Characteristics And Genesis Of Au-Mo Mineralization In Wudaogou Area,Heihe County,Heilongjiang Province

The Wudaogou area is located in the low mountain-hill area near the Dahei Mountain in the lesser Hingan region and the southeast of Xing'an block in the east of Central Asian Orogenic Belt.The west of Wudaogou area is close to the famous Duobaoshan-Tongshan large-medium porphyry copper deposits in eastern Jihei.Based on field geological surveys,we carried out a comprehensive study of the geological and mineralization characteristics,fluid inclusions,and geochronology of the Auand Momineralization in this area,and then discussed the genesis and metallogenic tectonic setting of the Auand Momineralization combined with regional geological tectonic evolution in this work.And the Auand Mometallogenic model have been established.The details are as follow:Momineralization is the porphyry mineralization.There are mainly Veinlet-dissemination type Moore.The hydrothermal alterations show the typical alteration zoning characteristics of porphyry system.A core of potassic alteration forms early and is surrounded by a propylitic alteration halo and sericitization halo.According to mineral paragenesis and vein crosscutting relationships,the mineralization is divided into four stages: Mo?,quartz-pyrite stage;Mo?,quartz-molybdenite stage;Mo?,quartz-polymetallic sulfide;MoIV,calcite-poor sulfide stage.From the early to late stage,the ore-forming fluid gradually transformed from the high temperature?380?390??high salinity?7?48 wt.% NaCl eqv.?NaCl-H₂O system fluid dominated by magmatic water to low temperature?190? 200 ??and low salinity?0?2wt.% NaCl eqv.?NaCl-H₂O system fluid with a mixed magmatic meteoric origin.The estimated ore-forming pressures are 151?254bars.The deposition of Mowas controlled by the boiling occured in Mo? and MoII stages.while the late mineralization was related the mixing of meteoric water and the decrease in fluid temperature and salinity.Aumineralization is the intrusion-related hydrothermal vein type mineralization.The orebodies are strictly controlled by NE-striking faults.The hydrothermal alteration types are mainly chloritization and sericitization,the minor types are epidotization and carbonatization.According to mineral paragenesis and vein crosscutting relationship,the mineralization is divided into four stages: Au?,quartz-pyrite-chalcopyrite stage;Au?,quartz-polymetallic sulfide;Au?,calcite-poor sulfide stage.From the early to late stage,the ore-forming fluid gradually transformed from the medium-high temperature?corrected ore-forming temperature is 320?360??high salinity?4?8 wt.% NaCl eqv.?CO₂±N₂-NaCl-H₂O system fluid dominated by magmatic water to low temperature?200?210??and low salinity?0?2 wt.% NaCl eqv.?NaCl-H₂O system fluid with a mixed magmatic meteoric origin.The estimated ore-forming pressures are 824?1012 bars.The deposition of Auwas controlled by the effervescence occured in AuI stage,while the late mineralization was related the mixing of meteoric water and the boiling.The Momineralization is genetically related with the alkali granite.The results of U-Pb geochronology for the alkali granite show that the weighted mean age of the rock is 270.4±1.6Ma.The alkali granite of Wodaogou area belong to High Aluminium high potassium calc alkaline A-type granite,imply that the metallogenic tectonic setting is post-orogenic extension related to Paleo-Asian Ocean collision.The Aumineralization is genetically related with the diorite.The results of U-Pb geochronology for the diorite show that the weighted mean age of the rock is 240.6± 1.5Ma.The diorite of Wodaogou area belong to metaluminous high potassium calc alkaline diorite,and are characterized by enrichment in large ion lithophile elements?LILEs;e.g.Rb,Ba,and K?and in light rare-earth elements?LREEs?,and by depletion in high field strength elements?HFSEs;e.g.Nb,Ta,and Ti?,revealed that the gold mineralization was formed under the background of the Mongolia-Okhotsk Ocean continuously subducting towards Northeast China.In summary,Comprehensive researches indicate that the Wodaogou metallogenesis are divided into two-stages metallogenesis:?1?the Permian porphyry-type Momineralization formed under post-orogenic extension background related to Paleo-Asian Ocean collision,and?2?the Triassic intrusion-related hydrothermal vein type Aumineralization formed under the background of the Mongolia-Okhotsk Ocean continuously subducting towards Northeast China.