The Ediacaran-Cambrian Petermann Orogen is a dextral transpressional orogen exposed in central Australia,which facilitated the exhumation of a high-pressure core and the deformation of the Neoproterozoic-Palaeozoic Am...The Ediacaran-Cambrian Petermann Orogen is a dextral transpressional orogen exposed in central Australia,which facilitated the exhumation of a high-pressure core and the deformation of the Neoproterozoic-Palaeozoic Amadeus Basin.Several studies have investigated the metamorphic and deformational evolution of the Petermann Orogen;however,the spatiotemporal variation of the deformation and cooling history is yet to be fully understood.In situ muscovite and biotite Rb-Sr geochronology,in combination with Ti-in-quartz thermometry is applied to map the spatiotemporal deformation and cooling patterns of the northern part of the Petermann Orogen.Interpreted muscovite Rb-Sr growth ages obtained from samples in the Petermann Nappe Complex(PNC),range between c.598 Ma and 565 Ma,which correlate with the timing of deformation during the 600-520 Ma Petermann Orogeny.Interpreted muscovite and biotite cooling ages are younger in the east of the PNC(c.556-541 Ma)and broadly correlate with the regional pattern of crustal heat production,suggesting that the geothermal gradient had a significant control on the timing and duration of cooling.Biotite Rb-Sr cooling ages between c.555 Ma and 497 Ma for the orogenic core show no correlation with high heat production areas,however,differences in exhumed crustal levels across the Petermann Orogen are observed:high-P granulite facies rocks in the orogenic core vs middle-upper crustal rocks in the PNC,indicating that at least part of the spatiotemporal variation of cooling ages can be attributed to differential exhumation during the Petermann Orogeny.Hence,crustal heat production and differential exhumation were likely the main controlling factors on the duration and variation of cooling rates in the Petermann Orogen.展开更多
The Tasmanian microcontinent,situated along the East Gondwana accretionary margin during the late Neoproterozoic and early Palaeozoic,contains an unequivocal high-pressure metamorphic record comprising key information...The Tasmanian microcontinent,situated along the East Gondwana accretionary margin during the late Neoproterozoic and early Palaeozoic,contains an unequivocal high-pressure metamorphic record comprising key information pertaining to the geodynamics of subduction along the margin.Subduction of the Tasmanian microcontinent is interpreted by some as a response to back-arc basin inversion prior to ophiolite obduction and high-pressure metamorphism during the Cambrian Tyennan Orogeny.However,thermobarometric evidence in support of such a model from rocks once positioned on the subducting continental margin is lacking.Despite occurrences of eclogite-facies mineral assemblages in the strongly deformed Tyennan Region of western Tasmania,garnet-bearing quartzofeldspathic assemblages documented in metasedimentary lithologies from the remote south-west coast of Tasmania have been interpreted as an expression of low-to moderate-pressure metamorphism.We report a strongly overprinted chlorite-quartz-garnet-bearing assemblage from the southern Tyennan Region(Nye Bay)which shows evidence for high-pressure metamorphism.Coarse-grained garnet porphyroblasts contain inclusions of kyanite,muscovite,and rutile,and yield in-situ Lu-Hf dates of c.520 Ma.The cm-scale garnet porphyroblasts are zoned in the major and trace elements,preserving core-rim compositional gradients reflecting garnet growth up-pressure.Aided by mineral equilibria forward modelling,the garnet rim compositions and the Zr content of Cambrian rutile constrain peak metamorphic conditions of∼17.5-19 kbar and∼780-820℃,equivalent to warm subduction thermal gradients between 410-470℃/GPa.Garnet core compositions and the Ti content of quartz inclusions in the garnet cores constrain the pressures and temperatures for garnet nucleation to∼6-7 kbar and∼560-580℃,corresponding to relatively high prograde thermal gradients between 800-965℃/GPa.The thermal gradients determined from the south-west Tasmanian metamorphic record provide a direct window into the progressive evolution of the thermal state of the Cambrian subduction system,with the physical conditions of garnet nucleation potentially reflecting those of subduction initiation.The corresponding warm thermal gradients provide evidence for subduction initiation driven by the collapse of a pre-orogenic back-arc.This interpretation is consistent with an existing tectonic model for the Tyennan Orogeny which proposes a back-arc basin origin for the protoliths to the western Tasmanian sub-ophiolitic metamorphic sole.展开更多
