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Maekawa, Hirokazu; Shozui, Masaya; Ishii, Teruaki; Saboda, Kristine L; Ogawa, Yujiro (1992): Geochemistry of metamorphic rocks from the Mariana and Izu-Ogasawara forearcs [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.770591, Supplement to: Maekawa, H et al. (1992): Metamorphic rocks from the serpentinite seamounts in the Mariana and Izu-Ogasawara forearcs. In: Fryer, P; Pearce, JA; Stokking, LB; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 125, 415-430, https://doi.org/10.2973/odp.proc.sr.125.131.1992

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Abstract:
During Leg 125, two serpentinite seamounts were drilled in the Mariana and Izu-Ogasawara forearcs. Together with abundant serpentinized peridotites, low-grade metamorphic rocks were recovered from both seamounts. The metamorphic rocks obtained from Hole 778A on Conical Seamount on the Mariana forearc contain common blueschist facies minerals, lawsonite, aragonite, blue amphibole, and sodic pyroxene. Approximate metamorphic conditions of these rocks are 150° to 250° C and 5 to 6 kb. These rocks are considered to have been uplifted by diapirism of serpentinite from a deeper portion within the subduction zone. This discovery presents direct evidence that blueschist facies metamorphism actually takes place within a subduction zone and provides new insight about trench-forearc tectonics.
The diagnostic mineral assemblage of the metamorphic rocks from Holes 783A and 784A on Torishima Forearc Seamount, in the Izu-Ogasawara region, is actinolite + prehnite + epidote, with a subassemblage of chlorite + quartz + albite + H2O, which is typical of low-pressure type, prehnite-actinolite facies of Liou et al. (1985). This metamorphism may represent ocean-floor metamorphism within trapped oceanic crust or in-situ metamorphism that occurred at depths beneath the island-arc.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: 22.932845 * Median Longitude: 145.201100 * South-bound Latitude: 19.499000 * West-bound Longitude: 141.738000 * North-bound Latitude: 30.964300 * East-bound Longitude: 146.696000
Date/Time Start: 1986-03-26T10:30:00 * Date/Time End: 1989-03-31T10:00:00
Event(s):
125-778A * Latitude: 19.499000 * Longitude: 146.666000 * Date/Time Start: 1989-02-22T06:30:00 * Date/Time End: 1989-02-24T19:25:00 * Elevation: -3924.0 m * Penetration: 107.6 m * Recovery: 22.8 m * Location: North Pacific Ocean * Campaign: Leg125 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 13 cores; 107.6 m cored; 0 m drilled; 21.2 % recovery
125-779A * Latitude: 19.512500 * Longitude: 146.696000 * Date/Time Start: 1989-02-28T10:00:00 * Date/Time End: 1989-03-04T03:00:00 * Elevation: -3958.0 m * Penetration: 317.2 m * Recovery: 73.24 m * Location: North Pacific Ocean * Campaign: Leg125 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 37 cores; 317.2 m cored; 0 m drilled; 23.1 % recovery
125-783A * Latitude: 30.964300 * Longitude: 141.788000 * Date/Time Start: 1989-03-24T05:30:00 * Date/Time End: 1986-03-26T10:30:00 * Elevation: -4660.0 m * Penetration: 168.2 m * Recovery: 46.95 m * Location: North Pacific Ocean * Campaign: Leg125 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 18 cores; 168.2 m cored; 0 m drilled; 27.9 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
10 datasets

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Datasets listed in this publication series

  1. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 1) Mineral associations of metamorphosed mafic rocks in ODP Hole 125-778A and 125-779A. https://doi.org/10.1594/PANGAEA.770541
  2. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 3) Representative analyes of pumpellyite of ODP Hole 125-778A and 125-779A. https://doi.org/10.1594/PANGAEA.770546
  3. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 2) Representative analyes of lawsonite of ODP Hole 125-778A. https://doi.org/10.1594/PANGAEA.770544
  4. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 6) Representative analyes of phengite, chlorite, albite, and sphene of ODP Hole 125-778A. https://doi.org/10.1594/PANGAEA.770580
  5. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 5) Representative analyes of sodic pyroxene and relict pyroxene of ODP Hole 125-778A. https://doi.org/10.1594/PANGAEA.770578
  6. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 4) Representative analyes of winchite and Ca-amphiboles of ODP Hole 125-778A. https://doi.org/10.1594/PANGAEA.770547
  7. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 7) Representative analyes of garnet, thomsonite, natrolite, chlorite, and sphene of ODP Hole 125-779A. https://doi.org/10.1594/PANGAEA.770581
  8. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 8) Mineral ssociation of metamorphosed mafic rocks in ODP Holes 125-778A and 125-779A. https://doi.org/10.1594/PANGAEA.770590
  9. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 9) Representative analyes of prehnite, epidote, actinolite, and chlorite of ODP Hole 125-783A. https://doi.org/10.1594/PANGAEA.770582
  10. Maekawa, H; Shozui, M; Ishii, T et al. (1992): (Table 10) Representative analyes of prehnite, epidote, actinolite, and chlorite of ODP Hole 125-784A. https://doi.org/10.1594/PANGAEA.770583