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Staudigel, Hubert; Davies, Gareth R; Hart, Stanley R; Marchant, K M; Smith, Brian M (1995): Chemical and isotope compositions of rocks from altered ocean crust at DSDP/ODP Sites 417/418 [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.704936, Supplement to: Staudigel, H et al. (1995): Large scale isotopic Sr, Nd and O isotopic anatomy of altered oceanic crust: DSDP/ODP sites 417/418. Earth and Planetary Science Letters, 130(1-4), 169-185, https://doi.org/10.1016/0012-821X(94)00263-X

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Abstract:
Large-scale compositional domains at DSDP/ODP drill sites 417A, 417D and 418A were analyzed for O, Sr and Nd isotope ratios, and REE, U, K, Rb and Sr abundances, to constrain the bulk chemical composition of the oceanic crust that is recycled at subduction zones. The combination of the three sites gives the composition of the upper oceanic crust in this region over a distance of about 8 km. The d18O(SMOW) and 87Sr/86Sr(meas) of compositional domains 10-100 m in size correlate well, with a range of 7.7-19.2 and 0.70364-0.70744, and mean of 9.96 and 0.70475, respectively. The Rb inventory of the upper crust increases by about an order of magnitude, while Sr contents remain constant. U abundances increase moderately under oxidizing alteration conditions and nearly triple in the commonly reducing alteration environments of the upper oceanic crust. REEs are influenced by alteration only to a small extent, and recycled oceanic crust is similar to MORB with respect to 143Nd/144Nd. Even though the average composition of the upper oceanic crust is well defined, the large scale composition varies widely. Highly altered compositional domains may not have a large impact on the average composition of the oceanic crust, but they may preferentially contribute to fluids or partial melts derived from the crust by prograde metamorphic reactions.
Project(s):
Coverage:
Median Latitude: 25.085667 * Median Longitude: -68.048467 * 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
Size:
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