湘黔地区埃迪卡拉纪-寒武纪之交硅质岩的成因探讨——来自稀土元素和Ge/Si比值的证据
|
摘要
对埃迪卡拉纪-寒武纪之交的贵州铜仁坝黄剖面留茶坡组层状硅质岩和湖南张家界柑子坪剖面留茶坡组穹隆状硅质岩的主量、微量元素和稀土元素以及Ge/Si特征进行分析,探讨两种硅质岩的成因。层状硅质岩的SiO_2含量为96.06%~99.61%,穹窿状硅质岩的SiO_2含量为98.62%~99.56%,平均值为99.13%;其他元素含量很低,两者均为纯硅质岩。坝黄层状硅质岩的∑REE为20.14~248.56μg/g(平均100.62μg/g),Eu/Eu*值为0.90~1.10(平均1.06),无明显异常,Ge/Si值为0.13~0.98μmol/mol(平均0.50μmol/mol),Al_2O_3与∑REE明显正相关,表明硅质岩成分明显受陆源输入的控制。柑子坪穹隆状硅质岩的∑REE值低,为3.75~7.24μg/g(平均5.73μg/g),Ce/Ce*值为0.46~0.66(平均0.57),具负异常,Eu/Eu*值为2.28~11.07(平均4.60),具明显正异常,Ge/Si值为1.09~1.43μmol/mol(平均1.25μmol/mol),Al_2O_3与∑REE的相关性较差,表明硅质岩为海底热液成因。Al_2O_3与Ge/Si的相关性强弱也可以反映硅质岩的来源。结合古地理环境,推断层状硅质岩可能形成于盆地内部,而穹隆状硅质岩可能发育在台缘同生断裂处,因海底热液喷流而形成。以1μmol/mol作为Ge/Si的临界值可以为示踪硅质岩的物质来源提供新的思路。
Two types of Liuchapo Formation cherts, bedded cherts and mounded cherts, were deposited in Bahuang section of Tongren in Guizhou Province and Ganziping section of Zhangjiajie in Hunan Province. The origin of the cherts was discussed by analyzing the characteristics of major, trace elements and REE compositions and Ge/Si ratios. It was revealed that the content of SiO_2 in bedded cherts was range from 96.06% to 99.61%, and the content of SiO_2 in mounded cherts was range from 98.62% to 99.56%, averaging 99.13%, and the contents of other chemical components were very low. Thus, two types of cherts are pure cherts. Moreover, the ∑REE of the bedded cherts in Bahuang section is ranged from 20.14 to 248.56 μg/g(averaging 100.62 μg/g), and no obvious abnormality in Eu/Eu* which is ranged from 0.90 to 1.10(averaging 1.06), and the ratio of Ge/Si is 0.13-0.98 μmol/mol(averaging is 0.50 μmol/mol), indicating that the origin of bedded cherts affected terrigenous input. Whereas, the ∑REE of the mounded cherts in Ganziping district is ranged from 3.75 to 7.24 μg/g(averaging 5.73μg/g), the ratio of Ce/Ce* is 0.46-0.66(averaging 0.57) which shows a negative abnormal, Eu/Eu* is ranged from 2.28 to 11.07(averaging 4.60) which shows a positive abnormal, and Ge/Si ratio is 1.09-1.43 μmol/mol,(averaging 1.25 μmol/mol) all of which reflect a hydrothermal origin of the mounded cherts. Otherwise, the relationship between Al_2O_3 and ∑REE in the bedded cherts has an excellent correlation, while in the mounded cherts has a poor correlation. It also illustrates that continental substance plays an important role in controlling the formation of bedded cherts, and the mounded cherts is originated from submarine volcanic or hydrothermal activity. The relationship between Al_2O_3 and Ge/Si also reflect the origin of cherts. Combined with the paleogeographic environment, it can conclude that the mounded cherts were deposited in syngenetic fault at the margin of the basin, originated from submarine hydrothermal activity, while the bedded cherts were deposit in the deep basin, mainly influenced by terrigenous input. What's more, using 1 μmol/mol as the critical value of Ge/Si may provide a new way to trace the material sources of cherts.
