is coeval with the jura thin skinned belt northwestward thrusting and uplift of the external crystalline massifs above the alpine sole thrust deformed the overlying helvetic nappes and formed a backstop inducing the formation of the jura arc in that part of the external alps nw se shortening with minor dextral ne sw motions appears to have been continuous from 22 ma until at least 4 ma but may be still active today a sequential history of the alpine structural evolution of the units now outcropping nw of the pennine thrust is proposed

kinematic thermal and petrological model of the central alps lepontine metamorphism in the upper crust and eclogitisation of the lower crust abstract seismic and seismological studies as well as gravimetric models indicate that a slab of european lithospheric mantle and lower crust is currently underthrust below the apulian crust we assume a simple kinematic model in which the lower and upper subducted european crusts are decoupled along a decollement the lower crust goes into subduction without deformation the upper crust deforms by pure shear with a horizontal compressional axis the total erosional flux is adjusted to balance upper crust input so that the belt keeps the same geometry different distributions of erosion being used the computed temperature field is steady state if the kinematic model applies during a minimum time of 40 myr for a convergence rate of 8 mm yr equilibrium mineral assemblages and densities are determined from the computed p t conditions for a granodioritic chemical composition of the upper crust and an andesitic composition of the lower crust assuming local isostasy the density model fits the average topographic profile across the central alps the p t t paths obtained for the part of the upper crust initially at depths 10 to 16 km are compatible with the medium pressure oligocene metamorphism in the lepontine dome the peak calculated temperature for the deepest non subducted crustal rocks is 600 c for a pressure of 0 8 gpa near the lower limit of high pressure amphibolites we thus propose that the lepontine metamorphism corresponds to the steady state thermal regime however either faster erosion rates in the internal part of the belt or tectonic denudation are required for exhumation of the deeper portion of the belt the computed temperature field implies eclogitisation of the lower crust at a depth of 55 to 60 km we conclude that the moho limiting the deepest part of the root may correspond to the eclogitisation phase change lower crust eclogites have a density comparable to or higher than that of the mantle depending on their chemical composition 3 37 for andesitic eclogites 3 56 for gabbroic eclogites thus andesitic eclogites may stay in gravitational equilibrium in the mantle below the root whereas gabbroic eclogites are gravitationally unstable and should sink

synchrony and causal relations between permian triassic boundary crises and siberian flood volcanism the permian triassic boundary records the most severe mass extinctions in earth9s history siberian flood volcanism the most profuse known such subaerial event produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less analysis of 40 ar 39 ar data from two tuffs in southern china yielded a date of 250 0 0 2 million years ago for the permian triassic boundary which is comparable to the inception of main stage siberian flood volcanism at 250 0 0 3 million years ago volcanogenic sulfate aerosols and the dynamic effects of the siberian plume likely contributed to environmental extrema that led to the mass extinctions

linking mineral deposit models to quantitative risk analysis and decision making in exploration this paper describes a methodology of translating mineral deposit models into flexible probabilistic structures based on 1 extraction of ore components fluids metals and ligands from crustal or mantle sources or both 2 fluid or melt assisted transport of ore components from source to trap zones 3 formation of trap zones i e effective melt or fluid channels that can focus melt or fluid migration and accommodate large amounts of metal and 4 operation of the physicochemical processes that promote and sustain the deposition of metal from fluids or melts passing through a particular trap site our approach integrates these critical mineralization processes and conditions with concepts of probability theory decision analysis and financial modeling the principal objective is to make mineral deposit models amenable to financial risk and value analysis and suitable for communication of value creating geologic concepts to financial stakeholders in economic terms a case study based on an actual porphyry copper project illustrates how the resulting probabilistic mineral systems model can generate a measure of the probability of ore occurrence as an input for exploration decision trees and simulations to calculate the expected value of an exploration project and the probability distribution of all possible surrounding net present values npvs within a minimum and maximum range formulation of the probabilistic model closely follows and combines principles of the well established petroleum and mineral systems approaches and makes use of excel based model templates with decision tree and simulation add in software packages

permian carboniferous and permian triassic magmatism in the rift zone bordering the tethyan margin of southern pangea magma was emplaced in the india australia rift zone along the tethyan margin during permian carboniferous and permian triassic time permian carboniferous alkalic granite and basaltic and rhyolitic lava flows and tuffs formed at the same time as right lateral transtension of pangea as recorded by the magmatic rocks of neocratonic post variscan europe and post kanimblan eastern australia permian triassic tholeiitic basalt in india alkalic magmatic rocks in oman and rhyolite dolerite and undersaturated alkalic volcanic rocks in western australia preceded and accompanied the early opening of the neo tethys ocean coeval magmatism included the voluminous mid plate siberian traps the emeishan basalt of south china and the peak activity of the magmatic arc along the convergent panthalassan margin the background magmatism probably permitted the siberian traps to trigger the environmental catastrophe at the permian triassic boundary

