Characteristics Of Ore Compositional Variation And Its Influence Factors Of Fluorite Deposits In Linxi Region, Inner Mongolia

The Linxi region of Inner Mongolia is located in the southern Greater Hinggan Mountains. Thisis a binding site between the Siberian plate and the Sino-Korea plate. Also, it is one of the importantfluorite ore district in eastern China. The major ore-hosting wall rocks are Late-Paleozoic andMesozoic volcanic-sedimentary rocks and Mesozoic granites, the main ore-controlling structures areNE-NNE and EW trending faults. According to the geological characterisics of fluorite deposits andthe extent of the ore composition variation, fluorite deposits can be divided into two types in thestudy area: the one has well-differentiated ore composition (I type) and another has badly-differentiated ore composition (II type). This paper systematically study based on the comparison ofthe macro-micro geologic features、geochemical features and characteristic of ore-forming fluidinclusions of two types of fluorite deposits and ores. The following five results and understanding areachieved:1. The research show the obvious ore-controlling geological condition difference between thesetwo types of fluorite deposits. I type main ore-hosting wall rock is volcanic-sedimentary rock andprincipal ore-controlling structures are NE-NNE trending faults. While II type main ore-hosting wallrock is granites and main ore-controlling structures are EW trending faults.2. On the aspect of the macro-micro geologic features, the ore mainly fluorite andquartz-fluorite of I type fluorite deposites, the fluorite mainly has euhedral-subhedral granulartexture. Massive. stipped and brecelated structure is developed and the ore grade is high; However,the ore mainly quartz-fluorite and fluorite-quartz of II type fluorite deposites, the fluorite mainly hasallotriomorphic-subhedral granular texture. Massive, veinlike-stockwork and speckle structure isdeveloped and the ore grade is low.3. On the aspect of the REE geochemical features, the ΣREE contents in fluorite of these twotypes of deposits are significantly higher than in quartz. II type is generally higher than I type. Boththe reducing and oxidizing ore-forming environment of I type can be shown by δCe and δEu. But IItype formed only in strongly reducing environment. The Y/Ho-La/Ho graph demonstrated that thequartz and fluorite in these two types of deposits represented the characteristics of horizontaldistribution, which illustrates the ore-forming fluids are homologous.4. On the aspect of the characteristics of ore-forming fluid inclusions, inclusions of I type represent characteristics of large particles, great quantity in fluorite and characteristics of poorlydeveloped, small particles and small quantity in quartz. While inclusions of II type representcharacteristics of relatively small particles and small quantity in fluorite and grew too badly to find inquartz. The microthermometric data show that the homogenization temperature of inclusions in Itype is131-289℃, representing the medium-low temperature deposits. However, the homogenizationtemperature of inclusions in II type is110-201℃, showing the low-temperature deposits. The salinityand density of ore-forming fluid are similar in these two types of deposits, belonging to thelow-salinity and low-density fluid. The ore-forming pressure of these two types has a large differenceand I type has relatively higher pressure. The composition of ore-forming fluid has similarcharacteristics that has mainly content of H2O and generally contain H2and C3H6in these two types.5. Through the comparative study on the macro-micro of two types of fluorite deposits and thencombining with the results of the geochemical characteristics of trace and rare earth elements andfluid inclusions analysis, this paper discusses some main factors that influence the differences of orecomponent differentiation in the fluorite deposits and suggests that fluorite deposit’s ore componentdifferentiation differences are mainly affected by ore-controlling tectonic conditions, secondly byore-hosting wall rock conditions.