preface archaean geology of the eastern goldfields of western australia regional overview abstract the eastern goldfields region forms part of the yilgarn craton which after the superior province of canada is one of the largest fragments of archaean granite greenstone terrain exposed at the surface of the earth this craton has much in common with the more intensely studied superior province but there are also significant differences between these two cratons both cratons were assembled from numerous smaller crustal fragments in a relatively brief period during the late archaean the superior province was assembled between 2725 and 2695 ma card 1990 and the yilgarn craton was assembled between c 2670 and 2650 ma myers 1993 both cratons contain fragments of older continental crust and volcanic arcs that formed just prior to collision and cratonisation the superior province contains extensive belts of metasedimentary rocks interpreted as accretionary prisms card 1990 whereas metasedimentary rocks form only a minor component of the yilgarn craton and most appear to postdate accretion both cratons contain significant concentrations of gold and support thriving gold mining industries the most prominent difference between the cratons lies in the nature of the granitoid rocks the superior province is dominated by tonalite and granodiorite whereas the yilgarn craton largely consists of granite this applies to granitoid rocks of all ages in each craton granite studies form a major part of this special volume of precambrian research

late archaean synorogenic basins of the eastern goldfields superterrane yilgarn craton western australia part ii kurnalpi terrane abstract the penny dam belches yilgangi white hills granny royal lucky brock and wallaby supersequences of the kurnalpi terrane crop out in synclines that are the erosional remnants of basins that developed as linear zones of subsidence between approximately north trending compartment bounding faults dominant sedimentary facies range from gravel rich and sand rich concentrated density flow deposits to thickly and thinly bedded bouma type turbidites background deposits are black shales or laminated green mudstones and banded iron formation is preserved in some condensed sections periods of non deposition are recorded by bedded chert which is the product of early diagenetic sea floor silicification the basins were separate deep marine canyon to linear fan systems that were linked laterally and distally by mud rich deposits there is only minor evidence for fault anchored canyon margin slope aprons basin development occurred during two stages separated by a period of deformation uplift and erosion sparse palaeocurrents establish sediment dispersal was to the south or southeast indicating that uplift to the north or northwest controlled palaeoslopes stacking of lithofacies is aggradational and consistent with deposition in fault bound basins tectonostratigraphic equivalence with siliciclastic supersequences of the kalgoorlie and gindalbie terranes is established by common depositional systems stratigraphic styles and stratigraphic responses to tectonic forcing consequently the siliciclastic supersequences represent overlap or late stage basins that tied together arc related terranes following terrane amalgamation similar depositional facies aggradational styles of facies stacking and two stage development characterise the syncollisional plio pleistocene coastal range basin of taiwan modern analogues are the deep marine southern longitudinal and taitung troughs off southeastern taiwan that are being filled by synorogenic sediments derived from the taiwan orogen

lithospheric processes and products in the southern canadian cordillera a lithoprobe perspective analyses of lithoprobe and other data from southwestern canada provide new insights on how this portion of the cordillera formed during plate convergence along the western margin of north america crustal rocks are detached from their mantle lithosphere which must have been consumed during subduction detachment occurred at or near the base of the crust beneath the intermontane and or omineca belts probably along the tips of tectonic wedges while the rocks were still outboard of the relatively cool mechanically rigid north american craton during the late cretaceous and early tertiary rotation of detached rocks caught between the north american craton and the oceanic plates accounts for some apparently conflicting results between paleomagnetic data that indicate large northward translation of rocks in the western cordillera and regional geological features that appear to preclude comparable amounts of translation of rocks in the eastern cordillera during the same time interval transpression assoc

late archaean deep marine volcaniclastic sedimentation in an arc related basin the kalgoorlie sequence of the eastern goldfields superterrane yilgarn craton western australia abstract the kalgoorlie sequence 2658 ma is a 3000 m thick succession of volcaniclastic sedimentary rocks and subordinate rhyolite dacite andesite and basalt spatially and temporally associated with subvolcanic sills and dykes of rhyolite and dacite gabbro sills and i type granitoids although basalts are tholeiitic the felsic rocks have ttd affinity the sequence comprises mostly deep marine channel levee turbidite complexes and hemipelagites resedimented syneruptive volcaniclastic deposits are associated with coherent lavas but almost all of the sedimentary fill was recycled from prior cycle volcanic and volcaniclastic sources provenance was mainly dacitic rhyolitic with minor andesitic basaltic and polymictic compositions volcano bound and fault bound architectures and two styles of basin filling are identified progradational or aggradational transverse fans and slope aprons and retrogradational longitudinal fans of a linear trough retrogradation in longitudinal systems is consistent with basin lengthening and deepening six depositional sequences are grouped in four unconformity bounded tectonic stages that record uplift subsidence cycles coeval mafic and felsic magmatism indicate that the tectonic stages represent extensional tectonic settings whereas volcanogenic provenance spatially linked volcanism and plutonic magmatism and deep marine environments support an intra arc site cyclic uplift subsidence and basin lengthening are more consistent with strike slip controls on basin formation than with orthogonal extension the tectonic setting is interpreted to have been a pull apart basin associated with strike slip faulting and amalgamating arc related terranes similar to the modern philippines archipelago the strong similarity between archaean volcaniclastic and modern arc related volcaniclastic environments implies comparable tectonic settings and therefore comparable controlling tectonic factors

tectonic controls on spatio temporal development of depositional systems and generation of fining upward basin fills in a strike slip setting kyokpori formation cretaceous south west korea the kyokpori formation cretaceous south west korea represents a small scale lacustrine strike slip basin and consists of an 290 m thick siliciclastic succession with abundant volcaniclasts the succession can be organized into eight facies associations representing distinctive depositional environments i subaqueous talus ii delta plain iii steep gradient large scale delta slope iv base of delta slope to prodelta v small scale nested gilbert type delta vi small scale delta lobe system vii subaqueous fan and viii basin plain facies associations i iii and iv together constitute a large scale steep sloped delta system correlation of the sedimentary succession indicates that the formation comprises two depositional sequences the lower coarsening to fining upward succession up to 215 m thick and the upper fining upward succession up to 75 m thick based on facies distribution architecture and correlation of depositional sequences three stages of basin evolution are reconstructed stage 1 is represented by thick coarse grained deposits in the lower succession that form subaqueous breccia talus and steep sloped gravelly delta systems along the northern and southern basin margins respectively and a sandy subaqueous fan system inside the basin abutting against a basement high this asymmetric facies distribution suggests a half graben structure for the basin and the thick accumulation of coarse grained deposits most likely reflects rapid subsidence of the basin floor during the transtensional opening of the basin stage 2 is marked by sandy black shale deposits in the upper part of the lower succession the black shale is readily correlated across the basin margins indicating a basinwide transgression probably resulting from large scale dip slip suppressing the lateral slip component on basin bounding faults stage 3 is characterized by gravelly delta lobe deposits in the upper succession that are smaller in dimension and located more basinward than the deposits of marginal systems of the lower succession this lakeward shift of depocentre suggests a loss of accommodation in the basin margins and quiescence of fault movements this basin evolution model suggests that the rate of dip slip displacement on basin margin faults can be regarded as the prime control for determining stacking patterns of such basin fills the resultant basinwide fining upward sequences deviate from the coarsening upward cycles of other transtensional basins and reveal the variety of stratigraphic architecture in strike slip basins controlled by the changes in relative sense and magnitude of fault movements at the basin margins

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 late archaean melita complex eastern goldfields western australia shallow submarine bimodal volcanism in a rifted arc environment abstract the melita volcanic complex is a late archaean bimodal rhyolite basalt volcanic succession within the gindalbie terrane in the eastern goldfields province of the yilgarn craton the melita complex has been dated by ion probe at 2683 3 ma 95 and forms part of a distinctive 2681 2692 ma volcanic association that records bimodal basalt rhyolite and calc alkaline intermediate silicic volcanism at several discrete volcanic centres and which locally hosts volcanic massive sulphide mineralisation teutonic bore approximately 3 km of stratigraphic thickness is exposed in the melita area the upper 1 1 5 km of the exposed succession is dominated by subaqueously resedimented volcaniclastic sandstones and breccias rhyolite flows and sills primary subaerial pyroclastic deposits including ignimbrites have not been identified in this study although subaerial explosive activity is indicated by the occurrence of accretionary lapilli and the abundance of vitric material shards and pumice fragments in resedimented deposits the lower part of the succession is dominated by pillowed to massive basalt lavas and in situ and resedimented mafic hyaloclastites mafic extrusive and intrusive rocks are tholeiitic with trace element concentrations similar to modern arc tholeiites felsic volcanic rocks at melita are dacite to high silica rhyolite they are highly enriched in incompatible elements particularly high field strength element enriched compared to other felsic associations in the eastern goldfields province representing evolved partial melts of heterogeneous intermediate arc type crust the volcanic facies and geochemistry of volcanic rocks at melita are consistent with those observed in modern intra arc or arc rift settings and the succession is interpreted to represent the initial stages of back arc rifting within a complex convergent margin

detrital zircon age spectra for late archaean synorogenic basins of the eastern goldfields superterrane western australia abstract the kalgoorlie gindalbie kurnalpi duketon and burtville terranes were amalgamated by 2658 ma into the eastern goldfields superterrane which was later accreted cordilleran style onto the foreland of a pre existing continent late stage synorogenic basins developed within the eastern goldfields superterrane during the early stage of accretion the basins are similar to all late stage basins of archaean provinces developing late in the tectonic cycle in a strike slip regime they developed in two stages during the gap in granite emplacement between 2658 ma and 2648 ma basin analysis suggests that the bulk of sediments was derived from rocks readily identifiable today within the superterrane consistent with the provenance style of all late stage basins sediment derivation from the foreland occurred only during stage ii and is recorded only from basins proximal to the suture detrital zircon geochronology has corroborated those interpretations eleven new shrimp u pb detrital zircon datasets and 14 previously published datasets indicate that the bulk of zircon bearing sediment was derived from the 2715 ma to 2658 ma high ca ttg granites and volcanic rocks that define the terranes moreover primary modes in the detrital zircon age spectra of 2680 3 ma 2673 ma 2666 3 ma and 2660 3 ma coincide with the peaks of emplacement of high ca granites provenance from across the suture has also been corroborated with detrital zircon age spectra of the kurrawang basin a stage ii basin close to the suture having no match to rocks of the eastern goldfields superterrane defining modes of 2730 ma and 3000 ma some as old as 3750 ma and 3540 ma can be matched to an 2735 ma calc alkaline volcanic province and quartzites with 4350 3130 ma detrital zircon in the foreland the study shows that detrital zircon age spectra can be powerful supporters of tectonic analysis but for the study presented here their interpretation has been greatly assisted by prior basin analysis and a considerable geochronological database of source rock equivalents

translating the mineral systems approach into an effective exploration targeting system abstract holistic mineral systems approaches are being increasingly adopted in the study of ore deposits but application in industry has been suboptimal because of the lack of a conceptual framework to help translate the mineral system understanding to practical application a four step process is proposed for linking the conceptual mineral system with data available to support exploration targeting these steps include translation from 1 critical processes of the mineral system to 2 constituent processes of the mineral system to 3 targeting elements reflected in geology and 4 targeting criteria used to detect the targeting elements directly or by proxy this translation process is illustrated using examples from komatiite hosted ni cu pge and orogenic au mineral systems ranking of targets must be at the critical process level rather than the current practice of mixing processes elements and proxies the significance of targeting elements and their mappable criteria changes as a function of the scale at which the critical processes operate and the availability of relevant geoscience datasets this scale dependence is rarely recognised in current practice sources of uncertainty when translating the mineral system understanding into an effective exploration targeting system include 1 resolution of a mappable criterion in a dataset 2 how well the targeting criterion reflects the targeting element 3 how well the targeting element reflects the critical process and 4 whether the process being mapped is critical for the genesis of a mineral deposit the first three sources of uncertainty collectively are termed the representativeness of the targeting criteria i e how representative is a mappable criterion of the constituent process for which it is a proxy the last source of uncertainty reflects our lack of understanding of the processes that control mineralisation and highlights areas for further research

