Geochemical parameters of metaterrigenous rocks of the Slyudyanka Group, southwestern Baikal area, as indicators of their source and protolith genesis

For the first time, full geochemical characteristics were obtained for metaterrigenous gneisses of the Slyudyanka Group, which are characterized by high concentrations of rare siderophile (Cr and Ni), Sc, and some lithophile elements (Ba and Sr). These features make the gneisses different from seemingly analogous post-Archean NASC and PAAS schists and similar to analogous rocks in ancient granulite-gneiss terranes and greenstone belts. Judging from the geochemical signatures revealed in the rocks, the protolith of the Slyudyanka rocks consisted of the decomposition products of a granulite-gneiss complex, such as the nearby Sharyzhalgai Complex. Complexes of this type consist of granitoids with elevated Ba concentrations and relatively low concentrations of Rb and contain nodules of ultramafic and mafic rocks. The latter and, particularly, their weathering products could predetermine the Cr and Ni concentrations of the Slyudyanka rocks that are anomalously high for gneisses of granodiorite (andesite) composition. The terrigenous material was deposited within the deepest part of a marginal sea.