Two types of Liuchapo Formation cherts, bedded cherts and mounded cherts, were deposited in Bahuang section of Tongren in Guizhou Province and Ganziping section of Zhangjiajie in Hunan Province. The origin of the cherts was discussed by analyzing the characteristics of major, trace elements and REE compositions and Ge/Si ratios. It was revealed that the content of SiO_2 in bedded cherts was range from 96.06% to 99.61%, and the content of SiO_2 in mounded cherts was range from 98.62% to 99.56%, averaging 99.13%, and the contents of other chemical components were very low. Thus, two types of cherts are pure cherts. Moreover, the ∑REE of the bedded cherts in Bahuang section is ranged from 20.14 to 248.56 μg/g(averaging 100.62 μg/g), and no obvious abnormality in Eu/Eu* which is ranged from 0.90 to 1.10(averaging 1.06), and the ratio of Ge/Si is 0.13-0.98 μmol/mol(averaging is 0.50 μmol/mol), indicating that the origin of bedded cherts affected terrigenous input. Whereas, the ∑REE of the mounded cherts in Ganziping district is ranged from 3.75 to 7.24 μg/g(averaging 5.73μg/g), the ratio of Ce/Ce* is 0.46-0.66(averaging 0.57) which shows a negative abnormal, Eu/Eu* is ranged from 2.28 to 11.07(averaging 4.60) which shows a positive abnormal, and Ge/Si ratio is 1.09-1.43 μmol/mol,(averaging 1.25 μmol/mol) all of which reflect a hydrothermal origin of the mounded cherts. Otherwise, the relationship between Al_2O_3 and ∑REE in the bedded cherts has an excellent correlation, while in the mounded cherts has a poor correlation. It also illustrates that continental substance plays an important role in controlling the formation of bedded cherts, and the mounded cherts is originated from submarine volcanic or hydrothermal activity. The relationship between Al_2O_3 and Ge/Si also reflect the origin of cherts. Combined with the paleogeographic environment, it can conclude that the mounded cherts were deposited in syngenetic fault at the margin of the basin, originated from submarine hydrothermal activity, while the bedded cherts were deposit in the deep basin, mainly influenced by terrigenous input. What's more, using 1 μmol/mol as the critical value of Ge/Si may provide a new way to trace the material sources of cherts.
引文
[1]Hou X G,Aldridge R J,Bergstr?m J,et al.The Cambrian Fossils of Chengjiang,China:the flowering of early animal life.Oxford:Blackwell,2004
[2]Shields-Zhou G,Och L.The case for a neoproterozoic oxygenation event:geochemical evidence and biological consequences.GSA Today,2011,21(3):4-11
[3]杨競红,蒋少涌,凌洪飞,等.黑色页岩与大洋缺氧事件的Re-Os同位素示踪与定年研究.地学前缘,2005,12(2):143-150
[4]朱茂炎.动物的起源和寒武纪大爆发:来自中国的化石证据.古生物学报,2010,49(3):269-287
[5]Canfield D E,Poulton S W,Knoll A H,et al.Ferruginous conditions dominated Later Neoproterozoic deep-water chemistry.Science,2008,321:949-952
[6]Chen D,Zhou X,Fu Y,et al.New U-Pb zircon ages of the Ediacaran-Cambrian boundary strata in South China.Terra Nova,2015,27(1):62-68
[7]Douthitt C B.The geochemistry of the stable isotopes of silicon.Geochimica et Cosmochimica Acta,1982,46(8):1449-1458
[8]陈永权,蒋少涌,周新源,等.塔里木盆地寒武系层状硅质岩与硅化岩的元素、δ30Si、δ18O地球化学研究.地球化学,2010,39(2):159-170
[9]Murray R W,Brink M R B T,Gerlach D C,et al.Rare earth,major,and trace element composition of Monterey and DSDP chert and associated host sediment:assessing the influence of chemical fractionation during diagenesis.Geochimica et Cosmochimica Acta,1992,56(7):2657-2671
