Petrologic character of the Atlantic crust from DSDP and IPOD drill sites

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doi: 10.1029/ME002p0273
Author(s): Bryan, W.; Thompson, G.; Frey, F.
Author Affiliation(s): Primary:
Woods Hole Oceanogr. Inst., Woods Hole, Mass., United States
Volume Title: Deep drilling results in the Atlantic Ocean; ocean crust
Volume Author(s): Talwani, M., editor; Harrison, C. G.; Hayes, D. E.
Source: Maurice Ewing Series, 2, p.273-284; Deep drilling results in the Atlantic Ocean; ocean crust, Harriman, N.Y., March 19-25, 1978, edited by M. Talwani, C. G. Harrison and D. E. Hayes. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0197-6346. ISBN: 978-1-118-66623-4 CODEN: MEWSDN
Note: In English. 42 refs.; illus. incl. table, sketch map
Summary: Basement rocks recovered by DSDP and IPOD drilling in the Atlantic are predominantly pillowed or massive basalt lava flows which resemble modern Mid-Atlantic Ridge (MAR) basalts in their range of chemical composition and petrographic characteristics. Basalts from the oldest sites drilled (70-150 m.y.) generally resemble modern basalts presently being erupted at the locations on the MAR where these older basalts should have originated; all of these represent "normal" ridge segments unaffected by "mantle plume" activity. The Leg 37 transect drilled opposite the Azores "mantle plume" or "blob" shows evidence of some fluctuation in geochemical parameters, possibly indicating short-term fluctuations in plume activity. Only two sites (334 and 395) have penetrated layer 3 plutonic rocks, but it is likely that these are tectonically emplaced, and the true thickness of layer 2 has not been defined by drilling. In general, the transition from sediment to basalt basement is sharp. Excellent core recovery at Sites 417 and 418 shows that pillowed and massive flows are interbedded; dikes and sills are rare at these and other sites, but probably are hard to recognize unless core recovery is very good. Drilling at Site 417 suggests that intense low temperature alteration may be limited to topographic highs which are not immediately buried by sediment. Hydrothermal alteration and metamorphism are not encountered in the sites so far drilled. Most DSDP and IPOD sites have not been well-placed to indicate the persistence of "mantle plumes" with time, although north-south geochemical variations in continental triassic basalts resemble those documented for modern basalts associated with the Azores plume and suggest that such plumes may have initiated spreading in the Atlantic. Future drilling should be designed to define the persistence of such plumes in time and space, and also should attempt to penetrate the lower part of layer 2 and the upper part of layer 3 in a crustal section of normal thickness. Abstract Copyright 1979 by the American Geophysical Union.
Year of Publication: 1979
Research Program: DSDP Deep Sea Drilling Project
Key Words: 05 Petrology, Igneous and Metamorphic; Atlantic Ocean; Basalts; Chemical composition; Composition; Crust; Deep Sea Drilling Project; Geochemistry; Hot spots; Igneous rocks; Mantle plumes; Marine geology; Mid-Atlantic Ridge; Ocean floors; Oceanography; Petrology; Plate tectonics; Stratigraphy; Structural geology; Structure; Volcanic rocks
Record ID: 1980017790
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.

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