changes in coral reef structure through the miocene in the mediterranean province adaptive versus environmental influence well documented mediterranean examples of miocene carbonate platforms with complete exposures from shallow water to basinal facies provide evidence for temporal changes in reef building capacity of zooxanthellate corals in pre late tortonian platforms small coralgal patches and mounds occur from platform top to the toe of slope but they did not build to sea level in contrast barrier reefs with unequivocal reef crest structures that reached sea level are documented in late tortonian early messinian platforms we suggest that a change in both calcification rates and bathymetric zonation was the result of coevolution of corals and symbiodinium zooxanthellae coeval to global cooling and at least at a regional scale a geochemical change that supported widespread aragonite precipitation through the late miocene

do seismic reflections necessarily have chronostratigraphic significance many seismic reflections from within sedimentary successions are thought to be generated along stratal surfaces because those surfaces are laterally continuous and have marked acoustic impedance contrasts as stratal surfaces are isochronous those reflections are then also taken as being chronostratigraphically significant in contrast seismic reflections are thought not to be generated along the boundaries of lithostratigraphic units because those boundaries are discontinuous and gradational nevertheless synthetic seismic analysis shows that seismic reflections should in many circumstances be expected to follow lithostratigraphic unit boundaries not stratal surfaces as these lithostratigraphic unit boundaries will generally be diachronous seismic reflections from within sedimentary successions should evidently not be treated as necessarily having chronostratigraphic significance

hiatal duration of correlative sequence boundaries from oligocene pliocene mixed carbonate siliciclastic sediments of the south florida platform abstract sequence boundaries defined by regional unconformities in mixed carbonate siliciclastic sediments have a variable duration from the margin to the interior of the florida platform factors controlling the timing and duration of these unconformities include a combination of global eustatic and regional mechanisms sediment supply current intensification integrated chronostratigraphies developed from a transect of continuous cores in the south central interior to the southern margin of the florida platform show an increase in duration of the hiatal gaps along correlative sequence boundaries toward the platform edge two sequence boundaries are correlated across the south florida platform and mark formation contacts the lower sequence boundary sb a marks the suwannee limestone arcadia formation contact and is of significantly less duration in the platform interior southwest peninsular florida 2 0 m y than at the south platform margin middle florida keys 8 1 m y the hiatal gap along the upper sequence boundary sb b marking the arcadia formation overlain by miocene pliocene sediments that vary in age and composition regionally records the same increase from the central part of the platform southwest florida arcadia fm peace river fm 1 6 m y to the south platform edge lower florida keys arcadia fm stock island fm 11 5 m y eustatic fluctuations affected the relative sedimentation rates of the mixed sediments in the platform interior and at the margin most notably the large eustatic fall at the end of the early oligocene terminated carbonate deposition of the suwannee limestone sb a sediment accumulation on the platform interior was more temporally continuous than at the margin because of greater siliciclastic input from the north the strengthening of marine currents beginning in the middle miocene limited sediment accumulation across the southern platform margin sb b and possibly caused erosion of the margin carbonates increasing the duration of the hiatal gap on top of the arcadia formation

a review of cenozoic evolution of the southeastern united states atlantic coast north of the georgia trough abstract from late eocene or oligocene to the present the pattern of cyclic sediment deposition on the atlantic coastal plain of the southeastern united states is the product of 1 a relatively stable trailing edge continental margin with gentle downwarping 2 deposition of siliciclastics by major appalachian mountain and piedmont draining rivers and shelf generated carbonates 3 a humid temperate to subtropical climate 4 a mesotidal coast with moderate wave energy and periodic tropical storms 5 dominant longshore drift towards the southwest 6 a history of sea level change that was moderately submergent from late cretaceous through late eocene or oligocene and mildly emergent during the neogene intermittent fluctuations in sea level up to 100 m in the neogene subdivide the stratigraphy as unconformities during the late oligocene through holocene but are less pronounced in the paleogene each of these six factors has influenced the geomorphology sedimentation stratigraphy petrology and geometry of the cenozoic sedimentary units and the diversity of surficial quaternary coastal deposits during the quaternary sea level change would have been produced by glacial interglacial cycles the late eocene oligocene to early miocene and the late miocene transition experienced a major sea level decline influenced by ice cap formation in addition to climatic cycle induced sea level fluctuations