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

architecture of the neoarchaean jaguar vhms deposit western australia implications for prospectivity and the presence of depositional breaks abstract the duration and nature of breaks in archaean volcanosedimentary packages recently re evaluated in the abitibi greenstone belt has been assessed at jaguar an archaean cu zn rich volcanic hosted massive sulphide vhms deposit in the teutonic bore volcanic complex tbvc the eastern goldfields of the yilgarn craton western australia the deposit is hosted by coherent volcanic facies and associated volcaniclastic facies with minor non volcanic facies the hypothesis that vhms ore lies on the intersection of volcanic centres and depositional breaks is found to be valid for the jaguar deposit with the site being an active volcanic complex at footwall time with further dome development close to the final ore location at mineralised package time and then reoccurring volcanic complexes andesitic and basaltic at several points in the hangingwall succession broadly tied into the ore position at jaguar the entire stratigraphic sequence faces west with no major structural complications making it ideal for stratigraphic analysis the footwall evidences prolific volcanism with no intervening sedimentation the mineralised package mp consists of intercalated dacite breccia conglomerate sandstone and mudstone the footwall volcanic rocks and the mp dacite appear to be differentiation products from the same magma chamber a major volcanic geochemical boundary is identified between the footwall mp tholeiitic to transitional affinities and the immediate hangingwall succession calc alkaline the hangingwall package includes four distinct volcanic units intercalated with mass flow deposits and graphitic argillites vhms mineralisation occurred across a distinct change in the geochemistry of erupted volcanic facies at a time of increased volcaniclastic sedimentation and extension this break is comparable to member level hiatuses seen in the abitibi gb i e the most brief of breaks because there is no silicification of sedimentary unit tops by silicic seawater exposure and there is minimal development of black shales a third time sensitive criteria was the development of peperite on the base of hanging wall hw andesite lavas the mp closely resembles breaks within interpreted deeper water domains of the abitibi gb for instance the deloro tisdale assemblage interface south of timmins the recognition of the change in the rate of emplacement of volcanic units and particularly the change in chemistry of volcanic rocks are critical exploration lithologic guides to use in the absence of chemical sediment deposits exhalites although crustal extension and basin subsidence were factors in the shaping of the succession their effects were too subtle to use as an exploration tool a corollary of the recognition of a member level vhms bearing interval in the teutonic bore volcanic complex is that like the kidd munro assemblage stratigraphy abitibi gb where several ore bearing depositional breaks are known below the great kidd creek deposit there is scope for the discovery of further potentially larger deposits on higher formation or group level breaks in the tbvc

the wangkathaa orogeny an example of episodic regional d2 in the late archaean eastern goldfields province western australia abstract the eastern goldfields province egp is a late archaean orogenic belt located on the eastern margin of the yilgarn craton the egp is characterised by a prominent nnw trending tectonic grain developed largely during regional e w oriented shortening a simplistic sequence of largely progressive compressional deformation events d 1 to d 4 has been used by previous workers to explain the development of the egp regional d 2 was thought to be responsible for most of the finite strain and therefore a reliable marker event for correlating deformation histories across the region a re examination of the deformation history has shown that d 2 kalgoorlie orogen of weinberg et al precambrian res 120 2003 219 239 was not a single progressive event rather it was episodic and involved several stages of switching of the tectonic mode compression extension switching between 2665 and 2655 ma the sequence of events during d 2 was an early stage of e w shortening d 2a followed by extension with basin formation and normal fault movement d 2e and finally a second stage of e w compression d 2b we introduce this sequence of events as the wangkathaa orogeny more complex in tectonics and broader in geographical scope than the kalgoorlie orogen features of the wangkathaa orogeny are well illustrated by the geometry and geological relationships that occur in the kurnalpi terrane welcome well area and the kalgoorlie terrane ora banda kambalda and the boorara domains of the central and southern egp available geochronology indicates that this sequence of events was likely to have been diachronous across the entire egp and the eastern southern cross province of the yilgarn craton recognition of these separate episodic stages of e w oriented compression and extension is important in our understanding the tectonic evolution of the egp switching tectonic mode between compression and extension will change the state of mean stress in a rock mass e g from net dilation to net constriction and vice versa and is an effective method in transporting and trapping mineral rich fluids the paradox of the different timings established for d 2 across the province are explained by the wangkathaa orogeny especially if it were diachronous as different workers dated different phases of an episodic orogeny

evidence for temporal fluctuations in marine radiocarbon reservoir ages in the santa barbara channel southern california abstract differences in the 14 c ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on san miguel island california suggest holocene 10 000 present fluctuations in marine 14 c reservoir ages these fluctuations coincide with 18 o and 13 c shifts measured in mytilus californianus shells from the same stratigraphic contexts and general atmospheric oceanic circulation models for the region based on these data we make three primary observations 1 significant changes appear to have occurred in the radiocarbon reservoir during the holocene 2 these fluctuations appear to correlate with regional oceanographic changes and 3 high resolution 14 c dating of marine shells may require different r values for different periods of time

geochemistry of metamorphosed volcanic rocks in the neoarchean qingyuan greenstone belt north china craton implications for geodynamic evolution and vms mineralization abstract the qingyuan greenstone belt qgb situated in the northeastern section of the north china craton ncc is considered to be the unique metallogenic province in china that hosts both banded iron formations bifs and volcanogenic massive sulfide vms deposits traditionally the qgb is divided into the hunbei and hunnan terranes separated by the hunhe fault and grouped into the lower shipengzi middle hongtoushan and upper nantianmen formations which have undergone amphibolite to granulite facies metamorphism exposed supracrustal rocks are composed of plagioclase amphibolite and biotite plagioclase gneiss with minor amounts of bif marble and schist in this study detailed field and petrographic observations lithogeochemical u pb geochronological as well as whole rock sm nd isotope analyses were conducted on the metamorphosed mafic and felsic volcanic rocks i e plagioclase amphibolite and biotite plagioclase gneiss respectively in the qgb in order to discuss implications for tectonic evolution and comitant vms mineralization the supracrustal rocks of both hunbei and hunnan regions were formed synchronously from 2 57 to 2 53 ga and then had undergone 2 52 2 48 ga regional metamorphism specifically the lower section of the shipengzi formation is composed dominantly of transitional tholeiitic basalts with negative nb anomalies suggesting that they were likely generated by partial melting of a mantle source that was previously altered by variable amounts of slab derived fluids or melts in contrast the lithologic assemblages grade upward into interlayered bimodal volcanic rocks i e n morb type tholeiitic basalts and fi to fii type dacites of transitional to calc alkalic affinities representing a change in tectonic regime related to subduction from compression to extension among them all the basalts are characterized by consistently positive initial nd compositions end t 2 7 to 3 4 further indicate a depleted mantle source whereas those dacites possess negative to positive initial nd values end t 4 6 to 3 0 suggesting they were formed by partial melting of depleted mafic source likely lower mafic crust and accompanied with variable addition of old crustal material significantly vms deposits are genetically linked to this extensional event and closely associated with the fii type dacites that were generated by higher melting degree at high temperature conditions and shallow crustal level likely 10 15 km in all geochemical features e g negative nb anomalies and end value together with contamination from continental crusts for tholeiitic mafic rocks and inherited zircons from these volcanic rocks imply a continental arc setting where the qgb was evolved

on the antiquity of the single piece shell fishhook ams radiocarbon evidence from the southern california coast abstract during the late holocene a number of new technologies single piece fishhooks toggling harpoons plank canoes etc are thought to have significantly enhanced the fishing capabilities of california coastal peoples the single piece fishhook perhaps the most common of these artifacts appears to correlate with a regional intensification of marine fishing and a period of increased population growth determining the antiquity of the single piece fishhook has been complicated by a variety of taphonomic and methodological factors consequently age estimates for the initial appearance of these artifacts range from about 5500 to 2500 cal bp to help clarify the chronology of this important artifact type we had eight of the potentially oldest shell fishhooks in the region ams radiocarbon dated these dates indicate that the single piece shell fishhook appeared throughout the southern and central california coast by at least 2500 cal bp our data illustrate the utility of direct ams dating of individual artifacts as a method of documenting site disturbances bioturbation historical land use etc and refining artifact site and regional chronologies

strike slip faults offshore southern taiwan implications for the oblique arc continent collision processes taiwan is the site of present day oblique arc continent collision between the luzon arc of the philippine sea plate and the chinese continental margin the major structural pattern revealed from marine geophysical studies in the area offshore southern taiwan is that of a doubly vergent orogenic belt bounded by significant zones of thrusting on the west and east of the submarine accretionary wedge due to the oblique collision process strike slip faults could play an important role in this convergent domain topographic lineaments revealed from new digital bathymetry data and seismic reflection profiles confirm the existence of three sets of strike slip faults in the collision subduction zone offshore southern taiwan the n s trending left lateral strike slip faults within the luzon volcanic arc the ne sw trending right lateral strike slip faults across the accretionary wedge and the nne ssw trending left lateral strike slip faults lie in the frontal portion of the accretionary wedge these strike slip faults overprint pre existing folds and thrusts and may convert into oblique thrusts or thrusts as the forearc blocks accrete to the mountain belt a bookshelf rotation model is used to explain the observed geometrical relationships of these strike slip fault systems based on this model the counter clockwise rotation of the forearc blocks in the area offshore southern taiwan could have caused extrusion of the accretionary wedge material into the forearc basin the originally continuous forearc basin is thus deformed into several closed and separate proto collisional basins such as the southern longitudinal trough and taitung trough a tectonic evolution model which emphasizes on the development of various structures at different stages of the oblique arc continent collision for the taiwan mountain belt is proposed

scale integrated architecture of a world class gold mineral system the archaean eastern yilgarn craton western australia abstract world class mineral systems such as those found in the archaean eastern yilgarn craton are the product of enormous energy and mass flux systems driven by lithospheric scale processes these processes can create big footprints or signatures in the lithosphere which can be observed at a range of scales and via a variety of methods including geophysics isotopes tectonostratigraphy and geochemistry we use these datasets to describe both the architecture structure of world class gold systems of the yilgarn craton and the signatures of their formation by applying an understanding of the most critical elements of the process and their signatures new areas especially undercover may be targeted more predictably than before knowledge of the major architectural elements of the yilgarn craton has increased greatly over the last decade through the collection of a wide range of geophysical geochemical and isotopic data these data range in scale from 1 lithospheric scale which provide information on the entire craton and their underlying volumes down to depths in excess of 350 km through 2 regional scale which provide information at the province scale and to depths of 30 40 km to 3 mine and camp scale which provide information on the top few kilometres of the crust the architecture structure in the upper mantle and lower crust can be inferred from broadband seismic tomography and analysis of long wavelength gravity data geophysical data such as magnetotellurics and deep crustal reflection seismic also provide evidence for the signatures of the flow of fluids through this architecture the pathways and they illustrate that the scale of the system is many orders of magnitude larger than the immediate deposit itself of particular importance is the role of deep crustal penetrating shear zones or faults which link the mantle with domes in the upper crust together these data provide first order insights into the physical and chemical properties of the yilgarn craton these insights provide geodynamic clues and constraints as to why the yilgarn is so well endowed in metals such as gold groves et al 1989 the intersection of favourable architectural features provides connections between the mantle and the upper crust in the kalgoorlie region possibly explaining why this area is so well endowed in comparison to others

