西藏中仓蛇绿混杂岩中辉长岩锆石U-Pb定年及其地质意义
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摘要
作为大洋演化的残余,蛇绿混杂岩的形成时代是确定缝合带构造演化的重要依据.中仓蛇绿混杂岩位于狮泉河-永珠-嘉黎蛇绿混杂岩带西段,是达查沟地区区域地质调查过程中新发现的,主要由变质橄榄岩、堆晶辉长岩和辉长岩墙组成.本文应用LA-ICP-MS锆石U-Pb技术,对中仓蛇绿混杂岩中堆晶辉长岩和辉长岩墙进行了测年,分别获得(116.1±1.8)Ma和(113.4±1.7)Ma,该年龄代表了中仓蛇绿混杂岩的形成时代.结合前人的研究成果,初步认为狮泉河-永珠-嘉黎蛇绿混杂岩带在早白垩世仍处于弧后盆地的演化阶段.
As relicts of oceanic evolution, the formational age of ophiolitic mélange is an important evidence for pinning down the tectonic evolution of suture. Located in the western part of Shiquanhe-Yongzhu-Jiali ophiolitic mélange belt,Zhongcang ophiolitic mélange was newly discovered during regional geological surveying in Dachagou area. Zhongcang ophiolitic mélange mainly consists of metamorphic peridotite, cumulate gabbro, and gabbro dike. LA-ICP-MS technique is applied to U-Pb zircon dating of the gabbro from Zhongcang ophiolitic mélange. and the ages of cumulate gabbro and gabbro dike as( 116. 1 ± 1. 8) Ma and( 113. 4 ± 1. 7) Ma respectively are obtained. The ages stand for the formation time of Zhongcang ophiolitic mélange. Combined with previous studies, this research tentatively proposes that Shiquanhe-YongzhuJiali ophiolitic mélange belt was probably still in back-arc basin′s evolutional stage in Early Cretaceous.
As relicts of oceanic evolution, the formational age of ophiolitic mélange is an important evidence for pinning down the tectonic evolution of suture. Located in the western part of Shiquanhe-Yongzhu-Jiali ophiolitic mélange belt,Zhongcang ophiolitic mélange was newly discovered during regional geological surveying in Dachagou area. Zhongcang ophiolitic mélange mainly consists of metamorphic peridotite, cumulate gabbro, and gabbro dike. LA-ICP-MS technique is applied to U-Pb zircon dating of the gabbro from Zhongcang ophiolitic mélange. and the ages of cumulate gabbro and gabbro dike as( 116. 1 ± 1. 8) Ma and( 113. 4 ± 1. 7) Ma respectively are obtained. The ages stand for the formation time of Zhongcang ophiolitic mélange. Combined with previous studies, this research tentatively proposes that Shiquanhe-YongzhuJiali ophiolitic mélange belt was probably still in back-arc basin′s evolutional stage in Early Cretaceous.
引文
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[20]XU M,LI C,WU Y,et al.The petrology,geochemistry,and petrogenesis of E-MORB-type mafic rocks from the Guomangco ophiolitic mélange,Tibet[J].Acta Geologica Sinica(English Edition),2014,88(5):1437-1453.
[21]王永胜,曲永贵,吕鹏,等.西藏永珠蛇绿岩带地质特征[J].吉林地质,2003,22(2):1-14.
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[23]唐峰林,黄建村,罗小川,等.藏北阿索构造混杂岩的发现及其地质意义[J].东华理工学院学报,2004,27(3):245-250.
[24]曲永贵,王永胜,段建祥,等.中华人民共和国区域地质调查报告多巴区幅比例尺1∶250000[M].武汉:中国地质大学出版社,2011.
[2]ZHU D,ZHAO Z,NIU Y,et al.The Lhasa Terrane:Record of a microcontinent and its histories of drift and growth[J].Earth and Planetary Science Letters,2011,301(1/2):241-255.
[3]和钟铧,杨德明,王天武.西藏嘉黎断裂带凯蒙蛇绿岩的年代学、地球化学特征及大地构造意义[J].岩石学报,2006,22(2):653-660.
[4]潘桂棠,莫宣学,侯增谦,等.冈底斯造山带的时空结构及演化[J].岩石学报,2006,22(3):521-533.