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

evolution of a deep water carbonate platform upper cretaceous to pleistocene sedimentary environments on the west florida margin abstract deep water carbonates have been accumulating on the west florida margin since the early late cretaceous although the depositional style and sediment types have changed through time seven coreholes drilled by exxon record the establishment of two gently dipping aggradational ramps the first in the late cretaceous to oligocene and the second in the middle to late miocene to the present these dominantly pelagic depositional environments followed episodes of downslope transport of shallow water grains diluting background pelagic sedimentation and producing progradational ramps that built seaward this study traces the evolution of the deep water west florida sedimentary systems and contrasts the older aggradational ramp characterized by both foraminiferal and radiolarian oozes as well as volcanic ash with the late neogene ramp whose biogenic components are mainly foraminifera and coccoliths the cycles of progradation separated by periods of ramp aggradation developed as eustasy interacted with prolonged subsidence of the margin early late cretaceous as well as oceanographic changes caused by closure of the suwannee strait late oligocene to early miocene and of the isthmus of panama middle to late miocene the major transitions in environments recorded in the west florida ramp platform thus resulted from the superposition of climatic tectonic and oceanographic events on global sea level changes

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

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

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

stratigraphic and palaeoenvironmental summary of the south east georgia embayment a correlation of exploratory wells a continental offshore stratigraphic test cost well and six exploratory wells have been drilled in the south east georgia embayment the oldest rocks penetrated are weakly metamorphosed lower ordovician quartz arenites and silurian shales and argillites in the transco 1005 1 well and upper devonian argillites in the cost ge 1 well these marine strata which are equivalent to the tippecanoe sequence in florida underlie the post rift unconformity and represent part of a disjunct fragment of gondwana that was sutured to the north american craton during the late palaeozoic alleghanian orogeny the palaeozoic strata are unconformably overlain by interbedded non marine jurassic bajocian and younger sandstones and shales and marginal marine lower cretaceous sandstones calcareous shales and carbonates which contain scattered beds of coal and evaporite together these rocks are stratigraphically equivalent to the onshore fort pierce and cotton valley formations and rocks of the lower cretaceous comanchean provincial series the abundance of carbonates and evaporites in this interval which reflects marine influences within the embayment increases upwards eastwards and southwards the upper cretaceous part of the section is composed mainly of neritic calcareous shales and shaley limestones stratigraphically equivalent to the primarily marginal marine facies of the onshore atkinson cape fear and middendorf formations and black creek group and to limestones and shales of the lawson limestone and peedee formations cenozoic strata are primarily semiconsolidated marine carbonates palaeocene to middle eocene strata are commonly cherty middle miocene to pliocene strata are massive and locally phosphatic and glauconitic quaternary sediments are dominated by unconsolidated carbonate sands the effects of eustatic changes and shifts in the palaeocirculation are recorded in the upper cretaceous and tertiary strata

gulf trough the atlantic connection analyses of seismic reflection profiles and stratigraphic data indicate a continuation of the gulf trough trend across eastern south carolina and offshore between cape fear and cape hatteras north carolina seismic profiles show a linear northeast trending zone of nondeposition and erosion and areas of chaotic deposition in the eocene and oligocene sections the character of deposition and erosion along this trend is similar to that produced by bottom currents under the core of the present gulf stream the trend separates deep water from shallower water deposits indicating that the erosion was produced by strong marine currents flowing through the gulf trough in the high sea levels of middle eocene through early oligocene time

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

continental shelf landscapes of the southeastern united states since the last interglacial abstract the wide sediment starved continental shelf and modern coastal areas of the southeastern united states retain well preserved but scattered remnants of a submerged paleolandscape this paper presents a conceptual model of stratigraphic deposition and landscape formation since the last interglacial on the continental shelf of south carolina with portions of north carolina georgia and florida usa data for this study include multibeam bathymetry surveys sidescan sonar mosaics high resolution subbottom profiles and ground truth surveys from 250 m to the modern tidewater region four bathymetric zones are recognized with eleven landforms and landform indicators the described zones range in depths from the modern shoreline across the shelf and over the shelf edge to 250 m msl relative sea level curves are presented for the area and discussed in conjunction with cultural and climatic events the potential for preservation of paleoamerican sites is high at the shelf edge between 130 m and 45 m with archaic and later occupations likely in depths of less than 25 m prominent vantage points for paleoamericans 11 kya would have existed at the shelf edge and tidewater resources would have been available nearby for a period of almost 6 ka rapid transgression rates 60 km ka after the sea level rose over the shelf edge make preservation of tidewater sites less likely on the outer and middle shelf searches for the earliest paleoamericans should focus on promontories at the edge of the shelf and along future discoveries of paleoincisions on the shelf mapping and delineating this paleolandscape and associated unconsolidated sedimentary deposits interspersed with rocky plains and ledges will continue to be a priority to marine archeologists coastal managers fishery scientists and marine spatial planners over the next several decades

