This page is currently not sponsored. Click here to sponsor this page.
A term originally applied to rocks consisting mainly of serpentine, but later extended to the rock suite of Alpine-type peridotites, gabbros, dolerites, spilites and keratophyres. Now used to define the association of basic to ultrabasic rocks thought to represent oceanic crust. A group of mafic and ultramafic igneous rocks ranging from spilite and basalt to gabbro and peridotite, including rocks rich in serpentine, chlorite, epidote, and albite derived from them by later metamorphism, whose origin is associated with an early phase of the development of a geosyncline. The term was originated by Steinman in 1905.