川西松林口岩体锆石U-Pb定年及其地球化学特征
|
摘要
松林口岩体位于松潘—甘孜造山带中东部,为确定岩体的侵位时代和地球化学特征,通过镜下薄片观察、主微量元素分析以及锆石U-Pb测年,对松林口岩体进行了研究。结果表明,松林口岩体由二长花岗岩体和花岗闪长岩体组成,花岗闪长岩锆石206Pb/238U年龄加权平均值为(212. 4±0. 9) Ma (MSWD=0. 66),二长花岗岩锆石206Pb/238U年龄加权平均值为(222. 4±1. 1) Ma (MSWD=0. 39),形成于晚三叠世,由两期次岩浆作用形成;岩石的Si O2含量56. 56%～61. 97%;铝饱和指数A/CNK=0. 93～1. 05,全碱含量3. 78～5. 38,K2O/Na2O=1. 02～1. 68,里特曼指数σ=1. 194～1. 612,样品属于准铝质中—高钾钙碱性岩系列。岩石轻重稀土比值LREE/HREE=5. 22～7. 13,LaN/YbN比值为6. 93～8. 96,轻、重稀土分异较明显,具较强的负Eu异常。岩石Mg#值较高(50. 97～61. 27),w(Rb)/w(Sr)为0. 12～0. 25,Rb-(Y+Nb)图解显示为后碰撞环境。因此,松林口二长花岗岩—花岗闪长岩属后碰撞准铝质中—高钾钙碱性I型花岗岩类。
The songlinkou pluton is located in the mid-eastern Songpan-Ganzi orogenic belt.It was studied by microscopical observation,major and trace element analysis and zircon U-Pb dating,in order to determine the emplacement age and geochemical characteristics of the pluton.The results show that the Songlinkou pluton is composed of monzonitic granite and granodiorite which formed by two stages of magmatism in the late Triassic,the weighted mean age of zircon of granodiorite is 212.4±0.9 Ma(MSWD=0.66),and the weighted mean age of zircon of monzonitic granite is 222.4±1.1 Ma(MSWD=0.39).The pluton content of SiO_2 is 56.56%～61.97%,A/CNK value is 0.93～1.05,total alkali 3.78～5.38,K_2O/Na_2O 1.02～1.68,Rittmann index 1.194～1.612,so that the rocks belong to metaperaluminous mid-high K Calc-alkaline series.The LREE/HREE is 5.22～7.13,and La_N/Yb_N is 6.93～8.96,light and heavy rare earths are distinct,with obvious negative Eu anomalies.The rocks have high Mg#values(50.97～61.27),w(Rb)/w(Sr)is 0.12～0.25,and the Rb-(Y+Nb)diagram shows that it belongs to post-collision environment.Therefore,Songlinkou monzonitic granite-granodiorite belongs to post-collision metaperaluminous mid-high K Calc-alkaline I-type granite.
The songlinkou pluton is located in the mid-eastern Songpan-Ganzi orogenic belt.It was studied by microscopical observation,major and trace element analysis and zircon U-Pb dating,in order to determine the emplacement age and geochemical characteristics of the pluton.The results show that the Songlinkou pluton is composed of monzonitic granite and granodiorite which formed by two stages of magmatism in the late Triassic,the weighted mean age of zircon of granodiorite is 212.4±0.9 Ma(MSWD=0.66),and the weighted mean age of zircon of monzonitic granite is 222.4±1.1 Ma(MSWD=0.39).The pluton content of SiO_2 is 56.56%～61.97%,A/CNK value is 0.93～1.05,total alkali 3.78～5.38,K_2O/Na_2O 1.02～1.68,Rittmann index 1.194～1.612,so that the rocks belong to metaperaluminous mid-high K Calc-alkaline series.The LREE/HREE is 5.22～7.13,and La_N/Yb_N is 6.93～8.96,light and heavy rare earths are distinct,with obvious negative Eu anomalies.The rocks have high Mg#values(50.97～61.27),w(Rb)/w(Sr)is 0.12～0.25,and the Rb-(Y+Nb)diagram shows that it belongs to post-collision environment.Therefore,Songlinkou monzonitic granite-granodiorite belongs to post-collision metaperaluminous mid-high K Calc-alkaline I-type granite.
引文
[1]YIN A,HARRISON T M.The tectonic evolution of Asia[M].Cambridge:Cambridge University Press,1996:486-640.
