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Статті в журналах з теми "Delamerian Orogen"
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Mortimer, N., J. M. Palin, W. J. Dunlap, and F. Hauff. "Extent of the Ross Orogen in Antarctica: new data from DSDP 270 and Iselin Bank." Antarctic Science 23, no. 3 (February 8, 2011): 297–306. http://dx.doi.org/10.1017/s0954102010000969.
Повний текст джерелаАнотація:
AbstractThe Ross Sea is bordered by the Late Precambrian–Cambrian Ross–Delamerian Orogen of East Antarctica and the more Pacific-ward Ordovician–Silurian Lachlan–Tuhua–Robertson Bay–Swanson Orogen. A calcsilicate gneiss from Deep Sea Drilling Project 270 drill hole in the central Ross Sea, Antarctica, gives a U-Pb titanite age of 437 ± 6 Ma (2σ). This age of high-grade metamorphism is too young for typical Ross Orogen. Based on this age, and on lithology, we propose a provisional correlation with the Early Palaeozoic Lachlan–Tuhua–Robertson Bay–Swanson Orogen, and possibly the Bowers Terrane of northern Victoria Land. A metamorphosed porphyritic rhyolite dredged from the Iselin Bank, northern Ross Sea, gives a U-Pb zircon age of 545 ± 32 Ma (2σ). The U-Pb age, petrochemistry, Ar-Ar K-feldspar dating, and Sr and Nd isotopic ratios indicate a correlation with Late Proterozoic–Cambrian igneous protoliths of the Ross Orogen. If the Iselin Bank rhyolite is not ice-rafted debris, then it represents a further intriguing occurrence of Ross basement found outside the main Ross–Delamerian Orogen.
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Reid, Anthony, Marnie Forster, Wolfgang Preiss, Alicia Caruso, Stacey Curtis, Tom Wise, Davood Vasegh, Naina Goswami, and Gordon Lister. "Complex 40Ar ∕ 39Ar age spectra from low-grade metamorphic rocks: resolving the input of detrital and metamorphic components in a case study from the Delamerian Orogen." Geochronology 4, no. 2 (July 20, 2022): 471–500. http://dx.doi.org/10.5194/gchron-4-471-2022.
Повний текст джерелаАнотація:
Abstract. In this study, we provide 40Ar / 39Ar geochronology data from a suite of variably deformed rocks from a region of low-grade metamorphism within the Cambro–Ordovician Delamerian Orogen, South Australia. Low-grade metamorphic rocks such as these can contain both detrital minerals and minerals newly grown or partly recrystallised during diagenesis and metamorphism. Hence, they typically yield complex 40Ar / 39Ar age spectra that can be difficult to interpret. Therefore, we have undertaken furnace step heating 40Ar / 39Ar geochronology to obtain age spectra with many steps to allow for application of the method of asymptotes and limits and recognition of the effects of mixing. The samples analysed range from siltstone and shale to phyllite and contain muscovite or phengite with minor microcline as determined by hyperspectral mineralogical characterisation. Whole rock 40Ar / 39Ar analyses were undertaken in most samples due to their very fine-grained nature. All samples are dominated by radiogenic 40Ar, and contain minimal evidence for atmospheric Ca- or Cl-derived argon. Chloritisation may have resulted in limited recoil, causing 39Ar argon loss in some samples, which is especially evident within the first few percent of gas released. Most of the age data, however, appear to have some geological significance. Viewed with respect to the known depositional ages of the stratigraphic units, the age spectra from this study do appear to record both detrital mineral ages and ages related to the varying influence of either cooling or deformation-induced recrystallisation. The shape of the age spectra and the degree of deformation in the phyllites suggest the younger ages may record recrystallisation of detrital minerals and/or new mica growth during deformation. Given that the younger limit of deformation recorded in the high-metamorphic-grade regions of the Delamerian Orogen is ca. 490 Ma, the ca. 470 to ca. 458 Ma ages obtained in this study suggest deformation in low-grade shear zones within the Delamerian Orogen may have persisted until ca. 20–32 million years after high-temperature ductile deformation in the high-grade regions of the orogen. We suggest that these younger ages for deformation could reflect reactivation of older structures formed both during rift basin formation and during the main peak of the Delamerian orogeny itself. The younger ca. 470 to ca. 458 Ma deformation may have been facilitated by far-field tectonic processes occurring along the eastern paleo-Pacific margin of Gondwana.
