Genesis and geological significance of ilvaite in the Jinchanghe Fe-Cu-Pb-Zn skarn type polymetallic deposit, Baoshan block, western Yunnan
Ilvaite is a common mineral in skarn-type Pb-Zn and Fe deposits, and is closely related to lead-zinc ore bodies and magnetite ore bodies. To identify the relationship with lead-zinc-iron-copper polymetallic mineralization during ilvaite mineralization, this paper investigated the production environment, mineral symbiotic assemblage, chemical composition and ilvaite zonation in the Jinchanghe Fe-Cu-Pb-Zn skarn type polymetallic deposit. The mineral chemical composition by EMPA showed that the molecular formula of ilvaite in the Jinchanghe mining area is Ca0.95-1.08 (Fe0.87-1.97Mn0.08-0.36Mg0.01-0.06 )2+(1.89-2.03) (Fe0.82-1.04Al0.01-0.03)3+(0.88-1.15)(Si1.94-2.08O7)O(OH). Combined with the type of mineral assemblage, occurrence, zoning characteristics, etc., it was inferred that the skarn in the deposit will gradually metasomatize from the inner zone to the outer zone. Three mineral symbiotic combinations were identified in Jinchanghe mining area: ilvaite+magnetite combination, ilvaite+magnetite+pyrite+chalcopyrite combination, ilvaite+galena+sphalerite+chalcopyrite combination. These mineral assemblages correspond to three different alteration stages: the later skarn stage (representative assemblage Ⅰ), which is dominated by the decomposition of garnet, forming a large number of ilvaites; the retro-alteration stage (representative assemblage Ⅱ) where mainly actinolite, chalcopyrite, and pyrite developed; at the quartz-sulfide stage (representative assemblage Ⅲ), ilvaite was further decomposed to form quartz, calcite, magnetite, etc. In addition, the distribution pattern of rare earth elements in ilvaite is similar to that of garnet, which retains the characteristics of rare earth elements in garnet to some extent. It is believed that ilvaite is the product of the degradation and decomposition of early garnet, and the ore deposit is gradually metasomatized from the inside to the outside, forming a Mn-rich ilvaite in the lead-zinc-copper ore body and manganese ilvaite in the magnetite ore body banding feature. Mn-rich ilvaite is conducive to the formation of lead-zinc ore, and has an influence on the depletion of magnetite ore bodies and copper ore bodies. Meanwhile, it can also provide important scientific significance for the mining area to expose neutral acid rock and deep prospecting.
万方数据
维普