the west central florida inner shelf and coastal system a geologic conceptual overview and introduction to the special issue abstract this paper provides an overview for this special publication on the geologic framework of the inner shelf and coastal zone of west central florida this is a significant geologic setting in that it lies at the center of an ancient carbonate platform facing an enormous ramp that has exerted large scale control on coastal geomorphology the availability of sediments and the level of wave energy in order to understand the holocene geologic history of this depositional system a regional study defined by natural boundaries north end of a barrier island to the apex of a headland was undertaken by a group of government and university coastal geologists using a wide variety of laboratory and field techniques it is the purpose of this introductory paper to define the character of this coastal inner shelf system provide a historical geologic perspective and background of environmental information define the overall database present the collective objectives of this regional study and very briefly present the main aspects of each contribution specific conclusions are presented at the end of each paper composing this volume

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

estimating mediterranean oligocene miocene sea surface temperatures an approach based on coral taxonomic richness abstract during the oligocene and miocene shallow water carbonates of the mediterranean region were rich in scleractinian corals thriving within various depositional settings including different reef types their diversity patterns although related to a complex interplay between a suite of environmental factors and palaeobiogeography are considered to be strongly controlled by climate variability and changes in sea surface water temperature by using the quantitative relationship between present day coral taxonomic richness and prevailing sea water temperature underlined by the so called energy hypothesis we test zooxanthellate coral generic richness values from a selection of 102 oligocene miocene localities of the mediterranean region as a proxy for relative palaeotemperatures for each oligocene miocene stage generic richness values per z coral site are firstly examined together with variations of the mediterranean z coral generic pool for better testing the method and assessing its potential application patterns of generic richness and inferred palaeotemperatures are then compared with global palaeoclimatic curves based on marine oxygen stable isotopes data or other climate proxies such as palaeoclimatic records from european continental floras and from fossil coral linear extension rate results clearly show that fluctuations of coral richness derived palaeotemperatures correspond relatively well with global changes of sea water temperature especially for the entire oligocene the chattian aquitanian boundary and the late miocene the well known mid miocene climatic optimum however is not recorded suggesting that regional factors acting together with important palaeogeographical changes exerted a strong control on the generic richness of mediterranean z coral communities a remarkable decline of taxonomic richness is recorded after the burdigalian together with a gradual decrease of palaeotemperatures in the region from the middle miocene onwards to the messinian however an increase in the temperature range of z coral localities is clearly visible indicating that z coral communities were able to thrive and adapt to a wider temperature range as the mediterranean was gradually migrating northwards outside the tropical belt the energy hypothesis if used at global or regional scale can be considered a promising and reliable method for estimating cenozoic palaeotemperatures from coral or other suitable fossil assemblages of shallow water carbonates

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

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

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

seismic stratigraphy and geologic history of middle cretaceous through cenozoic rocks southern straits of florida multifold and singlefold seismic data and indirect ties to industry wells and deep sea drilling program and ocean drilling program sites are used to study the middle cretaceous to cenozoic history of the southern straits of florida since the late albian the southern straits of florida has evolved from a shallow water platform to a deep water trough this evolution is related in part to late albian middle cenomanian drowning and segmentation of a shallow water carbonate megabank which extended across the region since the late cretaceous shallow water deposition has continued around cay sal bank and along the southern margin of the south florida basin while deeper water deposition has persisted elsewhere evolution of the straits of florida is also related to late cretaceous middle eocene convergence between the north american and caribbean plates regional dip towards the cuban fold and thrust belt suggests that the southern straits of florida is an extension of the north cuban foreland basin a paleo florida current became active during the early paleocene along the northern limb of this foreland basin during this time the southern straits of florida was still relatively shallow and bottom currents persisted over most of the region rapid subsidence during the late eocene caused a change in depositional regimes from current dominated to predominantly pelagic hemipelagic sedimentation since the late eocene the florida current has influenced deposition only in the shallower parts f the southern straits of florida

