Origin of geochemically heterogeneous mid-ocean ridge basalts from the Macquarie Ridge Complex, SW Pacific

Jiang, Qiang; Merle, Renaud; Jourdan, Fred; Olierook, Hugo K.H.; Chiaradia, Massimo; Evans, Katy; Wang, Xuan‐Ce; Conway, Chris E.; Bostock, Helen; Wysoczanski, Richard J.

doi:10.1016/j.lithos.2020.105893

Cited by 8 publications

(23 citation statements)

References 71 publications

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“…Shipboard magnetic anomaly data from cruise MGL1803 reveal that magnetic anomaly is typically higher on the western side of Puysegur Ridge and support a continental‐oceanic juxtaposition (Figure 10). Additionally, although few and sparse, dredge samples from the western flank of Puysegur Ridge and southern Puysegur Bank found altered cobbles of basalt, diabase, and gabbro with mid‐ocean ridge basalt and ocean‐island basalt affinities (Figure 10; Mortimer, 1994), consistent with the geochemistry of other igneous rocks sampled along the MRC (e.g., Jiang et al., 2021). Recently, Hightower et al.…”

Section: Discussionsupporting

confidence: 61%

Strike‐Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints From Puysegur Margin, New Zealand

et al. 2021

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Subduction initiation often takes advantage of previously weakened lithosphere and may preferentially nucleate along pre-existing plate boundaries. To evaluate how past tectonic regimes and inherited lithospheric structure might lead to self-sustaining subduction, we present an analysis of the Puysegur Trench, a young subduction zone with a rapidly evolving tectonic history. The Puysegur margin, south of New Zealand, has experienced a transformation from rifting to seafloor spreading to strikeslip, and most recently to incipient subduction, all in the last ∼45 million years. Here we present deeppenetrating multichannel reflection and ocean-bottom seismometer tomographic images to document crustal structures along the margin. Our images reveal that the overriding Pacific Plate beneath the Solander Basin contains stretched continental crust with magmatic intrusions, which formed from Eocene-Oligocene rifting between the Campbell and Challenger plateaus. Rifting was more advanced to the south, yet never proceeded to breakup and seafloor spreading in the Solander Basin as previously thought. Subsequent strike-slip deformation translated continental crust northward causing an oblique collisional zone, with trailing ∼10 Myr old oceanic lithosphere. Incipient subduction transpired as oceanic lithosphere from the south forcibly underthrust the continent-collision zone. We suggest that subduction initiation at the Puysegur Trench was assisted by inherited buoyancy contrasts and structural weaknesses that were imprinted into the lithosphere during earlier phases of continental rifting and strike-slip along the plate boundary. The Puysegur margin demonstrates that forced nucleation along a strike-slip boundary is a viable subduction initiation scenario and should be considered throughout Earth's history.Plain Language Summary Subduction zones, where one plate underthrusts another, are the principal driver of tectonic plate motions on Earth; however, the origin of these convergent margins remains unsolved. Geoscientists have proposed that the process of forming a new subduction zone takes advantage of weaknesses such as buoyancy contrasts and re-using older weak plate boundaries. To test these ideas, we use new seismic images to document tectonic structures at the Puysegur margin, an incipient subduction zone south of New Zealand. Our images reveal that the upper plate of the Puysegur margin consists mostly of stretched continental lithosphere that formed during an Eocene-Oligocene extension phase. Following extension, a translational phase juxtaposed thin and high-density oceanic lithosphere against thick and low-density continental lithosphere in a wide damage zone. Convergence across this zone led to underthrusting of the Australian Plate beneath the Pacific Plate and the development of the newly established Puysegur subduction zone. Our results demonstrate that subduction initiation was aided by lithospheric buoyancy contrasts and weak zones inherited from earlier phases of tectonic activity. Our findings argue that pre-...

