东昆仑没草沟蛇绿岩地球化学、LA-ICP-MS锆石U-Pb年龄及其地质意义
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摘要
重点介绍了没草沟蛇绿岩岩石组合、地球化学特征等,并对该蛇绿岩构造背景进行了讨论。该蛇绿岩位于青海省格尔木市,构造上处于东昆仑复合造山带西段,岩石组合由变质基性玄武岩及少量辉绿岩、辉长岩、变质橄榄岩、辉橄岩等组成。岩石主量和微量元素特征显示该蛇绿岩与俯冲无关,属正常洋中脊型玄武岩。前人开展的地质调查表明,该蛇绿岩形成于晚奥陶世。通过对没草沟蛇绿岩中玄武岩和辉长岩进行LA-ICP-MS锆石U-Pb测年,分别获得了488.2±2.1Ma和500.8±2.2 Ma的年龄数据,确定该蛇绿岩形成时代为中寒武世—早奥陶世。该同位素年龄的获得填补了该地区蛇绿岩无时代依据的空白,同时反映古特斯洋在本区的残留。综合区域地质特征认为,没草沟蛇绿岩早期为初始洋盆环境,晚期有洋脊扩张中心环境的玄武岩形成。寒武纪早期是洋盆发育的全盛期,奥陶纪晚期洋壳发生消减,于晚志留世洋盆基本闭合,后期伴有绿片岩相变质作用。
This paper mainly introduces the rock assemblage and geochemical characteristics of the Meicaogou ophiolite and attempts to discuss the tectonic background of the ophiolite which is located in Golmud City of Qinghai Province and lies in the western part of the East kunlun composite orogenic belt. The rock association is composed of metamorphic basic basalt and a small amount of diabase, gabbro, metamorphic peridotite and augite peridotite. The characteristics of main elements and trace elements indicate that the ophiolite is not related to subduction but belongs to N-MORB. In the past geological survey carried out by previous researchers,it was considered that the ophiolite was formed in Late Ordovician. The LA-ICP-MS zircon U-Pb dating of gabbro and basalt in the Weitogou ophiolite yielded the exact age data of 488.2±2 Ma and 501.1±2.2 Ma. The isotope data have filled the gaps of the ophiolite data in this area, and reflected the existence of remains of the ancient ocean in this area. The comprehensive regional geological characteristics suggest that the early period of the oceanic basin was at the initial stage,but at the late stage basalt was formed in an oceanic ridge expanding center environment. The Early Cambrian period was the flourishing period of the development of the oceanic basin, the late oceanic crust was formed in the late Ordovician period, and the late Silurian basin was basically closed together with later greenschist facies metamorphism.
This paper mainly introduces the rock assemblage and geochemical characteristics of the Meicaogou ophiolite and attempts to discuss the tectonic background of the ophiolite which is located in Golmud City of Qinghai Province and lies in the western part of the East kunlun composite orogenic belt. The rock association is composed of metamorphic basic basalt and a small amount of diabase, gabbro, metamorphic peridotite and augite peridotite. The characteristics of main elements and trace elements indicate that the ophiolite is not related to subduction but belongs to N-MORB. In the past geological survey carried out by previous researchers,it was considered that the ophiolite was formed in Late Ordovician. The LA-ICP-MS zircon U-Pb dating of gabbro and basalt in the Weitogou ophiolite yielded the exact age data of 488.2±2 Ma and 501.1±2.2 Ma. The isotope data have filled the gaps of the ophiolite data in this area, and reflected the existence of remains of the ancient ocean in this area. The comprehensive regional geological characteristics suggest that the early period of the oceanic basin was at the initial stage,but at the late stage basalt was formed in an oceanic ridge expanding center environment. The Early Cambrian period was the flourishing period of the development of the oceanic basin, the late oceanic crust was formed in the late Ordovician period, and the late Silurian basin was basically closed together with later greenschist facies metamorphism.
引文
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[2]王荃,刘雪主.中国西部的古海洋地壳及其大地构造意义[J].地质科学,1976,(1):14-24.
[3]史仁灯.蛇绿岩研究进展、存在问题及思考[J].地质论评,2005,51(6):681-566.
[4]Anonymous.Penrose field conference on ophiolites[J].Geotimes,1972,17:24-25.
[5]Brongniart A.Essai de classi ficatin mineralogique desroches melanges[J].Journal des Mines,1813,XXXIV:190-199.
