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Basin Analysis | Geology | Geochronology | Isotope Geochemistry
Expanding Knowledge in the Earth Sciences | Oil and Gas Exploration | Mineral Exploration not elsewhere classified |
Publisher: Cambridge University Press (CUP)
Date: 30-10-2019
DOI: 10.1017/S0016756817000802
Abstract: The East African Orogen contains a series of high-strain zones that formed as Gondwana amalgamated. The Tulu Dimtu shear belt is one of these N–S structures within the Barka–Tulu Dimtu zone in western Ethiopia, and contains ultramafic bodies of equivocal origin. Identifying the petrogenetic origin of these enigmatic rocks provides evidence for the geodynamic significance of these shear zones. Owing to their altered state, these ultramafic rocks’ well-preserved chrome spinels provide the only reliable evidence for their source and tectonic affiliation. Chrome spinels have high Cr 2 O 3 (30.04–68.76 wt %), while recalculated Fe 2 O 3 ( 2 %) and TiO 2 (0.01–0.51 %) values are low. The Cr# (molar Cr 3+ /Cr 3+ + Al 2+ ) and Mg# (Mg 2+ /Mg 2+ + Fe 2+ ) have averages of 0.88 and 0.22, respectively. Based on olivine–spinel equilibria, the calculated f O 2 values (FMQ +3.03) for the dunites reveal a highly oxidized environment. This spinel chemistry (high Cr# 0.6 and low Ti) supports a supra-subduction origin, with an oxidized mantle source more refractory than depleted MORB mantle (DMM). These spinel compositions indicate that some ultramafic bodies in western Ethiopia, including those from Daleti, Tulu and Dimtu, are serpentinized peridotites emplaced as obducted ophiolite complexes. By contrast, the ultramafic rocks from the Yubdo locality have a different spinel chemistry, with strong affiliation with igneous spinels formed in Alaskan-style mafic intrusions. These collective results suggest that regardless of their origin as supra-subduction ophiolites or as Alaskan-type intrusions, these spinels were formed on a convergent-subduction margin.
Publisher: California Digital Library (CDL)
Date: 18-05-2022
DOI: 10.31223/X5S92D
Abstract: The ca. 1.5–1.3 Ga Roper Group of the greater McArthur Basin is a component of one of the most extensive Precambrian hydrocarbon-bearing basins preserved in the geological record, recently assessed as containing 429 million barrels of oil and eight trillion cubic feet of gas (in place). It was deposited in an intra-cratonic sea, referred to here as the McArthur-Yanliao Gulf.The Velkerri Formation forms the major deep-water facies of the Roper Group. Trace metal redox proxies from this formation indicate that it was deposited in stratified waters, in which a shallow oxic layer overlay suboxic to anoxic waters. These deep waters became episodically euxinic during periods of high organic carbon export. The Velkerri Formation has organic carbon contents that reach ~10 wt%. Variations in organic carbon isotopes are consistent with organic carbon enrichment being associated with increases in primary productivity and export, rather than flooding surfaces or variations in mineralogy.Although deposition of the Velkerri Formation in an intracontinental setting has been well established, recent global reconstructions show a broader mid to low latitude gulf, with deposition of the Velkerri Formation being coeval with the widespread deposition of organic-rich rocks across northern Australia and North China. The deposition of these organic-rich rocks may have been accompanied by significant oxygenation associated with such widespread organic carbon burial during the Mesoproterozoic.
Publisher: Wiley
Date: 16-04-2020
DOI: 10.1111/BRE.12450
Publisher: Geological Society of London
Date: 22-11-2019
DOI: 10.1144/JGS2018-125
Publisher: California Digital Library (CDL)
Date: 02-03-2021
DOI: 10.31223/X56K7S
Publisher: Elsevier BV
Date: 11-2015
Publisher: Petroleum Exploration Society of Australia (PESA)
Date: 30-08-2022
DOI: 10.36404/FIWQ4275
Abstract: The Centralian Superbasin (CSB) is a ~ 2 million km2 Neoproterozoic to early Palaeozoic (ca. 850−400 Ma) intracratonic depositional system, which stretches across four states (WA, NT, SA and QLD) and is of fundamental scientific and economic significance to Australia. Sedimentary sequences within the CSB, comprising the Amadeus/Warburton, Georgina and Officer Basins, record a critical phase of Earth history, encompassing the Neoproterozoic rise of atmospheric oxygen, major reorganisations in the global carbon cycle and the emergence of the first complex life.
