Rift systems

Figure 1.164. Distribution of Cenozoic basalts and active rift systems in the northeast China region. Arrows indicate the horizontal convective current in the upper mantle associated with the upwelling of the asthenosphere beneath the region. A Baikal Rift B Shanxi Graben C Tancheng-Lujiang Fault D Okinawa Trough (Tatsumi et al., 1990).

INTRA-PLATE VOLCANISM BACKARC VOLCANIC CONTINENTAL RIFT SYSTEM BASIN BASIN... 

Voggenreiter W., Hoetzl H., and Mechie J. (1988) Low-angle detachment origin for the Red Sea Rift system Tectonophysics 150, 51-75. 

Zipfel J. and Worner G. (1992) Thermobarometry on four- and five-phase periodotites from a continental rift system evidence for upper mantle uphft and coohng at the Ross Sea margin (Antartica). Contrib. Mineral. Petrol. Ill, 24-36. 

Extensive volcanism can be found in eastern Africa associated with the East African rift system. Helium isotope ratios measured in basalts from the Ethiopian Rift Valley and Afar, near the triple junction of Red Sea, Aden, and Ethiopian rift systems, are 6-17/ a (Marty et al., 1993, 1996 Scarsi and Craig, 1996). These values include MORB ratios as well as indications of both contributions from radiogenic He and high He/ He hotspots. To the south, the rift system divides into eastern and western branches. Xenoliths from Tanzanian vents in the eastern branch... 

Furman T. and Graham D. W. (1999) Erosion of lithospheric mantle beneath the East African rift system geochemical evidence from the Kivu volcanic province. Lithos 48, 237-262. 

Yin A. and Kelly T. K. (2000) An elastic wedge model for the development of coeval normal and thrust faulting in the Manna Loa-Kilauea rift system in Hawaii. J. Geophys. Res. Solid Earth 105, 25909-25925. 

Grove A. T. (1986) Geomorphology of the African rift system. Sedimentation in the African Rifts. Special Publication 25, (eds. L. E. Frostick, R. W. Renaut, I. Reid and J. J. Tiercelin). Geological Society, London, pp. 9-18. 

Mid-oceanic ridge-rift systems are areas in the oceans where the edges of two plates, and any continents that may be on them, are being forced away from each other by currents in the underlying asthenosphere. Magma from the asthenosphere is pushed up from below the rift to fill in the void created by spreading and to create new ocean floor. 

Fig. 3. Location of Tanzania Craton (Archaean), Oligocene-Recent Red Sea and Gulf of Aden rifts, and Miocene-Recent Ethiopian, Western and Eastern rift systems (after Ebinger et at. 1999). Dark shading encloses elevations above 1000 m lighter shading shows Late Eocene-Recent volcanic provinces. Hexagons mark the assumed path of the African plate over a mantle plume (from George et at. 1998). A, locations of Cenozoic kimberlites and carbonatites. MER, Main Ethiopian rift.

We tested the sensitivity of the splitting to the scaling adopted. The orientation of the shear-wave polarizations will remain consistent, but the magnitude of the splitting could vary. What the modelling provides is a prediction of the pattern in splitting that should be observed around the edges of the keel. The results from seismic studies under way in the East African rift system (Nyblade, pers. comm. Stuart, pers. 

Behrendt, j. C., Green, A. G., Cannon, W. F. 5 OTHERS 1988. Crustal strueture of the Midcontinent rift system results from GLIMPCE deep seismic reflection profiles. Geology, 16, 81-85. 

The Mesoproterozoic Midcontinent Rift System, Lake Superior region, USA. Sedimentary Geology, 141-142, 421-442. 

Syrian—African rift system, many thermo-mineral springs emerge. A large... 

The inflow of meteoric water into the aquifers saturated by the formation water was made possible only when an outlet was formed for the formation water to be pushed out. This may have started in the Neogene when transversal faulting occurred, but certainly took place during the Pleistocene after the down-faulting of the Syrian—African rift system. 

Modern monochromators consist of a rift system, the optics and the infrared radiation splitting system, which is usually presented by prism or diffraction grid. The following two types of monochromators are most popular in modern infrared spectrometers ... 

Delaney, J.R., Johnson, H.P. and Karsten, J.L., 1981. The Juan de Fuca Ridge-hot spot-propagating rift system. Journal of geophysical Research, 86 11747-11750. 

Furman T, Graham DW (1999) Erosion of lithospheric mantle beneath the East African Rift system geochemical evidence from the Kivu volcanic province. Lithos 48 237-262 Gasparon M, Hilton DR (1994) Crustal contamination processes traced by helium isotopes examples from the Sunda Arc, Indonesia. Earth Planet Sci Lett 126 15-22 Goes S, Spakman W., Bijwaard H (1999) A lower mantle source for central European volcanism. Science 286 1928-1931... 

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). 

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