discovered and undiscovered gold endowment of turkey a quantitative mineral resource assessment using gis and rank statistical analysis an assessment of the discovered and undiscovered gold endowment of turkey a prolific sector in the tethyan metallogenic belt is developed from a comprehensive geographic information system database containing 402 gold deposits and prospects the majority of the gold deposits and prospects are epithermal porphyry volcanic associated massive sulfides orogenic gold and skarn systems these five major deposit types form more than 90 of the known gold deposits and prospects just 87 corresponding to 21 6 of the deposits and prospects in the data set have current calculated gold reserve and or resources containing a total of 54 885 moz au current gold reserves of the country are 21 447 moz constituting 39 1 of the total gold resources of which 17 1 moz gold are contained in four deposits out of these 87 deposits and prospects only 27 contain significant gold reserve and or resources defined as equal to or more than 0 32 moz or 10 tons au and contain 91 8 of the total gold endowment of the country the cumulative frequency distribution model of the gold endowment of turkey abides by log normal distribution observed and estimated 10th 50th median and 90th percentiles of the data are 0 0046 moz 0 0045 moz estimated 0 1030 moz 0 0875 moz and 1 4969 moz 1 6938 moz respectively the 99th percentile of the data is 7 6444 moz 18 9636 moz the arithmetic mean of the known gold endowment is 0 657 moz and the swanson mean size is 0 492 moz the arithmetic mean of the 27 significant gold deposit or prospects is 1 94 moz zipf s law estimates of the undiscovered residual gold resources of turkey are based on the current size of the largest rank 1 gold deposit of turkey which is the kisladag porphyry deposit that has 17 481 moz gold endowment including past production zipf s law estimates a total of 88 261 moz natural or total gold endowment 57 133 moz or 65 of which has already been found this predicts at least 31 128 moz residual or undiscovered gold resources to be found in turkey though the lack of full delineation of the rank 1 deposit kisladag means that this figure is very conservative

kinematic nature and origin of regional scale ductile shear zones in the central yilgarn craton western australia abstract regional scale northwest and northeast trending ductile shear zones 1 to 6 km wide and over 100 km long are the most conspicuous structures in the central yilgarn craton western australia they are commonly developed along granite greenstone contacts but are centred in strongly foliated granite and granitic gneiss a wide range of kinematic indicators including well developed s c fabrics c type shear band cleavage and abundant asymmetric porphyroclasts consistently indicate sinistral movement on northwest trending shear zones and dextral movement on northeast trending shear zones major planar fabrics within the ductile shear zones include 1 a northwest or northeast trending foliation parallel to the shear zones 2 a northerly trending gneissic banding and 3 a northerly trending foliation the northwest and northeast trending foliations with associated asymmetric structural elements and a shallowly plunging mineral lineation were developed during a progressive inhomogeneous east west shortening event d3 characterized by low temperature noncoaxial deformation formation of the northerly trending gneissic banding and associated symmetric structural elements is attributed mainly to east west coaxial shortening d2 in a high temperature state during or shortly after granite intrusion the northerly trending foliation within the ductile shear zones commonly forms the s fabric of s c fabrics that was either developed during d3 same time as the c fabric or was reactivated from s2 foliations therefore major planar fabrics in the regional scale ductile shear zones of the central yilgarn craton can be ascribed to two tectonic events d2 and d3 and deformation within the shear zones includes both coaxial and noncoaxial components

the seismic parameter b of the frequency magnitude relation and its association with the geological zones in the area of greece abstract the parameter b of the frequency magnitude relation has been accurately calculated for each of the 21 seismic zones into which the aegean and surrounding area 34 n 43 n 18 e 30 e has been divided on the basis of several seismotectonic criteria these 21 seismic zones have been geographically separated into three a b c groups regions according to the values of the parameter b the outer region a is characterized by a relatively high value 1 03 the middle region b by an intermediate value 0 84 and the innermost region c by a low value 0 60 the boundaries of these three groups of zones almost coincide with the boundaries of well known geological zones this observation is interpreted in terms of mechanical heterogeneity of the material and of structural and stress conditions in the area

radiocarbon dating and the old shell problem direct dating of artifacts and cultural chronologies in coastal and other aquatic regions abstract archaeologists have long recognized the problem of the old wood effect in radiocarbon dating charcoal and wood samples the age of which may be hundreds of years older than their use by humans such problems have resulted in significant changes in how most researchers select wood and charcoal samples for 14 c dating with many now using relatively short lived carbonized materials for dating despite the significant strides made in our understanding of the potential biases of the old wood effect little emphasis has been placed on the possible impacts of dating old shell in archaeological deposits the use of marine shell for 14 c dating is widespread in coastal areas around the world including a growing emphasis on the dating of individual shell artifacts via accelerator mass spectrometry ams in dating shell artifacts we have obtained several dates older than associated 14 c dates for short lived subsistence remains from the same deposits including great disparities 10 000 years and more subtle differences 100 years these discrepancies appear to be due to the use of old shells by humans to make beads and other artifacts including shells collected from fossil deposits older archaeological sites and beaches the problems caused by the use of old shells to make beads and other artifacts are surmountable through careful sample selection analysis of multiple 14 c dates on a variety of materials and proper calibration procedures

predictive mineral discovery in the eastern yilgarn craton western australia an example of district scale targeting of an orogenic gold mineral system abstract the eastern yilgarn craton eyc is one of the world s premier gold provinces subject to over a century of mineral exploration prolonged interest in the terrane has led to the assembly of multiple world class data sets suitable for testing district scale targeting methodologies district scale targeting is concerned with identifying a mineral camp 60 km 60 km in size within a prospective region or province 1000 km 1000 km in size exploration at the district scale necessitates the development of predictive exploration models which can be applied to large regions recent advances in the study of the geodynamic evolution and 3d architecture of the eyc together with an understanding of their interrelationship with the orogenic gold mineral system has resulted in identification of critical mineralisation processes responsible for the region s rich gold endowment here we describe and map these critical processes using them as a basis for district scale targeting we relate gold mineralisation to three temporally constrained geodynamic periods integrated with regional hydrothermal alteration unlike many targeting methodologies this methodology does not incorporate the location of known gold deposits in the analysis yet it predicted 75 of known gold mineralisation in 5 of the area the methodology allows critical mineralisation processes to be identified and mapped through time and space these critical processes are mostly generic and can be applied to other granite greenstone orogenic gold regions such as the abitibi in canada an important outcome of this work for the eyc is the identification of a number of new target areas not known currently for significant gold mineralisation in what is otherwise thought to represent a mature terrane for gold exploration

the antiquity of olivella shell beads at ca ora 64 ams radiocarbon dated between 9420 and 7780 cal bp abstract investigations in the 1960s and 1970s showed the irvine site ca ora 64 to be among the oldest shell middens known from the pacific coast of north america the site chronology based on conventional analysis of mixed shell samples collected from heavily bioturbated soils extended back to ca 8440 rybp recent work at the site provided an opportunity to refine the ca ora 64 chronology via ams 14 c dating of single shell fragments including 14 olivella beads long considered to be one of the earliest ornament types made by pacific coast peoples such spire removed olivella beads were used through much of the holocene and generally are not good chronological indicators ams analysis of the ca ora 64 specimens however produced a consistent series of early holocene dates that includes some of the oldest securely dated shell beads in north america along with obsidian from interior sources olivella beads played an important role in early exchange networks between coastal and interior peoples methodologically our research demonstrates the utility of ams 14 c dating in determining the age of key artifact types found in multicomponent sites with assemblages affected by stratigraphic mixing

new results from physical modelling of arc continent collision in taiwan evolutionary model abstract both the analysis of the geological data and the results from 2d and 3d experimental modelling of arc continent collision in taiwan reveal the following major stages in this process 1 failure and thickening of the subducting crust of the chinese continental margin under the frontal part accretionary prism of the philippine sea plate psp since ca 6 7 ma 2 uplift squeezing and exhumation of the subducted crustal slice of the chinese margin and initiation of the central range about 5 ma ago 3 flexural buckling subsidence of the luzon arc fore arc under strong horizontal compression and sedimentary infilling of this area by the material shed from the growing and exhuming central range 4 failure of the psp along the west vergent longitudinal valley fault dipping beneath the arc and closure of the fore arc 5 subduction reversal and stoppage of continental subduction which has already occurred in northern taiwan and propagates to the south the southward propagation of the collision is not stationary currently occurring initial collision in southern taiwan and offshore to the south does not follow the same described above evolution as in central and northern taiwan the evolution of the collision in time and space should be considered in the framework of a 3d model where the psp rupture is preparing in the central and northern taiwan during a long time passing through a number of evolutionary stages once it has occurred the rupture longitudinal valley fault rapidly propagates to the south into the domain which did not undergo the pre rupture evolution the rupture front is currently located near 21 30 n

sedimentology of archean greenstone belts signatures of tectonic evolution abstract stratigraphic styles in archean greenstone belts are compared to those of modern and phanerozoic depositional basins in order to test the conformity of tectonic style through time six lithological associations in greenstone belts are recognized 1 mafic ultramafic volcanic 2 calc alkaline volcanic 3 bimodal volcanic 4 quartz arenite iron formation or carbonate 5 conglomerate wacke and 6 conglomerate arenite examples of the associations are described from the kaapvaal superior and zimbabwe provinces and the pilbara block each association differs only slightly between the four regions thereby emphasizing a common tectonostratigraphic theme sedimentary rocks are a minor component of the mafic ultramafic volcanic association they were deposited in two types of volcanic basin environments one similar to barred lagoons and bays around oceanic volcanic islands and the other similar to sediment starved platforms adjacent to coalesced volcanoes in inter arc intra arc and back are basins in contrast sedimentary rocks in the calc alkaline volcanic association comprise thick wedges of epiclastic and volcaniclastic detritus deposited in elongate sedimentary basins and thick wedges of pyroclastic and volcaniclastic detritus deposited adjacent to volcanic centers sedimentary facies were identical to those of forearc trench and marine volcanoplutonic arc settings chemogenic lithofacies in both volcanic associations were deposited in shallow to deep marine waters although shallow water profiles were selectively preserved in some terrains sedimentary rocks of the bimodal volcanic association are thick wedges of siliciclastic and volcaniclastic deposits interbedded with subaerial to submarine erupted flows of komatiite basalt and rhyolite depositional environments ranged from braid plain and braid delta to coastal marine and submarine fan starved basin deposits include banded iron formation and sulfidic black shale the association is identical to that of cratonic extensional basins in arc continent and intracontinental rifts sedimentary rocks of the quartz arenite iron formation or carbonate association onlap weathered basement or bimodal volcanic association rocks depositional environments were either transitional from fluvial to siliciclastic and carbonate marginal marine to offshore pelagic hemipelagic or from inshore intrabasinal clastic and volcaniclastic to offshore pelagic hemipelagic siliciclastic deposits are supermature two tectonic sites are represented those with siliciclastic facies represent continent adjacent syn to post rift stable shelves and those dominated by banded iron formation with volcaniclastic deposits represent arc adjacent post rift stable shelves sedimentary rocks of the conglomerate wacke association are represented by thick wedges of siliciclastic or volcaniclastic sandstone with minor volcanic components these were deposited in braid plain braid delta and submarine fan environments within elongate sedimentary basins coastal plain and pelagic basin facies are also present siliciclastic detritus was derived from syndepositional magmatic and metasedimentary thrust belts two stratigraphic styles are preserved one that records a flysch like stage of deep to marginal marine environments and the other that records a molasse like stage of marginal marine to fluvial environments the association is identical to that of compressional foreland basins of arc continent collisional and compressional arc tectonic affinities the conglomerate arenite association is preserved in elongate structural basins that transgress crustal components and all other supracrustal units it is dominated by thick wedges of siliciclastic sandstone although bimodal volcanic and volcaniclastic rocks can also be present depositional environments ranged from talus and alluvial fan and braid plain to either lacustrine or coastal marine local basin margins often show lateral offsets from source terrains and vertically skewed facies patterns longitudinal facies geometries are typical the association is similar to that of strike slip collisional graben in hinterland tectonic escape and terrane accretion orogens the examples show that despite all the ramifications of secular geophysical geothermal and geochemical global change the stratigraphic style of sedimentary rocks in archean greenstone belts can be matched with modern tectonic analogues thereby emphasizing the conformity of stratigraphic style through time the inseparable link between stratigraphic and tectonic styles implies that the tectonic style of greenstone belts was not temporally unique major differences exist with regards to the chemical composition of certain magmatic and sedimentary products but these are compensated for by their constant stratigraphic function in terms of depositional processes depositional environments and tectonic sites