Ultrahigh temperature （UHT） metamorphism is the most thermally extreme form of regional crustal metamorphism, with temperatures exceeding 900 ℃. UHT crustal metamorphism is recognised in more than 50 localities glo...Ultrahigh temperature （UHT） metamorphism is the most thermally extreme form of regional crustal metamorphism, with temperatures exceeding 900 ℃. UHT crustal metamorphism is recognised in more than 50 localities globally in the metamorphic rock record and is accepted as ＇normal＇ in the spectrum of regional crustal processes. UHT metamorphism is Wpically identified on the basis of diagnostic mineral assemblages such as sapphirine ＋ quartz, orthopyroxene ＋ sillimanite ＋ quartz and osumilite in Mg-Al- rich rock compositions, now usually coupled with pseudosection-based thermobarometry using internally-consistent thermodynamic data sets and/or Al-in-Orthopyroxene and ternary feldspar thermobarometry. Significant progress in the understanding of regional UHT metamorphism in recent years includes： （1） development of a ferric iron activity-composition thermodynamic model for sapphirine, allowing phase diagram calculations for oxidised rock compositions; （2） quantification of UHT conditions via trace element thermometry, with Zr-in-rutile more commonly recording higher temperatures than Ti-in-zircon. Rutile is likely to be stable at peak UHT conditions whereas zircon may only grow as UHT rocks are cooling. In addition, the extent to which Zr diffuses out of rutile is controlled by chemical communication with zircon; （3） more fully recognising and utilising temperature-dependent thermal properties of the crust, and the possible range of heat sources causing metamorphism in geodynamic modelling studies; （4） recognising that crust partially melted either in a previous event or earlier in a long-duration event has greater capacity than fertile, unmelted crust to achieve UHT conditions due to the heat energy consumed by partial melting reactions; （5） more strongly linking U-Pb geochronological data from zircon and monazite to P-T points or path segments through using Y ＋ REE partitioning between accessory and major phases, as well as phase diagrams incorporating Zr and REE; and （6） improved insight into the settings and factors responsible for UHT metamorphism via geodynamic forward models. These models suggest that regional UHT metamorphism is, principally, geodynamically related to subduction, coupled with elevated crustal radiogenic heat generation rates.展开更多
U-Pb monazite and zircon geochronology and calculated metamorphic phase diagrams from drill holes in the northern Gawler Craton, southern Australia, reveal the presence of ca. 1.45 Ga magmatism and metamorphism. Magma...U-Pb monazite and zircon geochronology and calculated metamorphic phase diagrams from drill holes in the northern Gawler Craton, southern Australia, reveal the presence of ca. 1.45 Ga magmatism and metamorphism. Magmatism and granulite facies metamorphism of this age has not previously been recognised in the Gawler Craton. The magmatic rocks have steep LREE-enriched patterns and high Ga/Al values, suggesting they are A-type granites. Calculated metamorphic forward models suggest that this event was associated with high apparent thermal gradients and reached pressures of 3.2 -5.4 kbar and temperatures of 775-815℃. The high apparent thermal gradients may reflect pluton-enhanced metamorphism, consistent with the presence of A-type granites. The recognition of ca. 1.45 Ga tectonism in the northern Gawler Craton is added to a compilation of ca. 1.50 -1.40 Ga magmatism, shear zone reactivation, rift basin development and isotope resetting throughout the South and North Australian Cratons that shows that this event was widespread in eastern Proterozoic Australia. This event is stylistically similar to ca. 1.45 Ga A-type magmatism and high thermal gradient metamorphism in Laurentia in this interval and provides further support for a connection between Australia and Laurentia during the Mesoproterozoic. The tectonic setting of the 1.50-1.40 Ga event is unclear but may record rifting within the Nuna(or Columbia) supercontinent, or a period of intracontinental extension within a long-lived convergent setting.展开更多
Geochronology is fundamental to understanding planetary evolution.However,as space exploration continues to expand,traditional dating methods,involving complex laboratory processes,are generally not realistic for unma...Geochronology is fundamental to understanding planetary evolution.However,as space exploration continues to expand,traditional dating methods,involving complex laboratory processes,are generally not realistic for unmanned space applications.Campaign-style planetary exploration missions require dating methods that can(1)rapidly resolve age information on small samples,(2)be applied to minerals common in mafic rocks,and(3)be based on technologies that could be installed on future rover systems.We demonstrate the application of rapid in situ microanalytical Lu–Hf phosphate geochronology using samples of pallasite meteorites,which are representative examples of the deep interiors of differentiated planetoids that are generally difficult to date.Individual pallasites were dated by laser ablation tandem mass-spectrometry(LA-ICP-MS/MS),demonstrating a rapid novel method for exploring planetary evolution.Derived formation ages for individual pallasites agree with traditional methods and have<2%uncertainty,opening an avenue of opportunity for remote micro-analytical space exploration.展开更多
