Abstract:

The PHaLek iron deposit is situated in the Northwest end of the Truongson fold belt, an elongate trending belt, which forms part of the Indochian Terrane of SE Asia. It is one of huge iron deposits associated with magmatic activities in the Truongson metallogenic belt. Combined their field geology survey, the micro-petrographic and element geochemical analyses are finished for the ore-forming intrusive rock, the wall-rock of the ore bodies and the iron ore. It was shown that the granitic rock related to the mineralization belongs to the “I” type granite, calcium alkali series and metaluminum, and formed in the tectonic environment of volcanic island arc. Three main ore types are recognized in PHaLek mine district, i.e. massive magnetite ore, pore-shaped hematite ore, gravel-earthy ore. Based on trace element geochemical analysis of the ore and wall-rock, it was concluded that the PHaLek iron deposit is characterized by composite metallogenesis, which can be divided three main metallogenic epochs. The earliest one is the skarn magnetite mineralization associated with the Variscan intrusive magmatism. Thereafter, the volcanic eruption resulted in pore-shaped lava-type hematite mineralization in continental rift basins, which formed in late stage of continental folding orogenic process. Finally, supergene physical and chemical weathering mineralization caused the gravel-earthy iron mineralization on the surface, due to the crustal uplift in the Cenozoic period.

Key words: iron deposit, metallogenesis, Truongson fold belt, lava type;gravel-earthy, PHaLek, Laos