[6]Miyashiro A.Classification,characteristics,and origin of ophiolites.The Journal of Geology,1975,83(2):249-281
[7]Moores E M.Origin and emplacement of Ophiolites[J].Reviews of Geophysics and Space Physics,1982,20:735-760.
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[10]张进,邓晋福,肖庆辉,等.蛇绿岩研究的最新进展[J].地质通报,2012,32(1):1-12.
[11]Dilek Y,Furnes H.Ophiolite genesis and global tectonics:Geochemical and tectonic fingerprinting of ancient oceanic lithosphere[J].Geological society of America Bulletin,2011,123:387-411.
[12]Pearce J A.Immobile element fingerprinting of ophiolites[J].Elements,2014,10(2):101-108.
[13]肖序常,陈国铭,朱志直.祁连山古蛇绿岩的地质构造意义[J].地质学报,1978,54(1):287-295.
[14]付长垒,闫臻,郭现轻,等.拉脊山口蛇绿混杂岩中辉绿岩的地球化学特征及SHRIMP锆石U-Pb年龄[J].岩石学报,2014,30(6),1695-1706.
[15]李荣社,计文化,赵振明,等.昆仑早古生代造山带研究进展[J].地质通报,2007,26(4):374-382.
[16]宋泰忠,赵海霞,张维宽,等.祁漫塔格地区十字沟蛇绿岩地质特征[J].西北地质,2010,43(4):124-133.
[17]谌宏伟,罗照华,莫宣学,等.东昆仑喀雅克登塔格杂岩体的SHRIMP年龄及其地质意义[J].岩石矿物学杂志,2006,25(1):25-32.
[18]祁生胜.青海省东昆仑造山带火成岩岩石构造组合与构造演化[D].中国地质大学(北京)博士学位论文,2015:1-343.
[19]陈隽璐,黎敦朋,李新林,等.东昆仑祁漫塔格山南缘黑山蛇绿岩的发现及其特征[J].陕西地质,2004,22(2):35-46.
[20]郭通珍,刘荣,陈发彬,等.青海祁漫塔格山乌兰乌球尔斑状正长花岗岩LA-MC-ICPMS锆石U-Pb定年[J].地质通报,2011,30(8):1204-1211.
[21]罗照华,邓晋福,曹永清,等.青海省东昆仑地区晚古生代-早中生代火山活动与区域构造演化[J].现代地质,1999,13(1):51-56.
[22]郭正府,邓晋福,许志琴,等.青藏东昆仑晚古生代末-中生代中酸性火成岩与陆内造山过程[J].现代地质,1998,12(3):344-352.
[23]潘桂棠,肖庆辉,陆松年,等.中国大地构造单元划分[J].中国地质,2002,36(1):1-28.
[24]青海省地质矿产局.青海省岩石地层[M].武汉:中国地质大学出版社,1997.
[25]路凤香,桑隆康,邬金华,等.岩石学[M].北京:地质出版社,2002.
[26]李怀坤,耿建珍,郝爽,等.用激光烧蚀多接收器等离子体质谱仪(LA-MC-ICPMS)测定锆石U-Pb同位素年龄的研究[J].矿物学报,2009,(增刊):600-601.
[27]邱家骧.岩浆岩岩石学[M].北京:地质出版社,1986.
[28]韩磊,张立飞.K和Na在深俯冲板块中的元素化学行为[J].岩石矿物学杂志,2015,34(5):755-766.
[29]Pearce J A.Trace element characteristics of lavas from destructive plate boundaries[C]//Thorpe R S.Andesits.Chichester:Wiley,1982:525-548.
[30]Boynton W V.Geochemistry of the rare earth elements:Meteorite studies[C]//Henderson P.Rare earth element geochemistry.Elservier,1984:63-114.
[31]李昌年.微量元素岩石学[M].武汉:中国地质大学出版社,1992.
[32]Yegodainski G M,Kay R W,Volynets O N,et al.Magnesian andesite in thewesternAleutian Komandorsky region:Implications for slabmelting and processes in themantlewedge[J].Geol.Soc.Amer.Bull.,1995,107:505-519.
[33]Sun S S,McDonough W F.Chemical and isotopic systematicsof oceanic basalts:implications for mantle composition and processes[C]//Saunders A D,Norry M J.Magmatism in the Oceanic Basins,Geological Society Special Publication,1989,42:313-346.
