Hafnium isotope homogenization during metamorphic zircon growth in amphibolite-facies rocks: Examples from the Shackleton Range (Antarctica)

Zeh, Armin; Gerdes, Axel; Will, Thomas M.; Frimmel, Hartwig E.

doi:10.1016/j.gca.2010.05.016

Cited by 77 publications

(24 citation statements)

References 64 publications

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“…Although metamorphic zircon growth has been shown to occur under amphibolite facies conditions (45), cathodoluminescence imaging shows no evidence of metamorphic overgrowths in these zircons. Instead, they are euhedral, prismatic, and have distinct, fine, oscillatory zoning, a feature that is characteristic and unique to magmatic zircons (46) (Fig.…”

Section: Age and Geochemistry Of The Palawan Ophiolite And Its Solementioning

confidence: 92%

Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology

Keenan

Encarnación

Buchwaldt

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Where and how subduction zones initiate is a fundamental tectonic problem, yet there are few well-constrained geologic tests that address the tectonic settings and dynamics of the process. Numerical modeling has shown that oceanic spreading centers are some of the weakest parts of the plate tectonic system [Gurnis M, Hall C, Lavier L (2004) Geochem Geophys Geosys 5:Q07001], but previous studies have not favored them for subduction initiation because of the positive buoyancy of young lithosphere. Instead, other weak zones, such as fracture zones, have been invoked. Because these models differ in terms of the ages of crust that are juxtaposed at the site of subduction initiation, they can be tested by dating the protoliths of metamorphosed oceanic crust that is formed by underthrusting at the beginning of subduction and comparing that age with the age of the overlying lithosphere and the timing of subduction initiation itself. In the western Philippines, we find that oceanic crust was less than ∼1 My old when it was underthrust and metamorphosed at the onset of subduction in Palawan, Philippines, implying forced subduction initiation at a spreading center. This result shows that young and positively buoyant, but weak, lithosphere was the preferred site for subduction nucleation despite the proximity of other potential weak zones with older, denser lithosphere and that plate motion rapidly changed from divergence to convergence. subduction initiation | tectonics | geochronology | Philippines | ophiolite

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Section: Age and Geochemistry Of The Palawan Ophiolite And Its Solementioning

confidence: 92%

Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology

Keenan

Encarnación

Buchwaldt

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…However, in situ modified metamorphic zircon grains will not lose its isotopic composition with regard to Hf (Zeh et al, 2010). This contrasts with zircon grains that have been dissolved and re-precipitated from a fluid or melt (Gerdes and Zeh, 2009;Zeh et al, 2010). In short, zircon grains can lose Pb while retaining its Hf isotope composition during solid-state recrystallization, which would be represented by the Pb-loss trend in figure 5.…”

Section: Hf Constrains On Subsurface Evolution Of Ohiomentioning

confidence: 99%

“…Recent studies, by Zeh et al (2010) suggest that zircon can lose Pb through various processes under metamorphic conditions. These processes lead to zircon domains with different appearance and generally lower U-Pb ages and Th/U ratios than their unmetamorphosed igneous counterparts (Harley et al, 2007).…”

Section: Hf Constrains On Subsurface Evolution Of Ohiomentioning

confidence: 99%

“…These processes lead to zircon domains with different appearance and generally lower U-Pb ages and Th/U ratios than their unmetamorphosed igneous counterparts (Harley et al, 2007). However, in situ modified metamorphic zircon grains will not lose its isotopic composition with regard to Hf (Zeh et al, 2010). This contrasts with zircon grains that have been dissolved and re-precipitated from a fluid or melt (Gerdes and Zeh, 2009;Zeh et al, 2010).…”

Section: Hf Constrains On Subsurface Evolution Of Ohiomentioning

confidence: 99%

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Zircon U-Pb, Hf and O isotope constraints on growth versus reworking of continental crust in the subsurface Grenville orogen, Ohio, USA

Petersson

Scherstén

Andersson

et al. 2015

Precambrian Research

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“…In addition, combined U-Pb dating and Hf isotope analyses of zircon can provide key information regarding the source of the magma from which zircon crystallized as well as on the timing of crustal formation and reworking (Condie et al, 2011;Kemp et al, 2006). Moreover, combined U-Pb dating and Hf isotope tracing has proven efficient in retrieving reliable chrono-petrological information even from complexly zoned zircons grains formed and/or altered during multiple metamorphic, magmatic, and/or sedimentary processes (e.g., Gerdes and Zeh, 2009;Kemp et al, 2006;2009;Zeh et al, 2010aZeh et al, , 2010b. As a result, zircon is the perfect tool to investigate crustal evolution in the eastern Massif Central (EMC; Fig.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Pre-Cadomian to late-Variscan odyssey of the eastern Massif Central, France: Formation of the West European crust in a nutshell

Chelle-Michou¹

2017

Preprint

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The East Massif Central (EMC), France, is part of the internal zone of the Variscan belt where late Carboniferous crustal melting and orogenic collapse have largely obliterated the pre-to early-Variscan geological record. Nevertheless, parts of this history can be reconstructed by using in-situ U-Th-Pb-Lu-Hf isotopic data of texturally well-defined zircon grains from different lithological units. All the main rock units commonly described in the EMC are present in the area of Tournon and include meta-sedimentary and meta-igneous rocks of the Upper Gneiss Unit (UGU) and of the Lower Gneiss Unit (LGU), as well as cross-cuttingVariscan granitoid dikes and a heterogeneous granite coring the major Velay dome. Herein we demonstrate that the UGU and the LGU have markedly distinct zircon records. The results of this study are consistent with deposition of the protoliths of the paragneisses within a backarc basin that was located adjacent to the Arabian-Nubian shield and/or the Saharan Metacraton during the late Ediacaran and collected detritus from the Gondwana continent. At ~545 Ma some of these sedimentary rocks were affected by a first melting event that formed the protoliths of the LGU orthogneisses, those of which subsequently remelted at ca. 308 Ma to form the Velay granite-migmatite dome. Protoliths of the UGU result mainly from a bimodal rift-related magmatism at ~480 Ma, corresponding to melting of the Ediacaran sediments and depleted mantle. Zircon rims from the UGU additionally provide evidence for a metamorphic/migmatitic overprint during the Lower Carboniferous (~350-340 Ma).Finally, several generations of granite dikes of which inherited zircons display characteristics of both the UGU and the LGU were protractedly emplaced from ~322 Ma to ~308 Ma, the youngest of which being coeval with the formation of the Velay dome. Our data further show that the vast majority of crustal material ultimately involved in the Variscan orogeny, which forms the present-day basement in the EMC, was derived from a sedimentary mixture of ACCEPTED MANUSCRIPTA C C E P T E D M A N U S C R I P T various components from the Gondwana continent deposited in Ediacaran times, with no evidence for the involvement of an older autochthonous crust.

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Hafnium isotope homogenization during metamorphic zircon growth in amphibolite-facies rocks: Examples from the Shackleton Range (Antarctica)

Cited by 77 publications

References 64 publications

Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology

Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology

Zircon U-Pb, Hf and O isotope constraints on growth versus reworking of continental crust in the subsurface Grenville orogen, Ohio, USA

Pre-Cadomian to late-Variscan odyssey of the eastern Massif Central, France: Formation of the West European crust in a nutshell

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