On the analcime nature in Permic rocks of the Caspian and Solikamsk depressions

Abstract

The findings of authigenic analcime are described in the sheshmin ore and barren sandstones of the Solikamsk depression of the Pre-Ural foredeep, as well as the Upper Kazan carbonate-argillite and Tatarian mudstone-siltstone rocks of the Saratov-Orenburg trough of the Caspian basin. Based on the Na/Al and Si/Al ratios, analcimes are divided into three groups. The first is confined to carbonate layers in the terrigenous strata, is characterized by high sodium and silicon contents and is associated with the transformation of pyroclastics in highly alkaline conditions. For analcimes of the second group, formed in clayey and carbonate-clayey layers, enriched in sodium and depleted in silicon, a connection with soda waters is assumed. Low sodium contents and variability of silicon in analcimes of the third group from polymictic cuprous and barren sandstones indicate the presence of fragments of acidic and basic (tholeiitic) rocks in the rock.