Publisher: Geological Society of London
Date: 03-03-2020
DOI: 10.1144/JGS2019-132
Publisher: California Digital Library (CDL)
Date: 02-04-2022
DOI: 10.31223/X5NH0G
Abstract: Continental rifts have a significant role in supercontinent breakup, and the development of sedimentary basins. The Australian Adelaide Superbasin is one of the largest and best-preserved rift systems that initiated during the breakup of Rodinia, yet substantial challenges still hinder our understanding of its early evolution and place within the Rodinian supercontinent. In the past decade, our understanding of rift and passive margin development, mantle plumes and their role in tectonics, geodynamics of supercontinent breakup, and sequence stratigraphy in tectonic settings has advanced significantly, however literature on the early evolution of the Adelaide Superbasin has not been updated to reflect these advancements. Using new detrital zircon age data for provenance, combined with existing literature, we examine the earliest tectonic evolution of the Adelaide Superbasin in the context of our modern understanding of rift system development. A new maximum depositional age of 893 ± 9 Ma from the lowermost stratigraphic unit provides a revised limit on the initiation of sedimentation and rifting within the basin. Our model suggests that the basin evolved through an initial pulse of extension exploiting pre-existing crustal weakness to form half-grabens. Tectonic quiescence and stable subsidence followed, with deposition of a sourceward-shifting facies tract. Emplacement and extrusion of the Willouran Large Igneous Province occurred at c. 830 Ma initiating a new phase of rifting. This rift renewal led to widespread extension and subsidence with deposition of the Curdimurka Subgroup, which constitutes the main cyclic rift sequence in the Adelaide Superbasin. Our model suggests that the Adelaide Superbasin formed through rift propagation an apparent triple junction, rather than apical extension outwards from this point. Additionally, we provide evidence suggesting a late Mesoproterozoic zircon source to the east of the basin, and show that the lowermost stratigraphy of the Centralian Superbasin, which is thought to be deposited coevally, had different primary detrital sources.
Publisher: Copernicus GmbH
Date: 23-03-2022
Publisher: Springer Science and Business Media LLC
Date: 26-03-2019
DOI: 10.1038/S41598-019-40783-4
Abstract: Precambrian hydrocarbons and their corresponding source rocks are distinctly different from their Phanerozoic counterparts, having been deposited in persistently anoxic environments in ecosystems dominated by bacteria. Here, we show that cyclic enrichment of organic matter in the world’s oldest hydrocarbon play (ca. 1.38 Ga), is not associated with flooding surfaces and is unrelated to variations in mineralogy or changes in the relative rate of clastic to biogenic sedimentation—factors typically attributed to organic enrichment in Phanerozoic shales. Instead, the cyclic covariation of total organic carbon, δ 15 N, δ 13 C and molybdenum are explained by the feedback between high levels of primary productivity, basin redox and the biogeochemical nitrogen cycle. These factors are important in constraining productivity in the marine biosphere, the development of Precambrian hydrocarbon source rocks, and more generally in understanding oxygenation of the ocean and atmosphere through Earth history as all are ultimately related to organic carbon burial.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-3173
Abstract: & & There is a view that a supercontinent, called Pannotia, existed for a short time at the end of the Neoproterozoic. This hypothetical continent requires collision between Neoproterozoic India, Australia-Mawson and the African and South American continents to occur before formation of Iapetus as Laurentia rifted off Amazonia.& & & & Data from the last decade demonstrate the complexity of consumption of the Mozambique Ocean that separated Neoproterozoic India from the African Neoproterozoic continents (Congo-Tanzania-Bangweulu, the Sahara Metacraton and Kalahari). In particular, the presence of pre-Neoproterozoic terranes that lie within the East African Orogen of Arabia, east Africa, Madagascar and South India demonstrate the multi-phase collision of the this ocean closure?. Here we examine the Cryogenian to Cambrian tectonic geography of the closure of the Mozambique Ocean from a full-plate perspective. We focus on the northern East African Orogen, where Gondwana-formation shortening and crustal thickening has been considerably less than seen in East Africa/Madagascar/South India. We focus on the Neoproterozoic India& #8211 Azania& #8211 Sahara Metacraton collision represented by the northernmost part of Madagascar (the Bemarivo Domain), and throughout Arabia. We conclude that final ocean closure and formation of central Gondwana occurred in the latest Ediacaran and into the Cambrian, along a suture that passes under the Rub' al Khali region of Arabia and through the northeast of Madagascar. It separates the extended Neoproterozoic India margin (now in Oman, The Seychelles and the northern Bemarivo Domain), from the growing kernel of Gondwana (the east-most parts preserved in Saudi Arabia, Yemen and Central Madagascar).