tholeiitic basalt

Tholeiitic basalt is a fine-grained, extrusive igneous rock, a type of basalt. It is characterized by the presence of plagioclase feldspar (labradorite), clinopyroxene (augite with pigeonite), and iron ore (magnetite and ilmenite). Tholeiitic lavas typically contain glass but little to no olivine.1

This type of basalt is found in extensive plateaus, such as those in the Pacific Northwest and the Deccan region of western India, as well as in lava flows in the Lake Superior region, South Africa, Western Australia, and South America. Tholeiitic basalts are subalkaline and are commonly found at divergent plate boundaries, forming mid-ocean-ridge basalt (MORB). MORB is the most abundant rock on Earth's surface and is generated from a mantle depleted of volatile elements. Tholeiitic basalts are also erupted by active volcanoes in Hawaii, like Mauna Loa and Kilauea.123