Geological Characteristics And Genesis Of The Huogeqi Copper Mine In Inner Mongolia

Huogeqi copper mine is located in the Langshan metallogenic belt of the western part of the northern margin of the North China Craton.The tectonic settings are the Langshan Baiyunebo platform margin depression belt and the north wing of Langshan zhertai mountain fold fault bundle Langshan complex anticline.In this paper,based on the collection and collation of geological data such as regional geological background,geological characteristics of the deposit and field geological investigation,combined with the study of the geochemical characteristics of the deposit,we have a further understanding of the genesis of Huogeqi copper deposit,and put forward a new viewpoint on the genesis of the deposit.The Huogeqi copper deposit is located in the second rock formation of the Neoproterozoic Langshan Group.The ore bearing rocks are mainly banded quartzite.The ore body is layered,quasi layered,locally lenticular,and the occurrence is basically consistent with the surrounding rock.There are mainly chalcopyrite,pyrrhotite and pyrite in the copper ore.Gangue minerals are mainly quartz.The ore structures are mainly heteromorphic grain structure,etching structure,intergrowth edge structure,metasomatic residual structure and so on.Ore structure includes banded structure,reticulated vein structure,massive structure and breccia structure.The U-Pb zircon dating of the ore bearing banded quartzite shows that the lower limit of the formation age of quartzite is 1337 Ma,which restricts the formation of the Huogeqi copper deposit no later than 1337 Ma.Hf isotopic analysis of zircons from banded quartzite shows that zircons with U-Pb ages ranging from 1450Ma to 1660Ma are derived from new crustal materials,while zircons with U-Pb ages which is greater than 1700Ma are mainly derived from reconstruction and recycling of old materials.In addition,zircon U-Pb dating of the copper bearing skarn has been carried out.The sulfur isotopic analysis of pyrrhotite shows that?³⁴S value is 7.4‰?11.5‰,and the average value is+9.2‰,which indicates that the ore-forming sulfur comes from sea water.The study of fluid inclusions shows that the fluids during the hydrothermal transformation are aqueous inclusions,CH₄-H₂O inclusions and pure CH₄inclusions.The composition of ore-forming fluid is CH₄-H₂O system,and the fluid is immiscible in the process of migration.In addition,this paper also makes a comparative study on the characteristics of the copper deposit and typical copper deposits home and abroad,and makes a brief analysis on the metallogenic model.In this paper,it is considered that Huogeqi copper deposit and typical marine sandstone type copper deposit have similar characteristics.The enrichment of copper mainly occurs in the stage of sedimentary diagenesis.The ore-forming environment is redox.The metallogenic stages are mainly divided into sedimentary metallogenic stage,hydrothermal transformation stage and supergene oxidation stage.In conclusion,it is considered that the Huogeqi Copper Deposit in Inner Mongolia is a kind of marine sand-stone type copper deposit with sedimentary modification.