Ore deposits associated with flood basalt volcanism
Flood basalt volcanism is a feature of the later stages of the Earth’s evolution, beginning in the mid to late Proterozoic. Specific episodes are characterized by the immense areas that they cover (commonly hundreds of thousands km2) and the short duration of the magmatic activity (up to 15 My in the Proterozoic and, typically, 1–2 My in the Phanerozoic). Lava facies dominate over explosive and intrusive facies and uniform tholeiitic basalts predominate among the rock types. The flood basalt provinces are typically, but not universally, equant in shape. These eruptions represent the most catastrophic igneous events in the Phanerozoic history of the earth. The magmatism occurred both in oceanic and continental environments. Oceanic flood-basalt provinces can be much more extensive than continental provinces. The largest oceanic province (the Outang-Java plateau) comprises over 60 millions km3 (Mahoney and Coffin, eds 1997) while the largest continental province (the Siberian trap) comprises about 4 millions km3 (Masaitis 1983) (see Fig. 4.1). However continental flood-basalt events had the greater effect on geological history because they resulted in ecological catastrophes that brought with them major mass extinctions. The Siberian trap define the biostratigraphic boundary between the Paleozoic and Mesozoic (Czamanske et al. 1998 and their references), the Karoo-Ferrar between the Lower and Middle Jurassic (Duncan et al. 1997), and the Deccan — between the Mesozoic and Cenozoic (e.g. Courtillot et al., 1986, 1988).
KeywordsMassive Sulfide Flood Basalt Sulfide Liquid Olivine Gabbro Duluth Complex
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