| The newly discovered Bangbule deposit is located in the western part of the Tibet Gangdise-Nyainqentangula Pb?Zn?Ag polymetallic metallogenic belt. Sphalerite is one of the main ore minerals of this deposit, and its chemical composition is of great significance to reveal physics-chemical conditions of mineralization and ore-forming fluids evolution. In this paper, different generations of sphalerite from the proximal and distal skarn of the Bangbule deposit have been studied in detail with microscopic observation and Electron Probe Microanalysis. Two generations of sphalerite (Sph-I, Sph-II) were distinguished with regard to their mineral associations, microscopic characteristics, and geochemical features. Sph-I mainly occurred in the proximal skarn, which is dark-red and co-exists with chalcopyrite, replace magnetite and pyrrhorite. The content of Fe is high (the Fe content of some sphalerite is more than 10 wt.%), and the Zn/Fe value is mostly less than 10. Sph-II can be subdivided into two types (Sph-IIa, Sph-IIb). Sph-IIa is brownish yellow in color and developed in both proximal and distal skarns. This generation sphalerite is usually filled in between skarn mineral grains (e g., pyroxene and garnet) and the fractures of those minerals, and the Fe content is obviously lower than that of the Sph-I. Sph-IIb is mainly developed in the distal skarn, which is light yellow and co-exist with galena and quartz, and Fe content is distinctly lower than that of the Sph-I and Sph-II. The estimation of Fe-in-Sphalerite thermometer shows that the mineralization temperatures from the Sph-I to the Sph-II (160℃~314℃, 138℃~157℃, respectively), which is consistent with the results of Zn/Fe ratios of sphalerite. Based on the above features, it is suggested that the early ore-forming fluids in the Bangbule deposit are of high temperature and rich in Fe, Mn, Cu, etc. As the temperature of ore-forming fluid decreases gradually, the content of Fe and Mn in the fluids decreases significantly. Spatially, the temperature and oxygen fugacity of the ore-forming fluid gradually decreased during the migration from northwest to southeast of the deposit, and indicating that there is potential to find distal Manto-type ore-bodies in the southeast direction of the deposit. |