西非矿产资源的地质背景及重要成矿分区
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摘要
西西非地区蕴藏着丰富的矿产资源,尤其以产出众多大型超大型的铝土矿、铁矿、金矿、金刚石矿等著称,在全球占有重要地位。矿床集中分布在三个构造域内,形成于不同的成矿期:(1)太古宙马恩(Man)地盾和雷圭巴特(Reguibat)地盾、古元古界莱奥(Leo)地盾及凯涅巴(Kéniéba)和卡伊(Kayes)构造窗,主要成矿事件包括在2.5-2.3 Ga形成了多个巨型铁矿床;几乎所有金矿、斑岩型铜矿、铅锌矿和沉积型锰矿都形成于2.2-2.1 Ga;原生金刚石矿床形成于两个时间段,分别是2.2-2.0 Ga左右和中生代。(2)泛非期和海西期活动带成矿域,主要成矿事件包括前寒武纪2.1 Ga左右以及680 Ma左右发生的铁氧化物铜金矿床(IOCG)成矿事件,以及新元古代沉积型铁矿和磷矿。(3)克拉通内盆地和海岸盆地带,包括新生代在中生代辉绿岩之上发生的铝土矿化作用,新近纪/第四纪形成的砂矿床、鲕状铁矿床和沉积型磷矿。西非地区的矿产分布规律与成矿时代、赋矿岩石、区域构造密切相关,不同矿种区域集中分布特征明显。根据已发现的铁矿、铝土矿、金矿、金刚石矿等主要经济矿产的分布,结合区域地质背景等因素,在西非克拉通南部划分了3个重要成矿区:(1)马恩太古宙地盾铁、金刚石巨型成矿区;(2)莱奥古中元古界地盾(包括凯涅巴构造窗)金矿等巨型成矿区;(3)博韦(Bove)新元古-古生代盆地铝土矿巨型成矿区。这些巨型成矿区也是西非地区最重要的矿产地和成矿远景区。
West Africa is rich in mineral resources, especially in the production of large and super-large bauxite, iron ore, gold, diamond and so on, which occupies an important position in the world. The deposits are concentrated in three tectonic domains and formed in different metallogenic stages:(1) Archean Man shield and Reguibat shield, Paleoproterozoic Leo shield and Kéniéba and Kayes structural window, The main metallogenic events include the formation of several huge iron deposits in 2.5-2.3 Ga; almost all gold deposits, porphyry copper deposits, lead-zinc deposits and sedimentary manganese deposits were formed in 2.2-2.1 Ga, while primary diamond deposits were formed in 2.2-2.0 Ga and Mesozoic respectively.(2) In the Pan-African and Hercynian active metallogenic domains, the main metallogenic events include the occurrence of iron oxide copper-gold deposits(IOCG) in the Precambrian around 2.1 Ga and 680 Ma respectively,as well as the Neoproterozoic sedimentary iron ore and phosphorus deposits.(3) The intracratonic basins and coastal basin belts include bauxite mineralization over Mesozoic diabase in Cenozoic, ancient placer type deposits, oolitic iron deposits and sedimentary phosphate deposits formed in Tertiary/Quaternary. The distribution of mineral resources in West Africa is closely related to metallogenic epoch, ore-hosting rocks and regional structure, and the regional concentration distribution characteristics of different mineral species are obvious. According to the distribution of major economic minerals such as iron ore, bauxite, gold and diamond deposits, and combined with regional geological background, three important metallogenic areas are divided in the southern part of West African craton:(1) Archean shield iron and diamond mega-metallogenic areas in Man shield;(2) Mesoproterozoic Leo shield(including Kaneba structural window) gold deposits;(3)Bowe Neoproterozoic-Paleozoic basin bauxite giant metallogenic area. These mega-metallogenic areas are also the most important mineral resources and metallogenic prospects in West Africa.
West Africa is rich in mineral resources, especially in the production of large and super-large bauxite, iron ore, gold, diamond and so on, which occupies an important position in the world. The deposits are concentrated in three tectonic domains and formed in different metallogenic stages:(1) Archean Man shield and Reguibat shield, Paleoproterozoic Leo shield and Kéniéba and Kayes structural window, The main metallogenic events include the formation of several huge iron deposits in 2.5-2.3 Ga; almost all gold deposits, porphyry copper deposits, lead-zinc deposits and sedimentary manganese deposits were formed in 2.2-2.1 Ga, while primary diamond deposits were formed in 2.2-2.0 Ga and Mesozoic respectively.(2) In the Pan-African and Hercynian active metallogenic domains, the main metallogenic events include the occurrence of iron oxide copper-gold deposits(IOCG) in the Precambrian around 2.1 Ga and 680 Ma respectively,as well as the Neoproterozoic sedimentary iron ore and phosphorus deposits.(3) The intracratonic basins and coastal basin belts include bauxite mineralization over Mesozoic diabase in Cenozoic, ancient placer type deposits, oolitic iron deposits and sedimentary phosphate deposits formed in Tertiary/Quaternary. The distribution of mineral resources in West Africa is closely related to metallogenic epoch, ore-hosting rocks and regional structure, and the regional concentration distribution characteristics of different mineral species are obvious. According to the distribution of major economic minerals such as iron ore, bauxite, gold and diamond deposits, and combined with regional geological background, three important metallogenic areas are divided in the southern part of West African craton:(1) Archean shield iron and diamond mega-metallogenic areas in Man shield;(2) Mesoproterozoic Leo shield(including Kaneba structural window) gold deposits;(3)Bowe Neoproterozoic-Paleozoic basin bauxite giant metallogenic area. These mega-metallogenic areas are also the most important mineral resources and metallogenic prospects in West Africa.
