条带状铁建造(BIF—Banded Iron Formation)上部发育的赤铁矿床(w(TFe)＞62％)是全球最重要的铁矿资源,但对其成矿条件的认识仍然存在争议.文章以几内亚西芒杜赤铁矿矿床(Ⅰ、Ⅱ区块)为例,根据全球古板块(含BIF)漂移轨迹,并按成矿系统"五要素"(源、运、储、变、保)对全球风化淋滤型赤铁矿矿床的形成条件进行讨论.文章认为丰富的矿源层是形成赤铁矿床的基础;条带状铁建造出露地表,板块(含BIF)漂移穿过赤道和南、北回归线是必备条件;上亿年的热带环境和热带雨林生物及微生物的作用是脱硅的关键;富氧化铁矿石的后期改造提高矿石质量;赤铁矿矿体大部分得到保存能形成超大型矿床.
Discussion on ore forming conditions of supergene high grade hematite ores from Simandou deposit(Ⅰ and Ⅱ region)in Guinea
Hematite deposits(w(TFe)＞62％)developed in the upper part of the banded iron formation(BIF)represent the most important iron ore resources in the world,but the ore-formation conditions remain debated.Taken the Si-mandou hematite deposit in Guinea as an example,and based on the drift trajectory of global ancient plates(con-taining BIF)and the"five elements"of mineralization system(including source,transport,storage,transforma-tion,and preservation),this paper discussed the ore-forming conditions of the BIF-hosted high-grade hematite de-posits in the world.We propose that abundant BIF layers are the basis for the formation of large-scale high-grade hematite deposits,the exposure of BIF layers to the surface and BIF-bearing plates drifting through the equator and Tropic of Cancer is a necessary condition,billions of years of tropical environment as well as tropical rainfor-est organisms and microorganisms is the key for desilicification,later alteration of hematite is favorable for in-creasing ore grade,and the preservation condition is also important for the formation of large-scale high-grade he-matite deposits.
banded iron formationsupergene processhigh-grade hematite oreore-forming conditionSimandou
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