early carbonate veining and gold mineralization in the timmins camp depositional context of the dome mine ankerite veins abstract the earliest auriferous veining event in the development of the over 16 moz gold endowment at the dome mine was an extensive set of ankerite veins over 5400 m strike length the depositional context of the dome mine ankerite veins has been historically contentious and their role in the mineralization history of the deposit not well understood we present a deposit wide geochemical study of the ankerite veins and their host rocks with observations from new underground mapping ankerite veining across the mine is almost exclusively restricted to the vipond formation which is fe rich and tholeiitic in nature metamorphic fluids and ankerite vein formation generally focused along flow boundaries in the volcanic sequence however carbonatization is ubiquitous the flows of the vipond formation maintain their protolith geochemical signatures as ree zr al2o3 tio2 and y are largely immobile during mineralization and alteration which mobilized na2o k2o and locally fe2o3 the ankerite vein structures are reactivated and overprinted by quartz and quartz tourmaline veining and gold grade is variable ranging from

geochemistry and nd isotope systematics of archaean granites of the eastern goldfields yilgarn craton australia implications for crustal growth processes abstract the archaean granites and granitic gneisses of the eastern goldfields in the yilgarn craton western australia can be divided into two major groups high ca and low ca and three minor groups high hfse high field strength elements mafic and syenitic the high ca group 68 77 sio 2 with high al 2 o 3 na 2 o and sr and low y shares many features with typical archaean tonalite trondhjemite suites but has higher k 2 o rb and th contents the low ca group 70 76 sio 2 differs from the high ca group in having lower al 2 o 3 cao and na 2 o but higher k 2 o rb th zr y la and ce contents granites of the high hfse mafic and syenitic groups form a minor component 10 20 of the eastern goldfields granites the siliceous 74 77 sio 2 high hfse granites are restricted to a narrow nnw trending zone and are characterised by high tio 2 total feo mgo y zr and ce but only moderate rb th and pb contents the a type syenites 50 68 sio 2 are distinguished by their high total alkalies and mainly occur along tectonic lineaments the mafic group 55 70 sio 2 is lithologically diverse and exhibits a wide range of k 2 o rb th la and ce contents granite emplacement occurred between 2 69 and 2 60 ga contemporaneous with or post dating greenstone formation nd values for the high ca mafic and syenitic groups are similar mostly 0 0 to 2 5 whereas those for the low ca group show a pronounced polarity from 4 5 in the west to 2 0 in the east nd depleted mantle model ages for the low ca granites range from 3 2 ga in the west to 2 75 ga in the east model ages for the high ca group 2 75 2 9 ga overlap with ages for inherited zircons from these granites the high ca granites appear to have been derived at high pressures by partial melting of a mafic to intermediate source subducted oceanic crust crustal underplate or thickened crust or remelting of an older tonalitic source derived by such a process if the high ca granites were largely crust derived then their extensive source rocks must have formed less than 250 ma prior to granite formation the low ca granites appear to be the products of crustal reworking probably from a tonalitic to granodioritic protolith that was progressively younger towards the east perhaps in the order of several hundred million years younger or involved an additional younger component the localisation of the crustally derived high hfse granites suggests either geochemical zonation of the crust or specific tectonic processes such as rifting the mafic granites and possibly the syenites imply a significant mantle contribution and new crustal growth although the extent is equivocal the crust of the eastern goldfields appears to have been generated by both lateral and vertical accretion over a significant period from or before 3 0 ga until the time of granite emplacement

seasonal changes in beach morphology along the sheltered coastline of perth western australia abstract seasonal change in beach morphology is traditionally ascribed to a variation in the incident wave energy level with calm conditions in summer resulting in wide beaches with pronounced subaerial berms and energetic conditions in winter causing narrow beaches with nearshore bar morphology the coastline of perth western australia is characterised by a large seasonal variation in the incident wave height and local beaches exhibit a distinct seasonal change in morphology however these morphological changes are better explained by a seasonal reversal in the littoral drift direction than by variations in the incident wave energy conditions in summer when northward sediment transport prevails due to sea breeze activity beaches located south of coastal structures headlands or rocky outcrops become wider due to the accumulation of sediment against the obstacle these beaches will subsequently erode in winter during storms when the longshore sediment transport is toward the south in contrast beaches located north of obstacles will become narrower during summer and wider during winter the usefulness of the dimensionless fall velocity h b w s t where hb is the breaker height ws is the sediment fall velocity and t is the wave period as a predictor of presence absence of bar morphology and beach type was investigated it was found that fluctuates around the threshold of bar formation 1 5 2 over a variety of time scales daily weekly and seasonally these temporal variations in in conjunction with the relatively low wave energy level that characterises the coast negates the development of beach and nearshore morphology that is in equilibrium with the hydrodynamic conditions as a result bar occurrence and beach type can not be readily predicted using along the perth coast

the timing of gold mineralization across the eastern yilgarn craton using u pb geochronology of hydrothermal phosphate minerals the highly mineralized eastern goldfields of the eastern yilgarn craton is an amalgamation of dominantly neoarchaean granitoid greenstone terranes and domains that record a history of early rifting followed by westward directed collision with initial arc formation collision and clastic basin formation and final accretion to the western yilgarn proto craton between 2 66 and 2 60 billion years ago the gold deposits that define this region as a world class gold province are the product of orogenic processes that operated during accretion late in the tectonic history after initial compressional deformation d1 d2 and the majority of granitoid magmatism minor gold was also deposited throughout the entire tectonic history in magmatic hydrothermal related systems however such mineralization mostly 0 3 g t gold is nowhere economic unless it overprints or is overprinted by much higher grade orogenic gold lodes robust shrimp u pb geochronology of gold related hydrothermal xenotime and monazite supports structural studies that gold mineralization occurred during late transpressional events d3 d4 shortly before cratonization however westward migration of collision and accretion produced a complementary diachroneity in the timing of gold mineralization of 5 to 20 m y between c 2 65 ma in the east including laverton district kurnalpi terrane to c 2 63 ma in the west including kalgoorlie terrane across the eastern part of the craton the robust geochronology refutes previous suggestions that significant gold mineralization events extended from de to d4 in the evolution of the orogen and that the kalgoorlie gold deposits formed over a period of 45 m y the crustal continuum model is applicable within terranes where orogenic gold depositional events were penecontemporaneous but must be modified to account for diachroneity of orogenic events and gold mineralization across the eastern goldfields

the largest au deposits in the st ives goldfield yilgarn craton western australia may be located in a major neoarchean volcano sedimentary depo centre the largest neoarchean gold deposits in the world class st ives goldfield western australia occur in an area known as the argo junction region e g junction argo and athena why this region is so well endowed with large deposits compared with other parts of the st ives goldfield is currently unclear because gold deposits at st ives are hosted by a variety of lithologic units and were formed during at least three different deformational events this paper presents an investigation into the stratigraphic architecture and evolution of the argo junction region to assess its implications for gold metallogenesis the results show that the region s stratigraphy may be subdivided into five regionally correlatable packages mafic lavas of the paringa basalt contemporaneously resedimented feldspar rich pyroclastic debris of the early black flag group coarse polymictic volcanic debris of the late black flag group thick piles of mafic lavas and sub volcanic sills of the athena basalt and condenser dolerite and the voluminous quartz rich sedimentary successions of the early merougil group in the argo junction region these units have an interpreted maximum thickness of at least 7 130 m and thus represent an unusually thick accumulation of the neoarchean volcano sedimentary successions it is postulated that major basin forming structures that were active during deposition and emplacement of the voluminous successions later acted as important conduits during mineralisation therefore a correlation exists between the location of the largest gold deposits in the st ives goldfield and the thickest parts of the stratigraphy recognition of this association has important implications for camp scale exploration

rip spacing and persistence on an embayed beach 1 four years of daily time exposure images from an embayed beach were examined to study the spacing persistence and location preferences of rips in a natural rip channel system a total of 5271 rip channels was observed on 782 days occurrence statistics showed no evidence of the preferred location pattern associated with standing edge waves trapped in an embayed beach the histogram of rip spacing the primary diagnostic observable for most models was well modeled by a lognormal distribution mean spacing of 178 m however spacings were highly longshore variable time mean of the standard deviation longshore mean of rip spacing was 39 so they are of questionable merit as a diagnostic variable storm driven resets to the longshore uniform condition required by most models occurred only four times per year on average making rip generation models relevant to only a small fraction of the system behavior rip spacings after the 15 observed reset events were uncorrelated with bar crest distance the lifetime of the 324 individual rip channel trajectories averaged 45 6 days rips were equally mobile in both longshore directions but the coefficient of variation of rip migration rates was large even for high migration rates the mean migration rate was well correlated to a proxy for the longshore current r2 of 0 78 thus there is no significant evidence that the formation spacing and migration of rip channels on this beach can be explained by currently existing simple models moreover the alongshore uniform initial conditions assumed by these models are rare on palm beach making the models generally inapplicable

