Geochemical signs of magmatic commingling in the Dashkesan gabbro-granite intrusion (Dashkesan iron ore deposit, Azerbaijan)

Abstract

Background. Geochemical signs of magmatic commingling are considered on the example of the Dashkesan Fe–Co deposit using geochemical data and mathematical modeling.Aim. To develop a petrological-geochemical model of magmatic commingling in the Dashkesan ore deposit.Materials and methods. The research methodology is based on field data, geochemical data (ICPMS, XRF) analysis of retrospective data and petrographic studies of thin sections.Results. The influence of the processes of contamination and magmatic commingling is shown using the Dashkesan deposit as an example. This site is associated with the formation of Fe-Co skarn deposits. The rich composition of accessory minerals, variations in textures and structures from hypidiomorphic granular to taxitic, the presence of numerous schlieren and cumulus accumulations of mafic minerals, and numerous xenoliths and enclaves — all are indicative of magmatic commingling processes. The rocks of the first gabbroid phase with increased contents of lithophile and REE elements are characterized by geochemical anomalies; at the same time, lower contents are observed for rocks of further stages of granitoids. The geochemical parameters indicate a relatively enriched magmatic source for the formation of rocks with contamination of the continental crust and subduction-fluid enrichment. These processes led to a deviation in the chemical composition of the Dashkesan rocks from the composition of typical island-arc igneous rocks. The source for the rocks of the gabbro-granite complex was the relatively enriched rocks of the mantle wedge. In addition to the process of melt mixing, the formation of the gabbro-granite complex was accompanied by crustal contamination and subduction enrichment.