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Adams, C. J., J. D. Bradshaw, and T. R. Ireland. "Provenance connections between late Neoproterozoic and early Palaeozoic sedimentary basins of the Ross Sea region, Antarctica, south-east Australia and southern Zealandia." Antarctic Science 26, no. 2 (July 18, 2013): 173–82. http://dx.doi.org/10.1017/s0954102013000461.
Повний текст джерелаАнотація:
AbstractThick successions of turbidites are widespread in the Ross–Delamerian and Lachlan orogens and are now dispersed through Australia, Antarctica and New Zealand. U-Pb detrital zircon age patterns for latest Precambrian, Cambrian and Ordovician metagreywackes show a closely related provenance. The latest Neoproterozoic–early Palaeozoic sedimentary rocks have major components, at c. 525, 550, and 595 Ma, i.e. about 40–80 million years older than deposition. Zircons in these components increase from the Neoproterozoic to Ordovician. Late Mesoproterozoic age components, 1030 and 1070 Ma, probably originate from igneous/metamorphic rocks in the Gondwanaland hinterland whose exact locations are unknown. Although small, the youngest zircon age components are coincident with estimated depositional ages suggesting that they reflect contemporaneous and minor, volcanic sources. Overall, the detrital zircon provenance patterns reflect the development of plutonic/metamorphic complexes of the Ross–Delamerian Orogen in the Transantarctic Mountains and southern Australia that, upon exhumation, supplied sediment to regional scale basin(s) at the Gondwana margin. Tasmanian detrital zircon age patterns differ from those seen in intra-Ross Orogen sandstones of northern Victoria Land and from the oldest metasediments in the Transantarctic Mountains. A comparison with rocks from the latter supports an allochthonous western Tasmania model and amalgamation with Australia in late Cambrian time.
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Foden, J. D., M. A. Elburg, S. P. Turner, M. Sandiford, J. O'Callaghan, and S. Mitchell. "Granite production in the Delamerian Orogen, South Australia." Journal of the Geological Society 159, no. 5 (September 2002): 557–75. http://dx.doi.org/10.1144/0016-764901-099.
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Foden, John, Marlina A. Elburg, Jon Dougherty‐Page, and Andrew Burtt. "The Timing and Duration of the Delamerian Orogeny: Correlation with the Ross Orogen and Implications for Gondwana Assembly." Journal of Geology 114, no. 2 (March 2006): 189–210. http://dx.doi.org/10.1086/499570.
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Shaanan, U., G. Rosenbaum, and F. M. H. Sihombing. "Continuation of the Ross–Delamerian Orogen: insights from eastern Australian detrital-zircon data." Australian Journal of Earth Sciences 65, no. 7-8 (August 21, 2017): 1123–31. http://dx.doi.org/10.1080/08120099.2017.1354916.
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Robertson, Kate, David Taylor, Stephan Thiel, and Graham Heinson. "Magnetotelluric evidence for serpentinisation in a Cambrian subduction zone beneath the Delamerian Orogen, southeast Australia." Gondwana Research 28, no. 2 (September 2015): 601–11. http://dx.doi.org/10.1016/j.gr.2014.07.013.
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Ireland, T. R., T. Flöttmann, C. M. Fanning, G. M. Gibson, and W. V. Preiss. "Development of the early Paleozoic Pacific margin of Gondwana from detrital-zircon ages across the Delamerian orogen." Geology 26, no. 3 (1998): 243. http://dx.doi.org/10.1130/0091-7613(1998)026<0243:dotepp>2.3.co;2.
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Kemp, A. I. S. "Plutonic boninite-like rocks in an anatectic setting: Tectonic implications for the Delamerian orogen in southeastern Australia." Geology 31, no. 4 (2003): 371. http://dx.doi.org/10.1130/0091-7613(2003)031<0371:pblria>2.0.co;2.
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Foden, J., M. Sandiford, J. Dougherty-Page, and I. Williams. "Geochemistry and geochronology of the Rathjen Gneiss: Implications for the early tectonic evolution of the Delamerian Orogen." Australian Journal of Earth Sciences 46, no. 3 (June 1999): 377–89. http://dx.doi.org/10.1046/j.1440-0952.1999.00712.x.
Повний текст джерелаДисертації з теми "Delamerian Orogen"
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Merrett, H. D. "2D lithospheric imaging of the Delamerian and Lachlan Orogens, southwestern Victoria, Australia from Broadband Magnetotellurics." Thesis, 2016. http://hdl.handle.net/2440/121124.