& & & & Considering the early Ediacaran formation of Iapetus, there is growing evidence that Pannotia never existed as connected continental crust, yet the & #8216 Pannotian geodynamic cell& #8217 with lithosphere ided into continental and oceanic hemispheres had formed. The closure of the Mozambique Ocean represented the termination of & million years of subduction at this locale. The termination of this subduction with the formation of Gondwana, and the initiation of the Terra Australis Orogen led to the present geodynamic configuration.& &
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-12458
Abstract: & & The greater McArthur Basin is a regionally extensive Palaeo-to-Mesoproterozic, intra-cratonic, super basin system overlying the North Australian craton. Deposition initiated after the Pine Creek Orogeny whereby the basin extends from Western Australia to northwestern Queensland. Lithostratigraphic units are ided into five coherent packages of similar age, stratigraphic position and facies association. Successions of the basin system are dominated by an assemblage of sedimentary siliciclastics, evaporitic carbonates and organic-rich mudstones with minor intersections of volcanic rocks and records nearly a billion years of Earth& #8217 s history from ca. 1.82 Ga to the Tonian. This period has generally been considered a time of stability within the Earth system and is therefore unfortunately titled & #8216 the boring billion& #8217 . However, compilation of new and existing water chemistry proxies shown in this study reflected the contrary. Notably, shales and carbonates from the greater McArthur Basin chronicled a critical time in Earth& #8217 s history where the oxygenation of the ocean and atmosphere began and multi-cellular eukaryotes started to thrive within the ecosystem, demonstrating that this interval in the geological record is anything but boring.& & & & This study applied a multi-proxy approach based on observations of isotopic tracers and elemental variations from an extensive archive of carbonate-rich units throughout the greater McArthur Basin to reconstruct its palaeoenvironment, determine the tectonic setting and establish regional or global correlations. Elucidating the evolution of the basin is essential for understanding the controls of its petroleum and mineral resources as well as how Earth system processes developed during the Proterozoic. Radiogenic and stable isotopes are used to infer palaeo-depositional constraints such as biological productivity, weathering fluxes and provenance sources. Redox-sensitive elemental concentrations can also be used to reflect the changes in water-column chemistry between oxic, anoxic and euxinic conditions.& & & & Consequently, results from this study illustrate the relationship between the precipitation of metal compounds, production of organic matter and preservation of both systems with large-scale biogeochemical processes. Furthermore, this study also highlights the spatial and temporal variations of water chemistry within the basin. Enrichment in Mo concentrations in the Wollogorang Formation within the Tawallah Group indicated spells of widespread euxinia. Base metal concentrations within the unit showed lithogeochemical, halo-like distribution that is strongly correlated with changes in water column redox conditions. A shift to more radiogenic & sup& & /sup& Sr/& sup& & /sup& Sr values up to & #8764 .722 in the Fraynes Formation of the Limbunya Group reflected an increase in relative contribution of strontium from old continental crust in contrast to hydrothermal input which is consistent with a transient basin restriction from the open ocean. Rare earth and yttrium (REY) plots of the Dook Creek Formation inferred parts of the basin may have been lacustrine at ca. 1.5 Ga. Further up stratigraphy, the Middle Velkerri showed a shift towards more positive & #949 & sub& Nd(t)& /sub& values, representing a change to more juvenile source regions. These mafic provenances are richer in essential nutrients for biological activity such as phosphorus. More juvenile & #949 & sub& Nd(t) & /sub& data within the Velkerri Formation coincide with an increase in P concentrations and total organic carbon content (& wt. %).& &
