Study on Source, Transport and the Enrichment Mechanism of Iron in Iron Skarn Deposits

Iron skarn deposits are of global concern, due to its complicated metallogenic mechanism. It is also one of the most important types of high-grade iron deposits in China. The source, transportation and enrichment mechanism of iron plays an important role in the study of iron skarn deposits, which are highly controversial at present. Based on the compilation of recent studies, the complex and polygenetic characteristics of iron skarn deposits are described in this paper, the transport and precipitation process of iron is summarized and a process flowchart has been constructed. Then the most possible iron sources in different kinds of iron skarn deposits are then. Above all, it was found that the deposits related to intermediate-acid intrusion and probably gained their iron from shallow intrusions. Many cases showed that most of the iron probably came from iron-rich strata nearby for those skarn deposits that related to acid intrusion. However, not all of this type of skarn deposits were hosted in iron-rich strata. Therefore, the possibility of deep iron source is also discussed. Combined with the theory of magmatic skarn and the cogenetic alkali-rich intrusion, it is proposed that the possible model is on the activation of deep source iron, transportation and enrichment process. The iron enriched ore pulp, derived by the assimilation of deep magma and calcic rocks, was transported to the aureole between shallow intrusion and carbonates. The ore pulp met the hydrothermal fluid to form iron enriched complex hydrothermal fluid, which precipitated the iron ores with the change of physical and chemical conditions in the aureole.