an early thrust duplex in the kalgoorlie kambalda greenstone belt eastern goldfields province western australia abstract extensive regional mapping of the stratigraphic sequence throughout the kalgoorlie kambalda greenstone belt in western australia has outlined the geometry of early subhorizontal thrust faults these thrusts stacked and repeated the stratigraphy to form a major thrust duplex south of kambalda the roof thrust to the duplex becomes a major thrust flat to the north at kalgoorlie later transpressional deformation f2 upright folds d3 sinistral shear zones and folding has rotated and displaced the d1 thrusts both sub horizontal deformation and subsequent transpression indicate that compressional tectonics rather than vertical tectonics involving solid state granitoid diapirs were crucial in the development of this granite greenstone terrain

from intrusion related to orogenic mineralization the wasamac deposit abitibi greenstone belt canada abstract the wasamac deposit is an example of archean greenstone hosted gold deposit located in the abitibi belt 15 km southwest of rouyn noranda the deposit is hosted by a second order ductile shear zone of the cadillac larder lake fault zone cllfz known as the francoeur wasa shear zone fwsz it regionally sits at the boundary between the orogenic gold district of noranda and the kirkland lake gold district dominated by intrusion related gold systems this specific location in between two different gold mineralization environments sets the wasamac deposit apart as a prime candidate for investigating hydrothermal processes along the cllfz within the wasamac deposit gold distribution is constrained to the altered mylonitized portion of the fwsz lode systems are absent hydrothermal alteration and associated disseminated mineralization occurs as a replacement of the blake river group metavolcanic units the hydrothermal signature displays two distinct alkaline alteration assemblages potassic and albitic each associated with specific gold characteristics 1 potassic alteration is characterized by the crystallization of microcline carbonates and quartz within this assemblage gold is associated with porous pyrite enriched in te ag au mo pb bi w deposited under oxidizing conditions such characteristics are widely described in the kirkland lake area and are found in examples of syenite related mineralization such as the beattie and malartic gold deposits 2 the albitic alteration assemblage composed of albite sericite and carbonates reflects more reduced hydrothermal conditions with mineralization characterized by free native gold this hydrothermal event is coeval with the brecciation of early gold rich pyrite reflecting a structural overprint that controlled late stage gold characteristics these alteration and structural features are common in orogenic gold deposits both worldwide and regionally particularly at the neighbouring kerr addison and francoeur deposits and in lode gold systems such as in the sigma lamaque deposit the gold mineralization at wasamac has similar characteristics to both intrusion related gold systems and structurally controlled orogenic gold deposits hydrothermal and structural crosscutting relationships at wasamac indicate that a structurally controlled hydrothermal event overprinted earlier potassic magmatic hydrothermal alteration this observation supports a multistage process of gold concentration during which new gold characteristics metal anomalies fluid conditions and alteration assemblages replaced earlier stages of gold enrichment in places completely obliterating previous signatures we propose that the wasamac deposit was originally related to an alkaline intrusion buried at depth beneath the francoeur wasa shear zone

the southern oscillation index wave climate and beach rotation short embayed beaches bounded by headlands are a common feature along the southern and central coastline of new south wales australia many of these embayed beaches have experienced severe erosion at their southern end over the last decade previous studies have suggested that this erosion may be the result of an oscillatory medium term phenomenon known as beach rotation the present study was undertaken with the objectives of 1 establishing definitive links between the southern oscillation index soi wave climate and beach rotation and 2 determining the physical processes governing beach rotation data from two similar new south wales beaches were analysed using time series analysis techniques and image processing techniques using argus video images in this study the results indicate that the northern end of this type of beach accretes during el nino phases while the southern end erodes resulting in a net clockwise rotation of the beach the opposite occurs during la nina phases resulting in a net anti clockwise rotation of the beach the beach response at the northern and southern ends lags soi trend shifts by 3 and 17 months respectively waves are predominantly incident from the southeast during both el nino and la nina phases offshore wave height is positively correlated with the soi while offshore wave direction is negatively correlated with the soi on average the number of storms per year doubles from el nino to la nina based on these links between beach width fluctuations soi and incident wave conditions a conceptual model of beach rotation is presented the model describes the combinations of cross shore and longshore sediment transport and hydrodynamic processes that are expected to result in the observed clockwise and anti clockwise beach rotation during el nino and la nina phases respectively

temporal and spatial relationship between sediment grain size and beach profile abstract sediment samples and beach profile evolution data collected along one profile line at el puntal spit santander spain are used to analyze the spatial and temporal structure of the grain size distribution variability and its relationship with the beach profile changes standard principal component analysis pca and three way pca is applied to determine the temporal and spatial scales of variability of the data results indicate that the sediment grain size distribution varies markedly along the beach profile both spatially and temporally these variations are shown to be strongly related to morphological changes in the beach profile the spatial eigenvectors determined from the profile data and those from the sediment data exhibit similar patterns with their maxima and minima located at the same position since eigenvectors may be regarded as representative of uncorrelated modes of variability it is concluded that the spatial variability of both sediment and profile data are strongly related in particular it is shown that the location of the highest variability of grain size corresponds to that of the beach profile also different grain sizes are shown to exhibit a distinct degree of variability which leads to the conclusion that each sediment size responds to the same hydrodynamics differently the temporal eigenvectors determined from the profile and the sediment data shown a seasonal dependency however their maxima and minima are not located at the same position it is shown that this temporal shift is due to the different response of each sediment size to the hydrodynamics and in particular that the recovery of the profile starts with fine material from the bar it is inferred that models for beach profile evolution which do not take into account the sorting processes involved in the sediment transport cannot be fully succesful a master grain size sample constructed by adding all the grain samples taken over the profile is used to further examine the cross shore redistribution of the sediment the following working hypothesis is suggested for a beach profile within a physiographic unit the master grain size does not depend on time

daily morphological changes determined by high energy events on an embayed beach a qualitative model this paper examines the daily morphological responses of sununga beach an embayed beach located on the south eastern brazilian coast to storms in the south atlantic ocean the main mechanisms and timing of beach erosion and accretion the relationship between wave height and direction and beach volume changes are considered to establish a qualitative model for short term embayed beach morphological changes the methodology consisted of daily topographic surveys during the month of may in 2001 2002 and 2003 using an rtk gps real time kinematics global positioning system weather and wave model results were used to correlate hydrodynamics and beach morphology the results indicate that the morphodynamics of sununga beach are characterized by a process of beach rotation which occurred more or less clearly during all three surveys unlike what has been commonly described in the literature for longer time intervals and alternations of fair and stormy weather the beach rotation processes on sununga beach occurred under conditions of moderate to high wave energy change wave heights greater than 2 m an integrated evaluation of the behaviour of the meteorological aspects together with beach morphology enabled us to recognize that extra tropical cyclones were the most important agent in remobilizing the beach planform whether in beach rotation or in cross shore erosion copyright 2010 john wiley sons ltd

tectono stratigraphy of late archaean greenstone terranes in the southern eastern goldfields western australia abstract late archaean greenstone terranes in the southern part of the eastern goldfields are regionally extensive faultbounded entities defined on the basis of small but distinct differences in stratigraphy and structure the greenstones comprise volcano sedimentary successions that were all deposited at the same time c 2720 2675 ma on sialic crust hence the terranes are interpreted to represent contemporaneous probably adjacent basins these basins were affected by the same history of granite plutonism and regional deformation c 2675 2620 ma early subhorizontal deformation is poorly understood but includes at least locally significant thrust stacking d1 with a south to north movement direction this was followed by regional east west extension affecting all supracrustal successions above a province wide detachment now lying at depths between 4 and 7 km this detachment may have evolved from the greenstone basement contact but only after extensive reworking clastic basins developed along or above major extensional faults but no volcanism is associated with this extension subsequent east west d2 shortening resulted in regional scale thrusting folding and associated late stage transcurrent fault movements the d2 event is contemporaneous with a major thermal event represented by voluminous granite emplacement c 2660 ma and associated peak regional metamorphism in the greenstone succession predominantly monzo granite derived from older sialic crust was emplaced throughout the period of basin formation and deformation early synvolcanic granite c 2719 2710 ma is a minor component late synvolcanic granite c 2685 2675 ma is widespread and syn d2 granite c 2660 ma is abundant there are a few small late tectonic intrusions c 2640 ma to 2600 ma the lateral lithostratigraphic persistence of the contemporaneous basins the syn d2 low pressure regional metamorphism and the province wide monzo granite magmatism suggest that the greenstone basins possibly developed in a tectonic setting similar to that of failed rifts above aborted spreading centres the basins closed in response to far field compressional stresses

