Final answer:
Large igneous provinces are primarily composed of basaltic magma, which is related to mafic magma and forms the oceanic crust. Such magma leads to basalt lava flows when extruded, and forms intrusive rocks like gabbro when cooled at depth.
Step-by-step explanation:
The great sheets or floods of magma that are extruded to form large igneous provinces tend to have a basaltic composition. This is because basaltic magma, which creates the oceanic crust, is characteristic of mafic magma eruptions that occur on the seafloor, leading to the formation of basalt lava flows or the cooling at depth to create intrusive igneous rock like gabbro.
As the magma extrudes onto the surface it cools relatively quickly, forming fine-grained extrusive igneous rock. In contrast, granitic, andesitic, and ultramafic rocks are associated with different cooling rates and magma compositions. Continental crust, for example, which consists predominantly of igneous, metamorphic, and sedimentary rocks, typically has a granitic composition and is less dense than the mafic rocks of the oceanic crust.