Rift areas

Areally close compositional contrast is seen in the recent rift area of Djibouti. On the western border, the terminal Lake Abhe is fed by the sodium-carbonate-type Awash River from the Ethiopian volcanic highlands, whereas the Asal Lake near an arm of the Gulf of Aden is fed by seawater through recent fault zones and hydrothermal inputs in addition to local runoff, and precipitates halite and gypsum (Fontes et al., 1979). 

Initial heat flow, Q, is estimated from the present-day values of surface heat flow in the regions with tectonic settings similar to that expected for the time of the basin initiation. For example, Q s 100-110 mW m" is typical of continental rift areas (Baikal Lake, African rift system) however, on rift shoulders, Q can be nearly 65-85 mW (Smirnov 1980). Estimations of the initial heat flow can be adjusted by analysis of variations in tectonic subsidence of the basement (see following sections). In the case of the Oued el-Mya Basin, Q is approximately 52 mW m" (Fig. 6.5). 

The Red Sea vent s metal content is similar to many other deep ocean vents, with quite high strontium values. Pushkina et al. (1982) also commented on the amounts of Ba, Cu, Fe, Mn, Ni, Pb and Zn in the brine, while Manheim (1974) in addition noted the presence of elevated amounts of As, Co, Se, U and perhaps F. Older vents in the same rift area appear to have formed Fe—Mn—Ba, Pb—Zn, and Pb—Zn—Cu— Ba deposits along the Red Sea far to the north and south of the current vents (Figs. 2.13 and 2.14). The sea floor Late Miocene shale-anhydrite breccia just south of the vents contains about 5% Zn. At the vents, the rocks contain 14—21% Fe, 0.8% Zn, 0.6-0.8% Cu and 0.5-0.7% Pb. Based upon marine sediments and the presence of several deposits of this type, it appears that the Red Sea once filled the adjacent Afar (Danakil) Depression clear to the Ethiopian Plateau (Fig. 2.13 Manheim, 1974 Bonatti et al, 1972). 

The features created by crustal movements may be mountain chains, like the Himalayas, where collision of continents causes extensive compression. Conversely, the depressions of the Red Sea and East African Rift Basin are formed by extensional plate movements. Both type of movements form large scale depressions into which sediments from the surrounding elevated areas ( highs ) are transported. These depressions are termed sedimentary basins (Fig. 2.3). The basin fill can attain a thickness of several kilometres. 

Several different hypotheses on the tectonic setting of the Kuroko mine area have been proposed. They include volcanic front of island arc (T. Sato, 1974 Horikoshi, 1975a), rifting of island arc (Cathles, 1983a), back-arc depression (Fujioka, 1983 Uyeda, 1983), and back-arc basin. 

Rift Valley fever is characterized by high fever and the development of hemorrhagic areas under the skin. Only a small number of cases (<1%) go on to develop the more serious viral hemorrhagic fever syndrome that causes death in 50% of those who manifest this syndrome. The syndrome is associated with mucosal bleeding or hemorrhaging, liver and kidney failure, and shock before death. Some infections can be complicated with encephalitis and a variety of ocular defects.3... 

Carbonatites. Carbonatites are igneous mixtures of essentially carbonate minerals found in the form of intrusions and lavas, associated with highly undersaturated alkali igneous complexes along major rift zones, cutting old stable continental shield areas. 

Many reports (78-84) investigated the differences in packed and capillary supercritical fluid chromatography. Unfortunately, the rift between packed and capillary column users of SFC impeded the development of the science. This rift is a likely cause of the current low interest in SFC. Ideally, the unique features of the mobile phase is the area of scientific exploration that should be exploited. Choice of column size or type should be dependent upon the analytical problem to be solved. 

The Intra-Apennine area was affected by late Triassic to Jurassic rifting, with sedimentation of both complete and reduced successions inside progressively deepening extensional basins. Starting in Cretaceous time,... 

The catalyst particles are built of crystallites, the interior of which is extremely pure iron, whereas the surface layers have a high content of promoter atoms. The total crystallite surface area as will be discussed later, is some two to three times greater than that found by low-temperature surface area measurements by the BET-method. It is concluded that interfacial layers join the crystallites, and only where the distance between two crystallites is too great or their orientation too divergent is the interfacial layer split up into two separate surface layers, thus producing a rift network through the catalyst particles. It is through this rift network that the inner surface is reached by the reactants, and this inner surface is utilized as effectively as is the outer surface. 

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