age constraints on recycled crustal and supracrustal sources of archaean metasedimentary sequences eastern goldfields province western australia evidence from shrimp zircon dating abstract shrimp u pb zircon dating of sedimentary volcanic and subvolcanic intrusive rocks from unconformity bounded sequences in the eastern goldfields province defines maximum depositional ages for those sequences the kambalda sequence which records a backarc basin was deposited prior to 2700 ma and from at least 2715 ma the spargoville sequence which records an arc adjacent volcano bound basin was deposited between 2700 and 2683 ma the kalgoorlie sequence which records an intra arc rift basin comprises two tectonic stages with depositional ages of 2681 2670 and 2661 2655 ma deposition of the spargoville and kalgoorlie sequences overlapped with the intrusion of granitoids and subvolcanic porphyries thereby indicating that those granitoids were emplaced during crustal extension younger submarine fan kurrawang sequence and braided fluvial merougil and jones creek sequences deposits of a remnant ocean basin were deposited at when coupled to palaeocurrent data provenance dating of detrital zircon suites fingerprints southeast oriented amalgamation of felsic detritus from multiple sources within longitudinal depositional systems and longitudinal reworking of felsic detritus from single sourced transverse systems most felsic detritus was recycled from coeval volcanoplutonic arcs and the orogen to the remnant ocean basin sequences with zircon ages ranging from 2730 to 2660 ma older felsic sources with age ranges of 3570 3130 3030 2900 2870 2770 and 2760 ma could have been structural enclaves within the volcanoplutonic arcs or orogen but were more likely within a distant cratonic basement when coupled with stratigraphic data it is concluded that detrital zircon age distributions preserve evidence for the sedimentary recycling of coeval volcanoplutonic arc or orogenic sources uplifted basin floor and dissected arc successions and cratonic basement virtually all source terrains have apparently vanished presumably through the combination of tectonic and sedimentary recycling and tectonic severance increased use of detrital zircon suites from archaean sedimentary sequences is advocated in order to quantify the balance between sedimentary recycling of felsic rocks from contemporaneous volcanoplutonic sources which themselves document crustal growth in arc environments and from relict volcanoplutonic and crustal basement sources which document the degree of crustal recycling

the invincible deposit early gold mineralisation truncated by unaltered c 2665 ma conglomerate st ives eastern goldfields western australia abstract two distinct styles of mineralisation are recognised at the invincible deposit with bedding parallel shear related gold mineralisation type 1 and shallow dipping mineralised extension veins type 2 the different styles of mineralisation reflect formation during two discrete deformation events type 1 mineralisation is hosted in laminated mudstone of the upper black flag group and mineralised quartz veins and breccia zones are distributed throughout the mudstone rather than being associated with a single shear mineralised zones are associated with intense sodic alteration the early mineralised structures are strongly modified by east west horizontal d2 3 compression in contrast type 2 extension veins are undeformed and are best developed in the massive sandstone conglomerate footwall but also overprint type 1 veins in the mudstone unit throughout the mine the early type 1 mineralisation is truncated by unaltered conglomerate of the c 2665 ma merougil formation a 10 20 difference in strike dip is commonly present and indicates that the main mineralising event at invincible occurred prior to erosion and deposition of the merougil formation the strong modification of the mineralisation by horizontal east west d2 3 compression is also consistent with formation early in the deformation history during the c 2672 2660 ma d1 event gold deposition in the egt was episodic occurring over a prolonged period during extension and compression bedding vein relationships indicate southwest side down kinematics during the early mineralising event in weakly mineralised zones sub vertical extension veins cut across beds that dip 70 to the southwest in strongly mineralised zones bedding is sub vertical and large quartz breccia veins develop along the bedding above moderately west dipping shears that extend across the steep bedding the location of the steep strongly mineralised zones where bedding is sub vertical reflects enhanced dilation in these zones during southwest side down movement southwest side down movement could represent extensional slip on the laminated mudstone beds if the bedding was tilted into a developing basin early merougil basin the location of the invincible system at the eastern edge of the merougil basin likely reflects an association with early basin controlling faults

structural geology across a proposed archaean terrane boundary in the eastern yilgarn craton western australia abstract the eastern goldfields province of the archaean yilgarn craton western australia can be divided into several nw se trending terranes with different stratigraphic signature at least two main phases of penetrative ductile deformation affect the terranes d1 is a phase of nappe type transport mainly to the north along gently dipping ductile shear zones it is interpreted as a phase of regional extension contemporaneous with intrusion of massive granitoid plutons and possibly contemporaneous with deposition of felsic volcanics and metasediments in the greenstone belts terrane boundaries were probably formed during d1 d2 gave rise to steep nw se to n s trending foliations and upright folds d2 is strongly partitioned over the area for strain and vorticity the pattern of partitioning seems to be dependent on the position of granitoid plutons which give rise to development of d2 strain shadows d1 structures have been preserved mainly in these strain shadows terrane boundaries are transected by boundaries of d2 structural domains minor intrusion of granitoids continued during and after d2 d1 is possibly associated with arrival of a mantle plume below the yilgarn craton and d2 may be a phase of regional shortening in a thinned lithosphere weakened by the thermal event

the granny smith gold deposit the role of heterogeneous stress distribution at an irregular granitoid contact in a greenschist facies terrane the granny smith gold deposits formed late in the structural history of the yilgarn block at a high crustal level in a largely brittle structural regime gold mineralisation is located along a n s striking fault which wraps around the contact of a small granitoid intrusion in different sections of the fault mineralisation may be developed in the granitoid in the adjacent sedimentary sequence and or along the contact between them in the granitoid gold mineralisation is in conjugate networks of thin carbonate quartz veins and their alteration halos small displacements along veins are common in contrast veins and faults in the sedimentary rocks are subparallel to bedding spatial variations in the conjugate vein orientations indicate that the local stress field was heterogeneous and controlled by the shape of the granitoid contact the greatest variations in vein and implied stress orientations occur in zones where the contact is most irregular these are also the areas of richest mineralisation fluid flow was thus focused in a regional scale low mean stress region created by the geometry of the granitoid intrusion its irregular contact caused deposit scale variations in fluid flow and resulted in heterogeneous gold grades along the contact zone

a video based technique for mapping intertidal beach bathymetry abstract measuring the location of the shoreline and monitoring foreshore changes through time are core tasks carried out by coastal engineers for a wide range of research monitoring and design applications with the advent of digital imaging technology shore based video systems provide continuous and automated data collection encompassing a much greater range of time and spatial scales than were previously possible using field survey methods a new video based technique is presented that utilises full colour image information which overcomes problems associated with previous grey scale methods which work well at steep reflective sites but are less successful at flatter dissipative sites identification of the shoreline feature is achieved by the automated clustering of sub aqueous and sub aerial pixels in hue saturation value hsv colour space and applying an objective discriminator function to define their boundary i e shoreline within a time series of consecutive geo referenced images the elevation corresponding to the detected shoreline features is calculated on the basis of concurrent tide and wave information which is incorporated in a model that combines the effects of wave set up and swash at both incident and infragravity frequencies validation of the technique is achieved by comparison with dgps survey results to assess the accuracy of the detection and elevation methods both separately and together the uncertainties associated with the two sub components of the model tend to compensate for each other the mean difference between image based and surveyed shoreline elevations was less than 15 cm along 85 of the 2 km study region which corresponded to an horizontal offset of 6 m the application of the intertidal bathymetry mapping technique in support of czm objectives is briefly illustrated at two sites in the netherlands and australia

directional ocean wave measurements in a coastal setting using a focused array imaging radar a unique focused array imaging doppler radar was used to measure directional spectra of ocean surface waves in a nearshore experiment performed on the north carolina outer banks radar images of the ocean surface s doppler velocity were used to generate two dimensional spectra of the radial component of the ocean surface velocity field these are compared to simultaneous in situ measurements made by a nearby array of submerged pressure sensors analysis of the resulting two dimensional spectra include comparisons of dominant wave lengths wave directions and wave energy accounting for relative differences in water depth at the measurement locations limited estimates of the two dimensional surface displacement spectrum are derived from the radar data the radar measurements are analagous to those of interferometric synthetic aperture radars insar and the equivalent insar parameters are shown the agreement between the remote and in situ measurements suggests that an imaging doppler radar is effective for these wave measurements at near grazing incidence angles

evidence for diachronous archean lode gold mineralization in the yilgarn craton western australia a shrimp u pb study of intrusive rocks the currently accepted model for the archean lode gold deposits of the yilgarn craton postulates that they represent a coherent group of epigenetic deposits the majority of which formed during a craton scale broadly synchronous hydrothermal event late in the tectonothermal evolution of the granite greenstone terranes at ca 2640 to 2630 ma felsic rocks from the southern eastern goldfields which host or are cut by gold mineralization have shrimp ii u pb zircon ages of 2673 or 3 ma at mount charlotte 2669 or 17 ma at mount percy 2663 or 3 ma at racetrack and 2657 or 8 ma at porphyry all these ages are consistent with gold mineralization at ca 2640 to 2630 ma intermediate to felsic dikes cut typical syn to postmetamorphic lode gold mineralization at the mount mcclure and jundee deposits in the yandal greenstone belt in the north of the kurnalpi terrane the dikes give ages of 2656 or 4 2663 or 4 and 2668 or 10 ma from mount mcclure and 2656 or 7 ma from jundee requiring that mineralization and peak regional metamorphism in the belt occurred prior to ca 2660 ma however both the characteristics of the jundee and mount mcclure deposits and the relative timing of mineralization with respect to the metamorphic and structural history of the belt are similar to that seen for gold deposits elsewhere in the yilgarn craton this implies that mineralization at jundee and mount mcclure was produced prior to 2660 ma by similar processes to those seen elsewhere in the yilgarn at 2640 to 2630 ma peak metamorphism in the western higher metamorphic grade terranes of the yilgarn was not reached until ca 2630 ma some 10 to 30 m y after peak metamorphism in the kalgoorlie terrane and more than 30 m y after metamorphism in the yandal belt in addition almost all of the published robust ages supporting gold mineralization at ca 2640 to 2630 ma are from the west of the craton consideration of the new data from the yandal belt in conjunction with previously published geochronology throws doubt on the hypothesis that lode gold mineralization occurred approximately synchronously across the yilgarn craton rather it suggests that mineralization along with regional metamorphism is earlier by at least 30 m y in the northeastern yilgarn craton

