Tectonics of an incipient oceanic rift |
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| Authors: | P Choukroune J Francheteau B Auvray J M Auzende J P Brun B Sichler F Arthaud J C Lepine |
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| Institution: | (1) CAESS, Université de Rennes I, Campus de Beaulieu, 35042 Rennes Cedex, France;(2) IPGP, Université de Paris 7, 75230 Paris Cedex, France;(3) IFREMER. COB, 29273 Brest Cedex, France;(4) USTL. Université de Montpellier, 34060 Montpellier Cedex, France |
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| Abstract: | The results of 26 dives with the diving saucer Cyana in the Gulf of Tadjoura and Ghoubbet al Kharab (Republic of Djibouti) are presented. One can demonstrate that the sites of recent volcanism, tectonics and hydrothermal activity within the axial part of the Gulf of Tadjoura coincide with topographic highs trending at a high angle (azimuth 135°) with respect to the average trend of the axial trough of the Gulf (azimuth 080°). The highs owe their relief to both volcanism and normal faulting along a trend of 130–140°. Recent faulting on the bounding walls of the axial trough is also found along a trend of 130–140° where the faults interfere with another set of apparently older faults trending 070° parallel to the axial trough. Spacing between the active zones of the Gulf is regular and about 30 km. No evidence for transform faulting has been found, in contradiction to all previous kinematic models of the Gulf of Tadjoura. There is evidence that the presently active phase of opening associated with 130–140° faults is less than 0.7 my old and that there was an older phase associated with 070°–080° faults creating the main trough of the Gulf. The basaltic lavas created during the two phases have evolved from transitional to tholeiitic. |
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| Keywords: | Gulf of Tadjoura submersible oceanic rift tectonics |
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