Large Igneous Provinces

Large igneous provinces (LIPs) are massive crustal emplacements of predominantly Fe- and Mg-rich (mafic) rock that form by processes other than normal seafloor spreading. LIP rocks are readily distinguishable from the products of the two other major types of magmatism, mid-ocean ridge and arc, on the Earth's surface on the basis of petrologic, geochemical, geochronologic, geophysical, and physical volcanological data. LIPs occur on both the continents and oceans, and include continental flood basalts, volcanic passive margins, oceanic plateaus, submarine ridges, seamounts, and ocean basin flood basalts. LIPs and hot spots are commonly attributed to decompression melting of hot, low density mantle material known as mantle plumes. This type of magmatism currently represents ∼ 10% of the mass and energy flux from the Earth's deep interior to its crust. The flux may have been higher in the past, but is episodic over geological time, in contrast to the relatively steady-state activity at seafloor spreading centers. Such episodicity reveals dynamic, non-steady-state circulation within the Earth's mantle, and suggests a strong potential for LIP emplacements to contribute to, if not instigate, major environmental changes.