timing of deformation in the norseman wiluna belt yilgarn craton western australia establishing relative and absolute time frameworks for the sedimentary magmatic tectonic and gold mineralisation events in the norseman wiluna belt of the archean yilgarn craton of western australia has long been the main aim of research efforts recently published constraints on the timing of sedimentation and absolute granite ages have emphasized the shortcomings of the established rationale used for interpreting the timing of deformation events in this paper the assumptions underlying this rationale are scrutinized and it is shown that they are the source of significant misinterpretations a revised time chart for the deformation events of the belt is established the first shortening phase to affect the belt d1 was preceded by an extensional event d1e and accompanied by a change from volcanic dominated to plutonic dominated magmatism at approximately 2685 2675 ma later extension d2e controlled deposition of the ca 2655 ma kurrawang sequence and was followed by d2 a major shortening event which folded this sequence d2 must therefore have started after 2655 ma at least 20 ma later than previously thought and after the voluminous 2670 2655 ma high ca granite intrusion younger transcurrent deformation d3 d4 waned at around 2630 ma suggesting that the crustal shortening deformation cycle d2 d4 lasted approximately 20 30 ma contemporaneous with low volume 2650 2630 ma low ca granites and alkaline intrusions time constraints on gold deposits suggest a late mineralisation event between 2640 2630 ma thus d2 d4 deformation cycle and late felsic magmatism define a 20 30 ma long tectonothermal event which culminated with gold mineralisation the finding that d2 folding took place after voluminous high ca granite intrusion led to research into the role of competent bodies during folding by means of numerical models results suggest that buoyancy driven doming of pre tectonic competent bodies trigger growth of antiforms whereas non buoyant competent granite bodies trigger growth of synforms the conspicuous presence of pre folding granites in the cores of anticlines may be a result from active buoyancy doming during folding 2002 elsevier science b v all rights reserved

shoreline dynamics and beach rotation of artificial embayed beaches abstract artificially embayed beaches are an increasingly common environment in retreating and urban coasts the study of embayed beaches usually focuses on the concept of some equilibrium configuration of the shoreline caused by the wave approach and the location of protection structures but detailed studies of their shoreline dynamics are scarce the study reported herein monitored the shoreline dynamics of three artificial embayed beaches in barcelona city during a three year period using an argus video system to examine the behaviour of the emerged beach in order to assess the main factors affecting the shoreline and to analyze the processes causing beach rotation at different time scales the length and degree of protection of the three beaches were different and so were their morphological behaviours two of the beaches presented a general retreating trend with rapid abrupt displacements of the shoreline caused by oblique wave incidence during storm events and to the effects of beach nourishment after nourishment slower changes at the beaches determined beach evolution which was also influenced by the formation of long lasting megacusps the third beach the most protected one showed an accretionary trend no formation of megacusps and episodes of beach rotation related to the gradual recovery of the beach after storm events it is concluded that factors controlling the evolution of barcelona city beaches are associated with both natural processes and man induced actions resulting in a more complex pattern than would be expected for small embayed beaches beach rotation appears as a key process for understanding the morphodynamics of embayed beaches it occurs as a fast response to storms but also as a medium term adaptation of the shoreline configuration to morphological changes in the beach or to the recovery of a more stable orientation after storm events and man made changes in the beach orientation resulting from nourishment or sand relocation

shoreline variability via empirical orthogonal function analysis part ii relationship to nearshore conditions the method of empirical orthogonal function eof or principal component analysis pca was used to investigate the spatial and temporal variability of shoreline data sets from duck north carolina the gold coast australia and the united states pacific northwest in the present work an attempt is made to relate the individual modes of shoreline variability identified by the eof analyses to select parameterizations of the nearshore environment the parameters considered include the wave energy e the cross shore and longshore wave energy fluxes fx and fy the wave steepness ho lo the non dimensional fall velocity parameter the profile parameter p the surf similarity parameter and a surfzone froude number fr correlation analyses were used to evaluate the linear relationship between each of these parameters and the temporal eigenfunctions ck t associated with individual modes of shoreline change typically strong correlations were observed between longshore uniform modes and the monthly means of several of the nearshore parameters

empirical orthogonal function analysis of shoreline changes behind two different designs of detached breakwaters this paper compares the shoreline responses immediately shoreward of two adjacent schemes of segmented shore parallel rubble mound breakwaters undergoing the same forcing by waves and tides scheme one consists of four longer emergent breakwaters that have produced tidal tombolos in their lee scheme two consists of five shorter lower breakwaters that are submerged at higher tides with salients in the breakwater s lee empirical orthogonal function analysis was used to decompose a video derived shoreline dataset into the dominant modes of shoreline change for both schemes the two schemes showed similar modes of change the primary mode of change for both schemes was the cross shore growth and shrinking of the salients tombolos the secondary mode of change was the longshore movement of the salients tombolos for all modes of change the dominant length scale was dictated by the breakwater dimensions and locations a new manifestation of hydrodynamic parameters is introduced the cumulative integral of the de meaned parameters this parameterisation allowed for meaningful correlation of the temporal eof components with forcing parameters and identification of the important influence of the tide on observed morphodynamic change clear differences were observed between the shoreline responses measured in schemes one and two including differences in bay erosion accretion and the longshore translation of salients tombolos the beaches in scheme two showed behavioural patterns similar to unprotected beaches which were not observable in scheme one it is postulated that these differences are caused both by the different breakwater designs and by variation in longshore sediment supply

the world class wallaby gold deposit laverton western australia an orogenic style overprint on a magmatic hydrothermal magnetite calcite alteration pipe gold mineralisation at the wallaby gold deposit is hosted by a 1 200 m thick mafic conglomerate the conglomerate is intruded by an apparently comagmatic alkaline dyke suite displaying increasing fractionation through mafic monzonite monzonite syenite syenite porphyry to late stage carbonatite in the mine area a pipe shaped zone of actinolite magnetite epidote calcite amec alteration overprints the conglomerate gold mineralisation associated with dolomite albite quartz pyrite alteration is hosted in a series of sub horizontal structurally controlled zones that are largely confined within the magnetite rich pipe the deposit has a current ore reserve of 2 0 moz au and a total resource of 7 1 moz au

extension and gold mineralization in the archean kalgoorlie terrane yilgarn craton abstract this paper focuses on two extensional events affecting late archean crust of the kalgoorlie terrane in the eastern goldfields and which are associated with gold mineralization these events bracket the duration of the crustal shortening event known as the kalgoorlie orogen the early extension phase is preserved around the raeside batholith and gave rise to the earliest recognized structures d 1e this event is characterized by multi directional horizontal extension in contrast to unidirectional extension associated with core complexes extension uplifted the batholith in relation to the overlying greenstone sequence and produced recumbent folds gold including the large deposits at leonora was deposited in normal shear zones around the batholith we propose that extension triggered doming of gravitationally unstable granitic rocks buried under a greenschist sequence and amplified the growth of extensional nappes the late phase of extension is evident in a number of gold deposits in the kalgoorlie terrane this phase is characterized by a overprinting crustal shortening structures that suggests it is the latest structure in all localities b gently dipping foliation associated with recumbent folds which are dragged into moderately dipping normal shear zones c maximum stretching axis nw se or n s at high angles to the maximum shortening axis inferred from regional shortening phases of the kalgoorlie orogen and d hosting gold this phase records relaxation of the kalgoorlie orogen and the findings suggest that gold mineralization was not restricted to a single deformation phase but started before the kalgoorlie orogen and waned at the end of the orogeny

geochronological constraints on pre syn and postmineralization events at the world class cleo gold deposit eastern goldfields province western australia recent geological and geochronological studies have led to a reevaluation of whether or not the majority of the lode gold deposits of the yilgarn craton formed nearly synchronously during an archean craton wide hydrothermal event as previously proposed the majority of reliable data indicate that gold mineralization took place at ca 2640 to 2625 ma however recent work in the far north of the eastern goldfields province provides structural evidence for instances of earlier gold mineralization and geochronological data for interpreted postore rocks that are considerably older than 2640 ma the documentation of xenotime and monazite in association with ore minerals at the cleo deposit provides a valuable means of determining the absolute age of gold mineralization at the cleo deposit high grade western lodes veins crosscut the sunrise shear zone at a high angle with only centimeter scale offset given that the stratigraphic sequence indicates at least several hundred meters offset across the shear zone the minimal offset of the western lodes veins indicates that gold mineralization was late in the history of movement in the shear zone the absolute ages of pre syn and postmineralization elements in the mine stratigraphic succession have been determined using a variety of geochronological techniques fuchsite micas formed in the sunrise shear zone yield an 40ar 39ar isochron age of 2667 19 ma rhyodacite porphyry dikes postdate the formation of the shear zone but predate the main phase of gold mineralization dike intrusion is constrained to 2674 3 ma by shrimp ii u pb analysis of zircons from these dikes rhenium os analysis of molybdenite from quartz chalcopyrite molybdenite veins that crosscut the porphyry dikes gives an age of formation at 2663 11 ma consistent with their relationship to the porphyry dikes both the dikes and these veins are crosscut by gold bearing western lodes veins mutually crosscutting relationships with ore minerals indicate that microscopic xenotime and monazite grains were deposited during ore formation in the western lodes ore zones shrimp ii u pb analyses of xenotime and monazite grains indicate that western lodes mineralization took place at 2654 8 ma at least 9 m y after the intrusion of the porphyry dikes 95 confidence evidence for substantial temporal separation between intrusive activity and gold mineralization is recorded by other researchers for other deposits associated with granitic intrusions in the leonora laverton area phlogopitic micas from a lamprophyre that crosscuts the whole succession including the sunrise shear zone yield an ar ar plateau age of 2080 4 ma this study constrains the timing of multiple events at cleo including the main phase of gold mineralization during a relatively short span of time however in the context of the larger debate about the existence of a dominant 2640 to 2625 ma period of gold mineralization and the extent of a proposed widespread pre 2660 ma mineralization event in the yilgarn craton the data from cleo are equivocal the 2654 8 ma age for mineralization being significantly older than 2640 ma but not significantly pre 2660 ma even if the maximum possible age is accepted

