Geochemistry of Tieshan Iron Deposit in the Wuyang Area, Henan Province and Its Environmental Implications
详细信息
- 责任者：Li Yongfeng (Non-Ferrous Mineral Exploration Engineering Reseach Center of Henan Province ; Zhengzhou 450016 ; China) ; Xie Kejia
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(9)
- 关键词：铁矿 ; iron ores ; 河南 ; Henan Province
- 页码：p.1377-1398
- 图表：16 illus., 7 tables, 52 refs.
- 分类号：1001
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
Located in the Wuyang area of Henan Province and geotectonically on the southern margin of the North China Craton,the Tieshan banded iron formation（BIF）constitutes a large iron deposit of Anshan type formed in NeoArchaean.In this paper,petrology and geochemistry of Tieshan BIF were studied and a comparison was made with other BIF in the world.Systematic chemical analyses of wall rocks and ores indicate that the banded iron formation might have been related to marine volcanic-sedimentary volcanic rocks,and the ore deposit probably belongs to the Precambrian volcanic-sedimentary metamorphic iron deposit.The homogenization temperatures of fluid inclusion show a peak at 120360℃for the wall rock and 120320℃for the ore,and the ore-forming fluids have low salinity（1%14%）and low density（0.751.00g/cm3）.Ore-forming fluid is a kind of low salinity water of Na+,Ca2+,SO42-,Cl-,and contains high amount of CO2 and small quantities of O2,N2 and CH4.Petrological studies show that the BIF suffered greenschist facies to low amphibolite facies metamorphism and part of the magnetite was recrystallized whereas the other part of the magnetite preserved the characteristics of chemical sediments.In the diagram of TFe-（CaO+MgO）-SiO2,Tieshan BIF has a consistent distribution area with Anshan BIF and Wutaishan BIF and other BIF in the world.The REE contents of Tieshan BIF are low,showing characteristics of marine sediments in Archean.In the PAAS-normalized REE pattern,LREE are depleted and HREE are enriched relatively,with obvious Eu positive anomaly（Eu/Eu*=0.302.21）,obvious Y positive anomaly（Y/Y*=1.343.19）and visible La positive anomaly（La/La*=0.811.60）,slightly negative Ce anomaly（Ce/Ce*=0.891.01）.These characteristics of Tieshan BIF are similar with characteristics of Gongchangling,Wutaishan and many other Archean BIF in the world.As for trace elements,contents of Ti,V,Co,Ni,Mn,Sr and Ba are low.In trace elements distribution diagram normalized by primary mantle,U,Ta,La,Ce and P have positive anomalies,whereas things are just the opposite for K,Nb,Sr,Hf and Zr.The ratios of Sr/Ba,Ti/V and some other elements are also considered in this paper.A comprehensive study of Tieshan BIF shows that its ferruginous material was associated with volcanic hydrothermal solution and was formed in a marine chemical sedimentary environment.It is thus held that the Tieshan iron deposit underwent the ferrosilicon sedimentary deposition stage followed by further enrichment during the late regional metamorphic process.In the late stage,the metamorphic fluids from the original homogeneous metamorphic ore-forming solution resulted in immiscibility and hence the enrichment of ore-forming elements.
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