鲁西郯城蛇纹岩微量元素和锆石U-Pb年代学:对华北陆块东部岩石圈地幔改造的启示
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摘要
对鲁西郯城蛇纹岩进行锆石LA-ICP-MS U-Pb年代学和全岩微量元素研究。结果为:蛇纹岩中44颗锆石的年龄值可以分为5组,其中岩浆锆石的年龄为古元古代—新太古代(1 815～2 518 Ma)、新元古代(711 Ma、719 Ma)、早白垩世(106～122 Ma)和晚白垩世(78～92 Ma),而变质锆石形成于晚三叠世(225～231 Ma)。郯城蛇纹岩轻重稀土元素分馏不明显,相对富集大离子亲石元素(Ba、Th、U),相对亏损高场强元素(Nb、Zr、Hf),整体上与华北陆块代表古老岩石圈地幔残留的橄榄岩类包体地球化学特征相类似。蛇纹岩的原岩为纯橄岩,是华北陆块东部古老岩石圈地幔的残留。古元古代—新太古代岩浆锆石的存在,代表拆沉的华北陆块基底物质对岩石圈地幔的改造;新元古代岩浆锆石和晚三叠世变质锆石的发育,表明蛇纹岩的原岩受到了由超高压变质作用的俯冲-断离扬子陆壳物质熔融产生的熔体改造;早白垩世和晚白垩世岩浆锆石年龄的出现,与华北陆块东部该时期发育的岩浆作用时间相一致。华北陆块东部岩石圈地幔受到多阶段、不同性质熔体的改造,改造的峰期发生在早白垩世,与华北陆块东部岩石圈发生大规模减薄的峰期时间一致。
Zircon LA-ICP-MS U-Pb geochronology and trace-element geochemistry for serpentinites from Tancheng,western Shandong were carried out in this paper. The results show that ages of 44 zircons in serpentinite are divided into five distinct groups,of which the ages of magmatic zircons are Paleoproterozoic-Neoarchean( 1 815 ～ 2 518 Ma),Neoproterozoic( 711 Ma and 719 Ma),Early Cretaceous( 106 ～ 122 Ma) and Late Cretaceous( 78 ～ 92 Ma),whereas the age of the metamorphic zircons is Late Triassic( 225 ～ 231 Ma). The light rare earth elements and heavy rare earth elements of the Tancheng serpentinites are not well fractionated. The Tancheng serpentinites are relatively rich in large ion lithophilic elements( Ba,Th,U) and relatively deficient in high field strength elements( Nb,Zr,Hf). Generally,the serpentinites are similar to the peridotite xenoliths representing the ancient lithospheric mantle in the North China Block( NCB). Therefore,it is believed that the protolith of serpentinite is dunite and it is the residue of old lithospheric mantel in eastern NCB. The occurrence of Paleoproterozoic-Neoarchean zircons represents the modification of lithospheric mantle from delamination of ancient basement materials in NCB. The development of Neoproterozoic magmatic zircons and Late Triassic metamorphic zircons show that the protolith of serpentinite experienced melt-related modification from the subduction-faulted Yangtze continental crust with ultrahigh pressure metamorphism. The occurrence of Early and Late Cretaceous magmatic zircons is coincident with the coeval magmatism in eastern NCB. The lithospheric mantle in eastern NCB was modified by various melt with multi-stages. The modification peak time is Early Cretaceous,coincident with the peak time for the lithosphere thinning of eastern NCB.
Zircon LA-ICP-MS U-Pb geochronology and trace-element geochemistry for serpentinites from Tancheng,western Shandong were carried out in this paper. The results show that ages of 44 zircons in serpentinite are divided into five distinct groups,of which the ages of magmatic zircons are Paleoproterozoic-Neoarchean( 1 815 ～ 2 518 Ma),Neoproterozoic( 711 Ma and 719 Ma),Early Cretaceous( 106 ～ 122 Ma) and Late Cretaceous( 78 ～ 92 Ma),whereas the age of the metamorphic zircons is Late Triassic( 225 ～ 231 Ma). The light rare earth elements and heavy rare earth elements of the Tancheng serpentinites are not well fractionated. The Tancheng serpentinites are relatively rich in large ion lithophilic elements( Ba,Th,U) and relatively deficient in high field strength elements( Nb,Zr,Hf). Generally,the serpentinites are similar to the peridotite xenoliths representing the ancient lithospheric mantle in the North China Block( NCB). Therefore,it is believed that the protolith of serpentinite is dunite and it is the residue of old lithospheric mantel in eastern NCB. The occurrence of Paleoproterozoic-Neoarchean zircons represents the modification of lithospheric mantle from delamination of ancient basement materials in NCB. The development of Neoproterozoic magmatic zircons and Late Triassic metamorphic zircons show that the protolith of serpentinite experienced melt-related modification from the subduction-faulted Yangtze continental crust with ultrahigh pressure metamorphism. The occurrence of Early and Late Cretaceous magmatic zircons is coincident with the coeval magmatism in eastern NCB. The lithospheric mantle in eastern NCB was modified by various melt with multi-stages. The modification peak time is Early Cretaceous,coincident with the peak time for the lithosphere thinning of eastern NCB.
