Coupled garnet Lu–Hf and monazite U–Pb geochronology constrain early convergent margin dynamics in the Ross orogen, Antarctica

Hagen‐Peter, Graham; Cottle, John M.; Smit, Matthijs; Cooper, Alan F.

doi:10.1111/jmg.12182

Cited by 38 publications

(17 citation statements)

References 79 publications

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“…To investigate whether Lu zonation significantly affected bulk-grain Lu-Hf age results, models of Lu distribution in garnet were constructed. These models used measured Lu transects (Figure 4), averaging adjacent analyses to calculate the Lu abundance within a concentric shell between the two points, and assuming spherical garnet geometry, concentric compositional zoning, and either constant volumetric or constant radial growth rates (Hagen-Peter, Cottle, Smit, & Cooper, 2016;Kellett, Cottle, & Smit, 2014;Lapen et al, 2003;Smit, Ratschbacher, Kooijman, & Stearns, 2014;Smit, Scherer, Br€ ocker, & van Roermund, 2010). Figure 6 plots cumulative Lu v. either the core-rim volume percentage or core-rim radius percentage of the garnet grain for a representative garnet from each sample.…”

Section: Lu-hf Garnet Geochronologymentioning

confidence: 99%

Record of plate boundary metamorphism during Gondwana breakup from Lu–Hf garnet geochronology of the Alpine Schist, New Zealand

Briggs

Cottle

Smit

2018

Journal Metamorphic Geology

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The Zealandia portion of the Pacific–Gondwana margin underwent widespread extension, fragmentation, separation and subsidence during the final stages in the breakup of Gondwana. Although these processes shaped the geology of New Zealand, their timing and the timing of subduction cessation in the region remain unclear. To investigate the timing of these processes, we used Lu–Hf garnet geochronology to date six samples of the Alpine Schist, which represents the metamorphic section of the former Zealandia margin. The garnet dates range from 97.3 ± 0.3 to 75.4 ± 1.3 Ma. Compositional zoning in garnet indicates that the spread in ages results from diachronous metamorphism in the upper plate at the Pacific–Gondwana margin, occurring concurrently with rifting of Zealandia from East Gondwana via opening of the Tasman Sea. Clear spatial trends in the timing of garnet growth throughout the Alpine Schist are absent, indicating that either regional age trends were offset by post‐metamorphic deformation, or that metamorphism did not result from a single regional heat source, and was instead driven by short‐duration, spatially dispersed processes such as episodic fluid‐fluxing or mechanical heating. Diachronous metamorphism of the Alpine Schist can be attributed to heat conduction from the rising upper mantle during widespread extension, progressive burial and heating of accretionary wedge sediments during ongoing horizontal shortening, or fluid‐fluxing sourced from a subducting and dehydrating Hikurangi Plateau. These results indicate that during separation of Zealandia from East Gondwana in the late Cretaceous, the crust at the Pacific–Gondwana margin remained hot, potentially facilitating the extensive thinning of the Zealandia lithosphere during this time.

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Section: Lu-hf Garnet Geochronologymentioning

confidence: 99%

Record of plate boundary metamorphism during Gondwana breakup from Lu–Hf garnet geochronology of the Alpine Schist, New Zealand

Briggs

Cottle

Smit

2018

Journal Metamorphic Geology

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“…To test if monazite and garnet grew in equilibrium, we have calculated the apparent monazite/garnet REE distribution coefficients for sample BC43 and compared the results against previously published reference values (Hermann & Rubatto, 2003; Rubatto et al., 2006; Warren et al., 2018). Recent studies have urged for caution when using monazite–garnet partition coefficients from natural samples as evidence of growth in equilibrium (Hagen‐Peter et al., 2016; Warren et al., 2018), and there is evidence to suggest that REE partitioning between monazite and garnet is temperature‐dependent (Warren et al., 2018). However, partitioning values do not appear to differ greatly between sub‐ and supra‐solidus metapelites (Hermann & Rubatto, 2003; Rubatto et al., 2006; Warren et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Tectono‐Metamorphic Evolution of the Northern Dom Feliciano Belt Foreland, Santa Catarina, Brazil: Implications for Models of Subduction‐Driven Orogenesis

