新疆库地北中三叠世斑状二长花岗岩锆石U-Pb年龄、地球化学特征及其构造意义
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摘要
西昆仑山是塔里木地块和羌塘地块在晚中生代碰撞造山的产物,古特提斯洋分支库尔良-阿羌裂谷闭合时限亦存在争议。以库地北斑状二长花岗岩为研究对象,进行岩石学、地球化学和年代学研究。获得LA-ICP-MS锆石U-Pb年龄244.42±0.87Ma,时代为中三叠世。斑状二长花岗岩的SiO_2含量为65.57%～67.70%,Mg~#值为35～38,A/CNK值为0.90～1.01,属于偏铝质高钾钙碱性岩石。稀土元素总量为193×10~(-6)～339×10~(-6),δEu=0.72～0.78,具弱负Eu异常。微量元素Rb、K、Th、U、La、Ce、Zr富集,Nb、Ti、P中等-强亏损。斑状二长花岗岩属于I型花岗岩,源岩为安山岩,形成于俯冲的大陆岛弧环境。结合区域资料和前人研究成果表明,斑状二长花岗岩形成于中三叠世大陆岛弧环境,中三叠世库地一带存在古特提斯洋壳俯冲活动,库尔良-阿羌裂谷尚未消减闭合。
The West Kunlun Mountains is the product of the Tarim block and the Qiangtang plots in the Late Mesozoic collision orogeny. The closing time of the Kurdish-Aqiang rift valley is also controversial. In this paper, we studied the petrology,geochemistry and chronology of prophyritic monzonitic granite of the Kudi northern. In this paper, the LA-ICP-MS zircon U-Pb age is 244.42±0.87 Ma, and the age is Middle Triassic. The SiO_2 content of the porphyritic granite is 65.57%～67.70%, Mg~#=35～38,A/CNK=.90～1.01, belonging to the aluminum-alkali high-potassium calc-alkaline rock. The total amount of rare earth elements is 193×10~(-6)～339×10~(-6), δEu=0.72～0.78, with weak negative anomaly.Trace elements Rb, K, Th, U, La, Ce, Zr are enriched,Nb, Ti, P medium-strong loss. The porphyritic granite belongs to the I-type granite, and the source rock is the Andesite, which is formed in the subduction continental island arc environment. Regional data, previous achievements and research in this paper indicate that the porphyritic granite was formed in the continental arc environment of the Middle Triassic, and that the ancient Tethys oceanic crust subduction activity existed in the reservoir area of the Middle Triassic, Kulliag-A Rift Valley has not yet reduced closure.
The West Kunlun Mountains is the product of the Tarim block and the Qiangtang plots in the Late Mesozoic collision orogeny. The closing time of the Kurdish-Aqiang rift valley is also controversial. In this paper, we studied the petrology,geochemistry and chronology of prophyritic monzonitic granite of the Kudi northern. In this paper, the LA-ICP-MS zircon U-Pb age is 244.42±0.87 Ma, and the age is Middle Triassic. The SiO_2 content of the porphyritic granite is 65.57%～67.70%, Mg~#=35～38,A/CNK=.90～1.01, belonging to the aluminum-alkali high-potassium calc-alkaline rock. The total amount of rare earth elements is 193×10~(-6)～339×10~(-6), δEu=0.72～0.78, with weak negative anomaly.Trace elements Rb, K, Th, U, La, Ce, Zr are enriched,Nb, Ti, P medium-strong loss. The porphyritic granite belongs to the I-type granite, and the source rock is the Andesite, which is formed in the subduction continental island arc environment. Regional data, previous achievements and research in this paper indicate that the porphyritic granite was formed in the continental arc environment of the Middle Triassic, and that the ancient Tethys oceanic crust subduction activity existed in the reservoir area of the Middle Triassic, Kulliag-A Rift Valley has not yet reduced closure.
引文
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[18]迟清华,鄢明才.应用地球化学元素丰度数据手册[M].北京:地质出版社,2007.
[19]肖庆辉,王涛,邓晋福,等.中国典型造山带花岗岩与大陆地壳生长研究[M].北京:地质出版社,2009.
[20]Ringwood A E.Composition and petrology of the Earth's mantle[M].McGraw-Hill.Inc.,1975.