the north anatolian fault a new look dedicated to the memory of three pioneers ihsan ketin sirri erinc and melih tokay and a recent student aykut barka who burnt himself out in pursuit of the mysteries of the north anatolian fault abstract the north anatolian fault naf is a 1200 km long dextral strike slip fault zone that formed by progressive strain localization in a generally westerly widening right lateral keirogen in northern turkey mostly along an interface juxtaposing subduction accretion material to its south and older and stiffer continental basements to its north the naf formed approximately 13 to 11 ma ago in the east and propagated westward it reached the sea of marmara no earlier than 200 ka ago although shear related deformation in a broad zone there had already commenced in the late miocene the fault zone has a very distinct morphological expression and is seismically active since the seventeenth century it has shown cyclical seismic behavior with century long cycles beginning in the east and progressing westwa

multiple gold mineralizing styles in the northern pataz district peru gold production from the northern pataz district in the eastern andean cordillera of peru has been sourced mainly from mesothermal quartz carbonate sulfide veins hosted by the mississippian pataz batholith gold is also found in basement hosted veins underlying the batholith in the vijus santa filomena area of the district both are located within a central horst similar vein mineralogy and proximal phengitic white mica alteration are common to both however comb textured quartz the chemical compositions of bulk ore and sulfide minerals and the presence of barite and siderite veins suggest that the basement hosted veins formed at a shallower crustal level similar expressions of hydrothermal alteration associated with anomalous gold as sb and tl are also present in the adjacent lavasen graben where alteration is intimately associated with volcanic processes that deposited the mississippian lavasen volcanics k ar and 40 ar 39 ar ages for hydrothermal illite from all three locations range between mississippian and late triassic but are consistent with a single mississippian hydrothermal event if the data record a minimum age for original illite formation the geologic setting mineralization styles and chemical data suggest a range of crustal depths ranging from mesothermal batholith hosted veins through shallow to intermediate depths for the vijus santa filomena area to a near surface epithermal setting for the misquichilca area telescoping of this 10 to 13 km crustal range into a 3 km topographic section of the andes is attributed to syn and postmineralization uplift and erosion sulfide rich high grade ore shoots and moderately saline fluid inclusions in the batholith hosted veins are inconsistent with the original orogenic gold model and suggest a magmatic source component for the ore fluid consistent with stable isotope o h c and s compositions of quartz illite carbonates and sulfides the isotopic data suggest a mixed magmatic meteoric ore fluid in the basement hosted deposits of the vijus santa filomena area and the volcanic hosted misquichilca area both the pataz batholith and the esperanza subvolcanic complex are of the same mississippian age as the hydrothermal alteration and mineralization the esperanza subvolcanic complex comagmatic with the lavasen volcanics contains cognate mineral clots from which a subjacent magma chamber can be inferred it exhibits potassic calc silicate and argillic alteration and evidence for the evolution of an fe rich volatile phase the lavasen esperanza magma suite is ferroan and weakly alkaline with a type affinities these features provide a conceptual genetic link with hydrothermal alteration associated with gold mineralization including fe as sulfides phengitic white mica celadonite fe rich carbonates and less common fe oxides an oxidized intrusion related model is proposed for gold and hydrothermal alteration in the northern pataz district

major crustal boundaries of australia and their significance in mineral systems targeting abstract for over 35 years deep seismic reflection profiles have been acquired routinely across australia to better understand the crustal architecture and geodynamic evolution of key geological provinces and basins major crustal scale breaks have been interpreted in some of the profiles and are often inferred to be relict sutures between different crustal blocks as well as sometimes being important conduits for mineralising fluids to reach the upper crust the widespread coverage of the seismic profiles now allows the construction of a new map of major crustal boundaries across australia which will better define the architecture of the crustal blocks in three dimensions it also enables a better understanding of how the australian continent was constructed from the mesoarchean through to the phanerozoic and how this evolution and these boundaries have controlled metallogenesis starting with the locations in 3d of the crustal breaks identified in the seismic profiles geological e g outcrop mapping drill hole geochronology isotope and geophysical e g gravity aeromagnetic magnetotelluric data are used to map the crustal boundaries in plan view away from the seismic profiles some of the boundaries mapped are subsurface boundaries and in many cases occur several kilometres below the surface hence they will not match directly with structures mapped at the surface for some of these boundaries a high level of confidence can be placed on the location whereas the location of other boundaries can only be considered to have medium or low confidence in other areas especially in regions covered by thick sedimentary successions the locations of some crustal boundaries are essentially unconstrained unless they have been imaged by a seismic profile from the mesoarchean to the phanerozoic the continent formed by the amalgamation of many smaller crustal blocks over a period of nearly 3 billion years the identification of crustal boundaries in australia and the construction of an australia wide gis dataset and map will help to constrain tectonic models and plate reconstructions for the geological evolution of australia and will provide constraints on the three dimensional architecture of australia deep crustal penetrating structures particularly major crustal boundaries are important conduits to transport mineralising fluids from the mantle and lower crust into the upper crust there are several greenfields regions across australia where deep crustal penetrating structures have been imaged in seismic sections and have potential as possible areas for future mineral systems exploration

ancient long distance trade in western north america new ams radiocarbon dates from southern california abstract eleven olivella biplicata spire lopped shell beads from six sites located 250 365 km inland from the pacific coast of southern california produced ams dates between 11 200 and 7860 cal bp olivella shell beads were well documented items of prestige and media of exchange in native california and recovery of these examples from inland contexts indicates low level exchange between resident populations of the coast and the southwestern great basin by at least 10 300 10 000 cal years bp these findings represent some of the earliest unequivocal evidence for long distance trade in western north america and push the antiquity of this important form of inter group interaction back several thousand years earlier than previously thought

regularities in time and space distribution of seismicity in the periadriatic regions tectonic implications abstract the pattern of energy release in the very active seismic belt along the hellenides and southern dinarides which is interpreted as the main collision boundary between the adriatic plate and the balkan regions has been characterized in the last three centuries by a fairly regular succession of active and quiescent phases statistical tests have indicated a very low probability of observing this kind of pattern associated with a random generation of earthquakes the discontinuous release of seismic energy might be connected with a periodic activation of the underthrusting of the adriatic mesozoic platform beneath the dinarides hellenides belts this effect could condition the kinematic behavior of the whole adriatic plate this hypothesis might explain the fact that the italian regions lying on the other side of the adriatic platform also show a seismic energy release pattern characterized by alternating active and quiescent periods which furthermore proves to be well correlated in time with those occurring at the adriatic balkan border

evidence of interrelation between the seismicity of the southern apennines and southern dinarides abstract during the last two centuries the strongest earthquakes in the southern apennines m 5 5 have almost regularly occurred within a short time a few months to some years of the occurrence of earthquakes in southern yugoslavia the high statistical significance of this correspondence suggests the presence of a tectonic connection between the two zones

prospectivity analysis of the plutonic marymia greenstone belt western australia abstract the plutonic marymia greenstone belt is the sixth largest gold camp in western australia quantitative estimates of the residual endowment of this greenstone belt based on zipf s law indicate that the belt contains between 5 5 and 5 9 moz of gold in undiscovered deposits larger than 0 1 moz including six undiscovered deposits ranging in size between 0 7 moz and 0 4 moz and another six undiscovered deposits ranging between 0 3 moz and 0 2 moz in addition to several smaller deposits gis based prospectivity analyses using weights of evidence and logistic regression models were undertaken to delineate prospective areas where these yet to be discovered deposits could be spatially located this knowledge will be critical in guiding future exploration programs in the plutonic marymia greenstone belt

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

towards producing mineral resource potential maps within a mineral systems framework with emphasis on australian orogenic gold systems abstract discovery of new deposits has slowed dramatically since the beginning of the 21st century despite increased expenditure targeting below deep complex cover is recognised as key to opening up new search spaces and re invigorating exploration success existing techniques and technologies are reaching maturity as direct detection exploration methods are costly and have limited success when targeting beneath cover thus the application of a predictive conceptual based approach to exploration targeting is required the mineral systems concept provides a framework within which the critical elements of a system can be defined and incorporated into a predictive exploration targeting model however modelling of entire mineral systems remains in its infancy as such the effective translation of the mineral systems concept into robust targeting models is defined as a significant research challenge by several authors a conceptual whole system modelling approach is proposed in light of the critical elements of an orogenic gold mineralising system and a review of existing exploration tools the approach combines probabilistic sub models for predicting total mineral endowment with localised mineral distribution linking resource endowment assessments total mineral endowment with fluid dynamics and fluid rock interaction modelling local mineral distribution provides an opportunity to develop resource potential maps that define the approximate cost benefit of exploring any given location further research is required for such modelling methods to become feasible although hydrodynamic and hydrogeologic modelling has advanced in other research fields methods for modelling auriferous fluid flow through the crust remain under developed this in part is due to detailed 3d geological data being unavailable or prohibitively expensive to acquire potential solutions to limited data availability include the development of more advanced interpolation and geophysical inversion methodologies based on data from well understood geological provinces resulting in improved 3d geological interpretations collaboration between academia and the minerals industry to develop an integrated approach to entire mineral system modelling may lead to successful predictive exploration by providing a meaningful output to guide decision making during the exploration targeting process

mossman orogenic gold province in north queensland australia regional metallogenic controls and undiscovered gold endowment the hodgkinson and broken river provinces of the mossman orogen in north queensland host numerous orogenic gold deposits and still remain under explored this paper discusses regional metallogenic controls and results of a probabilistic quantitative assessment of undiscovered gold potential in the region significant orogenic gold deposits in the region occur only within relatively small well endowed metallogenic zones likely to be controlled by the eastern margin of the paleoproterozoic continental crust underlying the western mossman orogen three distinct styles of primary orogenic gold deposits are present in the area gold quartz veins refractory gold associated with quartz pyrite arsenopyrite veins and stockworks and stibnite quartz gold veins refractory gold deposits are estimated to have the highest potential for significant undiscovered resources in the region the hodgkinson province is estimated to host between one and ten significant undiscovered refractory gold ore fields with a 50 probability of at least 20 t of total contained gold and a 90 probability of at least 1 t the broken river province is estimated to host up to five significant undiscovered refractory gold ore fields with a 50 probability of at least 12 t of contained gold

