Gabrodes

Gabrodes are a group of igneous rocks belonging to the ultramafic class. They are characterized by their coarse grain size and their composition, which is primarily dominated by olivine and pyroxene. Unlike basalt, which has a similar mineralogical composition but is fine-grained, gabrodes are phaneritic, meaning their crystals are visible to the naked eye. This coarse texture indicates that the magma from which they formed cooled slowly, typically deep within the Earth's crust.

The specific mineral proportions within gabrodes can vary, leading to different sub-classifications. For instance, olivine-rich varieties are known as lherzolite, while those with a higher pyroxene content are called harzburgite. If both olivine and pyroxene are present in significant amounts, along with a small percentage of plagioclase feldspar, the rock may be classified as pyroxenite or dunite, depending on the dominant mineral.

Gabrodes are significant components of the Earth's upper mantle. They are often found in ophiolite complexes, which are remnants of oceanic crust and upper mantle that have been thrust onto continental crust. They can also occur in layered intrusions, where distinct layers of different rock compositions form as magma cools and crystallizes over time. The study of gabrodes provides valuable insights into the composition and processes occurring within the Earth's mantle.