Mafic Rocks

This video talks about mafic igneous rocks and their metamorphic equivalents. Mafic igneous rocks are low in silicon low in potassium and aluminum. These are Felsic elements that give rise to Felsic minerals like quartz and potassium feldspar. Mafic igneous and metamorphic rocks are high in iron and high in calcium and high in magnesium. These elements are Masic elements and they give rise to mafic minerals like Pyroxene Hornblend and calcium rich feldspar. Here is a list of mafic igneous rocks. Gabbro, diabase, basalt, and mafic Tuff. All of these mafic igneous rocks have similar minerals such as Pyroxene, Hornblende, and calcium rich Feldspar. When basalt ocean crust is metamorphosed and pushed up on land it becomes Metabasalt. When the basalt is pushed up on land a lot of hot water is mixed with it and reverse metamorphism also called retrograde metamorphism occurs. This process causes metamorphism to go in reverse and the dark minerals like Pyroxene reversed to intermediate minerals like biotite and chlorite Take on a shiny schisted appearance with the greenish color of chlorite often dominating. for this reason ocean crust Metabasalt is often called green schist. When gabbro and diorite end on land basalt lava flows are metamorphosed they become a metamorphic rock called amphibolite. Amphibolite often has a hard crystalline texture that is E that is difficult to crack. Amphibolite is usually found in the field as rounded pods that exhibit onion skin type weathering also called spheroidal weathering pattern. when may fake tuff comes out of a volcano it settles down on the ground and is rapidly weathered due to its high iron content. Iron is one of the most easily weathered elements. For this reason Maphet tough can appear as reddish dirt clods often with a dark center or core.