测点相对位置对离子探针锆石U-Pb定年的影响
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摘要
离子探针得益于高空间分辨率的特点,在复杂变质锆石的微区原位年代学研究中,其常被作为首选技术手段。对具有复杂环带结构的锆石进行原位分析,通常可以得到岩石多期次地质演化信息,因此在一颗有核(幔)边结构的锆石上进行多点分析是常见现象。为了定量地评估多点分析时测点的相对位置对离子探针测量结果的影响,本研究采用目前报道最为均一的锆石标样M257为测试对象,分为四种情况,即同一测点重复测试年龄、同一测点先氧同位素分析后年龄测试、在首个测点的上/下/左/右方且预剥蚀区域有部分重叠的范围内测试、距首个测点有显著距离测试等,进行了系统性U-Pb定年对比实验。结果显示,相对一个颗粒上的首个测点,第二个测点的测试深度和预剥蚀区域的变化会给测试结果带来-5%到+11%的系统偏差,尤以与首个测点的预剥蚀区域有重叠且位于一次离子入射方向后侧的分析点会产生最为显著的系统偏差。因此,在采用离子探针进行副矿物U-Pb测试的时候,当需要原位重复分析或在临近区域多点分析时,需要特别注意多个测点的相对位置和分析顺序。本实验结果指示,以往通过离子探针方法对变质锆石进行过核边多点分析,通过变质锆石边部所获得的年龄结果值得重新审视,有将变质时代持续时间扩大化的隐忧。
The Secondary Ion Mass Spectrometry(SIMS)is normally considered as the first choice to reveal the age of complicate metamorphic zircon due to its high spatial resolution.It is very common to test the rim and the core of a metamorphic zircon grain at the same analytical session to investigate the metamorphic and protolith age,respectively.In order to evaluate the effect of relative measured position on SIMS U-Pb dating quantitatively,the most homogenous zircon reference material M257 was tested under four different situations:1)testing U-Pb age of the zircon twice on the same spot,2)analyzing O isotopes firstly and U-Pb dating secondly in the same pit,3)bombing the up/down/left/right region relative to the first measured position with overlapped pre-sputter area successively,4)detecting two spots on the same zircon grain with visible distance.The results showed that the depths of the bombardment and the pre-sputter area relative to the first measurement can cause obvious U-Pb data bias ranging from-5%to 11%.The maximum bias is recorded in the rear region relative to the direction of primary ion of the first measured spot with overlapped presputter area the rear.Cautions are suggested when setting the relative measured position on the same area.In addition,previous SIMS dating results on metamorphic zircon rims after measuring the zircon core should be re-evaluated.The time span of metamorphism could be extended without evaluation of the relative measured position effect.
The Secondary Ion Mass Spectrometry(SIMS)is normally considered as the first choice to reveal the age of complicate metamorphic zircon due to its high spatial resolution.It is very common to test the rim and the core of a metamorphic zircon grain at the same analytical session to investigate the metamorphic and protolith age,respectively.In order to evaluate the effect of relative measured position on SIMS U-Pb dating quantitatively,the most homogenous zircon reference material M257 was tested under four different situations:1)testing U-Pb age of the zircon twice on the same spot,2)analyzing O isotopes firstly and U-Pb dating secondly in the same pit,3)bombing the up/down/left/right region relative to the first measured position with overlapped pre-sputter area successively,4)detecting two spots on the same zircon grain with visible distance.The results showed that the depths of the bombardment and the pre-sputter area relative to the first measurement can cause obvious U-Pb data bias ranging from-5%to 11%.The maximum bias is recorded in the rear region relative to the direction of primary ion of the first measured spot with overlapped presputter area the rear.Cautions are suggested when setting the relative measured position on the same area.In addition,previous SIMS dating results on metamorphic zircon rims after measuring the zircon core should be re-evaluated.The time span of metamorphism could be extended without evaluation of the relative measured position effect.
