纳米比亚西北部朝斯组铁矿地质特征研究与初步经济评价
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摘要
纳米比亚西北部地区朝斯组中赋存大规模铁矿,该铁矿形成于新元古代约730 Ma时期,由于雪球地球的影响,全球在这一时期形成很多大的铁矿。本文通过对朝斯组铁矿岩芯的观察和对岩芯主量元素特征的分析可知朝斯组铁矿主要由Fe_2O_3和SiO_2组成,铁矿中SiO_2含量较高。微量元素特征表明铁矿中富集Co,相对亏损Rb。稀土元素特征表明铁矿中稀土总量均较低,具有相似的REE配分模式,轻稀土相对重稀土亏损,轻微的Eu正异常和明显的Ce负异常。地球化学分析表明铁矿的物质来源兼具陆源沉积物和海相沉积物的特征,Ce的轻微负异常反映了成矿时海水为低氧化环境,而Eu的轻微正异常说明海底低温热液参与了铁矿的成矿过程。朝斯组铁矿石资源量为20亿t,平均品位30%,潜在经济价值为700亿美元。纳米比亚对环境保护严格,采矿的征地成本很高,铁矿所在地区的基础设施非常差,从开采到铁矿运输的成本投入很高,这些都导致纳米比亚铁矿价格优势并不明显。本文认为,如果该地区未来不能发现其他价值更高的共伴生矿产,这些铁矿在目前技术经济条件下开采盈利的前景不明朗。
There is a large scale of iron ore deposit within the Chuos formation in northwest of Namibia.The iron ore was formed in about 730 Ma of Neoproterozoic.Due to the influence of snowball earth,many large iron ores formed in the world during this period.By analyzing the major element of iron ore of Chuos formation,it consists mainly of Fe_2O_3 and SiO_2,the SiO_2 content is high.Tracing element characteristics indicates that Co is enriched in iron ore and Rb is relatively deficient.The characteristics of rare earth elements indicate that the total amount of rare earth elements in iron ore is relatively low,and there is a similar REE distribution model.The light rare earth has loss relative to heavy rare earth,slight positive Eu anomaly and obvious negative Ce anomaly.The source of iron ore is characterized by both terrestrial sources sediments and marine sedimentary deposits.The slight negative anomaly of Ce reflects the low oxidizing environment of seawater during mineralization,but the slight anomaly of Eu indicates that the undersea cryohydrothermal is involved in the deposit of iron ore.The iron ore resources amount to 2 billion tons,average grade 30%,potential economic value is 70 billion US dollars.There is strictly environmental protection law in Namibia,the cost of land acquisition for mining is high,the infrastructure is poor,and the costs for mining and the ore transportation will be high.All these lead to Namibia iron ore price advantage may not be obvious.This paper argues that if the region cannot find other,more valuable,co-associated minerals in the future,the prospect of the mining of these iron ores under the current technical and economic conditions is not clear.
There is a large scale of iron ore deposit within the Chuos formation in northwest of Namibia.The iron ore was formed in about 730 Ma of Neoproterozoic.Due to the influence of snowball earth,many large iron ores formed in the world during this period.By analyzing the major element of iron ore of Chuos formation,it consists mainly of Fe_2O_3 and SiO_2,the SiO_2 content is high.Tracing element characteristics indicates that Co is enriched in iron ore and Rb is relatively deficient.The characteristics of rare earth elements indicate that the total amount of rare earth elements in iron ore is relatively low,and there is a similar REE distribution model.The light rare earth has loss relative to heavy rare earth,slight positive Eu anomaly and obvious negative Ce anomaly.The source of iron ore is characterized by both terrestrial sources sediments and marine sedimentary deposits.The slight negative anomaly of Ce reflects the low oxidizing environment of seawater during mineralization,but the slight anomaly of Eu indicates that the undersea cryohydrothermal is involved in the deposit of iron ore.The iron ore resources amount to 2 billion tons,average grade 30%,potential economic value is 70 billion US dollars.There is strictly environmental protection law in Namibia,the cost of land acquisition for mining is high,the infrastructure is poor,and the costs for mining and the ore transportation will be high.All these lead to Namibia iron ore price advantage may not be obvious.This paper argues that if the region cannot find other,more valuable,co-associated minerals in the future,the prospect of the mining of these iron ores under the current technical and economic conditions is not clear.