Publisher: Copernicus GmbH
Date: 06-09-2022
DOI: 10.5194/GCHRON-4-577-2022
Abstract: Abstract. Recent developments in tandem laser ablation mass spectrometer technology have demonstrated the capacity for separating parent and daughter isotopes of the same mass online. As a result, beta-decay chronometers can now be applied to the geological archive in situ as opposed to through traditional whole-rock digestions. One novel application of this technique is the in situ Rb–Sr dating of Proterozoic shales that are dominated by authigenic clays such as illite. This method can provide a depositional window for shales by differentiating signatures of early diagenetic processes versus late-stage secondary alteration. However, the hydrothermal sensitivity of the Rb–Sr isotopic system across geological timescales in shale-hosted clay minerals is not well understood. As such, we dated the Mesoproterozoic Velkerri Formation from the Altree 2 well in the Beetaloo Sub-basin (greater McArthur Basin), northern Australia, using this approach. We then constrained the thermal history of these units using common hydrocarbon maturity indicators and modelled effects of contact heating due to the intrusion of the Derim Derim Dolerite. In situ Rb–Sr dating of mature, oil-prone shales in the diagenetic zone from the Velkerri Formation yielded ages of 1448 ± 81, 1434 ± 19, and 1421 ± 139 Ma. These results agree with previous Re–Os dating of the unit and are interpreted as recording the timing of an early diagenetic event soon after deposition. Conversely, overmature, gas-prone shales in the anchizone sourced from deeper within the borehole were dated at 1322 ± 93 and 1336 ± 40 Ma. These ages are younger than the expected depositional window for the Velkerri Formation. Instead, they are consistent with the age of the Derim Derim Dolerite mafic intrusion intersected 800 m below the Velkerri Formation. Thermal modelling suggests that a single intrusion of 75 m thickness would have been capable of producing a significant hydrothermal perturbation radiating from the sill top. The intrusion width proposed by this model is consistent with similar Derim Derim Dolerite sill thicknesses found elsewhere in the McArthur Basin. The extent of the hydrothermal aureole induced by this intrusion coincides with the window in which kerogen from the Velkerri Formation becomes overmature. As a result, the mafic intrusion intersected here is interpreted to have caused kerogen in these shales to enter the gas window, induced fluids that mobilize trace elements, and reset the Rb–Sr chronometer. Consequently, we propose that the Rb–Sr chronometer in shales may be sensitive to temperatures of ca. 120 ∘C in hydrothermal reactions but can withstand temperatures of more than 190 ∘C in thermal systems not dominated by fluids. Importantly, this study demonstrates a framework for the combined use of in situ Rb–Sr dating and kerogen maturation indicators to help reveal the thermochronological history of Proterozoic sedimentary basins. As such, this approach can be a powerful tool for identifying the hydrocarbon potential of source rocks in similar geological settings.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-3171
Abstract: & & Plate reorganization events are a characteristic of plate tectonics that punctuate the Phanerozoic. They fundamentally change the lithospheric plate-motion circuit, influencing the planet& #8217 s tectonic-mantle system and both ocean and atmospheric circulation through changes in bathymetry and topography. The development of full-plate reconstructions for deep time allows the geological record to be interrogated in a framework where plate kinematic reorganizations can be explored. Here, the geological record of the one of the most extensive tracts of Neoproterozoic crust on the planet (the Arabian-Nubian Shield) is interpreted to reflect a late Tonian plate reorganization at ca. 800-715 Ma that switched plate-convergence directions in the Mozambique Ocean, bringing Neoproterozoic India towards both the African cratons and Australia-Mawson, instigating the closure of the intervening ocean and the future amalgamation of central Gondwana ca. 200 million years later. This plate kinematic change is coeval with constraints on break-up of the core of Rodinia between Australia-Mawson and Laurentia and Kalahari and Congo.& &
Publisher: Elsevier BV
Date: 11-2020
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-12412
