Geological Features And Molybdenite Re-Os Age Of Majizhang Molybdenum And Tungsten Bailanggou, The Center Of Jiang Xi Province

Majizhang molybdenum and tungsten bailanggou is located in Le'an county, Jiangxi province, the eastern of China. Is is next to the largest volcanic type uranium deposit in that field of our country, Xiangshan uranium ore-field deposit. The bailanggou was discovered in 1950 s. Although former has carried out the exploration work, but the basic geological research is slightly weak, especially in metallogenic epoch, metallogenic mechanism and material source etc. In this paper, after the geological characteristic, petrology and mineralogy, geochemical characteristics of the host rock and rare earth element determination, Re-Os isotopic determination of molybdenite in majizhang molybdenum, looking forward to offer help on ore genesis and geological prospecting. In short, the following achievements have been achieved.(1) Through research on petrology and mineralogy of the host rock in Majizhang bailanggou, two kinds of granite are found spread across the bailanggou. They are caledonian coarse-grained biotite monzogranite and yanshanian alkali feldspar granitelle.(2) There is a similar characteristic between coarse-grained biotite monzogranite and alkali feldspar granitelle:(1) silicon-enriched,alkali-enriched,potassium-enriched and peraluminous.(2) trace element is consistent with rare earth element,which are all display LREE enrichment right deviation distribution pattern.(3) in the picture of plumbum tectonic pattern, the two kinds of the host rock are located between crustal evolution curve and orogen evolution.(3)The source rock of two kinds host rock are all from the upper crust and the products of comagmatic evolution.(4) There are two kinds of molybdenum in bailanggou,one is the greisenization molybdenite,and the other one is the quartz vein type molybdenite. The two kinds of rare earth element of molybdenum have a same characteristic:Eu shows obvious negative anomaly and the distribution curve shows LREE enrichment right the seagull.(5) Re-Os isotope dating shows that the mineralization ages of the greisenization molybdenite are between(183.72 ±2. 47)Ma and(161.71 ±21.78)Ma,came into being in middle Jurassic,the mineralization ages of the quartz vein type molybdenite are between(161.33 ±2. 85)Ma and(157.14 ±1.73)Ma,came into being in early Jurassic. There are two metallogeny stages in Majizhang bailanggou, the early mineralization is greisenization type in early Jurassic, and the later is quartz vein type in middle Jurassic.(6) The mineralization mechanism of the study area may be summarized as follows: the greisenization of mineralized surrounding rock ? the early greisenization polymetallic mineralization ? the late quartz vein type polymetallic mineralization.in which polymetallic is the prerequisite of the study area. The fearly greisenization polymetallic mineralization is the basic and the late quartz vein type makes the polymetallic mineralization mineralization came true.