The geological evolution of Australia is closely linked to supercontinent cycles that have characterised the tectonic evolution of Earth,with most geological and metallogenic events relating to supercontinent/supercra...The geological evolution of Australia is closely linked to supercontinent cycles that have characterised the tectonic evolution of Earth,with most geological and metallogenic events relating to supercontinent/supercraton assembly and breakup.Australia mainly grew from W–E,with two major Archean cratons,the Yilgarn and Pilbara cratons,forming the oldest part of the continent in the West Australian Element.The centre of the continent consists of the mainly Paleoproterozoic–Mesoproterozoic North and South Australian elements,whereas the E is dominated by the Neoproterozoic–Mesozoic Tasman Element.The West,North and South Australian elements initially assembled during the Paleoproterozoic amalgamation of Nuna,and the Tasman Element formed mostly as a Paleozoic accretionary margin during the assembly of Gondwana-Pangea.Australia’s present position as a relatively stable continent resulted from the breakup of Gondwana.Australia is currently moving northward toward SE Asia,probably reflecting the earliest stages of the assembly of the next supercontinent,Amasia.展开更多
Many countries around the world have carried out national-scale geochemical surveys,providing important information on the natural concentration of chemical elements and compounds in the near-surface regolith.Resultan...Many countries around the world have carried out national-scale geochemical surveys,providing important information on the natural concentration of chemical elements and compounds in the near-surface regolith.Resultant data and information layers have been put to a multitude of uses:identifying targets for mineral exploration;improving land-use management and environmental policy development;and展开更多
Paleoproterozoic–earliest Mesoproterozoic sequences in the Mount Isa region of northern Australia preserve a 200 Myr record(1800–1600 Ma)of intracontinental rifting,culminating in crustal thinning,elevated heat flow...Paleoproterozoic–earliest Mesoproterozoic sequences in the Mount Isa region of northern Australia preserve a 200 Myr record(1800–1600 Ma)of intracontinental rifting,culminating in crustal thinning,elevated heat flow and establishment of a North American Basin and Range-style crustal architecture in which basin evolution was linked at depth to bimodal magmatism,high temperature-low pressure metamorphism and the formation of extensional shear zones.Rifting initiated in crystalline basement≥1840 Ma old and produced three stacked sedimentary basins(1800–1750 Ma Leichhardt,1730–1670 Ma Calvert and 1670–1575 Ma Isa superbasins)separated by major unconformities and in which depositional conditions progressively changed from fluviatilelacustrine to fully marine.By 1685 Ma,a deep marine,turbidite-dominated basin existed in the E and basaltic magmas had evolved in composition from continental to oceanic tholeiites as the crust became increasingly thinned and attenuated.Except for an episode of minor deformation and basin inversion at c.1640 Ma,sedimentation continued across the region until onset of the Isan Orogeny at 1600 Ma.A near-identical record of crustal thinning and basaltic magmatism accompanied basin formation(lower Willyama Supergroup)in the formerly contiguous Broken Hill region from 1730–1670 Ma.展开更多
1.Introduction In 2018,the Australian Commonwealth Government committed 224.9 million AUD(160 million USD)to the Positioning Australia program in order to provide 10 cm accurate and reliable positioning to all Austral...1.Introduction In 2018,the Australian Commonwealth Government committed 224.9 million AUD(160 million USD)to the Positioning Australia program in order to provide 10 cm accurate and reliable positioning to all Australians and accelerate the adoption and development of positioning technology and applications.This is a significant improvement from the 5–10 m accuracy that can currently be achieved using consumer positioning devices.Geographically speaking,Australia is in the position to take advantage of highquality,accurate,and efficient space-based positioning constellations with view of all global and regional constellations,including those of the United States(Global Positioning System,GPS),Russia(Global Navigation Satellite System,GLONASS),the European Union(Galileo),China(BeiDou),Japan(Quasi-Zenith Satellite System,QZSS),and India(Indian Regional Navigation Satellite System,IRNSS).展开更多
Introduction Since its inception in 1878,the International Geological Congress(IGC)has grown progressively in size and stature to become the largest global geoscience meeting,attracting thousands of delegates from ove...Introduction Since its inception in 1878,the International Geological Congress(IGC)has grown progressively in size and stature to become the largest global geoscience meeting,attracting thousands of delegates from over a hundred countries.The International Union of Geological Sciences(IUGS)is the scientific sponsor of the IGC,which is generally held every four years and is sometimes referred to as the Geoscience Olympics,given that quite a few congresses have been held in the Olympic month and year.That is the case for the 34^(th) IGC,which is being hosted by the Oceania region(Figure 1)in Brisbane,Queensland,Australia,during 5–10 August 2012(www.34igc.org).展开更多
