Tectonic development of the Samail ophiolite: High‐precision U‐Pb zircon geochronology and Sm‐Nd isotopic constraints on crustal growth and emplacement

Rioux, Matthew; Bowring, Samuel A.; Kelemen, P. B.; Gordon, Stacia M.; Miller, Robert B.; Dudás, Francis Ő.

doi:10.1002/jgrb.50139

Cited by 158 publications

(273 citation statements)

References 103 publications

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“…The age of the youngest zircon, 35.25 ± 0.15 Ma, is taken as the best estimate of the final crystallization age of the protolith of this sample. The small spread in ages seen in this sample is similar to those revealed by high precision U-Pb geochronology in the Samail ophiolite (44) and may be due to prolonged zircon crystallization in a replenished magma chamber or assimilation of slightly older wall rock.…”

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

confidence: 74%

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 Solesupporting

confidence: 74%

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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“…The high-grade metamorphism of the metamorphic sole can occur only at the inception of subduction because the hanging wall would subsequently be too cold to cause high-grade metamorphism (Wakabayashi and Dilek, 2003). Temporal and spatial relations of ophiolites and metamorphic soles have been well-documented in the Oman ophiolite by high-precision U-Pb zircon geochronology and whole rock Nd-isotopic data (Rioux et al, 2013;Warren et al, 2005). Warren et al (2005) reported coeval U-Pb zircon ages for trondhjemites (95.3±0.2 Ma) and for amphibolites (94.48±0.23 Ma), and suggested an SSZ origin for the Semail ophiolite.…”

Section: Discussionmentioning

confidence: 99%

“…Warren et al (2005) reported coeval U-Pb zircon ages for trondhjemites (95.3±0.2 Ma) and for amphibolites (94.48±0.23 Ma), and suggested an SSZ origin for the Semail ophiolite. However, Rioux et al (2013) provided more detailed U-Pb zircon ages and whole rock Nd isotopic data for the crustal rocks and the underlying metamorphic sole and concluded that most of the ophiolitic crust formed at an oceanic spreading center in <1 Ma in the Late Cretaceous, followed by subduction or thrusting that was established below the ophiolite after ≤0.25-0.5 Ma. Both mid-ocean ridge (MOR) and suprasubduction zone (SSZ) models have been proposed for the genesis of the Oman ophiolite (Rioux et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…However, Rioux et al (2013) provided more detailed U-Pb zircon ages and whole rock Nd isotopic data for the crustal rocks and the underlying metamorphic sole and concluded that most of the ophiolitic crust formed at an oceanic spreading center in <1 Ma in the Late Cretaceous, followed by subduction or thrusting that was established below the ophiolite after ≤0.25-0.5 Ma. Both mid-ocean ridge (MOR) and suprasubduction zone (SSZ) models have been proposed for the genesis of the Oman ophiolite (Rioux et al, 2013). MOR-and SSZ-type mantle residues have been reported from mantle tectonites of the Tauride ophiolites, suggesting a low-degree of partial melting in a mid-ocean ridge environment during the opening stage of the Neotethyan oceanic basins followed by re-melting and depletion in a suprasubduction zone (SSZ) setting (Saka et al, 2014;Uysal et al, 2012;Caran et al, 2010;Aldanmaz et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Different cooling histories of the metamorphic soles and oceanic crustal rocks, as well as different blocking temperatures of zircon U-Pb (~900 o C) and hornblende 40 Ar/ 39 Ar (~550 o C) systems, do not permit compilation of a coherent geochronological record (Hacker and Gnos, 1997;Spray, 1984). Therefore, more high-precision U-Pb geochronological studies on zircons in both magmatic and metamorphic rocks of the Tauride belt ophiolites should be applied to better constrain the temporal relations of the oceanic lithosphere and the metamorphic soles, as has been done in the Oman ophiolite (Rioux et al, 2013;Warren et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

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The tauride ophiolites of Anatolia (Turkey): A review

