Diamonds Are Sought By Smell Like Truffles

Russian researchers suggest that diamond deposits should be explored by smell of soil. Kimberlite pipes deeply hidden under the sedimentary rock cover are given away by the composition of adsorbed gases in superstrata. Specialists of the All-Russian Research Institute of Geological, Geophysical and Geochemical Systems, Lomonosov Moscow State University, Open Joint Stock Company “Arkhangelskgeoldobycha” (Stock company “ALROSA”) have compared the composition of gases adsorbed in the rock of already known diamondiferous kimberlite pipes and the rock from the Russian plain, where diamonds have never been found. It has turned out that the kimberlite mass presence is given away by constrast in carbohydrates content in the soil and sediments. Kimberlite (blue earth) is specific rock filling earth cuts that were formed when gases burst through the earth’s crust strata – the so-called blow holes (diatremes). They consist of cemented rubble of mafic minerals. Altogether, about 1.5 thousand blow holes are known, and diamonds are found approximately in every tenth blow hole.

Geologists have investigated several hundreds of specimen from the kimberlite pipes from the Arkhangelsk and Yakut diamondiferous provinces, and 3,000 specimen from the Russian platform, which were considered the standard no-diamond-containing rock. The adsorbed gases’ composition was determined with the help the gas chromatograph by heating crushed rock up to 200 degrees C so that superfine carbohydrates films evaporated from the rock.

Then the researchers compared the correlation in the quantity of carbohydrates of various compositions adsorbed in the kimberlite and in the Russian platform rock. Their total contents is approximately equal in both cases – slightly less than cubic centimeter per kilogram, but in the specimen from diamondiferous rock mass, the share of heavy carbohydrates (containing 4 to 5 carbon atoms) is usually significantly higher. Sometimes, up to 15 cubic centimeters of gases per kilogram are contained in kimberlite rock, which practically does not happen even in oil and gas deposits, so kimberlite pipes are active “breathing” zones of the Earth, this fact giving away their presence even if volcanic pipes are located extremely deeply.

This method is applied for investigation of “gas fields” in search of oil and gas. Within several recent years, geologists have tried the method not only on kimberlite pipes, but also for ore and precious metals exploration.