THE COMPOSITION AND CONDITIONS OF FORMATION OF THE CARBONIFEROUS TERRIGENOUS ROCKS OF THE SIBERIAN PLATFORM

We present new data on the composition and U–Pb (LA-ICP-MS) age of detrital zircons from the Carboniferous sedimentary rocks of the Siberian Platform cover, in which diamonds and accessory minerals were found, namely, the Baeronovka Formation in the southwest and the Tushama and Kata formations at the center of the Siberian Platform. The geochemical characteristics and results of analysis of minerals of the heavy fraction from the Baeronovka Formation indicate a predominantly felsic composition of the provenance rocks. The latter are, most likely, the rocks of the Cis-Sayan uplift of the Siberian Platform basement, including mostly Paleoproterozoic granitoids and volcanic rocks of the South Siberian postcollisional magmatic belt. Smaller amounts of detrital material got into the sedimentation basin of the Baeronovka Formation through the destruction of early Paleozoic rocks at the northern segment of the Central Asian Orogenic Belt. The geochemical characteristics of the terrigenous rocks of the Carboniferous Tushama and Kata formations testify to a felsic composition of the provenance rocks, but the mineral compositions of the heavy fractions indicate different compositions of these rocks. These data and the age of detrital zircons suggest that the Neoproterozoic sedimentary rocks and middle Paleozoic igneous rocks of the Baikal–Patom zone on the southern margin of the Siberian Platform and the Middle Paleozoic igneous rocks of the Vilyui rift and the Yakut diamondiferous province are the main provenances for the Tushama and Kata formations. The established differences in the composition and age of provenance rocks for the Carboniferous sandstones of different areas of the Siberian Platform confirm the earlier conclusions about the existence of several local sedimentary basins within it in the Devonian–Carboniferous. These basins formed after the middle Paleozoic tectonomagmatic activity accompanied by diamondiferous lamproite and kimberlite magmatism.