Mitchell, John G; Peate, David W; Murton, Bramley J; Pearce, Julian A; Arculus, Richard J; van der Laan, Sieger R (1992): Potassium and argon concentrations and age determination of ODP Site 125-782 and 125-786 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.767574, Supplement to: Mitchell, JG et al. (1992): K-Ar dating of samples from Sites 782 and 786 (Leg 125): the Izu-Bonin Forearc region. 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, 203-210, https://doi.org/10.2973/odp.proc.sr.125.136.1992
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Abstract:
K-Ar whole-rock ages have been obtained for 30 samples from Sites 782 and 786, Ocean Drilling Program Leg 125 in the Izu-Bonin (Ogasawara) forearc region. They form a trimodal spread of ages between 9 Ma and 44 Ma and are, with a few exceptions, consistent with the inferred lithostratigraphy. The ages have been interpreted in terms of at least two distinct episodes of magmatic and/or hydrothermal activity. A group of ten samples, including the lava flows, gave an isochron age of 41.3 ± 0.5 Ma (middle-late Eocene). This is thought to represent the age of the principal magmatic development of the volcanic forearc basement, and is comparable to published ages on equivalent rocks from other parts of the forearc basement high (e.g., the Ogasawara Islands). It may be significant that this age is slightly younger than the timing of major plate reorganization in the Western Pacific at about 43 Ma. This was followed by a minor episode of intrusive magmatism at 34.6 ± 0.7 Ma (early Oligocene) which appears to have reset the ages of some of the earlier units. This event probably corresponds to the initiation of rifting of the "proto-arc" to form the Parece Vela Basin. Boninitic samples were erupted during both episodes of magmatism, the earlier being of low-Ca boninite type and the later being of medium- and high-Ca types. It is also possible that a third episode of intrusive magmatism affected the Izu-Bonin forearc region at both Sites 782 and 786 at about 17 Ma. This would be consistent with magmatic activity elsewhere in the region during the Miocene, associated with the end of active spreading in the Parece Vela Basin and the start of arc activity in the West Mariana Ridge.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: 31.367550 * Median Longitude: 141.270175 * South-bound Latitude: 30.860000 * West-bound Longitude: 141.226000 * North-bound Latitude: 31.875000 * East-bound Longitude: 141.314200
Date/Time Start: 1989-03-16T18:00:00 * Date/Time End: 1989-04-16T17:00:00
Minimum Elevation: -3082.0 m * Maximum Elevation: -2958.9 m
Event(s):
125-782A * Latitude: 30.861000 * Longitude: 141.314200 * Date/Time Start: 1989-03-16T18:00:00 * Date/Time End: 1989-03-17T07:30:00 * Elevation: -2958.9 m * Penetration: 476.8 m * Recovery: 282 m * Location: North Pacific Ocean * Campaign: Leg125 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 50 cores; 476.8 m cored; 0 m drilled; 59.1 % recovery
125-782B * Latitude: 30.860000 * Longitude: 141.314000 * Date/Time Start: 1989-03-17T07:30:00 * Date/Time End: 1989-03-23T22:45:00 * Elevation: -2958.9 m * Penetration: 468.9 m * Recovery: 0.1 m * Location: North Pacific Ocean * Campaign: Leg125 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 1 core; 9.6 m cored; 0 m drilled; 1 % recovery
125-786A * Latitude: 31.875000 * Longitude: 141.226000 * Date/Time Start: 1989-04-04T12:00:00 * Date/Time End: 1989-04-04T12:00:00 * Elevation: -3070.0 m * Penetration: 166.5 m * Recovery: 84.95 m * Location: North Pacific Ocean * Campaign: Leg125 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 19 cores; 166.5 m cored; 0 m drilled; 51 % recovery
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Event label | Event | ||||
| 2 | Sample code/label | Sample label | Mitchell, John G | DSDP/ODP/IODP sample designation | ||
| 3 | Potassium oxide | K2O | % | Mitchell, John G | Flame photometry | |
| 4 | Potassium, standard deviation | K std dev | ± | Mitchell, John G | Flame photometry | |
| 5 | Argon-40 at standard pressure | 40Ar STP | 10-6 cm3/g | Mitchell, John G | Isotope ratio mass spectrometry | |
| 6 | Argon-40, standard deviation | 40Ar std dev | ± | Mitchell, John G | Isotope ratio mass spectrometry | |
| 7 | Argon | Ar | % | Mitchell, John G | atmospheric | |
| 8 | Age, dated | Age dated | ka | Mitchell, John G | Age, 40K/40Ar Potassium-Argon | |
| 9 | Age, dated standard deviation | Age dated std dev | ± | Mitchell, John G | Age, 40K/40Ar Potassium-Argon | 1 sigma |
| 10 | Lithologic unit/sequence | Unit | Mitchell, John G | morphology | ||
| 11 | Lithologic unit/sequence | Unit | Mitchell, John G | chemical, after Arculus et al., (1992, doi:10.2973/odp.proc.sr.125.137.1992) |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
300 data points