Simple identification and quantification of microdiamonds in rock thin-sections

A method is described for the preparation of polished thin-sections which allows the rapid and quantitative detection of microdiamonds in high-P metamorphic rocks by distinctive pattern of striations on the polished surface of the thin-section. Diamonds as small as 1 mu m are revealed by a striation pattern as soon as they emerge on the surface during the polishing procedure, but this pattern disappears almost immediately after extraction of the microdiamond that caused it. Results are presented for samples from diamondiferous gneiss and marble from the Lake Kumdy-Kol region of the Kolchetav Massif, N Kazakhstan. The examination of > 600 polished thin sections of igneous and metamorphic rocks without a high-P origin showed striation patterns in << 1% of them; here, the striations could conceivably be due to outside contamination.