[5]张玉修.班公湖-怒江缝合带中西段构造演化[D].广州:中国科学院研究生院(广州地球化学研究所),2007:23-50.
[6]陈文,万渝生,李华芹,等.同位素地质年龄测定技术及应用[J].地质学报,2011,85(11):1917-1947.
[7]樊帅权,史仁灯,丁林,等.西藏改则蛇绿岩中斜长花岗岩地球化学特征、锆石U-Pb年龄及构造意义[J].岩石矿物学杂志,2010,29(5):467-478.
[8]郑有业,许荣科,马国桃,等.锆石SHRIMP测年对狮泉河蛇绿岩形成和俯冲的时间约束[J].岩石学报,2006,22(4):895-904.
[9]徐建鑫,李才,范建军,等.西藏改则县拉果错蛇绿岩构造属性:来自岩石学、地球化学、年代学及Lu-Hf同位素的制约[J].地质通报,2018,37(8):1541-1553.
[10]ZENG Y C,XU J F,CHEN J L,et al.Geochronological and geochemical constraints on the origin of the Yunzhug ophiolite in the Shiquanhe-Yunzhug-Namu Tso ophiolite belt,Lhasa Terrane,Tibetan Plateau[J].Lithos,2017,300/301:250-260.
[11]XU M,LI C,XU W,et al.Petrology,geochemistry and geochronology of gabbros from the Zhongcang ophiolitic mélange,central Tibet:Implications for an intra-oceanic subduction zone within the Neo-Tethys Ocean[J].Journal of Earth Science,2014,25(2):224-240.
[12]YIN A,HARRISON T M.Geologic evolution of the HimalayanTibetan Orogen[J].Annual Review of Earth and Planetary Sciences,2000,28(1):211-280.
[13]LI C,ZHAI Q,DONG Y,et al.High-pressure eclogiteblueschist metamorphic belt and closure of paleo-tethys ocean in central Qiangtang,Qinghai-Tibet plateau[J].Journal of Earth Science,2009,20(2):209-218.
[14]XU M,LI C,XU W,et al.Petrology,geochemistry and geochronology of gabbros from the Zhongcang ophiolitic mélange,central Tibet:Implications for an intra-oceanic subduction zone within the Neo-Tethys Ocean[J].Journal of Earth Science,2014,25(2):224-240.
[15]陈莉,徐军,苏犁.场发射环境扫描电子显微镜上阴极荧光谱仪特点及其在锆石研究中的应用[J].自然科学进展,2005,15(11):1403-1408.
[16]LUDWIG K R.ISOPLOT/Ex,version 3,a geochronological toolkit for microsoft excel[M].Berkeley:Berkeley Geochronological Center Special Public,2003.
[17]HOSKIN P W O,SCHALTEGGER U.The composition of zircon and igneous and metamorphic petrogenesis[J].Reviews in Mineralogy and Geochemistry,2003,53(1):27-62.
[18]SUN S S,MCDONOUGH W F.Chemical and isotopic systematics of oceanic basalts:Implications for mantle composition and processes[J].Geological Society,London,1989,42(1):313-345.
[19]曾庆高,毛国政,王保弟,等.中华人民共和国区域地质调查报告日干配错幅比例尺1∶250000[M].武汉:中国地质大学出版社,2011.
[20]XU M,LI C,WU Y,et al.The petrology,geochemistry,and petrogenesis of E-MORB-type mafic rocks from the Guomangco ophiolitic mélange,Tibet[J].Acta Geologica Sinica(English Edition),2014,88(5):1437-1453.
[21]王永胜,曲永贵,吕鹏,等.西藏永珠蛇绿岩带地质特征[J].吉林地质,2003,22(2):1-14.
[22]朱志勇.西藏永珠-纳木错蛇绿岩地球化学特征及其构造环境[D].长春:吉林大学,2004:1-55.
[23]唐峰林,黄建村,罗小川,等.藏北阿索构造混杂岩的发现及其地质意义[J].东华理工学院学报,2004,27(3):245-250.
[24]曲永贵,王永胜,段建祥,等.中华人民共和国区域地质调查报告多巴区幅比例尺1∶250000[M].武汉:中国地质大学出版社,2011.