The Australian continent comprises an amalgamation of cratonic elements onto which there has been significant Phanerozoic accretion in the east.The result is a complex lithospheric structure with a broad span of ages ...The Australian continent comprises an amalgamation of cratonic elements onto which there has been significant Phanerozoic accretion in the east.The result is a complex lithospheric structure with a broad span of ages of material at the surface.The continent is moving rapidly to the north at c.7 cm/yr,relative to Asia.The collisions with the Eurasian and Pacific plates to the north,coupled to the interaction with the Pacific Plate along the eastern plate boundary through Tonga and New Zealand result in a complex pattern of stresses that is reflected in a moderate rate of intra-plate earthquakes.展开更多
The Flinders Ranges and its surroundings in South Australia comprise an impressive rugged terrain that rises abruptly from piedmont plains to the east and west and merges into the plains of the Cenozoic Lake Eyre Basi...The Flinders Ranges and its surroundings in South Australia comprise an impressive rugged terrain that rises abruptly from piedmont plains to the east and west and merges into the plains of the Cenozoic Lake Eyre Basin to the north.Folded and faulted Neoproterozoic–Cambrian clastic and carbonate sedimentary rocks of the Adelaide Geosyncline(Adelaide Rift Complex)form the predominant geology of the ranges and record varied depositional environments and metamorphic overprints and have had a complex landscape history,resulting in a diverse regolith.This ancient,arid terrain represents some of the best analogue landscapes and settings in Australia to observe features and processes fundamental to the evolution of the Earth.The strata of the Flinders Ranges record the evolution of terrestrial surface environments and the biosphere through the Cryogenian,Ediacaran and Cambrian periods,including evidence for Neoproterozoic glaciations,orbital and rotational dynamics and asteroid impact.The diverse assemblages of stromatolites,ancient and modern hydrothermal systems,and alteration assemblages provide field laboratories for astrobiological and hyperspectral research and training.For these reasons the northern Flinders Ranges near Arkaroola have been selected as a site for multi-disciplinary Mars analogue research and space education.展开更多
The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–...The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–3600 Ma);the age of the Solar System based on the oldest solids,calcium-aluminium inclusions(CAIs),generated in the protoplanetary disk.The formal GSSA for the Hadean base is the oldest reliable,weighted mean Ucorrected Pb–Pb age of 4567.30±0.16 Ma obtained for CAIs in primitive meteorites Allende and Efremovka.This age is supported by the 4568–4567 Ma U-corrected Pb–Pb ages of chondrules in Northwest African meteorites.The boundary sets an upper lifetime for the protoplanetary disk and timing of planet formation.展开更多
We have examined the fluid inclusion data and fluid chemistry of Australian orogenic and intrusion-related gold deposits to determine if similar mineralization processes apply to both styles of deposits.The fluid incl...We have examined the fluid inclusion data and fluid chemistry of Australian orogenic and intrusion-related gold deposits to determine if similar mineralization processes apply to both styles of deposits.The fluid inclusion data from the Yilgarn craton,the western subprovince of the Lachlan orogen,the Tanami,Tennant Creek and Pine Creek regions,and the Telfer gold mine show that mineralization involved fluids with broadly similar major chemical components(i.e.H_2O+NaCl+CO_2±CH_4±N_2).These deposits formed over a wide range of temperature-pressure conditions(<200 to>500℃,<100～400MPa).Low salinity, CO_2-bearing inclusions and low salinity aqueous inclusions occur in both systems but the main difference between these two types of deposits is that most intrusion-related gold deposits also contain at least one population of high-salinity aqueous brine.Oxygen and hydrogen isotope data for both styles of deposit usually cannot distinguish between a magmatic or metamorphic source for the ore-bearing fluids.However,sulfur and lead isotope data for the intrusion-related gold deposits generally indicate either a magmatic source or mixing between magmatic and sedimentary sources of fluid.The metamorphic geothermal gradients associated with intrusion-related gold deposits are characterized by low pressure,high temperature metamorphism and high crustal geothermal gradients of>30/km.Where amphibole breakdown occurs in a granite source region,the spatially related deposits are more commonly associated with Cu-Au deposits rather than Au-only deposits that are associated with lower temperature granites.The dominant processes thought to cause gold precipitation in both types of deposits are fluid-rock interaction(e.g.desulfidation)or phase separation.Consideration of the physical and chemical properties of the H_2O-NaCl-CO_2 system on the nature of gold precipitation mechanisms at different crustal levels infers different roles of chemical(fluid-rock interaction)versus rheological(phase separation and/or fluid mixing)host-rock controls on gold deposition.This also implies that at the site of deposition,similar precipitation mechanisms operate at similar crustal levels for both orogenic and intrusion-related gold deposits.展开更多
Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been ...Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa.We devise paleogeographically constrained global models of mantle convection and,based on the evolution of flow in the deepest lower mantle,show that the Afar plume migrated southward throughout its lifetime.The models suggest that the mobile Afar plume provides a dynamically consistent explanation for the spatial extent of the southward propagation of the east African rift system(EARS),which is difficult to explain by the northeastward migration of Africa over one or more fixed plumes alone,over the last≈45 Myr.We further show that the age-progression of volcanism associated with the southward propagation of EARS is consistent with the apparent surface hotspot motion that results from southward motion of the modelled Afar plume beneath the northeastward migrating African plate.The models suggest that the Afar plume became weaker as it migrated southwards,consistent with trends observed in the geochemical record.展开更多
Accurate estimation of clocks, for example for the Gravity Recovery And Climate Experiment(GRACE)twin-satellites, is a critical part of precise orbit determination(POD) that ensures temporal gravity inversion. Charact...Accurate estimation of clocks, for example for the Gravity Recovery And Climate Experiment(GRACE)twin-satellites, is a critical part of precise orbit determination(POD) that ensures temporal gravity inversion. Characterizing the periodic variations of the receiver clocks is critical for precise clock modeling and prediction. In this study, the receiver clock is estimated using two different POD procedure: kinematic and reduced-dynamic approaches. Choices and the number of orbital parameters estimated in POD process affect the clock estimates, e.g., there are 8895 and 34,560 total parameters in the reduced-dynamic and kinematic approaches, respectively. In the both cases, the periodic variations of GRACE receiver clock are mainly dominated by the GPS orbit period, as well as once-(1-pr) and twiceper-revolution(2-pr) effects. Here the 1-pr effect is coupled with the relativistic effect, resulting in a difficulty to separate both signals. The clock amplitudes caused by the GPS orbit period, 1-pr and 2-pr are about 0.1, 0.03 and 0.01 ns, respectively. The GPS orbit period is almost one order magnitude larger than the 1-and 2-pr effect. The 0.1-ns amplitude of the 12-h periodic variation is equivalent to a 3-cm error in range. Such a systematic error should be considered in the receiver clock modeling for both the improvement of positioning accuracy and the reduction of number of unknown parameters, if the precise point positioning(PPP) technique is used for the orbit determination of the GRACE.展开更多
Introduction The International Union of Geological Sciences(IUGS)was formed in 1961 as the umbrella organisation to represent the geosciences globally.It is a non-political,non-governmental and notfor-profit organizat...Introduction The International Union of Geological Sciences(IUGS)was formed in 1961 as the umbrella organisation to represent the geosciences globally.It is a non-political,non-governmental and notfor-profit organization with 120 member countries,which:1.Promotes development of the geosciences through the support of international,broad-based,and interdisciplinary scientific studies relevant to the entire System Earth.展开更多
Petascale archives of Earth observations from space(EOS)have the potential to characterise water resources at continental scales.For this data to be useful,it needs to be organised,converted from individual scenes as ...Petascale archives of Earth observations from space(EOS)have the potential to characterise water resources at continental scales.For this data to be useful,it needs to be organised,converted from individual scenes as acquired by multiple sensors,converted into“analysis ready data”,and made available through high performance computing platforms.Moreover,converting this data into insights requires integration of non-EOS data-sets that can provide biophysical and climatic context for EOS.Digital Earth Australia has demonstrated its ability to link EOS to rainfall and stream gauge data to provide insight into surface water dynamics during the hydrological extremes of flood and drought.This information is supporting the characterisation of groundwater resources across Australia’s north and could potentially be used to gain an understanding of the vulnerability of transport infrastructure to floods in remote,sparsely gauged regions of northern and central Australia.展开更多
