阿尔金南缘江尕勒萨依二长花岗岩年龄测定毕业设计论文Word下载.docx

阿尔金南缘江尕勒萨依二长花岗岩年龄测定毕业设计论文Word下载.docx

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反映该花岗岩的源岩主要来自于壳源物质的重熔，其来源也相对单一。

江尕勒萨依二长花岗岩稀土总量为中等（∑REE=180.89ppm~260.17ppm）,具有高度富集轻稀土而亏损重稀土的特征,轻重稀土比值高（LR/HR=9.01~22.14,平均为20.59）,（La/Yb）N=14.18~89.35,平均为74.68,样品均出现明显的负Eu异常（δEu=0.16~0.36,平均为0.25）｡从微量元素对原始地幔标准化蛛网图上可以看出,所有花岗岩样品富集K､Rb､Th和U等大离子亲石元素（LILEs）与轻稀土元素（La､Ce､Nd等）,亏损Nb､Ta､P和Ti等高场强元素（HFSEs）,具有明显的Sr与Ba负异常,Zr､Hf无明显分异,Sr､Ba亏损与负的Eu异常,共同表明部分熔融源区残留体中存在斜长石或在岩浆演化过程中斜长石发生分离结晶｡该地区花岗岩样品中的锆石自形程度为自形晶,呈长柱状｡从CL图像可以看出,锆石显示清晰的岩浆振荡环带。

锆石CL图像特征表明所有样品中的锆石主体为岩浆成因,可以代表花岗岩的形成时代。

利用LA-ICP-MS方法对该区花岗质岩石进行了锆石U-Pb定年分析。

大部分测点位于谐和线上及附近,江尕勒萨依二长花岗岩的206Pb/238U年龄介于449Ma~458Ma,加权平均值为453.1±

2.1Ma,锆石U-Pb定年结果表明江尕勒萨依地区花岗岩的形成年龄与超高压岩石的退变质年龄一致，都是折返背景下由地壳物质重熔形成的。

关键字:

阿尔金；

二长花岗岩；

LA-ICP-MS锆石定年；

Hf同位素特征；

碰撞后抬升

Abstract

AltunmountainislocatedinthenorthernmarginoftheQinghaiTibetPlateau,theeastQilianMountains,KunlunMountainsinthewest,islocatedbetweentheTarimplateandtheQaidammicroplate,occupiesaprominentimportanttectonicposition,theorogenicprocesstimelimittoexplorecontrastoftheadjacentgeologicalunitoftheconnectionandtheWesterntectonicevolutionhasimportantgeologicalsignificance.Inthispaper,theresearchonthesouthernAltynjanggalsayRivergranitefieldgeology,petrology,geochemistryandgeochronologytodeterminethespatialdistributioncharacteristicsofthestudyareatheearlyPaleozoicgranitoids,magmatismandpetrogenesis,combinedwithregionalhigh-pressureandultrahighpressuremetamorphismandresearchresults,toexploretheSouthAltunsouthmarginofjanggalsayRivergraniterocksofdiageneticdynamicbackground.DiscoveredbytheAltynjanggalsayRivergraniterockisstudied,themainmineralcompositionofpotassiumfeldspar,plagioclase,quartzandbiotite. 

Whichpotassiumfeldsparareeuhedraltosubhedralcrystal,mainlyofperthiteandmicroclinecontentis30%~40%,thecontentofplagioclasebetween20%~30%,quartzcontentisabout30%,biotitecontentofabout15%,accessorymineralsmainlyzircon,titanite,apatiteandmagnetite,HighcontentofSiO2（7.337%~74.02%,withanaverageof73.69%）,TiO2content（0.11%~0.16%,withanaverageof0.13%）low,theCaOcontent（0.85%~0.94%,withanaverageof0.91%）low,Na2Ocontentwas3.04%~3.65%,withanaverageof3.32%,K2Ocontentwas5.22%~5.69%,withanaverageof5.43%,hightotalalkalicontent（K2O+Na2O=8.42~9.01,average8.76）,arelativelyhighNa2OK2Ocontent,K2O/Na2O=1.46~177,withanaverageof1.63.InSiO2-K2O+Na2Odiagramallsamplesfallintothegranitearea.InSiO2-K2Odiagramintohigh-kcalcalkalinepotassiumshoshoniteseries,inK2O-Na2Omapintohighpotassiczonehascharacteristicsofrichaluminum,Al2O3contentfor13.78%~13.98%,withanaverageof13.9%,aluminumcladandindexA/CNK=1.03~1.11inthe,withanaverageof1.06,aluminousrocks. 

Janggalsayriveristhesecondlongestzircon176Hf/177Hfvariesintherangeof0.282412~0.282456,withameanvalueof0.282440,epsilonHf（T）variedfrom3.1~1.5,andthemeanvalueis2.1,thetwostagemodelagesfor1391Ma~1478Ma,averagefor1425Ma.Reflectthe 

sourcerocksofthe 

granite 

ismainlyfrom 

crustsource 

material 

remelting, 

itssource 

isrelatively 

single. 

Medium（REE=180.89ppmjanggalsayRivermonzoniticgraniteREE~260.17partspermillion（PPM）ofishighlyenrichedinlightrareearthandlosscharacteristicsofheavyrareearth,highratiobetweenLREEandhree（LR/HR=9.01~22.14,withanaverageof20.59）,（LA/Yb）n=14.18~89.35averagefor74.68,sampleswerefoundsignificantnegativeEuanomalies（8eu=0.16~0.36,averagefor0.25）.uhedralplagioclaseresiduallossfromtraceelementsofprimitivemantlenormalizedspiderdiagramcanbeseen,allgranitesamplesareenrichedinK,Rb,ThandUandotherlargeionlithophileelements（LILEs）andlightrareearthelements（La,Ce,Nd）anddepletedinNb,Ta,PandTiandhighfieldstrengthelements（HFSEs）,withobviousSrandBanegativeanomalies,Zr,Hfwithoutobviousdifferentiation,Sr,BaandnegativeEuanomaliesshowthatthepartialmeltingofthesourceregionofthebodyinthepresenceofplagioclaseorinthemagmaevolutionintheprocessoffractionalcrystallization.Theareaofgranitesamplesofzircondegreeaseuhedralcrystal,alongcolumnshape,lengthof100~150mum,lengthandwidthratiois2:

1~3:

1.Ascanbeseen 

fromtheCL 

images, 

showing 

clear 

zircon 

magmaticoscillatoryzoning. 

Alargenumber