引文
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[7]Zhu R X,Zhang H F,Zhu G,et al.Craton destruction and related resources[J].International Journal of Earth Sciences,2017,106:2233-2257.
[8]Zhao G C,Wilde S A,Cawood P A,et al.Archean blocks and their boundaries in the North China Craton:lithological,geochemical,structural and P-T path constraints and tectonic evolution[J].Precambrian Research,2001,107(1):45-73.
[9]Xie Z P,Hattorl K,Wang J.Origins of ultramafic rocks in the Sulu ultrahigh-pressure terrane,eastern China[J].Lithos,2013,178(9):158-170.
[10]Li Q,Wen Z H,Hou F H,et al.The genesis of Yangkou serpentinites in the Sulu ultra-high-pressure terrane:evidence from mineral chemistry,geochemistry and geochronology[J].Geological Bulletin of China,2016,35(11):1784-1796.
[11]Yang D B,Xu W L,Zhao G C,et al.Tectonic implications of Early Cretaceous low-Mg adakitic rocks generated by partial melting of thickened lower continental crust at the southern margin of the central North China Craton[J].Gondwana Research,2016,38:220-237.
[12]Lan T G,Fan H R,Santosh M,et al.Early Jurassic high-K calc-alkaline and shoshonitic rocks from the Tongshi intrusive complex,eastern North China Craton:implication for crust-mantle interaction and post-collisional magmatism[J].Lithos,2012,140/141:183-199.
[13]Xu W L,Yang D B,Gao S,et al.Geochemistry of peridotite xenoliths in Early Cretaceous high-Mg#diorites from the central orogenic block of the North China Craton:the nature of Mesozoic lithospheric mantle and constraints on lithospheric thinning[J].Chemical Geology,2010,270(1):257-273.
[14]Zhang R Y,Yang J S,Wooden J L,et al.U-Pb SHRIMP geochronology of zircon in garnet peridotite from the Sulu UHP terrane,China:implications for mantle metasomatism and subduction-zone UHP metamorphism[J].Earth and Planetary Science Letters,2005,237(3):729-743.
[15]Sun S S,Mcdonough W F.Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J].Geological Society Special Publication,London,1989,42(1):313-345.
[16]Liu X M,Gao S,Diwu C R,et al.Precambrian crustal growth of Yangtze Craton as revealed by detrital zircon studies[J].American Journal of Science,2008,308(4):421-468.
[17]Ames L,Tilton G R,Zhou G Z.Timing of collision of the Sino-Korean and Yangtze cratons:U-Pb zircon dating of coesite-bearing eclogites[J].Geology,1993,21(4):339-342.
[18]Yang C H,Xu W L,Yang,et al.Petrogenesis of Shangyu gabbro-diorites in western Shandong:geochronological and geochemical evidence[J].Science in China(Ser.D):Earth Sciences,2008,51(4):481-492.
[19]Yang D B,Xu W L,Wang Q H,et al.Chronology and geochemistry of Mesozoic granitoids in the Bengbu area,central China:constraints on the tectonic evolution of the eastern North China Craton[J].Lithos,2010,114(1/2):200-216.
[20]杨承海,许文良,杨德彬,等.鲁西济南辉长岩的形成时代:锆石LA-ICP-MS U-Pb定年证据[J].地球学报,2005,26(4):321-325.YANG Cheng-hai,XU Wen-liang,YANG De-bin,et al.Chronology of the Jinan gabbro in western Shandong:evidence from LA-ICP-MS Zircon U-Pb dating[J].Acta Geoscientica Sinica,2005,26(4):321-325.
[21]杨德彬,许文良,裴福萍,等.徐淮地区早白垩世adakitic岩石的年代学和Pb同位素组成:对岩浆源区与华北克拉通东部构造演化的制约[J].岩石学报,2008,24(8):1745-1758.YANG De-bin,XU Wen-liang,PEI Fu-ping,et al.Chronology and Pb isotope compositions of Early Cretaceous adakitic rocks in Xuzhou-Huaibei area,central China:constrains on magma sources and tectonic evolution in the eastern North China Craton[J].Acta Petrologica Sinica,2008,24(8):1745-1758.
