Abstract：By investigating the geochronology and petrogeochemistry of monzonitic granite in Ganjin Mountain, Ejinaqi, Inner Mongolia, the intruding age and tectonic background are discussed. The zircon U-Pb weighted average age is considered to be (276.63±0.84) Ma by using LA-ICP-MS method, constraining its formation age to be Early Permian. Lithological and geochemical characteristics indicate that the monzonitic granite belongs to subaluminous-peraluminous and calc-alkaline series, with A/CNK ratios of 0.97-1.15 and σ values of 1.64-1.96. The monzonitic granite is rich in large ion lithophyte elements (LILE, e.g., Rb, Ba, Sr), high field strength elements (HFSE, e.g., Th, U, Zr), and LREE with negative euanomolies on the chondrite-normalized diagram, and its LREEs and HREEs are not obviously differentiated. They share affinities with syn-orogenic I-type granites, indicating they formed in a continental arc setting. It is suggested that the monzonitic granite was generated during late Hercynian movement in Ganjin area. The time that terranes on both sides of the Hongshishan-Lujing rifting belt converged was limited to Early Permian.
[1] 何世平,任秉琛,姚文光,等.甘肃内蒙古北山地区构造单元划分[J].西北地质,2002,35(4):30-40. [2] 左国朝,刘义科,刘春燕.甘新蒙北山地区构造格局及演化[J].甘肃地质学报,2003,12(1):1-15. [3] 龚全胜,刘明强,梁明宏,等.北山造山带大地构造相及构造演化[J].西北地质,2003,36(1):11-17. [4] 何世平,周会武,任秉琛,等.甘肃内蒙古北山地区古生代地壳演化[J].西北地质,2005,38(3):6-15. [5] 黄增保,金霞.甘肃红石山蛇绿岩地球化学特征及构造环境[J].地质科学,2006,41(4):601-611. [6] 聂凤军,江思宏,赵省民,等.北山地区照壁山金矿床地质特征及成因[J].地质科学,2002,37(2):207-218. [7] 杨合群,李英,李文明,等.北山花岗岩S型/I型空间变化规律及含矿性[J].地球学报,2009,30(5):627-633. [8] 杨合群,李英,赵国斌,等.北山蛇绿岩特征及构造属性[J].西北地质,2010,43(1):26-36. [9] 杨合群,李英,赵国斌,等.新疆-甘肃-内蒙古衔接区地层对比及其意义[J].西北地质,2009,42(4):60-75. [10] Ao S J,Xiao W J,Han C M,et al.Geochronology and geochemistry of Early Permian mafic-ultramafic complexes in the Beishan area,Xinjiang,NW China:implications for late Paleozoic tectonic evolution of the southern Altaids[J].Gondwana Research,2010,18(2/3):466-478. [11] 甘肃省地质局地质力学区域地质测量队.中华人民共和国区域地质调查报告:六驼山幅(1∶20万)(K-47-16)[R].兰州:甘肃省地质局地质力学区域地质测量队,1979. [12] 内蒙古地质矿产勘查院.内蒙古 1∶5 万红梁子(K47E011013)、沙多山(K47E011014)、红旗山(K47E012013)、蓬勃山幅(K47E012014)区域地质矿产调查[R].2015. [13] Liu Y S,Hu Z C,Gao S,et al.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J].Chemical Geology,2008,257(1/2):34-43. [14] 李永军,杨高学,李鸿,等.新疆伊宁地块晚泥盆世火山岩的确认及其地质意义[J].岩石学报,2012,28(4):1225-1237. [15] 毛景文,李红艳,裴荣富,等.千里山花岗岩体地质地球化学及与成矿关系[J].矿床地质,1995,14(1):12-25. [16] 甘肃省地质局地质力学区域测量队.中华人民共和国区域地质调查报告:黑鹰山幅(K-47-15)[R].兰州:甘肃省地质局地质力学区域测量队,1977. [17] Barbarin B.A review of the relationships between granitoid types,their origins and their geodynamic environments[J].Lithos,1999,46(3):605-626. [18] Pearce J A,Harris N B W,Tindle A G.Trace element discrimination diagrams for the tectonic interpretation of granitic rocks[J].Journal of Petrology,1984,25(4):956-983. [19] 李昌年.火成岩微量元素岩石学[M].武汉:中国地质大学出版社,1992:97-109. [20] Batchelor R A,Bowden P.Petrogenetic interpretation of granitoid rock series using multicationic parameters[J].Chemical Geology,1985,48(1/4):43-55.
2017, Vol. 4 
