<sup>40</sup>Ar/<sup>39</sup>Ar DATING OF MARUYAMAITE (K-DOMINANT TOURMALINE) FROM DIAMOND-BEARING METAMORPHIC ROCKS OF THE KOKCHETAV MASSIF

40 Ar/ 39 Ar analyses were made on maruyamaite (potassium-dominant tourmaline) from tourmaline-quartz-feldspar rocks discovered within the Kumdy-Kol microdiamond deposit (Kokchetav massif, North Kazakhstan). Turmaline yielded well-defined plateau age spectra whose values coincide error - ages of 502.3±8.0, 502.2±8.0, 506.0±8.0 Ma. These are much younger than 530±2 Ma determined for high-pressure metamorphism by different methods. Thus, formation tourmaline-rich cannot be associated with metamorphic events, and, therefore, testifies in favor low-pressure nature maruyamaite. Based coincidence data tourmaline crystals potassium contents, it can concluded that K/Ar system used dating metasomatic and processes.