引文
Andersen CA and Hinthorne JR.1973.Thermodynamic approach to the quantitative interpretation of sputtered ion mass spectra.Analytical Chemistry,45(8):1421-1438
Chaussidon M,Deng ZB,Villeneuve J,Moureau J,Watson B,Richter Fand Moynier F.2017.In situ analysis of non-traditional isotopes by SIMS and LA-MC-ICP-MS:Key aspects and the example of Mg isotopes in olivines and silicate glasses.Reviews in Mineralogy and Geochemistry,82(1):127-163
Chen DG,Li BX,Xia QK,Wu YB and Cheng H.2001.An evaluation of zircon U-Pb dating for metamorphic rocks and comments on zircon ages of Dabie orogen.Acta Petrologica Sinica,17(1):129-138(in Chinese with English abstract)
Compston W,Williams IS and Meyer C.1984.U-Pb geochronology of zircons from lunar breccia 73217 using a sensitive high massresolution ion microprobe.Journal of Geophysical Research,89(S02):B525-B534
Gao YY,Li XH,Griffin WL,Tang YJ,Pearson NJ,Liu Y,Chu MF,Li QL,Tang GQ and O’Reilly SY.2015.Extreme lithium isotopic fractionation in three zircon standards(Ple2ovice,Qinghu and Temora).Scientific Reports,5:16878,doi:10.1038/srep16878
Hinthorne JR,Andersen CA,Conrad RL and Lovering JF.1979.Singlegrain207Pb206Pb and U/Pb age determinations with a 10-(m spatial resolution using the ion microprobe mass analyzer(IMMA).Chemical Geology,25(4):271-303
Kita NT,Ushikubo T,Fu B and Valley JW.2009.High precision SIMSoxygen isotope analysis and the effect of sample topography.Chemical Geology,264(1-4):43-57
Li QL,Li XH,Liu Y,Tang GQ,Yang JH and Zhu WG.2010a.Precise U-Pb and Pb-Pb dating of Phanerozoic baddeleyite by SIMS with oxygen flooding technique.Journal of Analytical Atomic Spectrometry,25(7):1107-1113
Li QL,Li XH,Liu Y,Wu FY,Yang JH and Mitchell RH.2010b.Precise U-Pb and Th-Pb age determination of kimberlitic perovskites by secondary ion mass spectrometry.Chemical Geology,269(3-4):396-405
Li QL,Lin W,Su W,Li XH,Shi YH,Liu Y and Tang GQ.2011a.SIMS U-Pb rutile age of low-temperature eclogites from southwestern Chinese Tianshan,NW China.Lithos,122(1-2):76-86
Li QL,Li XH,Wu FY,Yin QZ,Ye HM,Liu Y,Tang GQ and Zhang CL.2012.In-situ SIMS U-Pb dating of Phanerozoic apatite with low U and high common Pb.Gondwana Research,21(4):745-756
Li QL,Yang W,Liu Y,Tang GQ,Hao JL,Zhang JC,Hu S,Zhao XC,Chen YL,Chu XL,Wang Y,Jiang Y,Zhang AC,Xu WB,Lin YTand Li XH.2013.Ion microprobe microanalytical techniques and their applications in earth sciences.Bulletin of Mineralogy,Petrology and Geochemistry,32(3):310-327(in Chinese with English abstract)
Li QL,Li XH,Lan ZW,Guo CL,Yang YN,Liu Y and Tang GQ.2013.Monazite and xenotime U-Th-Pb geochronology by ion microprobe:Dating highly fractionated granites at Xihuashan tungsten mine,SE China.Contributions to Mineralogy and Petrology,166(1):65-80
Li QL.2015.Characteristics and analytical methods of the U-Pb dating system.Bulletin of Mineralogy,Petrology and Geochemistry,34(3):491-500(in Chinese with English abstract)
