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Comparison of Geologic and Seismic Structure of Uppermost Fast-Spreading Oceanic Crust: Insights From a Crustal Cross-Section at the Hess Deep Rift

Chapter

Abstract

Based on studies of ophiolites (Moores and Vine, 1971; Casey and Karson, 1981; Lippard et al., 1986; Nicolas, 1989) and limited deep drilling (Becker et al., 1988; Alt et al., 1993), the uppermost 2 km of oceanic crust created at fast-to intermediate-rate (>50 mm/yr, full spreading rate) mid-ocean ridge spreading centers is generally considered to consist of a series of laterally continuous geologic units. The upper unit includes basaltic lavas mostly with pillow and lobate morphologies with lesser tabular sheet flows. The lavas are underlain by a “sheeted dike complex” composed of side-byside, vertical, tabular, basaltic intrusions. Dikes are ~1 m wide and represent incremental spreading events accommodated by the injection of basaltic magma from an underlying magma body (Delaney et al., 1998). Slowly crystallizing magma beneath the sheeted dike complex forms coarse-grained gabbroic rocks that constitute the bulk of oceanic crust (Sinton and Detrick, 1992). Thus, the basaltic lavas and sheeted dikes represent a relatively fine-grained, intrusive/extrusive carapace that overlies an axial magma chamber or its products. These rock units form the basis for the interpretation of the geology and geophysics of oceanic crust and, by inference, processes beneath mid-ocean ridge spreading centers.

Keywords

Oceanic Crust Basaltic Lava Ocean Drill Program Gabbroic Rock East Pacific Rise 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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© Springer Science+Business Media New York 2003

Authors and Affiliations

  1. 1.Division of Earth and Ocean SciencesDuke UniversityDurhamUSA
  2. 2.Institute for GeophysicsUniversity of Texas at AustinAustinUSA

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