[34]Pearce J A,Role of the sub-continental lithosphere in magma genesis at active continental margins[C]//Hawkesworth C J,Norry M J.Continental basalts and mantle xenoliths.Nantwich:Shiva,1983:230-249.
[35]吴元保,郑永飞.锆石成因矿物研究及其对U-Pb年龄解释的制约[J].科学通报,2004,49(16):1589-1604.
[36]Nasdala L,Wenzel M,Vavra G,et al.Metamictisation of natural zircon:Accumulation versus thermal annealing of radioactivityinduced damage[J].Contributions to Mineralogy and Petrology,2001,141(2):125-144
[37]Pearce J A,Lippard S J,Roberts S.Characteristics and tectonic significance of supra-subduction zone ophiolites[J].Geological Society of London,Special Publications,1984,16(1):74-94.
[38]Dewey J F,Bird J M.Origin and emplacement of the ophiolite suite:Appalachian ophiolites in Newfoundland[J].Journal of Geophysical Research,1971,76(14):3179-3206
[39]邓晋福,肖庆辉,苏尚国,等.火成岩组合与构造环境:讨论[J].高校地质学报,2007,13(3):392-402.
[40]Pearce J A,Cann J R.Tectonic setting of basic volcanic rocks determined using trace element analyses[J].Earth and Planetary Science Letters,1973,19:290-300.(1)
(1)1∶20万不冻泉幅区域地质调查报告.青海省区调综合地质大队,1986.
(2)1∶25万不冻泉幅区域地质调查报告.中国地质大学(武汉), 2003.
(3)青海省格尔木市窑洞山地区两幅1∶5万区域地质调查报告.青海省地质调查院, 2016.
(4)青海省区域地质调查与片区总结成果报告内部资料.青海省地质调查院, 2017.
(5)1∶5万保沟幅、没草沟幅、青办食宿幅区域地质调查报告.青海省地质调查院, 2002.
[2]王荃,刘雪主.中国西部的古海洋地壳及其大地构造意义[J].地质科学,1976,(1):14-24.
[3]史仁灯.蛇绿岩研究进展、存在问题及思考[J].地质论评,2005,51(6):681-566.
[4]Anonymous.Penrose field conference on ophiolites[J].Geotimes,1972,17:24-25.
[5]Brongniart A.Essai de classi ficatin mineralogique desroches melanges[J].Journal des Mines,1813,XXXIV:190-199.
[6]Miyashiro A.Classification,characteristics,and origin of ophiolites.The Journal of Geology,1975,83(2):249-281
[7]Moores E M.Origin and emplacement of Ophiolites[J].Reviews of Geophysics and Space Physics,1982,20:735-760.
[8]张旗,肖序常.中国蛇绿岩研究概述[J].岩石学报,1995,11(增刊):1-9.
[9]张旗,周国庆.中国蛇绿岩[M].北京:科学出版社,2001:1-182.
[10]张进,邓晋福,肖庆辉,等.蛇绿岩研究的最新进展[J].地质通报,2012,32(1):1-12.
[11]Dilek Y,Furnes H.Ophiolite genesis and global tectonics:Geochemical and tectonic fingerprinting of ancient oceanic lithosphere[J].Geological society of America Bulletin,2011,123:387-411.
[12]Pearce J A.Immobile element fingerprinting of ophiolites[J].Elements,2014,10(2):101-108.
[13]肖序常,陈国铭,朱志直.祁连山古蛇绿岩的地质构造意义[J].地质学报,1978,54(1):287-295.
[14]付长垒,闫臻,郭现轻,等.拉脊山口蛇绿混杂岩中辉绿岩的地球化学特征及SHRIMP锆石U-Pb年龄[J].岩石学报,2014,30(6),1695-1706.
[15]李荣社,计文化,赵振明,等.昆仑早古生代造山带研究进展[J].地质通报,2007,26(4):374-382.
[16]宋泰忠,赵海霞,张维宽,等.祁漫塔格地区十字沟蛇绿岩地质特征[J].西北地质,2010,43(4):124-133.
[17]谌宏伟,罗照华,莫宣学,等.东昆仑喀雅克登塔格杂岩体的SHRIMP年龄及其地质意义[J].岩石矿物学杂志,2006,25(1):25-32.
[18]祁生胜.青海省东昆仑造山带火成岩岩石构造组合与构造演化[D].中国地质大学(北京)博士学位论文,2015:1-343.
