tholeítico

Tholeiitic refers to a common type of volcanic rock, specifically a basalt. It is characterized by a relatively low alkali content and a specific mineralogy, typically containing plagioclase feldspar and pyroxene. Olivine may or may not be present, and when it is, it is generally less abundant than in its alkaline counterparts. Tholeiitic basalts are formed from the partial melting of the Earth's upper mantle under conditions of low pressure and relatively low water content.

This type of magma is generated in various tectonic settings, most notably at mid-ocean ridges where seafloor spreading occurs, and in large igneous provinces. They are also found in continental rift zones and some hot spot volcanoes. The composition of tholeiitic magma is considered to be primitive, meaning it has undergone little alteration or differentiation since its formation. This makes tholeiitic rocks important for understanding the composition and processes of the Earth's mantle.

The term "tholeiitic" is derived from Tholey, a town in Germany where such rocks were first extensively studied. The classification of basalts into tholeiitic and alkaline series is a fundamental concept in igneous petrology, helping geologists interpret the tectonic environment and mantle source from which these rocks originated. Their widespread occurrence and relatively simple composition make them a key subject in the study of volcanism and plate tectonics.