To comprehensively support national and international initiatives for sustainable development,land cover products need to be reliably and routinely generated within operational frameworks.Coupled with consistent seman...To comprehensively support national and international initiatives for sustainable development,land cover products need to be reliably and routinely generated within operational frameworks.Coupled with consistent semantics and taxonomies,ensuring confidence in mapping land cover for multiple time periods,facilitates informed decision-making at scales appropriate to multiple policy domains.The United Nations Food and Agriculture Organisation(FAO)Land Cover Classification System(LCCS)provides a taxonomy that comparable at different scales,level of detail and geographic location.The Open Data Cube(ODC)initiative offers a framework for operational continental-scale land cover mapping using analysis-ready Earth Observation data.This study utilised the FAO LCCS framework and the Landsat sensor data through Digital Earth Australia(DEA;Australia’s ODC instance)to generate consistent and continent-wide land cover mapping(DEA Land Cover)of the Australian continent.DEA Land Cover provides annual maps from 1988 to 2020 at 25 m resolution.Output maps were validated with∼12,000 independent validation points,giving an overall map accuracy of 80%.DEA Land Cover provides Australia with a nationally consistent picture of land cover,with an open-source software package using readily available global coverage data and demonstrates a pathway of adoption for national implementations across the world.展开更多
Global Positioning System(GPS)position verification and legal traceability in Australia supports industry,trade,science and innovation and is trusted and recognized domestically and internationally.At the end of 2017,...Global Positioning System(GPS)position verification and legal traceability in Australia supports industry,trade,science and innovation and is trusted and recognized domestically and internationally.At the end of 2017,the Australia’s national datum was transitioned from the Geocentric Datum of Australia 1994(GDA94)to the Geocentric Datum of Australia 2020(GDA2020).As such,the datum for the legal traceability of GPS positions in Australia has also moved to GDA2020.This paper highlights the importance of legal metrology and measurement in terms of GPS positions in accordance with the National Measurement Act 1960(Commonwealth of Australia).Here we provide an overview of the process of issuing the so-called‘Regulation 13 Certificates’for Continuously Operating Reference Stations(CORS)across Australia.The position verification methodology is detailed,including the quality control,metadata assurance,and dynamic management of the certificates as well as positional uncertainty determination of CORS with varying quality.A quality monitoring system of positions is also discussed along with how measurement traceability is ensured including short-term and long-term position monitoring schemes.展开更多
Earth Observation(EO)has been recognised as a key data source for supporting the United Nations Sustainable Development Goals(SDGs).Advances in data availability and analytical capabilities have provided a wide range ...Earth Observation(EO)has been recognised as a key data source for supporting the United Nations Sustainable Development Goals(SDGs).Advances in data availability and analytical capabilities have provided a wide range of users access to global coverage analysis-ready data(ARD).However,ARD does not provide the information required by national agencies tasked with coordinating the implementation of SDGs.Reliable,standardised,scalable mapping of land cover and its change over time and space facilitates informed deci-sion making,providing cohesive methods for target setting and reporting of SDGs.The aim of this study was to implement a global framework for classifying land cover.The Food and Agriculture Organisation’s Land Cover Classification System(FAO LCCS)provides a global land cover taxonomy suitable to comprehensively support SDG target setting and reporting.We present a fully implemented FAO LCCS optimised for EO data;Living Earth,an open-source software package that can be readily applied using existing national EO infrastructure and satellite data.We resolve several semantic challenges of LCCS for consistent EO implementation,including modifications to environmental descriptors,inter-dependency within the mod-ular-hierarchical framework,and increased flexibility associated with limited data availability.To ensure easy adoption of Living Earth for SDG reporting,we identified key environmental descriptors to provide resource allocation recommendations for generating routinely retrieved input parameters.Living Earth provides an optimal platform for global adoption of EO4SDGs ensuring a transparent methodology that allows monitoring to be standardised for all countries.展开更多
