A coarse-grained basic igneous
rock composed of essential calcic plagioclase
and orthopyroxene. Norites also can
contain up to 50% clinopyroxene and can be considered orthopyroxene dominated
gabbro. Minor components can include biotite
and hornblende. Norite is generally found
in layered igneous intrusions formed by progressive crystal fractionation.
The crystallisation of large amounts of orthopyroxene can occur by the reaction
of olivine with the magma.
Norite is sometimes associated with anorthosite
and troctolite. It is found extensively
in the highland regions of the Moon.
AND PLANETARY SCIENCE