Li XH,Liu Y,Li QL,Guo CH and Chamberlain KR.2009.Precise determination of Phanerozoic zircon Pb/Pb age by multicollector SIMS without external standardization.Geochemistry,Geophysics,Geosystems,10(4):Q04010,doi:10.1029/2009GC002400
Li XH,Li QL,Liu Y and Tang GQ.2011b.Further characterization of M257 zircon standard:A working reference for SIMS analysis of Li isotopes.Journal of Analytical Atomic Spectrometry,26(2):352-358
Li XH,Tang GQ,Gong B,Yang YH,Hou KJ,Hu ZC,Li QL,Liu Yand Li WX.2013.Qinghu zircon:A working reference for microbeam analysis of U-Pb age and Hf and O isotopes.Chinese Science Bulletin,58(36):4647-4654
Ling XX,Schmdicke E,Li QL,Gose J,Wu RH,Wang SQ,Liu Y,Tang GQ and Li XH.2015.Age determination of nephrite by in-situ SIMS U-Pb dating syngenetic titanite:A case study of the nephrite deposit from Luanchuan,Henan,China.Lithos,220-223:289-299
Ling XX,Li QL,Liu Y,Yang YH,Liu Y,Tang GQ and Li XH.2016.In situ SIMS Th-Pb dating of bastnaesite:Constraint on the mineralization time of the Himalayan Mianning-Dechang rare earth element deposits.Journal of Analytical Atomic Spectrometry,31(8):1680-1687
Liu XC,Li XH,Liu Y,Yang L,Li QL,Wu FY,Yu HM and Huang F.2018.Insights into the origin of purely sediment-derived Himalayan leucogranites:Si-O isotopic constraints.Science Bulletin,63(19):1243-1245,doi:10.1016/j.scib.2018.09.001
Liu Y,Li XH,Li QL,Tang GQ and Yin QZ.2011.Precise U-Pb zircon dating at a scale of<5 micron by the CAMECA 1280 SIMS using a Gaussian illumination probe.Journal of Analytical Atomic Spectrometry,26(4):845-851
Liu Y,Li XH,Tang GQ,Li QL,Liu XC,Yu HM and Huang F.2019.Ultra-high precision silicon isotope micro-analysis using a Cameca IMS-1280 SIMS instrument by eliminating the topography effect.Journal of Analytical Atomic Spectrometry,34(5):906-914,doi:10.1039/C8JA00431E
Ludwig KR.2001.Users Manual for Isoplot/Ex Rev.2.49.Berkeley:Berkeley Geochronology Center Special Publication,1-55
Misawa K,Yamaguchi A and Kaiden H.2005.U-Pb and207Pb-206Pb ages of zircons from basaltic eucrites:Implications for early basaltic volcanism on the eucrite parent body.Geochimica et Cosmochimica Acta,69(24):5847-5861
Nasdala L,Hofmeister W,Norberg N,Martinson JM,Corfu F,D9rr W,Kamo SL,Kennedy AK,Kronz A,Reiners PW,Frei D,Kosler J,Wan YS,G9tze J,Hger T,Kr9ner A and Valley JW.2008.Zircon M257:A homogeneous natural reference material for the ion microprobe U-Pb analysis of zircon.Geostandards and Geoanalytical Research,32(3):247-265
Schmitt AK and Vazquez JA.2017.Secondary ionization mass spectrometry analysis in petrochronology.Reviews in Mineralogy and Geochemistry,83(1):199-230
Schroeer JM,Rhodin TN and Bradley RC.1973.A quantum-mechanical model for the ionization and excitation of atoms during sputtering.Surface Science,34(3):571-580
Stacey JS and Kramers JD.1975.Approximation of terrestrial lead isotope evolution by a two-stage model.Earth and Planetary Science Letters,26(2):207-221
