Geological Characteristics And Prospecting Direction Of Gaoletu Crystalline Graphite Deposits In Urad Middle Banner,Inner Mongolia

The study area is located in Xinhure Sumu,Urad Middle Banner,Inner Mongolia.The tectonic position belongs to the Langshan-Bayan Obo platform margin depression of North China platform.Inside the margin depression,accumulated deep terrigenous clastic rock,muddy mudstone rocks and carbonate rocks,which provides a material basis for the formation of graphite ore.Gaoletu graphite is located in the Au,Ag,Cu,Fe,REE,Pb,Zn,W,graphite,and muscovite metallogenic belts in the northern margin of North China.The strata exposed in the area are mainly the the Sertengshan group of the New Archean and the Baiyunebo Group of the Middle Proterozoic,while the graphite ore body is produced in the Baiyunebo Group.The Baiyunebo Group is a set of huge shallow metamorphic rocks,which are carbonaceous slate,schist,metamorphic sandstone and carbonate rock.Magmatic rocks have been exposed from the Neoarchean to the Triassic,and the decisive role for mineralization is the Permian biotite granite.Affected by Bayan Obo-Hoya jurdo-Bodin goer fault zone near the east-west,a series of secondary faults are formed,which provide favorable channels for magmatic hydrothermal rise during the mineralization period.There is only one ore body in the graphite deposit,which is a single graphite deposit.The graphite ore body is located in the graphite two mica schist of the Jianshan Formation,and the thickness is stable.The surrounding rock of the roof is the biotite plagioclase K-feldspar gneiss of the Liushugou Formation,and the bottom plate is the metamorphic quartz sandstone of the Jianshan Formation.Through systematic sampling analysis,the fixed carbon content of graphite deposits is at least 3.00%,the highest is 18.30%,the average is 5.1%,and the mineral content is 15.8088 million tons,which has reached an extra large scale.Under the microscopic observation,the distribution of graphite has two forms,scaly and sparse,and the coexistence of the two forms indicates that the temperature and pressure are unstable during mineralization.After SEM scanning analysis of 208 polished thick sections,the graphite sheet is between 0.02 and 0.3 mm,and the larger the sheet size.The study on the relationship between rock mass and graphite mineralization found that the fixed carbon content of the ore body near the rock mass and the vein rock side is higher than the fixed carbon content away from the rock mass side,and the graphite crystallisation degree is also good.Through the recovery of the original rock of the graphite ore,the original rock is a set of terrestrial clastic rocks of aluminum-rich carbonaceous mudstone,argillaceous siltstone,sandstone and carbonate rock.The carbon isotopes in graphite minerals are analyzed.The ?13C value is between-27.78‰ and-29.13‰,and the average value is-28.61‰.The value does not change much,and the concentration and deviation are small,which can be judged that the source of graphite is organic carbon.When the original rock undergoes regional metamorphism,accompanied by the increase of temperature and pressure,the organic carbon is gasified and precipitated when the metamorphism reaches the low green schist facies.Under the closed reducing condition,the organic matter metamorphoses and crystallizes to form graphite.This also laid the foundation for the formation of the deposit.With the large amount of heat brought by the intrusion of Early Permian biotite granite,the originally formed graphite recrystallized under the thermal contact metamorphism,forming the current graphite deposit.The formation time of the deposit is subject to the intrusion era of biotite granite.The formation time of biotite granite is 267.9~284.7Ma,which belongs to Early Permian.After all,the graphite deposit is also a metamorphic deposit,different from the typical regional metamorphic deposits and contact metamorphic deposits,but a type of deposit between the two.Through the ore-forming geological characteristics and ore-forming genesis of the Gaoletu crystalline graphite ore.The ore-forming age of graphite ore is the late Hualixi,and the occurrence of the horizon is the Baiyun Obo group.In this era and the horizon,several large graphite deposits and gold deposits have been discovered.The strata and magmatic rocks are the main breakthroughs in the prospecting direction.The contact sites between the carbonaceous strata and the Early Permian acid magmatic rocks in the Jianshan Formation of the Bayan Obo Group can be used as important prospecting clues.