Details
| Original language | English |
|---|---|
| Pages (from-to) | 4973-4991 |
| Number of pages | 19 |
| Journal | Geochemistry, Geophysics, Geosystems |
| Volume | 17 |
| Issue number | 12 |
| Publication status | Published - 22 Nov 2016 |
Abstract
Most of the well-preserved ophiolite complexes are believed to form in suprasubduction zone (SSZ) settings. We compare physical properties and seismic structure of SSZ crust at the Izu-Bonin-Mariana (IBM) fore arc with oceanic crust drilled at Holes 504B and 1256D to evaluate the similarities of SSZ and oceanic crust. Expedition 352 basement consists of fore-arc basalt (FAB) and boninite lavas and dikes. P-wave sonic log velocities are substantially lower for the IBM fore arc (mean values 3.1–3.4 km/s) compared to Holes 504B and 1256D (mean values 5.0–5.2 km/s) at depths of 0–300 m below the sediment-basement interface. For similar porosities, lower P-wave sonic log velocities are observed at the IBM fore arc than at Holes 504B and 1256D. We use a theoretical asperity compression model to calculate the fractional area of asperity contact Af across cracks. Af values are 0.021–0.025 at the IBM fore arc and 0.074–0.080 at Holes 504B and 1256D for similar depth intervals (0–300 m within basement). The Af values indicate more open (but not necessarily wider) cracks in the IBM fore arc than for the oceanic crust at Holes 504B and 1256D, which is consistent with observations of fracturing and alteration at the Expedition 352 sites. Seismic refraction data constrain a crustal thickness of 10–15 km along the IBM fore arc. Implications and inferences are that crust-composing ophiolites formed at SSZ settings could be thick and modified after accretion, and these processes should be considered when using ophiolites as an analog for oceanic crust.
Keywords
- IBM fore arc, IODP Expedition 352, oceanic crust, ophiolite
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Geochemistry, Geophysics, Geosystems, Vol. 17, No. 12, 22.11.2016, p. 4973-4991.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Physical properties and seismic structure of Izu-Bonin-Mariana fore-arc crust
T2 - Results from IODP Expedition 352 and comparison with oceanic crust
AU - Christeson, G. L.
AU - Morgan, S.
AU - Kodaira, S.
AU - Yamashita, M.
AU - Almeev, R. R.
AU - Michibayashi, K.
AU - Sakuyama, T.
AU - Ferré, E. C.
AU - Kurz, W.
PY - 2016/11/22
Y1 - 2016/11/22
N2 - Most of the well-preserved ophiolite complexes are believed to form in suprasubduction zone (SSZ) settings. We compare physical properties and seismic structure of SSZ crust at the Izu-Bonin-Mariana (IBM) fore arc with oceanic crust drilled at Holes 504B and 1256D to evaluate the similarities of SSZ and oceanic crust. Expedition 352 basement consists of fore-arc basalt (FAB) and boninite lavas and dikes. P-wave sonic log velocities are substantially lower for the IBM fore arc (mean values 3.1–3.4 km/s) compared to Holes 504B and 1256D (mean values 5.0–5.2 km/s) at depths of 0–300 m below the sediment-basement interface. For similar porosities, lower P-wave sonic log velocities are observed at the IBM fore arc than at Holes 504B and 1256D. We use a theoretical asperity compression model to calculate the fractional area of asperity contact Af across cracks. Af values are 0.021–0.025 at the IBM fore arc and 0.074–0.080 at Holes 504B and 1256D for similar depth intervals (0–300 m within basement). The Af values indicate more open (but not necessarily wider) cracks in the IBM fore arc than for the oceanic crust at Holes 504B and 1256D, which is consistent with observations of fracturing and alteration at the Expedition 352 sites. Seismic refraction data constrain a crustal thickness of 10–15 km along the IBM fore arc. Implications and inferences are that crust-composing ophiolites formed at SSZ settings could be thick and modified after accretion, and these processes should be considered when using ophiolites as an analog for oceanic crust.
AB - Most of the well-preserved ophiolite complexes are believed to form in suprasubduction zone (SSZ) settings. We compare physical properties and seismic structure of SSZ crust at the Izu-Bonin-Mariana (IBM) fore arc with oceanic crust drilled at Holes 504B and 1256D to evaluate the similarities of SSZ and oceanic crust. Expedition 352 basement consists of fore-arc basalt (FAB) and boninite lavas and dikes. P-wave sonic log velocities are substantially lower for the IBM fore arc (mean values 3.1–3.4 km/s) compared to Holes 504B and 1256D (mean values 5.0–5.2 km/s) at depths of 0–300 m below the sediment-basement interface. For similar porosities, lower P-wave sonic log velocities are observed at the IBM fore arc than at Holes 504B and 1256D. We use a theoretical asperity compression model to calculate the fractional area of asperity contact Af across cracks. Af values are 0.021–0.025 at the IBM fore arc and 0.074–0.080 at Holes 504B and 1256D for similar depth intervals (0–300 m within basement). The Af values indicate more open (but not necessarily wider) cracks in the IBM fore arc than for the oceanic crust at Holes 504B and 1256D, which is consistent with observations of fracturing and alteration at the Expedition 352 sites. Seismic refraction data constrain a crustal thickness of 10–15 km along the IBM fore arc. Implications and inferences are that crust-composing ophiolites formed at SSZ settings could be thick and modified after accretion, and these processes should be considered when using ophiolites as an analog for oceanic crust.
KW - IBM fore arc
KW - IODP Expedition 352
KW - oceanic crust
KW - ophiolite
UR - http://www.scopus.com/inward/record.url?scp=85007099377&partnerID=8YFLogxK
U2 - 10.1002/2016GC006638
DO - 10.1002/2016GC006638
M3 - Article
AN - SCOPUS:85007099377
VL - 17
SP - 4973
EP - 4991
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
SN - 1525-2027
IS - 12
ER -