diabase
/ˈdʌɪəbeɪs
/noun Geology
Another term for dolerite.It is also a widespread constituent of a variety of igneous and metamorphic rocks and is occasionally found in pegmatites and in related veins marginal to igneous rock units ranging from granite to diabase....
- The lower series consists of alternating basalt lava, tuff breccia, tufite, and siliceous rock, whereas the upper one is dominated by diabase.
- Many such dikes in western Maine are classified as alkali diabase.
Origin
Mid 19th century (originally denoting diorite): from French, formed irregularly as if from di- 'two' + base 'base' (thus 'rock with two bases', referring to the base minerals of diorite), but associated later perhaps with Greek diabasis 'transition'.