内蒙古锡林浩特博仁敖包—巴彦门德过铝质岩的锆石U-Pb年代学、地球化学及其构造意义
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摘要
锡林浩特博仁敖包花岗闪长岩主要由花岗闪长岩、闪长岩等侵入岩组成。通过对该岩体开展系统的锆石LA-ICP-MSU-Pb年代学、岩石地球化学等综合研究,锆石U-Pb测年结果表明该地区过铝质侵入岩主要由形成于早二叠世花岗闪长岩(278±2Ma),晚二叠世花岗闪长岩(252±2Ma)组成。二者的岩石地球化学特征显示,均以钙碱性系列为主,具过铝质的特点。岩体富含大离子亲石元素Rb、K、Ce和高场强元素Zr、Hf、Th等,而Sr、Ba、P、Ti等元素较低,Nb呈现了亏损的正常弧造山花岗岩的特征。Sr、Ba的亏损反映花岗岩分离结晶作用的存在。早二叠世的花岗闪长岩从其总体的化学组成与典型的I型花岗岩相似,为碰撞前的花岗岩组合,与大陆弧花岗岩类组合的构造环境相同。晚二叠世的组合特征代表了碰撞后的抬升阶段的花岗岩组合。微量元素Ta-Yb、Nb-Y构造判别图解显示从早叠世的花岗闪长岩到晚二叠世的花岗闪长岩代表了锡林浩特地区从碰撞前的大陆弧环境到其间的小洋盆闭合隆升的过程。从晚二叠世开始该地区进入了造山活动的活跃期,暗示滨太平洋构造体系对内蒙古东南缘的影响可能从二叠世已经开始显现。
The Peraluminous intrusive rocks in the Borentunbao area of Xilinhot are mainly composed of invasive rocks such as the Early Permian granodiorite,diorite and Late Permian granodiorite.Through the systematic study of zircon LA-ICP-MS U-Pb geochronology and rock geochemistry of the rock mass,the zircon U-Pb dating results indicate that the Early Permian granodiorite was formed in(278 ± 2 Ma),Late Permian granodiorite(252 ± 2 Ma).The geochemical characteristics of the rocks show that they are mainly calcium-alkaline series and have the characteristics of peraluminous.The rock mass is rich in large ion lithophile elements Rb,K,Ce and high field strength elements Zr,Hf,Th,etc.,while Sr,Ba,P,Ti and other elements are lower,and Nb presents the characteristics of loss-making normal arc orogenic granite..The loss of Sr and Ba reflects the existence of separation and crystallization of granite.The Early Permian granodiorite is similar in its overall chemical composition to the typical I-type granite,and is the granite combination before the collision,which is the same as the continental arc granite combination.The combined features of the Late Permian represent granite combinations during the ascending phase of the collision.The tracing diagrams of trace elements Ta-Yb and Nb-Y show that the granodiorite from the Early Permian granodiorite to the Late Permian represents the small ocean basin in the Xilinhot area from the continental arc environment before the collision.The process of closing the uplift.Since the Late Permian,the area has entered an active period of orogenic activities,suggesting that the influence of the Pacific Ocean tectonic system on the southeastern margin of Inner Mongolia may have begun to appear from the Permian.
The Peraluminous intrusive rocks in the Borentunbao area of Xilinhot are mainly composed of invasive rocks such as the Early Permian granodiorite,diorite and Late Permian granodiorite.Through the systematic study of zircon LA-ICP-MS U-Pb geochronology and rock geochemistry of the rock mass,the zircon U-Pb dating results indicate that the Early Permian granodiorite was formed in(278 ± 2 Ma),Late Permian granodiorite(252 ± 2 Ma).The geochemical characteristics of the rocks show that they are mainly calcium-alkaline series and have the characteristics of peraluminous.The rock mass is rich in large ion lithophile elements Rb,K,Ce and high field strength elements Zr,Hf,Th,etc.,while Sr,Ba,P,Ti and other elements are lower,and Nb presents the characteristics of loss-making normal arc orogenic granite..The loss of Sr and Ba reflects the existence of separation and crystallization of granite.The Early Permian granodiorite is similar in its overall chemical composition to the typical I-type granite,and is the granite combination before the collision,which is the same as the continental arc granite combination.The combined features of the Late Permian represent granite combinations during the ascending phase of the collision.The tracing diagrams of trace elements Ta-Yb and Nb-Y show that the granodiorite from the Early Permian granodiorite to the Late Permian represents the small ocean basin in the Xilinhot area from the continental arc environment before the collision.The process of closing the uplift.Since the Late Permian,the area has entered an active period of orogenic activities,suggesting that the influence of the Pacific Ocean tectonic system on the southeastern margin of Inner Mongolia may have begun to appear from the Permian.