(1)陕西省地质调查院.麻扎幅、神仙湾幅1∶25万区域地质调查报告.2004.
(2)内蒙古第九地质矿产勘查开发院.新疆叶城县库地东一带1∶5万区域地质调查报告.2014.
[2]赵冬冬,陈汉林,杨树锋,等.西昆仑甜水海地区前陆褶皱冲断带的构造样式及其演化[J].地质学报,2000,74(2):134-141.
[3]康磊,校培喜,高晓峰,等.西昆仑康西瓦断裂西段斜长片麻岩LA-ICP-MS锆石U-Pb定年及其构造意义[J].地质通报,2012,1(8):1244-1250.
[4]刘金菊,牛耀龄,张宇,等.西昆仑三十里营房-康西瓦花岗岩体的年代学、地球化学特征研究[C]//俯冲带壳幔相互作用论文集.中国地球科学联合学术年会,2014:1746.
[5]杨文强,刘良,曹玉亭,等.西昆仑塔什库尔干印支期(高压)变质事件的确定及其构造地质意义[C]//中国科学:地球科学,2011,41(8):1047-1060.
[6]计文化,周辉,李亚民.西昆仑新藏公路118~323km段基性、酸性岩脉K-Ar年龄[J].地质通报,2005,24(3):243-245.
[7]Frost B R,Barnes C G,Collins W J,et al.A geochemical classification for granitic rocks[J].Journal of Petrylogy,2001,42(11):2033-2048.
[8]Peccerillo A,Taylor S R.Geochemistry of Eocen calc-alkaline volcanic rocks from the Kastamonu area,northern Turkey[J].CMP,1976,58:63-81.
[9]Boynton W V.Geochemistry of rate earth elements:Meteorite studies[C]//Henderson P.Rare Earth Elements Geochemistry.Amsterdam:Elsevier,1984:63-114.
[10]Sun S S,McDonough W F.Chemical and isotopic systematics of oceanic basalts:Implications for mantle composition and processes[C]//Saunders A D,Norry M J.Magmatism in Ocean Basins.Geological Society,London:Geological Society of Special Publication,1989,42(1):313-345.
[11]Altherr R,Hegner E.High-potassium,calc-alkaline I-type Plutonism in the European Variscides:Northern Vosges(France)and northern Schwarzwald(Germany)[J].Lithos,2000,50:51-73.
[12]邓晋福,罗照华,苏尚国,等.岩石成因、构造环境与成矿作用[M].北京:地质出版社,2004.
[13]Smithies R H.The Archaean tonalite-trondhjemite-granodiorite(TTG)series is not an analogue of Cenozonic adakite[J].Earth and Planetary Science Letters,2000,182(1):115-125.
[14]Rapp R P,Watson E B.Dehydration melting of metabasalt at 8-32kbar:Implications for continental growth and crust-mantle recycling[J].Journal of Petrology,1995,36(4):891-931.
[15]Hofmann A W.Chemical differntitation of the Earth:The relationship between mantle,continental crust,and oceanic crust[J].Earth and Planetary Science Letters,1988,90:297-314.
[16]Ayers J.Trace element modeling of aqueous fluid-peridotiti interaction in the mantle wedge of subduction zones[J].Contributions to Mineralogy and Petrology,1998,132(4):390-404.
[17]Ryerson F J,Watson E B.Rutile saturrtion in magma:Implications for Ti-Nb-Ta depletion in island-arc basalts[J].Earth and Planetary Science Letters,1987,86(2/4):225-239.
[18]迟清华,鄢明才.应用地球化学元素丰度数据手册[M].北京:地质出版社,2007.
[19]肖庆辉,王涛,邓晋福,等.中国典型造山带花岗岩与大陆地壳生长研究[M].北京:地质出版社,2009.
[20]Ringwood A E.Composition and petrology of the Earth's mantle[M].McGraw-Hill.Inc.,1975.
(1)陕西省地质调查院.麻扎幅、神仙湾幅1∶25万区域地质调查报告.2004.
(2)内蒙古第九地质矿产勘查开发院.新疆叶城县库地东一带1∶5万区域地质调查报告.2014.
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