Parlak¹

2016

J. Earth Sci.

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The Tauride ophiolites lie on the northern and southern flanks of an E-W-trending Tauride carbonate platform. They mainly consist of three tectonic units namely in ascending order, ophiolitic mélange, sub-ophiolitic metamorphic sole and oceanic lithospheric remnants. They were generated above intra-oceanic subduction zones and emplaced over the Tauride carbonate platform from different Neotethyan oceanic basins in the Late Cretaceous. Tauride ophiolites from west to east are described and reviewed. All are underlain by well-preserved dynamothermal metamorphic soles of varied structural thicknesses up to 500 m that have a constant structural position between ophiolitic mélange below and harzburgitic mantle tectonites above and display typical inverted metamorphic sequences from amphibolite facies above to greenschist facies below. The metamorphic soles are shown to have evolved during the initiation of subduction and emplacement processes. In the Pozantı-Karsantı area the contact between the metamorphic sole and the overlying serpentinized harzburgites is characterized by a 1.5-2-m-thick zone of sheared serpentinized harzburgitic mantle intercalated with amphibolites and cut by thick mafic dykes (7-8 m) which postdate intraoceanic metamorphism and high-temperature ductile deformation. This contact is interpreted as an intra-oceanic decoupling surface along which volcanics from the upper levels of the down-going plate were metamorphosed to amphibolite facies and accreted to the base of the hanging wall plate. The metamorphic soles and overlying ophiolitic rocks were intruded by numerous isolated post-metamorphic diabase dykes filled by island arc tholeiitic magma. Subduction initiation and roll-back processes best explain the structural and petrological relationships of Late Cretaceous ophiolite genesis, metamorphic sole formation and subsequent dyke emplacement of the Tauride ophiolites. KEY WORDS: ophiolite, metamorphic sole, dyke emplacement, roll-back, subduction initiation. INTRODUCTIONThe Tauride orogenic belts of Turkey are interpreted as representing a continental fragment that rifted from Gondwana (North Africa) during the Triassic, followed by reamalgamation and continental collision during the OligoMiocene (Karaoğlan et al., 2016) or Miocene (Okay et al., 2010). The Taurides are traditionally divided into three contiguous parts; the western, central and eastern Taurides (Özgül, 1976).Ophiolites along the Tauride belt start with the Lycian nappes to the west and end with the Divriği ophiolite to the east (Fig. 1). These ophiolites (the Lycian nappes, Antalya, Beyşehir-Hoyran nappes, Mersin, Alihoca, Pozantı-Karsantı, Pınarbaşı and Divriği) are situated either on the northern or on the southern flank of an approximately E-W trending Tauride carbonate platform axis (Juteau, 1980 (Juteau, 1980). The plutonic sections and the metamorphic soles of the Tauride ophiolites are cut by numerous isolated microgabbro-diabase and minor pyroxenite dykes at different structural levels (Robertson et al

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U‐Pb dating of interspersed gabbroic magmatism and hydrothermal metamorphism during lower crustal accretion, Vema lithospheric section, Mid‐Atlantic Ridge

et al. 2015

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New U/Pb analyses of zircon and xenotime constrain the timing of magmatism, magmatic assimilation, and hydrothermal metamorphism during formation of the lower crust at the Mid-Atlantic Ridge. The studied sample is an altered gabbro from the Vema lithospheric section (11°N). Primary gabbroic minerals have been almost completely replaced by multiple hydrothermal overprints: cummingtonitic amphibole and albite formed during high-temperature hydration reactions and are overgrown first by kerolite and then prehnite and chlorite. In a previous study, clear inclusion-free zircons from the sample yielded Th-corrected 206 Pb/ 238 U dates of 13.528 ± 0.101 to 13.353 ± 0.057 Ma. Ti concentrations, reported here, zoning patterns and calculated Th/U of the dated grains are consistent with these zircons having grown during igneous crystallization. To determine the timing of hydrothermal metamorphism, we dated a second population of zircons, with ubiquitous <1-20 μm chlorite inclusions, and xenotimes that postdate formation of metamorphic albite. The textures and inclusions of the inclusion-rich zircons suggest that they formed by coupled dissolution-reprecipitation of metastable igneous zircon during or following hydrothermal metamorphism. Th-corrected 206 Pb/ 238 U dates for the inclusion-rich zircons range from 13.598 ± 0.012 to 13.503 ± 0.018 Ma and predate crystallization of all but one of the inclusion-free zircons, suggesting that the inclusion-rich zircons were assimilated from older hydrothermally altered wall rocks. The xenotime dates are sensitive to the Th correction applied, but even using a maximum correction, 206 Pb/ 238 U dates range from 13.341 ± 0.162 to 12.993 ± 0.055 Ma and postdate crystallization of both the inclusion-rich zircons and inclusion-free igneous zircons, reflecting a second hydrothermal event. The data provide evidence for alternating magmatism and hydrothermal metamorphism at or near the ridge axis during accretion of the lower crust at a ridge-transform intersection and suggest that hydrothermally altered crust was assimilated into younger gabbroic magmas. The results of this study show that high-precision U-Pb dating is a powerful method for studying the timing of magmatic and hydrothermal processes at mid-ocean ridges.

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Tectonic development of the Samail ophiolite: High‐precision U‐Pb zircon geochronology and Sm‐Nd isotopic constraints on crustal growth and emplacement

Cited by 158 publications

References 103 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

The tauride ophiolites of Anatolia (Turkey): A review

U‐Pb dating of interspersed gabbroic magmatism and hydrothermal metamorphism during lower crustal accretion, Vema lithospheric section, Mid‐Atlantic Ridge

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