Stern RA,Bodorkos S,Kamo SL,Hickman AH and Corfu F.2009.Measurement of SIMS instrumental mass fractionation of Pb isotopes during zircon dating.Geostandards and Geoanalytical Research,33(2):145-168
Tang GQ,Li XH,Li QL,Liu Y,Ling XX and Yin QZ.2015.Deciphering the physical mechanism of the topography effect for oxygen isotope measurements using a Cameca IMS-1280 SIMS.Journal of Analytical Atomic Spectrometry,30(4):950-956
Wu FY,Li XH,Yang JH and Zheng YF.2007.Discussions on the petrogenesis of granites.Acta Petrologica Sinica,23(6):1217-1238(in Chinese with English abstract)
Wu YB and Zheng YF.2004.Genesis of zircon and its constraints on interpretation of U-Pb age.Chinese Science Bulletin,49(15):1554-1569
Yang YN,Li QL,Liu Y,Tang GQ,Ling XX and Li XH.2014.Zircon U-Pb dating by secondary ion mass spectrometry.Earth Science Frontiers,21(2):81-92(in Chinese with English abstract)
Zhou Q,Yin QZ,Young ED,Li XH,Wu FY,Li QL,Liu Y and Tang GQ.2013.SIMS Pb-Pb and U-Pb age determination of eucrite zircons at<5μm scale and the first 50Ma of the thermal history of Vesta.Geochimica et Cosmochimica Acta,110:152-175
陈道公,李彬贤,夏群科,吴元保,程昊.2001.变质岩中锆石U-Pb计时问题评述---兼论大别造山带锆石定年.岩石学报,17(1):129-138
李秋立,杨蔚,刘宇,唐国强,郝佳龙,张建超,胡森,赵旭晁,陈雅丽,储雪蕾,王英,蒋云,张爱铖,徐伟彪,林杨挺,李献华.2013.离子探针微区分析技术及其在地球科学中的应用进展.矿物岩石地球化学通报,32(3):310-327
李献华,唐国强,龚冰,杨岳衡,侯可军,胡兆初,李秋立,刘宇,李武显.2013.Qinghu(清湖)锆石:一个新的U-Pb年龄和O,Hf同位素微区分析工作标样.科学通报,58(20):1954-1961
吴福元,李献华,杨进辉,郑永飞.2007.花岗岩成因研究的若干问题.岩石学报,23(6):1217-1238
吴元保,郑永飞.2004.锆石成因矿物学研究及其对U-Pb年龄解释的制约.科学通报,49(16):1589-1604
杨亚楠,李秋立,刘宇,唐国强,凌潇潇,李献华.2014.离子探针锆石U-Pb定年.地学前缘,21(2):81-92
Chaussidon M,Deng ZB,Villeneuve J,Moureau J,Watson B,Richter Fand Moynier F.2017.In situ analysis of non-traditional isotopes by SIMS and LA-MC-ICP-MS:Key aspects and the example of Mg isotopes in olivines and silicate glasses.Reviews in Mineralogy and Geochemistry,82(1):127-163
Chen DG,Li BX,Xia QK,Wu YB and Cheng H.2001.An evaluation of zircon U-Pb dating for metamorphic rocks and comments on zircon ages of Dabie orogen.Acta Petrologica Sinica,17(1):129-138(in Chinese with English abstract)
Compston W,Williams IS and Meyer C.1984.U-Pb geochronology of zircons from lunar breccia 73217 using a sensitive high massresolution ion microprobe.Journal of Geophysical Research,89(S02):B525-B534
Gao YY,Li XH,Griffin WL,Tang YJ,Pearson NJ,Liu Y,Chu MF,Li QL,Tang GQ and O’Reilly SY.2015.Extreme lithium isotopic fractionation in three zircon standards(Ple2ovice,Qinghu and Temora).Scientific Reports,5:16878,doi:10.1038/srep16878
Hinthorne JR,Andersen CA,Conrad RL and Lovering JF.1979.Singlegrain207Pb206Pb and U/Pb age determinations with a 10-(m spatial resolution using the ion microprobe mass analyzer(IMMA).Chemical Geology,25(4):271-303
Kita NT,Ushikubo T,Fu B and Valley JW.2009.High precision SIMSoxygen isotope analysis and the effect of sample topography.Chemical Geology,264(1-4):43-57
