| 华北克拉通辽东半岛新元古代早期基性岩浆活动:辉绿岩墙年代学和岩石地球化学证据 |
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| 引用本文： | 韩吉龙,王清海.华北克拉通辽东半岛新元古代早期基性岩浆活动:辉绿岩墙年代学和岩石地球化学证据[J].世界地质,2015,34(4):886-902. |
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| 作者姓名： | 韩吉龙 王清海 |
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| 作者单位： | 1. 吉林大学 地球科学学院，长春 130061; 2. 吉林大学 东北亚国际地学研究与教学中心，长春 130026 |
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| 摘 要： | 华北克拉通辽东半岛地区广泛发育侵位于青白口系不同层位中的辉绿岩(脉)岩墙,对其锆石CL图像、U--Pb定年和岩石地球化学特征研究得出以下结论。锆石类型有三组:前两组锆石具有早期岩浆作用的锆石属性或结晶基底的变质锆石属性,反映该区辉绿岩岩浆上升过程受到了陆壳的混染;第三组锆石多呈自形--半自形短柱状,发育岩浆振荡生长环带结构或条带结构,具原生岩浆成因锆石属性,锆石SHRIMP U--Pb定年显示其加权平均年龄为832.3±8.1 Ma(n=14,MSWD=1.3),可以代表辉绿岩的结晶年龄。岩石地球化学组成,其具有低Si O_2、Al_2O_3,高TFe_2O_3、MgO、Ti O_2的特征,这与拉斑玄武岩特征相似;其稀土元素总量相对较低(ΣREE=71.88×10~-6~129.64×10~-6),且具弱的正Eu异常和铌亏损;略富集轻稀土元素(LREE)、富集大离子亲石元素(LILE:Rb、Pb、Ba)和高场强元素(HFSE:Th、U、Zr、Ti、Hf),而亏损高场强元素(HFSE:Nb、Sm、Gd、P)等;以上特征指示岩浆源区为富集型地幔,且上侵位就位过程中受陆壳不同程度的同化混染。本文对辉绿岩的研究显示华北克拉通辽东半岛地区在新元古代早期存在基性岩浆活动,结合前人对华北克拉通中元古代晚期—新元古代早期构造--岩浆事件的研究成果,进一步证明了华北克拉通东北部在新元古代早期经历了挤压汇聚后的伸展裂解演化过程,这与Rodinia超大陆聚合和裂解事件一致。
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| 关 键 词： | 华北克拉通 辽东半岛 新元古代早期 辉绿岩 SHＲIMP U- - Pb 年代学 地球化学 Ｒodinia 超大陆 |
Early Neoproterozoic basic magmatism in Liaodong Peninsula，northeastern North China Craton: evidence from zircon SHＲIMP U- - Pb age and whole- rock geochemistry of diabase dike |
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| HAN Ji-Long,WANG Qing-Hai.Early Neoproterozoic basic magmatism in Liaodong Peninsula，northeastern North China Craton: evidence from zircon SHＲIMP U- - Pb age and whole- rock geochemistry of diabase dike[J].World Geology,2015,34(4):886-902. |
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| Authors: | HAN Ji-Long WANG Qing-Hai |
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| Institution: | 1. College of Earth Sciences，Jilin University，Changchun 130061，China; 2. International Center for Geoscience Ｒesearch and Education in Northeast Asia，Jilin University，Changchun 130026，China |
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| Abstract: | The diabase dike develops extensively in Liaodong Peninsula，North China Craton ( NCC)， which emplaces in different layers of Qingbaikou System． The following conclusions are drawn from the zircon CL image，SHＲIMP U- -Pb dating and the geochemical characteristics． The zircon types can be divided into three groups，two groups with the attributes of early magmatic zircon or metamorphic zircon in crystalline basement， impl- ying that they experienced contamination by the crust during the emplacement process of diabase magma，and the third group with euhedral- subhedral short column in sharpe，displaying oscillatory growth zoning rims or striped ab- sorption，indicating that the zircons are of igneous origin． The weighted mean age from the third type of zircon by SHＲIMP U - - Pb zircon dating is 832. 3 ±8. 1 Ma (n =14，MSWD =1. 3)，which can represent the crystallization age of diabase． Geochemically，the diabase has relatively low contents of SiO 2 and Al 2 O 3 ，high contents of TFe 2 O 3 ，MgO and TiO 2 ，which is similar to those of tholeiite． And they have low total ＲEE content (ΣＲEE = 71. 88 ×10 －6 ～129. 64 × 10 －6 )，with slight Eu anomaly and Nb * loss，and are relatively enriched in light rare earths (LＲEE)，large in lithophile elements (LILE: Ｒb，Pb，Ba) and high field strength elements (HFSE: Th，U，Zr，Ti，Hf)，but relatively depleted in high field strength elements (HFSE: Nb，Sm，Gd，P)． Above characteristics indicate that the magma source is close to that of enriched mantle，and the magma experi- enced assimilation and contamination by the continental crustal materials of different degrees during the emplace- ment process． Combined with previous data on Late Mesoproterozoic- -Early Neoproterozoic tectono- magmatism in the north margin of NCC，the diabase research in this paper confirms the existence of the Early Neoproterozoic bas- ic magmatism in Liaodong Peninsula，and further evidences the northeastern NCC experienced in extensional break- ing processes in Early Neoproterozoic after the compression convergencing，which coincides with the assembly and breaking event of Ｒodinia supercontinent． |
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| Keywords: | North China Craton Liaodong Peninsula Early Neoproterozoic diabase SHＲIMP U- - Pb dat- ing geochemistry Ｒodinia supercontinent |
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