Study On Characteristics Of Intrusive Rocks Related To Mineralization And Metallogenic Time Of Huojihe Molybdenum Deposit,Xiao Hinggan Mountains

Huojihe molybdenum deposit is located in the north part of the Yichun-Zhangguangcailing metallogenic belt,Xiao Hinggan mountains.And it is also located in the north part of Wuxing-Guansong town middle uplift belt,which is belongs to Hinggan mountains-Inner Mongolia geosyncline fold zone,Yichun-Yanshou geosyncline fold system tectonicaly.The mining area is a large molybdenum deposit discovered by Jiamusi Geological Exploration Institute of Heilongjiang Province,but it is not enough in the petrological research about this area,there are remains controversial about the petrogenesis,the formation environment,the metallogenic times and the ore-forming material sources.So this paper have studied the petrology,geochemistry,and Pb isotopes,and analysised the Re-Os isotope age of molybdenite in the mining area.There are three types of intrusive rocks in the Huojihe molybdenum mining area:biotite monzogranites,aplite granites and quartz monzonite porphyries.To synthesize the studies of both field and mineralogy and texture,the biotite monzogranites widespread occurrence of alteration and mineralization,the alteration mainly are potassium and sericitization,the mineralization mainly are disseminated-stockwork molybdenite mineralization and a small amount of pyrite and brass mineralization.No obvious alteration in the aplite granites,only have some small vein molybdenite mineralization and a little pyrite and brass mineralization.The quartz monzonite porphyries shows a weaker alteration than the biotite monzogranites,which are sericitization and potassium.The mineralization mainly is magnetite.Biotite monzogranites is the mainly wall rock in the area.Geochemistry characteristics shows the intrusive rocks in mining area mainly are high-K calc alkaline-shoshonitic series,metaluminous-peraluminous rocks.All of the intrusive rocks are enriched in LREE related to HREE,two kinds of granites show slightly negative or non Eu anomalies,but the quartz monzonite porphyries show slightly positive Eu anomalies.Three kinds of rocks' HREE fraction degree are significantly different and the biotite monzogranites have the maximum fraction ibetween the pattern of the LREE and the HREE.In terms of trace elements,the biotite monzogranites and aplite granites are enriched in large ion lithophile elements(LILE)such as Rb,K,Th,U and Pb etc.relative to high field strength elements(HFSE),depleted Nb,Ta,P and Ti,showing very similar geochemistry to the island arc magmatic rocks.The quartz monzonite porphyries are enriched in Ba,U,La,Zr and Hf,depleted Rb,Th,Nb,Sr,P and Ti,showing similar geochemistry to the earth crust.In addition,themagmatic rocks in mining area is enriched in the metal elements of Mo?Cu?Pb?Zn?W and Cr.The whole rock Pb isotope analysis in the mining area showing the characteristics of mixing by the upper crust and the mantle.The biotite monzogranites in the mining area have similar magma source,mainly are the results of metamorphic grewack's partial melting in the upper crust mixed with a small amount of mantle composition,and have the characteristics of volcanic arc or syn-collision.The isochron age of the molybdeite is 169.1 ± 3.5Ma,suggesting the molybdenite metallogenic was taken place in the middle Jurassic.Using Os to trace the source of the molybdenite,show that it mainly come from earth crust and a small amount of mantle ingredients.Based on this study,we believe that biotite monzogranites and aplite granites have the close relationship to the deposit formation in the Huojihe mining area,and may related in the Pacific plate subduction and the flattening of the Songnen block and the Jiamusi block in the Jrassic.