Abstract: & & There is still little known about the occurrence, formation and spatial distribution of long-lived cratonic basins that form during hundreds of millions of years of subsidence. Their histories often span multiple phases of super-continent break-up, dispersal and amalgamation. Each of these phases resulted in the modification of sedimentation rates and drainage within the basins but the broader basin persisted. These changing conditions are recorded in the detrital zircon record, providing a tool for understanding the basin evolution and consequently its palaeogeography.& & & & The informally termed greater McArthur Basin is a regionally extensive Proterozoic basin that overlies the North Australian Craton. It is a vast sedimentary system that stretches across the northern part of the Northern Territory from north-eastern Western Australia to north-western Queensland. It includes Palaeo- to Mesoproterozoic successions of the McArthur and Birrindudu basins, the Tomkinson Province and likely the Lawn Hill Platform and South Nicholson Basin (to the south-east) all interpreted to be contemporaneous systems. However, the full extent of the greater McArthur Basin sedimentary system is still being unravelled. The basin records nearly one billion years of Earth history, from ca. 1.82 Ga to ca. 0.85 Ma. This sedimentary system temporally overlaps with episodes of Palaeo- to Mesoproterozoic tectonism and igneous activity that affected underlying and adjacent terranes, including the Aileron, Warumpi and Musgrave provinces to the present-day south, Pine Creek Orogen and Arnhem Province to the north, Halls Creek Orogen and Tanami Region to the west, and Mount Isa and Murphy provinces to the east. & & & & & LA-ICP-MS detrital zircon U& #8211 Pb geochronology and Lu& #8211 Hf isotope data provide new constraints on the lower sedimentary successions of the McArthur Basin (Tawallah and Katherine River Groups) and demonstrate they are coetaneous with the Tomkinson Province (Tomkinson Creek Group). U& #8211 Pb detrital zircon data show major & sup& & /sup& Pb /& sup& & /sup& Pb peaks at ca. 1860 Ma and ca. 2500& #8211 Ma in both the McArthur Basin and Tomkinson Province sediments. Combined with Lu& #8211 Hf isotope data, the detrital zircon age data from the McArthur Basin show similarities to the Aileron Province (to the south) and magmatic rocks of the Gawler Craton, suggesting that these terranes might be possible source areas. Comparatively, the oldest succession within the Tomkinson Province (Hayward Creek Formation), shows similar spectra to units within the Lawn Hill Platform succession (McNamara Group, Surprise Creek Sandstone and Carrara Range Group) possibly suggesting a correlation between the two areas.& & & & Here we explore the links between the North Australia Craton and surrounding continents to further elucidate the evolution of this enigmatic basin throughout the Proterozoic. New palaeogeographic reconstructions link the & #8216 greater& #8217 McArthur basin to the Yanliao Basin and coeval rocks in the North China Craton. The & #8216 greater& #8217 McArthur basin may also have extended into southern Australia, Laurentia and Siberia as a vast intra-continental gulf (the McArthur-Yanliao Gulf) within the core of the supercontinent Nuna/Colombia.& &
Publisher: California Digital Library (CDL)
Date: 23-07-2023
DOI: 10.31223/X50G9N
Abstract: The glaciogenic nature of the Yudnamutana Subgroup was first identified over a century ago, and its global significance was recognised shortly after, eventually culminating with the global Sturtian Glaciation and Snowball Earth theory. Much debate on the origin and timing of these rocks, locally and globally, has ensued in the years since. A significant corpus of research on the lithology, sedimentology, geochronology, and formal lithostratigraphy of these sequences globally has attempted to resolve many of these debates. In the type area for the Sturtian Glaciation, South Australia’s Adelaide Superbasin, lithostratigraphy and sedimentology have been well understood however, formal stratigraphic nomenclature has remained complicated and contested. Geochronology has also been extremely sparse in this area. The result of these longstanding issues has been disagreement as to whether the sedimentary rocks of the Yudnamutana Subgroup are truly correlative throughout South Australia, and if they were deposited in the same time window recently defined for Sturtian glacial rocks globally, c. 717 Ma to c. 660 Ma. In this study we present a large detrital zircon study, summarise and compile existing global geochronology for the Sturtian Glaciation, and provide an updated formal lithostratigraphy. We show equivalence of the rocks that comprise the revised Sturt Formation of the Yudnamutana Subgroup, and that it was deposited within the time span globally defined for Sturtian Glaciation.
