Forearc ages reveal extensive short-lived and rapid seafloor spreading following subduction initiation

Reagan, Mark K.; Heaton, D. E.; Schmitz, Mark D.; Pearce, Julian A.; Shervais, John W.; Koppers, Anthony A. P.

doi:10.1016/j.epsl.2018.11.020

Cited by 177 publications

(231 citation statements)

References 53 publications

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“…Although the oldest Site U1438 basalts have compositions similar to those of FAB from the Bonin fore arc, radiometric dating reveals that they are circa 50 Ma ( 40 Ar/ 39 Ar age of 49.9 ± 0.5 Ma renormalized to Fish Canyon Sanidine flux monitor of 28.201; Ishizuka et al, ). This indicates that they formed not by subduction initiation spreading but most probably by extension within or behind the Bonin Ridge embryonic arc (Reagan et al, ). The compositional similarity between the basalt from Site U1438 and Sites U1440 and U1441 FAB thus appears to reflect the depletion history of their common source region, rather than a common tectonic setting.…”

Section: Discussionmentioning

confidence: 99%

Magmatic Response to Subduction Initiation: Part 1. Fore‐arc Basalts of the Izu‐Bonin Arc From IODP Expedition 352

Shervais

Reagan

Haugen

et al. 2019

Geochem Geophys Geosyst

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137

115

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The Izu‐Bonin‐Mariana (IBM) fore arc preserves igneous rock assemblages that formed during subduction initiation circa 52 Ma. International Ocean Discovery Program (IODP) Expedition 352 cored four sites in the fore arc near the Ogasawara Plateau in order to document the magmatic response to subduction initiation and the physical, petrologic, and chemical stratigraphy of a nascent subduction zone. Two of these sites (U1440 and U1441) are underlain by fore‐arc basalt (FAB). FABs have mid‐ocean ridge basalt (MORB)‐like compositions, however, FAB are consistently lower in the high‐field strength elements (TiO2, P2O5, Zr) and Ni compared to MORB, with Na2O at the low end of the MORB field and FeO* at the high end. Almost all FABs are light rare earth element depleted, with low total REE, and have low ratios of highly incompatible to less incompatible elements (Ti/V, Zr/Y, Ce/Yb, and Zr/Sm) relative to MORB. Chemostratigraphic trends in Hole U1440B are consistent with the uppermost lavas forming off axis, whereas the lower lavas formed beneath a spreading center axis. Axial magma of U1440B becomes more fractionated upsection; overlying off‐axis magmas return to more primitive compositions. Melt models require a two‐stage process, with early garnet field melts extracted prior to later spinel field melts, with up to 23% melting to form the most depleted compositions. Mantle equilibration temperatures are higher than normal MORB (1,400 °C–1,480 °C) at relatively low pressures (1–2 GPa), which may reflect an influence of the Manus plume during subduction initiation. Our data support previous models of FAB origin by decompression melting but imply a source more depleted than normal MORB source mantle.

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Section: Discussionmentioning

confidence: 99%

Magmatic Response to Subduction Initiation: Part 1. Fore‐arc Basalts of the Izu‐Bonin Arc From IODP Expedition 352

Shervais

Reagan

Haugen

et al. 2019

Geochem Geophys Geosyst

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“…The timing of large‐scale lithospheric subduction is constrained by the age of igneous rocks of the IBM forearc that started in the Eocene, at ~52 Ma (Bloomer et al, ; Cosca et al, ; Ishizuka et al, ; Ishizuka et al, ; Reagan et al, ). The initial spreading generated forearc basalt (FAB) lavas at ~52 Ma; later volcanism produced low‐Si, then high‐Si boninites (~51–46 Ma: Ishizuka et al, , Ishizuka, Tani, et al, ; Reagan et al, , Reagan et al, ) to form the proto‐Bonin Ridge. Magmatic activity appears to have migrated inboard, with the FAB erupting closest to the trench (Sites U1440 and U1441) and the boninites (Sites U1439 and U1442 and the Bonin Ridge) erupting farther from the trench.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…Ishizuka, Taylor, et al () argue that the crustal stratigraphy of the IBM forearc is oceanic crust overlain by boninitic and later arc lavas, while Stern and Bloomer () and Ishizuka et al () argue that a broad swath of forearc crust formed by seafloor spreading after subduction initiation. Relating to IODP Expedition 352 results, Reagan et al (, ) have developed a hybrid of these models, in which FAB and low‐Si boninite magmas were generated during an initial period of seafloor spreading, whereas the high‐Si boninites erupted subsequently at discrete volcanic centers (i.e., the nascent arc) at 51.3 Ma. The rear arc basalts of the ASB (Site 351‐U1438) are younger than the Sites U1439 and U1442 boninite, which suggests that they formed by renewed volcanism west of the Bonin Ridge, after initial spreading ceased in the forearc (Ishizuka et al, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The geochemistry of the basement lavas (Hickey‐Vargas et al, ; Yogodzinski et al, ) indicates derivation from mantle source rocks that were more melt depleted than those of typical mid‐ocean ridges, similar to the IBM FABs (Shervais et al, ). The basaltic basement of the ASB (IODP Site U1438) is currently interpreted as part of the initial basement produced during subduction initiation (Arculus, Ishizuka, Bogus, & the Expedition 351 Scientists, ), although ages of the Amami‐Sankaku basement are concurrent with high‐Si boninite volcanism on the Bonin Ridge (Ishizuka et al, ), allowing an alternative explanation that this was the first IBM back arc basin (Reagan et al, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…It resulted from ~52 Ma of subduction of the Pacific Plate beneath the eastern margin of the Philippine Sea plate (Reagan et al, ). IODP expedition results were published recently, notably concerning the magmatic evolution (Brandl et al, ; Yogodzinski et al, ; Hickey‐Vargas et al, ; Shervais et al, ), and the age of IBM volcanic rocks (Barth et al, ; Ishizuka et al, ; Reagan et al, ). In addition, the drilled cores provided (hemi)pelagic sedimentary‐volcaniclastic successions and tectonic structures that bear information on the tectonic evolution of the outer IBM forearc.…”

