Tectonic structure and petrology of the Antarctic plate boundary near the Bouvet triple junction |
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Authors: | JG Sclater H Dick IO Norton D Woodroffe |
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Institution: | 1. Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 U.S.A.;2. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 U.S.A.;3. Lamont-Doherty Geological Observatory, Palisades, NY 10964 U.S.A. |
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Abstract: | An en echelon suite of four fracture zones, trending approximately N40°E, has been discovered during a survey of the Southwest Indian Ocean Ridge between Bouvet Island and 14°E. The largest of these fracture zones, the Islas Orcadas and Shaka, are less than 30 km wide, have more than 3 km of vertical relief, and are respectively 100 and 200 km in length. The morphology of these and the Bouvet and Prince Edward fracture zones have been used to compute a pole for the relative motion between Africa and Antarctica. This pole, at 4°S and 32°W, is within the range of previously computed pole positions.Ridge basalts were dredged at three separate locations: at the Conrad fracture zone near 55°40′S and 3°51′W, at the Islas Orcadas fracture zone near 54°5′S and 6°4′E, and at the ridge crest near 11°E. In addition, samples from a probable upper mantle intrusion were recovered from one wall of the Islas Orcadas fracture zone. The opposite wall was very different consisting entirely of normal mid-ocean ridge basalt. |
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