A New Reconstruction for Permian East Gondwana Based on Zircon Data From Ophiolite of the East Australian Great Serpentinite Belt

Milan, Luke; Белоусова, Е. А.; Glen, R. A.; Chapman, Timothy; Kalmbach, John H.; Fu, Bin; Ashley, P. M.

doi:10.1029/2020gl090293

Cited by 7 publications

(11 citation statements)

References 83 publications

(149 reference statements)

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“…In contrast, Milan et al. (2021) have recently found that the age of plagiogranite dykes, intruded into a relatively coherent block of gabbro (18 km 2 ), is Early Permian (∼280 Ma). The conclusion by Milan et al.…”

Section: Discussionmentioning

confidence: 90%

“…However, Milan et al. (2021) have recently suggested that the age of this ocean is much younger than previously thought, based on the age of plagiogranite dykes (∼280 Ma) intruded into a larger (∼18 km 2 ) block of ophiolite.…”

Section: Geological Settingmentioning

confidence: 88%

“…All these studies, except Milan et al. (2021), have shown that dismembered ophiolitic blocks, ranging in scale from meters to tens of meters, are Cambrian in age (535–500 Ma). In contrast, Milan et al.…”

Section: Discussionmentioning

confidence: 99%

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Origin of the Intra‐Oceanic Silverwood Block (New England Orogen, Australia): Evidence From Radiolarian Biostratigraphy and Detrital Zircon Petrochronology

et al. 2021

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Cambrian to Triassic subduction processes in eastern Australia produced a complex and highly contorted assembly of supra‐subduction units. However, regardless of the long history of oceanic subduction, relatively little evidence exists on oceanic terranes whose accretion onto the continental margin may have accompanied subduction processes. We present new radiolarian and petrochronological data from Devonian and Carboniferous rocks exposed in the middle of a tight orocline. Based on radiolarian biostratigraphy and U‐Pb dating of detrital zircon grains, we show that volcaniclastic rocks from the Silverwood Group and Alice Creek beds were deposited during the Late Devonian, which is later than previously thought. Trace‐element compositions of the Devonian zircons are characteristic of crystallization of magmas in an oceanic environment, thus supporting previous suggestions that the Silverwood Group was derived from an intra‐oceanic arc system. Carboniferous zircons from a nearby forearc basin unit (Mount Barney beds) exhibit a continental affinity, indicating that accretion of the Silverwood Block likely occurred before the establishment of this continental arc. A serpentinite belt that occurs adjacent to the Silverwood Block might represent a remnant ophiolitic suture of the now‐consumed oceanic domain, which once separated the Silverwood Block from the eastern Gondwanan margin. Based on the assumption that such an intervening ocean existed, we discuss alternative scenarios for the origin and accretion of the Silverwood Block. The most likely scenario involves intra‐oceanic magmatism in a marginal oceanic basin whose development was driven by trench retreat, and a subsequent accretion in response to trench advance and/or slab flattening.

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Section: Discussionmentioning

confidence: 90%

Section: Geological Settingmentioning

confidence: 88%

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Origin of the Intra‐Oceanic Silverwood Block (New England Orogen, Australia): Evidence From Radiolarian Biostratigraphy and Detrital Zircon Petrochronology

et al. 2021

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“…Two major are-up cycles are identi ed along the arc at c. 290-280 Ma (30 km 3 /my per km) and c. 260-245 Ma (63 km 3 /my per km) that punctuate the background low-volume magmatism along the margin (5-10 km 3 /my per km: Fig. 3) 21 . The c. 290-280 Ma peak is related to back-arc extension and crustal reworking 22 .…”

Section: Eastern Australia Permian Are-upmentioning

confidence: 99%

Arc eruptions deliver ‘first blow’ in the pulsed end-Permian mass extinction

Chapman¹,

Milan²,

Metcalfe³

et al. 2021

Preprint

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Brief pulses of intense magmatic activity (flare-ups) along convergent margins represent drivers for climatic excursions that can lead to major extinction events. However, correlating volcanic outpouring to environmental crises in the geological past is often difficult due to poor preservation of volcanic sequences. Herein, we present a high-fidelity, CA-TIMS U–Pb zircon record of an end-Permian flare-up event in Eastern Australia, that involved the eruption of >39,000–150,000 km3 of silicic magma in c. 4.21 million years. A correlated high-resolution tephra record (c. 260–249 Ma) in the proximal sedimentary basins suggests recurrence of eruptions from the volcanic field in intervals of ~51,000–145,000 years. Peak eruption activity at 253 Ma is chronologically associated with the pulsed stages of the Permian mass extinction event. The ferocity of the 253 Ma eruption cycle in Eastern Australia is identified as a driver of greenhouse crises and ecosystem stress that led to the reduction in diversity of genera and the demise of the Glossopteris Forests. Simultaneous global continental margin arc flare-up events could thus present an additional agent to trigger greenhouse warming and ecosystem stress that preceded the catastrophic eruption of the Siberian Traps.

