Abovyan – an enigmatic Kiruna-type apatite-magnetite deposit in Armenia

The Abovyan deposit in Armenia represents a unique example of relatively young, Late Miocene age Kiruna-type apatite-magnetite mineralization in the region. Initially identified in 1947 by a team of Armenian geologists, based on the well-pronounced magnetic anomaly, it remains largely obscure outside the confines of Soviet-era scholarly literature. This deposit resides within a magmatic formation predominantly of intermediate composition, comprising andesites and dacites, and characterized by disseminated and massive magnetite ores and transitional varieties between them. The deposit is fully covered by several dozens of meters of younger, Pliocene-Quaternary volcanic rocks, so the samples for our study were collected from drill cores. These specimens, encompassing both host rocks and ores, retain critical insights into the processes governing ore segregation and accumulation, despite having a large influence of the autometasomatic alteration. The young age (~6-7 Ma, K-Ar, Sarukhanyan, 1969) and, consequently, the absence of later metamorphic events in the area is the main advantage of the Abovyan deposit over the majority of Kiruna-type deposits around the world in terms of preservation of the initial textures and other mineralogical and petrological features. Several generations of the magnetite-apatite ores could be clearly distinguished in the ores, which include (1) magnetite melt-like droplets in the host-rocks, (2) massive magnetite apatite ores, (3) magnetite-hosted breccias of the altered host-rocks and (4) several generations of late hydrothermal veins. Notably, the apatite within these ores exhibits a remarkable enrichment in light rare earth elements (REEs), reaching concentrations as high as 4 wt.%. This level of enrichment is notably higher than that observed in other Kiruna-type deposits (Frietsch, Perdahl, 1995) and is accompanied by the other critical metals’ mineralization (e.g., Th). Ongoing research on the geochemistry and geochronology of the Abovyan deposit may be a key to understanding the formation of the Kiruna-type deposits and their REE potential, in particular.

This study was funded by the Science Committee of RA (Research projects №23PostDoc-1E001 and  № 22IRF‐08), and by the Swiss National Science Foundation (grant 200021_188714).

Frietsch, R., Perdahl, J. A., 1995. Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types. Ore Geology Reviews, 9, 6, 489-510.

Sarukhanyan, L.B., 1969. Some questions about the genesis of the Abovyan apatite-magnetite deposit. Proceedings of the Armenian SSR Academy of Science, Earth Sciences, 3, 40-49 (in Russian)