Source of the Lachlan fold belt flysch linked to convective removal of the lithospheric mantle and rapid exhumation of the Delamerian-Ross fold belt

Turner, Simon; Kelley, Simon P.; Vandenberg, A.H.M.; Foden, John; Sandiford, Mike; Flöttmann, Thomas

doi:10.1130/0091-7613(1996)024<0941:sotlfb>2.3.co;2

Cited by 96 publications

(74 citation statements)

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“…Earlier ideas on the Cambrian-Ordovician paleogeography of southeastern Australia regarded the Delamerian Orogeny as a major episode of shortening, which thickened crust of the Delamerian Fold Belt and thereby provided a repeatedly-recycled source for deposition of the widespread siliciclastic turbidite fan (Turner et al, 1996;Fergusson and Tye, 1999). Various plate tectonic scenarios have been given for the Delamerian Orogeny including an island arc -passive margin collision as exemplified by the geology of western Tasmania (Berry and Crawford, 1988;Meffre et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…Sandstone samples from the southern Bendigo Zone and the central part of the Tabberabbera Zone have detrital muscovite ages in the range 512-480 Ma (Turner et al, 1996). From sandstones in the Stawell and Bendigo zones, Foster et al (1998) showed muscovite ages range 580-470 Ma with most ages in the interval 510-500 Ma.…”

Section: Potential Sources Of the Ordovician Turbidites?mentioning

confidence: 98%

“…The source of the Ordovician turbidites is clearly continental, as indicated by the quartz-rich nature of sandstones in the succession. Some authors infer derivation of the sandstones from the Delamerian mountain chain (Turner et al, 1996;Fergusson and Tye, 1999), whilst others argue for a more distant source in the East African Orogen at the junction of West and East Gondwana ( Fig. 1) (the Gondwana Supermountain of Squire et al, 2006;Williams and Pulford, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Evolution of a Cambrian active continental margin: The Delamerian–Lachlan connection in southeastern Australia from a zircon perspective

et al. 2013

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Section: Discussionmentioning

confidence: 99%

Section: Potential Sources Of the Ordovician Turbidites?mentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Evolution of a Cambrian active continental margin: The Delamerian–Lachlan connection in southeastern Australia from a zircon perspective

et al. 2013

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“…Petrographic data from sandstones have been widely used in determining provenance along with other tools such as palaeocurrent indicators, geochemistry, isotope geochemistry and geochronology, particularly detrital zircon age data but also including Ar/Ar ages of detrital micas and amphibole (Dickinson and Suczek, 1979;McLennan et al, 1993;Weltje and von Eynatten, 2004). Many of these types of analyses have been used to determine the provenance of the major Ordovician turbidite fan in the Lachlan Orogen of southeastern Australia (Turner et al, 1996;Fergusson and Tye, 1999;Fergusson et al, 2013) (Figs. 1, 2).…”