early new world maritime technologies sea grass cordage shell beads and a bone tool from cave of the chimneys san miguel island california usa recent excavations at cave of the chimneys ca smi 603 located on san miguel island revealed well preserved sea grass knots twined cordage olivella spire ground beads and a bone gorge the assemblage dated to roughly 8000 years ago is dominated by s twist cordage and includes an assortment of strands loops and knotted pieces wrapped sea grass knotted balls including some stained red suggest they may have had a decorative function unique among paleocoastal assemblages of the area these artifacts offer a rare glimpse into the non lithic technologies of early native americans on the pacific coast of north america

archean plate tectonics what can be learned from continental geology some basic questions about archean plate tectonics can be addressed by examining accretionary archean margins in particular fault zones with significant strike slip components on the canadian shield 1 were the oceanic plates typically rigid like modern plates yes significant lateral viscosity contrasts in the lithosphere between plates and plate boundaries are required for major strike slip faults to exist conversely strike slip faults are a kinematic consequence of rigid plates 2 did large oceanic plates exist in the archean probably first the length and offset of the longest preserved segments of archean faults are similar to modern examples such as in alaska less directly the duration of a period with a consistent sense of strike slip at a point on the continental side of an accretionary margin should be related to the time that a typical oceanic plate remains outboard of the margin this time varies proportionally with size of typical ocean plates and inversely with their velocity the

sedimentary basin controls on orogenic gold deposits new constraints from u pb detrital zircon and re os sulphide geochronology lynn lake greenstone belt canada abstract sedimentary basins that open and close during the last stages of mountain building represent an important exploration criterion for orogenic gold deposits however the genetic and or preservation controls of these synorogenic or timiskaming type sedimentary basins and their controlling fault systems on orogenic gold deposits remain unclear herein we address that knowledge gap and report new u pb detrital zircon and re os sulphide arsenopyrite and pyrite geochronology and sulphide pb isotope results for the paleoproterozoic lynn lake greenstone belt llgb manitoba canada the youngest detrital zircon from all six meta conglomerate and psammite samples of the synorogenic sickle group and previously reported u pb zircon ages for post sickle group intrusions are used to constrain its depositional timing from 1836 15 to 1831 4 ma replicate analyses of one highly radiogenic arsenopyrite sample from an auriferous vein at the maclellan gold deposit yield a weighted average re os model age of 1824 12 ma which is identical to previously published in situ u pb xenotime ages at the same deposit 1827 8 ma each of these hydrothermal ages demonstrate that early stage auriferous veins immediately post date deposition of the sickle group and most likely occurred prior to peak metamorphism 1814 1801 ma this sequence of events is very similar to the abitibi greenstone belt suggesting that a synorogenic phase of extension and rapid burial of auriferous veins by timiskaming type sickle group sediments may have played an important genetic and or preservation control on early stage gold mineralization in the llgb however unlike the abitibi greenstone belt none of the known gold deposits within the llgb are hosted within the sickle group younger re os model arsenopyrite ages at 1782 16 ma from the maclellan gold deposit also post date synorogenic sedimentary basins by ca 50 myr these late stage auriferous veins are unrelated to the synorogenic extensional phase and more likely reflect repeated fluid focusing along reactivated structures during a post peak metamorphic phase of hydrothermal activity the multi stage hydrothermal history of orogenic gold deposits in the llgb also provides a possible explanation for the mixture of depleted mantle like and highly radiogenic fluid components that are inferred from age corrected sulphide pb isotope compositions 1 8 ga 8 9 10 6 reworked cratonic margins and their associated greenstone belts thus represent favourable depositional settings for auriferous fluids at multiple stages throughout the lifespan of an orogen

groundmass microsampling using laser ablation time of flight inductively coupled plasma mass spectrometry la tof icp ms potential for rhyolite provenance research abstract provenance research using rhyolite formations that cooled too slowly to form obsidian has proven difficult for geochemical researchers to date uncertainties about the temperature regimes within the parent magma chamber and subsequently of the eruption process itself yield highly divergent phenocryst compositions and quantities variable and uncertain phenocryst composition and content make bulk and surface compositional analysis techniques e g inaa xrf ineffectual without efforts to homogenise or render samples into solutions this is frequently not a viable option for archaeological materials thus rendering provenance research on rhyolite artifacts impractical using traditional techniques one hundred and fifty one source samples from five rhyolite sources in the western mojave desert california were used to conduct a pilot study on the potential for using la tof icp ms to pursue provenance research using rhyolite to test this methodological question an archaeological case study using fifty one rhyolite artifacts collected from the western mojave desert region was sampled analysis of samples indicates that using la tof icp ms to microsample the rock s groundmass coupled with multivariate statistics can confidently distinguish rhyolite sources in geochemical space results indicate that geochemical survey and analyses of rhyolite sources should be undertaken to provide a database for archaeological provenance studies in the region

genesis of the hanwang fe deposit in neoarchean granite greenstone succession of the eastern north china craton abstract research on history of the earth s continents and the genesis of mineral deposits has been one of the hotspots in geology but only limited studies have been completed on iron deposits hosted by banded iron formations bifs such as the large hanwang iron deposit located in the eastern north china craton ncc in this contribution we present the petrology zircon u pb geochronology lu hf isotopes and whole rock geochemistry on hanwang iron deposit hosted by the metamorphosed neoarchean to early paleoproterozoic taishan group and orthogneiss derived from tonalite trondhjemite granodiorite ttgs magnetite bearing amphibolite magnetite bearing quartz amphibolite and gneiss host the hanwang iron deposit which is characterised by subhedral to euhedral magnetite pyrite with minor galena and bif laminations gangue minerals include hornblende plagioclase and quartz with minor amounts of biotite chlorite epidote and microcline this mineral assemblage is indicative of amphibolite facies metamorphism with regression to greenschist facies the deposit is located in a transition zone between metamorphosed mafic to felsic volcanic rocks the age of the hanwang bif hosted iron deposit is late neoarchean lu hf isotope systematics indicate that the protolith for the biotite amphibolite is derived from a neoarchean mantle contaminated by the crust and orthogneiss is derived from the neoarchean crust the biotite amphibolite is characterised by high na fe and low k assays enrichment in light rare earth elements lree and relatively depletion in heavy rees hree without an obvious ce anomaly the geochemistry of the orthogneiss is characteristic of a volcanic arc granite although this must be accepted with caution given that the orthogneiss is metamorphosed and deformed at amphibolite facies it is proposed that hanwang iron deposit was deposited in a marine volcanic arc environment and derived from hydrothermally leached volcanic units and similar to the algoma type iron deposit most bifs occurring in neoarchean granite greenstone succession of the eastern ncc belong to the algoma type iron deposits globally this sequence appears to be coeval with the yilgarn craton in western australia

structural mineralogical and geochemical constraints on the atypical komatiite hosted turret deposit in the agnew mt white district western australia in the norseman wiluna belt yilgarn craton the agnew mt white district is the host of many gold deposits located in the hinge of the regional lawlers anticline the turret gold deposit is structurally controlled by the table hill shear zone that transects the agnew ultramafic unit geochemistry coupled with petrographic data allowed the delineation of the paragenetic sequence associated with gold mineralisation and include 1 a pervasive talc carbonate alteration assemblage 2 a pre mineralisation stage associated with pervasive arsenopyrite chalcopyrite pyrrhotite pyrite alteration followed by 3 a late deformation event along a dilatational segment of the main table hill shear zone leading to the formation of a breccia hosting a cu bi mo au ag zn te w metal assemblage the presence of au ag cu alloys native bismuth chalcopyrite and other bi te s phases in the mineralisation stage suggest that gold may have been scavenged from the hydrothermal fluids by composite bi te cu au ag s liquids or melts using this mineral paragenetic sequence together with mineralogical re equilibration textures observed we show that the gold deposition at turret occurred over a temperature range approximately between c 350 and 270 c this temperature range together with the structural control and typical mesothermal alteration pattern including carbonate chlorite alteration shows that the turret deposit shares common characteristics with the orogenic gold deposit class however the metal association of cu au bi and mo the quartz poor and high copper sulphide content up to 15 are characteristics that depart from the typical orogenic gold deposit mineralogy through comparison with similar deposits in the yilgarn craton and worldwide we propose that the turret deposit represents an example of a porphyry derived au cu bi mo deposit

a two stage model for the formation of the granite greenstone terrains of the kalgoorlie norseman area western australia abstract accurate dating of granites and greenstones from the kalgoorlie norseman area shows that there is considerable overlap in time between the formation of granites and greenstones however within any given area the oldest granites are always younger than the oldest greenstones it is suggested that the long lived 100 ma thermal anomaly in the uppermost asthenosphere that gave rise to the greenstones is also responsible for regional metamorphism and widespread crustal melting leading to the production of granites the time lag between greenstone and granite formation reflects the time taken to conduct heat from the mantle to the lower crust anatexis of the lower crust produces a layer of light granitic magma that may temporarily stop the ascent of basaltic magma where this happens the basaltic magma ponds at the base of the crust supplying additional heat and accelerating the melting process eventually the granitic melt layer becomes unstable and rises within the crust areas intruded by granite become topographic highs with topographic lows forming above areas where light melt has been withdrawn from the lower crust when the topographic highs protrude above sea level they are eroded to shed sediments into the topographic lows which contain the basaltic greenstones thus the change from a basalt dominated lower greenstone succession to a sediment and felsic volcanic dominated upper whitestone sequence seen in many granite greenstone terrains results from the intrusion of granitic magma into the upper crust the crust of the kalgoorlie norseman area formed in two distinct stages separated by a time break of up to 700 ma the first stage involved the formation of primitive crust probably above subduction zones this primitive crust was characterized by low rb sr and high sm nd ratios the second stage resulted from a major change in mantle convection that produced thermal upwellings in the mantle below the continents this led to the eruption of basaltic magmas and to metamorphism and anatexis of the lower crust to produce granitic magmas melting reset the rb sr sm nd and u pb systems giving the impression that the second event which occurred at 2 7 ga was a major crust forming event it was in fact a crustal reworking process although some basalt was added to the crust at this time although the two stage history of the kalgoorlie norseman area is clearly seen in the lead isotopes and in zircons it is not readily discernible from the rb sr and sm nd systematics due to mantle like ratios of those elements in the primitive crust

undiscovered orogenic gold endowment in northern victoria australia abstract the northern part of the victorian gold province australia is covered by cainozoic sediments and remains poorly explored this contiguous covered area of over 44 000 km 2 is highly prospective for orogenic gold deposits this paper discusses results of probabilistic quantitative assessments of undiscovered gold potential in the northern covered parts of the western lachlan orogen the stawell bendigo and melbourne zones for the bendigo and stawell zones quantitative estimates were only made for undiscovered mesozonal orogenic gold quartz vein deposits the predominant type of gold mineralisation in that region for the northern part of the bendigo zone under cover 10 000 km 2 the mean estimate is approximately 1000 t with a 90 probability of at least 290 t of gold in undiscovered mesozonal orogenic gold deposits for the northern covered area of the stawell zone 30 000 km 2 the mean estimate is 1200 t with a 90 probability of at least 200 t of undiscovered gold the northern part of the melbourne zone 4400 km 2 is considered prospective for epizonal orogenic gold deposits associated with quartz pyrite arsenopyrite veins and stockworks or with quartz stibnite gold veins the mean estimate for that area is 90 t with a 90 probability of at least 10 t of gold in undiscovered epizonal orogenic gold deposits