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

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

orbitally controlled oscillations in planktic communities and cyclic changes in western mediterranean hydrography during the messinian we use quantitative analyses of the planktic foraminiferal assemblages and stable isotope analyses of the sorbas section in the western mediterranean to reconstruct the cyclical changes in surface and deep water hydrographic conditions during the late miocene prior to the messinian salinity crisis oscillations in winter and summer temperatures linked to cyclical fluctuations in the hydrographic conditions and nutrient availability were the main mechanisms driving the cyclical changes in the planktic foraminiferal assemblages during the messinian the winter intensification and southward expansion of the northern cool and dry winds during precession maxima lowered sea surface temperatures below 14 15 c favoring water convection and the upward mixing of nutrients with the consequent increase in the proportion of cold eutrophic water foraminifera the low summer temperatures below 24 c inhibited the growth of warm oligotrophic water foraminifera as occurs today in the mediterranean by contrast at times of precession minima the low influence of the high latitude air masses caused winter temperatures to remain relatively high which combined with the lower surface salinities led to the formation of a permanent pycnocline winter conditions prevented the growth of cold eutrophic water foraminifera while high summer temperatures and the formation of a permanent pycnocline stimulated the growth of warm oligotrophic water foraminifera the prevalence of stable water stratification during winter due to the large density gradient between the surface and intermediate waters prevented deep water formation and slowed down the rates of oxygen supply to the bottom resulting in the formation of the sapropels a sharp decrease in 13c of benthic and planktic foraminifera that occurred between 6 8 and 6 7 myr is related to an increase in the residence time of mediterranean waters because similar changes have been observed in other regions of the mediterranean we conclude that this change records a significant reduction in the atlantic mediterranean water exchange at that time mediterranean climatic amplification increased throughout the messinian as the atlantic mediterranean water exchange was progressively more limited and oscillations in the ratio of planktic benthic foraminifera and of warm oligotrophic cold eutrophic species are good records of this increasing amplification which culminated at 5 95 myr with the deposition of gypsum pelitic layers that mark the onset of the messinian salinity crisis

environmental factors influencing skeletal grain sediment associations a critical review of miocene examples from the western mediterranean the presence of foramol rhodalgal and bryomol skeletal grain associations in ancient shallow marine limestones is commonly interpreted as evidence for non tropical palaeoclimate despite temperature being only one of several factors influencing skeletal grain associations such interpretations neglect the multitude of factors other than temperature that influence carbonate producing biota these include nutrients water energy water transparency depth of the sea floor salinity oxygen ca2 and co2 concentrations mg ca ratio alkalinity substrate requirements competitive displacement as well as biological and evolutionary trends this uniformitarian approach also disregards the probability that conditions of present day biological systems may not be representative of past conditions of analogous systems here the importance of considering these other factors is illustrated through two examples of carbonate platforms in the western mediterranean these platforms are dominated by foramol rhodalgal and bryomol associations of miocene age in spite of having formed in tropical conditions the platforms discussed are 1 the lower tortonian ramp on menorca balearic islands and 2 the lower middle miocene ramps of the central apennines italy evidence for tropical conditions in the mediterranean during the period of growth of these platforms is provided by species of red algae and larger foraminifera by data from coeval continental basins and by global oxygen isotope data