Publisher: Cambridge University Press (CUP)
Date: 23-12-2020
DOI: 10.1017/S0016756820001223
Abstract: The c. 1.5–1.3 Ga Wilton package, the upper succession of the greater McArthur Basin, preserves detailed tectono-sedimentary evidence for the Mesoproterozoic evolution of the North Australian Craton (NAC). In addition, it is a valuable global sedimentary repository for the poorly explored Mesoproterozoic. New detrital zircon U–Pb age and Lu–Hf isotope data, collected from multiple, geographically separated, basins that make up the Wilton package, are compiled with previously published data to illuminate the basin evolution. The spatial and temporal variation in sedimentary provenance illustrates two major geographic changes that correspond to continent-scale tectonic convulsions of the NAC during the Mesoproterozoic. The first is shown by the influx of sediment sourced from east and southeast terranes. This is linked to rifting between Proterozoic Australia and Laurentia at c . 1.45 Ga, resulting in the uplift of the eastern margin of the NAC–SAC (South Australian Craton). The second basin geographic change is illustrated by a flux of southerly-sourced detritus that is interpreted to be tectonically driven by the uplift of the southern NAC, during the subduction/closure of the Mirning Ocean at c. 1.32 Ga. Spatially, sediment in the Wilton package is separated into two depositional systems: sedimentary rocks within the Birrindudu Basin, the western component of the Wilton package, have different detrital signatures relative to other Wilton package successions found east of the Daly Waters Fault Zone, in the Beetaloo Sub-basin, the McArthur Basin and the South Nicholson Basin. The Daly Waters Fault Zone is interpreted as an ancient bathymetric high, blocking sediment transport. Although they differ in sources, rocks in both the Birrindudu Basin and the eastern Wilton package record coeval shifts of basin provenance to southern sources. The coherent evolution of basin provenance indicates a consistent tectono-sedimentation history, and links the Birrindudu Basin and the other Wilton successions in a tectonic framework.
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 12-2018
Publisher: Geological Society of London
Date: 09-05-2019
DOI: 10.1144/JGS2018-159
Publisher: Elsevier BV
Date: 09-2018
Publisher: Cambridge University Press (CUP)
Date: 07-2023
DOI: 10.1017/S0016756823000390
Abstract: The glaciogenic nature of the Yudnamutana Subgroup was first recognized over a century ago, and its global significance was recognized shortly after, with the eventual postulation of a global Sturtian Glaciation and Snowball Earth theory. Much debate on the origin and timing of these rocks, locally and globally, has ensued in the years since. A significant corpus of research on the lithology, sedimentology, geochronology and formal lithostratigraphy of these sequences globally has attempted to resolve many of these debates. In the type area for the Sturtian Glaciation, South Australia’s Adelaide Superbasin, the lithostratigraphy and sedimentology are well understood however, formal stratigraphic nomenclature has remained complicated and contested. Absolute dates on the stratigraphy are also extremely sparse in this area. The result of these longstanding issues has been disagreement as to whether the sedimentary rocks of the Yudnamutana Subgroup are truly correlative throughout South Australia, and if they were deposited in the same time span recently defined for Sturtian glacial rocks globally, c. 717 Ma to c. 660 Ma. This study presents a large detrital zircon study, summarizes and compiles existing global geochronology for the Sturtian Glaciation and revises the formal lithostratigraphic framework of the Yudnamutana Subgroup. We show equivalence of the rocks that comprise the revised Sturt Formation, the main glaciogenic unit of the Yudnamutana Subgroup, and that it was deposited within the time span globally defined for the Sturtian Glaciation.
