Depositional Ages and Tectonic Implications for South Liaohe Group from Kuandian Area in Northeastern Liaodong Peninsula, Northeast China
详细信息
- 责任者：Meng En (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Liu Fulai
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：铀—铅计时 ; U-Pb dating ; 辽河群 ; Liaohe Group ; 辽东半岛 ; Liaodong Peninsula
- 页码：p.2465-2480
- 图表：7 illus., 2 tables, 70 refs.
- 分类号：1200
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
South Liaohe Group widely occurred in Kuandian area of northeastern Liaodong Peninsula. LA-ICP-MS zircon U-Pb ages and micro trace-elements composition for the biotite-quartz schist,tourmaline-bearing leucoleptite and granitic gneiss from this group were carried out with the aim of restricting the ages of the protolith and metamorphism and the tectonic nature of the Jiao-Liao-ji Belt. The cathodoluminescence ( CL) images show that the grain could be divided into three groups,i. e. ,one group with features of showing low luminescence ( cinereous) and structureless,one group with a structureless core surrounded by a cinereous rim,similar to grains of the former group,and the final ones with cores displaying striped absorption or fine-scale oscillatory growth zoning. The trace-element results suggest that the first group have low Th ( 51. 09 × 10 - 6 ～ 85. 15 × 10 - 6 ) and Th/U ratios ( 0. 06 ～ 0. 07) ,indicating a metamorphic origin,the second ones have high Th ( 97. 68 × 10 - 6 ～ 219. 7 × 10 - 6 ) and Th/U ratios ( 0. 21 ～ 0. 27) ,implying a magmatic origin,and the last ones show higher Th ( 249. 6 ～ 469. 4 × 10 - 6 ) and Th/U ( 0. 60 ～0. 74) ,suggesting a typical magmatic origin. The dating results show that the 207 Pb / 206 Pb ages of the two former ranging from 1878Ma to 1903Ma ( peak at 1885Ma) and from 2011Ma to 2043Ma ( peak at 2035Ma) ,respectively,suggesting that the protoliths of the South Liaohe Group was deposited at some time after 2035Ma and the peak metamorphism occurred at 1885Ma. Besides,the ages of the third ones vary from 2082Ma to 3285Ma,mainly consistent with the formation of regionally distributed granitoids and coeval volcanic rocks in the Jiao-Liao-Ji Belt and the granitoids of the basement,suggesting that these rocks provided the major component of the provenance for the South Liaohe Group. These new zircons ages for the South Liaohe Group and recent data for the Liaoji granite, combined with lithological,structural and metamorphic considerations,indicate that South Liaohe Group from Kuandian area could form under an extensional environment.