Mineralogy characteristics of pyrrhotite and its implications for ore genesis of Dongguashan deposit in Tongling area
Sun Wenlong1, Ren Shenglian1, Zhang Junjie2, Song Chuanzhong1, Huang Fang3, Li Longming1, Li Jiahao1, Zhang Yan1, Liu Guoting1, Han Xu1, Wang Jingya1, Li Hailong1
1. School of Resources and Environment，Hefei University of Technology，Hefei 230009；
2. Metallurgical Geological Prospecting Bureau of East China，Ma anshan，Anhui 243000；
3. School of Earth and Space Science，University of Science and Technology of China，Hefei 230026
Pyrrhotite is one of the important ore mineral in Tongling Dongguashan deposit. The typomorphic characteristics of pyrrhotite not only reflect their own formation environment， also have implications for the genesis of the Dongguashan deposit. In this paper， we select the pyrrhotite ore samples in different layers of the deposit， using mineralography， X ray diffraction， electron probe to analysis the morphology， composition and standard type structure of pyrrhotite， to discuss the mechanism of its formation and using Fe isotope and S isotope analysis to investigate the ore—forming material sources of pyrrhotite. The research shows that： The pyrrhotite is mainly distributed in the middle of the ore body. According to metasomatic relations of pyrrhotite and its paragentic mineral， it was considered that the generated sequence of metal mineral is pyrite→ pyrrhotite→ chalcopyrite→ magnetite. X ray diffraction indicated that the pyrrhotite include the hexagonal system and the monoclinic system， the hexagonal system is more than monoclinic system. The phenomenon of the monoclinic pyrrhotite along edge of hexagonal metasomatism， shows the characteristics of hydrothermal metasomatism. Electronic probe test displays that the content of Fe element is 58.435％～60.978％， average value is 59.737％， the content of S element is 38.297％～39.891％， the average value is 38.696％， the molecular formula is Fe4S5～Fe9S10. It also shows that there are the hexagonal system and the monoclinic system， the individual particle component profile of pyrrhotite shows the core part is the hexagonal， the edge is monoclinic. δ34S of the pyrrhotite is distributed between -0.7％ to ＋13.5％，the overall distribution of δ57 Fe is 0.49‰～0.52‰，Fe and S isotopes show that they are all derived from the magmatic hydrothermal fluid in the region. It is indicated that pyrrhotite has magmatic and hydrothermal metasomatic genesis. We support that the Dongguashan deposit is a skarn deposit related to magmatic activity in Yanshan epoch.
Sun Wenlong,Ren Shenglian,Zhang Junjie et al. Mineralogy characteristics of pyrrhotite and its implications for ore genesis of Dongguashan deposit in Tongling area[J]. Chinese Journal of Geology, 2016, 51(3): 891-907.