Li QL,Li XH,Liu Y,Tang GQ,Yang JH and Zhu WG.2010a.Precise U-Pb and Pb-Pb dating of Phanerozoic baddeleyite by SIMS with oxygen flooding technique.Journal of Analytical Atomic Spectrometry,25(7):1107-1113
Li QL,Li XH,Liu Y,Wu FY,Yang JH and Mitchell RH.2010b.Precise U-Pb and Th-Pb age determination of kimberlitic perovskites by secondary ion mass spectrometry.Chemical Geology,269(3-4):396-405
Li QL,Lin W,Su W,Li XH,Shi YH,Liu Y and Tang GQ.2011a.SIMS U-Pb rutile age of low-temperature eclogites from southwestern Chinese Tianshan,NW China.Lithos,122(1-2):76-86
Li QL,Li XH,Wu FY,Yin QZ,Ye HM,Liu Y,Tang GQ and Zhang CL.2012.In-situ SIMS U-Pb dating of Phanerozoic apatite with low U and high common Pb.Gondwana Research,21(4):745-756
Li QL,Yang W,Liu Y,Tang GQ,Hao JL,Zhang JC,Hu S,Zhao XC,Chen YL,Chu XL,Wang Y,Jiang Y,Zhang AC,Xu WB,Lin YTand Li XH.2013.Ion microprobe microanalytical techniques and their applications in earth sciences.Bulletin of Mineralogy,Petrology and Geochemistry,32(3):310-327(in Chinese with English abstract)
Li QL,Li XH,Lan ZW,Guo CL,Yang YN,Liu Y and Tang GQ.2013.Monazite and xenotime U-Th-Pb geochronology by ion microprobe:Dating highly fractionated granites at Xihuashan tungsten mine,SE China.Contributions to Mineralogy and Petrology,166(1):65-80
Li QL.2015.Characteristics and analytical methods of the U-Pb dating system.Bulletin of Mineralogy,Petrology and Geochemistry,34(3):491-500(in Chinese with English abstract)
Li XH,Liu Y,Li QL,Guo CH and Chamberlain KR.2009.Precise determination of Phanerozoic zircon Pb/Pb age by multicollector SIMS without external standardization.Geochemistry,Geophysics,Geosystems,10(4):Q04010,doi:10.1029/2009GC002400
Li XH,Li QL,Liu Y and Tang GQ.2011b.Further characterization of M257 zircon standard:A working reference for SIMS analysis of Li isotopes.Journal of Analytical Atomic Spectrometry,26(2):352-358
Li XH,Tang GQ,Gong B,Yang YH,Hou KJ,Hu ZC,Li QL,Liu Yand Li WX.2013.Qinghu zircon:A working reference for microbeam analysis of U-Pb age and Hf and O isotopes.Chinese Science Bulletin,58(36):4647-4654
Ling XX,Schmdicke E,Li QL,Gose J,Wu RH,Wang SQ,Liu Y,Tang GQ and Li XH.2015.Age determination of nephrite by in-situ SIMS U-Pb dating syngenetic titanite:A case study of the nephrite deposit from Luanchuan,Henan,China.Lithos,220-223:289-299
Ling XX,Li QL,Liu Y,Yang YH,Liu Y,Tang GQ and Li XH.2016.In situ SIMS Th-Pb dating of bastnaesite:Constraint on the mineralization time of the Himalayan Mianning-Dechang rare earth element deposits.Journal of Analytical Atomic Spectrometry,31(8):1680-1687
Liu XC,Li XH,Liu Y,Yang L,Li QL,Wu FY,Yu HM and Huang F.2018.Insights into the origin of purely sediment-derived Himalayan leucogranites:Si-O isotopic constraints.Science Bulletin,63(19):1243-1245,doi:10.1016/j.scib.2018.09.001
Liu Y,Li XH,Li QL,Tang GQ and Yin QZ.2011.Precise U-Pb zircon dating at a scale of<5 micron by the CAMECA 1280 SIMS using a Gaussian illumination probe.Journal of Analytical Atomic Spectrometry,26(4):845-851