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

rank statistical analysis of nickel sulphide resources of the norseman wiluna greenstone belt western australia estimating the undiscovered mineral resources of a terrane is a challenging yet essential task in mineral exploration we apply zipf s law rank statistical analysis to estimate the undiscovered nickel sulphide resources in the norseman wiluna greenstone belt western australia the analysis suggests that about 3 0 to 10 0 mt of nickel sulphide resources are yet to be discovered in this belt compared to the currently known total nickel sulphide endowment of 10 8 mt this undiscovered nickel sulphide endowment is likely to be hosted by incompletely delineated deposits and undiscovered deposits in less explored komatiites in the belt using the more detailed data subset of the kambalda domain this study manipulates zipf s law to estimate the sizes of undiscovered deposits in addition to the domain s total nickel sulphide endowment estimate importantly regression analysis shows that the gradient of the line of best fit through the logarithmic rank size plot for the detailed kambalda data subset is 1 this gradient which is the key zipf s law constant k has the value of 0 92 for the norseman wiluna greenstone belt which is collectively less mature than the kambalda domain this result corroborates the use of k 1 in zipf s law predictive analyses of mineral resources for deposit populations for which the value of k 1 has not yet been attained due to exploration immaturity

granite cored domes and gold mineralisation architectural and geodynamic controls around the archaean scotia kanowna dome kalgoorlie terrane western australia abstract granite cored domes are associated with many of the larger gold deposits of the archaean eastern yilgarn craton of western australia the scotia kanowna dome is eroded to sufficiently deep levels to provide insights into the role granite cored domes play in controlling fluid flow and gold deposition at the centre of the scotia kanowna dome is a granite batholith which is surrounded by outward dipping greenstone belts and associated shear zones this upper crustal dome sits above mid crustal domes providing a series of stacked geometries favourable to focussed fluid flow a number of small to medium sized gold deposits occur on the limbs and the centre of the dome and the world class kanowna belle gold mine occurs on the nose of the dome at least three separate gold mineralising events are defined each of regional significance which can be correlated with other well known gold deposits of the eastern yilgarn craton the palaeostress across this region was dominated by both maximum contractional and extensional vectors oriented perpendicular to the north northwest trending grain the resultant strain is seen in the architecture of the scotia kanowna dome with its margins and associated shear zones controlling the distribution of stratigraphy which is relatively linear and parallel to the margin throughout most of the tectonic history the flanking shear zones were high strain domains that recorded multiple stages of contraction with thrust and mostly sinistral strike slip shear kinematics in contrast the dome nose region was a relatively low strain domain as it was located in the strain shadow of the regional contractional events for example the early extensional record has been preserved at the nose with late stage basins formed in the hangingwall to the extensional faults adding to the stratigraphic complexity of the local region these late basins also may have contributed to the fluid budget in contrast along the flanks of the domes there is no record of these late basins or the extensional faults that controlled their deposition the architecture of the dome played an important role in controlling mineralisation during a significant deviation in the maximum contractional stress vector to an east southeast west southwest orientation at this time basins in the nose region underwent inversion with thrusting to the north and northwest shortening was accommodated along the dome flanks by sinistral strike slip shearing which was relatively free to move due to the mostly linear stratigraphy combined with limited anisotropy and perturbations along the flank however the stratigraphic and geometrical complexity around the dome nose resulted in localised maximum dilation and gold deposition at this time the dome nose area was also a favoured locus for gold enriched dominantly mafic type magmas which are seen as the extensive porphyry swarms in the region these felsic intermediate rocks also may have contributed to the complex fluid budget and are considered as indicators of particular fertility for gold they may have been the primary source for much of the metal endowment the architecture of granite cored domes has played a critical role in focussing magma as well as mineralising fluids into regions of maximum dilation they did this by virtue of their inherent competence and by influencing the position and geometry of shear zones fluid pathways and hence distribution of stratigraphy depositional sites across the region the scotia kanowna dome is a good example of this effect and inferences can be made in favour of similar controls by concealed domes such as beneath kalgoorlie

differences in radiocarbon age between shell and charcoal from a holocene shellmound in northern california abstract the west berkeley shellmound the oldest well dated archaeological site in the san francisco bay region contains shell and charcoal ranging in age from ca 1200 to 5700 cal yr b p radiocarbon ages of marine shell and charcoal collected from fifteen stratigraphic levels in the west berkeley shellmound suggest changes in the 14 c content of san francisco bay surface waters relative to the atmosphere the oceanic reservoir age over the past 5000 yr the reservoir age of san francisco bay waters fluctuated between 870 and 170 14 c yr over the past 5000 yr with the lowest values occurring 2900 to 3800 cal yr b p and the highest values between 1200 and 2000 cal yr b p changes in the radiocarbon reservoir age may be due to changes in the strength of seasonal wind driven upwelling off coastal california where upwelling brings 14 c depleted waters to the surface the period of lowest r values at 3500 to 3900 cal yr b p is coincident with relatively low salinity in san francisco bay indicating high freshwater inflow and wet climate in california based on lake level records the period of high r values 1200 2000 cal yr b p is coincident with one of the driest periods in california during the late holocene these data suggest a link between coastal upwelling and precipitation over central california the age of the top of west berkeley mound and several other mounds in the san francisco bay region 1100 to 1300 cal yr b p coincides with a prolonged dry period in california and low river inflow to san francisco bay perhaps the sites were abandoned because of the drought

appraisal of the usgs three part mineral resource assessment through estimation of the orogenic gold endowment of the sandstone greenstone belt yilgarn craton western australia regional scale ground selection presents a significant risk in mineral exploration targeting as any exploration search space contains a finite and fixed number of ore bodies selection of barren or depleted search spaces incurs wasted exploration expenditure by defining regions of estimated high mineral endowment via generation of quantitative information as to the value of potential discoveries mineral exploration effectiveness project acquisition and exploration portfolio management can be improved the three part mineral resource assessment developed by the united states geological survey usgs is a methodology designed to assist in this process here two separate assessments are applied to estimate the orogenic gold endowment of the sandstone greenstone belt in the yilgarn craton western australia first the results of a global regression assessment median endowment of 33 t 1 16 moz au mean of 130 t 4 59 moz au based on an available but outdated global grade tonnage model for low sulfide gold quartz vein deposits suggest that most outcropping and shallow orebodies in the sandstone greenstone belt have been discovered and fully delineated in contrast an expert assessment median endowment of 210 t 7 41 moz au mean of 220 t 7 76 moz au using expert derived grade and tonnage distributions specific to the sandstone greenstone belt predicts that significant gold mineralization remains to be discovered largely beneath cover the contrasting assessments imply a step change in exploration focus from surficial deposits at the time of the usgs global grade tonnage model to those buried under cover at the present time the expert assessment in contrast to the global regression assessment implies the potential for deeper exploration targets within the sandstone greenstone belt based on the predicted total number of deposits much of the undiscovered mineral endowment is likely to be distal to known ore bodies beneath cover and at greater depths within the belt

late archaean synorogenic basins of the eastern goldfields superterrane yilgarn craton western australia abstract siliciclastic supersequences of the kalgoorlie and gindalbie terranes post date 2660 ma deformation uplift and erosion associated with the amalgamation of arc related terranes but were tectonically buried to greenschist or amphibolite facies during the orogenic shortening that accreted the eastern goldfields superterrane to the yilgarn craton the supersequences are synclinal remnants of late stage basins that were linear zones of subsidence adjacent to north trending strike slip faults fluvial facies merougil navajo jones creek scotty creek and yandal basins are dominated by sheet sandstones that represent the deposits of medial braid plains but proximal channel and bar complexes of cobble and boulder conglomerates are also preserved submarine facies kurrawang basin range from boulder to pebble conglomerates but are dominantly bouma turbidites with rare black shales and record the filling of a proximal canyon that fed a distal submarine fan axial depositional systems are preferentially preserved in all basins but transverse systems are preserved at the base of some fluvial deposits the gross vertical succession in all basins is from proximal up to distal the basins developed during two tectonic stages separated by an intervening period of uplift tilting and erosion with the southern kalgoorlie terrane recording change from a stage i fluvial to a stage ii deep marine basin stage ii fluvial deposits are preserved in the northern kalgoorlie terrane and in the gindalbie terrane sparse palaeocurrents establish sediment dispersal was to the south or southeast implying uplift to the north or northwest controlled palaeoslopes stacking of lithofacies is aggradational and is consistent with limited lateral migration of facies tracts in fault confined basins similar lithofacies and aggradational styles of facies stacking characterise syncollisional sequences of the cenozoic coastal range basin of taiwan and the present day syncollisional basins of southeastern taiwan are good analogues of late stage basins of the kalgoorlie and gindalbie terranes

formation of an archaean continent about 30 of the earth is covered by continents but only about 10 small kernels of these continentsae known as archaean cratonsae are continental fragments formed before 2 5 gyr ago the kaapvaal craton of south africa which formed and stabilized between 3 7 and 2 7 gyr ago is one of the oldest reasonably sized examples of these continental fragments it consists of a mosaic of subdomains that have been welded together by processes similar to those of modern day plate tectonics the earliest subdomains may have owed their origin to the onset of efficient recycling from the earth s hydrosphere into the mantle

lithospheric structure in the southern canadian cordillera from a network of seismic refraction lines lithospheric velocity structure and its relationship to regional tectonics and development of the southern canadian cordillera are derived from a synthesis of interpretations from nine in line seismic refraction wide angle reflection profiles and broadside data recorded during the lithoprobe southern cordillera refraction experiment score and other refraction experiments across southern british columbia and one profile in northwestern washington consistency of the score two dimensional models at their intersection positions is achieved through application of a simultaneous inversion of all relevant traveltime data the cross sectional and map presentations demonstrate the strong degree of three dimensional heterogeneity within the crust and upper mantle a first order characteristic is the continuous increase in crustal velocities westward from the foreland belt to the insular belt the variations do not correlate with the morphogeological belts they do correspond with large scale geological and or

the role of early formed structures on the development of the world class st ives goldfield yilgarn wa a revised structural interpretation for the victory to kambalda area of the world class st ives goldfield in the archean yilgarn craton has mapped out the distribution of wnw trending faults within this area of the field these previously cryptic wnw trending structures had been identified in gravity data and also by isopach thickness variations the wnw trending faults acted as transfers syn gold mineralization although only discrete segments of these faults were active during the main stage of gold mineralization where mineralized the faults transferred strain from a complex combination of block on block movement associated with thrusting and strike slip movement on nw and n trending faults along some segments n trending mineralized faults terminate against the wnw trending faults many of the wnw trending faults correlate with major strike changes on regional and camp scale faults and they are domain boundaries for the critical n trending fault segments that host high grade gold within contractional jogs the wnw trending faults also show evidence for an older deformation history prior to main stage gold which may extend back to early basin development associated with ultramafic and mafic volcanism they are inferred to have been a series of early wnw trending normal faults and breached relay ramps associated with oblique rifting along an older nnw trending basement boundary

use of immobile trace elements in gold exploration in the neoarchean sandstone greenstone belt yilgarn block western australia exploration in the sandstone greenstone belt ssgb with its widespread complex regolith cover is extremely difficult as targeted orogenic gold deposits have no consistent parameters that allow direct geophysical detection and gold and ore metal surface geochemistry reflects variations from in situ to highly transported responses based on aeromagnetic interpretations the gold deposits of the ssgb can be viewed within broad litho structural frameworks and nnw nw and nne ne trending domains with more favourable orientation with respect to the inferred principal maximum stress during the time of gold mineralisation can be defined fault jogs and high angle corridors of cross faults further constrain more prospective zones however the aeromagnetic data cannot identify relatively small volumes of critical host rocks which can localize ore fluid flux and fluid rock reactions that control the deposition of gold mineralisation in the ssgb these critical host rocks include thin granodiorite intrusions within ultramafic schists or specific mafic bodies in mafic ultramafic sequences a reconnaissance study using the immobile trace elements ti and zr demonstrates that these critical rock types can be readily recognized at surface and in drill chips in particular ti zr geochemistry identifies previously unknown 20 km long differentiated dolerite units with granophyric zones that localize gold mineralisation a combination of aeromagnetic interpretation of structures and major domains plus the location of critical host units using ti zr geochemistry allows production of an exploration targeting map for this district with definition of priority targets based on a mineral system approach thus in the ssgb for gold exploration under regolith cover that represents in situ weathering of those host rocks rather than later cover sequences immobile trace element geochemistry provides an effective low cost methodology as an adjunct to conventional ore metal geochemistry and should be used in other orogenic gold provinces worldwide