[19]陈隽璐,黎敦朋,李新林,等.东昆仑祁漫塔格山南缘黑山蛇绿岩的发现及其特征[J].陕西地质,2004,22(2):35-46.
[20]郭通珍,刘荣,陈发彬,等.青海祁漫塔格山乌兰乌球尔斑状正长花岗岩LA-MC-ICPMS锆石U-Pb定年[J].地质通报,2011,30(8):1204-1211.
[21]罗照华,邓晋福,曹永清,等.青海省东昆仑地区晚古生代-早中生代火山活动与区域构造演化[J].现代地质,1999,13(1):51-56.
[22]郭正府,邓晋福,许志琴,等.青藏东昆仑晚古生代末-中生代中酸性火成岩与陆内造山过程[J].现代地质,1998,12(3):344-352.
[23]潘桂棠,肖庆辉,陆松年,等.中国大地构造单元划分[J].中国地质,2002,36(1):1-28.
[24]青海省地质矿产局.青海省岩石地层[M].武汉:中国地质大学出版社,1997.
[25]路凤香,桑隆康,邬金华,等.岩石学[M].北京:地质出版社,2002.
[26]李怀坤,耿建珍,郝爽,等.用激光烧蚀多接收器等离子体质谱仪(LA-MC-ICPMS)测定锆石U-Pb同位素年龄的研究[J].矿物学报,2009,(增刊):600-601.
[27]邱家骧.岩浆岩岩石学[M].北京:地质出版社,1986.
[28]韩磊,张立飞.K和Na在深俯冲板块中的元素化学行为[J].岩石矿物学杂志,2015,34(5):755-766.
[29]Pearce J A.Trace element characteristics of lavas from destructive plate boundaries[C]//Thorpe R S.Andesits.Chichester:Wiley,1982:525-548.
[30]Boynton W V.Geochemistry of the rare earth elements:Meteorite studies[C]//Henderson P.Rare earth element geochemistry.Elservier,1984:63-114.
[31]李昌年.微量元素岩石学[M].武汉:中国地质大学出版社,1992.
[32]Yegodainski G M,Kay R W,Volynets O N,et al.Magnesian andesite in thewesternAleutian Komandorsky region:Implications for slabmelting and processes in themantlewedge[J].Geol.Soc.Amer.Bull.,1995,107:505-519.
[33]Sun S S,McDonough W F.Chemical and isotopic systematicsof oceanic basalts:implications for mantle composition and processes[C]//Saunders A D,Norry M J.Magmatism in the Oceanic Basins,Geological Society Special Publication,1989,42:313-346.
[34]Pearce J A,Role of the sub-continental lithosphere in magma genesis at active continental margins[C]//Hawkesworth C J,Norry M J.Continental basalts and mantle xenoliths.Nantwich:Shiva,1983:230-249.
[35]吴元保,郑永飞.锆石成因矿物研究及其对U-Pb年龄解释的制约[J].科学通报,2004,49(16):1589-1604.
[36]Nasdala L,Wenzel M,Vavra G,et al.Metamictisation of natural zircon:Accumulation versus thermal annealing of radioactivityinduced damage[J].Contributions to Mineralogy and Petrology,2001,141(2):125-144
[37]Pearce J A,Lippard S J,Roberts S.Characteristics and tectonic significance of supra-subduction zone ophiolites[J].Geological Society of London,Special Publications,1984,16(1):74-94.
[38]Dewey J F,Bird J M.Origin and emplacement of the ophiolite suite:Appalachian ophiolites in Newfoundland[J].Journal of Geophysical Research,1971,76(14):3179-3206
[39]邓晋福,肖庆辉,苏尚国,等.火成岩组合与构造环境:讨论[J].高校地质学报,2007,13(3):392-402.
[40]Pearce J A,Cann J R.Tectonic setting of basic volcanic rocks determined using trace element analyses[J].Earth and Planetary Science Letters,1973,19:290-300.(1)
(1)1∶20万不冻泉幅区域地质调查报告.青海省区调综合地质大队,1986.
(2)1∶25万不冻泉幅区域地质调查报告.中国地质大学(武汉), 2003.
(3)青海省格尔木市窑洞山地区两幅1∶5万区域地质调查报告.青海省地质调查院, 2016.
(4)青海省区域地质调查与片区总结成果报告内部资料.青海省地质调查院, 2017.
(5)1∶5万保沟幅、没草沟幅、青办食宿幅区域地质调查报告.青海省地质调查院, 2002.