Geological Phenomenon of Yalguba Ridge Variolite from F. Yu. Levinson-Lessing’s Time until Today: Mineralogical and Geochemical Aspects

Resumo

The Yalguba Ridge in Karelia is a reference geological object for studying Paleoproterozoic variolitic lavas. F. Yu. Levinson-Lessing—the prominent Russian petrologist—was the first to describe these lavas in detail in 1884. Our paper presents up-to-date results of contemporary mineralogical and geochemical studies. Several generations of pyroxenes with magmatic and metamorphic zoning reflect variations in the chemical compositions and thermodynamic parameters of melts during crystallization. The contents of rock-forming and trace chemical elements are estimated for varioles and the rock matrix. Based on a comparison of the mineralogical and geochemical data, we draw conclusions on the crystallization sequence of immiscible melts and the role of crustal-material contamination of basaltic melts.