The effort and cost required to convert satellite Earth Observation(EO)data into meaningful geophysical variables has prevented the systematic analysis of all available observations.To overcome these problems,we utili...The effort and cost required to convert satellite Earth Observation(EO)data into meaningful geophysical variables has prevented the systematic analysis of all available observations.To overcome these problems,we utilise an integrated High Performance Computing and Data environment to rapidly process,restructure and analyse the Australian Landsat data archive.In this approach,the EO data are assigned to a common grid framework that spans the full geospatial and temporal extent of the observations–the EO Data Cube.This approach is pixel-based and incorporates geometric and spectral calibration and quality assurance of each Earth surface reflectance measurement.We demonstrate the utility of the approach with rapid time-series mapping of surface water across the entire Australian continent using 27 years of continuous,25 m resolution observations.Our preliminary analysis of the Landsat archive shows how the EO Data Cube can effectively liberate high-resolution EO data from their complex sensor-specific data structures and revolutionise our ability to measure environmental change.展开更多
文摘The geological evolution of Australia is closely linked to supercontinent cycles that have characterised the tectonic evolution of Earth,with most geological and metallogenic events relating to supercontinent/supercraton assembly and breakup.Australia mainly grew from W–E,with two major Archean cratons,the Yilgarn and Pilbara cratons,forming the oldest part of the continent in the West Australian Element.The centre of the continent consists of the mainly Paleoproterozoic–Mesoproterozoic North and South Australian elements,whereas the E is dominated by the Neoproterozoic–Mesozoic Tasman Element.The West,North and South Australian elements initially assembled during the Paleoproterozoic amalgamation of Nuna,and the Tasman Element formed mostly as a Paleozoic accretionary margin during the assembly of Gondwana-Pangea.Australia’s present position as a relatively stable continent resulted from the breakup of Gondwana.Australia is currently moving northward toward SE Asia,probably reflecting the earliest stages of the assembly of the next supercontinent,Amasia.
文摘Many countries around the world have carried out national-scale geochemical surveys,providing important information on the natural concentration of chemical elements and compounds in the near-surface regolith.Resultant data and information layers have been put to a multitude of uses:identifying targets for mineral exploration;improving land-use management and environmental policy development;and
文摘Paleoproterozoic–earliest Mesoproterozoic sequences in the Mount Isa region of northern Australia preserve a 200 Myr record(1800–1600 Ma)of intracontinental rifting,culminating in crustal thinning,elevated heat flow and establishment of a North American Basin and Range-style crustal architecture in which basin evolution was linked at depth to bimodal magmatism,high temperature-low pressure metamorphism and the formation of extensional shear zones.Rifting initiated in crystalline basement≥1840 Ma old and produced three stacked sedimentary basins(1800–1750 Ma Leichhardt,1730–1670 Ma Calvert and 1670–1575 Ma Isa superbasins)separated by major unconformities and in which depositional conditions progressively changed from fluviatilelacustrine to fully marine.By 1685 Ma,a deep marine,turbidite-dominated basin existed in the E and basaltic magmas had evolved in composition from continental to oceanic tholeiites as the crust became increasingly thinned and attenuated.Except for an episode of minor deformation and basin inversion at c.1640 Ma,sedimentation continued across the region until onset of the Isan Orogeny at 1600 Ma.A near-identical record of crustal thinning and basaltic magmatism accompanied basin formation(lower Willyama Supergroup)in the formerly contiguous Broken Hill region from 1730–1670 Ma.
文摘1.Introduction In 2018,the Australian Commonwealth Government committed 224.9 million AUD(160 million USD)to the Positioning Australia program in order to provide 10 cm accurate and reliable positioning to all Australians and accelerate the adoption and development of positioning technology and applications.This is a significant improvement from the 5–10 m accuracy that can currently be achieved using consumer positioning devices.Geographically speaking,Australia is in the position to take advantage of highquality,accurate,and efficient space-based positioning constellations with view of all global and regional constellations,including those of the United States(Global Positioning System,GPS),Russia(Global Navigation Satellite System,GLONASS),the European Union(Galileo),China(BeiDou),Japan(Quasi-Zenith Satellite System,QZSS),and India(Indian Regional Navigation Satellite System,IRNSS).