the behaviour of nearshore bars on the time scale of years a conceptual model abstract soundings of the sandy dutch coast have demonstrated the presence of a multiple bar system that exhibits cyclic offshore directed migration on the time scale of years medium term a cycle comprises bar generation interannual offshore migration and decay in this paper we propose a conceptual model in which we qualitatively outline the relationships between short term hourly process knowledge waves currents sediment transport based on a 15 week data set of near bed hydrodynamics obtained in the multiple bar system of terschelling the netherlands and medium term bar behaviour the short term process knowledge is aggregated to the medium term by combining probabilistic characterisations of medium term wave conditions and sediment transports estimated from the short term field measurements essential to the conceptual model is the observed cross shore change in short term conditions that dominate medium term onshore and offshore sediment transport q on and q off respectively in the cross shore direction the conditions contributing most to q on change from predominantly breaking situations outside the bar zone to mainly non breaking conditions on the beach in contrast q off remains restricted to breaking conditions over the entire profile in the model we qualitatively describe how this cross shore change in the forcing conditions results in interannual offshore bar migration bar decay and the onset of the next cycle as such our model may serve as a first step towards a more coherent quantitative model on medium term periodic bar behaviour

suspended sediment transport around a large scale laboratory breaker bar this paper presents novel insights into suspended sediment concentrations and fluxes under a large scale laboratory plunging wave measurements of sediment concentrations and velocities were taken at 12 locations around an evolving breaker bar covering the complete breaking region from shoaling to inner surf zone with particular high resolution near the bed using an acoustic concentration and velocity profiler wave breaking evidently affects sediment pick up rates which increase by an order of magnitude from shoaling to breaking zone time averaged reference concentrations correlate poorly with periodic and time averaged near bed velocities but correlate significantly with near bed time averaged turbulent kinetic energy the net depth integrated suspended transport is offshore directed and primarily attributed to current related fluxes undertow at outer flow elevations i e above the wave bottom boundary layer the wave related suspended transport is onshore directed and is generally confined to the wave bottom boundary layer cross shore gradients of sediment fluxes are quantified to explain spatial patterns of sediment pick up and deposition and of cross shore sediment advection suspended particles travel back and forth between the breaking and shoaling zones following the orbital motion leading to local intra wave concentration changes at locations between the breaker bar crest and bar trough intra wave concentration changes are due to a combination of horizontal advection and of vertical exchange with the bedload layer sediment is entrained in the bar trough during the wave trough phase almost instantly advected offshore and deposited near the bar crest during the wave crest phase finally these results are used to suggest improvements for suspended sediment transport models

magma differentiation and mineralisation in the siberian continental flood basalts new major trace element and sr and nd isotope data are presented for selected lavas from the three uppermost formations in the siberian trap and on over 60 samples of the associated intrusive rocks the lavas from a 1400 m section are remarkably homogeneous and apart from four samples of basaltic andesites sio2 48 4 49 6 mgo 8 1 6 3 and mg 54 58 tio2 1 05 1 6 sr 1 7 and nd 3 8 1 3 there is no significant depletion in ni and cu or coupled increase in sio2 and la sm which so characterise the underlying nadezhdinsky formation rocks the intrusive rocks are considered in 5 groups following naldrett et al the alkaline rocks group 1 dolerites with a range of ti contents groups 2 and 3 and differentiated intrusions not associated with ore junctions group 4 all exhibit restricted initial sr and nd values of 3 32 and 3 5 to 3 2 respectively in contrast the intrusions related to ore junctions noril sk and lower talnakh types 5a and 5b trend towards higher sr and lower nd with sr 17 59 and nd 2 9 to 3 4 in the noril sk type and 41 66 and 3 7 to 6 2 respectively in the lower talnakh type the roles of crustal contamination and partial melting in the continental mantle lithosphere are briefly reviewed a minimum of three components are required to explain the basalt data which are therefore inconsistent with simple mixing between plume derived magmas and crustal material rather magmas were derived from both the mantle lithosphere and the underlying asthenosphere and crustal contamination modified the composition of specific magma types the minor and trace element characteristics of the contaminant appear to have been similar to those of an inferred deep seated crustal melt rather than an upper crustal melt or a bulk sediment the between suite variations in the intrusions are similar to those in the lavas but in addition there are within suite variations attributed to late stage open system differentiation within the noril sk and lower talnakh type intrusions in the preferred model in which sulphide precipitation occurred in response to the crustal contamination processes responsible for the elevated la sm and lower nd of the lower talnakh and nadezhdinsky rocks sulphide precipitation took place before the crystallization of the silicate phases currently preserved in the intrusive rocks

