Fig. 7

Zone VI: a Contact between hornblende-gabbro, meta-gneisses and olivine-orthopyroxene-(Mg-hornblende)-(Cr-Al-spinel) rock (Samples Ol4, Ol6, Ol8 and Ol35) zone VI. b Photograph of the olivine-orthopyroxene-(Mg-hornblende)-(Cr-Al-spinel) rock containing large orthopyroxene grains with visible cleavage, brown-weathered olivine and black Cr–Al-spinel. c Photograph of elongated olivine, orthopyroxene and black Cr–Al-spinel encircled by greyish chlorite. d Plain polarised light image of Cr–Al-spinel consisting of a sub-grain aggregates with black Al-magnetite-rich cores and brown to green rims. Its outer boundary consists of retrograde magnetite-chlorite replacement rims and olivine in the groundmass. e Backscatter image zoom-in of d consisting of zoned Cr–Al-spinel aggregates with bright cores becoming gradually darker toward the rims. Magnetite and chlorite rims form the outer boundaries of the sub-grain aggregate. f Crossed polarised light image of inclusion-free orthopyroxene intergrown with Mg-hornblende. g Backscatter image of sample Ol6 showing the prograde paragenesis Cr–Al-spinel, Mg-hornblende, orthopyroxene and olivine. The retrograde assemblage consists of chlorite, anthophyllite, tremolite and late serpentine