[2]许志琴,侯立玮,王宗秀,等.中国松潘-甘孜造山带的造山过程[M].北京:地质出版社,1992.XU Zhiqin,HOU Liwei,WANG Zongxiu,et al.Orogenic processes of the Songpan Ganze orogenic belt of China[M].Beijing:Geology Press,1992.(in Chinese)
[3]赖绍聪,赵少伟.川西北塔公石英闪长岩地球化学特征和岩石成因[J].地球科学与环境学报,2015,37(3):1-13.LAI Shaocong,ZHAO Shaowei.Geochemistry and petrogenesis of quartz diorite in Tagong Area of Northwest Sichuan[J].Journal of Earth Sciences and Environment,2015,37(3):1-13.(in Chinese with English abstract)
[4]蔡宏明.松潘-甘孜褶皱带印支期花岗岩类和火山岩类成因及深部作用[D].武汉:中国地质大学,2010.CAI Hongming.Petrogenesis of indosinian granitoids and volcanic rocks in Songpan-Garze fold belt:constrains for deep geologic processes[D].Wuhan:China University of Geosciences,2010.(in Chinese with English abstract)
[5]四川省地质矿产局.四川省区域地质志[M].北京:地质出版社,1991.Sichuan Bureau of Geology and Mineral resources.Regional geological records of Sichuan Province[M].Beijing:Geology Press,1991.(in Chinese)
[6]胡健民,孟庆任,石玉若,等.松潘-甘孜地体内花岗岩锆石SHRIMP U-Pb定年及其构造意义[J].岩石学报,2005,21(3):867-880.HU Jianmin,MENG Qingren,SHI Yuruo,et al.SHRIMP U-Pb dating of zircons from granitoid bodies in the Songpan-Ganzi terrane and its implications[J].Acta Petrologica Sinica,2005,21(3):867-880.(in Chinese with English abstract)
[7]王全伟,王康明,阚泽忠,等.川西地区花岗岩及其成矿系列[M].北京:地质出版社,2008.WANG Quanwei,WANG Kangming,KAN Zezhong,et al.Granite and its metallogenic series in Western Sichuan[M].Beijing:Geology Press,2008.(in Chinese)
[8]刘亚轩,张勤,黄珍玉,等.ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究[J].化学世界,2006,47(1):16-20.LIU Yaxuan,ZHANG Qin,HUANG Zhenyu,et al.Study on determination of 18 trace elements including As,Cr,Ge,V in geochemical samples by ICP-MS[J].Chemical World,2006,47(1):16-20.(in Chinese with English abstract)
[9]吴元伟,周广法,曾现虎.变质锆石成因类型及内部结构、地球化学特征[J].科技创新与应用,2013,(26):128.WU Yuanwei,ZHOU Guangfa,ZENG Xianhu.Genetic types,internal structure and geochemical characteristics of metamorphic zircons[J].Technology Innovation and Application,2013,(26):128.(in Chinese)
[10]PETFORD N,CRUDEN A R,MCCAFFREY K J W,et al.Granite magma formation,transport and emplacement in the Earth's crust[J].Nature,2000,408(6813):669-673.
[11]CHAPPELL B W,WHITE A J R.Two contrasting granite types[J].Pacific Geology,1974,8:173-174.
[12]王德滋,刘昌实,沈渭洲,等.桐庐I型和相山S型两类碎斑熔岩对比[J].岩石学报,1993,9(1):44-54.WANG Dezi,LIU Changshi,SHEN Weizhou,et al.The contrast between Tonglu I-type and Xiangshan S-type clastoporphyritic lava[J].Acta Petrologica Sinica,1993,9(1):44-54.(in Chinese with English abstract)
[13]专少鹏,白春东,毛志芳,等.新疆库地南苏盖提力克晚志留世花岗岩锆石U-Pb年龄、地球化学特征及大地构造意义[J].地质力学学报,2018,24(5):661-669.ZHUAN Shaopeng,BAI Chundong,MAO Zhifang,et al.Zircon U-Pb ages and geochemical characteristics of the Sugaitilike late Silurian granites in southern Kudi,Xinjiang and its geotectonic significance[J].Journal of Geomechanics,2018,24(5):661-669.(in Chinese with English abstract)
[14]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.
[15]ROGER F,MALAVIEILLE J,LELOUP P H,et al.Timing of granite emplacement and cooling in the Songpan-Garzêfold belt(eastern Tibetan Plateau)with tectonic implications[J].Journal of Asian Earth Sciences,2004,22(5):465-481.
