A PERIPATETIC APPROACH TO DIAMONDISM BY UTILIZING CARBON IN A SOLID SOLUTION OF A METAL OF GROUP VIII AS A SOURCE - PART TWO: CONSTRUCTION OF A UTILITY PHASE DIAGRAM BY UTILIZING SPECIMENS IN PART ONE

Pursuant to Part One (GSA Abst. Prog. 2009, 41, 7, 99) a P-T phase and transformation diagram, herein temporarily referred to as a utility phase diagram (UPD) to be distinguished from an experimentally determined P-T phase diagram, of carbon was constructed by utilizing specimens in Part One. As stated UPD differs from experimentally determined phase diagram of carbon (e.g. Bundy 1979) in (1) enlarged metastable fields; (2) wide distance between graphite and diamond. It is a matter of more than drawing a thicker line for graphite=diamond. Width of greater than two experimental error brackets calls for further examination. I propose this to be a not yet previously identified line-shaped field-like region involving thermodynamically distinct, surface mineralogically semi-distinct four phases of metastable diamond, graphite, metastable graphite, and diamond. It is not an actual phase field, since a one component system can not have a four-phase field.To bring it into compliance with the phase rule, a similarly line-shaped region of metastable diamond+metastable graphite+graphite is inserted between it and metastable diamond+graphite; and another line-shaped region of metastable graphite+metastable diamond+diamond inserted between it and metastable graphite+diamond. Thus a set of three bundled line-shaped regions with a positive slope in place of the good old equilibrium line of two isomorphs graphite=diamond. ^[1]

Attributable processes include (1) spontaneous (partial) graphitization on the surface of diamond (and in between layers where zoned - repetition through time) as stepped trigons, inverse trigons, and hexagons pronounced for {111}, {100}, and combinations of {111} and {100}; (2) amorphous film-like carbon on surface; (3)combination of (1) and (2); (4) other competing processes or factors such as polytypical preference, epitaxial vs. nonepitaxial, size, scale, and microstructural evolution.

As stated UPD reinforces the importance of the issue of rates. For instance, the rate of ascent for an average kimberlitic melt to reach the surface from the upper mantle needs to be in the order of hours to remain diamondiferous. In addition, the rate of quenching, nucleation, and growth need to be sufficiently rapid or relatively rapid.

^[1] United States utility patent application submitted for this portion