[22]Ying J F,Zhang H F,Kita N,et al.Nature and evolution of Late Cretaceous lithospheric mantle beneath the eastern North China Craton:constraints from petrology and geochemistry of peridotitic xenoliths from Junan,Shandong Province,China[J].Earth and Planetary Science Letters,2006,244(3):622-638.
[23]王冬艳,许文良,冯宏,等.辽西中生代晚期岩石圈地幔的性质:来自玄武岩和地幔捕虏体的证据[J].吉林大学学报(地球科学版),2002,32(4):319-324.WANG Dong-yan,XU Wen-liang,FENG Hong,et al.Nature of Late Mesozoic lithospheric mantle in western Liaoning Province:evidences from basalt and the mantle-derived xenoliths[J].Journal of Jilin University(Earth Science Edition),2002,32(4):319-324.
[24]Tang Y J,Zhang H F,Nakamura E,et al.Multistage melt/fluid-peridotite interactions in the refertilized lithospheric mantle beneath the North China Craton:constraints from the Li-Sr-Nd isotopic disequilibrium between minerals of peridotite xenoliths[J].Contributions to Mineralogy and Petrology,2011,161(6):845-861.
[25]路凤香.华北克拉通古老岩石圈地幔的多次地质事件:来自金伯利岩中橄榄岩捕虏体的启示[J].岩石学报,2010,26(11):3177-3188.LU Feng-xiang.Multiple-geological events of ancient lithospheric mantle beneath North China Craton:as inferred from peridotite xenoliths in kimberlite[J].Acta Petrologica Sinica,2010,26(11):3177-3188.
[2]师江朋,霍腾飞,杨浩田,等.鲁西下常庄中三叠世磁铁角闪岩的岩石地球化学和Sr-Nd同位素:对岩石成因和构造背景的制约[J].世界地质,2016,35(3):608-616.SHI Jiang-peng,HUO Teng-fei,YANG Hao-tian,et al.Geochemistry and Sr-Nd isotope compositions of Middle Triassic Xiachangzhuang magnetite amphibolites from western Shandong:constraints on petrogenesis and tectonic setting[J].Global Geology,2016,35(3):608-616.
[3]Xu W L,Hergt J M,Gao S,et al.Interaction of adakitic melt-peridotite:implications for the high-Mg#signature of Mesozoic adakitic rocks in the eastern North China Craton[J].Earth and Planetary Science Letters,2008,265(1):123-137.
[4]Yang D B,Xu W L,Gao S,et al.Repeated modification of lithospheric mantle in the eastern North China Craton:constraints from SHRIMP zircon U-Pb dating of dunite xenoliths in western Shandong[J].Science Bulletin,2012,57(6):651-659.
[5]Rudnick R L,Gao S.The composition of the continental crust[C]//Rudnick R L.The crust,vol.3:treatise on geochemistry,Oxford:Elsevier,2003:1-64.
[6]Xu Y G.Thermo-tectonic destruction of the Archean lithospheric keel beneath the Sino-Korean Craton in China:evidence,timing and mechanism[J].Physics and Chemistry of the Earth,2001,26(9/10):747-757.
[7]Zhu R X,Zhang H F,Zhu G,et al.Craton destruction and related resources[J].International Journal of Earth Sciences,2017,106:2233-2257.
[8]Zhao G C,Wilde S A,Cawood P A,et al.Archean blocks and their boundaries in the North China Craton:lithological,geochemical,structural and P-T path constraints and tectonic evolution[J].Precambrian Research,2001,107(1):45-73.
[9]Xie Z P,Hattorl K,Wang J.Origins of ultramafic rocks in the Sulu ultrahigh-pressure terrane,eastern China[J].Lithos,2013,178(9):158-170.
[10]Li Q,Wen Z H,Hou F H,et al.The genesis of Yangkou serpentinites in the Sulu ultra-high-pressure terrane:evidence from mineral chemistry,geochemistry and geochronology[J].Geological Bulletin of China,2016,35(11):1784-1796.
[11]Yang D B,Xu W L,Zhao G C,et al.Tectonic implications of Early Cretaceous low-Mg adakitic rocks generated by partial melting of thickened lower continental crust at the southern margin of the central North China Craton[J].Gondwana Research,2016,38:220-237.
