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Geoscience ›› 2011, Vol. 25 ›› Issue (6): 1032-1046.

• Petrology and geochemistry • Previous Articles     Next Articles

Evolution of Yanshanian Granites in Southern Marginal Region of North China Block:A Case Study of XiaoqinlingWaifangshan Area

 WANG  Zhen-Jiang-1, 2 , XU  Jian-Chang-2, FENG  Jian-Zhi-2, 3 , QI  Dong-Mei-4, YANG  Gang-4, SUN  Wei-Zhi-2, 3   

  1. 1 Key Laboratory of Gold and Silver Polymetallic Mineralization Series and Deep Prediction of Henan, Luoyang,Henan471023, China;
    2No1 Geological Survey Team,Exploration and Development Bureau of Geological and Mineral Resources of Henan Province,
    Luoyang,Henan471023, China;3Luoyang Institute of Geological Survey,Luoyang, Henan471023, China;
    4Faculty of Earth Sciences,China University of Geosciences,Wuhan,Hubei430074, China
  • Received:2011-06-29 Revised:2011-10-14 Online:2011-12-14 Published:2011-12-15

Abstract:

According to the time and space distribution characteristics of Mesozoic granites in XiaoqinlingWaifangshan  area in southern marginal region of North China block,the forming process of the Mesozoic granites can be divided into 160-155 Ma(Ⅰ), 150-125 Ma(Ⅱ), and 120-110 Ma(Ⅲ),not identical with largescale magmatic activity periods of North China. The geochemical evolution of the three periods of granites are special: geochemical  characteristics of Ⅰ and Ⅲ periods of granites are very similar,and they are abnormally high content of K, obvious negative Eu anomaly and weak heavy rareearth fractionation, belonging to Atype granites. Ⅱ period of granite is metaluminousperaluminous and high potassium calcium alkaline series granite, and is rich in big ion lithophile element,such as K, U, and Th,lack in the high field element. P2O5 content decrease with the increasing of SiO2 content, belonging to Itype granite. For the contents of most samples, Sr content is more than 300.00×10-6,Y content is less than 19.00×10-6 and Yb content is less than 1.90×10-6, showing the geochemical characteristics of adakite rock. From early to late period,Ⅰ,Ⅱ and Ⅲ periods of granites show the trend of Atype-Itype-Atype. I period of granite formed in local extensional environment under the extrusion tectonic background. Ⅱ period of granite formed in tectonic setting transition period,being the product of the lower crust melting led by thickening crust. Ⅲ period of granite formed from plate stabilization, lithosphere stretching, and decompression and melting of the lower crust rocks, after Yangtze and North China continental blocks fitting.

Key words: XiaoqinlingWaifangshan, Yanshanian granite, magmatic evolution, southern marginal region of North China block