Geochemical fluxes during seafloor alteration of the basaltic upper oceanic crust; DSDP sites 417 and 418

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doi: 10.1029/GM096p0019
Author(s): Staudigel, Hubert; Plank, Terry; White, Bill; Schmincke, Hans-Ulrich
Author Affiliation(s): Primary:
Free University Amsterdam, Faculty of Earth Sciences, Amsterdam, Netherlands
Other:
University of Kansas, United States
Cornell University, United States
Abteilung Vulkamologie und Petrologie, Geomar Forschungszentrum, Federal Republic of Germany
Volume Title: Subduction top to bottom
Volume Author(s): Bebout, Gray E., editor; Scholl, David W.; Kirby, Stephen H.; Platt, John P.
Source: Subduction top to bottom, edited by Gray E. Bebout, David W. Scholl, Stephen H. Kirby and John P. Platt. Geophysical Monograph, Vol.96, p.19-38. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0065-8448. ISBN: 978-1-118-66457-5 CODEN: GPMGAD
Note: In English with English summary. Includes appendix. 48 refs.; illus., incl. 6 tables, sect.
Summary: Seafloor alteration of the basaltic upper oceanic crust provides one of the major geochemical pathways between the mantle, the ocean/atmosphere and subduction zone regimes. Yet, no reliable mass balances are available, in large part because of the extremely heterogeneous distribution of altered materials in the oceanic crust but also because of the limited availability of high recovery drill cores. In this paper, we document the feasibility of determining the bulk altered and fresh composition of the oceanic crust on a 10-500 m length scale, from a region in the western Atlantic Ocean (DSDP/ODP Sites 417-418). Unaltered compositions were obtained from glass and phenocryst data and altered compositions were determined through analysis of composite samples. Most of the alteration-related chemical inventory resides preferentially in the upper oceanic crust and in highly permeable volcaniclastics. Most major elements (Si, Al, Mg, Ca, and Na) and many trace elements (Sr, Ba, LREE's) experience substantial large scale redistribution, but fluxes are relatively low. Overall, 12 wt % are added to the crust, mostly H2O, CO2, and K, but the distribution varies widely. High field strength elements, Th, Ti and Fe remain essentially immobile during low temperature alteration, while most other elements are affected to some degree. While the total fluxes are relatively small, the re-distribution of alteration-sensitive elements in the ocean crust is much larger, even on length scales exceeding 100m. The bulk composition of the upper 500m at Sites 417/418 can be used to constrain the impact of ocean crust subduction on element recycling to volcanic arcs. Flux balances indicate that the altered domains within the upper basaltic crust may contribute a very large proportion of some element fluxes recycled to the arc (H2O, CO2, K, Rb, U), while other element fluxes require additional contributions from sediments and deeper oceanic crust.
Year of Publication: 1996
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 18 Geophysics, Solid-Earth; Actinides; Alkali metals; Alteration; Atlantic Ocean; Basalts; Carbon dioxide; Crust; DSDP Site 417; DSDP Site 418; Deep Sea Drilling Project; Geochemistry; IPOD; Igneous rocks; Leg 102; Leg 51; Leg 52; Leg 53; Metals; Ocean Drilling Program; Oceanic crust; Plate tectonics; Potassium; Rubidium; Sea water; Subduction; Upper crust; Uranium; Volcanic rocks; West Atlantic
Coordinates: N250000 N250000 W0680000 W0680000
N250205 N250207 W0680326 W0680327
N250205 N250207 W0680326 W0680327
N240000 N260000 W0670000 W0690000
N240000 N260000 W0670000 W0690000
N240000 N260000 W0670000 W0690000
Record ID: 1997021961
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