morphodynamics of slightly oblique nearshore bars and their relationship with the cycle of net offshore migration abstract while slightly oblique nearshore bars seem to be present on most barred beaches worldwide to date they have been poorly studied due to their great longshore extension that requires large spatial scale data sets here we give a detailed report of the morphology and multi annual dynamics of these bars using a large set of data lidar bathymetric profiles and aerial photographs on two barred beaches of the gulf of lions mediterranean sea france slightly oblique bars are characterized by a down drift longshore gradual increase of their distance from the shoreline over tens of kilometres forming an angle of 3 4 relative to the shore thus at any time the bar is in a different phase of the net offshore migration nom cycle according to its longshore extent alongshore a single bar is in the emergence phase of the cycle at its proximal end near the coast in the phase of seaward migration where it exhibits transition switching state from on to offshore position and finally in the decay phase at its distal end where its disappears on a multi annual timescale net offshore migration nom of slightly oblique bars results in an up drift displacement of the bar pattern with rates that can reach several metres per day thus a longshore time lag appears in the nom cycle when the bar is observed on separate cross shore bathymetric profiles a global worldwide inventory based on the literature shows that these bars are common to many barred beaches where nom cycles have been identified in almost all case there is a gradual down drift increase of distance of the bar from the shoreline however inter site comparison of environmental parameters does not allow us to determine the factors controlling the formation of slightly oblique bars the longshore displacement of the bars is directly related to the cross shore dynamics this study emphasizes the important role of slightly oblique bars in nearshore morphodynamics and the need to improve our knowledge of these features

a new petrogenetic grid for low grade metabasites abstract we have used internally consistent thermodynamic data to present calculated phase equilibria for the system na2o cao mgo al2o3 sio2 h2o ncmash in the range 0 500 c and 0 1 10 kbar involving the phases anorthite glaucophane grossular heulandite jadeite laumontite lawsonite paragonite prehnite pumpellyite stilbite tremolite wairakite zoisite with excess albite clinochlore quartz and pure water average activity terms derived from published mineral chemical data were included for clinochlore glaucophane prehnite pumpellyite tremolite and zoisite the new petrogenetic grid delineates stability fields and parageneses of common index minerals in zeolite prehniteactinolite prehnite pumpellyite pumpellyite actinolite blueschist and greenschist facies metabasites the stability fields of mineral assemblages containing prehnite pumpellyite epidote actinolite albite chlorite quartz were analysed in some detail using activity data calculated from five specific samples for example the prehnite actinolite facies covers a p t field ranging from about 220 to 320 c at pressures below 4 5 kbar the transition from the prehnite actinolite and pumpellyite actinolite to greenschist facies occurs at about 250 300 c at 1 3 kbar and at about 250 350 c at 3 8 kbar p t fields of individual facies overlap considerably due to variations in chemical composition

process based modeling of kilometer scale alongshore sandbar variability subtidal nearshore sandbars may exhibit cyclic net offshore migration during their multi annual lifetime along many sandy coasts although this type of behavior can extend continuously for several kilometers alongshore variations in cross shore bar position and bar amplitude are commonly observed alongshore variability is greatest when bars display km scale disruptions indicative of a distinct alongshore phase shift in the bar cycle an outer bar is then attached to an inner bar forming a phenomenon known as a bar switch here we investigate such large scale alongshore variability using a process based numerical profile model and observations at 24 transects along a 6 km section of the barred beach at noordwijk the netherlands when alongshore variability is limited the model predicts that the bars migrate offshore at approximately the same rate i e the bars remain in phase only under specific bar configurations with high wave energy levels is an increase in the alongshore variability predicted this suggests that cross shore processes may trigger a switch in the case of specific antecedent morphological configurations combined with storm conditions it is expected that three dimensional 3d flow patterns augment the alongshore variability in such instances in contrast to the observed bar behaviour predicted bar morphologies on either side of a switch remain in different phases even though the bars are occasionally located at a similar cross shore position in short the 1d model is not able to remove a bar switch this data model mismatch suggests that 3d flow patterns are key to the dissipation of bar switches

simulating cross shore material exchange at decadal scale theory and model component validation a model is developed to simulate the cross shore cs exchange of sand and the resulting profile response at decadal scale to be used in regional coastal evolution models the cs model consists of modules for calculating dune erosion and overwash wind blown sand transport and bar berm material exchange the sand transport equations included in these modules are formulated based on relevant physics in combination with empirical observations and then validated towards laboratory and field data in order to couple the transport equations to the evolution of key morphological features describing the profile a set of sand volume conservation equations are employed and solved together with the transport equations the features that are modeled include dune height from dune foot to crest the locations of the landward dune foot seaward dune foot berm crest and shoreline as well as the longshore bar volume the cs model is employed and tested at three different field sites in a companion paper palalane et al 2016 whereas in the present paper the properties of the model are demonstrated by simulating the evolution of the dune berm and shoreline in connection with accretion and erosion of sand in a groin compartment this case derives from a study at westhampton beach that focused on shortening the length of a number of groins in order to release accumulated sand in the groin field to eroding downdrift beaches

