Facey, D; Housden, J; O'Reilly, W (1985): Magnetic properties, grain sizes and minerals at DSDP Site 83-504B [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.805183, Supplement to: Facey, D et al. (1985): A magneto-petrological study of rocks from Leg 83, Hole 504B, Deep Sea Drilling Project. In: Anderson, RN; Honnorez, J; Becker, K; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 83, 339-346, https://doi.org/10.2973/dsdp.proc.83.117.1985
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Abstract:
Twenty-seven samples from the Leg 83 section of Hole 504B have been investigated using magnetic, optical, and electron optical methods. The primary magnetic mineral to crystallize was titanomagnetite of approximate composition Fe2.4Ti0.6O4 (TM60), but none survives, nor is there evidence of titanomaghemite produced by oxidation of TM60. The average measured magnetic properties can be interpreted in terms of magnetite, Fe3O4, having average grain size of <1 µm and present in average volume concentration of - 0.5%. The intensity of the natural remanent magnetization (NRM) of the rocks could also be accounted for as being a thermoremanence carried by this mineral.
Although the heterogeneity of the titanomagnetite grains could be detected optically, the texture of the intergrown phases is poorly developed. In some samples from the massive units of the lower part of the section, trellis patterns were visible. The Fe3O4 present in the intergrowths is too intimately mixed with the other intergrown phases to be revealed by electron microprobe analysis that simply returns the bulk composition of the intergrowth (oxidized TM60). The path by which the mineral assemblage evolved from TM60 to an Fe304-containing intergrowth, under the temperature and pressure conditions obtaining in the Leg 83 section, makes interesting speculation. Deuteric oxidation, maghemitization/inversion, or some hypothetical low-temperature/high-pressure oxidation by a leaching-of-iron process may all play roles.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Latitude: 1.227200 * Longitude: -83.730200
Date/Time Start: 1981-11-22T00:00:00 * Date/Time End: 1982-01-02T00:00:00
Event(s):
83-504B * Latitude: 1.227200 * Longitude: -83.730200 * Date/Time Start: 1981-11-22T00:00:00 * Date/Time End: 1982-01-02T00:00:00 * Elevation: -3460.0 m * Penetration: 1350 m * Recovery: 107.7 m * Campaign: Leg83 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: Leg 83 of DSDP was devoted entirely to coring and experiments in Hole 504B, the deepest borehole to date into the oceanic crust. Hole 504B now extends over a kilometer into basement, nearly twice as far as any other DSDP hole, and it is the only DSDP hole to have clearly penetrated into the intrusive sheeted dikes that underlie the extrusive pillow lavas of the upper oceanic crust. At Hole 504B, Leg 83 continued an ongoing DSDP effort that began during Legs 68, 69, and 70 in 1979, and also included part of Leg 92 in 1983. 71 cores; 514 m cored; 0 m drilled; 21 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
2 datasets
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Datasets listed in this publication series
- Facey, D; Housden, J; O'Reilly, W (1985): (Table 1) Magnetic properties at DSDP Hole 83-504B. https://doi.org/10.1594/PANGAEA.805180
- Facey, D; Housden, J; O'Reilly, W (1985): (Table 2) Grain sizes and minerals at DSDP Hole 83-504B. https://doi.org/10.1594/PANGAEA.805182