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引用本文:刘飞,杨经绥,连东洋,余晓艳,Kewame Rollyken Gwandu. 博茨瓦纳和中国含金刚石金伯利岩的地质特征及对寻找类似岩体的启示[J]. 中国地质, 2019, 46(1): 43-76.
LIU Fei,YANG Jingsui,LIAN Dongyang,YU Xiaoyan,Kewame Rollyken Gwandu. Metallogenic features of diamondiferous kimberlites in Botswana and China:Enlightenment for exploration of the same type deposits[J]. Geology in China, 2019, 46(1): 43-76(in Chinese with English abstract).
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博茨瓦纳和中国含金刚石金伯利岩的地质特征及对寻找类似岩体的启示
刘飞1, 杨经绥1, 连东洋2, 余晓艳3, Kewame Rollyken Gwandu4
1.地幔研究中心, 自然资源部深地动力学实验室, 中国地质科学院地质研究所, 北京 100037;2.南京大学地球科学与工程学院, 江苏 南京 210023;3.中国地质大学珠宝学院, 北京 100083;4.Botswana Geoscience Institute, Lobatse 70883, Botswana
摘要:
金刚石及其寄主岩石是人类认识地球深部物质组成和性质、壳幔和核幔物质循环重要研究对象。本文总结了中国不同金刚石类型的分布,着重对比了博茨瓦纳和中国含金刚石金伯利岩的地质特征,取得如下认识:(1)博茨瓦纳含矿原生岩石仅为金伯利岩,而中国含矿岩石成分复杂,金伯利岩主要出露在华北克拉通,展布于郯庐、华北中央和华北北缘金伯利岩带,具有工业价值的蒙阴和瓦房店矿床分布于郯庐金伯利岩带中;钾镁煌斑岩主要出露在华南克拉通,重点分布在江南和华南北缘钾镁煌斑岩带中;(2)钙钛矿原位U-Pb年龄和Sr、Nd同位素显示,86~97 Ma奥拉帕金伯利岩群和456~470 Ma蒙阴和瓦房店金伯利岩均具有低87Sr/86Sr(0.703~0.705)和中等εNdt)(-0.09~+5)特征,指示金伯利岩浆源自弱亏损地幔或初始地幔源区;(3)博茨瓦纳金伯利岩体绝大多数以岩筒产出,而中国以脉状为主岩筒次之;博茨瓦纳岩筒绝大部分为火山口相,中国均为根部相,岩筒地表面积普遍小于前者;(4)奥拉帕A/K1和朱瓦能金伯利岩体是世界上为数不多的主要产出榴辉岩捕虏体和E型金刚石的岩筒之一,而同位于奥拉帕岩群的莱特拉卡内、丹姆沙和卡罗韦岩体与我国郯庐带的金伯利岩体类似,均主要产出地幔橄榄岩捕虏体以及P型和E型金刚石;(5)寻找含矿金伯利岩重点注意以下几点:克拉通内部和周缘深大断裂带是重要的控岩构造;镁铝榴石、镁钛铁矿、铬透辉石、铬尖晶石和铬金红石等是寻找含金刚石金伯利岩重要的指示矿物;航磁等地球物理测量需与土壤取样找矿方法相结合才能取得更好效果;(6)郯庐金伯利岩带、江南钾镁煌斑岩带和塔里木地块是中国重要含矿岩石的找矿靶区,冲积型金刚石成矿潜力巨大。
关键词:  金伯利岩  金刚石  找矿标志  博茨瓦纳  中国
DOI:10.12029/gc20190104
分类号:
基金项目:国家自然科学基金项目(41672063,41773029,41373029,41720104009),中国地质调查局地质调查项目(DD20160023-01,DD20160022-01)和科技部项目(2014DFR2127C)联合资助。
Metallogenic features of diamondiferous kimberlites in Botswana and China:Enlightenment for exploration of the same type deposits
LIU Fei1, YANG Jingsui1, LIAN Dongyang2, YU Xiaoyan3, Kewame Rollyken Gwandu4
1.CARMR, Key Laboratory of Deep-Earth Dynamics of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2.School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, Jiangsu, China;3.School of Gemology, China University of Geosciences, Beijing 100083, China;4.Botswana Geoscience Institute, Lobatse 70883, Botswana
Abstract:
Important implications for the interior workings, constituent, circulation between crust and mantle, convection between core and mantle of the Earth can be drawn by studying diamonds and their hosted rocks. Based on the geological comparison of metallogenic kimberlites from super-giant deposits in Botswana and Mengyin and Wafangdian deposits in China, the authors put forward some exploration suggestions and prospecting clues as follows:(1) Kimberlite is an unique diamondiferous rock in Botswana, whereas lamproite is a main hosted -rock in South China craton including two important lamproite zones along the Jiangnan orogenic belt and northern margin of South China craton. Kimberlite is dominantly distributed in the North China craton, which is composed of three kimberlitic zones along Tanlu fault, Trans-North China orogen and northern margin of North China. Two industrial value diamondiferous kimberlite deposits are distributed in the Tanlu zone. (2) In-situ U-Pb age and Sr, Nd isotopic data of perovskites show that 86-97 Ma Orapa kimberlites and 456-470 Ma Mengyin and Wafangdian kimberlites have low 87Sr/86Sr ratios of 0.703-0.705, medium εNd(t) values ranging from -0.09 to 5, indicating that primary kimberlitic magmas were likely derived from primitive mantle or convective lower mantle. (3) Primary kimberlites in Botswana dominantly occur as pipes, while in China they mainly occur as irregular fissures, expressed as dykes and lesser extent sills. Crater facies are pervasively observed in Orapa and Jwaneng kimberlite pipes in comparison with hypabyssal (or root zone) facies in Mengyin and Wafangdian pipe clusters. (4) Orapa A/K1 and Jwaneng mines are a few diamondiferous kimberlitic pipes yielding predominantly eclogitic xenoliths and E type diamond. In contrast, Letlhakane, Damtshaa and Karowe mines also occur in Orapa cluster, Mengyin and Wafangdian mines from the Tanlu kimberlite belt have mainly peridotite xenoliths as well as P type and E type diamonds. (5) Some exploration suggestions and prospecting clues of diamondiferous kimberlites are presented as follows:(A) Deep faults cutting through on-craton and off-craton subcontinental lithospheric mantle play a role in the emplacement of kimberlites; (B) Soil sampling for kimberlite indicator minerals such as picroilmenite and garnet, Cr-rich rutile, Cr-spinel and Cr-diopside is a primary exploration tool; (C) Geophysical surveys such as aeromagnetic mothed should be combined with soil sampling for better prospecting results. (6) Work in diamondiferous prospecting target areas in the Tanlu kimberlite zone, Jiangnan lamproite zone and Tarim block should be further strengthened. Illuvial type diamond deposits in China have great potential for mineralization.
Key words:  kimberlite  diamond  prospecting indicator  Botswana  China