NOVOSIBIRSK, Mar 7 Russian scientists as part of an international team of researchers have studied a 3.6 billion-year-old diamond found in Yakutia, Science in Siberia, a publication of the Siberian Branch of the Russian Academy of Sciences, reported.
It is specified that the jewel was found in the rocks of the Udachnaya kimberlite pipe. This is one of the largest diamond deposits in Russia. Samples of rocks and minerals of the lithospheric mantle brought here to the Earth's surface have been of interest to Russian and foreign scientists since the late 1960s. For more than half a century, geologists have been collecting and studying diamonds that were brought from depths of up to 250 kilometers millions of years ago. In one of these collections, a sample unique in age and education was found, an article about which was published in the authoritative journal Minerals.
«The diamond we discovered is apparently the oldest one studied to date. The age of the sulfide inclusion syngenetic to this diamond is estimated at approximately 3.6 billion years. According to our results, it was captured by growing olivine at sufficiently high temperatures — more than 1400 degrees Celsius and pressures of more than 5.5 hectopascals. This corresponds to depths of about 180 kilometers,» Academician Nikolai Pokhilenko, scientific director of the V. S. Sobolev Institute of Geology and Mineralogy of the Siberian Branch of the Russian Academy of Sciences, said in the message.
He explained that kimberlites are the most common rocks that carry diamonds from the depths of the lithospheric mantle to the earth's surface. The diamond crystal in question grew out of a silicate or sulfide melt. It was brought to the surface from refractory rocks that form the lithospheric mantle, included in a one and a half centimeter grain of the olivine mineral. The size of the diamond itself is only about 0.3 millimeters.
«In general, this find and its study confirmed earlier speculative assumptions about the time and parameters of the formation of the lower horizons of the lithosphere, reaching the pressures and temperatures of the diamond stability region, and, accordingly, the period of the appearance of the very first diamonds on the planet in them. Crystal from Udachnaya today, apparently, the oldest on Earth: at least among those that were held in the hands and studied by man,» Pokhilenko noted.
Scientists also managed to show that the conditions for the formation of diamonds in that era differed significantly from the characteristics of later processes of formation of the bulk of currently mined crystals: both the environment and the range of temperatures and pressures changed, and, accordingly, the depths of formation of later diamonds in a thicker and cooler lithosphere.