Geologic Feature And Metallogenic Prediction Of Mijiang Forestry Farm Iron Deposit In Hailin,Heilongjiang Province

Mijiang Forestry Farm iron deposit,located in Hailin,Mudanjiang City,is located in the north and middle part of marginal uplift of Fangzheng – Changting Fault in Yichun – Zhangguangcai Ridge orogenic belt.The intrusive rocks in the area are mainly late Triassic to early Jurassic syenogranite and monzonitic granite,early Jurassic bojite,and late Jurassic syenogranite.The magnetite orebodies are hosted in the early Jurassic bojite,hardly broken by the structures,and occur in stratiform.The ore rocks are mainly banded and infected.The mineral composion of the ores is complex.The main metal minerals consist of magnetite and pyrite,with minor chalcopyrite,ilmenite,pyrrhotite and hematite.The magnetite occurs dominantly as grained,subhedral to anhedral granular.According to the features of ore body and the relationship between ore body and rocks,the deposit is formed by the further enrichment during the magmatic differentiation.The geochemistry feature suggests that the magmatic rocks were formed by the cooling crystallization under the gravity differentiation.The temperature and pressure play an important role in the formation and enrichment.The ore-forming fluid were formed with the temperature and pressure decrease,which caused by the decreasing gravity.The better crystallization make bigger mineral aggregate,which contains more magnetite.Otherwise the mineral is smaller.According to the result of magnetic survey,the high magnetic anomaly was caused by the magnetite.The outcropped bojite in the area is positive magnetic anomaly.The area of bojite and the positive magnetic anomaly fit well,and the boundary is clear.The expected value of magnetic outlier is 1600-5000 n T.Based on the study of basic magmatic rocks,we come up with three prospecting targets,where we may discover economic ore-bodies..