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

updip sequence development on a wave and current dominated mixed carbonate siliciclastic continental shelf paleogene north carolina eastern u s a abstract cores quarry exposures and exploratory wells in the paleogene sediments of the albemarle basin north carolina span the transition between the southern carbonate and northern siliciclastic provinces of the eastern u s continental shelf succession this swell wave and current dominated shelf succession differs from the standard carbonate sequence stratigraphic model because available accommodation is limited by the depth of wave abrasion and scour the study area is on the thin updip part of the shelf which includes the relatively positive cape fear arch onslow block and the slowly subsiding 1 5 cm ky albemarle block to the north the paleogene supersequence set has a basal boundary that is a hardground on cretaceous shoreface shallow shelf mollusc facies it is overlain by a thin paleocene sequence of transgressive deeper offshore glauconitic fine sands to deep marine silt shale five regionally mappable vertically stacked eocene sequences 0 30 m thick contain coastal sands shoreface sandy mollusc rudstone offshore bryozoan grainstone packstone and subwave base fine wackestone packstone and marl eocene sequences commonly are bounded by hardgrounds overlain by thin local lowstand shallow marine sands they consist of a thin transgressive shallow marine unit commonly absent overlain by an upward shallowing highstand marine succession on the arch lowstand and transgressive units may be condensed into lags the lower oligocene succession on the arch has a single marl to fine foram sand dominated sequence whereas downdip two to three siliciclastic rich sequences are developed capped by nearshore sandy molluscan facies the upper oligocene section is dominated by possibly three sequences composed of basal thin sands grading up into variably sandy mollusc rudstone sequence development was influenced by differential movement of basement blocks which influenced localization of fines in lows coupled with increasing third order eustatic sea level changes during later paleogene global cooling this was coupled with swell wave and current sweeping of the shelf that effectively decreased available accommodation by 20 30 m and generated the distinctive hardgrounds at sequence boundaries and variable development of lowstand and transgressive system tracts the well developed highstand deposits reflect maximum accommodation allowing deposition of an upward shallowing succession that terminated at the depth of wave abrasion and current scour on the open shelf the sequence stratigraphic development contrasts markedly with that from tropical shelves which tend to be aggraded to sea level

deep water changes the near synchronous disappearance of a group of benthic foraminifera from the late miocene mediterranean abstract benthic foraminiferal and geochemical data from the monte del casino section in northern italy are employed to reconstruct the sequence of events preceding the late miocene mediterranean salinity crisis we evaluate the effects of eustatic sea level changes and tectonic events affecting the atlantic mediterranean connections changing benthic foraminiferal assemblages record changes in the deep water environment that can be explained by progressive isolation of the mediterranean basin the results of the analyses of stable oxygen and carbon isotopes and redox sensitive elements are in line with the benthic faunal trends at 7 16 ma a first major step in isolation of the basin is indicated by the nearly simultaneous disappearance of a group of deeper water benthic species usually found in middle to lower slope environments at the same time stable isotopes and redox sensitive elements indicate cooling and decreasing bottom water oxygenation after 6 8 ma gradual development of water mass stratification probably accompanied by increasing bottom water salinity is indicated by all proxies the cyclic pattern of homogeneous and sapropelitic sediments in the section is related to astronomical parameters and allows a detailed correlation with mediterranean sections at considerable geographic distances we compared the benthic foraminiferal faunas with those from the metochia section gavdos greece deposited at a similar water depth 1000 m to find that the benthic foraminifera at both sites indicate a similar synchronous paleoenvironmental development all proxies indicate that the onset of the late miocene mediterranean salinity crisis dates back to the earliest messinian the development of the mediterranean basin toward an evaporite trap is a result of interactions between a 400 kyr eccentricity related climatic effect superimposed upon gateway dynamics at the atlantic mediterranean connections benthic foraminifera accurately record the steps in increasing isolation of the mediterranean basin