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Section: Discussionsupporting

confidence: 61%

Strike‐Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints From Puysegur Margin, New Zealand

et al. 2021

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“…Two groundmass samples, MQ17-06 and MQ17-07, from the central northern portion of the island yielded plateau ages of 16.6 ± 2.3 Ma (p = 0.93; MQ17-06) and 10.1 ± 2.2 Ma (p = 0.59; MQ17-07). However, alteration minerals (e.g., chlorite, zeolite, and sericite; Figures 2a and 2b) are common in the groundmass, and the LOI of sample MQ17-06 (LOI = 3.2 wt.%) is higher than that of sample MQ17-07 ( Figure S2; LOI = 2.0 wt%; Jiang et al, 2020), so the plateau age of sample MQ17-06 is likely to be older than its true crystallization age, based on the probable loss of K 2 O from the glass component. Groundmass sample MQ17-10 yielded a 64% mini-plateau age with a large uncertainty (Table 1, Figure S1).…”

Section: Ar/ 39 Ar Ages Of Macquarie Islandmentioning

confidence: 97%

“…Rocks from the MRC seamounts and Macquarie Island are alkaline to sub‐alkaline basalts with geochemical compositions ranging from N‐MORB to E‐MORB and isotopic compositions lying between the fields of MORBs from the Pacific‐Antarctic Ridge and HIMU‐like basalts (Conway et al., 2012; Jiang et al., 2020; Kamenetsky et al., 2000; Kamenetsky & Maas, 2002). The geochemical and isotopic compositions are highly heterogeneous for rocks from each individual seamount (Conway et al., 2012; Jiang et al., 2020), and Macquarie Island (Kamenetsky et al., 2000; Kamenetsky & Maas, 2002), and there is no systematic latitudinal variations along the MRC (Jiang et al., 2020). Such heterogeneous geochemical characteristics were interpreted to be unrelated to hotspot contamination, but were attributed to pyroxenite veins generated in the metasomatized upper mantle (Jiang et al., 2020).…”

Section: Geological Settingmentioning

confidence: 99%

Timing of Seafloor Spreading Cessation at the Macquarie Ridge Complex (SW Pacific) and Implications for Upper Mantle Heterogeneity

Jiang

Merle

Jourdan

et al. 2021

Geochem Geophys Geosyst

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Mid-ocean ridges are Earth's most important producers of igneous rocks and contribute ∼75% of Earth's present-day volcanism (Crisp, 1984). While much is known about the production of mid-ocean ridge basalts (MORBs) by mantle upwelling and decompression melting at active mid-ocean ridges, the magmatic processes during mid-ocean ridges' slowdown and eventual cessation in response to plate reorganization are less well understood. Despite, the wide distribution of extinct mid-ocean ridges on Earth (see review of Ma-cLeod et al., 2017), much of current knowledge of such processes comes from studies of the fossil Phoenix Ridge off the Antarctic Peninsula (

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“…Rocks from the MRC seamounts and Macquarie Island are alkaline to sub-alkaline basalts with geochemical compositions ranging from N-MORB to E-MORB and isotopic compositions lying between the fields of MORBs from the Pacific-Antarctic Ridge and HIMU-like basalts [Conway et al, 2012;Jiang et al, 2020;Kamenetsky et al, 2000;Kamenetsky & Maas, 2002].…”

Section: Geochemistry Of the Macquarie Ridge Morbsmentioning

confidence: 99%

“…Geochemical and isotopic data for basalts from the MRC and other extinct mid-ocean ridges reveal a continuum from normal MORB (N-MORB) to transitional MORB to enriched MORB [E-MORB;Castillo et al, 2010;Choi et al, 2008;Jiang et al, 2020;Kamenetsky et al, 2000;Tian et al, 2011]. The production of geochemically and isotopically varied magma by dying mid-ocean ridges has led to different hypotheses to account for the heterogeneity of the asthenospheric upper mantle and evolution of the mantle source at mid-ocean ridges.…”

Section: Introductionmentioning

confidence: 99%

Timing of seafloor spreading cessation at the Macquarie Ridge Complex (SW Pacific) and implications for upper mantle heterogeneity

Jiang¹,

Whitehouse²,

Merle³

et al. 2021

Goldschmidt2021 Abstracts

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Origin of geochemically heterogeneous mid-ocean ridge basalts from the Macquarie Ridge Complex, SW Pacific

Cited by 8 publications

References 71 publications

Strike‐Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints From Puysegur Margin, New Zealand

Strike‐Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints From Puysegur Margin, New Zealand

Timing of Seafloor Spreading Cessation at the Macquarie Ridge Complex (SW Pacific) and Implications for Upper Mantle Heterogeneity

Timing of seafloor spreading cessation at the Macquarie Ridge Complex (SW Pacific) and implications for upper mantle heterogeneity

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