Petrogenesis of orthopyroxene-magnetite-ilmenite intergrowths from an ultramafic layer

A new occurrence of myrmekitic orthopyroxene-magnetite-ilmenite intergrowth from a thin ultramafic layer within a heterogeneous noritic rock from the Frederiksdal area, South Greenland, was investigated chemically and texturally. Compositionally, the intergrown ilmenite and orthopyroxene show the lowest recorded MgO content from pyroxene-oxide mineral intergrowths. The magnetite-ilmenite intergrowth has skeletal morphology, consisting of sets of thinly tabular plates parallel to the (111) planes of the spinel structure. The orthopyroxene-oxide intergrowth is considered to be the result of a simultaneous magmatic crystallization, that of the oxide minerals being faster.