东准噶尔卡拉麦里姜巴斯套组闪长岩脉LA-ICP-MS锆石U-Pb测年及地质意义
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摘要
姜巴斯套组主要分布在卡拉麦里断裂带内,沿卡拉麦里大断裂,呈北西—南东向条带展布,地层内出露闪长岩脉体。对闪长岩脉进行岩石地球化学,LA-ICP-MS锆石U-Pb测年综合研究,研究结果显示:姜巴斯套组中的闪长岩脉表现为高碱,富钾,富集轻稀土元素(LREE)和大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE)。锆石测年显示闪长岩脉的206Pb/238 U年龄加权平均值为303.7±1.5Ma,(NSWD=0.94)。为晚石炭世早期岩浆活动的产物。闪长岩脉体形成条件可能与板块的俯冲消减有关。闪长质岩浆可能形成于俯冲板片流体和俯冲的沉积物交代地幔楔高程度部分熔融。
The Jiangbasitao formation is mainly distributed along Kalamaili fault,a NW-SE strip distribution and the diorite dykes are exposed in the strata.The diorite dyke rock geochemistry,LA-ICP-MS zircon U-Pb dating study shows that the diorite dyke in Jiangbasitao formation are characterized by high alkali,potassium enrichment,enrichment of Light rare earth elements(LREE)and large ion lithophile elements(LILE),loss of high field strength elements(HFSE),such as Nb,Ta,and Ti.The Zircon dating shows that the 206 Pb/238 U age weighted average value of the diorite dikes is 303.7±1.5 Ma(NSWD=0.94).It is the product of the early magmatic activity of late Carboniferous.The diorite magmas may have been formed in the subducted plate fluids and subducted sediments,partially melted by the high degree.
The Jiangbasitao formation is mainly distributed along Kalamaili fault,a NW-SE strip distribution and the diorite dykes are exposed in the strata.The diorite dyke rock geochemistry,LA-ICP-MS zircon U-Pb dating study shows that the diorite dyke in Jiangbasitao formation are characterized by high alkali,potassium enrichment,enrichment of Light rare earth elements(LREE)and large ion lithophile elements(LILE),loss of high field strength elements(HFSE),such as Nb,Ta,and Ti.The Zircon dating shows that the 206 Pb/238 U age weighted average value of the diorite dikes is 303.7±1.5 Ma(NSWD=0.94).It is the product of the early magmatic activity of late Carboniferous.The diorite magmas may have been formed in the subducted plate fluids and subducted sediments,partially melted by the high degree.
引文
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[4]李锦轶,杨天南,李亚萍,等.东准噶尔卡拉麦里断裂带的地质特征及其对中亚、地区晚古生代洋陆格局重建的约束[J].地质通报,2009,28(12):1817-1826.LI Jinyi,YANG Tiannan,LI Yaping,et al.Geological features of the Karamaili faulting belt,eastern Junggar region,Xinjiang,China and its constraints on the reconstruction of Late Paleozoic ocean-continental framework of the Central Asian region[J].Geological Bulletin of China,2009,28(12):1817-1826.
[5]SCARROW J H,LEAT P T,WARCHAM C D,et al.Geochemistry of Mafic Dykes in the Antarctic Peninsula Continental-Margin Batholith;A Record of Arc Evolution[J].Comirzbutzoms to Mierulogy umd Petrology,1998,131:289-305.
[6]FOWLER M B,HENNEY P J.Mixed caledonian appinite Magmas;implications for lamprophyre fraction and high Ba-Sr granite genesis[J].Cootrilbutions to Mineralogy and Petrology,1996,126:99-215.
[7]HOLE M J,SAUNDERS A D,MARRINER G F,et al.Subduction of pelagio sediments:implications for the origin of Ce-anomalous basalts from the Manana islands[J].Journal of the Geological Speciety,London,1984,141(3):453-472.
[8]PLANK T,LANGMUIR C H.The chemical composition of subducting sediment and its consequences for the crust and mantle[J].Chemical Geology,1998,145:325-394.
[9]SEGHEDI I,DOWNES H,VASELLI O,et al.Postcollisional Tertiary-Quaternary mafic alkalic magmatism in the Carpathian-Pannonian region:a review[J].Tectonophysics,2004,393:43-62.
[10]SUN S S,MCDONOUGH W F.Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[C]//Geological Society Special Publication,1989,42:313-345.
[11]ROGERS N W.Potassic magmatism as a key to trace element enrichment processes in the upper mantle[J].J.Volcan.Geother.Research on Chemical.1992,50:85-99.
[12]龙晓平,孙敏,袁超,等.东准噶尔石炭系火山岩的形成机制及其对准噶尔洋盆闭合时限的制约[J].岩石学报,2006,22(1):31-40.LONG Xiaoping,SUN Min,YUAN Chao,et al.Genesis of carboniferous volcanic rocks in the eastern Junggar:constrants on the closure of the Junggar ocean[J].Acta Petrologica Sinica,2006,22(l):31-40.