Is the Imposition of Diamond Morphology on Mineral Inclusions a Syngenetic or Post-Genetic Process with Respect to Diamond Formation?

Recent studies showed that inclusions of the same phasewithina single diamond are relicts of an original monocrystal that underwenta dissolution event during diamond growth. Interestingly, these inclusionsdeveloped both diamond-imposed (i.e., cubic-octahedral shape) andlobed morphologies with rounded shapes and/or embayments. Whetherthe diamond-imposed morphology is developed during or after entrapmentof the inclusion is unknown. We addressed the problem in two ways:(i) by determining the thermodynamic conditions under which mineralinclusions can modify their size (e.g., a single inclusion separatesto give two inclusions with different size) and morphology, when trappedin diamond and (ii) by critically reviewing and discussing the recentobservations on mineral inclusions in diamond. Accordingly, we developeda thermodynamic model which considers all the involved energetic contributions(i.e., surface and strain energies) to completely describe the Gibbsenergy of a closed system designed to forecast the size evolutionof two adjacent (or a single) inclusions, at constant T and P. Basedon this model and analyzing the existing scientific literature ondiamond, we propose an experimental/observational protocol to evaluatewhether post-entrapment modification of inclusions has occurred.A thermodynamic model was developed tounderstand whetherthe diamond-imposed morphology is developed during or after entrapmentof the inclusion