Liu Y,Li XH,Tang GQ,Li QL,Liu XC,Yu HM and Huang F.2019.Ultra-high precision silicon isotope micro-analysis using a Cameca IMS-1280 SIMS instrument by eliminating the topography effect.Journal of Analytical Atomic Spectrometry,34(5):906-914,doi:10.1039/C8JA00431E
Ludwig KR.2001.Users Manual for Isoplot/Ex Rev.2.49.Berkeley:Berkeley Geochronology Center Special Publication,1-55
Misawa K,Yamaguchi A and Kaiden H.2005.U-Pb and207Pb-206Pb ages of zircons from basaltic eucrites:Implications for early basaltic volcanism on the eucrite parent body.Geochimica et Cosmochimica Acta,69(24):5847-5861
Nasdala L,Hofmeister W,Norberg N,Martinson JM,Corfu F,D9rr W,Kamo SL,Kennedy AK,Kronz A,Reiners PW,Frei D,Kosler J,Wan YS,G9tze J,Hger T,Kr9ner A and Valley JW.2008.Zircon M257:A homogeneous natural reference material for the ion microprobe U-Pb analysis of zircon.Geostandards and Geoanalytical Research,32(3):247-265
Schmitt AK and Vazquez JA.2017.Secondary ionization mass spectrometry analysis in petrochronology.Reviews in Mineralogy and Geochemistry,83(1):199-230
Schroeer JM,Rhodin TN and Bradley RC.1973.A quantum-mechanical model for the ionization and excitation of atoms during sputtering.Surface Science,34(3):571-580
Stacey JS and Kramers JD.1975.Approximation of terrestrial lead isotope evolution by a two-stage model.Earth and Planetary Science Letters,26(2):207-221
Stern RA,Bodorkos S,Kamo SL,Hickman AH and Corfu F.2009.Measurement of SIMS instrumental mass fractionation of Pb isotopes during zircon dating.Geostandards and Geoanalytical Research,33(2):145-168
Tang GQ,Li XH,Li QL,Liu Y,Ling XX and Yin QZ.2015.Deciphering the physical mechanism of the topography effect for oxygen isotope measurements using a Cameca IMS-1280 SIMS.Journal of Analytical Atomic Spectrometry,30(4):950-956
Wu FY,Li XH,Yang JH and Zheng YF.2007.Discussions on the petrogenesis of granites.Acta Petrologica Sinica,23(6):1217-1238(in Chinese with English abstract)
Wu YB and Zheng YF.2004.Genesis of zircon and its constraints on interpretation of U-Pb age.Chinese Science Bulletin,49(15):1554-1569
Yang YN,Li QL,Liu Y,Tang GQ,Ling XX and Li XH.2014.Zircon U-Pb dating by secondary ion mass spectrometry.Earth Science Frontiers,21(2):81-92(in Chinese with English abstract)
Zhou Q,Yin QZ,Young ED,Li XH,Wu FY,Li QL,Liu Y and Tang GQ.2013.SIMS Pb-Pb and U-Pb age determination of eucrite zircons at<5μm scale and the first 50Ma of the thermal history of Vesta.Geochimica et Cosmochimica Acta,110:152-175
陈道公,李彬贤,夏群科,吴元保,程昊.2001.变质岩中锆石U-Pb计时问题评述---兼论大别造山带锆石定年.岩石学报,17(1):129-138
李秋立,杨蔚,刘宇,唐国强,郝佳龙,张建超,胡森,赵旭晁,陈雅丽,储雪蕾,王英,蒋云,张爱铖,徐伟彪,林杨挺,李献华.2013.离子探针微区分析技术及其在地球科学中的应用进展.矿物岩石地球化学通报,32(3):310-327
李献华,唐国强,龚冰,杨岳衡,侯可军,胡兆初,李秋立,刘宇,李武显.2013.Qinghu(清湖)锆石:一个新的U-Pb年龄和O,Hf同位素微区分析工作标样.科学通报,58(20):1954-1961
吴福元,李献华,杨进辉,郑永飞.2007.花岗岩成因研究的若干问题.岩石学报,23(6):1217-1238
吴元保,郑永飞.2004.锆石成因矿物学研究及其对U-Pb年龄解释的制约.科学通报,49(16):1589-1604
杨亚楠,李秋立,刘宇,唐国强,凌潇潇,李献华.2014.离子探针锆石U-Pb定年.地学前缘,21(2):81-92