Study on indium occurrence state and enrichment patterns in the Xianghualing Sn-Pb-Zn orefield in southern Hunan

Indium ( In), as a typical dispersed element, is extremely difficult to form an independent deposit, which is usually enriched in Sn-Pb-Zn polymetallic deposits as an associated component. Xianghualing orefield hosts abundant resources of Sn, Pb, Zn, and is a potential area of In resources in China. However, the occurrence state, distribution regularities and mineralization potential of In in the Xianghualing orefield are still unknown. In view of this, this paper takes three large and medium-sized tin polymetallic deposits (i. e., Xinfeng, Tieshaping and Chashan) in Xianghualing area as the research object. Based on detailed field geological and mineralogical research, ICP-MS, EPMA and LA-ICP-MS are applied to systematically carry out whole -rock geochemistry, sphalerite mineral chemistry and in -situ micro -element geochemistry research. Our results show that, In is mainly enriched in sphalerite in the form of homomorphism, and the possible replacement mechanism is In3+ + Cu+ <-> 2Zn(2+). The enrichment degree of In within different deposits is significantly different, among which, Xinfeng ore is the highest (average grade 213. 7g/t), Tieshaping is low, and Chashan is the middle. In addition, when the Cd content of sphalerite ranges from 5000 x 10 (-6) to 7000 x 10(-6), the corresponding In content increases sharply to 1000 x 10(-6) and above. All the analyzed sphalerite samples from the Xianghualing orefield is enriched in Fe, Mn, In and other high -temperature elements, but significantly depleted in Ga and Ge and other low -temperature elements. By comparison, it is found that the elemental composition of sphalerite is very similar to that of typical middle -high temperature magmatic-hydrothermal deposits ( such as distal skarn type deposits). Combined with the geological thermometer of sphalerite, the formation temperature of sphalerite is estimated to be 345 similar to 372 degrees C, and the Xinfeng deposit is slightly higher than the other two deposits. In summary, we believe that the concentration of In is mainly controlled by temperature, that is, the closer to the granitic intrusion, the higher the temperature of sphalerite, the more enriched In. Combined with previous studies, it is estimated that the amount of associated In resources in Xianghualing ore field is more than 15,000t, with huge potential economic value. It should be recycled in the future.