GEOCHEMISTRY OF CALCAREOUS-SILICATE ROCKS OF THE KHARAGOL FORMATION, SOUTHERN BAIKAL REGION

Abstract

Complete geochemical characteristics have been found for calcareous–silicate rocks of the Kharagol Formation that serves as a reference unit within the Khamardaban polymetamorphic composite terrain (southern folded framing of the Siberian Platform, Baikal–Khubsugul region). We studied the high-grade (granulite) domain known as Slyudyanka crystalline complex of the southern Baikal region. The Kharagol Formation is composed of different diopside, scapolite–diopside, and wollastonite–scapolite–diopside gneisses and crystalline schists with a variable calcite content. Petrogeochemical data suggest that their protoliths were tuffoids with different amounts of calcareous material. The volcanoclastic component of tuffoids is closest to the Andean-type calc-alkaline andesites. The Kharagol paleobasin was probably located at the active continental margin. Within the studied metamorphic sequence, the Kharagol Formation marks a sharp change in sedimentation conditions and may be considered a boundary of subterrains with protoliths formed in different paleogeodynamic settings. Geochemical indicators of calcareous–silicate rocks of the Kharagol Formation in different metamorphic zones may be high Cr, Ni, and Ba contents.