GeologicalCharacteristics and Ore Genesis of the Beizhan Iron Deposit in the Western Tianshan Mountains, Xinjiang

Situated in east Awulale metallogenic belt of West Tianshan, Beizhan iron deposit is hosted in the intermediate-basic lava and pyroclastic rocks of Carboniferous Dahalajunshan formation. Orebodies appear in stratiform and stratoid shapes. Main metallic mineral in the iron ore is magnetite. The ore textures consist of subhedral-anhedral grainular texture, metasomatic relict texture, lath texture and radial texture. On the basis of its size and color, magnetite can be divided into two categories. Ore structures mainly contain crypto explosive brecciated type, penetration brecciated type, taxitic type, dense massived type, spotted type, banded type, mesh-vein type, and disseminated type, etc. The major altered minerals include diopside, garnet, actinolite, tremolite, epidote, chlorite, tourmaline, carbonate, etc. Based on the study of ore fabric, genesis and its occurrence characteristics, the metallogenesis of Beizhan iron deposit can be divided into two stages as crypto explosive-pulp metallogenic period(a) and crypto explosive-hydrothermal period(b), which could be further subdivided into four stages including magnetite-diopside-garnet stage(a₁), magnetite-actinolite-tremolite-garnet-epidote-chlorite stage (a₂), magnetite-garnet-chlorite stage (b₁), and epidote-tourmaline-carbonate stage (b₂). This iron deposit has a close genetic relationship with its wall rocks(intermediate-basic volcanic rocks of Dahalajunshan Formation), and is a volcanogenic magmatic-hydrothermal compound deposit.