The development of laser ablation inductively coupled plasma quadrupole tandem mass spectrometry(LA-ICP-Q-MS/MS)opens new opportunities to rapidly date a variety of hydrothermal minerals.Here we present in situ Lu-Hf ...The development of laser ablation inductively coupled plasma quadrupole tandem mass spectrometry(LA-ICP-Q-MS/MS)opens new opportunities to rapidly date a variety of hydrothermal minerals.Here we present in situ Lu-Hf and Re-Os dates for hydrothermal apatite and molybdenite,respectively.We further report the first in situ Lu-Hf dates for bastnäsite,dolomite,and siderite,and assess their potential for constraining ore deposit geochronology.For method validation,we report isotope-dilution Lu-Hf dates for apatite reference material Bamble-1(1102±5 Ma)and calcite reference material ME-1(1531±7 Ma),enabling improved accuracy on matrix-matched calibration for LA-ICP-MS/MS Lu-Hf dating.The new methods are applied to the Vulcan Iron-Oxide Copper-Gold(IOCG)prospect in the Olympic Cu-Au Province of South Australia.Such deposits have been difficult to accurately date,given the general lack of reliable mineral geochronometers that are cogenetic with IOCG mineralisation.Hydrothermal apatite Lu-Hf dates and molybdenite Re-Os dates demonstrate that mineralisation at Vulcan largely occurred at ca.1.6 Ga,contemporaneous with the world class Olympic Dam deposit.Our data also indicates that the Lu-Hf system in apatite is more robust than the U-Pb system for determining the timing of primary apatite formation in an IOCG system.We further demonstrate that dolomite can retain Lu-Hf growth ages over an extended time period(>1.5 billion years),providing constraints on the timing of primary ore mineral crystallisation during brecciation and IOCG mineralisation.Finally,late Neoproterozoic(ca.589–544 Ma)and Carboniferous(ca.334±7 Ma)Lu-Hf dates were obtained for texturally late Cubearing carbonate veins,illustrating that the carbonate Lu-Hf method allows direct dating of Cu remobilisation events.This has important implications for mineral exploration as the remobilised Cu may have been transferred to younger deposits hosted in Neoproterozoic sedimentary basins overlaying the Olympic IOCG province.展开更多
The Rogaland-Vest Agder Sector of southwestern Norway comprises high-grade metamorphic rocks intruded by voluminous plutonic bodies that include the ~1000 km^2 Rogaland Igneous Complex（RIC）.New petrographic observat...The Rogaland-Vest Agder Sector of southwestern Norway comprises high-grade metamorphic rocks intruded by voluminous plutonic bodies that include the ~1000 km^2 Rogaland Igneous Complex（RIC）.New petrographic observations and thermodynamic phase equilibria modelling of three metapelitic samples collected at various distances（30 km,10 km and ~ 10 m） from one of the main bodies of RIC anorthosite were undertaken to assess two alternative P-T-t models for the metamorphic evolution of the area.The results are consistent with a revised two-phase evolution.Regional metamorphism followed a clockwise P-T path reaching peak conditions of ~ 850-950 ℃ and ~7-8 kbar at ~1035 Ma followed by high-temperature decompression to ~5 kbar at ~950 Ma,and resulted in extensive anatexis and melt loss to produce highly residual rocks.Subsequent emplacement of the RIC at ~930 Ma caused regional-scale contact metamorphism that affected country rocks 10 km or more from their contact with the anorthosite.This thermal overprint is expressed in the sample proximal to the anorthosite by replacement of sillimanite by coarse intergrowths of cordierite plus spinel and growth of a second generation of garnet,and in the intermediate（10 km） sample by replacement of sapphirine by coarse intergrowths of cordierite,spinel and biotite.The formation of late biotite in the intermediate sample may suggest the rocks retained small quantities of melt produced by regional metamorphism and remained at temperatures above the solidus for up to 100 Ma.Our results are more consistent with an accretionary rather than a collisional model for the Sveconorwegian Orogen.展开更多
The Gawler Craton preserves a complex and prolonged tectonic history spanning the interval c.3200–1500 Ma.Reworking of Paleoarchean,c.3400–3250 Ma crust led to the formation of c.3150 Ma granites now exposed within ...The Gawler Craton preserves a complex and prolonged tectonic history spanning the interval c.3200–1500 Ma.Reworking of Paleoarchean,c.3400–3250 Ma crust led to the formation of c.3150 Ma granites now exposed within a narrow belt in the eastern Gawler Craton.Following this,there is no known record of significant tectonic activity until the onset of bimodal magmatism during the Neoarchean to earliest Paleoproterozoic,c.2560–2470 Ma.This magmatism was terminated by high temperature metamorphism and deformation during the 2465–2410 Ma Sleafordian Orogeny.Magmatic events associated with widespread