引文
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[2]Petters S W.Regional Geology of Africa[M].SpringerVerlag,Berlin,Heidelberg,1991.
[3]段焕春,林晓辉,秦正永.西非地质和矿产的基本特征[C].//见:非洲地质经济:纪念天津华北地质勘查局走出去10周年论文集[M].北京:地质出版社,2009:136-145.
[4]Wright J B,Hastings D A,Jones W B,Williams H R.Geology and mineral resources of West Africa[J].London:George Allen&Unwin Ltd.,1985.
[5]Markwitz V,Hein K A A,Miller J.Compilation of West Africa mineral deposits:Spatial distribution and mineral endowment[J].Precambrian Research,2015,274:61-81.
[6]梅燕雄,裴荣富,裴荣富,杨德凤,戴自希,李进文,徐丛荣,瞿泓滢.全球成矿域和成矿区带[J].矿床地质,2009,28(4):383-389.
[7]毛景文,张作衡,王义天,李晓峰,谢桂青,杨富全.国外主要矿床类型、特点及找矿勘查[J].北京:地质出版社,2012.
[8]Commission for the Geological Map of the World.International mineral deposits map of Africa(1/5 000 000,Sheet 1)[M].CGMW/Council for Geoscience,2002.
[9]Brinckmann J,Bering D,Toloczyki M.Geological and Geographical Map of Western Africa(1:2 000 000)(Sheet1:Geotectonic and Geological Situation of Guinea,Sierra Leone,Liberia,West Coast of Ivo 1..re,Southwest of Mali)[M].Assessment of the inventory of mineral resources of Guinea,1997.in France.
[10]Brinckmann J,Bering D,Toloczyki M.Geological and Geographical Map of Western Africa(1:2 000 000)(Sheet2:Geotectonic and Geological Situation of Guinea,Sierra Leone,Liberia,West Coast of Ivo 1..re,Southwest of Mali)[M].Assessment of the inventory of mineral resources of Guinea,1997.in France.
[11]Milesi J P.West African gold deposits in their Lower Proterozoic lithostructural setting(1/2000,000)[M].Chronique de la Recherche Miniere(497),1989:3-98.
[12]Matt Fernley,Brock Salier,et al.African Iron Ore Equities:Lots going on in Africa but focus on quality[R].Securities(GMP)Metals&Minerals,2013.02.
[13]Skinner E M W,Apter D B,Morelli C,Smithson NK.Kimberlites of the Man craton,West Africa[J].Lithos,2004,76:233-259.
[14]Hirdes W,Toloczyki M,Davis D W,Agyei Duodu J.Loh G K,Boamah K O,Baba M.Geological map of Ghana1:1 000 000[M].Geological Survey Dpartment(GSD),Accra,Republic of Ghana,2009.
[15]Bossiére G,Bonkoungou I,Peucat J,Pupin J.Origin and age of Paleoproterozoic conglomerates and sandstones of the Tarkwaian Group in Burkina Faso,West Africa[J].Precambrian Research,1996,80(3-4):153-172.
[16]Béziat D,Dubois M,Debat P,Nikiéma S,Stefano S,Tollon F.Gold metallogeny in the Birimian craton of Burkina Faso(West Africa)[J].Journal of African Earth Sciences,2008,50(2-4):215-233.
[17]Hein K A A,Morel V,KagonéO,Kiemde F,Mayes K.Birimian lithological succession and structural evolution in the Goren segment of the Boromo-Goren Greenstone Belt,Burkina Faso[J].Journal of African Earth Sciences,2004,39(1-2):1-23.
[18]Institut géographique national(France).CARTE DEL'AFRIQUE DE L'OUEST AU 1/200000(FEUILLE ND-29-V/ND-29-VI,BAMAKO EST/DIOILA)[M].Paris:Institut Géographique National,1929.
[19]徐红伟,张先忠.几内亚共和国博凯地区红土型铝土矿地质特征和成矿机理初探[J].长春工程学院学报(自然科学版),2009,10(1):87-91.