西藏班公湖-怒江缝合带中段去申拉组火山岩锆石U-Pb年龄及Hf同位素特征
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摘要
西藏班公湖-怒江缝合带广泛分布中生代岩浆活动,对于认识特提斯洋的演化有重要的启示。班公湖-怒江缝合带中段东卡错微陆块去申拉组安山岩的锆石U-Pb测年和Hf同位素测试结果显示,其中21个测点给出的锆石~(206)Pb/~(238)U年龄加权平均值为110.3±0.7Ma;ε_(Hf)(t)值为-5.66～1.05,二阶段Hf模式年龄为1020～1448Ma,表现出壳幔混源的特征。综合区域构造沉积演化及前人研究成果,认为东卡错微陆块内发育的去申拉组火山岩很可能与早白垩世班公湖-怒江洋壳南向俯冲消减引起的板片断离有关,并形成于板内伸展环境,其岩浆来源于聂荣微陆块成熟地壳物质发生深熔或重熔作用形成的酸性熔体与古老岩石圈地幔部分熔融产生的基性熔体的混合。
Mesozoic magmatic activities are widely distributed in the Bangong Co-Nujiang suture zone in Tibet, and it is important to study them for understanding the evolution of the Tethys Ocean. This paper reports the zircon U-Pb dating and zircon Hf isotope data of the andesites of the Qushenla Formation in the Dongkaco microcontinental block of the middle Bangong Co-Nujiang suture zone. The zircon ~(206)Pb/~(238)U weighted age of the andesites obtained from 21 sites is 110.3±0.7 Ma. Zircon Hf isotope analysis shows that the zircon εHf(t)varies in the range of -5.66～1.05, and second stage Hf model ages are 1020～1448 Ma, showing the characteristics of crust-mantle mixing. Considering regional tectonic sedimentary evolution and previous research results, the authors hold that the volcanic rocks of the Qushenla Formation were probably related to the slab break-offduring southward subduction of the Bangong Co-Nujiang oceanic crust in the Early Cretaceous, and were produced in an intraplate extensional environment. The magma was derived from the mixing of acidic melt formed by deep melting or remelting of mature crustal material in Nyainrong microcontinent with basic melt formed by partial melting of ancient lithospheric mantle.
Mesozoic magmatic activities are widely distributed in the Bangong Co-Nujiang suture zone in Tibet, and it is important to study them for understanding the evolution of the Tethys Ocean. This paper reports the zircon U-Pb dating and zircon Hf isotope data of the andesites of the Qushenla Formation in the Dongkaco microcontinental block of the middle Bangong Co-Nujiang suture zone. The zircon ~(206)Pb/~(238)U weighted age of the andesites obtained from 21 sites is 110.3±0.7 Ma. Zircon Hf isotope analysis shows that the zircon εHf(t)varies in the range of -5.66～1.05, and second stage Hf model ages are 1020～1448 Ma, showing the characteristics of crust-mantle mixing. Considering regional tectonic sedimentary evolution and previous research results, the authors hold that the volcanic rocks of the Qushenla Formation were probably related to the slab break-offduring southward subduction of the Bangong Co-Nujiang oceanic crust in the Early Cretaceous, and were produced in an intraplate extensional environment. The magma was derived from the mixing of acidic melt formed by deep melting or remelting of mature crustal material in Nyainrong microcontinent with basic melt formed by partial melting of ancient lithospheric mantle.
引文
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[8]朱弟成,潘桂棠,莫宣学,等.冈底斯中北部晚侏罗世—早白垩世地球动力学环境:火山岩约束[J].岩石学报, 2006,(3):534-546.
[9]朱弟成,潘桂棠,王立全,等.西藏冈底斯带侏罗纪岩浆作用的时空分布及构造环境[J].地质通报, 2008,(4):458-468.
[10]Zhu D C, Pan G T, Zhao Z D, et al. Early Cretaceous subductionrelated adakite-like rocks in the Gangdese, South Tibet:Products ofslab melting and subsequent melt-peridotite interaction?[J].Journal of Asian Earth Sciences, 2009, 34(3):298-309.
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[12]Wang Q, Zhu D C, Zhao Z D, et al. Origin of the ca. 90 Ma magnesia-rich volcanic rocks in SE Nyima, central Tibet:Products of lithospheric delamination beneath the Lhasa-Qiangtang collision zone[J]. Lithos, 2014, 198/199(3):24-37.
