Features of the impurity composition of diamonds from placers of the northeastern Siberian craton

Abstract

Diamond crystals from the Istok (25 crystals) and Mayat (49 crystals) placers were studied using the EPR-, IR-, and luminescence methods. The total content of impurity nitrogen in forms of A-, B-, and C (P1)-centers ranges from 50 to 1200 ppm. According to the EPR-spectroscopy, the presence of nitrogen C(P1), N3V nitrogen-titanium OK1, N3, NU1 impurity centers was established in the investigated crystals. Crystals from the Istok placer contain the OK1, N3, NU1 centers, but luminescence attributed to the oxygen-containing centers is absent in the region of 610-670 nm. For the Mayat placer crystals, the reverse situation was observed. The luminescence ascribed to the oxygen-containing centers was detected for 17 crystals, but there were no OK1, N3 and NU1 centers according to the EPR- and luminescence. This result contradicts the arguments of a number of authors about the oxygen nature of these defects. For 5 crystals from the Mayat placer, the nickel impurity was registered. This indicates the presence of ultrabasic paragenesis diamond crystals in this placer.