Geochronology,geochemistry and Hf isotope of monzogranite in Niubiziliang of Qinghai  

作　　者：JIANG Hefang SUN Fengyue LI Liang LI Ruihua YU Lu WANG Fei SHEN Dali JIANG Hefang;SUN Fengyue;LI Liang;LI Ruihua;YU Lu;WANG Fei;SHEN Dali(College of Earth Sciences, Jilin University, Changchun 130061, China;MLR Key Laboratory of Metallogeny and Mineral Resources Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences, Beijing 100037, China;School of Earth and Space Sciences, Perking University, Beijing 100871, China;Qinghai Nuclear Industrial Geology Bureau,Xining 810008,China)

机构地区：[1]College of Earth Sciences, Jilin University, Changchun 130061, China [2]MLR Key Laboratory of Metallogeny and Mineral Resources Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences, Beijing 100037, China [3]School of Earth and Space Sciences, Perking University, Beijing 100871, China [4]Qinghai Nuclear Industrial Geology Bureau,Xining 810008,China

出　　处：《Global Geology》2016年第3期153-163,共11页世界地质（英文版）

摘　　要：Zircon U-Pb dating, whole-rock geochemical analyses and Hf isotope are undertaken for the monzogranite in Niubiziliang area with the aim of constraining its formation time,petrogenesis and the regional tectonic setting. The zircons from monzogranite are euhedral-subhedral in shape,and display rhythm growth zoning,indicating a magmatic origin. LA-ICP-MS zircon U-Pb dating indicates the monzogranite formed most probably in the Late Devonian( 359. 0 ± 2. 6 Ma). The monzogranite has Si O2= 74. 69%--76. 11%,Al2O3=12. 07%--12. 81%,Na2 O + K2 O = 8. 24%--8. 70%,Na2 O / K2 O = 0. 60--0. 68,A / CNK > 1,which shows that it belongs to high-Si and high-K weakly peraluminous calc-alkaline series. The monzogranite is enriched in K,Rb,Th( LILEs) and La,Ce,Sm,Nd( LREEs); and depleted in Ba,U( HREEs) and Ta,Nb( HFSEs).Their zircon εHf( t) values range from 1. 21 to 3. 46,in response to their two-stage Hf model ages( TDM2) ranging from 1 034 Ma to 1 159 Ma,respectively,indicating that the primary magma was derived from the young crust in Meso-Neoproterozoic. Combined with the regional geological evolution background,it is considered that the Niubiziliang monzogranite formed the closure of North Qaidam ocean,which was the stretching stage product after the collision between Qaidam block and Qilian block.Zircon U-Pb dating, whole-rock geochemical analyses and Hf isotope are undertaken for the monzogranite in Niubiziliang area with the aim of constraining its formation time,petrogenesis and the regional tectonic setting. The zircons from monzogranite are euhedral-subhedral in shape,and display rhythm growth zoning,indicating a magmatic origin. LA-ICP-MS zircon U-Pb dating indicates the monzogranite formed most probably in the Late Devonian（ 359. 0 ± 2. 6 Ma）. The monzogranite has Si O2= 74. 69%--76. 11%,Al2O3=12. 07%--12. 81%,Na2 O ＋ K2 O = 8. 24%--8. 70%,Na2 O / K2 O = 0. 60--0. 68,A / CNK 〉 1,which shows that it belongs to high-Si and high-K weakly peraluminous calc-alkaline series. The monzogranite is enriched in K,Rb,Th（ LILEs） and La,Ce,Sm,Nd（ LREEs）; and depleted in Ba,U（ HREEs） and Ta,Nb（ HFSEs）.Their zircon εHf（ t） values range from 1. 21 to 3. 46,in response to their two-stage Hf model ages（ TDM2） ranging from 1 034 Ma to 1 159 Ma,respectively,indicating that the primary magma was derived from the young crust in Meso-Neoproterozoic. Combined with the regional geological evolution background,it is considered that the Niubiziliang monzogranite formed the closure of North Qaidam ocean,which was the stretching stage product after the collision between Qaidam block and Qilian block.

关 键 词：magmatic zircon geochemistry dating isotope depleted enriched crust probably geochemical 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]