This paper provides a top-down nanoscale analysis of Cu-Ni-Fe sulfide inclusions in laurite from the Taitao ophiolite (Chile) and the Kevitsa mafic-ultramafic igneous intrusion (Finland). High-resolution transmission electron microscopy (HRTEM) reveal that Cu-Ni-Fe sulfide inclusions are euhedral to (sub)-anhedral (i.e., droplet-like) and form single, biphasic or polyphasic grains, made up of different polymorphs, polytypes and polysomes even within a single sulfide crystal. Tetragonal (I4\(\stackrel{-}{2}\)d) and cubic (F\(\stackrel{-}{4}\)3m) chalcopyrite (CuFeS₂) host frequent fringes of bornite (Cu₅FeS₄; cubic F\(\stackrel{-}{4}\)3m and/or orthorhombic Pbca) ± talnakhite (Cu₉(Fe, Ni)₈S₁₆; cubic I\(\stackrel{-}{4}\)3m) ± pyrrhotite (Fe_1 − xS; monoclinic C2/c polytype 4C and orthorhombic Cmca polytype 11C) ± pentlandite ((Ni, Fe)₉S₈; cubic Fm3m). Pentlandite hosts fringes of pyrrhotite, bornite and/or talnakhite. Laurite and Cu-Fe-Ni sulfide inclusions display coherent, semi-coherent and incoherent crystallographic orientation relationships (COR), defined by perfect edge-to-edge matching, as well as slight (2–4º) to significant (45º) lattice misfit. These COR suggest diverse mechanisms of crystal growth of Cu-Fe-Ni sulfide melt mechanically trapped by growing laurite. Meanwhile, the mutual COR within the sulfide inclusions discloses: (1) Fe-Ni-S melt solidified into MSS re-equilibrated after cooling into pyrrhotite ± pentlandite, (2) Cu-Ni-Fe-S melts crystallized into the quaternary solid solution spanning the compositional range between heazlewoodite [(Ni, Fe)_3±xS₂] (Hz_ss) and ISS [(Cu_1±x, Fe_1±y)S₂]. Additionally, nanocrystallites (50–100 nm) of Pt-S and iridarsenite (IrAsS) accompanying the sulfide inclusions spotlight the segregation of PGE-rich sulfide and arsenide melt earlier and/or contemporarily to laurite crystallization from the silicate magmas. Cobaltite (CoAsS)-gersdorffite (NiAsS) epitaxially overgrown on laurite further supports the segregation of arsenide melts at early stages of chromitite formation.

本文对来自 Taitao 蛇绿岩（智利）和 Kevitsa 镁铁质-超镁铁质火成岩侵入体（芬兰）的月桂石中的 Cu-Ni-Fe 硫化物包裹体进行了自上而下的纳米级分析。高分辨率透射电子显微镜 (HRTEM) 显示 Cu-Ni-Fe 硫化物包裹体是自面体到（亚）反面体（即液滴状），并形成单相、双相或多相晶粒，由不同的多晶型、多型和多核糖体甚至在单个硫化物晶体内。四方晶系 (I4\(\stackrel{-}{2}\)d) 和立方晶系 (F\(\stackrel{-}{4}\)3m) 黄铜矿 (CuFeS ₂ ) 具有频繁的条纹斑铜矿 (Cu ₅ FeS ₄ ；立方 F\(\stackrel{-}{4}\)3m 和/或斜方 Pbca) ± 塔拉金矿 (Cu ₉ (Fe, Ni) ₈ S ₁₆ ; 立方 I\(\stackrel{-}{4}\)3m) ± 磁黄铁矿 (Fe _1 − x S ; 单斜晶 C2/c 多型 4C 和斜方晶 Cmca 多型 11C) ± 镍黄铁矿 ((Ni, Fe) ₉ S ₈ ；立方 Fm3m)。镍黄铁矿含有磁黄铁矿、斑铜矿和/或塔钠铁矿的边缘。月桂石和 Cu-Fe-Ni 硫化物夹杂物表现出相干、半相干和非相干晶体取向关系 (COR)，由完美的边到边匹配以及轻微 (2–4°) 到显着 (45°) 晶格失配定义。这些 COR 表明了通过生长的月桂石机械捕获的 Cu-Fe-Ni 硫化物熔体晶体生长的不同机制。同时，硫化物包裹体内的相互COR揭示了：（1）Fe-Ni-S熔体凝固成MSS，冷却后重新平衡成磁黄铁矿±镍黄铁矿，（2）Cu-Ni-Fe-S熔体结晶成四元固溶体跨越黑铁矿 [(Ni, Fe) _3±x S ₂ ] (Hz _ss ) 和 ISS [(Cu _1±x ) 之间的成分范围, Fe _1±y )S ₂ ]。 此外，伴随硫化物包裹体的 Pt-S 和铱砷矿 (IrAsS) 纳米微晶 (50–100 nm) 突出了富含 PGE 的硫化物和砷化物熔融的分离，该熔融早于和/或同时发生在硅酸盐岩浆中的月桂石结晶中。月桂石上外延生长的钴矿 (CoAsS)-gersdorffite (NiAsS) 进一步支持了铬铁矿形成早期阶段砷化物熔体的偏析。