Добірка наукової літератури з теми "Centralian Superbasin"

Abstract Hafnium (Hf) isotope composition of zircon has been integrated with U-Pb age to form a long-term (>4 b.y.) record of the evolution of the crust. In contrast, trace element compositions of zircon are most commonly utilized in local- or regional-scale petrological studies, and the most noteworthy applications of trace element studies of detrital zircon have been in “fingerprinting” potential source lithologies. The extent to which zircon trace element compositions varied globally over geological time scales (as, for example, zircon U-Pb age abundance, O isotope composition, and Hf isotope composition seem to have varied) has been little explored, and it is a topic that is well suited to the large data sets produced by detrital zircon studies. In this study we present new detrital zircon U-Pb ages and trace element compositions from a continent-scale basin system in Australia (the Centralian Superbasin) that bear directly on the Proterozoic history of Australia and which may be applicable to broader interpretations of plate-tectonic processes in other regions. U-Pb ages of detrital zircon in the Centralian Superbasin are dominated by populations of ca. 1800, 1600, 1200, and 600 Ma, and secular variations of zircon Hf isotope ratios are correlated with some trace element parameters between these major age populations. In particular, elevated εHf(i) (i.e., radiogenic “juvenile” Hf isotope composition) of detrital zircon in the Centralian Superbasin tends to correspond with relatively high values of Yb/U, Ce anomaly, and Lu/Nd (i.e., depletion of light rare earth elements). These correlations seem to be fundamentally governed by three related factors: elemental compatibility in the continental crust versus mantle, the thickness of continental crust, and the contributions of sediment to magmas. Similar trace element versus εHf(i) patterns among a global zircon data set suggest broad applicability. One particularly intriguing aspect of the global zircon data set is a late Neoproterozoic to Cambrian period during which both zircon εHf(i) and Yb/U reached minima, marking an era of anomalous zircon geochemistry that was related to significant contributions from old continental crust.

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 the 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 to an apparent triple junction, rather than apical extension outward from this point. In addition, 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.

Queensland contains a number of carbonate-bearing basins which are under-explored for petroleum, but contain the elements of potentially economic petroleum systems. The oldest such basin is the Neoproterozoic to Ordovician Georgina Basin which straddles the Queensland-Northern Territory border and is traversed by the Ballera to Mount Isa gas pipeline.The basin developed across several major crustal blocks resulting in regional variations in deposition and deformation. Thick Neoproterozoic rocks of the Centralian Superbasin form the base of the sequence in apparently fault-bounded, extensional sub-basins. These rocks are generally tight and source rocks are unknown. The Cambrian to Ordovician rocks have the best petroleum potential with the most prospective part of the basin being the Toko Syncline. The Burke River Structural Belt is less prospective, but is worthy of further exploration. Basin fill consists of Cambrian and Early Ordovician rocks which are dominantly carbonates, with both limestones and dolostones present. In the Early to Middle Ordovician, the rocks became predominantly siliciclastic.The main phase of deformation affecting the Georgina Basin occurred in the Devonian as part of the Alice Springs Orogeny. The Toomba Fault, which forms the western boundary of the asymmetric Toko Syncline, is a thrust fault with up to 6.5 km of uplift. The angle of thrusting is between less than 40 degrees and up to 70 degrees. Rich, marine source rocks of Middle Cambrian age in the Toko Syncline are mature for oil except in the deepest part of the syncline where they are mature for dry gas. The deeper part of the Toko Syncline may be gas saturated.Potential hydrocarbon targets include large folds associated with fault rollovers, stratigraphic traps and faultbounded traps. Vugular, secondary porosity in dolostones offers the best chance for commercial reservoirs within the Ninmaroo and Kelly Creek formations and Thorntonia Limestone. There are also oolitic carbonates which may have good primary porosity, as well as interbedded sandstones in the carbonates with preserved porosity. Structurally controlled hydrothermal dolomite facies represent potential reservoirs. The dominantly siliciclastic Ordovician sequence is water flushed. Fracture porosity is another possibility (cf. the Palm Valley gas field in the Amadeus Basin). As the deeper part of the Toko Syncline appears to be gas saturated, there may be potential for basin-centred gas. Fine-grained carbonates and shales provide excellent seals. There has not been a valid structural test; although AOD Ethabuka–1 flowed 7,000 m3/d of dry gas, the well was abandoned short of the target depth.

