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引用本文:蔡逸涛,张洁,董钟斗,曹正琦,肖书阅,李帅,李成凯,陈乐柱,范飞鹏. 皖北栏杆地区新元古代岩浆活动:含金刚石母岩U-Pb年代学及地球化学制约[J]. 中国地质, 2018, 45(2): 351-366.
CAI Yitao,ZHANG Jie,DONG Zhongdou,CAO Zhengqi,XIAO Shuyue,LI Shuai,LI Chenkai,CHEN Lezhu,FAN Feipeng. Neoproterozoic basic magmatism in the north of Anhui Province: Evidence from whole-rock geochemistry and U-Pb geochronology of Diabase in Langan area[J]. Geology in China, 2018, 45(2): 351-366(in Chinese with English abstract).
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皖北栏杆地区新元古代岩浆活动:含金刚石母岩U-Pb年代学及地球化学制约
蔡逸涛1,2, 张洁1,3, 董钟斗4, 曹正琦3, 肖书阅5, 李帅5, 李成凯6, 陈乐柱1, 范飞鹏1
1.南京地质调查中心, 江苏 南京 210016;2.内生金属矿床成矿机制研究国家重点实验室, 南京大学地球科学与工程学院, 江苏 南京 210093;3.中国地质大学(武汉)地球科学学院, 湖北 武汉 430074;4.安徽省地勘局第二水文地质工程勘察院, 安徽 芜湖 241000;5.湖南省地质矿产勘查开发局四一三队, 湖南 常德 415000;6.中国地质大学(北京)地球科学与资源学院, 北京 100083
摘要:
中国东部皖北地区分布着大量镁铁质岩,岩石类型为辉绿岩、辉绿辉长岩、辉绿玢岩等。本文对皖北栏杆地区侵位于元古宙地层中的辉绿岩进行系统的U-Pb年代学、岩石地球化学研究。结果显示,该区绝大多数辉绿岩的侵位结晶年龄为870~890 Ma,形成于新元古代早期。辉绿岩化学成分以高SiO2、CaO和(K2O2O)为特征,属于板内碱性玄武岩系列岩石。总体上略富集轻稀土元素(LREE)、富集大离子亲石元素(LILE)Rb、Ba、La,略亏损高场强元素(HFSE)Th、Nb、Ta、Zr、Hf等,相对富集Cr和Ni。本次研究暗示皖北栏杆地区存在新元古代早期的构造-岩浆活动事件,并为金刚石带出地表创造了条件。结合新元古代全球Rodinia超大陆裂解事件及其岩浆活动与地幔柱的密切关系,皖北地区新元古代辉绿岩墙群应该是一次地幔柱作用在华北陆块边缘的记录。
关键词:  金刚石  U-Pb  年代学  岩石地球化学  皖北栏杆
DOI:10.12029/gc20180210
分类号:P597+.3;P595;P588.12+4
基金项目:国家青年科学基金项目(41402075)和中国地质调查局地调项目(12120114054301)联合资助。
Neoproterozoic basic magmatism in the north of Anhui Province: Evidence from whole-rock geochemistry and U-Pb geochronology of Diabase in Langan area
CAI Yitao1,2, ZHANG Jie1,3, DONG Zhongdou4, CAO Zhengqi3, XIAO Shuyue5, LI Shuai5, LI Chenkai6, CHEN Lezhu1, FAN Feipeng1
1.The Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, Jiangsu, China;2.State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, Jiangsu, China;3.School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China;4.The Second Institute of Hydrology and Engineering Geological Prospecting of Anhui Geological Prospecting Bureau, Wuhu 241000, Anhui, China;5.Team 413 of Geology & Mineral Resources Development Bureau, Changde 415000, Hunan, China;6.School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
Abstract:
The mafic rock is exposed in North Anhui province of the East China. It consists of diabase, gabro-diabase and dabaseporphyrite. This paper presents a synthetic U-Pb isotopic study of zircons and a whole-rock geochemical study on diabase that were emplaced into the Proterozoic formations in the Langan area of the North Anhui province. The SHRIMP U-Pb zircon dating results indicate that the diabase were emplaced at ca.870-890 Ma. Geochemically, the diabase swarms are characterized by enriched in SiO2、CaO and (K2O2O).It is therefore deduced that the diabases might belong to intraplate tholeiite occurring within the North China Plate. There are also show relative enrichment in LREE and LILE(Rb, Ba and La),a comparative enrichment in Cr and Ni, but a slight depletement in HFSE(Th, Nb, Ta, Zr and Hf).They are plotted in the within-plate tholeiite series on the tectonic discrimination diagrams. Taken together, these geochemical and isotopic data suggest that the primary magmas to form the diabase dykes in the Langan area could have been derived from a transitional mantle in the Mesoproterozoic, and were most probably emplaced under a continental margin extensional setting at ca.870-890 Ma. The results of this study demonstrate that the Neoproterozoic magmatism occurred at the Langan area of the North Anhui province, and created conditions for diamond mineralization. Taken along with the Neoproterozoic breakup of the Rodinia Supercontinent and the close relationship between the coeval magmatism and the hypothesis of a superplmue, it is reasonable to contribute the emplacement of the Neoproterozoic diabases in the Langan area to the geochemical fingerprints the contemporaneous mantle plume activity preserved in the continental margin of the North China Block.
Key words:  diamond minerliaztion  U-Pb zircon dating  geochemistry  Langan