Diamond deposits of the Siberian craton: Products of post-1200 Ma plume events affecting the lithospheric keel

摘要

The Siberian craton was affected by more voluminous plume events during last 1200 Ma than any other craton on the Earth. These events produced many economically important deposits, of which the tectonic setting of diamond deposits and related alkaline magmatism is analysed in this paper. In space and time, they can be grouped into several subprovinces: Meso- to Neoproterozoic Yenisei-Sayan; Late Devonian to Early Carboniferous Vilyui; Permo-Triassic Tunguska; Late Jurassic Olenek; and Late Jurassic to Early Cretaceous Aldan. Regardless of their age and subprovince affinity, the alkaline intrusions, including kimberlites, preferentially occur within the Archean granulite-gneiss terranes, forming a north-south-trending 'Central Horde', framed by Archean granite-greenstone terranes. These terranes in the basement of the Siberian craton constitute Tungus-Anabar and Aldan domains of similar composition, sinistrally offset for about 870 km. Despite such similarity, diamond deposits are discovered to date only in the Tungus-Anabar domain. The seismic data show that the Central Horde in the Tungus-Anabar domain has a lithospheric keel, extending to a depth of greater than 250 km, whereas it is absent in the Aldan domain. At the surface, the Central Horde forms an uplift that controls lithofacies of Riphean to Cenozoic sedimentary basins in the Siberian craton, thus representing a long-lived and relatively stable feature, with storage of the diamonds in the subcontinental lithosphere at depth. Previous direct dating of diamonds from different Siberian kimberlites indicated that they were formed in Archean to Paleoproterozoic times. The reconstructions suggest that, in Meso- to Neoproterozoic times, the Siberian craton might have formed part of the supercontinents Columbia and Rodinia. Within them, Siberian craton was attached by its northern edge to the present western margin of the North American craton, whereas the southern margin of Siberia might have been facing a present northern margin of Australia. Together, they were part of a very long supercontinent, and plotting of all presently globally known diamond deposits shows that they would all occur along its axis, mapping its then possibly single lithospheric keel, or a Super-Horde. After breakup of Rodinia, due to penetration of the spreading ridges between the Australian and Siberian cratons, Siberia was translated towards Eastern Europe for about 5000 km during 500 Ma. It was during this translation that it was periodically affected by Neoproterozoic to Mesozoic plumes, which delivered the diamonds to the surface into all subprovinces except Aldan.