subtropical to temperate facies from a transition zone mixed carbonate siliciclastic system palaeogene north carolina usa palaeogene passive margin sediments on the us mid atlantic coastal plain provide valuable insight into facies interaction and distribution on mixed carbonate siliciclastic shelves this study utilizes well cuttings outcrop core and seismic data to document temporal and spatial variations in admixed bryozoan rich skeletal carbonates and sandy siliciclastic units that were deposited on a humid passive margin located in the vicinity of a major marine transition zone this zone was situated between north flowing warm waters of the ancestral gulf stream carbonate dominated settings and south flowing cold waters of the ancestral labrador current siliciclastic dominated settings some degree of mixing of carbonates and siliciclastics occurs in all facies however siliciclastic prone sediments predominate in nearshore settings while carbonate prone sediments are more common in more open marine settings of the inner shelf break and deep shelf a distinctive dual break shelf depositional profile originated following a major late cretaceous to palaeocene transgression that drowned the earlier shallow platform this profile was characterized by prominent mid shelf break dividing the shallow shelf from the deep shelf and a major continental shelf slope break incomplete filling of available accommodation space during successive buildup of the shallow shelf preserved the topographic break on this passive margin storm wave base also contributed to the preservation of the dual break shelf geometry by beveling shallow shelf sediments and transporting them onto and seaward of the mid shelf break sediment fines in deep shelf facies were produced in place transported downdip from the shallow shelf by storm ebb currents and boundary currents and reworked from adjacent areas of the deep shelf by strike parallel boundary currents regional climate and boundary currents controlled whether carbonate or siliciclastic material was deposited on the shelf with warmer waters and more humid climates favouring carbonate deposition and cooler more arid conditions favouring glaucony and siliciclastic dominated deposition continuous wave and current sweeping of the shallow shelf favoured deposition of mud lean facies across much of the shallow shelf skeletal components in much of the carbonate rich strata formed in warm nutrient rich subtropical waters as indicated by widespread occurrences of larger benthic foraminifera and molluscan assemblages these indicators of warm water deposition within the bryozoan mollusk rich carbonate assemblage on this shelf provide an example of a warm water bryomol assemblage such facies generally are associated with cooler water depositional settings

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

interplay of late cenozoic siliciclastic supply and carbonate response on the southeast florida platform abstract high resolution seismic reflection data collected along the length of the caloosahatchee river in southwestern florida have been correlated to nannofossil biostratigraphy and strontium isotope chemostratigraphy at six continuously cored boreholes these data are interpreted to show a major late miocene to early pliocene fluvial deltaic depositional system that prograded southward across the carbonate florida platform interrupting nearly continuous carbonate deposition since early in the cretaceous connection of the platform top to a continental source of siliciclastics and significant paleotopography combined to focus accumulation of an immense supply of siliciclastics on the southeastern part of the florida platform the remarkably thick 100 m sand rich depositional system which is characterized by clinoformal progradation filled in deep accommodation while antecedent paleotopography directed deltaic progradation southward within the middle of the present day florida peninsula the deltaic depositional system may have prograded about 200 km southward to the middle and upper florida keys where late miocene to pliocene siliciclastics form the foundation of the quaternary carbonate shelf and shelf margin of the florida keys these far traveled siliciclastic deposits filled accommodation on the southeastern part of the florida platform so that paleobathymetry was sufficiently shallow to allow quaternary recovery of carbonate sedimentation in the area of southern peninsular florida and the florida keys

neogene to recent stratigraphy and depositional regimes of the northwest florida inner continental shelf abstract the late neogene to recent depositional history of the inner shelf off northwest florida was investigated using high resolution seismic reflection data two principal sedimentary provinces the apalachicola embayment and the alabama florida shelf are distinguished by different structural trends and sequence stratigraphy a transition from carbonate to terrigenous clastic deposition occurs vertically and laterally from east to west the dominant controls on deposition have been sea level history and location of fluvial systems advancing southward and infilling the apalachicola embayment in the apalachicola embayment the upward carbonate to terrigenous transition correlates with a change from relatively flat lying reflections to prograding clinoforms and then chaotic and reflection free sequences carbonate deposition in the middle and late miocene is inferred to have occurred during highstands of sea level with minor input of terrigenous material in the late miocene a major erosional unconformity and associated river valley entrenchment cut deeply into the flat lying carbonate section subsequent deposition is distinguished by broad prograding clinoforms and an increase in terrigenous material in an open shelf environment in the late pliocene sea level fluctuations generated a stratigraphic record estimated by offlapping seaward thickening sequences the interaction between sea level and fluvial supply to the shelf became very important as shifting river inputs resulted in locally thick depocenters bounded by erosional unconformities four primary areas of fluvial deltaic input in the plio pleistocene are identified based on the distribution of channels and prograding clinoforms interpreted to be delta front deposition the present inner shelf is a sediment starved clastic depositional regime