eocene high pressure metamorphism in the penninic units of the tauern window eastern alps evidence from 40 ar 39 ar dating and petrological investigations the40ar 39ar degassing spectra of white micas and amphiboles from three tectonic units of the central tauern window pennine basement and cover in the eastern alps have been measured white micas are classified as 1 pre alpine low si relic micas with an age value of 292 ma variously disturbed by the alpine metamorphism 2 alpine phengitic micas of variable composition with an age between 32 and 36 ma 3 alpine low si micas with a maximum age of 27 ma we attribute the higher alpine ages to a blueschist facies event whereas the lower age reflects the late cooling of the nappe pile blueschist facies phengites from the basement lower schieferhulle and the tectonic cover upper schieferhulle crystallized at a temperature below the closure temperature tc for argon diffusion in white mica and record ages of 32 to 36 ma at the same time a thin eclogite facies unit eclogite zone was thrust between the lower and the upper schieferhulle and cooled from eclogite facies conditions at about 600 c at 20 kbar to blueschist facies conditions at 450 c or even 300 c at 10 kbar eclogite facies phengites closed for argon diffusion and record cooling ages coinciding with the crystallization ages in the hanging and the footwall unit amphibole age spectra actinolite glaucophane barroisite are not interpretable in terms of geologically meaningful ages because of excess argon

diamond deposits of the siberian craton products of post 1200 ma plume events affecting the lithospheric keel abstract the siberian craton was affected by more voluminous plume events during last 1200 ma than any other craton on the earth these events produced many economically important deposits of which the tectonic setting of diamond deposits and related alkaline magmatism is analysed in this paper in space and time they can be grouped into several subprovinces meso to neoproterozoic yenisei sayan late devonian to early carboniferous vilyui permo triassic tunguska late jurassic olenek and late jurassic to early cretaceous aldan regardless of their age and subprovince affinity the alkaline intrusions including kimberlites preferentially occur within the archean granulite gneiss terranes forming a north south trending central horde framed by archean granite greenstone terranes these terranes in the basement of the siberian craton constitute tungus anabar and aldan domains of similar composition sinistrally offset for about 870 km despite such similarity diamond deposits are discovered to date only in the tungus anabar domain the seismic data show that the central horde in the tungus anabar domain has a lithospheric keel extending to a depth of greater than 250 km whereas it is absent in the aldan domain at the surface the central horde forms an uplift that controls lithofacies of riphean to cenozoic sedimentary basins in the siberian craton thus representing a long lived and relatively stable feature with storage of the diamonds in the subcontinental lithosphere at depth previous direct dating of diamonds from different siberian kimberlites indicated that they were formed in archean to paleoproterozoic times the reconstructions suggest that in meso to neoproterozoic times the siberian craton might have formed part of the supercontinents columbia and rodinia within them siberian craton was attached by its northern edge to the present western margin of the north american craton whereas the southern margin of siberia might have been facing a present northern margin of australia together they were part of a very long supercontinent and plotting of all presently globally known diamond deposits shows that they would all occur along its axis mapping its then possibly single lithospheric keel or a super horde after breakup of rodinia due to penetration of the spreading ridges between the australian and siberian cratons siberia was translated towards eastern europe for about 5000 km during 500 ma it was during this translation that it was periodically affected by neoproterozoic to mesozoic plumes which delivered the diamonds to the surface into all subprovinces except aldan

hydrous sulfide melting experimental evidence for the solubility of h2oin sulfide melts the effect of h 2 o on sulfide melting temperatures has been investigated in the fes pbs zns system at 1 5 gpa revealing that the addition of h 2 o results in a 35 c drop in melting temperature from 900 to 865 c in addition to the melting point depression the solubility of h 2 o is confirmed by the presence of vesicles in the quenched melt no oxide phases were present in any of the run products ruling out oxidation as a cause of the melting point depression confirmation of the solubility of h 2 o in sulfide melts is consistent with the recent suggestion by mungall and brenan 2003 of a magmatic origin for halogen rich alteration associated with magmatic sulfide ore deposits as the hydrous component of the alteration may similarly originate in the fractionating sulfide melt anatectic sulfide melts could be expected to contain more h 2 o than magmatic sulfide melts owing to the lack of a parental silicate melt that buffers the h 2 o content of magmatic sulfide melts fluids expelled from the cooling anatectic melts such as that present during granulite facies metamorphism of sulfide deposits at broken hill australia may have been responsible for associated retrograde hydrothermal alteration