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华北克拉通中部早白垩世岩石圈地幔性质:来自狐偃山科头钾质正长岩年代学、同位素的限制
投稿时间:2019-09-27  修订日期:2019-12-30  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020130
摘要点击次数: 37
全文下载次数: 41
作者单位E-mail
张乔 中国地质调查局西安地质调查中心 hotrock2012zq@163.com 
周俊林 中国地质调查局西安地质调查中心 zjlcug@163.com 
李玉宏 中国地质调查局西安地质调查中心  
陈高潮 中国地质调查局西安地质调查中心  
张慧婷 西安科技大学  
基金项目:国家自然科学基金项目(编号 41572131)和中国地质调查局“关中地区氦气资源调查项目(编号 20190103)
中文摘要:华北克拉通东部中生代岩石圈减薄已经取得了大量进展,相比之下对克拉通中部岩石圈演化认识不足。本文对华北克拉通中部狐偃山杂岩体中科头正长岩进行了锆石U-Pb年代学、主量和微量元素、Sr-Nd-Hf同位素地球化学研究。LA-ICP-MS锆石U-Pb定年结果显示,科头正长岩侵位于早白垩世晚期(~111Ma)。岩石样品均为钾质—超钾质,属于碱性系列岩石。这些岩石相对富集轻稀土,亏损重稀土和中稀土,具有明显的正Eu异常(Eu/Eu*=1.22~1.96)、富集大离子亲石元素LILE(Rb、Sr、Ba),亏损高场强元素HFSE(Nb、Ta、Ti)。所有岩石样品具有相对高的初始87Sr/86Sr 比值(0.7058~0.7062)和低的εNd (t)(-10.4~-11.1),εHf (t)介于-12.2~-5.2之间。详细的元素和同位素地球化学研究表明科头正长岩的原始岩浆可能来源于富集岩石圈地幔中富金云母的尖晶石二辉橄榄岩源区的部分熔融,岩浆演化过程中经历了地壳混染与结晶分异(AFC)过程。结合华北克拉通中部岩浆资料,将华北克拉通中部早白垩世岩浆作用分为早晚两期:早期(123~135Ma)为岩浆作用高峰期,晚期(~114Ma)为最后一期弱的岩浆期;华北克拉通中部陆下岩石圈地幔是富集的、不均一的,其至少在早白垩世(138~111Ma)一直处于减薄状态。
中文关键词:华北克拉通中部  正长岩  早白垩世晚期  钾质  富集岩石圈地幔  岩石圈减薄
 
Nature of Early-Cretaceous lithosphere mantle in central North China craton: constraints from dating, and isotopic data of Ketou potassic syenite in Huyanshan
Author NameAffiliationE-mail
Zhang Qiao Xi’an Center of Geological Survey, China Geological Survey hotrock2012zq@163.com 
Zhou Junlin Xi’an Center of Geological Survey, China Geological Survey zjlcug@163.com 
Li Yuhong Xi’an Center of Geological Survey, China Geological Survey  
Chen Gaochao Xi’an Center of Geological Survey, China Geological Survey  
Zhang Huiting Xi’an University of Science and Technology  
Abstract:A lot of progress on Mesozoic lithospheric thinning has been made in eastern North China Craton, while the research of that in central North China remain weak. This study presents detailed LA-ICP-MS zircon U-Pb dating, major and trace element geochemical and Sr-Nd-Hf isotopic data for Ketou syenite within Huyanshan alkaline complex in central North China Craton. LA-ICP-MS zircon U-Pb dating shows that Ketou syenite was emplaced at the late stage (111 Ma) of Early-Cretaceous. These samples are all potassic-ultrapotassic and alkaline rocks. They are distinct positive Eu anomalies. They have high initial 87Sr/86Sr of 0.7058~0.7062, lower εNd (t) of -11.1 to -10.4 and zircon εHf(t) values of -12.2 to -5.2. Detailed research suggest that primitive magmas of Ketou syenite were derived from partial melting of enriched lithosphere mantle with phlogopite-bearing lithosphere mantle at spinel lherzolite zone. And primitive magmas have went through the process of assimilation and fractional crystallization (AFC). Combined with published data of magmatism in central North China, we infer that the late-Mesozoic magmatism in central North China can be subdivided into two stages: early one at 123~135 Ma for the peak magmatism, late one at 114 Ma for the last weak magmatism. Together with the source region for the late-Mesozoic magmatic rocks in central North China, it is indicated that the lithosphere mantle in central North China was enriched and heterogeneous, which was thinning at least from 138 to 111 Ma.
keywords:central North China craton  syenite  Late Early-Cretaceous  potassic  enriched lithosphere mantle  lithosphere mantle thinning
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