Article about microdiamond formation published in the prestigious journal Scientific Reports
April 8, 2021
An article explaining metamorphic microdiamond formation in the world was published in the prestigious journal Scientific Reports. The paper was authored by the CGS specialist Jana Kotková. She was inspired by her discovery of microdiamonds, reaching 5–30 micrometers in size, which she described in 2011. These microdiamonds, enclosed mainly in garnet in granulite rocks in northwestern Bohemia, were formed during plate subduction to the minimal depth of 140 km. The discovery of perfect octahedral diamonds is a worldwide rarity, whereas irregular grains and polycrystalline aggregates of diamonds are dominating elsewhere. Diamonds and diamond-hosting rocks are usually studied separately. The research team focused on combined study of diamonds and diamond-hosting rocks using nanoanalytical techniques (FIB-TEM, SIMS) as well as results of diamond dissolution experimental study. This research showed that peak P-T conditions of formation of host rocks are triggered by phase transitions related to water activity. Diamonds are formed from water-rich fluids at low temperatures, from melts formed during presence of water at higher temperatures, whereas octahedrons are formed only at extreme temperatures over 1100 °C from melts created by decomposition of fluid phases. The observed effect of temperature on diamond morphology can explain also the prevalence of octahedrons in case of much bigger diamonds from kimberlites, formed at higher temperatures. The Scientific Reports is a peer-reviewed, open access scientific journal published by Nature Research, covering all fields of nature sciences.