Research Of Alteration Zone In Shimensi Tungsten Polymetallic Deposit

Shimensi tungsten polymetallic deposit is located within the northern margin of the Yangtze Craton, belong to Jiuling W, Sn polymetallic mineralization belt. Previous studies are insufficient to accurately analyze mineralization and metallogenic regularity, thus, the further research is very necessary. This study objected to Shimensi alterated wall rock, which can be divided into different zones and periods.The feature of the alteration?ineralization enrichment and element migration patterns are discussed here through the research of petrology mineralogy and geochemistry study.Jinning biotite granodiorite, Yanshanian porphyritoid biotite granite, Yanshanian fine grained biotite granite and Yanshanian granite porphyry are the main rock mass in Shimensi ore area. The mineralogy and geochemistry study indicate that Jinning biotite granodiorite and yanshanian granite are Si-reich, K-rich, subalkaline and peraluminous S-type granitoids.Various kind of wall rock alteration is extensive in Shimensi tungsten polymetallic deposit. Some of them are strong such as greisenization,sericitization silicification and potassic alteration. Chloritization is weak but common in this area. Greisenization and sericitization are closely associated with the mineralizationAlteration phases are classified in to thermal contact alteration in late magmatic stage and gasification hydrothermal alteration, high / low temperature hydrothermal alteration in post-magmatic stage. Alkali metasomatism occurs mainly in thermal contact alteration phase. Biotitization and sericitization are the main alteration in Jinning and Yanshan rock, inspectively in gasification hydrothermal alteration. Greisenization and chloritization are very common in igh / low temperature hydrothermal alteration. Geochemisty characteristics of magmatic rocks indicate its lithology is mainly granite and granodiorite rocks, which are belong to peraluminous calcium alkaline- alkaline series. REE gechemsitry study shows the similar distribution patterns in different type of wall rock, and also in the fresh and altered rock. All the patterns are right-wing type, relatively enriched in LREE, and Eu negative anomalies, indicating a similar material source and similar process.of magmatic crystallization, differentiation and evolution.Major elements geochemistry and its migration study indicate that greisenization altered rock are rich in SiO2, Na2 O, FeO, Fe2O3 and CaO, and depleted in K2 O and Al2O3 compared to fresh rock. SiO2, Na2 O, K2 O and CaO move into sericite biotite granite during alteration, while FeO and MgO move out. Overall, the granodiorite in external alateration zone losses SiO2, Na2 O and CaO; the greisenization porphyritic biotite granite in internal alateration zone gains SiO2, FeO, Fe2O3 and CaO and losses Na2 O and K2 O.Migration analysis of REE and trace element showed that the greisenization biotite granodiorite in external alteration zone exhibit moving in W, Cu and Mo, Zr, Hf, Rb, Zn and Ga, but moving out Sr, Cr and Pb, etc. W, Cu and Mo mineralization are very strong in greisenization stag.Sericite biotite granodiorite porphyry exhibits moving in Zr, Cr, Hf, U, Rb, etc., but moving out a small amout of V, Pb and other characteristics; greisenization porphyritic biotite granite gains Zr, Hf, U, Rb, Cr, Nb and losses V and Pb. Both of external and internal alateration zone have high ?REE, LREE and HREE value. Alteration and unaltered rock REE trend remained the same, LREE enrichment were tested negative Eu anomaly rightist type.