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

upwelling history of the mediterranean sea revealed by stunted growth in the planktic foraminifera orbulina universa early messinian crete greece microfossil and stable isotope data 13c 18o from deep water sediments of late miocene age in the mediterranean region have revealed a stepwise restriction of the mediterranean prior to the messinian salinity crisis which was modulated by a cyclicity responding to orbital precession very little is known with regard to the effects of these changes on shallow water environments of carbonate platforms and ramps this work is based on a geological section on crete greece exposing sediments of early messinian age which documents the coeval response of pelagic and neritic systems to oceanographic changes we discuss a dataset of planktic and benthic foraminifera assemblages in conjunction with size measurements n 6 777 and isotope analyses 18o 13c of the planktic foraminifera orbulina universa with regard to reef growth patterns the planktic foraminifera fauna displays pronounced cyclical abundance changes of warm oligotrophic o universa and cold meso to eu trophic taxa globigerinids neogloboquadrinids this cyclicity corresponds to lithological changes from laminated to homogeneous marls on the precessional frequency band in beds rich in mesotrophic foraminifera o universa is rare and the test is 50 smaller than average growth and size of o universa is affected by various environmental factors including temperature trophic resources illumination and o2 content of ambient water explaining size variability by water temperature implies a change of 11 c over one precessional cycle this estimate is in disagreement with growth patterns and stable isotope data of displaced reef corals porites tarbellastraea documenting almost constant sea surface temperatures but substantial evaporation therefore moderate temperature changes in a context of intense evaporation high salinity and water column destabilization associated with upward mixing of colder water masses with higher nutrient concentrations and low o2 content better fits size variation of o universa from the presence of halimeda bioherms intercalated with the sapropel cycles we infer cyclic photic zone anoxia and at least some sections with sapropel couplets to have formed in the neritic zone we also suggest further testing of stunted growth of o universa as a proxy for enhanced nutrient availability in future palaeoceanographic studies

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

mixed carbonate siliciclastic sequence stratigraphy of a paleogene transition zone continental shelf southeastern usa abstract the sequence stratigraphy and facies of the paleogene in the subsurface of the albemarle basin north carolina was defined using 1600 thin sections of plastic impregnated well cuttings from 24 wells wireline logs biostratigraphic data and seismic data the facies formed in the transition zone between warm subtropical and temperate conditions on a swell wave dominated open shelf exposed to major boundary current activity the shelf has a distinctive seismic profile consisting of a shallow inner shelf inner shelf break deep shelf depths in excess of 200 m and the continental slope the inner shelf was characterized by distinctive quartz sand and sandy mollusk facies inshore passing seaward into a broad wave swept abrasional shelf and then into storm influenced bryozoan echinoderm limestones to depths of several tens of meters argillaceous lime mud marl deposition was widespread across the deep shelf extending onto the inner shelf during major highstands sediment thickness trends were controlled by greater differential subsidence of crustal blocks within the albemarle basin which considerably modified but did not obliterate the effects of eustatic sea level changes in this passive margin setting five supersequences were identified on seismic and in wells each consisting of multiple regionally identifiable sequences the paleocene supersequence is dominated by widespread marl deposition reflecting shelf flooding into the late paleocene thermal maximum this warming corresponds with widespread inner shelf skeletal carbonate deposition from the late paleocene through the middle eocene the two eocene supersequences identified are dominated by bryozoan echinoderm rich carbonates that formed a seismically definable sediment buildup 50 km wide by 100 m thick across the deepest inner shelf during the lower to early middle eocene middle to upper eocene supersequence highstand sequences indicate increased progradation and greater mixing of shelf carbonates with nearshore siliciclastics likely in response to lowering sea levels and cooling climate the two oligocene supersequences identified are dominated by coarse siliciclastic sand that is heavily admixed with mollusk foraminifer dominated carbonates rapid flooding followed by extensive progradation of shallow shelf sediments in oligocene sequences reflects continued eustatic lowering driven by the onset of icehouse climatic conditions increased incision and reworking of deep shelf sediments during oligocene supersequence highstands resulted from increased ancestral gulf stream boundary current activity during icehouse times key elements controlling facies distribution through time include significant wave energy which controls the width and distribution of inner shelf facies belts through the degree of water bottom abrasion and winnowing boundary currents also are capable of large scale reworking of deep shelf sediment they also provide a mechanism for widespread inner shelf hardground development during major transgressions in addition boundary currents play a major role in stabilizing local climate by buffering seasonal temperature variations directly influencing which carbonate grain producers can thrive in this transition zone setting

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

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

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