Subduction initiation and ophiolite crust: new insights from IODP drilling

Reagan, Mark K.; Pearce, Julian A.; Petronotis, K. E.; Almeev, Renat R.; Avery, Aaron; Carvallo, C.; Chapman, Timothy; Christeson, G. L.; Ferré, E. C.; Godard, Marguerite; Heaton, D. E.; Kirchenbaur, Maria; Kurz, Walter; Kutterolf, Steffen; Li, Hongyan; Li, Yibing; Michibayashi, Katsuyoshi; Morgan, Sally; Nelson, W. R.; Prytulak, Julie; Python, Marie; Robertson, Alastair H.F.; Ryan, Jeffrey G.; Sager, William W.; Sakuyama, Tetsuya; Shervais, John W.; Shimizu, Kenji; Whattam, Scott A.

doi:10.1080/00206814.2016.1276482

Cited by 157 publications

(185 citation statements)

References 47 publications

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“…The main difference between these two systems appears to be the lack of fluid mobile trace elements, suggesting little hydrous flux from the slab in the first-formed forearc basalts (FABs) in the IBM system (Reagan et al, 2010;Reagan et al, 2017) contrasting with the significant enrichment in fluid mobile elements and measured elevated water contents in the SEMFR volcanics Ribeiro et al, 2015). This difference may be explained by the fact that the current southern Mariana rifted margin formed over a preexisting long-lived subduction zone.…”

Section: The Southern Mariana Margin As An Analog For Subduction Zonementioning

confidence: 99%

Diffuse Extension of the Southern Mariana Margin

et al. 2018

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Extension within the southern Mariana margin occurs both normal to and parallel to the trench. Trench‐normal extension takes place along focused and broad backarc spreading axes forming crust that is passively accreted to the rigid Philippine Sea plate flank to the northwest. To the southeast, trench‐parallel extension has split apart the Eocene‐Miocene forearc terrain accreting new crust diffusely over a 150–200 km wide zone forming a pervasive volcano‐tectonic fabric oriented at high angles to the trench and the backarc spreading center. Earthquake seismicity indicates active extension over this forearc region and basement samples date young although waning volcanic activity. Such diffuse formation of new oceanic crust and lithosphere is unusual; in most oceanic settings extension rapidly focuses to narrow plate boundary zones—a defining feature of plate tectonics. Diffuse crustal accretion has been inferred to occur during subduction zone infancy, however. We hypothesize that in a near‐trench extensional setting, the continual addition of water from the subducting slab creates a weak overriding hydrous lithosphere that deforms broadly. This process counteracts mantle dehydration and strengthening proposed to occur at mid‐ocean ridges that may help to focus deformation and melt delivery to narrow plate boundary zones. The observations from the southern Mariana margin suggest that where lithosphere is weakened by high water content narrow seafloor spreading centers cannot form. These conditions likely prevail during subduction zone infancy, explaining the diffuse contemporaneous volcanism inferred in this setting.

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Section: The Southern Mariana Margin As An Analog For Subduction Zonementioning

confidence: 99%

Diffuse Extension of the Southern Mariana Margin

et al. 2018

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“…During subduction initiation (∼52–47 Ma), igneous activity produced MORB‐like forearc basalts (“FAB”) (Reagan et al, ), low‐Ca boninites, low‐K tholeiitic to calc‐alkaline arc basalts, and subordinate low‐K rhyodacite within the subsequent forearc area. Typical arc and rear‐arc volcanism, represented by the Kyushu‐Palau arc, was initiated during the Eocene to Oligocene, shedding volcanic material into the modern IBM forearc (Ishizuka et al, ; Reagan et al, ; Ryan et al, ; Taylor, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

Tephrostratigraphy and Provenance From IODP Expedition 352, Izu‐Bonin Arc: Tracing Tephra Sources and Volumes From the Oligocene to Recent

Kutterolf

Schindlbeck

Robertson

et al. 2018

Geochem Geophys Geosyst

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Provenance studies of widely distributed tephras, integrated within a well‐defined temporal framework, are important to deduce systematic changes in the source, scale, distribution, and changes in regional explosive volcanism. Here, we establish a robust tephrochronostratigraphy for a total of 157 marine tephra layers collected during IODP Expedition 352. We infer at least three major phases of highly explosive volcanism during Oligocene to Pleistocene time. Provenance analysis based on glass composition assigns 56 of the tephras to a Japan source, including correlations with 12 major and widespread tephra layers resulting from individual eruptions in Kyushu, Central Japan, and North Japan between 115 ka and 3.5 Ma. The remaining 101 tephras are assigned to four source regions along the Izu‐Bonin arc. One, exclusively assigned to the Oligocene age, is proximal to the Bonin Ridge islands; two reflect eruptions within the volcanic front and back‐arc of the central Izu‐Bonin arc, and a fourth region corresponds to the Northern Izu‐Bonin arc source. First‐order volume estimates imply eruptive magnitudes ranging from 6.3 to 7.6 for Japan‐related eruptions and between 5.5 and 6.5 for IBM eruptions. Our results suggest tephras between 30 and 22 Ma reflect a subtly different Izu‐Bonin chemical signature compared to the recent arc. After a ∼9 Ma gap in eruption, tephra supply from the Izu‐Bonin arc predominated from 15 to 5 Ma, and finally a subequal mixture of tephra sources from the (palaeo)Honshu and Izu‐Bonin arcs occured within the last ∼5 Ma.

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“…We present here new data on the petrogenesis of FAB sampled by IODP (International Ocean Discovery Program) Expedition 352 (Reagan et al, , ). Two holes—U1440 and U1441—are composed almost entirely of FAB, with minor FAB‐related basaltic andesite.…”

Section: Introductionmentioning

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 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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Subduction initiation and ophiolite crust: new insights from IODP drilling

Cited by 157 publications

References 47 publications

Diffuse Extension of the Southern Mariana Margin

Diffuse Extension of the Southern Mariana Margin

Tephrostratigraphy and Provenance From IODP Expedition 352, Izu‐Bonin Arc: Tracing Tephra Sources and Volumes From the Oligocene to Recent

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

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