Theralite

Theralith (also Theralit ) is the name for a plutonic rock from the group of foidführenden gabbros. The name derives from an occurrence from on the island of Thera in the Aegean Sea. The first description was by Karl Heinrich Rose Bush in 1887.

Mineral composition and rock description

The mineral composition comprises plagioclase ( andesine and labradorite ), more than 10% Foide (mostly nepheline ), augite, olivine, and biotite in small amounts, up to 10% alkali and alkali - amphibole. As an accessory components occur apatite, titanite and sulfidic ore minerals on, but never quartz. With this composition Theralithe belong to the group of gabbroic. The total content of dark minerals less than 30%, the prefix leuco precedes the rock name, at levels above 70%, the prefix Mela. Theralithe are often grainy and have a more granular structure.

Origin and Occurrence

As a strong silicon undersaturated rocks, Theralithe never occur in tectonic active zones such as collisional. They are found predominantly as smaller deposits of deep-seated fault zones or trenches in which material can obtrude from the mantle. In addition to the type locality on the island of Thera is found this rock on the Kola Peninsula and in the transmit- crater in Namibia. In Germany there is a small occurrence in the Upper Rhine Graben at the Kaiser chair.

The volcanic equivalent of Theralits is the basanite.