[13]陈玉禄,何建社,张宽忠,等.班公错-怒江结合带中段的构造格局探讨[C]//青藏高原及邻区地质与资源环境学术讨论会论文摘要汇编. 2003.
[14]潘桂棠,莫宣学,侯增谦,等.冈底斯造山带的时空结构及演化[J].岩石学报, 2006,(3):521-533.
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[21]侯可军,李延河,邹天人,等. LA-MC-ICP-MS锆石Hf同位素的分析方法及地质应用[J].岩石学报, 2007, 23(10):2595-2604.
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[26]李学森,程立人.藏北申扎、班戈地区奥陶纪和志留纪的一些头足类化石[J].吉林大学学报(地), 1988,(3):241-248.
[27]姚建新,纪占胜,武桂春,等.西藏申扎地区德日昂玛-下拉剖面:冈瓦纳和特提斯晚石炭世—早二叠世地层和古生物对比的桥梁[J].地质通报, 2007, 26(1):31-41.
[28]杨桂芝,王军,王铁成.西藏班戈西南地区中二叠统下拉组岩性特征及时代讨论[J].吉林地质, 2016, 35(4):11-13.
[29]张勇强,钟康惠,刘珂辛.西藏确哈拉群、嘎加组中火山岩特征及其构造意义探讨[C]//全国岩石学与地球动力学研讨会. 2013:545-547.
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[31]李小波,王保弟,刘函,等.西藏达如错地区晚侏罗世高镁安山岩——班公湖-怒江洋壳俯冲消减的证据[J].地质通报, 2015,(2/3):251-261.
[32]李华亮,高成,李正汉,等.西藏班公湖地区竟柱山组时代及其构造意义[J].大地构造与成矿学, 2016, 40(4):663-673.
[33]吴浩,李才,胡培远,等.西藏尼玛县塔色普勒地区去申拉组火山岩的发现及其地质意义[J].地质通报, 2013, 32(7):1014-1026.
[34]吴浩,李才,胡培远,等.藏北班公湖-怒江缝合带早白垩世双峰式火山岩的确定及其地质意义[J].地质通报, 2014,33(11):1804-1814.
[35]Sui Q L, Wang Q, Zhu D C, et al. Compositional diversity of ca.110 Ma magmatism in the northern Lhasa Terrane, Tibet:implications for the magmatic origin and crustal growth in a continent-continent collision zone[J]. Lithos, 2013, 168(3):144-159.
[36]麦源君,杨文光,朱利东,等.西藏羌塘南缘查格隆去申拉组火山岩锆石U-Pb年龄、地球化学特征——对班公湖-怒江洋盆演化时限的制约[J].矿物岩石, 2018, 38(2):70-79.
[37]康志强,许继峰,王保弟.拉萨地块北部去申拉组火山岩:班公湖-怒江特提斯洋南向俯冲的产物?[J].岩石学报, 2010, 26(10):3106-3116.
[38]李伟.西藏改则地区去申拉组火山岩地球化学特征及锆石年代学制约[D].中国地质大学(北京)硕士学位论文, 2012.
[39]朱弟成,莫宣学,赵志丹,等.西藏南部二叠纪和早白垩世构造岩浆作用与特提斯演化:新观点[J].地学前缘, 2009,(2):1-20.
[40]陈莉,徐军,苏犁.场发射环境扫描电子显微镜上阴极荧光谱仪特点及其在锆石研究中的应用[J].自然科学进展,2005,15(11):1403-1408
[41]吴福元,李献华,郑永飞,等. Lu-Hf同位素体系及其岩石学应用[J].岩石学报, 2007, 23(2):185-220.
[42]Wu F Y, Yang Y H, Xie L W, et al. Hf isotopic compositions of the standard zircons and baddeleyites used in U-Pb geochronology[J].Chemical Geology, 2006, 234(1):105-126.
[43]Bolhar R, Weaver S D, Whitehouse M J, et al. Sources and evolution of arc magmas inferred from coupled O and Hf isotope systematics of plutonic zircons from the Cretaceous Separation Point Suite(New Zealand)[J]. Earth&Planetary Science Letters,2008, 268(3/4):312-324.
[44]Kapp P, Murphy M A, Yin A, et al. Mesozoic and Cenozoic tectonic evolution of the Shiquanhe area of western Tibet[J].Tectonics, 2003, 22(4):1029.