Повний текст джерелаАнотація:
This item is only available electronically.A geophysical study utilising the method of magnetotellurics (MT) was carried out across southwestern Victoria, Australia, imaging the electrical resistivity structure of the lithosphere beneath the Delamerian and Lachlan Orogens. Broadband MT (0.001-1000 Hz) data were collected along a 160 km west-southwest to east-northeast transect adjacent to crustal seismic profiling. Phase tensor analyses from MT responses reveal a distinct change in electrical resistivity structure and continuation further southwards of the Glenelg and Grampians-Stavely geological zones defined by the Yarramyljup Fault, marking the western limit of exploration interest for the Stavely Copper Porphyries. The Stawell and Bendigo Zones also show change across the Moyston and Avoca faults, respectively. Results of 2D modelling reveal a more conductive lower crust (10-30 Ωm) and upper mantle beneath the Lachlan Orogen compared to the Delamerian Orogen. This significant resistivity gradient coincides with the Mortlake discontinuity and location of the Moyston fault. Broad-scale fluid alteration zones were observed through joint analysis with seismic profiling, leaving behind a signature of low-reflectivity, correlating to higher conductivities of the altered host rocks. Isotopic analysis of xenoliths from western Victoria reveal the lithospheric mantle has undergone discrete episodes of modal metasomatism. This may relate to near-surface Devonian granite intrusions constrained to the Lachlan Orogen where we attribute the mid to lower crustal conductivity anomaly (below the Stawell Zone) as fossil metasomatised ascent paths of these granitic melts. This conductivity enhancement may have served to overprint an already conductive lithosphere, enriched in hydrogen from subduction related processes during the Cambrian. A predominately reflective upper crust exhibits high resistivity owing to turbidite and metasedimentary rock sequences of the Lachlan Orogen, representative of low porosity and permeability. Conductive sediments of the Otway Basin have also been imaged down to 3 km depth southwest of Hamilton.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2016
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Robertson, K. E. "An electrical resistivity model of the southeast Australian lithosphere and asthenosphere." Thesis, 2012. http://hdl.handle.net/2440/95433.
Повний текст джерелаАнотація:
This item is only available electronically.A combination of magnetotelluric and geomagnetic depth sounding data were used to attempt to image the electrical resistivity structure of southeast Australia, to investigate the physical state of the crust and upper mantle. A 3D forward model of southeast Australia comprised of regional sets of broadband and long-period magnetotelluric and geomagnetic depth sounding data, over an area of 440 x 300 km2, was used to map broad-scale lithospheric properties. Model results show an order of magnitude decrease in resistivity from the depleted continental mantle lithosphere of the Delamerian Orogen in the west, to the more conducting oceanic mantle of the Lachlan Orogen in the east. The decrease in resistivity in conjunction with a 0.1 km/s decrease in P-wave velocity at depths of 50-250 km, suggest a change in temperature (_T_200_C) due to lithospheric thinning toward the east as the likely cause, in conjuction with a change in geochemistry and/or hydration. A high resolution two-dimensional inversion using data from 37 new and 39 existing broadband magnetotelluric stations mapped crustal heterogeneity beneath the Delamerian Orogen in much greater detail. Lateral changes in resistivity from 10-10 000 m occur over the space of a few kilometres. Low resistivity (_10 m) regions occur at depths of 10-40 km. Narrow paths of low resistivity extend to the surface, coinciding with locations of crustal faults from seismic interpretations. Movement of mantle up these faults, during periods of extension prior to the Delamerian Orogen, may have produced a carbon-rich, low resistivity lower crust, leaving a resistive upper mantle, depleted of volatiles.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2012
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McDonald, G. D. "The petrology and timing of the Anabama Granite and associated igneous activity, Olary Region, SA." Thesis, 1992. http://hdl.handle.net/2440/122489.
