A CARBON-RICH MULTIPHASE INCLUSION IN A CHINESE DIAMOND AND ITS GEOCHEMICAL IMPLICATIONS

A multiphase inclusion in a diamond from Liaoning province, China cons ists of an olivine covered with large plates of graphite. Both phases are enclosed in a thin layer of glass that separates the multiphase in clusion from the host diamond. Microcrystallites of diamond and graphi te are embedded in the olivine and graphite plates. The characterizati on and distribution of all phases has been determined using micro-Rama n, infrared and Auger spectroscopy, and electron microprobe analysis. The structural form and morphology of the microcrystallites of diamond and graphite in the olivine suggests they formed contemporaneously wi th the olivine and the host diamond. An alternative suggestion is that they formed from carbon previously dissolved in the olivine at high p ressure and temperature. The genesis of the large graphite plates on t he surface of the olivine and beneath the glass film is less easily un derstood, especially as the composition of the glass is not fully docu mented. The occurrence of glass associated with other inclusions in di amond has been recognized previously by others although the compositio ns are varied. This is the first record of diamond and graphite occurr ing within a silicate inclusion in diamond.