Section: Introductionmentioning

confidence: 99%

Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

Offler

Fergusson

2016

Sedimentary Geology

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The Early Palaeozoic proto-Pacific Pacific margin of Gondwana was characterised by a huge turbidite submarine fan with abundant clastic detritus derived from unknown sources within Gondwana. These deposits are widespread in the Lachlan Orogen of southeast Australia and include the Ordovician Adaminaby Group. Here we show that the mudstones and sandstones of the Adaminaby Group have chemical compositions that indicate the detritus in them was derived from a felsic, continental source similar in composition to Post Archean Australian Shales (PAAS). Chondrite normalised REE patterns showing LREE enrichment, flat PAAS normalised patterns and elemental ratios La/Sc, Cr/Th, Cr/V, Th/Sc and Th/U, have been used to support this interpretation. The dominance of quartz, and to a lesser degree plagioclase and biotite in the sandstones, suggests that the source was mainly granodioritic to tonalitic in composition. Th/Yb and Ta/Yb ratios indicate that the source was probably calc-alkaline, continental and shoshonitic. In addition, the presence of detrital muscovite, low-grade metamorphic and felsic volcanic clasts, demonstrates that a lowgrade metamorphic terrane and volcanic arc contributed to the detritus observed in the samples. The presence of well-rounded zircons and tourmalines, very high Zr contents, high Zr/Sc and higher Cr/V ratios in some samples particularly in the Shoalhaven River area, indicate that some of the detritus was recycled.SiO2 versus (Al2O3 + K2O + Na2O) plots suggest the source areas experienced conditions varying from humid/semihumid to semi-arid. Textural features and weathering trends of samples from all locations follow a curved pathway on Al2O3 -(CaO* + Na2O) -K2O (ACNK) diagrams, and indicate that the clays formed from weathering had been K-metasomatised prior to penetrative deformation. Chemical indices of alteration (CIA) reveal that even the freshest sandstones are altered and others are moderately to strongly altered. Discrimination diagrams involving major, trace and REE strongly support a collisional/continental volcanic arc setting that was substantially eroded to produce the plutonic detritus observed in the sandstones. The collisional setting accords with that proposed previously by other authors who suggested that it developed during the Delamerian Orogeny, resulting in the uplifted source areas providing detritus that inundated the backarc and forearc sites of the Macquarie Arc. Some of the detritus, however, may have been derived from a continental arc that existed in the late Cambrian along the margin of the Ross Orogen. Based on palaeocurrent analyses in previous studies and shoshonitic signature of the detritus, it is proposed that the Cambrian volcanics along the eastern active margin of Gondwana provided much of the detritus in the Adaminaby Group. Zircons with the Grenvillian signature suggest that some detritus were also derived from the Ross Orogen. Discrimination diagrams involving major, trace and REE strongly support a collisional/continental volcanic arc setting...

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“…The early stages of the event were synchronous with granitic magmatism throughout the region, with the earliest syntectonic granite intruded during the onset of orogenic crustal shortening at 514 ± 4 Ma [31]. Increasingly mantle-derived magmatism marked the end of the orogenic event (c. 490 Ma) and continued into the Early Ordovician [32][33][34]. Following the Delamerian Orogeny, an extensional setting was re-established and post-orogenic magmatism resulted in the intrusion of rhyolite and diorite dikes [27].…”

Section: Geological Settingmentioning

confidence: 93%

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

et al. 2017

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Phase equilibria modelling incorporating melt reintegration offers a methodology to create hypothetical rock compositions that may have existed prior to melt loss, allowing the potential prograde evolution of rocks to be explored. However, melt reintegration modelling relies on assumptions concerning the volume of melt that was lost and is generally restricted by the absence of direct constraints on the pre-anatectic mineral assemblages. Mg-rich granulite in the 514-490 Ma Delamerian Orogen in southern Australia contains spinel-cordierite symplectic intergrowths that surround rare, coarse blocky domains of sillimanite. These sillimanite cores, as well as the widespread presence of andalusite in lower grade areas of the southern Delamerian Orogen, suggest that the subsolidus precursor to the granulite contained andalusite. This provides the opportunity to test if melt reintegration modelling of the granulite predicts subsolidus andalusite.Stepwise down-temperature melt reintegration modelling produces a water-saturated solidus after the addition of 12 mol% melt. When modelled at subsolidus conditions, the resulting rock composition produces andalusite-bearing assemblages with andalusite modes similar to the abundance of the sillimanite-cored spinel-cordierite intergrowths. The modelling results from this case study suggest that melt reintegration modelling is a valid method to recreate prograde subsolidus bulk rock compositions.

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Source of the Lachlan fold belt flysch linked to convective removal of the lithospheric mantle and rapid exhumation of the Delamerian-Ross fold belt

Cited by 96 publications

References 0 publications

Evolution of a Cambrian active continental margin: The Delamerian–Lachlan connection in southeastern Australia from a zircon perspective

Evolution of a Cambrian active continental margin: The Delamerian–Lachlan connection in southeastern Australia from a zircon perspective

Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

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