sedimentation over the interval c.2000–1740 Ma largely sources this older crust.The c.1730–1690 Ma Kimban Orogeny reworked these Paleoproterozoic basins and the Neoarchean basement in a pre-dominantly transpressional orogenic system.Juvenile mantle input followed by widespread crustal melting occurred over the interval c.1620–1570 Ma.This period of intense magmatism initiated with emplacement of the relatively juvenile c.1620–1608 Ma St Peter Suite.This was followed by the economically significant c.1600–1570 Ma Gawler Range Volcanics/Hiltaba Suite magmatic event,which resulted from widespread mid-crustal melting.Synchronous deformation and high temperature metamorphism accompanied the Gawler Range Volcanics/Hiltaba Suite magmatic event indicating it occurred in an orogenic environment.Far field stress was distributed around a central core zone of largely undisturbed Gawler Range Volcanics with deformation localised in the northern and southern Gawler Craton.The Gawler Range Volcanics/Hiltaba Suite magmatic event resulted in formation of a province of major economic significance that includes the giant Olympic Dam Cu-Au-U ore body.展开更多
Fluorite(CaF_(2))is a common hydrothermal mineral,which precipitates from fluorine-rich fluids with an exceptional capacity to transport metals and Rare Earth Elements(REEs).Hence,the ability to date fluorite has impo...Fluorite(CaF_(2))is a common hydrothermal mineral,which precipitates from fluorine-rich fluids with an exceptional capacity to transport metals and Rare Earth Elements(REEs).Hence,the ability to date fluorite has important implications for understanding the timing of metal transport in hydrothermal systems.Here we present,for the first time,fluorite Lu-Hf dates from fluorite-carbonate veins from the Olympic Cu-Au Province in South Australia.The fluorite dates were obtained in situ using the recently developed LA-ICP-MS/MS Lu-Hf dating method.A fluorite-calcite age of 1588±19 Ma was obtained for the Torrens Dam prospect,consistent with the timing of the formation of the nearby Olympic Dam iron-oxide copper gold Breccia Complex.Veins in the overlying Neoproterozoic successions were dated at 502±14 Ma,indicating a temporal link between Cu-sulphide remobilisation and the Delamerian Orogeny.Additionally,we present a multi-session reproducible date for magmatic fluorite from a monzogranite in the Pilbara Craton(Lu-Hf age of 2866±19 Ma).This age is consistent with a garnet Lu-Hf age from the same sample(2850±12 Ma)and holds potential to be developed into a secondary reference material for future fluorite Lu-Hf dating.展开更多
Tectonic reconstructions of Proterozoic Australia commonly place the Peake and Denison Domain of the northeastern Gawler Craton at the interface between the North and South Australian cratons prior to the reconfigurat...Tectonic reconstructions of Proterozoic Australia commonly place the Peake and Denison Domain of the northeastern Gawler Craton at the interface between the North and South Australian cratons prior to the reconfiguration of Australia’s main tectonic components in the Mesoproterozoic.However,this reconstruction is largely based on palaeomagnetic data as the geological correlations between these regions are currently limited,particularly during the Mesoproterozoic.The early Mesoproterozoic period is significant as it corresponds to major IOCG mineralization in the eastern Gawler Craton between 1600 Ma and 1575 Ma,and IOCG mineralization in the Mount Isa Province largely between 1550 Ma and 1490 Ma.Therefore,determining the relationship of the Peake and Denison Domain to the Gawler Craton and Mount Isa Province during this period is essential to evaluating mineral prospectivity in the northeastern Gawler Craton.New U–Pb LA-ICP-MS geochronology on zircon and titanite improves our understanding of the tectonothermal and hydrothermal history the Peake and Denison Domain during the latePalaeoproterozoic,early-Mesoproterozoic and the Cambrian–Ordovician periods.Titanite formed within largely calc-silicate alteration assemblages indicates the Peake and Denison Domain has a protracted history of hydrothermal activity,recording events at c.1565 Ma,1530–1515 Ma,c.1500 Ma,c.1465 Ma and c.490 Ma.The highly calcic nature of the c.1565–1500 Ma alteration in the Peake and Denison Domain shares strong similarities in age and character to the regional calcic-sodic alteration recorded in the Mount Isa Province.We suggest the two regions were influenced by similar hydrothermal systems during the early Mesoproterozoic,supporting reconstruction models that place the Peake and Denison Domain near the Mount Isa Province during the early-Mesoproterozoic.This highlights the prospectivity of the Peake and Denison Domain for Isan-style IOCG mineralization,but requires consideration of the post-1500 Ma rotation of prospective structures.展开更多
基金supported by the Mineral Exploration Cooperative Research Centre whose activities are funded by the Australian Government’s Cooperative Research Centre Program.This is MinEx CRC Document 2025/06.
