Better to look at peridotites and volcanics. For peridotites there are 2 ways: petrography and mineral chemistry. Petrography: most ophiolitic ultramafics are cpx-poor: lherzolite and harzburgite; layered intrusions often have more clinopyroxene. Mineral chemistry: ophiolitic olivines and pyroxenes have Mg# ~90, layered intrusions often contain more Fe-rich mafic minerals.

Thanks Bob for your kind interest. You are right, there are several points from which we can differentiate between peridotides of these different setting. However, if we do not have peridotites, just gabbros, is there any way to know whether it is ophiolitic or layered-intrusion ones using the geochemistry and mineral chemistry?

Thanks again

Look at variation in Mg# value vs. TiO2 contents of gabbro clinopyroxene (abyssal and forearc peridotite fields are from Bedard et al., 2009). Also plagioclase Anorthite content vs. clinopyroxene Mg# in the gabbroic rocks can be compared with fields of MORB and arc gabbro from Burns (1985).

PLz note

Ghoneim M.F 1989 : J. African Earth Science. V.9.2.pp.289-295.