Section: Introductionmentioning

confidence: 99%

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Postmagmatic Tectonic Evolution of the Outer Izu‐Bonin Forearc Revealed by Sediment Basin Structure and Vein Microstructure Analysis: Implications for a 15 Ma Hiatus Between Pacific Plate Subduction Initiation and Forearc Extension

Kurz

Micheuz

Christeson

et al. 2019

Geochem Geophys Geosyst

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International Ocean Discovery Program Expedition 352 recovered sedimentary-volcaniclastic successions and extensional structures (faults and extensional veins) that allow the reconstruction of the Izu-Bonin forearc tectonic evolution using a combination of shipboard core data, seismic reflection images, and calcite vein microstructure analysis. The oldest recorded biostratigraphic ages within fault-bounded sedimentary basins (Late Eocene to Early Oligocene) imply a~15 Ma hiatus between the formation of the igneous basement (52 to 50 Ma) and the onset of sedimentation. At the upslope sites (U1439 and U1442) extension led to the formation of asymmetric basins reflecting regional stretch of~16-19% at strain rates of~1.58 × 10 −16 to 4.62 × 10 −16 s −1 . Downslope Site U1440 (closer to the trench) is characterized by a symmetric graben bounded by conjugate normal faults reflecting regional stretch of~55% at strain rates of 4.40 × 10 −16 to 1.43 × 10 −15 s −1 . Mean differential stresses are in the range of~70-90 MPa. We infer that upper plate extension was triggered by incipient Pacific Plate rollback 15 Ma after subduction initiation. Extension was accommodated by normal faulting with syntectonic sedimentation during Late Eocene to Early Oligocene times. Backarc extension was assisted by magmatism with related Shikoku and Parece-Vela Basin spreading at~25 Ma, so that parts of the arc and rear arc, and the West Philippine backarc Basin were dismembered from the forearc. This was followed by slow-rift to postrift sedimentation during the transition from forearc to arc rifting to spreading within the Shikoku-Parece-Vela Basin system. Plain Language SummaryThis study examines the stress and deformation conditions and timing of extension in the Izu-Bonin forearc subsequent to subduction initiation by combining seismic images and microstructure analyses on veins and fault zones. By that we also examine a hiatus of 15 Ma between the formation of igneous forearc crust and the formation of sediment basins by forearc extension. This is implemented into an overall tectonic model at lithospheric scale.

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Timing of Tectonic and Magmatic Events in the Philippine Sea Plate since 50 Ma from High-Resolution Magnetostratigraphy of IODP Site U1438

Maffione

Morris

2021

Preprint

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The Philippine Sea Plate in the West Pacific is a unique natural laboratory to study subduction dynamics and the evolution of upper plate magmatism following subduction initiation. To investigate these processes, International Ocean Discovery Program Expedition 351 recovered at Site U1438, located in a rear-arc position, a complete sedimentary sequence from recent age to the early Eocene and the top of the underlying volcanic basement. The recovered cores offered the opportunity to study for the first time and in unprecedented detail the styles, products, and timing of the volcanic events that marked the emplacement, growth, and demise of the Kyushu-Palau volcanic arc following the inception of the Izu-Bonin-Mariana subduction. Here, we report a magnetostratigraphy for Site U1438 based on ∼60,000 remanence directions isolated from 1,063 archive half core sections and 429 discrete specimens. We identified 142 magnetic reversals and correlated 115 of them with the geomagnetic polarity timescale. When combined with additional biostratigraphic and geochronological constraints, our magnetostratigraphy allowed construction of a high-resolution age model for Site U1438 and the determination of changes in sedimentation rates. We show that following subduction initiation at 52-50 Ma and the emplacement of basalts in the rear-arc at 48.7 Ma, a diffuse volcanism in the rear-arc preceded the true emplacement of the Kyushu-Palau arc at 40.2 Ma, which then grew through four compositionally distinct eruptive phases until 28.8 Ma. Subsequent rollback of the Pacific slab triggered rifting of the arc (28.8-24.3 Ma) and ultimately back-arc spreading in the Shikoku and Parece Vela basins.

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Forearc ages reveal extensive short-lived and rapid seafloor spreading following subduction initiation

Cited by 177 publications

References 53 publications

Magmatic Response to Subduction Initiation: Part 1. Fore‐arc Basalts of the Izu‐Bonin Arc From IODP Expedition 352

Magmatic Response to Subduction Initiation: Part 1. Fore‐arc Basalts of the Izu‐Bonin Arc From IODP Expedition 352

Postmagmatic Tectonic Evolution of the Outer Izu‐Bonin Forearc Revealed by Sediment Basin Structure and Vein Microstructure Analysis: Implications for a 15 Ma Hiatus Between Pacific Plate Subduction Initiation and Forearc Extension

Timing of Tectonic and Magmatic Events in the Philippine Sea Plate since 50 Ma from High-Resolution Magnetostratigraphy of IODP Site U1438

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