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Tamura, Yoshihiko; Busby, Cathy J.; Blum, Peter; Barker, Abigail

doi:10.2204/iodp.sp.350.2013

Cited by 6 publications

(13 citation statements)

References 75 publications

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“…Expedition 350 was the first expedition to drill in the Izu rear arc; all previous Integrated Ocean Drilling Program sites were drilled in or near the Izu-Bonin arc front or fore arc ( Figure F1B), leading to an incomplete view of Izu arc magmatism. Thus, the main objective of Expedition 350 was to reveal the history of "the missing half " of the subduction factory (Tamura et al, 2013). The second expedition (351) will focus on IBM arc origins by drilling west of the Kyushu-Palau Ridge (Figure F3), where it is inferred that the foundation, origin, and early evolution of the IBM arc are recorded (Arculus et al, 2013).…”

Section: Background and Objectivesmentioning

confidence: 99%

“…This site was chosen to provide a temporal record of rear-arc magma compositions, ideally from Paleogene to Neogene time, allowing comparison with the previously drilled fore-arc magmatic record and determination of across-arc geochemical variations throughout the history of the arc system. Rear-arc magmatic evolution is important to understand because the chemistry of the samples dredged from the tops of rear-arc volcanoes are more similar to the average composition of continental crust than those of arc-front volcanoes, and seismic crustal structure suggests that the rear arc overlies the majority of "continental type" crust in the Izu arc system (Tamura et al, 2013). Figure F1.…”

Section: Background and Objectivesmentioning

confidence: 99%

“…The preliminary results of seismic surveys for Site U1437 are summarized briefly here from Tamura et al (2013); full results of the seismic surveys will be presented in a full paper at a later time after drilling results are integrated (M. Yamashita, pers. comm., 2014).…”

Section: Site U1437: Izu Rear Arcmentioning

confidence: 99%

“…Tamura et al (2013) estimated the 5 km/s iso-velocity contour to lie at ~2100 mbsf at Site U1437 and suggested that these rocks could be Oligocene-Eocene "igneous basement, " consisting of lava and/or intrusions. Line IBM3-NW5 ( Figure F15A) clearly shows that Site U1437 lies in a volcano-bounded basin between the Enpo and Manji rear-arc seamount chains.…”

Section: Iodp Proceedingsmentioning

confidence: 99%

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Expedition 350 summary

Tamura¹,

Busby²,

Blum³

et al. 2015

Proceedings of the International Ocean Discovery Program

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International Ocean Discovery Program (IODP) Hole U1436A (proposed Site IBM-4GT) lies in the western part of the Izu fore-arc basin, ~60 km east of the arc-front volcano Aogashima, ~170 km west of the axis of the Izu-Bonin Trench, and 1.5 km west of Ocean Drilling Program (ODP) Site 792, at 1776 meters below sea level (mbsl). It was drilled as a 150 m deep geotechnical test hole for potential future deep drilling (5500 meters below seafloor [mbsf ]) at proposed Site IBM-4 using the D/V Chikyu. Core from Site U1436 yielded a rich record of Late Pleistocene explosive volcanism, including a distinctive black glassy mafic ash layer that may record a large-volume subaqueous eruption on the Izu arc front. Because of the importance of this discovery, Site U1436 was drilled in three additional holes (U1436B, U1436C, and U1436D), as part of a contingency operation, in an attempt to get better recovery on the black glassy mafic ash layer and its enclosing sediments and to better constrain its thickness.IODP Site U1437 is located in the Izu rear arc, ~330 km west of the axis of the Izu-Bonin Trench and ~90 km west of the arc-front volcanoes Myojinsho and Myojin Knoll, at 2117 mbsl. The primary scientific objective for Site U1437 was to characterize "the missing half of the subduction factory" because numerous ODP/Integrated Ocean Drilling Program sites had been drilled in the arc-front to fore-arc region (i.e., ODP Site 782A Leg 126), but this was the first site to be drilled in the rear-arc region of the Izu arc. A complete view of the arc system is needed to understand the formation of oceanic arc crust and its evolution into continental crust. Site U1437 on the rear arc had excellent core recovery in Holes U1437B and U1437D, and we succeeded in hanging the longest casing ever in the history of R/V JOIDES Resolution scientific drilling (1085.6 m) in Hole U1437E and cored to 1806.5 mbsf.The stratigraphy at Site U1437 was divided into seven lithostratigraphic units (I-VII) that were distinguished from each other based on the proportions and characteristics of tuffaceous mud/mudstone and interbedded tuff, lapilli-tuff, and tuff-breccia. The section is much more mud rich than expected, with ~60% tuffaceous mud for the section as a whole (89% in the uppermost 433 m) and high sedimentation rates of 100-260 m/My for the upper 1320 m (Units I-V). The proportion (40%) and grain size of volcaniclastics are much smaller than expected for an intra-arc basin, composed half of ash/tuff and half of lapilli-tuff of fine grain size (clasts <3 cm). These volcaniclastics were deposited by suspension settling through water and from density currents, in relatively distal settings. Volcanic blocks are only sparsely scattered through the lowermost 25% of the section (Units VI and VII, 1320-1806.5 mbsf ), which includes hyaloclastite, in situ quench-fragmented blocks, and a rhyolite peperite intrusion (i.e., proximal deposits). The transition from unconsolidated to lithified rocks occurred progressively; however, sediments were consider...

