Alt, Jeffrey C; Emmermann, Rolf (1985): Geochemistry and fluxes at DSDP Hole 83-504B [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.804967, Supplement to: Alt, JC; Emmermann, R (1985): Geochemistry of hydrothermally altered basalts: Deep Sea Drilling Project Hole 504B, Leg 83. 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, 249-262, https://doi.org/10.2973/dsdp.proc.83.109.1985
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Abstract:
This chapter documents the chemical changes produced by hydrothermal alteration of basalts drilled on Leg 83, in Hole 504B. It interprets these chemical changes in terms of mineralogical changes and alteration processes and discusses implications for geochemical cycling.
Alteration of Leg 83 basalts is characterized by nonequilibrium and is heterogeneous on a scale of centimeters to tens or hundreds of meters. The basalts exhibit trends toward losses of SiO2, CaO, TiO2; decreases in density; gains of MnO, Na2O, CO2, H2O+ , S; slight gains of MgO; increased oxidation of Fe; and variable changes in A12O3. Some mobility of rare earth elements (REE) also occurred, especially the light REE and Eu. The basalts have lost Ca in excess of Mg + Na gains. Variations in chemical trends are due to differing water/rock ratios, substrate control of secondary mineralogy, and superimposition of greenschist and zeolite facies mineralogies. Zeolitization resulted in uptake of Ca and H2O and losses of Si, Al, and Na. These effects are different from the Na uptake observed in other altered basalts from the seafloor attributed to the zeolite facies and are probably due to higher temperatures of alteration of Leg 83 basalts.
Basalts from the transition zone are enriched in Mn, S, and CO2 relative to the pillow and dike sections and contain a metal-sulfide-rich stockwork zone, suggesting that they once were located within or near a hydrothermal upflow zone. Samples from the bottom of the dike section are extensively fractured and recrystallized indicating that alteration was significantly affected by local variations in permeability.
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:
3 datasets
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Datasets listed in this publication series
- Alt, JC; Emmermann, R (1985): (Table 4) Geochemical fluxes at DSDP Hole 83-504B. https://doi.org/10.1594/PANGAEA.804953
- Alt, JC; Emmermann, R (1985): (Table 2) Geochemistry of selected samples at DSDP Hole 83-504B. https://doi.org/10.1594/PANGAEA.804952
- Alt, JC; Emmermann, R (1985): (Table 1) Geochemistry of altered basalt at DSDP Hole 83-504B. https://doi.org/10.1594/PANGAEA.804951