Publisher: Elsevier BV
Date: 11-2018
Publisher: Copernicus GmbH
Date: 23-03-2022
Abstract: Abstract. Recent developments in tandem laser ablation-mass spectrometer technology have been shown to be capable of separating parent and daughter isotopes of the same mass online. As a result, beta decay chronometers can now be applied to the geological archive in situ as opposed to through traditional whole-rock digestions. One novel application of this technique is the in situ Rb–Sr dating on Proterozoic shales that are dominated by authigenic clays. This method can provide a depositional window for shales by differentiating signatures of early diagenetic processes versus late-stage secondary alteration. However, the hydrothermal sensitivity of the Rb–Sr isotopic system across geological timescales in shale-hosted clay minerals is not well understood. As such, we dated the Mesoproterozoic Velkerri Formation from the Altree 2 well in the Beetaloo Sub-basin (greater McArthur Basin) using in situ Rb–Sr geochronology and constrained its thermal history using common hydrocarbon maturity indicators, and modelled effects of contact heating due to the intrusion of the Derim Derim Dolerite. In situ Rb–Sr dating of mature, oil-prone shales in the diagenetic zone from the Velkerri Formation in this study yielded ages of 1470 ± 102 Ma, 1457 ± 29 Ma, and 1421 ± 152 Ma. These results agree with previous Re–Os dating of the unit and are interpreted as recording the timing of an early diagenetic event soon after deposition. Conversely, overmature, gas-prone shales in the anchizone sourced from stratigraphically deeper within the same borehole and succession were dated at 1318 ± 105 Ma and 1332 ± 67 Ma. These ages are younger than the expected depositional window for the Velkerri Formation. Instead, they are consistent with the age of the Derim Derim Dolerite mafic intrusion intersected 800 m below the Velkerri Formation. Thermal modelling suggests that a single intrusion of 75 m thickness would have been capable of producing a significant hydrothermal perturbation radiating from the sill top. The intrusion width proposed by this model is consistent with similar Derim Derim Dolerite sill thicknesses found elsewhere in the McArthur Basin. The extent of the hydrothermal aureole induced by this intrusion coincide with the point in which kerogen from the Velkerri Formation becomes overmature. As a result, the mafic intrusion intersected here is interpreted to have caused kerogen in these shales to enter the gas window, induced fluids that mobilise trace elements and resetting the Rb–Sr chronometer. Consequently, we propose that the Rb–Sr chronometer in shales may be sensitive to temperatures of ca. 110 °C in hydrothermal reactions but can withstand temperatures of more than 190 °C in thermal systems absent of fluid. Importantly, this study demonstrates a framework for the combined use of in situ Rb–Sr dating and kerogen maturation indicators to help reveal the thermochronological history of Proterozoic sedimentary basins. As such, this approach can be a powerful tool for identifying the hydrocarbon potential of source rocks in similar geological settings.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Cambridge University Press (CUP)
Date: 07-03-2018
DOI: 10.1017/S0016756817000061
Abstract: The Omani basement is located spatially distant from the dominantly juvenile Arabian–Nubian Shield (ANS) to its west, and its relationship to the amalgamation of those arc terranes has yet to be properly constrained. The Jebel Ja'alan (NE Oman) basement inlier provides an excellent opportunity to better understand the Neoproterozoic tectonic geography of Oman and its relationship to the ANS. To understand the origin of this basement inlier, we present new radiogenic isotopic data from igneous bodies in Jebel Ja'alan. U–Pb and 40 Ar/ 39 Ar geochronological data are used to constrain the timing of magmatism and metamorphism in the jebel. Positive εHf and εNd values indicate a juvenile origin for the igneous lithologies. Phase equilibria modelling is used to constrain the metamorphic conditions recorded by basement. Pressure–temperature ( P – T ) pseudosections show that basement schists followed a clockwise P–T path, reaching peak metamorphic conditions of c. 650–700°C at 4–7.5 kbar, corresponding to a thermal gradient of c. 90–160°C/kbar. From the calculated thermal gradient, in conjunction with collected trace-element data, we interpret that the Jebel Ja'alan basement formed in an arc environment. Geochronological data indicate that this juvenile arc formed during Tonian time and is older than basement further west in Oman. We argue that the difference in timing is related to westwards arc accretion and migration, which implies that the Omani basement represents its own tectonic domain separate to the ANS and may be the leading edge of the Neoproterozoic accretionary margin of India.