文摘Introduction Since its inception in 1878,the International Geological Congress(IGC)has grown progressively in size and stature to become the largest global geoscience meeting,attracting thousands of delegates from over a hundred countries.The International Union of Geological Sciences(IUGS)is the scientific sponsor of the IGC,which is generally held every four years and is sometimes referred to as the Geoscience Olympics,given that quite a few congresses have been held in the Olympic month and year.That is the case for the 34^(th) IGC,which is being hosted by the Oceania region(Figure 1)in Brisbane,Queensland,Australia,during 5–10 August 2012(www.34igc.org).
文摘The Australian continent comprises an amalgamation of cratonic elements onto which there has been significant Phanerozoic accretion in the east.The result is a complex lithospheric structure with a broad span of ages of material at the surface.The continent is moving rapidly to the north at c.7 cm/yr,relative to Asia.The collisions with the Eurasian and Pacific plates to the north,coupled to the interaction with the Pacific Plate along the eastern plate boundary through Tonga and New Zealand result in a complex pattern of stresses that is reflected in a moderate rate of intra-plate earthquakes.
文摘The Flinders Ranges and its surroundings in South Australia comprise an impressive rugged terrain that rises abruptly from piedmont plains to the east and west and merges into the plains of the Cenozoic Lake Eyre Basin to the north.Folded and faulted Neoproterozoic–Cambrian clastic and carbonate sedimentary rocks of the Adelaide Geosyncline(Adelaide Rift Complex)form the predominant geology of the ranges and record varied depositional environments and metamorphic overprints and have had a complex landscape history,resulting in a diverse regolith.This ancient,arid terrain represents some of the best analogue landscapes and settings in Australia to observe features and processes fundamental to the evolution of the Earth.The strata of the Flinders Ranges record the evolution of terrestrial surface environments and the biosphere through the Cryogenian,Ediacaran and Cambrian periods,including evidence for Neoproterozoic glaciations,orbital and rotational dynamics and asteroid impact.The diverse assemblages of stromatolites,ancient and modern hydrothermal systems,and alteration assemblages provide field laboratories for astrobiological and hyperspectral research and training.For these reasons the northern Flinders Ranges near Arkaroola have been selected as a site for multi-disciplinary Mars analogue research and space education.
文摘The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–3600 Ma);the age of the Solar System based on the oldest solids,calcium-aluminium inclusions(CAIs),generated in the protoplanetary disk.The formal GSSA for the Hadean base is the oldest reliable,weighted mean Ucorrected Pb–Pb age of 4567.30±0.16 Ma obtained for CAIs in primitive meteorites Allende and Efremovka.This age is supported by the 4568–4567 Ma U-corrected Pb–Pb ages of chondrules in Northwest African meteorites.The boundary sets an upper lifetime for the protoplanetary disk and timing of planet formation.
文摘We have examined the fluid inclusion data and fluid chemistry of Australian orogenic and intrusion-related gold deposits to determine if similar mineralization processes apply to both styles of deposits.The fluid inclusion data from the Yilgarn craton,the western subprovince of the Lachlan orogen,the Tanami,Tennant Creek and Pine Creek regions,and the Telfer gold mine show that mineralization involved fluids with broadly similar major chemical components(i.e.H_2O+NaCl+CO_2±CH_4±N_2).These deposits formed over a wide range of temperature-pressure conditions(<200 to>500℃,<100～400MPa).Low salinity, CO_2-bearing inclusions and low salinity aqueous inclusions occur in both systems but the main difference between these two types of deposits is that most intrusion-related gold deposits also contain at least one population of high-salinity aqueous brine.Oxygen and hydrogen isotope data for both styles of deposit usually cannot distinguish between a magmatic or metamorphic source for the ore-bearing fluids.However,sulfur and lead isotope data for the intrusion-related gold deposits generally indicate either a magmatic source or mixing between magmatic and sedimentary sources of fluid.The metamorphic geothermal gradients associated with intrusion-related gold deposits are characterized by low pressure,high temperature metamorphism and high crustal geothermal gradients of>30/km.Where amphibole breakdown occurs in a granite source region,the spatially related deposits are more commonly associated with Cu-Au deposits rather than Au-only deposits that are associated with lower temperature granites.The dominant processes thought to cause gold precipitation in both types of deposits are fluid-rock interaction(e.g.desulfidation)or phase separation.Consideration of the physical and chemical properties of the H_2O-NaCl-CO_2 system on the nature of gold precipitation mechanisms at different crustal levels infers different roles of chemical(fluid-rock interaction)versus rheological(phase separation and/or fluid mixing)host-rock controls on gold deposition.This also implies that at the site of deposition,similar precipitation mechanisms operate at similar crustal levels for both orogenic and intrusion-related gold deposits.
