Neodymium and Strontium Isotopic Measurements on Single Subcalcic Garnet Grains from Yakutian Kimberlites
Jacob, Dorrit E.; Jagoutz, Emil; Sobolev, Nick V.
published: May 1, 1998
ArtNo. ESP154017202012, Price: 29.00 €
Discrete grains of subcalcic garnets from Yakutian kimberlites have been investigated for major elements, Sm, Sr, Nd, Rb concentrations as well as for 87Sr/86Sr and 143Nd/144Nd ratios. cNdi-values range between +1 and -40.6, 87Sr/86Sr are between 0.70521 and 0.72632, confirming the very heterogeneous character of these minerals. SmlNd ratios range from 0.025 to 0.828. Strong positive correlations of 87Sr/86Sr-ratios with Cr and Mn are consistent with an origin of the subcalcic garnets from Cr-spinels from spinel-harzburgites which were subducted into depths of the diamond stability field and reacted there with a metasomatic agent producing subcalcic garnet and olivine at the expense of Cr-spinel, orthopyroxene and any remaining clinopyroxene. It is proposed that subcalcic garnets are formed episodically through time and that kimberlites randomly sample populations of these minerals which are not necessarily cogenetic.