Missing Oligocene Crust of the Izu-Bonin Arc: Consumed or Rejuvenated During Collision?

Tamura, Yoshihiko; Ishizuka, Osamu; Aoike, Kan; Kawate, Shinichi; Kawabata, Hiroshi; Chang, Qing; Saito, Satoshi; Tatsumi, Yoshiyuki; Arima, Makoto; Takahashi, Masaki; Kanamaru, Tatsuo; Kodaira, Shuichi; Fiske, Richard S.

doi:10.1093/petrology/egq002

Cited by 58 publications

(50 citation statements)

References 42 publications

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“…According to previous studies, the Tanzawa tonalities can be regarded as the exposed middle crust of the former IBM arc (Suyehiro et al 1996;Kawate and Arima 1998), and thus, the Tanzawa tonalitic pluton is generally considered to be a typical continental crust. The Tanzawa tonalities have very low K 2 O, low K 2 O/Na 2 O ratios (Ishihara et al 1976), and low initial 87 Sr/ 86 Sr ratios near mantle values (Kawate and Fujimaki 1996;Tamura et al 2010); they are also enriched in magnetite with high magnetic susceptibility (Ishihara et al 1976;Ishihara and Matsuhisa 1999). Fig.…”

Section: Geology and Samplingmentioning

confidence: 99%

Rock-magnetic properties of single zircon crystals sampled from the Tanzawa tonalitic pluton, central Japan

Sato

Yamamoto

et al. 2015

Earth Planet Sp

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This paper reports on the rock-magnetic properties of single zircon crystals, which are essential for future work establishing the reliable paleointensity method using single zircon crystals. Zircon crystals used in this study were sampled from the Nakagawa River, which crosses the Tanzawa tonalitic pluton in central Japan. Rock-magnetic measurements were conducted on 1037 grains of zircons, but many of these measurements are below the limits of the sensitivity of the magnetometers employed. Isothermal remanent magnetizations (IRMs) of 876 zircon crystal are below the practical resolution of this study; we infer that these crystals contain no or only minute quantities of ferromagnetic minerals. The other zircon crystals contain enough magnetic minerals to be measured in the DC SQUID magnetometer. Am 2 (80 zircons), combining the rock-magnetic parameter, we proposed the sample-selection criteria for future study of paleointensity experiments using single zircon crystals. In the case that the samples had high coercivity (B c ) values (>10 mT) or high M NRM /M IRM values (>~0.1), main remanence carriers are probably pyrrhotite and these samples are inappropriate for the paleointensity study. In the case that the samples had low B c values (<10 mT) and low M NRM /M IRM values (<~0.1), main remanence carriers seem to be nearly pure magnetite with pseudo-single-domain grain sizes, and these samples are expected to appropriate for the paleointensity study. Total thermoremanent magnetization (TRM) acquisition experiments were also carried out for 12 samples satisfying the above criteria. The TRM intensity was comparable with that of NRM, and a rough estimation of the paleointensity using NRM/TRM ratios shows field intensities consistent with the average geomagnetic field intensity at the Tanzawa tonalitic pluton for last 5 Myr.

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Section: Geology and Samplingmentioning

confidence: 99%

Rock-magnetic properties of single zircon crystals sampled from the Tanzawa tonalitic pluton, central Japan

Sato

Yamamoto

et al. 2015

Earth Planet Sp

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“…Petrological studies have shown that these plutons were emplaced at 16.8 to 10.6 Ma, which is almost coincident with the onset of the collision of the IBA (Saito et al 2007). In addition, the TPC, which intrudes the center of the Tanzawa Mountains (Kawate and Arima 1998), mainly consists of granite and tonalite that are thought to have been generated by partial melting of the middle/lower crust of the Honshu arc and IBA (Saito et al 2007;Tamura et al 2010;Tani et al 2010). …”

Section: Tectonic Settingmentioning

confidence: 99%

“…Here, the accreted crustal blocks of the IBA, which have a high velocity (green-blue parts with Vp above 6.0 km/s), are separated by dipping collisional boundaries that are accompanied by a lower-velocity sediment layer (red-orange parts with Vp below 5.0 km/s). The main body of the Kofu granitic complex (KGC), reportedly generated by partial melting of the subducted middle/lower crust of the IBA (e.g., Tamura et al 2010), is situated at depths greater than 4 km but forms a bump just beneath the Kofu Basin (red lines).…”