基金supported by ARC grants IH130200012 and DP130101946supported by the National Science Foundation under award EAR-1645775undertaken with the assistance of resources from the National Computational Infrastructure(NCI),which is supported by the Australian Government。
文摘Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa.We devise paleogeographically constrained global models of mantle convection and,based on the evolution of flow in the deepest lower mantle,show that the Afar plume migrated southward throughout its lifetime.The models suggest that the mobile Afar plume provides a dynamically consistent explanation for the spatial extent of the southward propagation of the east African rift system(EARS),which is difficult to explain by the northeastward migration of Africa over one or more fixed plumes alone,over the last≈45 Myr.We further show that the age-progression of volcanism associated with the southward propagation of EARS is consistent with the apparent surface hotspot motion that results from southward motion of the modelled Afar plume beneath the northeastward migrating African plate.The models suggest that the Afar plume became weaker as it migrated southwards,consistent with trends observed in the geochemical record.
基金funded by the Ministry of Science and Technology of Taiwan, under grant numbers 103-2116-M-008-014
文摘Accurate estimation of clocks, for example for the Gravity Recovery And Climate Experiment(GRACE)twin-satellites, is a critical part of precise orbit determination(POD) that ensures temporal gravity inversion. Characterizing the periodic variations of the receiver clocks is critical for precise clock modeling and prediction. In this study, the receiver clock is estimated using two different POD procedure: kinematic and reduced-dynamic approaches. Choices and the number of orbital parameters estimated in POD process affect the clock estimates, e.g., there are 8895 and 34,560 total parameters in the reduced-dynamic and kinematic approaches, respectively. In the both cases, the periodic variations of GRACE receiver clock are mainly dominated by the GPS orbit period, as well as once-(1-pr) and twiceper-revolution(2-pr) effects. Here the 1-pr effect is coupled with the relativistic effect, resulting in a difficulty to separate both signals. The clock amplitudes caused by the GPS orbit period, 1-pr and 2-pr are about 0.1, 0.03 and 0.01 ns, respectively. The GPS orbit period is almost one order magnitude larger than the 1-and 2-pr effect. The 0.1-ns amplitude of the 12-h periodic variation is equivalent to a 3-cm error in range. Such a systematic error should be considered in the receiver clock modeling for both the improvement of positioning accuracy and the reduction of number of unknown parameters, if the precise point positioning(PPP) technique is used for the orbit determination of the GRACE.
文摘Introduction The International Union of Geological Sciences(IUGS)was formed in 1961 as the umbrella organisation to represent the geosciences globally.It is a non-political,non-governmental and notfor-profit organization with 120 member countries,which:1.Promotes development of the geosciences through the support of international,broad-based,and interdisciplinary scientific studies relevant to the entire System Earth.
文摘Petascale archives of Earth observations from space(EOS)have the potential to characterise water resources at continental scales.For this data to be useful,it needs to be organised,converted from individual scenes as acquired by multiple sensors,converted into“analysis ready data”,and made available through high performance computing platforms.Moreover,converting this data into insights requires integration of non-EOS data-sets that can provide biophysical and climatic context for EOS.Digital Earth Australia has demonstrated its ability to link EOS to rainfall and stream gauge data to provide insight into surface water dynamics during the hydrological extremes of flood and drought.This information is supporting the characterisation of groundwater resources across Australia’s north and could potentially be used to gain an understanding of the vulnerability of transport infrastructure to floods in remote,sparsely gauged regions of northern and central Australia.
基金support of Geoscience Australia,through the DEA Land Cover project,and the European Regional Development Fund(ERDF)Sêr Cymru II programme award[grant number 80761-AU-108,Living Wales].
