Geochronology and Geochemistry of the Mesoproterozoic Panhe Syenites in the Southern Margin of North China Craton and Its Tectonic Implications
详细信息
- 责任者：Zeng Lingjun (Key Laboratory for Mineralogy and Metallogeny ; Guangzhou Institute of Geochemistry ; Chinese Academy of Sciences ; Guangzhou 510640 ; China) ; Bao Zhiwei
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：正长岩 ; syenites ; 华北地区 ; North China
- 页码：p.2425-2436
- 图表：11 illus., 3 tables, 64 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
It has long been an issue of debate whether the North China Craton was assembled into the Columbia or Nuna supercontinent and experienced breakup processes congruent with the other cratons. Controversy regarding the breakup processes of the North China Craton is partly due to the known Mesoproterozoic anorogenic magmatisms are mainly distributed in the northern margin of North China Craton. Series of Mesoproterozoic syenite veins of nearly EW-striking were discovered recently in the southern margin of North China Craton at the Panhe area in Lushi County,Henan Province. The syenites are composed of silica-saturated biotite syenite and silica-undersaturated nepheline syenite,within which the later only occurs locally. LA-ICP-MS zircon U-Pb dating of the biotite syenite yields a concordia age of 1469 ± 8Ma ( MSWD = 1. 4) . The Panhe syenites are per-alkaline and peraluminous with SiO 2 and Al 2 O 3 contents vary in ranges of 51. 3% ～ 65. 7% and 18. 7% ～ 20. 0% ,respectively. The syenites exhibit steep right declining REE patterns ( La / Yb) N = 14. 5 ～ 34. 5) with significant negative Eu anomalies ( δEu = 0. 2 ～ 0. 3) ,enriched in LILE ( Rb,Ba,Th,etc. ) and HFSE ( Nb,Ta,Nd,Tb) ,and considerably depleted in Sr,Ti,and P. The ε Hf ( t) values range from -14. 79 to +8. 16 and Hf model ages vary in range of 2. 93Ga to 1. 74Ga,which suggest that the syenites might have been derived from partial melting of the lithospheric mantle that was fertilized by delaminating of thickened crust,and underwent assimilation of silica-rich crustal material and fractional crystallization ( AFC) processes. The syenites were formed under extension tectonic regime. It means that the southern margin of North China Craton records the extension process of the NCC at Mesoproterozoic. And the process might be related to the breakup of the Columbia supercontinent.