引文
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[2]李秀慧,刘典波.纳米比亚矿业投资环境分析[J].资源与产业,2012,14(2):122-126.LI Xiuhui,LIU Dianbo.Mining investment environment of Namibia[J].Resources&Industries,2012,14(2):122-126.
[3]李强,李明,赵明武,等.纳米比亚西北部新元古界沉积变质型铁矿地质特征及开发前景[J].矿产勘查,2012,3(6):845-849.LI Qiang,LI Ming,ZHAO Mingwu,et al.Geological characteristics and development prospects of sedimentary metamorphic iron deposit of upper Proterozoic age in northwestern Namibia[J].Mineral Exploration,2012,3(6):845-849.
[4]李啸.纳米比亚地质概况及矿产资源特征[J].中国矿业,2016,25(S1):52-54.LI Xiao. Geologicalfeaturesandmineralresources characteristics of Namibia[J].China Mining Magazine,2016,25(S1):52-54.
[5]张启锐,储雪蕾,张同钢,等.从“全球冰川”到“雪球假说”:关于新元古代冰川事件的最新研究[J].高校地质学报,2002,8(4):473-481.ZHANG Qirui,CHU Xuelei,ZHANG Tonggang,et al.From global glaciation to snowball earth:recent researches on the Neoproterozoic glaciation events[J].Geological Journal of China Universities,2002,8(4):473-481
[6] BEKKER A,SLACK J F,PLANAVSKY N,et al.Iron formation:the sedimentary product of a complex interplay among mantle,tectonic,oceanic,and biospheric processes[J].Economic Geology,2010,105:467-508.
[7] HOFFMAN P F,KAUFMAN A J,HALVERSON G P,et al.A Neoproterozoic snowball earth[J].Science,1998,281:1342-1346.
[8]曹晗,吴昌志,刘援军,等.纳米比亚达马拉造山带新元古界朝斯组条带状铁建造的特征及成因[J].地质学刊,2016,40(4):589-598.CAO Han,WU Changzhi,LIU Yuanjun,et al.Characteristics and genesis of banded iron formation in the Neoproterozoic Chuos formation in Damara belt of Namibia[J].Journal of Geology,2016,40(4):589-598.
[9]杨松生,阮娟,周喜军,等.纳米比亚西北部朝斯组铁矿成因及有利区段选择[J].地质学刊,2017,41(1):124-128.YANG Songsheng,RUAN Juan,ZHOU Xijun,et al.On iron deposit and potential area selection in Chuos formation in northwestern Namibia[J].Journal of Geology,2017,41(1):124-128.
[10] MILLER R McG,BECKER T.The geology of Namibia[M].Windhoek,Namibia:Geological Survey of Namibia,Ministry of Mines and Energy,2008:13-70.
[11]沈其韩,宋会侠,杨崇辉,等.山西五台山和冀东迁安地区条带状铁矿的岩石化学特征及其地质意义[J].岩石矿物学杂志,2011,30(2):161-171.SHEN Qihan,SONG Huixia,YANG Chonghui,et al.Petrochemical characteristics and geological significations of banded iron formations in the Wutai Mountain of Shanxi and Qian'an of eastern Hebei[J]. Acta Petrologica et Mineralogica,2011,30(2):161-171.
[12]秦洁璇.2017年中国铁矿石市场回顾及2018年走势分析[J].冶金经济与管理,2018(2):30-34.QIN Jiexuan.Review of China's iron ore market in 2017and analysis of 2018 trends[J].Metallurgical Economy and Management,2018(2):30-34.
[13]李秀慧,刘典波.我国矿业矿业在纳米比亚投资面临的风险和对策[J].中国矿业,2012,21(5):52-55.LI Xiuhui,LIU Dianbo.Risks and solutions for Chinese mining company investing in Namibia[J].China Mining Magazine,2012,21(5):52-55.