今天是2019年07月19日

东阿拉善地块前寒武纪变质基底中晚古生代变质杂岩:来自波罗斯坦庙杂岩LA-ICP-MS锆石U-Pb定年的新证据

DOI:10.3799/dqkx.2018.386

作者:邹雷,刘平华,田忠华,冀-磊,施建荣

联系地址:中国地质科学院地质研究所,北京 100037

摘要:波罗斯坦庙杂岩是东阿拉善地块典型的中-高级变质杂岩之一,它的深入研究对进一步认识阿拉善地块起源、形成与演化过程具有十分重要的科学意义.通过对波罗斯坦庙杂岩中石英闪长质片麻岩、斜长角闪岩与花岗伟晶岩的野外观察、岩石学与锆石UPb定年发现,波罗斯坦庙杂岩中石英闪长质片麻岩、斜长角闪岩与花岗伟晶岩的岩浆锆石加权平均年龄分别为284±2 Ma、278±3 Ma,276±2 Ma、271±3 Ma与242±7 Ma,该组年龄被解释为其原岩成岩时代.石英闪长质片麻岩与斜长角闪岩中变质锆石加权平均年龄分别为274±6 Ma 、272±5 Ma与269±3 Ma、 268±2 Ma,代表它们遭受了晚古生代变质作用的时间.综合以上分析与前人研究资料,初步认为以往曾被认为是新太古代-古元古代的波罗斯坦庙杂岩,实际上可能是一个古元古代-晚古生代中-高级变质杂岩,并遭受了280~260 Ma 角闪岩相变质作用,指示它们曾被卷入到中亚造山带晚古生代造山作用过程.

关键字:东阿拉善地块;波罗斯坦庙杂岩;晚古生代;锆石U-Pb定年;岩石学

Late Paleozoic Metamorphic Complex of Precambrian Metamorphic Basement from Eastern Alxa Block: New Evidence from Zircon LA-ICP-MS U-Pb Dating of Boluositanmiao Complex

Author:Zou Lei ,Liu Pinghua ,Tian Zhonghua ,Ji Lei ,Shi Jianrong

Author Address:Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China

Abstract:The Boluositanmiao complex is a typical intermediate to highgrade metamorphic complex in the Alxa block, which is significant for better understanding of the origin, formation and evolution of Alxa block. In this paper, it presents a detailed study on the field geological observation, petrology and zircon UPb dating of the quartz dioritic gneisses, amphibolites and granitic pegmatites of the Boluositanmiao complex, and the results indicate that the magmatic zircons from the quartz dioritic gneisses, amphibolites and granitic pegmatites record the mean ages of 284±2 Ma and 278±3 Ma, 276±2 Ma and 271± 3 Ma , and 242±7 Ma, respectively, which is interpreted as the protolith timing of the complex in our study, rather than NeoacheanPaleoproterozoic as suggested in previous studies.Moreover, the metamorphic zircons from the quartz dioritic gneisses and amphibolites also record the mean ages of 274±6 Ma and 272±5 Ma, and 269±3 Ma and 268±2 Ma, respectively, which is interpreted as the Late Paleozoic metamorphic timing of the complex.In conclusion, it is proposed that the Boluositanmiao complex mainly consists of the Paleoproterozoic Late Paleozoic geological bodies, rather than Neoarchean Paleoproterozoic rocks. Besides, they have also undergone 280-260Ma amphibolite facies metamorphism, indicating that the complex could be related to the Late Paleozoic orogenesis of the central Asian orogenic belt.

Keyword:eastern Alxa block; Boluositanmiao complex; Late Paleozoic; zircon U-Pb dating; petrology.

 

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作者简介:邹雷(1994-),男,硕士研究生,变质岩石学专业.ORCID: 0000-0001-7515-9073.E-mail: zoulei0801@163.com

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