文摘To comprehensively support national and international initiatives for sustainable development,land cover products need to be reliably and routinely generated within operational frameworks.Coupled with consistent semantics and taxonomies,ensuring confidence in mapping land cover for multiple time periods,facilitates informed decision-making at scales appropriate to multiple policy domains.The United Nations Food and Agriculture Organisation(FAO)Land Cover Classification System(LCCS)provides a taxonomy that comparable at different scales,level of detail and geographic location.The Open Data Cube(ODC)initiative offers a framework for operational continental-scale land cover mapping using analysis-ready Earth Observation data.This study utilised the FAO LCCS framework and the Landsat sensor data through Digital Earth Australia(DEA;Australia’s ODC instance)to generate consistent and continent-wide land cover mapping(DEA Land Cover)of the Australian continent.DEA Land Cover provides annual maps from 1988 to 2020 at 25 m resolution.Output maps were validated with∼12,000 independent validation points,giving an overall map accuracy of 80%.DEA Land Cover provides Australia with a nationally consistent picture of land cover,with an open-source software package using readily available global coverage data and demonstrates a pathway of adoption for national implementations across the world.
文摘Global Positioning System(GPS)position verification and legal traceability in Australia supports industry,trade,science and innovation and is trusted and recognized domestically and internationally.At the end of 2017,the Australia’s national datum was transitioned from the Geocentric Datum of Australia 1994(GDA94)to the Geocentric Datum of Australia 2020(GDA2020).As such,the datum for the legal traceability of GPS positions in Australia has also moved to GDA2020.This paper highlights the importance of legal metrology and measurement in terms of GPS positions in accordance with the National Measurement Act 1960(Commonwealth of Australia).Here we provide an overview of the process of issuing the so-called‘Regulation 13 Certificates’for Continuously Operating Reference Stations(CORS)across Australia.The position verification methodology is detailed,including the quality control,metadata assurance,and dynamic management of the certificates as well as positional uncertainty determination of CORS with varying quality.A quality monitoring system of positions is also discussed along with how measurement traceability is ensured including short-term and long-term position monitoring schemes.
基金This research has been conducted with the support of Geoscience Australia,through the DEA Land Cover project,and the European Research Development Fund(ERDF)Sêr Cymru II program award(80761-AU-108,Living Wales).
文摘Earth Observation(EO)has been recognised as a key data source for supporting the United Nations Sustainable Development Goals(SDGs).Advances in data availability and analytical capabilities have provided a wide range of users access to global coverage analysis-ready data(ARD).However,ARD does not provide the information required by national agencies tasked with coordinating the implementation of SDGs.Reliable,standardised,scalable mapping of land cover and its change over time and space facilitates informed deci-sion making,providing cohesive methods for target setting and reporting of SDGs.The aim of this study was to implement a global framework for classifying land cover.The Food and Agriculture Organisation’s Land Cover Classification System(FAO LCCS)provides a global land cover taxonomy suitable to comprehensively support SDG target setting and reporting.We present a fully implemented FAO LCCS optimised for EO data;Living Earth,an open-source software package that can be readily applied using existing national EO infrastructure and satellite data.We resolve several semantic challenges of LCCS for consistent EO implementation,including modifications to environmental descriptors,inter-dependency within the mod-ular-hierarchical framework,and increased flexibility associated with limited data availability.To ensure easy adoption of Living Earth for SDG reporting,we identified key environmental descriptors to provide resource allocation recommendations for generating routinely retrieved input parameters.Living Earth provides an optimal platform for global adoption of EO4SDGs ensuring a transparent methodology that allows monitoring to be standardised for all countries.
文摘The effort and cost required to convert satellite Earth Observation(EO)data into meaningful geophysical variables has prevented the systematic analysis of all available observations.To overcome these problems,we utilise an integrated High Performance Computing and Data environment to rapidly process,restructure and analyse the Australian Landsat data archive.In this approach,the EO data are assigned to a common grid framework that spans the full geospatial and temporal extent of the observations–the EO Data Cube.This approach is pixel-based and incorporates geometric and spectral calibration and quality assurance of each Earth surface reflectance measurement.We demonstrate the utility of the approach with rapid time-series mapping of surface water across the entire Australian continent using 27 years of continuous,25 m resolution observations.Our preliminary analysis of the Landsat archive shows how the EO Data Cube can effectively liberate high-resolution EO data from their complex sensor-specific data structures and revolutionise our ability to measure environmental change.
