Geological Characteristics And Ore Genesis Of Beizhan Iron Mine, Western Tianshan,Xinjiang

Beizhan Iron Mine is a large iron ore deposits which located at AwulaleMetallogenic Belt, Western Tianshan. Through exploration work in recent years, thereserves were increasing. Based on numerous field geological investigation data, theauthor detailed summarizes the geological characteristics, geochemical characteristicsof the deposit to explore the mineralization era, tectonic setting and source material ofmineralization, then, interpret the metallogenic mechanism and ore genesis,Recognizing summarized as follows.1. Awulale ore zone is located at the junction of two basement faults, eastern ofAwulale rift zone, the secondary fold-fault and ring structure development, BeizhanIron Mine located on the eastern end of the rift zone. Main ore bodies arepredominantly hosted by a set of basic-calc-alkaline basalts, basaltic tuffs, andesitictuffs, andesite, dacite volcanic-volcaniclastic rocks of Carboniferous Dahalajunshangroup, partially folder bedded marble. Roof and floor are altered volcanic ore, L3mainore body nearly EW and presented by lenticular （middle thick, tapering to theperipheral edge）, stratiform, veined.2. Volcanic rocks in the mine experienced several volcanic cycles and the agesmainly in301Ma~321Ma, formed in the late Early Carboniferous continental marginarc environment which due to Junggar Ocean subduct to Yili-Central Tianshan block.Outcropping of granite in the southern is A-type granites which zircon U-Pb agesmostly in301Ma~307Ma, formed in the late Early Carboniferous-early LateCarboniferous, the formation background of the magmatic rocks in this phase waschanging from subduction volcanic island arc to post-collision stretch environment, itstectonic regime has changed.3. Trace elements and Fe isotope geochemistry results showed that:①Magmametallogenic epoch magnetite comes from the mantle of basaltic magma and intrusioninto the early volcanic rocks with tectonic activity after liquation, source of iron is deepwith magmatic origin;②hydrothermal metallogenic epoch magnetite is subject tocontact metasomatic formation by Crustal contamination of the silicon-rich magma andvolcanic rocks or marbles with hydrothermal origin.4. The δ56Fe value of dense massive magnetite ore was concentrated around zeroand the range of variation is small, since the δ56Fe value of magmatic iron ore alsoconcentrates near zero, thus indicating that the magnetite in this period is magmaticorigin. However, it is almost less than zero, and have some overlap with hydrothermaldeposits, which showed that the source of iron is various, mostly from the mantlemagma, a small part from the hydrothermal. Veined ore relative enrichment iron lightisotopes, distribution range larger than denser massive ore iron isotope. Descriptionvein ore is mainly formed by hydrothermal activity. 5. Beizhan Iron Mine is a composite iron deposit which undergone magmatic andpost-hydrothermal contact metasomatic mineralization.