[2]Zhu D C, Zhao Z D, Niu Y, et al. The Lhasa Terrane:Record of a microcontinent and its histories of drift and growth[J]. Earth and Planetary Science Letters, 2011, 301:241-255.
[3]陈国荣,陈玉禄,张宽忠,等.班戈县幅地质调查新成果及主要进展[J].地质通报, 2004, 23(5):520-524.
[4]Matte P, Taponnie P, Arnaud N, et al. Tectonics of western Tibet,between the Tarims and the Indus[J]. Earth Planet Sci Lett., 1996,142(3/4):311-320.
[5]史仁灯.班公湖SSZ型蛇绿岩年龄对班-怒洋时限的制约[J].科学通报, 2007, 52(2):223-227.
[6]高顺宝,郑有业,王进寿,等.西藏班戈地区侵入岩年代学和地球化学:对班公湖-怒江洋盆演化时限的制约[J].岩石学报, 2011, 27(7):1973-1982.
[7]Sui Q L, Wang Q, Zhu D C, et al. Compositional diversity of ca.110 Ma magmatism in the northern Lhasa Terrane, Tibet:Implications for the magmatic origin and crustal growth in a continent-continent collision zone[J]. Lithos, 2013, 168(3):144-159.
[8]朱弟成,潘桂棠,莫宣学,等.冈底斯中北部晚侏罗世—早白垩世地球动力学环境:火山岩约束[J].岩石学报, 2006,(3):534-546.
[9]朱弟成,潘桂棠,王立全,等.西藏冈底斯带侏罗纪岩浆作用的时空分布及构造环境[J].地质通报, 2008,(4):458-468.
[10]Zhu D C, Pan G T, Zhao Z D, et al. Early Cretaceous subductionrelated adakite-like rocks in the Gangdese, South Tibet:Products ofslab melting and subsequent melt-peridotite interaction?[J].Journal of Asian Earth Sciences, 2009, 34(3):298-309.
[11]Zhu D C, Zhao Z D, Niu Y, et al. The origin and pre-Cenozoic evolution of the Tibetan Plateau[J]. Gondwana Research, 2013, 23(4):1429-1454.
[12]Wang Q, Zhu D C, Zhao Z D, et al. Origin of the ca. 90 Ma magnesia-rich volcanic rocks in SE Nyima, central Tibet:Products of lithospheric delamination beneath the Lhasa-Qiangtang collision zone[J]. Lithos, 2014, 198/199(3):24-37.
[13]陈玉禄,何建社,张宽忠,等.班公错-怒江结合带中段的构造格局探讨[C]//青藏高原及邻区地质与资源环境学术讨论会论文摘要汇编. 2003.
[14]潘桂棠,莫宣学,侯增谦,等.冈底斯造山带的时空结构及演化[J].岩石学报, 2006,(3):521-533.
[15]中国科学院成都地质矿产研究所.青藏高原及邻区地质图,1:1500000[M].北京:地质出版社, 1988.
[16]王岚,杨理勤,王亚平,等.锆石LA-ICP-MS原位微区U-Pb定年及微量元素的同时测定[J].地球学报, 2012, 33(5):763-772.
[17]Nasdala L, Kronz A, Wirth R, et al. The phenomenon of deficient electron microprobe totals in radiation-damaged and altered zircon[J].Geochimica Et Cosmochimica Acta, 2008, 73(6):1637-1650.
[18]Liu Y S, Hu Z C, Zong K Q, et al. Reappraisement and refinement of zircon U-Pb isotope and trace element analyses by LA-ICP-MS[J]. Science Bulletin, 2010, 55(15):1535-1546.
[19]Ludwig K R. User's Manual for Isoplot 3.0:A Geochronological Toolkit for Microsoft Excel[M]. Berkeley Geochronology Center Special Publication, 2003, 4:1-7l.
[20]侯可军,李延河,田有荣. LA-MC-ICP-MS锆石微区原位UPb定年技术[J].矿床地质, 2009, 28(4):481-492.
[21]侯可军,李延河,邹天人,等. LA-MC-ICP-MS锆石Hf同位素的分析方法及地质应用[J].岩石学报, 2007, 23(10):2595-2604.
[22]Hoskin P W O, Black L P. Metamorphic zircon formation by solid-state recrystallization of protolith igneous zircon[J]. Journal of Metamorphic Geology, 2010, 18(4):423-439.
[23]S?derlund U, Patchett P J, Vervoort J D, et al. The176Lu decay constant determined by Lu-Hf and U-Pb isotope systematics of precambrian mafic intrusions[J]. Earth and Planetary Science Letters, 2004, 219(3/4), 311-324.