the effects of tides on swash statistics on an intermediate beach 1 swash hydrodynamics were investigated on an intermediate beach using runup data obtained from video images under mild near constant offshore wave conditions the presence of a sandbar and the tidally controlled water depth over its crest determined whether most of the incoming waves broke before reaching the shoreline this forced a change in the pattern of wave energy dissipation across the surf zone between low and high tide which was reflected by changes to swash on time scales of a few hours significant runup height rs defined as 4 times the standard deviation of the waterline time series was found to vary by a factor of 2 between low tide when most of the waves were breaking over the sandbar rs hs 1 5 where hs is the offshore significant wave height and high tide when the waves were barely breaking rs hs 2 7 the increase in wave energy dissipation during low tide was also associated with changes in swash maxima distribution a decrease in mean swash period and increasing energy at infragravity frequencies bispectral analysis suggested that this infragravity modulation might have been connected with the presence of secondary waves

storm response and beach rotation on a gravel beach slapton sands u k abstract continuous argus video data and fortnightly measurements of subaerial morphology were obtained over a 3 year period from a steep macrotidal gravel beach on the southwest coast of the u k concurrent wave and water level data were also collected enabling the correlation of the observed morphological changes to the hydrodynamic forcing wave conditions are generally low h s 0 5 1 m but the beach is affected by frequent storm wave activity c 15 storms per year with h s 2 4 m with waves either approaching from the south swell waves or from the east wind waves an assessment of the three dimensional morphological response of the beach to the two typical storm types was carried out by analysing the impact of 27 storms that occurred from april 2007 to april 2009 southerly storms cause accretion of the supratidal zone and erosion of the intertidal zone and a significant loss in overall beach volume easterly storms on the other hand induce supratidal erosion and intertidal accretion and a significant gain in overall beach volume during the intervening calm periods a small supratidal berm is constructed and a modest gain in overall beach volume occurs wave modelling indicated that opposing longshore energy fluxes occur for the different storm types with a northerly energy flux during southerly storms and a southerly flux during easterly storms weekly shorelines derived from the argus images revealed that the northern end of the beach widened by c 30 m and the middle beach receded by c 40 m over a relatively brief period a few months the occurrence of this beach rotation event is attributed to a higher frequency of southerly storms and or a lower frequency of easterly storms over this period thus the development and stability of the beach on annual time scales depend on the relative contributions of the two storm types and their sequencing longshore sediment transport lst rates derived from the data on beach morphological change were compared with several littoral drift formulae previously applied to gravel beaches the cerc equation with a proportionality factor k between littoral drift rate i l and longshore wave energy flux p l of k 0 054 yielded the best results

the tectonic setting and evolution of the 2 7 ga kalgoorlie kurnalpi rift a world class archean gold province the yilgarn craton results from three major mantle input events at ca 3 0 2 9 2 8 and 2 7 ga that have interacted with 3 0 ga continental crust zircon geochronology and sm nd isotopic data subdivide the craton into an older yilgarn proto craton and the younger more primitive eastern goldfields superterrane egst formation of the kalgoorlie kurnalpi rift kkr within the egst was associated with the 2 7 ga event which exploited weakened crust at the eastern margin of the yilgarn proto craton where thick sequences of komatiite and basalt were erupted between ca 2710 and 2690 ma in the kalgoorlie terrane calc alkaline volcanism in the kurnalpi terrane began at ca 2730 ma and continued to ca 2690 ma overlapping rifting and plume related volcanism in the kalgoorlie terrane deposition of siliciclastic sedimentary rocks within basins at ca 2660 resulted from an intra orogenic extensional event and coincided with the transition from high ca to low ca granite magmatism and peak emplacement of intrusions with a metasomatised mantle source component most aspects of the kkr are satisfied by broadly coincident plume related magmatism in the kalgoorlie terrane and westward subduction to the east of the burtville terrane geochemical characteristics of 2730 2700 ma calc alkaline volcanism and 2685 2630 ma low sio2 and alkali rich intrusions support models for a continental margin subduction zone setting world class gold deposits formed in reactivated margins of the kkr which became flux zones for mantle derived magmas hydrothermal fluids and heat during 2675 2620 ma orogenesis the orogenic gold mineralisation can be subdivided into proximal intrusion related and distal source deposits

architecture and geodynamic evolution of the st ives goldfield eastern yilgarn craton western australia abstract a new structural evolution consisting of both extensional and contractional events has been defined for the st ives goldfield in the south central kalgoorlie terrane of the eastern yilgarn craton in western australia these events shaped the development of the fault architecture which controlled the location of the regional anticlines the magmatic centres and the deposition of the archaean greenstone successions the fundamental grain of the st ives goldfield is north northwest trending this trend is marked by faults which developed during d1 extension which was oriented east northeast west southwest across these faults we map major stratigraphic changes in the thickness and composition of units especially of the previously undivided black flag group volcaniclastic rocks the centre of the st ives goldfield is dominated by the kambalda anticline this north northwest trending regional fold was likely established early during the d1 extensional history and was fully established during subsequent east northeast oriented d2 contraction the regional anticline is an important architectural element because 1 magmatism and gold mineralising fluids were focussed into this domed region and 2 deformation was partitioned across the limbs and crest of this structure the d3 event involved regional uplift and extension resulting in the formation of late basins merougil conglomerate locally and the emplacement of granitoids sourced from a metasomatised mantle wedge mafic type porphyries the most significant gold event in terms of endowment occurred during d4b sinistral strike slip shearing and associated thrusting e g tramways and republican thrusts these thrusts were previously interpreted as the first contractional structures to deform the area d1 but are here reinterpreted as relatively late d4b in this d4b event the north northwest trending faults underwent sinistral strike slip shearing and were linked across the kambalda anticline by accommodation structures represented by generally east to east northeast trending thrusts reactivation of d1 transfer structures may have influenced the location of these later accommodation structures late stage mineralisation during d5 was the result of dextral strike slip brittle shearing

a thrust ramp model for gold mineralization at the archean trondhjemite hosted tarmoola deposit the importance of heterogeneous stress distributions around granitoid contacts the trondhjemite hosted tarmoola gold deposit is situated in the leonora district in the eastern goldfields province and is the largest granitoid hosted gold deposit in the yilgarn craton of western australia 100 t au the massive trondhjemite pluton intrudes a northwest striking shallowly northeast dipping supracrustal sequence that comprises greenschist facies metamorphosed basalt komatiite chloritic siltstones and a volcani clastic unit several east northeast striking quartz diorite dikes cut the trondhjemite and supracrustal sequence major ore zones 1 g t au occur 1 within the trondhjemite as discontinuous west northwest striking zones 2 along the steeply dipping eastern trondhjemite contact in the supracrustal and trondhjemite rocks and 3 subparallel to the shallowly dipping western trondhjemite margin in supracrustal rocks ore zones in the trondhjemite are controlled by west northwest striking steeply south west and northeast dipping conjugate quartz carbonate veins that contain minor pyrite chalcopyrite sphalerite galena gold and rare scheelite gold bearing veins in supracrustal rocks have a similar vein mineralogy and timing to that of the auriferous veins in trondhjemite deformation at tarmoola occurred during progressive regional east west directed shortening the first deformation event d 1 caused early barren isoclinally folded quartz carbonate veins and a pervasive foliation in supracrustal rock to be aligned subparallel to the steeply dipping eastern margin of the pluton during the gold mineralization event d 2 the trondhjemite pluton acted as a competent body within ductile supracrustal country rocks subhorizontal northwest southeast shortening caused auriferous conjugate veins in trondhjemite and the reactivation of the eastern contact and a preexisting subparallel foliation in the supracrustal rock the reverse movement of supracrustal rock along the sheared western trondhjemite contact caused the formation of west dipping gold bearing shear zones in the overlying supracrustal sequence the reactivation of the eastern trondhjemite contact caused the development of low mean stress zones adjacent to the contact hy drothermal ore fluids were focused into these regions to form ore zones the third deformation event d 3 produced brittle ductile shear zones quartz carbonate veins and brittle faults that offset lithological contacts and gold bearing veins