Publisher: California Digital Library (CDL)
Date: 31-01-2022
DOI: 10.31223/X52S4G
Abstract: Recent progress in plate tectonic reconstructions has seen models move beyond the classical idea of continental drift by attempting to reconstruct the full evolving configuration of tectonic plates and plate boundaries. A particular problem for the Neoproterozoic and Cambrian is that many existing interpretations of geological and palaeomagnetic data have remained disconnected from younger, better-constrained periods in Earth history. An important test of deep time reconstructions is therefore to demonstrate the continuous kinematic viability of tectonic motions across multiple supercontinent cycles. We present, for the first time, a continuous full-plate model spanning 1 Ga to the present-day, that includes a revised and improved model for the Neoproterozoic–Cambrian (1000–520 Ma) that connects with models of the Phanerozoic, thereby opening up pre-Gondwana times for quantitative analysis and further regional refinements. In this contribution, we first summarise methodological approaches to full-plate modelling and review the existing full-plate models in order to select appropriate models that produce a single continuous model. Our model is presented in a palaeomagnetic reference frame, with a newly-derived apparent polar wander path for Gondwana from 540 to 320 Ma, and a global apparent polar wander path from 320 to 0 Ma. We stress, though while we have used palaeomagnetic data when available, the model is also geologically constrained, based on preserved data from past-plate boundaries. This study is intended as a first step in the direction of a detailed and self-consistent tectonic reconstruction for the last billion years of Earth history, and our model files are released to facilitate community development.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-3184
Abstract: & & The Adelaide Rift Complex is a large sedimentary superbasin in South Australia that formed resultant of Rodinia& #8217 s breakup and subsequent evolution of the Australian passive margin of the Pacific basin. It holds a globally significant and exceptionally well-preserved Neoproterozoic& #8211 early Cambrian succession. Much work has been done over the last century describing the lithostratigraphy and sedimentology of this vast basin. The rift complex contains evidence for major changes in Earth& #8217 s systems, yet, the rocks are poorly dated, and the sediment provenance, and link with tectonic evolution, is remarkably poorly known.& & & & This work provides a centralised database of the currently available, and previously unpublished, detrital zircon geochronology for the Neoproterozoic of the Adelaide Rift Complex, highlighting where the available data is from, and the stratigraphic and spatial gaps in our knowledge. By subjecting the U& #8211 Pb detrital zircon data to data analytical techniques, we provide a first look overview of the change in provenance, and subsequently (generalised) palaeo-tectonogeography that this suggests during the Neoproterozoic. These data show a change from dominantly local sources in the middle Tonian, to dominantly far-field sources as the rift-basin develops over time. The Cryogenian icesheets punctuate this with an ephemeral return to more local sources from nearby rift shoulders. This effect is particularly apparent during the Sturtian Glaciation than in the younger Marinoan Glaciation. In the Ediacaran, we see an increasingly stronger influence of younger (& Ma) detrital zircons from an enigmatic source that we interpret to be from southern (i.e. Antarctic) sources. We also note that we see a slight shift in the late Mesoproterozoic age peaks, from ca. 1170 Ma to ca. 1090 Ma, with a corresponding decrease in older ca. 1600 Ma detritus.& & & & This work forms the basis of continuing work to improve our understanding of the geochronology, provenance and palaeo-tectonogeography of the Adelaide Rift Complex.& &
Publisher: Petroleum Exploration Society of Australia (PESA)
Date: 30-08-2022
DOI: 10.36404/DYHY1639
Abstract: Recent developments in tandem laser ablation-mass spectrometer technology have been shown to be capable of separating parent and daughter isotopes of the same mass online. Consequently, beta decay chronometers can now be applied to the geological archive in situ as opposed to through traditional whole-rock digestions. This new technique provides quicker and cheaper acquisition of geochronological and geochemical data whilst still maintaining a s le’s petrographic context.
Publisher: California Digital Library (CDL)
Date: 24-03-2022
DOI: 10.31223/X5N63H
Abstract: The late Tonian sequences of the Adelaide Superbasin were witness to the birth of the proto-Pacific Ocean during the breakup of Rodinia. Understanding the sedimentology and provenance of these rocks from across the basin is key to understanding both their deposition over ~70 million years, the local palaeogeography, and leads to a better understanding of the early development of the proto-Pacific Ocean. While the sedimentology of the Burra Group is well studied in most areas, provenance studies on these sequences using detrital zircon have been limited in scope and lack both spatial and temporal ersity. In this study we begin to address this knowledge gap. S les were taken from across the Adelaide Superbasin to understand both spatial and temporal related changes in provenance. Our findings highlight the necessity of this approach by uncovering both subtle, and abrupt significant changes in detrital zircon spectra for coeval s les from across the basin, and up-sequence in local areas. Our results highlight significant changes in provenance c. 790 Ma in the north of the basin, and c. 740 Ma in the south of the basin. This suggests a southward propagation of the rift basin, gradually opening to southerly sediment supply. Additionally, we posit the existence of an unrecognised source of c. 1000–900 Ma zircon to the north or northeast of the basin to account for latest Stenian to earliest Tonian detrital zircon in the Myrtle Springs Formation.
Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 05-2018
No related organisations have been discovered for Morgan Blades.
Start Date: 06-2023
End Date: 06-2026
Amount: $405,000.00
Funder: Australian Research Council
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