Fig. 7

Back-scattered electron images of major constituent phases in A0017, bright group. a Euhedral hexagonal morphology of pyrrhotite and plaquette magnetite. Some pyrrhotites show smooth surface texture. b Pyrrhotite having modified surface. The back side of A0017 only contains this modified pyrrhotite instead of smooth ones. c Framboidal and spherical magnetite. d Framboidal and plaquette shape magnetite. e Ca–Mg carbonate, dolomite. f Coarse-grained phyllosilicate. g Circular structure-enriched region. Larger ones are indicated by arrows. h High-resolution image of a circular structure. i Melt-droplet texture includes rounded opaque phases. j Melt-vein and –splash like morphologies. k Large melt-aggregate layer. l Enlarged view of a part of region shown in j. It has tiny bubbles and opaque minerals at the surface