Mineralization aspects of trace and rare earth elements in the brecciated rocks in the Se-Chahun ore deposit: insights from mineralogical and geochemical evidence

Abstract

Mineralogical examination of the gangue and ore parts of the Se-Chahun magnetite-apatite ore deposit revealed the existence of Th and REE bearing minerals with paragenetic relationships with amphiboles, magnetite and calcite. Trace and REE host minerals are found in both of the gangue and the magnetite-apatite ore showing remarkable concentration in a phase referred to as the brecciated phase. This zone (phase) is characterized by high amounts of trace (Th) and light rare earth elements including La, Ce, Pr and Nd that were revealed in geochemical analysis. Mineralization of these elements is related to fluids appeared after magnetite mineralization in the region and resulted in metasomatism of the host rocks and a part of the ore and also concentration of the REE and trace elements as phosphates and silicates, respectively. There is not a clear key concerning the origin of these fluids but based on the geochemical evidence, the probable provenance is thought to be related to the magmas derived from the arc related subvolcanic bodies injected in subduction zones. Based on the paragenetic and geochemical evidence, a part of these elements is transported by carbonate complexes and accumulated in the brecciated rocks.

Keywords

• mineralogy
• trace and rare earth elements
• brecciated phase
• sechahun ore deposit