Агуйт төмрийн илрэлийн эрдэслэг бүрэлдэхүүний судалгаа

Abstract

This study was conducted to determine the structure, mineral composition, and origin of magnetite mineralization hosted within deep-seated ultramafic to mafic intrusive rocks of Cambrian age, located in the Khukh-Undur Mountain area, a subrange of the Khantaishir Range, near Biger soum, Gobi-Altai Province. These igneous bodies are intruded into the Khantaishir Metacomplex, which predominantly consists of hornblende-bearing granitic gneiss, dioritic gneiss, medium-grained amphibolite, and migmatites. Geological mapping, sampling, petrography, ore microscopy, and electron probe microanalysis (EPMA) were employed as primary investigation methods.

Petrographic analysis revealed that the studied samples are mainly composed of ultramafic plutonic rocks such as olivinite (harzburgite) and pyroxenite.

Ore microscopic observations identified magnetite, chromite, hematite, pentlandite, and chalcopyrite as primary ore minerals, occurring as disseminated, vein-type, and massive textures within the host rocks. Magnetite occurs in two distinct stages, indicating both early and late magmatic origins.

EPMA results show that magnetite contains tFeO = 81.06–88.22%, V2O3 = 0.58–0.96%, and TiO2 = 0.76–3.34%, supporting its magmatic origin. In some zones, tFeO content decreases (36.67–41.32%) and TiO2 increases (52.31– 55.75%), suggesting the presence of ilmenite phases. Chalcopyrite shows compositions of Cu = 30.35–34.12%, Fe = 29.94–30.77%, and S = 27.73–35.63%.

These findings suggest that the magnetite and ilmenite mineralization in the study area formed from magmatic processes in two stages and is associated with sulfide minerals such as pentlandite and chalcopyrite. This indicates the presence of massive iron– titan-nickel–copper mineralized bodies with economic potential. The study provides fundamental data for further research on ore genesis and for planning exploration activities in the region.