文摘The Ediacaran-Cambrian Petermann Orogen is a dextral transpressional orogen exposed in central Australia,which facilitated the exhumation of a high-pressure core and the deformation of the Neoproterozoic-Palaeozoic Amadeus Basin.Several studies have investigated the metamorphic and deformational evolution of the Petermann Orogen;however,the spatiotemporal variation of the deformation and cooling history is yet to be fully understood.In situ muscovite and biotite Rb-Sr geochronology,in combination with Ti-in-quartz thermometry is applied to map the spatiotemporal deformation and cooling patterns of the northern part of the Petermann Orogen.Interpreted muscovite Rb-Sr growth ages obtained from samples in the Petermann Nappe Complex(PNC),range between c.598 Ma and 565 Ma,which correlate with the timing of deformation during the 600-520 Ma Petermann Orogeny.Interpreted muscovite and biotite cooling ages are younger in the east of the PNC(c.556-541 Ma)and broadly correlate with the regional pattern of crustal heat production,suggesting that the geothermal gradient had a significant control on the timing and duration of cooling.Biotite Rb-Sr cooling ages between c.555 Ma and 497 Ma for the orogenic core show no correlation with high heat production areas,however,differences in exhumed crustal levels across the Petermann Orogen are observed:high-P granulite facies rocks in the orogenic core vs middle-upper crustal rocks in the PNC,indicating that at least part of the spatiotemporal variation of cooling ages can be attributed to differential exhumation during the Petermann Orogeny.Hence,crustal heat production and differential exhumation were likely the main controlling factors on the duration and variation of cooling rates in the Petermann Orogen.
基金supported by Australian Research Council(ARC)grant DP16010437 to MH.LJM is supported by an ARC DECRA Fellowship,DE210101126.
文摘The Tasmanian microcontinent,situated along the East Gondwana accretionary margin during the late Neoproterozoic and early Palaeozoic,contains an unequivocal high-pressure metamorphic record comprising key information pertaining to the geodynamics of subduction along the margin.Subduction of the Tasmanian microcontinent is interpreted by some as a response to back-arc basin inversion prior to ophiolite obduction and high-pressure metamorphism during the Cambrian Tyennan Orogeny.However,thermobarometric evidence in support of such a model from rocks once positioned on the subducting continental margin is lacking.Despite occurrences of eclogite-facies mineral assemblages in the strongly deformed Tyennan Region of western Tasmania,garnet-bearing quartzofeldspathic assemblages documented in metasedimentary lithologies from the remote south-west coast of Tasmania have been interpreted as an expression of low-to moderate-pressure metamorphism.We report a strongly overprinted chlorite-quartz-garnet-bearing assemblage from the southern Tyennan Region(Nye Bay)which shows evidence for high-pressure metamorphism.Coarse-grained garnet porphyroblasts contain inclusions of kyanite,muscovite,and rutile,and yield in-situ Lu-Hf dates of c.520 Ma.The cm-scale garnet porphyroblasts are zoned in the major and trace elements,preserving core-rim compositional gradients reflecting garnet growth up-pressure.Aided by mineral equilibria forward modelling,the garnet rim compositions and the Zr content of Cambrian rutile constrain peak metamorphic conditions of∼17.5-19 kbar and∼780-820℃,equivalent to warm subduction thermal gradients between 410-470℃/GPa.Garnet core compositions and the Ti content of quartz inclusions in the garnet cores constrain the pressures and temperatures for garnet nucleation to∼6-7 kbar and∼560-580℃,corresponding to relatively high prograde thermal gradients between 800-965℃/GPa.The thermal gradients determined from the south-west Tasmanian metamorphic record provide a direct window into the progressive evolution of the thermal state of the Cambrian subduction system,with the physical conditions of garnet nucleation potentially reflecting those of subduction initiation.The corresponding warm thermal gradients provide evidence for subduction initiation driven by the collapse of a pre-orogenic back-arc.This interpretation is consistent with an existing tectonic model for the Tyennan Orogeny which proposes a back-arc basin origin for the protoliths to the western Tasmanian sub-ophiolitic metamorphic sole.