a shoreline evolution model considering the temporal variability of the beach profile sediment volume sediment gain loss abstract the prediction of shoreline variability along sandy coastlines is a valuable skill for a broad range of coastal engineering applications currently there are multiple proposals in the literature for equilibrium cross shore shoreline evolution models based on a constant equilibrium condition correlated with the shoreline position the aim of this paper is to present an extension of an existing equilibrium shoreline evolution model adding a rate of change component which in turn modifies the relationship between the equilibrium shoreline position and the incident wave energy as a function that advances or retreats over time the proposed model is applied to two study sites on the spanish coast on the one hand one and a half years of shoreline position data obtained from a video camera system at nova icaria beach catalonia are used to evaluate the shoreline evolution during a period of sediment contribution which is attributed to a sand bypass coming from bogatell beach on the other hand 16 years of shoreline position data acquired from beach profile surveys in campo poseidon huelva are used to reproduce the shoreline evolution taking into account the trend of sediment loss due to sediment drift alongshore the results obtained from both study sites using the proposed model show overall good performance the model successfully represents the general shoreline erosion accretion oscillations and the progressive trend of sediment gains or losses through the evolutionary relationship between the equilibrium shoreline position and the incident wave energy

character and regional implications of the sheared archaean granite greenstone contact near leonora western australia abstract the boundary between greenstone belt rocks and deformed domal bodies of granite and gneissic granite in the area west and northwest of leonora is marked by a wide zone of high strain within which the dominant fabric elements are parallel to the boundary the high strain zone is arcuate the granitic body is domal in form consistent sense of shear movement indicators show that the greenstones moved down relative to the granite rocks from a continuous core of 1 6 km drilled 4 km southeast of leonora exhibit mesoscale recumbent folding and ductile faulting the upper 900 m of core is characterised by recumbent flexural slip folds with half wavelengths up to 660 m separated by discrete shear zones below about 1200 m rock type and structural character change at this depth greenschistfacies rocks are juxtaposed against amphibolite facies rocks across a major ductile shear thermodynamic data give estimates of 370 c 2 1 kbar for greenschist and 610 c 5 6 kbar for amphibolite facies with high fluid pressures dominated by water in low grade rocks and co 2 in high grade ones several kilometres of section have therefore been lost across this zone the amphibolite hosts broad and narrow shear zones within which movement sense is consistently normal the structural and metamorphic data suggest that emplacement of the domal granitic and gneissic rocks was temporally linked with normal ductile shearing the regional structural setting and juxtaposition of high and low grade rocks across the shear zone with abrupt changes in temperature and fluid composition suggests that the domes were emplaced as uprising hot deep seated rock in a regional extensional tectonic environment comparable to the tectonic setting of metamorphic core complexes

geodynamics of the eastern yilgarn craton abstract over the last decade there have been significant advances in our understanding of the stratigraphy magmatism deformation metamorphism and timing of mineralisation in the eastern yilgarn craton eyc of western australia the integration of these disciplines has enabled a holistic review of the tectonic history of the eyc which favours a paraautochthonous tectonic model a significant advance has been the recognition of a 2810 ma rifting event off the eastern margin of the youanmi terrane which set up the north northwest trending architecture of the eyc rifting was followed by a 100 myr long phase of tectonic activity initiated by the establishment of a convergent margin at 2715 ma characterised by a west dipping subduction zone to the east of the eyc subduction was associated with the deposition of 2715 2670 ma volcanic stratigraphy and the emplacement of voluminous tonalite trondhjemite granodiorite magmatism which resulted in magmatic thickening of the crust volcanism was terminated by a 5 myr pulse of east northeast contraction followed by mid orogenic extension possibly linked to lithospheric and lower crustal delamination the lack of ultra high pressure metamorphism and the presence of high geothermal gradients preclude this contractional event from recording continent continent collision mid orogenic extension at 2665 ma resulted in the introduction of metasomatised mantle melts mafic granites and syenites deposition of siliciclastic basins which record metamorphic anticlockwise ptt paths and the start of significant economic gold mineralisation in the eyc high stretching factors and or delamination associated with this extension event resulted in significant heat input into the base of the crust which eventually led to the emplacement of low ca crustal melt granites and cratonisation of the eyc major gold mineralisation postdates mid orogenic extension and was associated with renewed compression transpression 2650 ma and the development of steep predominantly north northwest striking sinistral and later north to north northeast striking dextral strike slip faults during low ca granite emplacement

protracted and polyphased gold mineralisation in the agnew district yilgarn craton western australia abstract the archean orogenic gold deposits exhibits common characteristics including coeval emplacement age often proposed to be associated with a single late tectonic gold mineralisation event although valid for a large majority of deposits in the yilgarn craton this model does not account for certain atypical gold deposits in the world class agnew district yilgarn craton western australia structural and paragenetic relationships combined with a compilation of geochronology and multiple sulfur isotopes indicate that mineralisation developed during a two stage process involving different fluid sources the initial event dated at c 2660 ma is related to the onset of folding during kalgoorlie orogeny and presents characteristics compatible with magmatic intrusion related mineralisation a second mineralisation event dated at c 2630 ma presents a mineral and metal inventory typical to archean orogenic like gold mineralisation and developed at a later stage of the orogenesis measurements of 34s and 33s from spatially constrained samples from the two temporally distinct mineralising events further ascertain contrasting fluid compositions and or reservoirs combined with geochronological data obtained on the poly magmatic lawlers granitic complex we argue for a protracted ore forming process the first stage of mineralisation has a magmatic affinity and is followed by a second stage of mineralisation whereby au bearing hydrothermal solution incorporated an archean sedimentary sulfur reservoir we propose that the change in source reservoir for sulfur in hydrothermal fluids may reflect a regional change in tectonic regime from convergent to transcurrent motion allowing fluids to be first sourced from mantle derived magmas followed later by metamorphic fluids

the age of the kambalda greenstones resolved by ion microprobe implications for archaean dating methods abstract a chert horizon within the archaean basalt pile at kambalda western australia contains zircons from air fall tuffs erupted as the sediment was laid down ion microprobe analyses of these magmatic zircons constrain the long sought age of the kambalda lavas to 2692 4ma 2 and show that regional metamorphism and deformation of the greenstone pile occurred within 30 ma of deposition rare zircon xenocrysts are evidence of pre greenstone crust as old as 3450 ma exposed remnants of which are yet to be identified subsets of both the magmatic and xenocryst zircons show evidence of hitherto unsuspected low temperature u and or pb mobility in the proterozoic long after stabilisation of the craton the ion microprobe data unravel complexities of isotopic inheritance and alteration illustrating the hazards of using bulk or whole rock samples in archaean isotopic investigations identification of interflow cherts as a precisely dateable rock type opens the way to direct ion probe dating of mafic ultramafic piles and close numerical age control of the complex but ill exposed stratigraphic and structural relations in this richly mineralised greenstone belt

natural variability of shoreline position observations at three pocket beaches we investigated the variability of shoreline position of three adjacent pocket beaches at barcelona city nw mediterranean over a period of two years daily measurements of shoreline position were extracted from high resolution video images and used to determine shoreline variability using empirical orthogonal function analysis we determine two dominant modes of shoreline variability for all beaches analysed the mode that explains most of the variability around 70 describes the beach plan form rotation which primarily occurs at the seasonal scale the cross shore translation of the beach profile is described by the 2nd mode which explains around 30 both types of shoreline movement have been related to the previous nearshore conditions this relationship was explored standardizing the translation rotation of the shoreline and comparing it with time averages of the cross shore energy flux efcsh and the energy flux direction efd averages over 7 to 12 days of efcsh were significantly correlated to the translation movement plan form rotation was well described by 28 to 40 day averaging of efd comparing results from the three beaches we determined that the time required to average the previous wave conditions depends on the beach characteristics beach length and sediment grain size in such a way that the greater the length of the beach and its sediment grain size the slower its response

host rock and structural controls on the nature and timing of gold mineralization at the holloway mine abitibi subprovince ontario the holloway mine a mesothermal gold deposit is located within the western abitibi subprovince ontario mineralized zones that contain microscopic gold within pyrite are hosted by a sequence of metakomatiites mafic to felsic metavolcanic and metasedimentary rocks there were two mineralization events however the early one was the main event in terms of the amount of gold mineralization this event was associated with albitization silicification chloritization and sericitization in addition to pyritization the later mineralization is associated with sericitization and pyritization carbonate and sericite alterations are associated with both mineralizing events results of u pb zircon age dating of rocks within the sequence constrains the main mineralization event to 2672 ma ore lenses of the holloway deposit are enveloped by 080 striking steeply south dipping zones of intense deformation and fabric development within the porcupine destor deformation zone the shear zones are characterized by a strong foliation and locally an associated extension lineation the ore lenses are interpreted to represent lithons that were formed by boudinage of the more competent mineralized zones which are pervasively albitized analysis of geochemical data demonstrates that the ree th nb hf ti fe and al were largely immobile with respect to the albite quartz chlorite sericite and hematite alterations locally preserved textures such as abundant varioles and spherulites indicate that the host metavolcanics were relatively evolved rocks geochemical data show they have an iron enrichment trend typical of tholeiitic mafic to felsic suites and that they were derived through fractional crystallization of parent basalt because of their high fe mg ratios the rocks reacted with hydrothermal solutions carrying gold presumably as thio complexes to form pyrite which scavenged the gold