Section: Implications For Collision/subduction Processes In the Ibamentioning

confidence: 99%

“…Following extraction from the melting zone, the felsic magma ascended and intruded into the Honshu arc crust and Tanzawa block to form the KGC and TPC, respectively (Tamura et al 2010). Denser cumulates or restites may have remained at the bottom of the crust (Annen et al 2006) and contributed to the growth of the Honshu arc.…”

Section: Implications For Collision/subduction Processes In the Ibamentioning

confidence: 99%

“…Arai et al (2013) also showed that Miocene granitic plutons with high seismic velocities that intrude into the Honshu arc crust and accreted crustal blocks of the IBA (Tanzawa block) form the Kofu granitic complex (KGC) and the Tanzawa plutonic complex (TPC), respectively. Petrological investigations have suggested that these intrusive rocks formed by syncollisional magmatism of the IBA crust that subducted beneath the Honshu arc (Saito et al 2007;Tamura et al 2010;Tani et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Crustal structure in the northwestern part of the Izu collision zone in central Japan

Arai

Iwasaki

2014

Earth Planet Sp

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The Izu-Bonin arc (IBA) has been colliding with the Honshu arc since the middle Miocene, which together form the active Izu arc-arc collision zone (ICZ) in central Japan. To understand the entire collisional system, we have used refraction/wide-angle reflection data to model velocity structures of the Honshu arc, northwest of the ICZ. The seismic data indicate that the upper 4-km crust of the Honshu arc consists of a horizontally homogenous layer with P wave velocity (Vp) of 5.6 to 6.0 km/s and S wave velocity (Vs) of 3.4 to 3.7 km/s. This uniformity is in contrast with the heterogeneous structure further south, where the accreted crustal blocks of the IBA are bounded by dipping collisional boundaries. These contrasting structures suggest that crustal shorting caused by the arc-arc collision has been mostly accommodated within the IBA by reverse faulting along collisional boundaries, with the Honshu arc undergoing relatively little crustal deformation. The high-velocity body of the Kofu granitic complex (KGC), generated by partial melting of the subducted IBA crust, is mostly situated at >4-km depths but shallows significantly just beneath the Kofu Basin. This structural change implies that most of the KGC magma had erupted from just beneath the Kofu Basin.

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Crustal structure of the Izu collision zone in central Japan from seismic refraction data

et al. 2013

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[1] The Izu-Bonin arc (IBA) has been colliding with the more northerly Honshu arc since the middle Miocene, forming a globally unique active Izu arc-arc collision zone (ICZ) in central Japan. To determine crustal structure of the ICZ, we constrain P and S wave velocities from active source refraction data. The velocity structures reveal that the style of collisions of the Misaka, Tanzawa, and Izu blocks, which were derived from the IBA, has been controlled by subduction of the IBA. High-velocity rocks (Vp > 6.2 km/s) observed in the ICZ continuously extend to deeper crust, suggesting that plutonic rocks, formed by partial melting of the subducted IBA crust, intruded into the Honshu arc crust and the accreted crustal blocks of the IBA. The northernmost major fault in the ICZ dips southeastward, which is in clear contrast with other major northwestward dipping faults farther southeast. In the northernmost part of the ICZ, the upper 5 km crust of the Misaka block was delaminated from its lower part and obducted onto the Honshu arc. The Tanzawa block, southeast of the Misaka block, is bounded by northwestward dipping faults and is characterized by crustal stacking. A low-velocity sedimentary layer between the Tanzawa and Izu blocks dips northwestward along the collisional boundary and reaches~5 km depth, suggesting that the Izu block underthrust beneath the Tanzawa block. The overall geometry of the collisional boundaries exhibits a doubly vergent system, which is characterized by inward-dipping thrust faults on both sides.Citation: Arai, R., T. Iwasaki, H. Sato, S. Abe, and N. Hirata (2013), Crustal structure of the Izu collision zone in central Japan from seismic refraction data,

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Missing Oligocene Crust of the Izu-Bonin Arc: Consumed or Rejuvenated During Collision?

Cited by 58 publications

References 42 publications

Rock-magnetic properties of single zircon crystals sampled from the Tanzawa tonalitic pluton, central Japan

Rock-magnetic properties of single zircon crystals sampled from the Tanzawa tonalitic pluton, central Japan

Crustal structure in the northwestern part of the Izu collision zone in central Japan

Crustal structure of the Izu collision zone in central Japan from seismic refraction data

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