Recent data on the isotopes and geochemistry of kimberlites of the TSNIGRI-Arkhangelskaya pipe, Arkhangelsk diamondiferous province (Northern East-European platform)

The first data on the bulk and isotopic (Sr, Nd) composition of kimberlites from the low-diamondiferous TSNIGRI-Arkhangelskaya pipe, located in the Kepino field of the Arkhangelsk diamondiferous province, are presented. It is shown that the kimberlites belong to the moderate titanium type of kimberlites of the province and differ significantly from the previously studied kimberlites of the Kepino field in lower concentrations of TiO2, Ba, high field strength and light rare earth elements. Among all the kimberlites of the province, the kimberlites of the TSNIGRI-Arkhangelskaya pipe have the most radiogenic Sr composition (87Sr/86Sr t from 0.7068 to 0.7089), which may be due to a combination of several factors. It has been established that the kimberlites of the pipe are represented by two varieties, which have differences both in the concentrations of major and trace elements, and in the compositions of Sr and Nd isotopes. The composition of Nd isotopes (εNd from 0 to –0.6) for variety I kimberlites indicates their enriched source in the lithospheric mantle. Kimberlites of variety II have a less radiogenic Nd composition (εNd from –3.5 to –4.9), the interpretation of which is ambiguous: their formation from an even more ancient enriched source inside the lithospheric mantle compared to variety I cannot be excluded.