Relationships And Distributing Disciplinarian Of Ore-forming Elements Of Tongkeng Indium-rich Tin-polymetallic Deposit

The well-known Tongkeng deposit, which located in Danchi metallogenic belt of northwest Guangxi, is particularly rare in the world due to abundant dispersed elements and huge reserves. It is formed with cassitente sulfide type tin polymetallic ore bodies on the upper part and skarn type zinc-copper ore bodies in the deep. The paper study on mineral assemblage, ore-controlling structure and geochemical feature of mineral elements, and according to EMPA data and ICP-MS data of sphalerite, element distribution and element correlation have been discussed, and some results and understandings can be concluded as follows:(1) According to EMPA data and ICP-MS data of sphalerite, there are some element of Fe, Cd, Pb, In, Sn, Cu and Ga in Tongkeng deposit, whether tin-polymetalic ore bodies on the upper part or Zinc-Copper ore bodies in the deep. The tin polymetallic ore bodies are rich of Sn(EMPA:0～0.05%; ICP-MS:3556～4707 ×10-6) and In(EMPA: 0.02～0.19%; ICP-MS:348～913×10-6), but are relatively poor of Cu(EMPA:0.03～ 0.26%; ICP-MS:862～2969×10-6), while Zinc-Copper ore bodies are rich of Cu(EMPA:0～0.76%; ICP-MS:3968～22250 ×10-6) but relatively poor of In(EMPA: 0～0.02%; ICP-MS:51.7～551×10-6). So the element of Sn and In are mainly enriched in tin-polymetalic ore bodies while the element of Cu is mainly enriched in Zinc-Copper ore bodies。(2) Zn and Fe is negatively correlation due to isomorphism of sphalerite; Sn and Cu is positive correlation, they get into sphalerite while Zn is replaced; In and Ga is negatively, which can be showed that enrichment in different temperatures and different pressures are on the contrary.(3) The element of In and Sn migration in the form of chloride anions,while separate in the precipitation process,and then occurred in sphalerite with Zn substituted in the form of isomorphism.(4) According to analysis of EMPA data and microscope observation, it can be inferred that with Cd-contained sphalerite in early stage replaced by Cu-rich fluid in later stage, which related to magma. The’skelecton’of sphalerite can be found for some sphalerite recrystall in chalcopyrite.(5) The characteristics ratios of In/Sn,Zn/Sn,Zn/Cd,In/Ga and so on in tin polymetallic ore bodies and zinc-copper ore bodies are similar, which indicate two types of ore bodies belong to a set of metallogenic system and they are products of terminal magmatic hydrothermal.(6) Prospecting for tin should pay attention the position of In-rich sphalerite in tin-polymetallic ore bodies, especially on the edge of tin-polymetalllic ore bodies; For the copper prospecting work should focus in the deep, especially the position close to the relative enrichment place of granite, or sphalerite and pyrrhotite.