LA-ICPMS Zircon U-Pb Geochronology and Geochemical Characteristics of the Zhangshiying Syenite From South of
详细信息
- 责任者：Li Chuangju (Key Laboratory for Metallogenic Dynamics ; Guangzhou Institute of Geochemistry ; Chinese Academy of Sciences ; Guangzhou 510640 ; China) ; Bao Zhiwei
- 刊名：Geotectonica et Metallogenia
- 出版年：2010
- 卷期：34(3)
- 关键词：正长岩 ; syenites ; 岩石地球化学 ; lithogeochemistry ; 河南 ; Henan Province
- 页码：p.435-443
- 图表：5 illus., 3 tables, 46 refs.
- 分类号：08801
- issnNo：ISSN1001-1552
- isbnNo：CN44-1595/P
摘要
The Zhangshiying syenite is located to the south of Wuyang,Henan Province,and tectonically on the southern margin of the North China craton.The syenite intrusion consists mainly of quartz monzonite and quartz syenite.The rocks are of metaluminous and high-K-shoshonitic（Al2O3=14.8%16.7%,A/CNK=0.981.10,K2O/Na2O=1.001.43）,which are rather high in rare earth elements（ranging from 261.7μg/g to 381.0μg/g）,and characterized by relative enrichment of LREE with（La/Yb）N ratio of 2850 and weak negative Eu anomalies（Eu/Eu=0.73 0.87）,and show smooth right dipping chondrite normalized REE patterns.The rocks are significantly depleted in Sr,Ba,Nb,Ta and relatively enriched in Th and U.The isotopic compositions of the rocks strongly suggest a crustal origin regarding the high（87Sr/86Sr）i ratios（0.709）,low εNd（t） value（-13.9-19.9） with Nd model ages range from 1.48Ga to 2.10Ga.LA-ICP-MS U-Pb zircon dating gives a crystallization age of（124.2±0.50）Ma.The syenite was formed in early Cretaceous under large-scale lithospheric thinning and transformation tectonic regime of the North China craton.Trace elements and isotopic characteristics of the rocks suggest that the magma was generated through partial melting of the lower crust with involvement of juvenile mantle material.The syenite might have been formed through partial melting of the lower crust coupled with involvement of juvenile mantle material and high degree fractional crystallization,which was triggered by underplating of asthenospheric mantle magma under the extensive extension and lithospheric thinning tectonic settings.