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Characteristics And Metallogeny Study Of Hemushan Iron Deposit In The Southern Part Of Ningwu Ore Cluster District

Posted on:2016-10-12Degree:MasterType:Thesis
Country:ChinaCandidate:Y W JiangFull Text:PDF
GTID:2180330461993631Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
The Hemushan iron deposit, which is located in the Zhonggu ore field in the southern part of Nanjing-Wuhu large ore-cluster district, is a typical medium-sized porphyrite iron deposit of the Yangtze River metallogenic belt. The major orebodies occur as layers and lens in the contact zones between dioritic pluton and Mid-Upper Triassic carbonate strata and their nearby country rock. Field investigation, microscopic observation, and mineralogical and geochemical analysis have been carried out on the Hemushan iron deposit, with a focus on an analysis of ore deposit characteristics and mineralization processes.Field investigation and microscopic observation indicate occurrence of orebodies of the Hemushan iron deposit mainly in the contact zones between dioritic pluton and Middle Triassic carbonate strata of the Zhouchongcun Formation and their nearby country rock, and sometimes at the disconformable surface between the Huangmaqing and Zhouchongcun Formations or in the dioritic pluton. The ore can be divided into two types, with mineral assemblages of actinolite – apatite – I type magnetite and edenite – phlogopite – II type magnetite. Mineralogical analyses indicate that edenite contains more Al and Na, and less Si than actinolite, and type II(coarse-grained vein) magnetite contains more Ti and Al, and less Mg than type I(disseminated) magnetite. These data show that the metallogenic temperature of the edenite – phlogopite – II type magnetite assemblage is higher than that of the actinolite – apatite – I type magnetite assemblage.Alteration and mineralization have a significant zoning, occurring from pluton to strata: dioritic porphyrite â†' sodium-metasomatic dioritic porphyrite â†' phlogopite – actinolite rock â†' actinolite – apatite – I type magnetite ore â†' edenite – phlogopite – II type magnetite ore â†'( tourmaline) – edenite – phlogopite( breccia) rockâ†'( actinolite) – phlogopite rock â†' marbleized limestone / hornstone â†' limestone / sandy shale. Geological investigation and petrographic observation support division of formation process of the deposit into pre-metallogenic, major metallogenic, and post-metallogenic periods. The pre-metallogenic period consists of albite stage with intensive replacement of plagioclase by Na-feldspar. The major metallogenic period includes actinolite – apatite – I type magnetite, edenite – phlogopite – II type magnetite, and hematite stages. The actinolite – apatite – I type magnetite stage is characterized by formation of the coarse-grained vein magnetite ores, and the edenite – phlogopite – II type magnetite stage by formation of the disseminated magnetite ores. The post-metallogenic period is further divided into quartz – pyrite and carbonate stages. The quartz – pyrite stage is characterized by occurrence of more pyrite and less quartz, and the carbonate stage by superimposed reform of previous minerals by calcite.The information obtained in this thesis supports an origin of the Hemushan iron deposit via medium-high temperature gas-liquid matasomatism and filling. The actinolite – apatite – I type magnetite ore was formed by hydrothermal metasomatism, and the edenite – phlogopite – II type magnetite ore by hydrothermal filling.
Keywords/Search Tags:porphyrite iron deposit, ore deposit geology, ore deposit geochemistry, metallogeny, Hemushan in Ningwu district
PDF Full Text Request
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