[12]Lan T G,Fan H R,Santosh M,et al.Early Jurassic high-K calc-alkaline and shoshonitic rocks from the Tongshi intrusive complex,eastern North China Craton:implication for crust-mantle interaction and post-collisional magmatism[J].Lithos,2012,140/141:183-199.
[13]Xu W L,Yang D B,Gao S,et al.Geochemistry of peridotite xenoliths in Early Cretaceous high-Mg#diorites from the central orogenic block of the North China Craton:the nature of Mesozoic lithospheric mantle and constraints on lithospheric thinning[J].Chemical Geology,2010,270(1):257-273.
[14]Zhang R Y,Yang J S,Wooden J L,et al.U-Pb SHRIMP geochronology of zircon in garnet peridotite from the Sulu UHP terrane,China:implications for mantle metasomatism and subduction-zone UHP metamorphism[J].Earth and Planetary Science Letters,2005,237(3):729-743.
[15]Sun S S,Mcdonough W F.Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J].Geological Society Special Publication,London,1989,42(1):313-345.
[16]Liu X M,Gao S,Diwu C R,et al.Precambrian crustal growth of Yangtze Craton as revealed by detrital zircon studies[J].American Journal of Science,2008,308(4):421-468.
[17]Ames L,Tilton G R,Zhou G Z.Timing of collision of the Sino-Korean and Yangtze cratons:U-Pb zircon dating of coesite-bearing eclogites[J].Geology,1993,21(4):339-342.
[18]Yang C H,Xu W L,Yang,et al.Petrogenesis of Shangyu gabbro-diorites in western Shandong:geochronological and geochemical evidence[J].Science in China(Ser.D):Earth Sciences,2008,51(4):481-492.
[19]Yang D B,Xu W L,Wang Q H,et al.Chronology and geochemistry of Mesozoic granitoids in the Bengbu area,central China:constraints on the tectonic evolution of the eastern North China Craton[J].Lithos,2010,114(1/2):200-216.
[20]杨承海,许文良,杨德彬,等.鲁西济南辉长岩的形成时代:锆石LA-ICP-MS U-Pb定年证据[J].地球学报,2005,26(4):321-325.YANG Cheng-hai,XU Wen-liang,YANG De-bin,et al.Chronology of the Jinan gabbro in western Shandong:evidence from LA-ICP-MS Zircon U-Pb dating[J].Acta Geoscientica Sinica,2005,26(4):321-325.
[21]杨德彬,许文良,裴福萍,等.徐淮地区早白垩世adakitic岩石的年代学和Pb同位素组成:对岩浆源区与华北克拉通东部构造演化的制约[J].岩石学报,2008,24(8):1745-1758.YANG De-bin,XU Wen-liang,PEI Fu-ping,et al.Chronology and Pb isotope compositions of Early Cretaceous adakitic rocks in Xuzhou-Huaibei area,central China:constrains on magma sources and tectonic evolution in the eastern North China Craton[J].Acta Petrologica Sinica,2008,24(8):1745-1758.
[22]Ying J F,Zhang H F,Kita N,et al.Nature and evolution of Late Cretaceous lithospheric mantle beneath the eastern North China Craton:constraints from petrology and geochemistry of peridotitic xenoliths from Junan,Shandong Province,China[J].Earth and Planetary Science Letters,2006,244(3):622-638.
[23]王冬艳,许文良,冯宏,等.辽西中生代晚期岩石圈地幔的性质:来自玄武岩和地幔捕虏体的证据[J].吉林大学学报(地球科学版),2002,32(4):319-324.WANG Dong-yan,XU Wen-liang,FENG Hong,et al.Nature of Late Mesozoic lithospheric mantle in western Liaoning Province:evidences from basalt and the mantle-derived xenoliths[J].Journal of Jilin University(Earth Science Edition),2002,32(4):319-324.
[24]Tang Y J,Zhang H F,Nakamura E,et al.Multistage melt/fluid-peridotite interactions in the refertilized lithospheric mantle beneath the North China Craton:constraints from the Li-Sr-Nd isotopic disequilibrium between minerals of peridotite xenoliths[J].Contributions to Mineralogy and Petrology,2011,161(6):845-861.
[25]路凤香.华北克拉通古老岩石圈地幔的多次地质事件:来自金伯利岩中橄榄岩捕虏体的启示[J].岩石学报,2010,26(11):3177-3188.LU Feng-xiang.Multiple-geological events of ancient lithospheric mantle beneath North China Craton:as inferred from peridotite xenoliths in kimberlite[J].Acta Petrologica Sinica,2010,26(11):3177-3188.