[24]Blichert T J, Albarède F. The Lu-Hf isotope geochemistry of chondrites and the evolution of the mantle-crust system[J]. Earth and Planetary Science Letters, 1998, 148:24-258.
[25]Griffin W L, Wang X, Jackson S E, et al. Zircon chemistry and magma mixing, SE China:In-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes[J]. Lithos, 2002, 61(3):237-269.
[26]李学森,程立人.藏北申扎、班戈地区奥陶纪和志留纪的一些头足类化石[J].吉林大学学报(地), 1988,(3):241-248.
[27]姚建新,纪占胜,武桂春,等.西藏申扎地区德日昂玛-下拉剖面:冈瓦纳和特提斯晚石炭世—早二叠世地层和古生物对比的桥梁[J].地质通报, 2007, 26(1):31-41.
[28]杨桂芝,王军,王铁成.西藏班戈西南地区中二叠统下拉组岩性特征及时代讨论[J].吉林地质, 2016, 35(4):11-13.
[29]张勇强,钟康惠,刘珂辛.西藏确哈拉群、嘎加组中火山岩特征及其构造意义探讨[C]//全国岩石学与地球动力学研讨会. 2013:545-547.
[30]西藏自治区地质矿产局.西藏自治区区域地质志[M].北京:地质出版社, 1993.
[31]李小波,王保弟,刘函,等.西藏达如错地区晚侏罗世高镁安山岩——班公湖-怒江洋壳俯冲消减的证据[J].地质通报, 2015,(2/3):251-261.
[32]李华亮,高成,李正汉,等.西藏班公湖地区竟柱山组时代及其构造意义[J].大地构造与成矿学, 2016, 40(4):663-673.
[33]吴浩,李才,胡培远,等.西藏尼玛县塔色普勒地区去申拉组火山岩的发现及其地质意义[J].地质通报, 2013, 32(7):1014-1026.
[34]吴浩,李才,胡培远,等.藏北班公湖-怒江缝合带早白垩世双峰式火山岩的确定及其地质意义[J].地质通报, 2014,33(11):1804-1814.
[35]Sui Q L, Wang Q, Zhu D C, et al. Compositional diversity of ca.110 Ma magmatism in the northern Lhasa Terrane, Tibet:implications for the magmatic origin and crustal growth in a continent-continent collision zone[J]. Lithos, 2013, 168(3):144-159.
[36]麦源君,杨文光,朱利东,等.西藏羌塘南缘查格隆去申拉组火山岩锆石U-Pb年龄、地球化学特征——对班公湖-怒江洋盆演化时限的制约[J].矿物岩石, 2018, 38(2):70-79.
[37]康志强,许继峰,王保弟.拉萨地块北部去申拉组火山岩:班公湖-怒江特提斯洋南向俯冲的产物?[J].岩石学报, 2010, 26(10):3106-3116.
[38]李伟.西藏改则地区去申拉组火山岩地球化学特征及锆石年代学制约[D].中国地质大学(北京)硕士学位论文, 2012.
[39]朱弟成,莫宣学,赵志丹,等.西藏南部二叠纪和早白垩世构造岩浆作用与特提斯演化:新观点[J].地学前缘, 2009,(2):1-20.
[40]陈莉,徐军,苏犁.场发射环境扫描电子显微镜上阴极荧光谱仪特点及其在锆石研究中的应用[J].自然科学进展,2005,15(11):1403-1408
[41]吴福元,李献华,郑永飞,等. Lu-Hf同位素体系及其岩石学应用[J].岩石学报, 2007, 23(2):185-220.
[42]Wu F Y, Yang Y H, Xie L W, et al. Hf isotopic compositions of the standard zircons and baddeleyites used in U-Pb geochronology[J].Chemical Geology, 2006, 234(1):105-126.
[43]Bolhar R, Weaver S D, Whitehouse M J, et al. Sources and evolution of arc magmas inferred from coupled O and Hf isotope systematics of plutonic zircons from the Cretaceous Separation Point Suite(New Zealand)[J]. Earth&Planetary Science Letters,2008, 268(3/4):312-324.
[44]Kapp P, Murphy M A, Yin A, et al. Mesozoic and Cenozoic tectonic evolution of the Shiquanhe area of western Tibet[J].Tectonics, 2003, 22(4):1029.