a reevaluation of coastal embayment rotation the dominance of cross shore versus alongshore sediment transport processes collaroy narrabeen beach southeast australia 1 over 30 years of wave and beach survey data at collaroy narrabeen beach in southeast australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross shore sediment exchange or shoreline rotations due to alongshore exchange between the beach s extremities offshore wave data are derived from both buoy measurements and era 40 reanalysis data eof analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability 60 of variability is an onshore offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end this mode is primarily associated with variability in wave energy storms which by the nature of the wave climate of this region chiefly occurs from the south southeast the secondary mode of shoreline variability 26 of variability is a rotational signal between either end of the beach which coincides with 24 of the offshore wave climate shifting between the south southeast and east as well as changes in the wave period and wave energy storms a distinct annual cycle is identified in this rotation signal it is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross shore sediment exchange processes

shoreline variability via empirical orthogonal function analysis part i temporal and spatial characteristics empirical orthogonal functions eofs or principal components were used to extract the significant modes of shoreline variability from several data sets collected at three very different locations although eofs have proven to be a valuable tool in the analysis of nearshore data most applications have focused on the ability of the technique to describe cross shore or profile variability here however eofs were used to help identify the dominant modes of longshore shoreline variability at duck north carolina the gold coast australia and at several locations within the columbia river littoral cell in the u s pacific northwest in part one of this analysis characteristic patterns of shoreline variability identified by the eof analysis are described in detail at each site the dominant modes consisting of the first four eigenfunctions were found to describe nearly 95 of the total shoreline variability at both duck and the gold coast several interesting longshore periodic features suggestive of sand waves were identified while boundary effects related to natural headlands and navigational structures entrances dominated the pacific northwest data sets

modes and emergent time scales of embayed beach dynamics in this study we use a simple numerical model the coastline evolution model to explore alongshore transport driven shoreline dynamics within generalized embayed beaches neglecting cross shore effects using principal component analysis pca we identify two primary orthogonal modes of shoreline behavior that describe shoreline variation about its unchanging mean position the rotation mode which has been previously identified and describes changes in the mean shoreline orientation and a newly identified breathing mode which represents changes in shoreline curvature wavelet analysis of the pca mode time series reveals characteristic time scales of these modes typically years to decades that emerge within even a statistically constant white noise wave climate without changes in external forcing suggesting that these time scales can arise from internal system dynamics the time scales of both modes increase linearly with shoreface depth suggesting that the embayed beach sediment transport dynamics exhibit a diffusive scaling

dynamics of single barred embayed beaches abstract the dynamics of single submerged sandbars of two artificial embayed beaches la barceloneta and bogatell barcelona nw mediterranean has been studied with a video recorded data set of 4 3 years the alongshore averaged cross shore migration the orientation with respect the shoreline and the sinuosity of the barlines have been analyzed and related to wave conditions alongshore sediment transport and shoreline variability in general the submerged bars follow the general cyclic morphological behaviour observed in natural beaches switching among the four intermediate morphodynamic states but the studied beaches can be arrested during long periods of low wave conditions the dominant up state transition in barcelona beaches during storms is the transition toward the rhythmic bar and beach state the complete morphodynamic reset longshore bar and trough state only occurring during extreme wave events the cross shore migration of bars is dominated by the weekly and interannual components the interannual component shows an onshore bar migration trend at both beaches in contrast with the net offshore migration observed in multibarred open beaches bar disposition is located progressively seaward in the dominant alongshore transport direction i e oblique with respect to the shoreline at la barceloneta beach shoreline and barline orientations change consistently and a significant correlation between the accumulated alongshore sediment transport and the associated change in bar orientation has been found suggesting that alongshore transport can play a significant role in barline orientation finally bar sinuosity increases during eastern storms in both beaches this indicates that the formation of crescentic bars occurs for approximately shore normal waves some of the differences observed in bar morphology and mobility in the two studied beaches are related to their different level of protection with respect to the incident waves beach indentation

the timmins porcupine gold camp ontario anatomy of an archean greenstone belt and ontogeny of gold mineralization new structural and geochronological data and interpretations from the timmins porcupine gold camp abitibi subprovince more precisely define the stratigraphy and the generation timing and effects of deformation tisdale basalts and porcupine volcaniclastic and turbiditic sedimentary rocks assemblage rocks exhibit three major foliations s2 s3 s4 plus a late constrictional fabric of which s3 and s4 are also present in younger timiskaming assemblage sedimentary rocks pre timiskaming folding has long been recognized in tisdale assemblage rocks but no foliation had previously been attributed to such an event d1 regional uplift and extension produced a low angle unconformity between the tisdale and porcupine assemblages with partial excision of upper tisdale stratigraphy and perhaps of the blake river assemblage d2 involved imbrication of a set of south over north thrust sheets rooted in the porcupine destor deformation zone d3 en echelon folds along the northern flank of the porcupine destor deformation zone are a result of left lateral strike slip along this zone the timiskaming basin lying along the curvilinear trace of the porcupine destor deformation zone formed as a d3 transtensional half graben and the dome fault formed its faulted margin s4 foliation formed during subsequent right lateral strike slip movement and folding of s3 foliation intense d5 constrictional strain deformed earlier lineations as the previously dilatational jog that hosts timiskaming assemblage rocks acted as a compressional jog during right lateral movement along the porcupine destor deformation zone these d2 to d5 phases represent an overall thrusting strike slip transpressional regime there were several phases of gold mineralization in the timmins porcupine gold camp clasts of ankerite veins occur in timiskaming assemblage conglomerate at the dome mine and d3 foliation and folds crosscut early ankerite veining and alteration and some quartz veining thus low grade mineralization and possibly the quartz fuchsite veins predate timiskaming sedimentation however the bulk of gold postdates timiskaming sedimentation quartz carbonate tourmaline gold veins hollinger mcintyre hoyle pond dome aunor delnite mines formed within timiskaming assemblage and tisdale assemblage rocks these gold deposits developed largely as oblique slip and extensional vein arrays formed during north south shortening and local strike slip faulting younger deposits pamour are associated with d4 dip slip faulting and were weakly deformed during late d4 thus the largest known archean lode gold camp formed throughout protracted orogenesis consisting of a broadly transpressional regime with unusually well developed early thrusting

estimation of wave phase speed and nearshore bathymetry from video imagery a new remote sensing technique based on video image processing has been developed for the estimation of nearshore bathymetry the shoreward propagation of waves is measured using pixel intensity time series collected at a cross shore array of locations using remotely operated video cameras the incident band is identified and the cross spectral matrix is calculated for this band the cross shore component of wavenumber is found as the gradient in phase of the first complex empirical orthogonal function of this matrix water depth is then inferred from linear wave theory s dispersion relationship full bathymetry maps may be measured by collecting data in a large array composed of both cross shore and longshore lines data are collected hourly throughout the day and a stable daily estimate of bathymetry is calculated from the median of the hourly estimates the technique was tested using 30 days of hourly data collected at the sandyduck experiment in duck north carolina in october 1997 errors calculated as the difference between estimated depth and ground truth data show a mean bias of 35 cm rms error 91 cm expressed as a fraction of the true water depth the mean percent error was 13 rms error 34 excluding the region of known wave nonlinearities over the bar crest the accuracy of the technique improved and the mean rms error was 20 cm 75 cm additionally under low amplitude swells wave height h 1 m the performance of the technique across the entire profile improved to 6 29 of the true water depth with a mean rms error of 12 cm 71 cm

observations of nearshore crescentic sandbars 1 the temporal and spatial variability of crescentic sandbars is analyzed with hourly long term months video observations collected at four barred sites and are qualitatively compared to the temporal and spatial variability predicted by hypotheses underpinning existing approaches and models for crescentic bar formation edge wave template model linear stability analysis and nonlinear models the observations coming from the single barred beaches at duck north carolina usa and miyazaki kyushu japan and from the double barred beaches at the northern gold coast queensland australia and noordwijk netherlands show that crescentic sandbar wavelength and amplitude variations over space and time are very common for instance at any moment in time the wavelength of the smallest and longest crescentic bar can differ by a factor of 2 temporal changes in wavelength and amplitude result from merging and splitting of individual crescents causing the final configuration of a crescentic sandbar system to be very different from the initial configuration the gold coast data indicate that these intrinsically nonlinear interactions are an attempt of the crescentic bar system to self organize into a more uniform pattern as splitting is usually confined to the longest crescentic bar observed whereas merging usually combines the smallest crescentic bars into a longer bar the observed spatial and temporal crescentic bar behavior contrasts qualitatively with behavior predicted from the edge wave template model and implies that the predictive skill of linear stability models is limited nonlinear models are potentially better suited for a comparison against these field observations several suggestions to improve these models and hence to facilitate a data model comparison are made

