Home – Home – Jornals – Russian Geology and Geophysics 2006 number 4

Diamondiferous calc-silicate rocks occur at the Kumdy-Kol' deposit as partings and lenses among biotite gneisses and schists. The most frequent alternation of these rocks is observed in crosscut 45 of the adit driven during the exploration of this metamorphic diamond deposit. Our collection of samples taken from this crosscut permitted research into the geochemistry of rocks with contrasting contents of diamonds. Study was also given to carbonate rocks with distinct banding and garnet-pyroxene rocks with abnormally high contents of diamonds taken from the adit spoil heaps. These rocks were analyzed by ICP MS and ICP AES, which ensured a simultaneous determination of a wide spectrum of trace elements with low detection limits. The determined contents of incompatible elements evidence that the diamondiferous calc-silicate rocks are not a mixture of carbonates with clays only. It is not ruled out that carbonates are also mixed with an end-member compositionally different from protoliths of garnet-biotite gneisses and schists. It is shown that at different stages of metamorphic evolution, including exhumation, subducted continental crust might have been the source of high-density fluids or melts metasomatizing the upper mantle. At the same time, the interaction of these fluids with carbonate partings present among the subducted sediments might have hindered their far migration.