Повний текст джерелаАнотація:
This item is only available electronically.Two ideologies of thought exist when models of granite genesis are considered. Do they represent the products of direct fractionation of a basaltic mantle melt, or, do they form in accordance with the restite model of White and Chappell (1977)? Assimilation and fractional crystallization (AFC) modelling of Nd - and Sr - isotopic data from the Anabama Granite, of this study, and data from the granites of the southern Adelaide Fold Belt, Antarctica and the Lachlan Fold Belt of New South Wales, all of approximately the same age, appears to reflect mixed sources with components derived both from an average Delamerian basalt composition and an average Archean crust composition. Results indicate that the Anabama Granite mostly represents primitive Delamerian basalt, contaminated by 12- 14 % Archean crustal material. Field relationships of the Anabama Granite indicate that it was the site of multiple magmatic intrusions, between approximately 490- 425 Ma. These intrusions are represented by several episodes of hydrothermal alteration and crosscutting dykes. A long-lived thermal source, not represented in the southern Adelaide Fold Belt, may be responsible for this ongoing magmatic activity. Examples of these dykes are the lamprophyre dyke, dated at 457 ± 18 Ma, which is similar in composition and appearance to the lamprophyres near Truro (South Australia) and the dacite porphyry dyke which crosscuts all other lithologies and was dated at 425 ± 13Ma. This age corresponds to the onset of thermal activity in the Lachlan Fold Belt, and therefore, leads to the suggestion that the region where the Anabama Granite outcrops may represent the western margin of the thermal perturbation responsible for the production of granitic melts in the Lachlan Fold Belt at around 400 Ma. Differences in source regions for the Anabama Granite, the granites of Antarctica and those of the Lachlan Fold Belt are recognized by the different Nd- and Sr - isotopic ratios, although all granites may represent the same process of formation, that being AFC. The dacite porphyry's isotopic signature indicates a more primitive source than that suggested for the Anabama Granite, and therefore its genesis does not represent a remelting of the Anabama Granite or of its source region. Geochemically, the Anabama Granite is similar to the Reedy Creek Granodiorite of the southern Adelaide Fold Belt and the Wanda Granodiorite of western Victoria. It can also be classified as an I-type granite using the criteria established by Chappell and White (1974). Geophysical gravity modelling of the Anabama Granite was carried out and it was found that the granite extends to a depth of approximately 15 km and dips uniformly to the north west. Thus giving an indication that fracture propagation, rather than plutonism, is the mechanism of granitic melt transport through the upper crust for the Anabama Granite and granites of the southern Adelaide Fold Belt.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 1992
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Pluckhahn, D. "The Palmer Granite: geochronology, geochemistry and genesis." Thesis, 1993. http://hdl.handle.net/2440/87543.
Повний текст джерелаАнотація:
This item is only available electronically.Various igneous bodies have intruded the Palmer area throughout the Delamerian Orogeny. The earliest, the Rathjen Gneiss, intruded either before or during D1 which gave it the prominent foliation. D1 was also responsible for crenulations in migmatite veins throughout the area. These crenelated migmatite veins are in areas folded by D2 mesoscale folds. Some pegmatite veins are also folded by D2 folds. The Palmer Granite intruded during D2 as is seen by shearing in a semi-crystalline state and a tectonic foliation that has been folded. The ballooning of the granite during emplacement deforms the surrounding sediments and the pre-granite folds hence their axes lie parallel to the contact of the granite. The effect of the granite intruding during the deformation has lead to the axis of the D2 folds forming after the granite to have a degree of randomness about their axis. Migmatite grade was reached again after the intrusion of the granite causing melt veins to develop to disrupt the foliation. D3 formed a regional syncline of the area combined with some small scale folding within the granite, however a foliation did not form. The emplacement of the granite and some other igneous bodies throughout the area has been controlled by using the bedding plane of the Kanmantoo. The geochemical trends throughout the Palmer Granite is formed by two different groups fractionally crystallising zircon, amphibole and biotite. This results in a decrease of normally incompatible elements. The two groups form by one group from a homogeneous source and the other a heterogeneous source. The xenoliths crystallised from a mafic magma. The amphibolites form two groups according to their differentiation and genetic relationship. They both form by fractional crystallisation however U and Pb are decreasing cannot be explained by this. Another possible mechanism is liquid un-mixing. To tie all of the groups together a model of a mafic pluton that crystallises the xenoliths as a chilled margin. The mafic magma evolves some of the Palmer Granite whilst turbulently convecting hence homogenising the magma. A magma recharge forms the more evolved mafic and this forms more Palmer Granite which convects in a laminar fashion forming heterogeneities. Part of the mafics evolve enough to be caught up in the Palmer Granite and as it does not crystallise zircons all the fractional crystallisation of the Palmer Granite must have occurred in the mafic plution.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 1993
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Franklin, H. D. "Spatial analysis and systematics of discrete extensional structures in the vicinity of the Kanmantoo Cu-Au mineral deposit, South Australia." Thesis, 2009. http://hdl.handle.net/2440/128769.