[2]许志琴,侯立玮,王宗秀,等.中国松潘-甘孜造山带的造山过程[M].北京:地质出版社,1992.XU Zhiqin,HOU Liwei,WANG Zongxiu,et al.Orogenic processes of the Songpan Ganze orogenic belt of China[M].Beijing:Geology Press,1992.(in Chinese)
[3]赖绍聪,赵少伟.川西北塔公石英闪长岩地球化学特征和岩石成因[J].地球科学与环境学报,2015,37(3):1-13.LAI Shaocong,ZHAO Shaowei.Geochemistry and petrogenesis of quartz diorite in Tagong Area of Northwest Sichuan[J].Journal of Earth Sciences and Environment,2015,37(3):1-13.(in Chinese with English abstract)
[4]蔡宏明.松潘-甘孜褶皱带印支期花岗岩类和火山岩类成因及深部作用[D].武汉:中国地质大学,2010.CAI Hongming.Petrogenesis of indosinian granitoids and volcanic rocks in Songpan-Garze fold belt:constrains for deep geologic processes[D].Wuhan:China University of Geosciences,2010.(in Chinese with English abstract)
[5]四川省地质矿产局.四川省区域地质志[M].北京:地质出版社,1991.Sichuan Bureau of Geology and Mineral resources.Regional geological records of Sichuan Province[M].Beijing:Geology Press,1991.(in Chinese)
[6]胡健民,孟庆任,石玉若,等.松潘-甘孜地体内花岗岩锆石SHRIMP U-Pb定年及其构造意义[J].岩石学报,2005,21(3):867-880.HU Jianmin,MENG Qingren,SHI Yuruo,et al.SHRIMP U-Pb dating of zircons from granitoid bodies in the Songpan-Ganzi terrane and its implications[J].Acta Petrologica Sinica,2005,21(3):867-880.(in Chinese with English abstract)
[7]王全伟,王康明,阚泽忠,等.川西地区花岗岩及其成矿系列[M].北京:地质出版社,2008.WANG Quanwei,WANG Kangming,KAN Zezhong,et al.Granite and its metallogenic series in Western Sichuan[M].Beijing:Geology Press,2008.(in Chinese)
[8]刘亚轩,张勤,黄珍玉,等.ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究[J].化学世界,2006,47(1):16-20.LIU Yaxuan,ZHANG Qin,HUANG Zhenyu,et al.Study on determination of 18 trace elements including As,Cr,Ge,V in geochemical samples by ICP-MS[J].Chemical World,2006,47(1):16-20.(in Chinese with English abstract)
[9]吴元伟,周广法,曾现虎.变质锆石成因类型及内部结构、地球化学特征[J].科技创新与应用,2013,(26):128.WU Yuanwei,ZHOU Guangfa,ZENG Xianhu.Genetic types,internal structure and geochemical characteristics of metamorphic zircons[J].Technology Innovation and Application,2013,(26):128.(in Chinese)
[10]PETFORD N,CRUDEN A R,MCCAFFREY K J W,et al.Granite magma formation,transport and emplacement in the Earth's crust[J].Nature,2000,408(6813):669-673.
[11]CHAPPELL B W,WHITE A J R.Two contrasting granite types[J].Pacific Geology,1974,8:173-174.
[12]王德滋,刘昌实,沈渭洲,等.桐庐I型和相山S型两类碎斑熔岩对比[J].岩石学报,1993,9(1):44-54.WANG Dezi,LIU Changshi,SHEN Weizhou,et al.The contrast between Tonglu I-type and Xiangshan S-type clastoporphyritic lava[J].Acta Petrologica Sinica,1993,9(1):44-54.(in Chinese with English abstract)
[13]专少鹏,白春东,毛志芳,等.新疆库地南苏盖提力克晚志留世花岗岩锆石U-Pb年龄、地球化学特征及大地构造意义[J].地质力学学报,2018,24(5):661-669.ZHUAN Shaopeng,BAI Chundong,MAO Zhifang,et al.Zircon U-Pb ages and geochemical characteristics of the Sugaitilike late Silurian granites in southern Kudi,Xinjiang and its geotectonic significance[J].Journal of Geomechanics,2018,24(5):661-669.(in Chinese with English abstract)
[14]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.
[15]ROGER F,MALAVIEILLE J,LELOUP P H,et al.Timing of granite emplacement and cooling in the Songpan-Garzêfold belt(eastern Tibetan Plateau)with tectonic implications[J].Journal of Asian Earth Sciences,2004,22(5):465-481.