引文
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陶继雄,白立兵,宝音乌力吉,等.内蒙古满都拉地区二叠纪俯冲造山过程的岩石记录[J].地质调查与研究.2003(04):241-249.
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郑龙,薛怀宇,郭娜,等.内蒙古锡林浩特白音锡勒牧场地区含天河石花岗岩岩石地球化学特征[J].地质论评.2017(S1):195-196.
袁建国,顾玉超,肖荣阁,等.内蒙古锡林浩特东部地区早白垩世花岗岩地球化学、锆石U-Pb年龄及地质意义[J].现代地质.2017(01):20-32.
袁建国,任永健,姜振宁,等.内蒙古锡林浩特毛登牧场早石炭世花岗岩锆石U-Pb年龄、地球化学特征及其地质意义[J].现代地质.2017(06):1131-1146.
范中林,柯于富,陈文,等.内蒙古锡林浩特Ⅰ型花岗岩的时代及构造意义[J].资源调查与环境.2012(03):191-197.
Boynton W V.Cosmochemistry of the rare earth elements:meteorite studies[M].Developments in geochemistry.Elsevier,1984,2:63-114.
Chen B,Jahn B M,Wilde S,et al.Two contrasting paleozoic magmatic belts in northern Inner Mongolia,China:petrogenesis and tectonic implications[J].TECTONOPHYSICS.2000,328(1-2):157-182.
Ludwig,K.R.,Ed.(2003).ISOPLOT 3.00:A Geochronological Toolkit for Microsoft Excel.Berkeley,Berkeley Geochronology Center,California.
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
Poli G,Frey F A,Ferrara G.Geochemical characteristics of the South Tuscany(Italy)volcanic province:constraints on lava petrogenesis[J].Chemical Geology,1984,43(3-4):203-221
Sengor A,Natalin B A,Burtman V S.EVOLUTION OF THE ALTAIDTECTONIC COLLAGE AND PALEOZOIC CRUSTAL GROWTH INEURASIA[J].NATURE.1993,364(6435):299-307.
Sun S S,Mc Donough W F.Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J].Geological Society,London,Special Publications,1989,42(1):313-345.
Zhao X,Zhou W,Fu D,et al.Isotope Chronology and Geochemistry of the Lower Carboniferous Granite in Xilinhot,Inner Mongolia,China[J].Journal of Earth Science,2018,29(2):280-294.
Zhou W,Li S,Ge M,et al.Geochemistry and zircon geochronology of a gabbro-granodiorite complex in Tongxunlian,Inner Mongolia:partial melting of enriched lithosphere mantle[J].Geological Journal,2016,51(1):21-41.
徐备,陈斌.内蒙古北部华北板块与西伯利亚板块之间中古生代造山带的结构及演化[J].中国科学(D辑:地球科学).1997(03):227-232.
施光海,苗来成,张福勤,等.内蒙古锡林浩特A型花岗岩的时代及区域构造意义[J].科学通报.2004(04):384-389.
陈斌,赵国春,Simonwilde.内蒙古苏尼特左旗南两类花岗岩同位素年代学及其构造意义[J].地质论评.2001(04):361-367.
段明,曾威,冯晓曦,等.内蒙古锡林浩特地区道伦达坝矿区花岗岩LA-ICP-MS锆石U-Pb年龄及其地质意义[J].地质通报.2016(07):1207-1216.
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,2009,29(S1):600-601.
陶继雄,白立兵,宝音乌力吉,等.内蒙古满都拉地区二叠纪俯冲造山过程的岩石记录[J].地质调查与研究.2003(04):241-249.
王荃.中国华夏与安加拉古陆间的板块构造[M].北京大学出版社,1991.
叶栩松,廖群安,葛梦春.内蒙古锡林浩特、林西地区三叠纪过铝质花岗岩的成因及构造意义[J].地质科技情报.2011(03):57-64.
郑龙,薛怀宇,郭娜,等.内蒙古锡林浩特白音锡勒牧场地区含天河石花岗岩岩石地球化学特征[J].地质论评.2017(S1):195-196.
袁建国,顾玉超,肖荣阁,等.内蒙古锡林浩特东部地区早白垩世花岗岩地球化学、锆石U-Pb年龄及地质意义[J].现代地质.2017(01):20-32.
袁建国,任永健,姜振宁,等.内蒙古锡林浩特毛登牧场早石炭世花岗岩锆石U-Pb年龄、地球化学特征及其地质意义[J].现代地质.2017(06):1131-1146.
范中林,柯于富,陈文,等.内蒙古锡林浩特Ⅰ型花岗岩的时代及构造意义[J].资源调查与环境.2012(03):191-197.