Study On The Metallogenic System Of Copper-polymetallic Deposits In The Middle–southern Part Of Da Hinggan Mountains, China

There are lots of copper-polymetallic deposits in middle-southern part of Da Hinggan Mountains. It is an important non-ferrous metals base in north China. Based on the former data and materials, combined with field survey, and using the theory and methods of regional metallogeny and metallogenic systems, this paper has made systematically analysis and summary to the metallogenic rules of copper-polymetallic deposit in middle-southern part of Da Hinggan Mountains area.Middle-southern part of Da Hinggan Mountains area is situated on the east of Xilinhot micro-massif. It belongs to Late Paleozoic continental accretion belt between North China craton and Siberia craton. The activities undergone in the study area mainly including: miro-massif formation in neoarchean-early proterozoic; paleo-asian ocean continental margin accretion in Paleozoic; and paleo-pacific ocean subduction in Mesozoic. These activities caused the origin of volcanic-sedimentary rift trough in Early Permian, magmatic intrusions in Triassic, and volcano- magmatism activities in Jurassic-Early Cretaceous in the study area. These activities are closely related to the copper-polymetallic deposit, which formed three main systems of copper-polymetallic deposit: (1) Late Paleozoic-Mesozoic SEDEX deposition superimposed late hydrothermal metallogenic system, (2) Mesozoic structure hydrothermal metallogenic system, and (3) Mesozoic Yanshanian porphyry hydrothermal metallogenic system. And Mesozoic structure hydrothermal metallogenic system, which metallogenic space are extensional structures or cracks of different directions, is an important copper-polymetallic ore-forming system in the area.Based on the research of inner relationship of Da Hinggan Mountains area copper polymetallic metallogenic system, there are fellowing deposit types: terminal type, excessive type, hydrothermal sedimentation and volcanic hydrothermal sedimentation superimposed post hydrothermal transformation type. These have reflected the continuous evolution of mineralization.Based on the regional metallogenetic conditions and rules of ore formation, the origin, distribution and evolution of Cu-polymetallic deposits in middle-southern part of Da Hinggan Mountains are subject to volcanic sedimentation, tectonic movement, volcanic - magmatic activity and other factors.(1)There is no obvious choice for country rocks for the origin of Cu-polymetallic deposits. Most people think that Early Permian Dashizai Group are good country rocks for Cu-polymetallic ore deposits’origin in the past. But now I think that this idea has some limitations. Late Jurassic acidic volcanic rocks and subvolcanic rocks, which broadly distribute in the study area, are also of great potential to find large-scale hydrothermal vein-type Cu-polymetallic deposits in these strata. (2)Based on the structure of deposits, the faults of the North-West and North-East control the distribution of copper-polymetallic deposits, the conjunction of two direction faults are good place for the ore deposit origin.(3)Based on the Mineralization age, besides early stage of Yanshan, late stage of Yanshan and Indo-Chinese stage are very important stages for the origin of copper deposits. Especially the late stage of Yanshan, this stage belongs to the late stage of a regional scale magmatic activity, the conditions of large scale of magma hydrothermal copper-polymetallic deposits’s origin to be possessed. (4)From the regional distribution, there are mainly porphyry and hydrothermal vein-type copper-polymetallic deposits in the eastern slope of middle-southern part of Da Hinggan Mountains, mainly hydrothermal vein-type and contact metasomatic (skarn) type in the main ridges, hydrothermal vein-type, and volcanic - subvolcanic hydrothermal type in the western slope. I think that there is great potential to find large-scale porphyry Cu-polymetallic deposits in the east slope of study area; and volcano-volcanic hydrothermal polymetallic copper deposits in the western slope.(5)From the types of deposit, It is possible to be find such as contact metasomatism-porphyry type, volcanic hydrothermal sediment-porphyry type, hydrothermal vein-contact metasomatism type and volcanic hydrothermal sediment superimposed late Triassic or Variscan hydrothermal reformation type , Indo-Yanshan superposition hydrothermal dike type.Based on geological conditions of deposits formation and the distribution of geochemical anomalies, combined with Cu-polymetallic deposits and the evaluation results of potential resources, this paper has determined 11Ⅴ-grade Cu-polymetallic mineralization potential area, and has proposed prospecting targets. For exploration, for searching concealed deposits in depth, it is very important to using the metallogenic systems theory. It is very important to carry out geological samples and geochemistry samples using shallow drilling in cover area, and effective use of geophysical probing methods.