基金Prof.M.Santosh is thanked for his warm hospitality and the invitation to write an updated review of progress on UHT metamorphism while DEK was on a research visit to China University of Geosciences,Beijing,in September 2013 funded by Australia's Group of Eight(Go8)and in China by the China Science and Technology Exchange Center(CSTEC).Thorough and constructive reviews by M.Brown and F.Korhonen were warmly welcomed
文摘Ultrahigh temperature （UHT） metamorphism is the most thermally extreme form of regional crustal metamorphism, with temperatures exceeding 900 ℃. UHT crustal metamorphism is recognised in more than 50 localities globally in the metamorphic rock record and is accepted as ＇normal＇ in the spectrum of regional crustal processes. UHT metamorphism is Wpically identified on the basis of diagnostic mineral assemblages such as sapphirine ＋ quartz, orthopyroxene ＋ sillimanite ＋ quartz and osumilite in Mg-Al- rich rock compositions, now usually coupled with pseudosection-based thermobarometry using internally-consistent thermodynamic data sets and/or Al-in-Orthopyroxene and ternary feldspar thermobarometry. Significant progress in the understanding of regional UHT metamorphism in recent years includes： （1） development of a ferric iron activity-composition thermodynamic model for sapphirine, allowing phase diagram calculations for oxidised rock compositions; （2） quantification of UHT conditions via trace element thermometry, with Zr-in-rutile more commonly recording higher temperatures than Ti-in-zircon. Rutile is likely to be stable at peak UHT conditions whereas zircon may only grow as UHT rocks are cooling. In addition, the extent to which Zr diffuses out of rutile is controlled by chemical communication with zircon; （3） more fully recognising and utilising temperature-dependent thermal properties of the crust, and the possible range of heat sources causing metamorphism in geodynamic modelling studies; （4） recognising that crust partially melted either in a previous event or earlier in a long-duration event has greater capacity than fertile, unmelted crust to achieve UHT conditions due to the heat energy consumed by partial melting reactions; （5） more strongly linking U-Pb geochronological data from zircon and monazite to P-T points or path segments through using Y ＋ REE partitioning between accessory and major phases, as well as phase diagrams incorporating Zr and REE; and （6） improved insight into the settings and factors responsible for UHT metamorphism via geodynamic forward models. These models suggest that regional UHT metamorphism is, principally, geodynamically related to subduction, coupled with elevated crustal radiogenic heat generation rates.
基金supported by ARC Linkage Project LP160100578 (MH and JP)ARCDiscovery Project DP160104637 (MH)
文摘U-Pb monazite and zircon geochronology and calculated metamorphic phase diagrams from drill holes in the northern Gawler Craton, southern Australia, reveal the presence of ca. 1.45 Ga magmatism and metamorphism. Magmatism and granulite facies metamorphism of this age has not previously been recognised in the Gawler Craton. The magmatic rocks have steep LREE-enriched patterns and high Ga/Al values, suggesting they are A-type granites. Calculated metamorphic forward models suggest that this event was associated with high apparent thermal gradients and reached pressures of 3.2 -5.4 kbar and temperatures of 775-815℃. The high apparent thermal gradients may reflect pluton-enhanced metamorphism, consistent with the presence of A-type granites. The recognition of ca. 1.45 Ga tectonism in the northern Gawler Craton is added to a compilation of ca. 1.50 -1.40 Ga magmatism, shear zone reactivation, rift basin development and isotope resetting throughout the South and North Australian Cratons that shows that this event was widespread in eastern Proterozoic Australia. This event is stylistically similar to ca. 1.45 Ga A-type magmatism and high thermal gradient metamorphism in Laurentia in this interval and provides further support for a connection between Australia and Laurentia during the Mesoproterozoic. The tectonic setting of the 1.50-1.40 Ga event is unclear but may record rifting within the Nuna(or Columbia) supercontinent, or a period of intracontinental extension within a long-lived convergent setting.
基金supported by the Institute for Mineral and Energy Resources (IMER)Australian Research Council (ARC) DP200101881
文摘Geochronology is fundamental to understanding planetary evolution.However,as space exploration continues to expand,traditional dating methods,involving complex laboratory processes,are generally not realistic for unmanned space applications.Campaign-style planetary exploration missions require dating methods that can(1)rapidly resolve age information on small samples,(2)be applied to minerals common in mafic rocks,and(3)be based on technologies that could be installed on future rover systems.We demonstrate the application of rapid in situ microanalytical Lu–Hf phosphate geochronology using samples of pallasite meteorites,which are representative examples of the deep interiors of differentiated planetoids that are generally difficult to date.Individual pallasites were dated by laser ablation tandem mass-spectrometry(LA-ICP-MS/MS),demonstrating a rapid novel method for exploring planetary evolution.Derived formation ages for individual pallasites agree with traditional methods and have<2%uncertainty,opening an avenue of opportunity for remote micro-analytical space exploration.