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“…Crystallisation of parts of the GSB has been constrained to the early Cambrian based on a U-Pb age of zircon in plagiogranite associated to the serpentinite sequence (530 ± 6 Ma; Aitchison and Ireland, 1995) but more recent zircon dating of serpentinite north of Woodsreef suggest formation ages of ~283-277 Ma (Milan et al, 2020). The GSB was emplaced along the Peel-Manning Fault during the early Permian, as indicated by thermal alteration by the Bundarra Plutonic Suite (267.2 ± 1.4 Ma; Cawood et al, 2011) and serpentinite interleaving with the Sakmarian Kensington Formation (Vickery et al, 2010).…”

Section: Great Serpentinite Beltmentioning

confidence: 99%

Mineralisation of atmospheric CO2 in hydromagnesite in ultramafic mine tailings – Insights from Mg isotopes

Oskierski

Turvey

Wilson

et al. 2021

Geochimica et Cosmochimica Acta

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In this study we present the first Mg isotope data that record the fate of Mg during mineralisation of atmospheric CO2 in ultramafic mine tailings. At the Woodsreef Asbestos Mine, New South Wales, Australia, weathering of ultramafic mine waste sequesters significant amounts of CO2 in hydromagnesite [Mg5(CO3)4(OH)2•4H2O]. Mineralisation of CO2 in above-ground, sub-aerially stored tailings is driven by the infiltration of rainwater dissolving Mg from bedrock minerals present in the tailings. Hydromagnesite, forming on the surface of the tailings, has lower δ 26 Mg (δ 26 MgHmgs = -1.48 ± 0.02 ‰) than the serpentinised harzburgite bedrock (δ 26 MgSerpentinite = -0.10 ± 0.06 ‰), the bulk tailings (δ 26 MgBulk tailings = -0.29 ± 0.03 ‰) and weathered tailings containing authigenic clay minerals (δ 26 MgWeathered tailings = +0.28 ± 0.06 ‰). Dripwater (δ 26 MgDripwater = -1.79 ± 0.02 ‰) and co-existing hydromagnesite (δ 26 MgHmgs = -2.01 ± 0.09 ‰), forming in a tunnel within the tailings, and nodular bedrock magnesite [MgCO3] (δ 26 MgMgs = -3.26 ± 0.10 ‰) have lower δ 26 Mg than surficial fluid (δ 26 Mg = -0.36 ‰) and hydromagnesite. Complete dissolution of source minerals, or formation of Mg-poor products during weathering, is expected to transfer Mg into solution without significant alteration of the Mg isotopic composition. Aqueous geochemical data and modelling of saturation indices, along with Rayleigh distillation and mixing calculations, indicate that the 26 Mg-depletion in the drip water, relative to surficial water, is the result of brucite dissolution and/or precipitation of secondary Mg-bearing silicates and cannot be assigned to bedrock magnesite dissolution. Our results show that the main mineral sources of Mg in the tailings (silicate, oxide/hydroxide and carbonate minerals) are isotopically distinct and that the Mg isotopic composition of fluids and thus of the precipitating hydromagnesite reflects both isotopic composition of source minerals and precipitation of Mg-rich secondary phases. The consistent enrichment and depletion of 26 Mg in secondary silicates and carbonates, respectively, underpins the use of the presented hydromagnesite and fluid Mg isotopic compositions as a tracer of Mg sources and pathways during CO2 mineralisation in ultramafic rocks.

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A New Reconstruction for Permian East Gondwana Based on Zircon Data From Ophiolite of the East Australian Great Serpentinite Belt

Cited by 7 publications

References 83 publications

Origin of the Intra‐Oceanic Silverwood Block (New England Orogen, Australia): Evidence From Radiolarian Biostratigraphy and Detrital Zircon Petrochronology

Origin of the Intra‐Oceanic Silverwood Block (New England Orogen, Australia): Evidence From Radiolarian Biostratigraphy and Detrital Zircon Petrochronology

Arc eruptions deliver ‘first blow’ in the pulsed end-Permian mass extinction

Mineralisation of atmospheric CO2 in hydromagnesite in ultramafic mine tailings – Insights from Mg isotopes

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