The Multi-Isotope Composition of Sulfur in Sulfides and Microfossils of the Mesoarchean Leksa Pyrite Ore Occurrence of the Karelian Craton: New Data on Abiogenic and Biogenic Effects on the Formation of Ancient Ores

Abstract

Pyrite ores have been formed on the Earth from the Archean to the present. The most important component, sulfur, can be provided by the following three sources: igneous, sedimentary, and sulfates of seawater. Studies of contemporary hydrothermal systems of the seabed, which are considered to be the ore-generating mechanism responsible for the oldest pyrite deposits, have shown that magmatic sulfur and seawater sulfate make the major contribution to the total sulfur budget in ore formation [1–3]. The question of the influence of the simplest forms of life on the processes of ore formation, which is especially important and debatable for the Archaean deposits, is also widely discussed. However, our understanding of the processes occurring at the early stage of the Earth’s development is limited to a few available well-preserved geological samples, while the overwhelming majority of Archean rocks have experienced some degree of metamorphic changes.