Characteristics And Genesis Of The Yaogangxian Tungsten Polymetallic Deposits In Hunan Province

The Yaogangxian tungsten polymetallic ore-field is located in the central part of the Nanling metallogenic belt. In this ore field are distributed the Yaogangxian tungsten, Qingshanli lead-zinc and Heshangtan scheelite deposits and associated intrusion (Known as Yaogangxian intrusion).A detailed study on the Yaogangxian intrusion and Yaogangxian tungsten has been carried out, with focus on their origin and evolution process of the Yaogangxian intrusion and Yaogangxian tungsten.The following are major achievement obtained in this dissertation:1. The Yaogangxian complex intrusions are divided into three stages. The lithologies of the intrusions include medium-coarse-grained biotite granite formed in the first stage, fine grained granite in the second stage, and granite porphyry in the third stage. The zircon SHRIMP U-Pb isotopic ages are defined as 155.4±2.2Ma(MSWD=0.53),157.6±2.6Ma(MSWD=1.5),158.4±2.1Ma(MSWD=1.17) for the first, second and third stages of intrusions, respectively. The Yaogangxian tungsten and Heshangtan scheelite deposits are dated at (160±3.3) Ma (n=6, MSWD=2.7) and (158±1.2) Ma (n=7, MSWD=1.3), respectively, using molybdenite Re-Os isochron method. They are continuous geological event, and are important parts of the explosive regional event in Nanling area during (160±3.3)～(155.4±2.2) Ma.2. The Yaogangxian complex intrusions, showing the characteristics of S-type granite, being rich in ore-forming elements, is the parental rock, and also the centre of The Yaogangxian tungsten polymetallic ore-field. W mineralization is related with the first and second stages of intrusions. Compare with the first and second stages of intrusions, the third stage of intrusion have experienced weak fractional crystallization.3. The characteristics of sulfur isotope and Pb isotopic from ore, composition of mineral fluid inclusion and H,O isotope compositons inferred that ore-forming material of Yaogangxian tungsten, Qingshanli lead-zinc and Heshangtan scheelite deposits is from the Yaogangxian complex intrusions, and ore-forming fluids of Yaogangxian tungsten and Qingshanli lead-zinc deposit are transition type between magmatic water and magmatic water mixed with meteoric water from the early stage to the later stage.4. The Geological and Geochemical Characteristics indicate Yaogangxian tungsten, Qingshanli lead-zinc and Heshangtan scheelite deposits are closely related with Yaogangxian complex intrusions magmatic-hydrothermal system, are products of different types of ore mineralization at different locations of the intrusion resulted from the this magmatic-hydrothermal system.