Genetic Mineralogy Of Magnetite In Handan-Xingtai Area,South Taihang

The study area is located between Handan City and Xingtai City in Hebei Province.The tectonics is located in the central part of the North China Craton and the southern part of the Mesozoic Taihang Mountain tectonic-magmatic belt.There are a large number of basic and alkaline intrusions,rich in mineral resources,is China' s large skarn iron ore-rich areas.The area is divided into eight major rock bodies from west to east.According to the metallogenic scale,it is divided into strong metallogenic rock mass,weak metallogenic rock mass and none metallogenic rock mass.The strong metallogenic rock mass includes Kuangshan rock mass,Wu ' an rock mass and Qicun rock mass.The weak metallogenic rock mass is Fushan rock mass,and the none metallogenic rock mass is Guzhen rock mass.This paper mainly focuses on the Fushan rock mass,Guzhen rock mass,mine rock mass and Wu ' an rock mass in the western and central metallogenic belt.Based on the field geological survey,detailed lithofacies observation is carried out to determine the relationship between magnetite and various symbiotic minerals,and the samples with typical characteristics are selected for experimental test and analysis.According to the composition characteristics,the differences between strong metallogenic rock mass,weak metallogenic rock mass and non-metallic rock mass in Hanxing area are revealed.At present,the main technical means used are EPMA and LA-ICP-MS to determine the main and trace elements of magnetite,and the data are analyzed and processed by SPSS,SIMCA and other statistical software.It is difficult to distinguish the four rock masses by mapping the main element data of magnetite according to the rock mass according to the genetic discrimination diagram,most magnetite is magmatic magnetite,and a small part is hydrothermal origin;according to the principal element covariant diagram,Wu ' an and Kuangshan rock bodies have high Ti characteristics,indicating that the metallogenic temperature is high,but the overall lithology of Wu ' an rock body shows as monzonite and quartz monzonite,and the overall lithology tends to be acidic;according to the box diagram,the content of V in the Wu 'an pluton is the highest,indicating that the mineralization is in a low oxygen fugacity condition and has high Mn and Mg characteristics,which may be formed by the replacement of Mg-rich and Mn-rich hydrothermal fluids in the late magmatic magnetite.SIMCA model fitting shows that the Kuangshan and Wu 'an rock mass with strong mineralization degree have high Ti,Mg and Mn characteristics,while the Fushan rock mass with poor mineralization and Guzhen rock mass with almost no mineralization show high V and Cr characteristics.The characteristics of trace elements in magnetite show that high field strength elements(HFSE)are depleted and lithophile elements are enriched.High field strength elements mainly occur in accessory minerals,which are relatively stable and difficult to migrate.The overall characteristics of rare earth elements show that the content of ? LREE is higher than that of ? HREE,and Eu is weakly depleted.However,some mines and Wu 'an plutons show obvious positive Eu anomalies,indicating that they are affected by late hydrothermal processes.The wide distribution of rare earth elements in the magnetite in the mine rock mass indicates that the magnetite has two genetic types.Since Eu is a variable element,the change of its content can reveal the change process of oxygen fugacity in the mineralization process from the side,so the magnetite in the Kuangshan rock mass has trend from magmatic type to hydrothermal type.In summary,the Kuangshan and Wu ' an rock mass with the largest mineralization intensity have higher oxygen fugacity and temperature characteristics,while the oxygen fugacity and temperature content of Fushan rock mass and Guzhen rock mass with poor mineralization scale are relatively low.The temperature and oxygen fugacity can be used as an important indicator to determine the mineralization intensity.