multistage gold mineralization at the lapa mine abitibi subprovince insights into auriferous hydrothermal and metasomatic processes in the cadillac larder lake fault zone the lapa gold deposit contains reserves of 2 4 mt at 6 5 g t au and is one of the few deposits located directly within the cadillac larder lake fault zone cllfz a first order crustal scale fault that separates the archean abitibi subprovince from the pontiac subprovince to the south gold mineralization is predominantly hosted in highly strained and altered upper greenschist lower amphibolite facies mafic to ultramafic rocks of the piche group auriferous ore zones consist of finely disseminated auriferous arsenopyrite pyrrhotite pyrite and native gold disseminated in biotite and carbonate altered wall rocks native gold which is also present in quartz dolomite calcite veinlets is locally associated with sb bearing minerals especially at depth 1 km from surface where the deposit is characterized by a au sb as association at vertical depth greater than 1 km gold is associated with arsenopyrite and pyrrhotite au as association the mineralogy and paragenesis of the lapa deposit metamorphosed ore and alteration assemblages record the superposition of three metamorphic episodes m1 m2 and m3 and three gold mineralizing events spatial association between biotitized wall rocks and auriferous arsenopyrite indicates that arsenopyrite precipitation is concomitant with potassic alteration the predominant au as association recognized across the deposit is related to gold in solid solution in arsenopyrite as part of a pre m2 low grade auriferous hydrothermal event however the occurrence of hornblende oligoclase porphyroblasts overprinting the biotite alteration and the presence of porous clusters and porphyroblasts of arsenopyrite with native gold and pyrrhotite indicate an auriferous metasomatic event associated with peak m2 prograde metamorphism late retrograde metamorphism m3 overprints the hornblende oligoclase m2 assemblage within the host rocks proximal to ore by an actinolite albite assemblage by precipitation of free gold and sb sulfosalts at lower p t the complex relationships between ore structural features and metamorphic assemblages at lapa are related to the tectonometamorphic evolution of the cadillac larder lake fault zone at different times and crustal levels and varying heat and fluid flow regimes the lapa deposit demonstrates that early low grade gold mineralization within the cadillac larder lake fault zone has benefited from late gold enrichment s during prograde and retrograde metamorphism suggesting that multi stage processes may be important to form gold rich orogenic deposits in first order crustal scale structures

validation of volume continuity method for estimation of cross shore swash flow velocity the use of flow volume continuity to estimate depth averaged cross shore swash flow velocity is validated using appropriate field data swash surface and beach face elevation were measured by a network of ultrasonic altimeters mounted through the swash zone of a sandy beach estimates of cross shore flow velocity derived from these data compare well with concurrent measurements obtained from a vertical array of four electromagnetic current meters emcms significantly the continuity technique allows swash velocity to be estimated throughout the full swash cycle this is not possible using fixed current meters and the new measurements indicate that swash velocity is more negatively skewed than previously observed

orogenic gold common or evolving fluid and metal sources through time abstract orogenic gold deposits of all ages from paleoarchean to tertiary show consistency in chemical composition they are the products of aqueous carbonic fluids with typically 5 20 mol co 2 although unmixing during extreme pressure fluctuation can lead to entrapment of much more co 2 rich fluid inclusions in some cases ore fluids are typically characterized by significant concentrations of ch 4 and or n 2 common estimates of 0 01 0 36 mol h 2 s a near neutral ph of 5 5 and salinities of 3 7 wt nacl equiv with na k ca mg this fluid composition consistency favors an ore fluid produced from a single source area and rules out mixing of fluids from multiple sources as significant in orogenic gold formation nevertheless there are broad ranges in more robust fluid inclusion trapping temperatures and pressures between deposits that support a model where this specific fluid may deposit ore over a broad window of upper to middle crustal depths much of the reported isotopic and noble gas data is inconsistent between deposits leading to the common equivocal interpretations from studies that have attempted to define fluid and metal source areas for various orogenic gold provinces fluid stable isotope values are commonly characterized by the following ranges 1 18 o for precambrian ores of 6 to 11 and for phanerozoic ores of 7 to 13 2 d and 34 s values that are extremely variable 3 13 c values that range from 11 to 2 and 4 15 n of 10 to 24 for the neoarchean 6 5 to 12 for the paleoproterozoic and 1 5 to 10 for the phanerozoic secular variations in large scale earth processes appear to best explain some of the broad ranges in the o s and n data fluid rock interaction particularly in ore trap areas may cause important local shifts in the o s and c ratios the extreme variations in d mainly reflect measurements of hydrogen isotopes by bulk extraction of waters from numerous fluid inclusion generations many which are not related to ore formation radiogenic isotopes such as those of pb sr nd sm and os measured on hydrothermal minerals are even more difficult to interpret for defining metal source particularly as the low salinity ore fluids transport limited amounts of these elements and significant amounts of these may be locally added to the minerals during alteration reactions at the sites of gold deposition noble gas and halogen data are equally equivocal fluid exsolution from granitoids emplaced into the upper and middle crust metamorphism of the crust or fluids entering trans crustal fault zones from below the crust all remain as permissive scenarios associated with orogenic gold formation as the abundant geochemical data are equivocal however geological and geochronological data weigh heavily against a magmatic hydrothermal model in the upper to middle crust there is no universal temporal association between orogenic gold and magmatism and where there is an overlap in age there is no specific type of magmatism consistently associated with gold formation nor element zonation around any specific pluton a crustal metamorphic model for fluid and metal sources is very consistent with geological geochronological and geochemical data although metamorphism on a regional scale that releases these components into major fault zones can be associated with many processes along active continental margins these can include crustal thickening and radiogenic heating slab rollback and heating during crustal extension or subduction of a spreading ridge heating the base of an accretionary prism in rare examples where phanerozoic orogenic gold deposits are hosted in precambrian high grade metamorphic terranes fluids and metals must however enter a transcrustal fault system from a sub crustal source this could either be a devolatilized subducted relatively flat perhaps stalled slab and its overlying sediment or the corner of the fertilized mantle wedge that releases a fluid during a thermal event

synvolcanic and syntectonic gold mineralization at the bousquet mine abitibi greenstone belt quebec the bousquet pyrite gold deposit consisting of disseminated and vein type mineralization in sheared and altered greenschist facies archean volcanic rocks is hosted by two vein sets foliation parallel veins in ore zone 3 and foliation oblique veins in zones 1 2 4 and 5 foliation parallel veins are composed of pyrite and lesser amounts of chalcopyrite sphalerite pyrrhotite arsenopyrite galena bornite rutile tellurides and native gold the foliation oblique veins of zones 1 and 2 are composed of pyrite chalcopyrite and sphalerite with subordinate amounts of pyrrhotite arsenopyrite galena stannite gudmundite rutile ilmenite and gold quartz and muscovite are the principal gangue minerals in both vein types in ore zones 1 2 and 3 in zone 4 foliation oblique veins are composed of pyrite magnetite pyrrhotite and minor amounts of chalcopyrite and gold the gangue minerals are calcite ankerite white mica chlorite and tourmaline the veins of zone 5 contain pyrite chalcopyrite sphalerite bornite magnetite rutile and gold in a gangue of quartz carbonate white mica and chlorite disseminated auriferous pyrite occurs in zones 3 and 5 mineralogical and textural features indicate that gold emplacement and associated alteration occurred during two events one predating peak regional metamorphism and another postdating peak metamorphism early premetamorphic mineralization and related synvolcanic hy drothermal alteration produced initial auriferous sulfides and an advanced argillic alteration subsequent deformation recrystallization and metamorphic remobilization of early sulfides resulted in the currently observed structurally controlled vein type gold deposits the vol canogenic event is suggested by highly aluminous rocks closely associated spatially with the mineralized zones by textures preserved through the overprint of metamorphic textures and by the occurrence of stannite in ore zones 1 and 2 the late postmetamorphic gold mineralization is considered to be contemporaneous with retrograde alteration of metamorphic minerals formed during late deformation this alteration produced a pervasive kaolinite pyrophyllite diaspore gangue mineral assemblage involving the replacement of syntectonic andalusite porphyroblasts in felsic rocks in mafic host rocks retrograde alteration is characterized by carbonate chlorite muscovite pyrite and gold the formation of a white mica diaspore carbonate chlorite assemblage and the emplacement of associated gold are interpreted as epigenetic metamorphic events because these late retrograde minerals overprint the greenschist facies mineral assemblage

rocky coasts their role as depositional environments abstract the role of rocky coasts as depositional environments has been generally neglected by rock and depositional coast workers although rock coasts can be hostile sedimentary environments they frequently host a variety of deposits consisting of mixes of boulders and megaclasts to sand and cobbles these deposits include pockets of sand and pebble trapped in topographic depressions or at the foot of scarps and cliffs isolated boulders pocket beaches trapped between headlands and sand to boulder beaches in shallow bays exposed to strong wave action the tectonic setting which is reflected in the degree of geological heterogeneity alongshore together with the wave regime and other elements of the morphogenic environment help to determine the amount and mobility of the sediment and consequently whether it plays an essentially abrasional or protectional role many beaches have a resistant rock foundation which will modulate their response to rising sea level and possibly increased storminess during this century wave refraction and temporal and spatial changes in sediment abrasional and protectional efficacy influence the development of crenulated planforms on coasts with a high degree of geological heterogeneity and possibly on more geologically homogeneous coasts with longshore variations in cliff height or in the amount of sediment theory suggests that these coasts may develop equilibrium planforms with uniform rates of erosion in bays and on headlands or they may undergo a series of cyclical transformations involving alternating increases and decreases in the depth of the bays relative to the headlands