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北山造山带南部奥陶纪-志留纪变质地层LA-ICP-MS锆石U-Pb定年
投稿时间:2021-06-29  修订日期:2021-07-23  点此下载全文
引用本文:王浩,任留东,王彦斌,李天福,李淼.2021.北山造山带南部奥陶纪-志留纪变质地层LA-ICP-MS锆石U-Pb定年[J].地质论评,67(5):67060001,[DOI]:.
WANG Hao,REN Liudong,WANG Yanbin,LI Tianfu,LI Miao.2021.LA-ICP-MS U-Pb Dating of Zircons from the Metamorphic Ordovician-Silurian Sequence in Southern Beishan Orogenic Belt[J].Geological Review,67(5):67060001.
DOI:
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作者单位E-mail
王浩 中国地质科学院地质研究所北京100037 2407779658@qq.com 
任留东 中国地质科学院地质研究所北京100037 ldren@ cags.ac.cn 
王彦斌 中国地质科学院地质研究所北京100037  
李天福 中国地质科学院地质研究所北京100037  
李淼 中国地质科学院地质力学研究所北京100081  
基金项目:本文为中国地质调查局地质调查项目(编号:DD20190358、20190370和20190448)资助成果
中文摘要:北山造山带东南部梧桐井地区广泛出露一套奥陶纪-志留纪地层, 有关其形成时代和区域地层对比仍存在较大分歧,极大的限制了对区域地质演化的认识。为进一步确定其形成时代,本文对该地区奥陶-志留系c岩组中的角闪绿帘黑云斜长片麻岩、白云母石英片岩及侵入其中的长英质岩脉进行了LA-ICP-MS锆石U-Pb定年。获得206Pb/238U加权平均年龄分别为419.8±2.7 Ma、421.5±0.8 Ma和417.0±3.4 Ma,前两者年龄在误差范围内一致,侵入其中的脉体的年龄限定了该岩组年龄的下限;由此将前人划分的奥陶系-志留系c岩组确切的形成时代确定为约420 Ma,属晚志留世。结合原定为奥陶系-志留系b岩组获得2个锆石U-Pb单峰年龄分别为427 Ma和428 Ma, 属中志留世(Song Dongfang et al., 2016),由此,将原奥陶纪-志留纪地层确定为志留纪地层,结合前人研究认为可能形成于早古生代古亚洲洋向敦煌地块俯冲相关的弧前盆地。
中文关键词:北山造山带  奥陶系-志留系  角闪绿帘黑云斜长片麻岩  白云母石英片岩  锆石U-Pb定年
 
LA-ICP-MS U-Pb Dating of Zircons from the Metamorphic Ordovician-Silurian Sequence in Southern Beishan Orogenic Belt
NameInstitution
WANG HaoInstitute of Geology,Chinese Academy of Geological Sciences,Beijing,100037
REN LiudongInstitute of Geology,Chinese Academy of Geological Sciences,Beijing,100037
WANG YanbinInstitute of Geology,Chinese Academy of Geological Sciences,Beijing,100037
LI TianfuInstitute of Geology,Chinese Academy of Geological Sciences,Beijing,100037
LI MiaoInstitute of Geomechanics,Chinese Academy of Geological Sciences,Beijing,100081
Abstract:Objectives: In the southeastern Beishan orogenic belt,there occurs a complex metamorphic sequence at Wutongjing area,which were taken as Ordovician-Silurian strata. Controversies exist on its formation ages and regional stratigraphic correlation,which greatly limits the understanding of regional geological evolution of the region.Methods: To determine the age of the sequence,LA-ICP-MS zircon U-Pb dating was performed on hornblende epidote biotite plagioclase gneiss and muscovite quartz schist of Formation Complex c of the sequence and monzonitic granite vein that intruded the gneiss in this area.Results: Weighted mean 206Pb/238U zircon ages of 419.8 ± 2.7 Ma,421.5 ± 0.8 Ma and 417.0 ± 3.4 Ma were obtained,respectively.Obviously the age of the vein constrains the lower limit of the sequence.Conclusion: Therefore,we suggest that the formation age of the Formation Complex c of the Ordovician-Silurian sequence was ca.420 Ma,i.e.,late Silurian.In combination of two zircon U-Pb single-peak ages of 427 Ma and 428 Ma of the Formation Complex b of the sequence (Song Dongfang et al.,2016),we conclude that the sequence formed in Silurian,and the previous Ordovician-Silurian sequence were in fact deposited as Silurian strata.Both rock formations and geochemistry demonstrate that the sequence originally formed in the fore-arc basin associated with subduction of the early Paleozoic Paleo-Asian Ocean to the Dunhuang Massif to the south.
keywords:Beishan orogenic belt  Ordovician-Silurian  gneiss  schist  LA-ICP-MS zircon U-Pb dating
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