Dating of remnant detrital zircon from high-grade metasediments of the Harts Range Group (HRG) in central Australia shows that the sedimentary protoliths were deposited during the Neoproterozoic to Cambrian, demonstrably younger than Palaeoproterozoic metamorphic rocks of the surrounding Arunta Inlier. The inferred depositional age of the HRG indicates that it was deposited at the same time as sedimentary rocks of the former Centralian Superbasin, now represented by the Amadeus and Georgina structural basins adjacent to the Harts Range. Detrital zircon data from the sedimentary rocks in these basins show that both the unmetamorphosed and high-grade metamorphic sequences shared common source regions and display similar provenance changes with time. These similarities imply that the HRG is the high-grade metamorphic equivalent of the Centralian Superbasin, meaning that the well-studied patterns of sedimentation in the basin can be used to constrain tectonism that occurred at mid- to lower-crustallevels in the Harts Range. The detrital zircon data indicate that the HRG extends at least 100 km east of the Harts Range, possibly grading eastwards beneath cover into unmetamorphosed sedimentary rocks of the Warburton Basin. Granitoids from the lower part of the HRG have Early Cambrian crystallisation ages of - 520 Ma, around 45 million years older than metamorphism recorded by metamorphic zircon, which has ages between -475-460 Ma (the Larapinta Event). The granites appear to have been derived from partial melting of their Early Cambrian host rocks and were coeval with mafic magmas, forming a bimodal igneous complex. During the Early Cambrian, deposition in the Centralian Superbasin adjacent to the Harts Range was clastic-poor and was accompanied by a marine transgression in the southern part of the Georgina Basin, implying that the Harts Range region was actively subsiding. Deeperwater pelitic sedimentation in the Harts Range area at this time and the presence of bimodal magmatism are consistent with an extensional setting for Early Cambrian partial melting and magmatism, here termed the Stanovos Event. Continued extension and subsidence resulted in the formation of a shallow marine seaway across central Australia in the Early Ordovician, below which granulite-facies metamorphism of the HRG took place at -10-12 kbar (-30-35 km). This metamorphism was accompanied by the formation of a pervasive layer-parallel foliation and the intrusion of syn-tectonic mafic dykes. Rare metamorphic and igneous zircon ages at -475 Ma possibly date peak metamorphism of the Larapinta Event, while widespread metamorphic zircon overgrowths at -460 Ma are probably related to retrograde metamorphism. Burial of the HRG to lower crustal levels is interpreted to have taken place in a rift or transtensional setting, implying that burial took place primarily by sediment loading within an actively subsiding basin (the Irindina sub-basin). The -30-35 km depth of metamorphism indicated by thermobarometric data imply that the Irindina sub-basin was deeper than any other known basin in Earth history. Potential field modelling of magnetic and gravity data was unable to distinguish whether a prominent linear gravity high in the Harts Range region is due to a preserved thick remnant of the Irindina Sub-basin or a large mafic body in the lower crust. However, the intensity of the anomaly indicates that a large accumulation of mafie material is present at depth, consistent with the interpreted rift setting for both the Stanovos and Larapinta Events. U-Pb zircon dating of the Entia Gneiss Complex and adjacent Strangways Metamorphic Complex shows that Larapinta Event had little effect on the Palaeoproterozoic basement adjacent to the Irindina sub-basin, with evidence limited to rare Early Ordovician isotopic disturbance. This is consistent with the interpretation that the Larapinta Event took place within the lower part of a deep sub-basin rather than as a result of a contractional event that would have affected both the basement and cover sequences. Basin inversion and uplift closely followed the retrograde phase of the Larapinta Event, culminating in the Alice Springs Orogeny at --400-300 Ma. The HRG was exhumed at this time and thrust over Palaeoproterozoic basement of the Entia Gneiss Complex along a major crustal detachment. Metamorphic zircon overgrowths between -~360-330 Main both the basement and cover sequences, and granitoid intrusions in the HRG at -360 Ma confirm that the Alice Springs Orogeny was a major tectonothermal event in the Harts Range region. U-Pb dating of monazite indicates that the Entia Gneiss Complex was pervasively reworked by a flat-lying kyanite-grade foliation at - 336 Ma, which was subsequently deformed into a complex domal culmination, the Entia Dome. The flat-lying foliation and doming possibly reflecting extensional collapse towards the end of the Alice Springs Orogeny, following a prolonged period of N-S to NNE-SSW directed contraction.

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The Heavitree Formation of the Amadeus Basin, central Australia, is thought to correlate with a number of similar formations in the Officer, Ngalia, Georgina and Murraba Basins that formed the Centralian Superbasin. The Jasper Gorge Formation of the Victoria Basin and Jamison Sandstone of the Beetaloo Sub-basin are also thought to be corollaries. These formations are all constrained to being younger than ca. 1.0 Ga by U-Pb detrital zircon studies. However, in all cases, this is suspected to considerably pre-date the timing of deposition. Here, we present new U-Pb and Hf data from seven samples of the Amadeus Basin Heavitree Formation to a) better constrain the age of the Heavitree Formation, b) investigate the spatial variation in provenance of the Heavitree Formation, and, c) compare it with other ‘Supersequence 1’ quartzites from the wider Centralian Superbasin.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018