| 宁芜型铁矿床成因和成矿模式的探讨 |
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| 引用本文：.1990.A discussion on genesis and metallogenic model of Ningwu-type iron deposits[J].Mineral Deposits,9(1):13~25,48 |
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| 中文摘要:文章以充分事实和大量资料探讨宁芜型铁矿的形成及其与气化一热液交代蚀变的关系，系统地论述了上升的成矿溶液在水/岩反应过程中所造成的交代蚀变分带和成矿及其有关元素活化转移和富集的规律，进一步强调热液一交代蚀变成矿模式的重要意义，并着重指出内生成矿作用与外生物质在宁芜型矿床形成过程中的密切联系。 |
| 中文关键词:钠交代 蚀变分带 成矿模式 膏盐层 |
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| A discussion on genesis and metallogenic model of Ningwu-type iron deposits |
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| Abstract:The Ningwu-type iron deposits, which are well-known to Chinese geologists, can be dhrided into some distinctive subtypes, such as 1) Aoshan subtype(actinolite-apatite-magnetite assemblage); 2)Taocun subtype(disseminated actinolite-apatite-magnetite); 3)Meishan subtype (scapolite -garnet-diopside-magnetite); 4)Jishan subtype(disseminated scapolite-albite-epidote-magnetite); and 5)Fenghuanshan subtype(lithostratigraphically-controlled Carbonate-magnetite-hematite). Being genetically related to Mesozoic gabbrodiorite and diorite porphyrites and having many similarites to porphyry-type deposits, these deposits are generally called porphyrite iron deposits. Although these deposits have been intensively investigated and explored for many years, their geneses have long been controversial as to whether they are of magmatic or pneumato-hydrothermal origin. Based on detailed field and laboratory investigation, this paper disscusses the sources of ore-forming elements and extractors such as H2O, Na+, Cl, CO and SO42-, the reactions between rocks and ore-forming fluids, factors for their mobilization and concentration. The authors lay emphasis on the metallogenic model related to metasomatic alteration. Every investigator has admitted the fact that there are ubiquitous and intense hydrothermal alterations and regular zonation in all of the Ningwu-type iron deposits. The vertical zonation of alteration can be seen within a distance of some hundred to a thousand meters. Three main stages (from early to late) and zones(from bottom to top)have been recognized, which include 1)soda metasomatism forming albitized zone; 2)ironmagnesium-calcium metasomatism forming iron bodies and mela-altered zone; 3)acid or hydrogen metasomatism forming 1euco-altered zone including silicified, alunitized and argillic zones. The Triassic evaporites in the basement of the Ningwu volcano-sedimentary faulted basin are of great importance to the formation of the Ningwu type iron deposits. These evaporires ate thought to have provided mineralizers or extractors for the convective hydrothermal fluids centered on aporphyrite intrusive, giving rise to hot and highly saline brines or ore-forming fluids, These fluids wouJd react upon the rocks(porphyrite and its country rocks), resulting in albitization which was essential to iron mineralization. |
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