Since the start of the Mesozoic Era about 230 million years ago, large volumes of tholeiite basalt have been erupted through fissures on all of the continents. In several cases, the extrusion of these lavas occurred in conjunction with the break-up of the supercontinents of Gondwana and Pangea. Therefore, these basalt plateaus are now situated on the passive margins of the present continents on opposite sides of ocean basins that have opened between them. Typical examples of this phenomenon are the complementary basalts of Scotland and Greenland, as well as the basalt plateaus in Namibia (southwest Africa) and in the state of Paraná (Brazil). Fissures can also form in back-arc basins behind subduction zones located off the continental coast, causing basalt magma to form by decompression melting of lithospheric mantle. The standard model of flood-basalt petrogenesis developed by White and McKenzie (1989) and by McKenzie and Bickle (1988) is based on the conclusion that flood basalts are erupted thorough continental rifts caused by the interaction of asthenospheric plumes with the lithospheric mantle and with the overlying continental crust (Milanovskiy 1976). The arrival of an asthenospheric plume at the base of the continental lithosphere causes extension and rifting before large-scale decompression melting in the head of the plume can occur (Kent et al. 1992a).
KeywordsLithospheric Mantle Flood Basalt Snake River Plain Benue Trough Skaergaard Intrusion
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