摘要
前人对金沙江-红河构造带上的煌斑岩研究工作主要集中在南段哀牢山地区.对构造带中段鲁甸地区新发现的煌斑岩脉进行了锆石U-Pb年代学和全岩地球化学研究.结果表明,煌斑岩形成时代为始新世末期,与滇西新生代富碱斑岩高峰期一致.鲁甸煌斑岩具有高钾、富碱、高Mg~#,富集大离子亲石元素(LILE)和轻稀土元素(LREE),亏损高场强元素(HFSE,尤其是Ta-Nb-Ti)的特征.其岩浆源区为受俯冲流体和熔体交代的岩石圈地幔,源区组分为含金云母的尖晶石相方辉橄榄岩.结合同期的镁铁质火山岩和富碱斑岩研究成果,滇西区域的岩石圈地幔富集过程可能为元古宙时期与罗迪尼亚超大陆聚合相关的俯冲作用.始新世时期,在印度和亚洲大陆碰撞过程中,金沙江-红河构造带的富集岩石圈地幔发生拆沉或对流减薄,软流圈物质上涌,引发富集的岩石圈地幔部分熔融,形成本期煌斑岩岩浆作用.
Researches on the lamprophyres from the Jinshajiang-Red River tectonic belt are mainly concentrated in the southern Ailaoshan area.The zircon U-Pb geochronology and the whole rock geochemistry of the newly discovered Ludian lamprophyres located in the middle segment of the belt are applied in this paper.Zircon U-Pb dating proves Eocene emplacement age of Ludian lamprophyres,which is consistent with the peak age of the Cenozoic magmatism in the Jingshajiang-Red River alkali-rich intrusion belt.Geochemical data indicate that Ludian lamprophyres have the characteristics of high K_2O,high（K_2O ＋ Na_2O）and Mg~#,low TiO_2,being enriched in LILE and LREE,depleted in HFSE（especially Ta-Nb-Ti）.The source of the Ludian lamprophyres should be the lithosphere mantle which had been enriched by subduction-related fluids and melts,and the source should be phlogopite bearing spinel harzburgite.Combined with the study of coeval mafic lava and felsic intrusion,we put forward that the mantle in western Yunnan might have been enriched by the Protozoic subduction related to the assembly of the Rodinia supercontinent.In the Eocene,following the collision between Indian and Asia,the continental lithosphere in the Jingshajiang-Red River tectonic belt underwent convective thinning or delamination,which induced rising of the asthenosphere,and then partialmelting of the enriched lithosphere mantle which generated the lamprophyre melt.
作者
贺娟
王启宇
闫国川
He Juan;Wang Qiyu;Yan Guochuana(Chengdu Center of China Geological Survey,Chengdu 610081,China;College of Earth Sciences and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2018年第8期2586-2599,共14页
Earth Science
基金
国家重点研究发展计划(No.2015CB452601)
中国地质调查局项目(No.DD20160016)
国家自然科学基金项目(No.41603038)
关键词
煌斑岩
金沙江-红河构造带
富集地幔
岩石成因
鲁甸
滇西
地质年代学
地球化学
lamprophyres
Jingshajiang-Red River tectonic belt
enriched mantle
petrogenesis
Ludian
western Yunnan
geochronology
geochemistry