provenance analysis of olivella biplicata shell beads from the california and oregon coast by stable isotope fingerprinting while olivella beads are a common component of archaeological sites in california and were widely traded in prehistory no method has been developed to trace individual beads to a point of origin this study examines the potential of stable carbon and oxygen isotopes to source olivella beads from the pacific coast the study shows that 1 the oxygen isotopic composition of modern olivella biplicata shells faithfully varies with ambient sea surface temperature and local upwelling lending themselves to sourcing studies 2 oxygen isotope ratios in modern shells can be used to identify shells that grow north versus south of point conception california and 3 shell carbon isotope ratios may further subdivide these two regions into more spatially restricted source zones analyses on a small sample of 10 beads found at various archaeological sites within the interior of california suggest that all were made in southern california

on thrusting regional unconformities and exhumation of high grade greenstones in neoarchean orogens the case of the waroonga shear zone yilgarn craton abstract during the neoarchean the dominant tectonic style progressively changed from an episodic overturn stagnant lid regime to modern style plate tectonics the neoarchean strengthening of continental lithosphere changed the style of deformation of orogenic belts the case study presented here provides insights into how such transition in tectonic style occurred a matter that is generally controversial we present structural and metamorphic data from the c 2660 ma waroonga shear zone wsz in the neoarchean yilgarn orogen western australia the wsz contains a syntectonic pluton and older high grade greenstones the tectonic fabric in the pluton developed during melt present thrusting followed by syn cooling wrench dominated transpression mafic greenstones preserve three metamorphic assemblages the m1 assemblage grt cpx qtz records peak p t conditions of 12 1 kbar and 800 50 c followed by isothermal decompression to 9 kbar m2 these anhydrous assemblages might predate the wsz greenstones then underwent decompression at c 2660 ma 3 4 kbar 600 650 c defined by the amphibole rich m3 assemblage synkinematic with the tectonic fabric in the wsz we show that shearing along the wsz exhumed these greenstones by at least 10 km inducing major uplift and erosion archean accretionary orogens developed on weak lithosphere where deformation suppressed crustal thickening orogenic relief and synorogenic exhumation of orogenic roots however our study indicates a genetic link between i strain localization along contractional structures inducing large scale uplift ii exhumation of high grade greenstones iii development of inverse metamorphic gradients iv establishment of a regional unconformity with clastic sediments fed by the uplifted terrane v incorporation of portions of the newly formed orogenic basins into the footwall of the wsz these features imply that the yilgarn orogenic lithosphere at c 2660 ma was stiff enough to allow tectonic processes analogous to those that dominate modern style orogenic belts representing an intermediate stage between archean and modern type orogens

proximal to distal sedimentological variation in a linear turbidite trough implications for the fan model determination of geographically dependent sedimentological variation proximality in ancient flysch deposits formed an important part of early turbidite studies attempts to quantify this variation highlighted anomalies which were neatly resolved by application of vertical sequence analysis and the use of fan models however there are many turbidite formations such as the lower cretaceous cumberland bay formation cbf of south georgia which cannot be described in terms of existing fan models but show strong proximal to distal sedimentological changes the cbf is a thick sequence of volcaniclastic sandstone turbidites deposited in a linear back arc basin principally by currents flowing wnw parallel to the basin margin four lithofacies associations are recognized on the basis of sandstone shale ratio the two finergrained associations are constant in character across the cbf outcrop in the coarse grained associations there is a change in character wnw down the palaeocurrent direction this is brought out by decreasing sandstone bed thickness and percentage amalgamation but these changes are not always marked or consistent in contrast the internal character of the sandstone beds changes strongly with a marked proportional increase in tb and tc divisions within the bed downcurrent the evidence suggests that the system was aggradational rather than progradational tectonic control of the basin margins prevented major migration of the depositional system and most areas remained in the same position relative to source through time comparison of the cbf with other turbidite formations suggests two end member states which will produce radically different vertical sequences progradational systems will produce strong vertical facies changes where beds deposited in distal environments are overlain by beds deposited in environments progressively nearer source however there will be no lateral change in the character of any particular facies type in contrast in aggradational systems the major sedimentological variation will be lateral rather than vertical

a time series audit of zipf s law as a measure of terrane endowment and maturity in mineral exploration controversy has surrounded the application of zipf s law as a potential exploration tool since it was first proposed by folinsbee in 1977 the current study empirically assesses with the wisdom of hindsight the realism of predictions that could have been made at various times in the past about the number and size of lode gold deposits yet to be discovered in the archean yilgarn craton of western australia the size distribution of gold deposits predicted by the zipf curve at any point in time represents an estimate of the original natural endowment for this terrane based on the knowledge available at the time predicted gold deposits not matched by known deposits by contrast represent the residual endowment for deposits yet to be discovered the study concludes that a zipf curve based on the size distribution of gold deposits known in 1973 1989 2003 and 2008 would have provided remarkably realistic predictions of the size and number of the gold deposits that were discovered subsequently or of the degree to which known deposits have grown in size in subsequent years as a result of better delineation because lode gold orebodies are notoriously difficult to fully delineate and their resources tend to grow with time initial zipf predictions generally prove conservative predictions are particularly sensitive to the accuracy of the resource inventory of the largest rank 1 deposit on which the zipf curve is based in our case the kalgoorlie golden mile which has virtually doubled in size during the period covered by the study from 36 to 72 moz of contained gold nevertheless the degree of exploration maturity could have consistently been estimated with a high degree of accuracy as 17 percent of predicted gold endowment discovered in 1973 33 percent in 1989 62 5 percent in 2003 and 75 percent in 2008 in conclusion application of zipf s law would have represented an effective motivator to embark into a well resourced gold exploration campaign in the yilgarn craton

late archaean synorogenic basins of the eastern goldfields superterrane yilgarn craton western australia part iii signatures of tectonic escape in an arc continent collision zone abstract siliciclastic supersequences in the eastern goldfields superterrane are remnants of basins that were linear zones of subsidence between intra terrane faults fluvial deposits record proximal to medial braid plains deep marine canyon and fan deposits were linked across intra terrane compartments only by mud rich deposits axial depositional systems dominate with only minor evidence for slope aprons although transverse and axial systems are preserved in some fluvial deposits basin development occurred during two stages separated by an inversion event with the kalgoorlie terrane recording change from a fluvial to a deep marine basin and the kurnalpi terrane change from distal to proximal deep marine facies tracts sparse palaeocurrents establish that uplift to the north controlled sediment dispersal lithofacies stacking is aggradational whereas abrupt upwards change in facies tracts is back stepping within depositional sequences and between depositional sequence sets but forward stepping between depositional sequences the stratigraphic architecture is atypical of synorogenic basins but consistent with a strike slip regime characterised by pulsed uplift subsidence steady state basin lengthening and subsidence punctuating catastrophic subsidence and lengthening and tectonic anchoring the basins are interpreted to have been similar to graben and half graben of the western anatolian extensional province of turkey with linear zones of subsidence developing adjacent to strike slip oblique slip or normal dip slip faults controls on stratigraphic patterns are considered to have been regional rather than at the scale of each basin the envisaged tectonic setting is similar to projected collision between the philippine archipelago west of the philippine fault and continental crust of the south china sea but the orogenic architecture is similar to that of accreted superterranes in the canadian cordillera interpreted north or northwest convergence between the burtville terrane to the east and the ancestral yilgarn continent to the northwest produced a south propagating orogen with the kalgoorlie gindalbie and kurnalpi terranes trapped between in a tectonic escape corridor tectonic escape to the south between bounding strike slip faults produced back stepping of facies tracts that simulated basin lengthening whereas forward stepping of facies tracts was the response to south propagating uplift

through the high rock and beyond placing the last supper cave and parman paleoindian lithic assemblages into a regional context based on source provenance data derived from paleoindian artifacts in the great basin most researchers agree that early groups were mobile and far ranging however current explanations of the behavior reflected by those data differ some models portray paleoindians as residentially mobile foragers while others portray them as wetland tethered collectors reliant upon logistical forays we consider the types of hunter gatherer behavior that could produce trends in the x ray fluorescence data from three paleoindian assemblages in northwest nevada where abundant high quality obsidian essentially allows us to hold the effects of raw material availability constant between sites we conclude that while it is difficult to differentiate between residential and logistical mobility using technological and sourcing data alone we can nevertheless begin to understand the relative time averaged importance of particular locations on the landscape and why such places attracted paleoindians

earthquake forecasting in southern italy on the basis of logistic models abstract the interrelation between the seismic activity of the southern apennines and southern dinarides mantovani et al 1987 seems to be characterized by a proportionality between the magnitude of the dinaric precursors and the probability of occurrence of a shock of m 5 0 in the apennines logistic models are used to define in a quantitative way this relationship and to estimate its statistical significance the good agreement between the observed data and the obtained relationship is an indication of the reliability of this model for earthquake forecasting purposes

ams radiocarbon dating and shell bead chronologies middle holocene trade and interaction in western north america direct ams radiocarbon dating can be used effectively to examine the stylistic evolution of shell beads and ornaments requiring only a small amount of shell this technique has the potential to test and refine bead chronologies that were developed before radiocarbon dating as an example eight olivella grooved rectangle ogr beads collected from archaeological sites throughout western north america were dated using the ams technique the results produced a consistent suite of dates clustering between 4400 and 5400 cybp most ogr beads come from the california channel islands where they are found in a variety of contexts and exhibit a high degree of stylistic variation on the mainland they are found most commonly in large coastal villages and in sites along natural corridors through the transverse ranges and the great basin ogr beads are recovered almost exclusively within the historic territories of uto aztecan speaking peoples which may indicate possible ethnic or linguistic connections this example serves to illustrate how ams radiocarbon dating can be used to test and refine artifact typologies and classificatory schemes

