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Alt, Jeffrey C; Muehlenbachs, Karlis; Honnorez, Jose J (1986): Oxygen isotope concentrations of minerals from the upper kilometer of the ocean crust, DSDP Hole 504B [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.713298, Supplement to: Alt, JC et al. (1986): An oxygen isotopic profile through the upper kilometer of the oceanic crust, DSDP Hole 504B. Earth and Planetary Science Letters, 80(3-4), 217-229, https://doi.org/10.1016/0012-821X(86)90106-8

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Abstract:
DSDP Hole 504B is the deepest basement hole in the oceanic crust, penetrating through a 571.5 m pillow section, a 209 m lithologic transition zone, and 295 m into a sheeted dike complex. An oxygen isotopic profile through the upper crust at Site 504 is similar to that in many ophiolite complexes, where the extrusive section is enriched in 18O relative to unaltered basalts, and the dike section is variably depleted and enriched. Basalts in the pillow section at Site 504 have delta 18O values generally ranging from +6.1 to +8.5 per mil SMOW (mean= +7.0 per mil ), although minor zeolite-rich samples range up to 12.7 per mil . Rocks depleted in 18O appear abruptly at 624 m sub-basement in the lithologic transition from 100% pillows to 100% dikes, coinciding with the appearance of greenschist facies minerals in the rocks. Whole-rock values range to as low as +3.6 per mil , but the mean values for the lithologic transition zone and dike section are +5.8 and +5.4 per mil , respectively.
Oxygen and carbon isotopic data for secondary vein minerals combined with the whole rock data provide evidence for the former presence of two distinct circulation systems separated by a relatively sharp boundary at the top of the lithologic transition zone. The pillow section reacted with seawater at low temperatures (near 0°C up to a maximum of around 150°C) and relatively high water/rock mass ratios (10-100); water/rock ratios were greater and conditions were more oxidizing during submarine weathering of the uppermost 320 m than deeper in the pillow section. The transition zone and dikes were altered at much higher temperatures (up to about 350°C) and generally low water/rock mass ratios (~1), and hydrothermal fluids probably contained mantle-derived CO2. Mixing of axial hydrothermal fluids upwelling through the dike section with cooler seawater circulating in the overlying pillow section resulted in a steep temperature gradient (~2.5°C/m) across a 70 m interval at the top of the lithologic transition zone. Progressive reaction during axial hydrothermal metamorphism and later off-axis alteration led to the formation of albite- and Ca-zeolite-rich alteration halos around fractures. This enhanced the effects of cooling and 18O enrichment of fluids, resulting in local increases in delta 18O of rocks which had been previously depleted in 18O during prior axial metamorphism.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 1.227140 * Median Longitude: -83.730140 * South-bound Latitude: 1.227000 * West-bound Longitude: -83.730200 * North-bound Latitude: 1.227200 * East-bound Longitude: -83.730000
Date/Time Start: 1979-12-04T00:00:00 * Date/Time End: 1982-01-02T00:00:00
Event(s):
70-504B * Latitude: 1.227000 * Longitude: -83.730000 * Date/Time: 1979-12-04T00:00:00 * Elevation: -3460.0 m * Penetration: 836.1 m * Recovery: 91.6 m * Campaign: Leg70 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 40 cores; 328.6 m cored; 18.5 m drilled; 27.9 % recovery
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:
5 datasets

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Datasets listed in this publication series

  1. Alt, JC; Muehlenbachs, K; Honnorez, JJ (1986): (Table 5) Oxygen isotopic composition and calculated equilibrium temperatures of formation for vein carbonates from DSDP Hole 504B. https://doi.org/10.1594/PANGAEA.713297
  2. Alt, JC; Muehlenbachs, K; Honnorez, JJ (1986): (Table 2) Oxygen isotopic composition and calculated temperatures of formation of clay minerals from DSDP Hole 504B. https://doi.org/10.1594/PANGAEA.713290
  3. Alt, JC; Muehlenbachs, K; Honnorez, JJ (1986): (Table 4) Oxygen isotopic composition and calculated equilibrium temperatures of formation for quartz from the transition zone and dike section of DSDP Hole 504B. https://doi.org/10.1594/PANGAEA.713296
  4. Alt, JC; Muehlenbachs, K; Honnorez, JJ (1986): (Table 3) Oxygen isotopic composition and calculated equilibrium temperatures of formation of quartz-epidote pairs from DSDP Hole 504B. https://doi.org/10.1594/PANGAEA.713294
  5. Alt, JC; Muehlenbachs, K; Honnorez, JJ (1986): (Table 1) Oxygen and carbon isotopic composition of secondary minerals from DSDP Hole 504B. https://doi.org/10.1594/PANGAEA.713289