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Section: Background and Objectivesmentioning

confidence: 99%

Section: Background and Objectivesmentioning

confidence: 99%

Section: Site U1437: Izu Rear Arcmentioning

confidence: 99%

Section: Iodp Proceedingsmentioning

confidence: 99%

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Expedition 350 summary

Tamura¹,

Busby²,

Blum³

et al. 2015

Proceedings of the International Ocean Discovery Program

View full text Add to dashboard Cite

show abstract

“…Expedition 350 was the first expedition to drill in the Izu rear arc; all previous IODP/ODP sites were drilled in or near the Izu-Bonin arc front or fore-arc ( Figure 2), leading to an incomplete view of Izu arc magmatism. Thus, the main objective of Expedition 350 was to reveal the history of "the missing half" of the subduction factory (Tamura et al, 2013). The second expedition (351) focused on IBM arc origins by drilling west of the Kyushu-Palau Ridge (Figure 1), where it was inferred that the foundation, origin, and early evolution of the IBM arc are recorded (Arculus et al, 2013(Arculus et al, , 2015.…”

Section: Introductionmentioning

confidence: 99%

The missing half of the subduction factory: shipboard results from the Izu rear arc, IODP Expedition 350

Busby

Tamura

Blum

et al. 2017

International Geology Review

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IODP Expedition 350 was the first to be drilled in the rear part of the Izu-Bonin, although several sites had been drilled in the arc axis to fore-arc region; the scientific objective was to understand the evolution of the Izu rear arc, by drilling a deepwater volcaniclastic section with a long temporal record (Site U1437). The Izu rear arc is dominated by a series of basaltic to dacitic seamount chains up to ~100 km long roughly perpendicular to the arc front. Dredge samples from these are geochemically distinct from arc front rocks, and drilling was undertaken to understand this arc asymmetry. Site U1437 lies in a ~20 km-wide basin between two rear arc seamount chains, ~90 km west of the arc front, and was drilled to 1804 mbsf with excellent recovery. We expected to drill a volcaniclastic apron, but the section is much more mud-rich than expected (~60%), and the remaining fraction of the section is much finer-grained than predicted from its position within the Izu arc, composed half of ashes/tuffs, and half of lapilli tuffs of fine grain size (clasts <3 cm). Volcanic blocks (>6.4 cm) are only sparsely scattered through the lowermost 25% of the section, and only one igneous unit was encountered, a rhyolite peperite intrusion at ~1390 mbsf. The lowest biostratigaphic datum is at 867 mbsf (~6.5 Ma), the lowest paleomagnetic datum is at ~1300 mbsf (~9 Ma), and the rhyolite peperite at ~1390 mbsf has yielded a U-Pb zircon concordia intercept age of 13.6 +1.6/-1.7 Ma. Both arc front and rear arc sources contributed to the fine-grained (distal) tephras of the upper 1320m, but the coarse-grained (proximal) volcaniclastics in the lowest 25% of the section are geochemically similar to the arc front, suggesting arc asymmetry is not recorded in rocks older than ~13 Ma.

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Generation of Silicic Melts in the Early Izu‐Bonin Arc Recorded by Detrital Zircons in Proximal Arc Volcaniclastic Rocks From the Philippine Sea

Barth

Tani

Meffre

et al. 2017

Geochem Geophys Geosyst

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A 1.2 km thick Paleogene volcaniclastic section at International Ocean Discovery Program Site 351‐U1438 preserves the deep‐marine, proximal record of Izu‐Bonin oceanic arc initiation, and volcano evolution along the Kyushu‐Palau Ridge (KPR). Pb/U ages and trace element compositions of zircons recovered from volcaniclastic sandstones preserve a remarkable temporal record of juvenile island arc evolution. Pb/U ages ranging from 43 to 27 Ma are compatible with provenance in one or more active arc edifices of the northern KPR. The abundances of selected trace elements with high concentrations provide insight into the genesis of U1438 detrital zircon host melts, and represent useful indicators of both short and long‐term variations in melt compositions in arc settings. The Site U1438 zircons span the compositional range between zircons from mid‐ocean ridge gabbros and zircons from relatively enriched continental arcs, as predicted for melts in a primitive oceanic arc setting derived from a highly depleted mantle source. Melt zircon saturation temperatures and Ti‐in‐zircon thermometry suggest a provenance in relatively cool and silicic melts that evolved toward more Th and U‐rich compositions with time. Th, U, and light rare earth element enrichments beginning about 35 Ma are consistent with detrital zircons recording development of regional arc asymmetry and selective trace element‐enriched rear arc silicic melts as the juvenile Izu‐Bonin arc evolved.

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Cited by 6 publications

References 75 publications

Expedition 350 summary

Expedition 350 summary

The missing half of the subduction factory: shipboard results from the Izu rear arc, IODP Expedition 350

Generation of Silicic Melts in the Early Izu‐Bonin Arc Recorded by Detrital Zircons in Proximal Arc Volcaniclastic Rocks From the Philippine Sea

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