late kinematic timing of orogenic gold deposits and significance for computer based exploration techniques with emphasis on the yilgarn block western australia abstract orogenic gold deposits are a widespread coherent group of epigenetic ore deposits that are sited in accretionary or collisional orogens they formed over a large crustal depth range from deep seated low salinity h2o co2 ch4 n2 ore fluids and with au transported as thio complexes regional structures provide the main control on deposit distribution in many terranes first order faults or shear zones appear to have controlled regional fluid flow with greatest ore fluid fluxes in and adjacent to lower order faults shear zones and or large folds highly competent and or chemically reactive rocks are the most common hosts to the larger deposits focusing of supralithostatic ore fluids into dilatant zones appears to occur late during the evolutionary history of the host terranes normally within d3 or d4 in a d1 d4 deformation sequence reactivation of suitably oriented pre existing structures during a change in far field stress orientation is a factor common to many deposits and repeated reactivation may account for multiple mineralization episodes in some larger deposits absolute robust ages of mineralization support their late kinematic timing and in general suggest that deposits formed diachronously towards the end of the 100 to 200 m y long evolutionary history of hosting orogens for example in the yilgarn block a region specifically emphasised in this study orogenic gold deposits formed in the time interval between 40 and 90 m y with most about 60 to 70 m y after the youngest widespread basic ultrabasic volcanism and towards the end of felsic magmatism the late timing of orogenic gold deposits is pivotal to geologically based exploration methodologies this is because the present structural geometries of i the deposits ii the hosting goldfields and iii the enclosing terranes are all essentially similar to those during gold mineralization at least in their relative position to each other thus interpretation of geological maps and cross sections and three dimensional models can be used to accurately simulate the physical conditions that existed at the time of ore deposition it is particularly significant that the deposits are commonly related to repetitive and predictable geometries such as structural heterogeneities within or adjacent to first order structures around rigid granitoid bodies or in specific locked up fold thrust structures importantly the two giant greenstone hosted goldfields kalgoorlie and timmins show a remarkably similar geometry at the regional scale computer based stress mapping and gis based prospectivity mapping are two computer based quantitative methodologies that can utilize and take advantage of the late timing aspect of this deposit type to provide important geological aids in exploration both in broad regions and more localized goldfields both require an accurate and consistent solid geology map stress mapping requires knowledge of the far field stresses during mineralization and the empirical prospectivity mapping requires data from a significant number of known deposits in the terrane the kalgoorlie terrane in the yilgarn block meets these criteria and illustrates the potential of these methodologies in the exploration for orogenic gold deposits low minimum stress anomalies interpreted to represent dilational zones during gold related deformation coincide well with the positions of known goldfields rather than individual gold deposits in the terrane and there are additional as yet unexplained anomalies the prospectivity analysis confirms that predictable and repetitive factors controlling the siting of deposits are i proximity to and orientation and curvature of granitoid greenstone contacts ii proximity to segments of crustal faults which strike in a preferred direction iii proximity to specific lithological contacts which have similar preferred strike iv proximity to anticlinal structures and v the presence of preferred reactive host rocks e g dolerite the prospectivity map defines a series of anomalous areas which broadly conform to those of the stress map 78 correspondence the most prospective category on this map covers less than 0 3 of the greenstone belts and yet hosts 16 of the known deposits which have produced 80 of known gold thus it discriminates in favour of the larger economically more attractive deposits in the terrane the successful application of stress mapping and prospectivity mapping to geology based exploration for orogenic gold deposits indicates that more quantitative analysis of geological map data is a profitable line of research the computer based nature of these methodologies is ideal for the production of an ultimate integrated deposit target map which can be compared to other more conventional targeting parameters such as geophysical and geochemical anomalies such an integrated strategy appears the way forward in the increasingly difficult task of cost effective global exploration for orogenic gold deposits in poorly exposed terranes

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

entering an immature exploration search space assessment of the potential orogenic gold endowment of the sandstone greenstone belt yilgarn craton by application of zipf s law and comparison with the adjacent agnew goldfield abstract the sandstone greenstone belt is an exploration immature regolith covered approximately 1000 sq km belt in the southern cross domain of the yilgarn craton in order to estimate potential endowment historical gold production and deposit resource estimates are required to be quantitatively analysed for calculation of natural and residual gold endowment the total residual gold endowment within the oxide zone of the sandstone greenstone belt is estimated by application of a zipf s law statistical assessment to be 2 3 moz this mineralisation is most likely contained in extensions of known deposits and several undiscovered deposits the fresh rock of the sandstone greenstone belt remains poorly explored however a conceptual endowment estimate can be made based on a minerals system comparison between the exploration immature sandstone greenstone belt and the well explored geologically similar agnew greenstone belt 100 km to the east it is possible that natural endowment at sandstone could total 21 3 moz with nine undiscovered deposits of 0 5 moz application of such a minerals system integrated endowment assessment represents an effective motivator to embark on a well resourced gold exploration campaign in the sandstone greenstone belt a currently immature exploration search space

gold mineralisation throughout about 45 ma of archaean orogenesis protracted flux of gold in the golden mile yilgarn craton western australia the golden mile deposit was discovered in 1893 and represents today the largest archaean orogenic lode gold system in the world 50 m oz produced gold the golden mile deposit comprises three major styles of gold mineralisation fimiston oroya and charlotte styles fimiston style lodes formed at 250 to 350 c and 100 to 200 mpa and are controlled by brittle ductile fault zones their subsidiary fault zone and vein networks including breccias and open cavity infill textures and hydrothermally altered wall rock fimiston lodes were formed late d1 prior to d2 regional upright folding hydrothermal alteration haloes comprise a progression toward the lode of diminishing chlorite an increase in sericite and in fe content of carbonates lodes contain siderite pyrite native gold 17 different telluride minerals au ag tellurides contain 25 of total gold tourmaline haematite sericite and v rich muscovite oroya style lodes formed at similar p t conditions as the fimiston lodes and are controlled by brittle ductile shear zones associated dilational jogs that are particularly well developed at the contact between paringa basalt and black shale interflow sedimentary rocks and altered wall rock the orebodies are characterised by micro breccias and zones of intense shear zone foliation very high gold grades up to 100 000 g t au and the common association of tellurides and vanadian mica green leader oroya lodes crosscut fimiston lodes and are interpreted to have formed slightly later than fimiston lodes as part of one evolving hydrothermal system spanning d1 and d2 deformation ca 2 675 2 660 ma charlotte style lodes exemplified by the mt charlotte deposit are controlled by a sheeted vein stockwork complex of north dipping quartz veins and hydrothermally altered wall rock the mt charlotte orebody formed at 120 to 440 c and 150 to 250 mpa during movement along closely spaced d4 2 625 ma and reactivated d2 faults with the quartz granophyre in the golden mile dolerite exerting a strong lithological control on gold mineralisation veins consist of quartz carbonate minor scheelite and wall rock alteration comprises chlorite destruction and growth of ferroan carbonate sericite pyrite native gold pyrite pyrrhotite is zoned on the scale of vein haloes and of the entire mine giving a vertical temperature gradient of 50 100 c over 1 000 vertical metres the structural hydrothermal model proposed consists of four major stages 1 d1 thrusting and formation of fimiston style lodes 2 d2 reverse faulting and formation of oroya style lodes 3 d3 faulting and dissecting of fimiston and oroya style lodes and 4 d4 faulting and formation of mt charlotte style sheeted quartz vein system the giant accumulation of gold in the golden mile deposit was formed due to protracted gold mineralisation throughout episodes of an archaean orogeny that spanned about 45 ma fluid conduits formed early in the tectonic history and persisted throughout orogenesis with the plumbing system showing a rare high degree of focussing efficiency and duration in addition to the long lasting fluid plumbing system the wide variety of transient structural and geochemical traps multiple fluid sources and precipitation mechanism contributed towards the richest golden mile in the world

estimation of the probability of earthquake occurrence on the basis of logistic models high probability of an earthquake of m 6 5 near the arc junction off northeast japan the probability of the occurrence of an earthquake of m 6 5 is estimated by applying logistic models to seismicity in the hokkaido tohoku region northeast japan it is found that the probability of an earthquake occurrence near the arc junction off northeast japan is high when a specific seismicity pattern appears that is seismic activity increases 7 10 years or decreases 3 6 years before an event of m 6 5 because seismic activity is currently extremely low near the arc junction it is possible that an earthquake of m 6 5 may occur there within a few years specifically the probability estimated on the basis of logistic models is higher than 0 9 for the year of 1988

the crustal continuum model for late archaean lode gold deposits of the yilgarn block western australia most archaean gold ores belong to a coherent genetic group of structurally controlled lode deposits that are characteristically enriched in au with variable enrichments in ag as w sb bi te b and pb but rarely cu or zn and are surrounded by wallrock alteration haloes enriched in k lile and co2 with variable na and or ca addition evidence from the yilgarn block of western australia combined with similar evidence from canada and elsewhere indicates that such deposits represent a crustal continuum that formed under a variety of crustal regimes over at least a 15 km crustal profile at pt conditions ranging from 180 c at 1 kb to 700 c at 5 kb individual deposits separated by tens to hundreds of kilometres collectively show transitional variations in structural style of mineralisation vein textures and mineralogy of wallrock alteration that relate to the pt conditions of their formation at varying crustal depths specific transitions within the total spectrum may be shown also by deposits within gold camps although nowhere is the entire continuum of deposits recorded from a single gold camp or even greenstone belt

structural variety and tectonic evolution of strike slip basins related to the philippine fault system northern luzon philippines the northern part of the philippine fault zone in luzon corresponds to a complex braided system of left lateral strike slip faults the nw oriented main active branch which emerges from the philippine sea splits into an array of north striking splays responsible for the tectonic evolution of the central cordillera this complex fault pattern has favored local stress field variations strike slip basins have evolved in this framework along or in the vicinity of the main splays of the philippine fault apart from the classical pull apart tectonics on a releasing fault termination overlap or bend we describe other mechanisms such as the strike slip tilting or the warping of a strip limited by two strike slip faults the strike slip basins are good recorders of the evolution of the philippine fault system those located along the north striking cordilleran faults individualized in late early pliocene to pleistocene time when the present day philippine fault initiated but their main control is the fault shape acquired in upper middle miocene time the recent tectonic evolution of the fault system is best recorded in central luzon where the active basins trace an asymmetrical v shape with the longest branch trending ne parallel to the east luzon trough and the shortest one trending nw related to the philippine fault both the fault pattern and the basin distribution demonstrate the influence of the benham rise in the tectonic evolution of luzon the structural setting is interpreted as the result of an early miocene collision event between the benham rise and the eastern margin of luzon and subsequent inception of the nw striking strand of the philippine fault the present locations of the basins result from the interaction between the structural heritage and the present day regional plate motion

geology mineralogy and geochemistry of magnetite associated au mineralization of the ultramafic basalt greenstone hosted crusader complex agnew gold camp eastern yilgarn craton western australia a late archean intrusion related au deposit abstract the crusader complex part of the agnew gold camp of the lawlers anticline of the yilgarn craton western australia is located close to or along the contact between the lawlers basalt and agnew ultramafics units au mineralization within the four orebodies that form the crusader complex is dominated by very pure au containing less than 1 wt ag with au variably associated with scheelite bi tellurides and minor chalcopyrite within a magnetite and titanite gangue assemblage hydrothermal alteration associated with this style of mineralization is characterized by increasing concentrations of mo be li sn and fe and depletions in na cu ba pb mn zn si and k relative to protolith concentrations these enrichments are more typical in orebodies associated with felsic intrusive related mineralizing systems rather than the more well known orogenic au deposits found elsewhere within the lawlers anticline e g at waroonga and within the greater yilgarn craton we propose that flexures of the contact between the lawlers basalt and agnew ultramafic units acted as conduits for au bearing felsic intrusive derived fluids and generated structural traps that enhanced fluid flow the mineralizing fluids that formed the crusader deposits were derived from the lawlers granitoid pluton that intruded into the study area enhanced fluid flow promoted interaction between hydrothermal fluids and the reactive mafic ultramafic rock sequence augmenting the amount of au that was precipitated during formation of the orebodies at crusader the magnetite dominated quartz and sulfide poor intrusion related mineralization at crusader contrasts sharply with other late archean intrusion related deposits of the yilgarn craton that are usually sulfide and or quartz rich this may in turn suggest that the crusader deposit represents a new class of under explored intrusion derived deposits possibly opening new mineral exploration opportunities for the agnew region and potentially the wider eastern goldfields superterrane enrichments in mo and sn and significant depletions in cu suggest that other parts of the lawlers batholith may also be prospective for base metal mineralization integration of stratigraphic interpretation with the identification of key structural fluid pathways and the presence of felsic intrusive bodies as presented in this study enables the delineation of the key elements that underlie mineralization at the crusader complex we propose that these key elements provide vital information for future gold exploration models that can be used within other archean terranes and within the eastern yilgarn craton in particular