Origin and implication of pentlandite in Chang'e-5 lunar soils

Abstract

Sulfides are important accessary minerals in lunar rocks and have great implications for lunar magma activity and subsequent evolution. Pentlandite, as one of important sulfides, has been found over 40 years. Its origin is however remain controversial. Here, we studied the texture, chemistry and crystallography of pentlandite and associated sulfides in Chang'e-5 (CE-5) lunar soils. Pentlandites occurred as lamella and veinlets in troilites, forming a troilite-pentlandite assemblage in basalt but troilite-pentlandite-taenite assemblage in breccia. Transmission electron microscopy (TEM) analyses provide the first robust evidence in lunar samples that pentlandites from both basalts and breccias were exsolved from troilite, rather than originate from the reaction between mobilized sulfur and metallic FeNi, or mobilized Ni with troilite. Considering that troilites in breccias have higher Ni content than basalts, we speculated the origin of pentlandite in breccia might involve a geological process with addition of exotic meteorites. These findings provide new clues for exploring the origin and geological evolution of sulfides on the Moon.