基金supported by an Accelerated Discovery Initiative Grant(ADI RD02/260),entitled‘Integrated Exploration Under Deep Cover‘with joint funding from Fortescue and the Government of South AustraliaSG was further supported by an Australian Research Council Future Fellowship(FT210100906)The acquisition of isotope-dilution Lu-Hf dates was financially supported by the Mineral Exploration Cooperative Research Centre whose activities are funded by the Australian Government’s Cooperative Research Centre Program。
文摘The development of laser ablation inductively coupled plasma quadrupole tandem mass spectrometry(LA-ICP-Q-MS/MS)opens new opportunities to rapidly date a variety of hydrothermal minerals.Here we present in situ Lu-Hf and Re-Os dates for hydrothermal apatite and molybdenite,respectively.We further report the first in situ Lu-Hf dates for bastnäsite,dolomite,and siderite,and assess their potential for constraining ore deposit geochronology.For method validation,we report isotope-dilution Lu-Hf dates for apatite reference material Bamble-1(1102±5 Ma)and calcite reference material ME-1(1531±7 Ma),enabling improved accuracy on matrix-matched calibration for LA-ICP-MS/MS Lu-Hf dating.The new methods are applied to the Vulcan Iron-Oxide Copper-Gold(IOCG)prospect in the Olympic Cu-Au Province of South Australia.Such deposits have been difficult to accurately date,given the general lack of reliable mineral geochronometers that are cogenetic with IOCG mineralisation.Hydrothermal apatite Lu-Hf dates and molybdenite Re-Os dates demonstrate that mineralisation at Vulcan largely occurred at ca.1.6 Ga,contemporaneous with the world class Olympic Dam deposit.Our data also indicates that the Lu-Hf system in apatite is more robust than the U-Pb system for determining the timing of primary apatite formation in an IOCG system.We further demonstrate that dolomite can retain Lu-Hf growth ages over an extended time period(>1.5 billion years),providing constraints on the timing of primary ore mineral crystallisation during brecciation and IOCG mineralisation.Finally,late Neoproterozoic(ca.589–544 Ma)and Carboniferous(ca.334±7 Ma)Lu-Hf dates were obtained for texturally late Cubearing carbonate veins,illustrating that the carbonate Lu-Hf method allows direct dating of Cu remobilisation events.This has important implications for mineral exploration as the remobilised Cu may have been transferred to younger deposits hosted in Neoproterozoic sedimentary basins overlaying the Olympic IOCG province.
基金provided by an ARC DECRA fellowship (DE120103067)to CC
文摘The Rogaland-Vest Agder Sector of southwestern Norway comprises high-grade metamorphic rocks intruded by voluminous plutonic bodies that include the ~1000 km^2 Rogaland Igneous Complex（RIC）.New petrographic observations and thermodynamic phase equilibria modelling of three metapelitic samples collected at various distances（30 km,10 km and ~ 10 m） from one of the main bodies of RIC anorthosite were undertaken to assess two alternative P-T-t models for the metamorphic evolution of the area.The results are consistent with a revised two-phase evolution.Regional metamorphism followed a clockwise P-T path reaching peak conditions of ~ 850-950 ℃ and ~7-8 kbar at ~1035 Ma followed by high-temperature decompression to ~5 kbar at ~950 Ma,and resulted in extensive anatexis and melt loss to produce highly residual rocks.Subsequent emplacement of the RIC at ~930 Ma caused regional-scale contact metamorphism that affected country rocks 10 km or more from their contact with the anorthosite.This thermal overprint is expressed in the sample proximal to the anorthosite by replacement of sillimanite by coarse intergrowths of cordierite plus spinel and growth of a second generation of garnet,and in the intermediate（10 km） sample by replacement of sapphirine by coarse intergrowths of cordierite,spinel and biotite.The formation of late biotite in the intermediate sample may suggest the rocks retained small quantities of melt produced by regional metamorphism and remained at temperatures above the solidus for up to 100 Ma.Our results are more consistent with an accretionary rather than a collisional model for the Sveconorwegian Orogen.
