Details

Autor(en) / Beteiligte

• Hwang, S.L.
• Shen, P.
• Yui, T.F.
• Chu, H.T.
• Logvinova, A.M.
• Sobolev, N.V.

Titel

Low-energy phase boundary pairs and preferred crystallographic orientations of olivines in nanometer-sized ultrapotassic fluid inclusions of Aykhal diamond

Ist Teil von

• Lithos, 2018-12, Vol.322, p.392-404

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2018

Link zum Volltext

Quelle

Elsevier ScienceDirect Journals Complete

Beschreibungen/Notizen

• The healed internal conjugated cleavages at the core of Aykhal octahedral diamond sample AH2 were decorated with {111}dia-facetted ultrapotassic fluid/melt inclusion pockets containing nanosized graphite, phlogopite and olivine (Fo92) inclusions. These olivines are either rounded in pockets with ample fluid, or facetted by the {111}dia mold in the pockets with a fluid film. Transmission electron microscopy revealed two distinct crystallographic characteristics of olivine inclusions: (1) pronounced crystallographic texture of olivines grouped in specific diamond domain, and (2) frequent parallelism or sub-parallelism of specific low-energy faces of the two phases, mainly (010)ol, {120}ol, (001)ol and {111}dia, {110}dia, {100}dia in the order of decreasing preference, forming prominent (010)ol/{111}dia, (010)ol/{110}dia, (001)ol/{110}dia, {120}ol/{111}dia, and {120}ol/{110}dia low-energy phase boundaries with thin liquid film of 1–2 nm in between. These findings not only testify to the extremely low adhesion energies of olivine-diamond boundary pairs, but also imply that, in the presence of a fluid phase, the interfacial energetics and the energetically favored crystallographic orientations of olivine inclusions in diamond can be controlled simply by the settlement/attachment of low-energy facets of olivine crystals precipitating from the parental fluid upon the low-energy {111}dia or {110}dia surfaces of diamond. Such interfacial energetics control and the resultant low-energy boundary pairs are characteristically distinct from the common topotaxy or epitaxy between oxide/silicate mineral pairs, but are in a sense like the Van der Waals heteroepitaxy in artificial systems. •There are abundant nano-sized olivine+ ultrapotassic fluid inclusions along the healed micro-cleavages at the diamond core.•The distinct olivine-diamond low-energy phase boundary pairs with liquid film in between, as observed by TEM, are reported.•A possible genesis via settlement/attachment of facetted olivine precipitates upon diamond cleavage plane is proposed.