Study On The Metallogenic Mechanism And Char Acteristics Of Ore-Forming Fluids Of Limu Tin Polymetallic Deposit, Guangxi

Limu tin polymetallic deposit is one of the most important tin-polymetallic deposits in south china, which include rare altered granite type deposits. The study on ore-forming fluid is not so much in this mining area so far. The characteristics, source of ore-forming fluid and the relationship between mineralization and regional tectonic evolution should be studied further.Based on the previous data and detailed field research in Limu tin polymetallic deposit, the sources of metallogenic material, ore-forming fluid and metallogenitc mechanism were studied by fluid inclusion, noble gas, rare earth elements and stable isotope in this paper. The results were sumarrized as follows.(1)Limu granite intruded from late Indosinian to early Yanshanian. mineralization occoured in late Indosinian and early Yanshanian two periods. The tectonic-metallogenic setting appears to related with the extensinal geodynamic background in lithosphere.(2)The studies on fluid inclusions wraped in quartz indicated that metallogenic temperature includes early medium-high temperature stage (230～500℃) and late intermediate temperature stage (90～260℃). The metallogenic temperature of altered granite type deposit is300～400℃. The temperature of sulfide and carbonate formed at intermediate temperature stage. The salinity is from0.6to9.0wt%NaC1with a low destiny fliud.(3)The noble gases isotopic components of fluid inclusions wraped in pyrite were tested in this paper. The results sumarrized as follows:3He/4He ratios are from0.14to0.97Ra,40Ar/36Ar ratios are from555.98to855.11,20Ne/22Ne ratios are from9.671to9.748,21Ne/22Ne ratios are from0.0306to 0.0330. It is suggested that mantle fluids were involved in the metallogenic process.(4)The magma brought a large number of metallogenic material and thermal energy. These energy lead to the activation, migration and enrichment of Sn, W, Nb and Ta. The occurrences of orebodies were controlled by structure, host rocks and metallogentic temperature.