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Staudigel, Hubert; Hart, Stanley R; Richardson, Stephen H (1981): Geochemistry of oceanic crust of the North Atlantic [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.708682, Supplement to: Staudigel, H et al. (1981): Alteration of the oceanic crust: processes and timing. Earth and Planetary Science Letters, 52(2), 311-327, https://doi.org/10.1016/0012-821X(81)90186-2

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Abstract:
87Sr/a6Sr ratios, Sr, K, Rb and Cs contents and the petrology of basalts and secondary phases recovered from deep basement drilling at DSDP Sites 332B, 417A, 417D and 418A show that the oceanic crust alters in four distinct stages characterized by formation of palagonite, smectite and calcite (Stages I, II and III, respectively). Stage IV represents the final compaction of the crust, including a dehydration of the crust without major chemical changes. Isotopic age determinations by Hart and Staudigel (1978, doi:10.1029/GL005i012p01009) and Richardson et al. (doi:10.1029/JB085iB12p07195), show that, at least for Atlantic-type crustal regimes, Stage I and II last for a maximum of 3 m.y., and Stage III lasts beyond Stage I and II, but is probably completed in significantly less than 10 m.y. Stage IV is long-lived and may still be active at 100 m.y. Stages I and II, the phase of halmyrolysis, include geochemically significant interactions between seawater and basalt for the upper 500 m of layer II and involve volumes of seawater containing a large basaltic component. Stage III solutions show evidence of less seawater-basalt interaction, at least to depths of 500 m; calcites deposited from these solutions have Sr isotopic ratios close to seawater values; but also have very low Sr/Ca ratios indicating a large basalt Ca component in the solutions.
Smectite formation is the result of the interaction of seawater and basalt. The initial 87Sr/a6Sr ratios of smectites represent the Sr isotopic composition of the solution when the smectite is being formed. Thereafter, alkalies may be continuously added to interlayer positions in the smectite in order of decreasing hydration energy (Cs is more enriched than Rb, Rb more than K). The later-formed carbonates have very low alkali concentrations, and 87Sr/86Sr ratios identical to contemporaneous seawater. Therefore, since the alkali concentrations in a whole rock sample are affected by different alteration processes, the alkali concentrations alone are not reliable indicators of the degree of alteration.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 25.072833 * Median Longitude: -68.049758 * South-bound Latitude: 25.035000 * West-bound Longitude: -68.057300 * North-bound Latitude: 25.111500 * East-bound Longitude: -68.041300
Date/Time Start: 1976-12-02T00:00:00 * Date/Time End: 1977-02-10T00:00:00
Event(s):
51-417A * Latitude: 25.110500 * Longitude: -68.041300 * Date/Time: 1976-12-02T00:00:00 * Elevation: -5468.0 m * Penetration: 417 m * Recovery: 250.4 m * Location: North Atlantic/CONT RISE * Campaign: Leg51 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 43 cores; 389.1 m cored; 27.8 m drilled; 64.4 % recovery
51-417D * Latitude: 25.111500 * Longitude: -68.046800 * Date/Time: 1976-12-02T00:00:00 * Elevation: -5482.0 m * Penetration: 532.5 m * Recovery: 202.6 m * Location: North Atlantic/CONT RISE * Campaign: Leg51 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 43 cores; 508.6 m cored; 30.4 m drilled; 39.8 % recovery
52-418A * Latitude: 25.035000 * Longitude: -68.057300 * Date/Time: 1977-02-10T00:00:00 * Elevation: -5511.0 m * Penetration: 570.5 m * Recovery: 205.5 m * Location: North Atlantic/CONT RISE * Campaign: Leg52 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 48 cores; 374 m cored; 0 m drilled; 54.9 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
6 datasets

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Datasets listed in this publication series

  1. Staudigel, H; Hart, SR; Richardson, SH (1981): (Table 3) K and Cs of carbonates from DSDP Hole 51-417A. https://doi.org/10.1594/PANGAEA.708678
  2. Staudigel, H; Hart, SR; Richardson, SH (1981): (Table 2) K and Cs contents of smectites and analcites from DSDP Hole 51-417A. https://doi.org/10.1594/PANGAEA.708676
  3. Staudigel, H; Hart, SR; Richardson, SH (1981): (Table 1) K, Rb, Cs, Sr contents and 87Sr/86Sr ratios of whole rocks from DSDP Site 51-417. https://doi.org/10.1594/PANGAEA.708673
  4. Staudigel, H; Hart, SR; Richardson, SH (1981): (Table 3) K and Cs of carbonates from DSDP Hole 52-418A. https://doi.org/10.1594/PANGAEA.708680
  5. Staudigel, H; Hart, SR; Richardson, SH (1981): (Table 2) K and Cs contents of smectites and analcites from DSDP Hole 52-418A. https://doi.org/10.1594/PANGAEA.708677
  6. Staudigel, H; Hart, SR; Richardson, SH (1981): (Table 1) K, Rb, Cs, Sr contents and 87Sr/86Sr ratios of whole rocks from DSDP Hole 52-418A. https://doi.org/10.1594/PANGAEA.708675