Thermal state of the lithospheric mantle beneath the Birekte terrain: reconstructions based on the study of xenocrysts from different-aged kimberlites of the Yaku-tian kimberlite province

The study presents the results of an investigation of clinopyroxene xenocrysts sampled from the heavy fraction concentrate of kimberlites from the Ivushka pipe (Toluopka field) and Anomaly 75/90 (Molodo field), located within the Birekte terrane of the Siberian craton. Reconstructions of the thermal state of the lithospheric mantle indicate that during the Paleozoic kimberlite magmatism (Toluopka field), the thermal boundary between the lithosphere and asthenosphere was similar to that in the southern kimberlite fields and was approximately 230 km deep. Preliminary estimates for Anomaly 75/90 suggest that by the Mesozoic, the lithospheric mantle in this region had likely already thinned and undergone significant transformation, with the xenocrysts transported by kimberlite magma representing fragments of rocks containing multiple generations of clinopyroxenes.

Although the lithospheric thickness of the northern and southern fields was quite similar during the Devonian, the kimberlite magmas of the southern fields entrained a broader range of potentially diamondiferous rocks (depths of 130–230 km) during ascent compared to those of the northern fields (depths up to 170 km). These results may indirectly explain the significant difference in diamond potential between the Devonian kimberlites of the southern fields, located on Archean terranes, and the northern fields, which belong to the Proterozoic blocks of the Siberian craton.