Characterstics And Genesis Of The Zhibo Iron Deposit In Xinjiang Province

The Zhibo iron deposit is a large and important magnetite deposit which isprospected at the Awulale metallogenic belt in Western Tianshan Mountainous ofXinjiang. On the basis of previous research, detailed field investigation and indoorsynthetic analysis hava been carried out on the deposit, with a focus on the study of itsgeological, mineralogical and geochemical characteristics. Some significantachievements in metallogenic tectonic setting, physical-chemical condition, materialsource and genesis of the Zhibo iron deposit have been obtained in this thesis.The Zhibo iron deposit occurs at the center of caldera ring fault system, and istectonically located in the Carboniferous island arc belt of the northeastern Ili block.The ore bodies of the Zhibo iron deposit are hosted in basaltic andesite of the LowerCarboniferous Dahalajunshan formation with layered, quasi-lamellar and lenticularforms. The ore types mainly include massive, disseminated, breccia, mottled, bandedand stockwork ores. The mineralization process of the Zhibo iron deposit can bedivided into two metallogenic periods which are magmatic period and hydrothermalperiod, including three metallogenic stages: magnetite+diopside, magnetite+K-feldspar+epidote and quartz+sulfide+carbonate stages. The mineralogical andgeochemical characteristics of the Zhibo iron deposit show that its metallogenictectonic setting is island-arc environment. The magnetite was formed in an alkalineand high oxidation environment, with formation temperature of about650℃duringmagmatic period and about300℃during hydrothermal period. The geochemical datasupport derivation of volcanic rock and magnetite ore from basaltic magma formed bypartial melting of depleted mantle wedge alterated by fluids in subduction zones, withthe same material source. The Zhibo iron deposit is a magmatic (main)-hydrothermal(minor) deposit. The basaltic magma intruded upward along deep fault and formed theprimitive volcanic rock. Because of the change of physical-chemical conditionsduring its intrusion, the iron ore slurry was liquated from the basaltic magma. Theinstusion of the iron ore slurry into primitive volcanic rock would be responsible for the formaton of the magmatic type magnetite orebody, and alteration of thesurrounding rock by the residual magmatic hydrothermal fluid for the formation of thehydrothermal type magnetite orebody.