Повний текст джерелаАнотація:
This item is only available electronically.The Kanmantoo Cu-Au deposit, situated 55 km south-east of Adelaide, is hosted in the Tapanappa Formation of the Kanmantoo Trough. Recent evidence supports an epigenetic mineralising model for the deposit with respect to the Delamerian Orogeny of ~514 to 490 ±3 Ma. The Delamerian deformation event is the oldest portion of the Tasmanides, a 20 000 km orogenic belt along the eastern palaeo-pacific margin of Gondwana. Mineralisation of the Kanmantoo deposit has been linked with post-Delamerian multi-phase extension in east dipping normal faults. The final stages of extension resulted in non-mineralised north dipping normal faults and proximal discrete fracturing. Structural analysis of geology centred on the Kanmantoo deposit has classified a systematic set of extensional fracturing, developed in- the Kanmantoo deposit and in the region surrounding the deposit for >5 km radius. The fracture set trends east-west and dips steeply to the north with a recorded mean orientation of 75/359°. Fractures are characteristically not offset by shearing, strike for tens of metres, have variable frequency, and alterations influenced by fluid migration. Petrographic and geochemical analysis (SEM)in this study has defined a regionally distributed fracture-hosted albitic alteration, which is relatively enriched in Na, Ca, Al and depleted in Fe, Mg and K. A late stage extensional setting is supported for the development of the discrete sub-vertical fracturing.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2009
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Barrett, L. "The structural geology of the Rapid BaySecond Valley area, Fleurieu Peninsula, South Australia." Thesis, 1995. http://hdl.handle.net/2440/128629.
Повний текст джерелаАнотація:
This item is only available electronically.Whilst the geology of the Rapid Bay-Second Valley area is known to be both structurally and stratigraphically complex, previous workers (Daily, 1963; Evans 1987; Drayton, 1963; Campana and Wilson, 1955) have been unable to agree on many aspects of the area. Neoproterozoic and Cambrian aged sediments were first deposited in an extensional basin, which was formed due to lithospheric thinning, and associated subsidence (Jenkins, 1986, 1990). These rocks have then been subjected to at least one phase of deformation, the Cambro-Ordovician Delamerian Orogeny (Offler & Fleming, 1968; Thompson, 1970). Listric extensional faults were formed both before and during sedimentation of the rocks, which has created narrow zones of weakness that the subsequent compressional event has exploited, creating thrust faults (Flottman et al., 1994). Structural mapping of the area has revealed that it is transected by two thrust faults and is intensely folded in places. Structural data has been collected during eight weeks of field work and has been compiled into a 1:10 000-scale geological map which accurately represents the area. A computer-generated three-dimensional model has been created for the area, based on this map, and cross and profile sections constructed from the data collected. The model was constructed using Vulcan™ software. Strain analysis has also been conducted on many of the folds in the area.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 1995
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Kimpton, B. J. "The geological relationship between Kanmantoo Cu-Au deposit mineralisation, hydrothermal metasomatism and igneous intrusives." Thesis, 2018. http://hdl.handle.net/2440/130628.
Повний текст джерелаАнотація:
This item is only available electronically.The Kanmantoo Cu-Au deposit has been in episodic operation since 1846, one decade after the capital city of Adelaide was established some 40 kilometres to the NW. Regionally and within the host stratigraphy there exists archetypal evidence of the Cambrian Delamerian Orogeny through a complex structural, metamorphic and intrusive history. Consequently, numerous theories exist within the literature regarding a syngenetic or epigenetic style of mineralisation and the debated contribution, if any, of magmatic hydrothermal fluids. This study has documented numerous felsic intrusive vein sets within the Kanmantoo Cu-Au deposit which have been utilised to constrain the role of igneous activity on mineralisation within a wider Delamerian context. Monazite U–Pb ages of felsic veins show that intrusion first occurred at syn-peak metamorphic, syn-orogenic conditions (495.11 ± 2.79 Ma), continuing periodically until post-peak metamorphic, extensional conditions (483.43 ± 2.52 Ma). Intrusions are coeval with mineralisation and are temporally and geochemically analogous to magmatic activity in the adjacent Monarto and Murray Bridge provinces. Analysis of trace elements in monazites identifies the Kanmantoo Cu-Au deposit as a syn- to post-peak metamorphic hydrothermal anomaly which, combined with the presence of felsic veins, indicates that mineralisation resulted partly from fluids generated by a pluton at depth. These findings broadly confirm the prospectivity of Delamerian-affected terranes throughout large parts of South Eastern Australia where pervasive intrusive geology exists.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018
Звіти організацій з теми "Delamerian Orogen"
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Bodorkos, S., P. L. Blevin, C. J. Simpson, P. J. Gilmore, R. A. Glen, J. E. Greenfield, R. Hegarty, and C. D. Quinn. New SHRIMP U-Pb zircon ages from the Lachlan, Thomson and Delamerian orogens, New South Wales: July 2009-June 2010. Geoscience Australia and Geological Survey of new South Wales, 2013. http://dx.doi.org/10.11636/record.2013.029.
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