文摘The Gawler Craton preserves a complex and prolonged tectonic history spanning the interval c.3200–1500 Ma.Reworking of Paleoarchean,c.3400–3250 Ma crust led to the formation of c.3150 Ma granites now exposed within a narrow belt in the eastern Gawler Craton.Following this,there is no known record of significant tectonic activity until the onset of bimodal magmatism during the Neoarchean to earliest Paleoproterozoic,c.2560–2470 Ma.This magmatism was terminated by high temperature metamorphism and deformation during the 2465–2410 Ma Sleafordian Orogeny.Magmatic events associated with widespread sedimentation over the interval c.2000–1740 Ma largely sources this older crust.The c.1730–1690 Ma Kimban Orogeny reworked these Paleoproterozoic basins and the Neoarchean basement in a pre-dominantly transpressional orogenic system.Juvenile mantle input followed by widespread crustal melting occurred over the interval c.1620–1570 Ma.This period of intense magmatism initiated with emplacement of the relatively juvenile c.1620–1608 Ma St Peter Suite.This was followed by the economically significant c.1600–1570 Ma Gawler Range Volcanics/Hiltaba Suite magmatic event,which resulted from widespread mid-crustal melting.Synchronous deformation and high temperature metamorphism accompanied the Gawler Range Volcanics/Hiltaba Suite magmatic event indicating it occurred in an orogenic environment.Far field stress was distributed around a central core zone of largely undisturbed Gawler Range Volcanics with deformation localised in the northern and southern Gawler Craton.The Gawler Range Volcanics/Hiltaba Suite magmatic event resulted in formation of a province of major economic significance that includes the giant Olympic Dam Cu-Au-U ore body.
基金supported by research grants DP200101881 and FT210100906 from the Australian Research Council(ARC)and additionallythe Mineral Exploration Cooperative Research Centre.
文摘Fluorite(CaF_(2))is a common hydrothermal mineral,which precipitates from fluorine-rich fluids with an exceptional capacity to transport metals and Rare Earth Elements(REEs).Hence,the ability to date fluorite has important implications for understanding the timing of metal transport in hydrothermal systems.Here we present,for the first time,fluorite Lu-Hf dates from fluorite-carbonate veins from the Olympic Cu-Au Province in South Australia.The fluorite dates were obtained in situ using the recently developed LA-ICP-MS/MS Lu-Hf dating method.A fluorite-calcite age of 1588±19 Ma was obtained for the Torrens Dam prospect,consistent with the timing of the formation of the nearby Olympic Dam iron-oxide copper gold Breccia Complex.Veins in the overlying Neoproterozoic successions were dated at 502±14 Ma,indicating a temporal link between Cu-sulphide remobilisation and the Delamerian Orogeny.Additionally,we present a multi-session reproducible date for magmatic fluorite from a monzogranite in the Pilbara Craton(Lu-Hf age of 2866±19 Ma).This age is consistent with a garnet Lu-Hf age from the same sample(2850±12 Ma)and holds potential to be developed into a secondary reference material for future fluorite Lu-Hf dating.
基金supported by ARC Linkage Project LP160100578(JLP and MH)the Mineral Exploration Cooperative Research Centre whose activities are funded by the Australian Government’s Cooperative Research Centre Programsupport of an Australian Government Research Training Program Stipend and LJM acknowledges the support of ARC DECRA Fellowship DE210101126.
文摘Tectonic reconstructions of Proterozoic Australia commonly place the Peake and Denison Domain of the northeastern Gawler Craton at the interface between the North and South Australian cratons prior to the reconfiguration of Australia’s main tectonic components in the Mesoproterozoic.However,this reconstruction is largely based on palaeomagnetic data as the geological correlations between these regions are currently limited,particularly during the Mesoproterozoic.The early Mesoproterozoic period is significant as it corresponds to major IOCG mineralization in the eastern Gawler Craton between 1600 Ma and 1575 Ma,and IOCG mineralization in the Mount Isa Province largely between 1550 Ma and 1490 Ma.Therefore,determining the relationship of the Peake and Denison Domain to the Gawler Craton and Mount Isa Province during this period is essential to evaluating mineral prospectivity in the northeastern Gawler Craton.New U–Pb LA-ICP-MS geochronology on zircon and titanite improves our understanding of the tectonothermal and hydrothermal history the Peake and Denison Domain during the latePalaeoproterozoic,early-Mesoproterozoic and the Cambrian–Ordovician periods.Titanite formed within largely calc-silicate alteration assemblages indicates the Peake and Denison Domain has a protracted history of hydrothermal activity,recording events at c.1565 Ma,1530–1515 Ma,c.1500 Ma,c.1465 Ma and c.490 Ma.The highly calcic nature of the c.1565–1500 Ma alteration in the Peake and Denison Domain shares strong similarities in age and character to the regional calcic-sodic alteration recorded in the Mount Isa Province.We suggest the two regions were influenced by similar hydrothermal systems during the early Mesoproterozoic,supporting reconstruction models that place the Peake and Denison Domain near the Mount Isa Province during the early-Mesoproterozoic.This highlights the prospectivity of the Peake and Denison Domain for Isan-style IOCG mineralization,but requires consideration of the post-1500 Ma rotation of prospective structures.
