摘要
叠布斯格杂岩作为阿拉善地块变质程度最高、形成时代最老的变质岩系,是进一步深入认识阿拉善地块形成、演化与构造亲缘性的最佳对象.本文对叠布斯格杂岩中黑云斜长片麻岩开展了系统的野外地质调查、岩相学观察和锆石U-Pb年代学研究.碎屑锆石U-Pb定年和野外地质调查表明,叠布斯格杂岩中黑云斜长片麻岩碎屑锆石年龄介于2 177~2 010 Ma,最小年龄峰值为2 050 Ma,结合变质锆石年龄数据,限定其沉积时代在2 050~1 969 Ma之间.区域对比研究表明,阿拉善地块叠布斯格杂岩中黑云斜长片麻岩与西阿拉善地块龙首山杂岩、华北克拉通孔兹岩带(尤其是孔兹岩带西部)中的变沉积岩系在沉积时代与源区特征上具有高度的一致性.此外,变质锆石U-Pb定年和微量元素分析表明,叠布斯格杂岩中黑云斜长片麻岩记录了古元古代晚期1 969~1 811 Ma连续的变质年龄.对比分析阿拉善地块与孔兹岩带变沉积岩系的碎屑锆石年龄谱系-变质时代表明,阿拉善地块与孔兹岩带在古元古代可能具有相同的沉积-变质演化历史,在古元古代期间阿拉善地块应是华北克拉通孔兹岩带的西延部分.
The Diebusige Complex, as the oldest metamorphic complex with the highest metamorphic grade from the Alxa Block,is an excellent object to investigate the formation, evolution, and tectonic affinity of the Alxa Block. This paper presents comprehensive studies on the biotite-plagioclase gneiss from the Diebusige Complex, including detailed field investigation,petrological observation and LA-ICP-MS zircon U-Pb dating. The detrital zircon U-Pb dating indicates that the ages of the detrital zircons from the biotite-plagioclase gneiss in the Diebusige Complex are between 2 177 and 2 010 Ma, with a peak age of ca. 2 050 Ma. Combined with the maximum metamorphic age of 1 969 Ma, it is proposed that the depositional timing of the biotiteplagioclase gneiss is 2 050~1 969 Ma. Comprehensive comparative analysis shows that the depositional timing and provenance of the biotite-plagioclase gneiss in the Diebusige Complex is highly consistent with the meta-sedimentary rocks from the Longshoushan Complex and the Khondalite Belt(especially the western part of the Khondalite Belt). In addition, metamorphic zircon U-Pb dating and REE analyses indicate that the metamorphic zircons of the biotite-plagioclase gneiss yield continuous ages of 1 969~1 811 Ma. Based on the similarities in the detrital zircon age patterns and metamorphic timing of the meta-sedimentary rocks from the Khondalite Belt in Paleoproterozoic, it is suggested that the Alxa Block should be the western part of the Khondalite Belt in Paleoproterozoic.
作者
邹雷
刘平华
刘利双
王伟
田忠华
Zou Lei;Liu Pinghua;Liu Lishuang;Wang Wei;Tian Zhonghua(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,CAS,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100039,China;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第9期3313-3329,共17页
Earth Science
基金
国家自然科学基金项目(Nos.41672191,41972205)
国家重点研发计划重点专项项目(No.2017YFC0601301)
中国地质调查局地质大调查项目(No.DD20190003)。