et al. 2022

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Orogenic systems vary widely in terms of their geometry, duration, and scale. The classic collisional orogen can be described using models that involve the termination of a Wilson cycle, where the opening and closing of a large ocean basin between continental bodies culminates in the continental collision. Accretionary orogens, in contrast, form at continental-oceanic convergent plate boundaries in the absence of continental collision, and develop during continuous subduction by crustal thickening due to short-term coupling across the subduction plate boundary (Cawood et al., 2009). Within-plate deformation can also occur away from plate margins, triggered by the transmission of stress from active plate boundaries through the lithosphere (Aitken et al., 2013;Raimondo et al., 2014). Large-scale intracontinental orogens are comparatively less common than collisional or accretionary orogens, but examples are recognized in both ancient and modern settings (Cunningham, 2005;Faure et al., 2009;Hand & Sandiford, 1999). Although the defining characteristics of collisional, accretionary, and intracontinental orogens make them distinct, Cawood et al. (2009) proposed that they represent three interrelated endmembers between which lies a wide spectrum of orogen types. Thus, continental collision at the termination of a Wilson cycle is genetically linked to preceding accretionary orogeny. Similarly, tectonic switching during accretionary orogeny can produce large-scale crustal thickening in within-plate settings (Lister & Forster, 2009), resulting in orogens that develop as the consequence of intracratonic rift inversion, similar to what occurs within an accretionary back-arc setting but at a distance from the developing arc (Collins, 2002;Thompson et al., 2001).The South Atlantic Neoproterozoic Orogenic System (SANOS, sensu Konopásek et al., 2020) comprises an extensive system of orogenic belts that formed during the late Neoproterozoic amalgamation of Western Gondwana

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“…Volcanic rocks of the Rocky Cape Group and equivalents formed between ~582-575 Ma (149), which we associate with back-arc rifting and consequently we cut passive margin sedimentation off earlier in this segment at 600 Ma. In the Ross Orogen of Antarctica, an active arc was established by 565 Ma (150). In Australia, the Delamerian orogeny formed from 520-490 Ma due to accretion of an outboard arc (147), with peak metamorphism in Tasmania between 520 and 508 Ma (151).…”

Section: Tasmanmentioning

confidence: 99%

Hemispheric geochemical dichotomy of the mantle is a legacy of austral supercontinent assembly and deep subduction of continental crust

Jackson¹,

Macdonald²

2021

Preprint

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Oceanic hotspots with extreme enriched mantle radiogenic isotopic signatures—including high 87Sr/86Sr and low 143Nd/144Nd indicative of ancient subduction of continental crust—are restricted to the southern hemispheric mantle. However, the mechanisms responsible for concentrating subducted continental crust in the austral mantle are unknown. We show subduction of sediments and subduction eroded material, and lower continental crust delamination, cannot generate this spatially coherent austral domain. However, late Neoproterozoic to Paleozoic continental collisions—associated with the assembly of Gondwana and Pangea—were positioned predominantly in the southern hemisphere during the late Neoproterozoic appearance of widespread continental ultra-high-pressure (UHP, >2.7 gigapascals) metamorphic terranes, which marked the onset of deep subduction of upper continental crust. We propose that deep subduction of upper continental crust at ancient rifted-passive margins during austral supercontinent assembly, from 650-300 Ma, resulted in enhanced upper continental crust delivery into the southern hemisphere mantle. In contrast, EM domains are absent in boreal hotspots, for two reasons. First, continental crust subducted after 300—when the continents drifted into the northern hemisphere—has had insufficient time to return to the surface in plumes feeding northern hemisphere hotspots. Second, before the appearance of continental UHP rocks at 650 Ma, upper continental crust was not subducted to great depths, thus precluding its subduction into the northern hemisphere mantle during the Precambrian when continents may have been located in the northern hemisphere. Our model implies a recent formation of the austral EM domain, explains the geochemical dichotomy between austral and boreal hotspots, and may explain why austral hotspots outnumber boreal hotspots.

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Coupled garnet Lu–Hf and monazite U–Pb geochronology constrain early convergent margin dynamics in the Ross orogen, Antarctica

Cited by 38 publications

References 79 publications

Record of plate boundary metamorphism during Gondwana breakup from Lu–Hf garnet geochronology of the Alpine Schist, New Zealand

Record of plate boundary metamorphism during Gondwana breakup from Lu–Hf garnet geochronology of the Alpine Schist, New Zealand

Tectono‐Metamorphic Evolution of the Northern Dom Feliciano Belt Foreland, Santa Catarina, Brazil: Implications for Models of Subduction‐Driven Orogenesis

Hemispheric geochemical dichotomy of the mantle is a legacy of austral supercontinent assembly and deep subduction of continental crust

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