Structural Effects of Sea-floor Spreading in the Gulf of Aden and the Red Sea on the Arabian Shield

Author(s):  
Peter J. Burek
1990 ◽  
Vol 127 (4) ◽  
pp. 309-318 ◽  
Author(s):  
D. I. J. Mallick ◽  
I. G. Gass ◽  
K. G. Cox ◽  
B. V. W. De Vries ◽  
A. G. Tindle

AbstractPerim Island is an eroded fragment of the southwest flank of a late Miocene (10.5 ± 1.0 Ma) volcano whose centre lay on the southwesternmost tip of Arabia. The volcano is the westernmost of the E–W line of six central vent volcanoes (the Aden Line) that extends 200 km along the south coast of Arabia from Perim to Aden. Major oxide and trace element abundances are given for 35 Perim specimens and these show that the volcano has within-plate trace element characteristics and consists of a petrographically and geochemically simple suite of alumina-poor olivine basalts, andesites, and transitional andesite–trachyandesites. Six specimens, however, are markedly enriched in Al2O3 and CaO, and contain abundant (20–30 mode %) highly calcic (An77–83) plagioclase phenocrysts. Geochemical modelling suggests that the main Perim volcanic sequence was produced by the fractional crystallization (o1 + cpx + Ti-mt + plag) of a silica saturated (SiO2 c. 45%) basic melt. The high A1, high Ca, magmas appear to be mixing products of plagioclase-enriched basic magmas with more evolved melts. Perim is the oldest volcano of the Aden line, which becomes increasingly younger and alkalic eastward. It is suggested that the volcanism is related to an eastwards-propagating rift produced before the most recent stage of sea-floor spreading in the Gulf of Aden (4.5 Ma–present).


The Red Sea Discussion Meeting originated in the desire of the other organizers to bring together as many as possible of the earth scientists who have been working recently in that area to examine the latest evidence and ideas on its structure and origin, to see how they accord with modern continental and sea-floor spreading concepts. The Red Sea, Gulf of Aden and Afar crustal depressions, now known to be continuous with the extension of the world ocean rift system, have been claimed as a manifestation of crustal separation, but some Earth scientists still consider that the evidence can be explained by less drastic crustal rifting. Definite solutions to the many outstanding problems were not expected but discussions would clearly assist further researches.


The results of an intensive seismic survey in the Red Sea are presented. Analysis of twenty seismic refraction lines leaves no doubt that much more than just the central trough of the Red Sea is underlain by material with a seismic velocity which is characteristic of oceans. In addition, up to 5 km of what we interpret as evaporites were regularly found. The suggestion that the Red Sea crust could be oceanic in character over the major part of its width is examined in conjunction with magnetic and gravity data. We conclude that there is no evidence against sea floor spreading on a substantial scale in the Miocene. The implications of this in terms of neighbouring features is briefly discussed.


Nature ◽  
1974 ◽  
Vol 247 (5435) ◽  
pp. 7-11 ◽  
Author(s):  
R. W. GIRDLER ◽  
P. STYLES

The seismicity of the Red Sea, Gulf of Aden and Afar triangle has been studied for the period January 1953 through December 1968. Epicentres have been relocated using the method of joint Epicentral Deter­mination (Douglas 1967) and some fault plane solutions have been attempted. Magnitude-frequency studies indicate that with the present distribution of teleseismic stations, earthquakes with body wave magnitude m b ≽ 4.8 are well determined in this region. The study confirms that there is surprisingly little major earthquake activity in the northern part of the Red Sea. Between 19.5 and 21.0° N, there is a concentration of epicentres and some of these might be associated with an active NNE transform fault. In the southern part of the Red Sea, most of the epicentres are associated with the deep, axial trough, although some are associated with the western mar­gin, especially in the neighbourhood of the Gulf of Zula (15° N). Earthquake activity is confined to the centre of the Gulf of Aden with concentrations of epicentres occurring on or near to NNE transform faults. The seismically active zone continues westwards through the Gulf of Tadjoura and across the Afar depression to the western boundary scarp. There are no teleseismically recorded epicentres between latitudes 12.2 and 14.2° N. In general, most of the seismic activity occurs along the centres of the Red Sea and Gulf of Aden and this supports a sea-floor spreading mechanism for their origin. The number of plates involved is discussed.


2014 ◽  
Vol 617 ◽  
pp. 140-149 ◽  
Author(s):  
Khalid A. Almalki ◽  
Peter G. Betts ◽  
Laurent Ailleres

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