Geochemistry and Petrogenesis of Picrites of the Lesser Caucasus and Talysh zone

The analysis of the results obtained during the research on the regularity of alterations in the petrochemical and geochemical composition of picrites of the Lesser Caucasus and Talysh zone shows that the magmatic melts underwent a fractional crystallization process in the intrusive chamber. As a result, lutetium prevails insignificantly among the heavy rare earth elements in the melt. The moderately alkaline picrites of the Khojavand and Talysh zones of the Lesser Caucasus are noticeably enriched in light REEs and depleted in heavy REE. Evaluating the role of the melting fraction of the upper mantle substrate in forming picrites is one of the most important tasks for the future. For this purpose, the ratio of elements with similar geochemical properties is widely used in this study. These elements remain stable during relative differentiation. The main factor in their distribution is their enrichment with fluids and the melting fraction. The obtained results show that all the studied rocks correspond to the differentiation of primary magma in most cases. Rare earth elements are highly fractionated in all three zones, and the La/Sm ratio fluctuates in the range of 2.4-5.5. The maximum and minimum amounts of Eu and Sm elements show evidence of fractional crystallization. Our analysis shows that ultramafic magma underwent a complex crystallization path in the intrusive chamber, resulting in the formation of ore interlayers (titanium magnetite, apatite, etc.). The obtained mathematical models also confirm that crystallization differentiation is the regulator of the regular distribution of iron-group elements, alkali, alkaline earth, and rare earth elements in moderately alkaline ultramafic rock formations. The mantle source, subjected to metasomatic alterations, enrichment, and depletion, played a major role in the formation of alkaline and moderately alkaline picrites of the Lesser Caucasus and Talysh zone.