[10]黄华,王国芝.浙黔桂地区寒武纪硅质岩的地球化学特征及其形成背景.沉积与特提斯地质,2011,31(1):100-106
[11]Frei R,Polat A.Source heterogeneity for the major components of~3.7 Ga banded iron formations(Isua Greenstone belt,Western Greenland):tracing the nature of interacting water masses in BIF formation.Earth and Planetary Science Letters,2007,253(1/2):266-281
[12]Delvigne C,Cardinal D,Hofmann A,et al.Stratigraphic changes of Ge/Si,REE+Y and silicon isotopes as insights into the deposition of a Mesoarchaean banded iron formation.Earth and Planetary Science Letters,2012,355/356:109-118
[13]Shen B,Lee C A,Xiao S.Germanium/silica ratios in diagenetic chert nodules from the Ediacaran Doushantuo Formation,South China.Chemical Geology,2011,280(3/4):323-335
[14]Dong L,Shen B,Lee C A,et al.Germanium/silicon of the Ediacaran-Cambrian Laobao cherts:implications for the bedded chert formation and paleoenvironment interpretations.Geochemistry Geophysics Geosystems,2015,16(3):751-763
[15]Alibert C,Kinsley L.Ge/Si in Hamersley BIF as tracer of hydrothermal Si and Ge inputs to the Paleoproterozoic ocean.Geochimica et Cosmochimica Acta,2016,184:329-343
[16]Wang C,Wu H,Li W,et al.Changes of Ge/Si,REE+Y and Sm-Nd isotopes in alternating Fe-and Si-rich mesobands reveal source heterogeneity of the~2.54 Ga Sijiaying banded iron formation in Eastern Hebei,China.Ore Geology Reviews,2016,80:363-376
[17]夏文杰,杜森官,徐新煌,等.中国南方震旦纪岩相古地理与成矿作用.北京:地质出版社,1994
[18]Yeasmin R,Chen D,Fu Y,et al.Climatic-oceanic forcing on the organic accumulation across the shelf during the Early Cambrian(age 2 through 3)in the mid-upper Yangtze Block,NE Guizhou,South China.Journal of Asian Earth Sciences,2017,134:365-386
[19]Chen D,Wang J,Qing H,et al.Hydrothermal venting activities in the Early Cambrian,South China:petrological,geochronological and stable isotopic constraints.Chemical Geology,2009,258(3):168-181
[20]汪建国,陈代钊,严德天,等.湘西地区前寒武纪-寒武纪转折期碳酸盐-硅泥质沉积体系的截然转换:地层-沉积样式形成机理及意义.地质科学,2011,46(1):27-41
[21]Adachi M,Yamamoto K,Sugisaki R.Hydrothermal chert and associated siliceous rocks from the northern Pacific their geological significance as indication of ocean ridge activity.Sedimentary Geology,1986,47(1):125-148
[22]Herzig P M,Becker K P,Stoffers P,et al.Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86°W.Earth and Planetary Science Letters,1988,89(3):261-272
[23]Mc Lennan S M.Rare earth elements in sedimentary rocks:influence of provenance and sedimentary process.Reviews in Mineralogy and Geochemistry,1989,21(1):169-200
[24]彭军,夏文杰,伊海生.湘西晚前寒武纪层状硅质岩的热水沉积地球化学标志及其环境意义.沉积与特提斯地质,1999,19(2):29-37
[25]Murray R W,Gerlach D C,Iii G P R,et al.Rare earth,major,and trace elements in chert from the Franciscan complex and Monterey group,California:assessing REE sources to fine-grained marine sediments.Geochimica et Cosmochimica Acta,1991,55(7):1875–1895
[26]Bolhar R,Kamber B S,Moorbath S,et al.Characterisation of early Archaean chemical sediments by trace element signatures.Earth and Planetary Science Letters,2004,222(1):43-60
[27]Armstrong H A,Owen A W,Floyd J D.Rare earth geochemistry of Arenig cherts from the Ballantrae Ophiolite and Leadhills Imbricate Zone,southern Scotland:implications for origin and significance to the Caledonian Orogeny.Journal of the Geological Society,1999,156(3):549-560
[28]DiasáS,Früh-Green G L,Bernasconi S M,et al.Geochemistry and stable isotope constraints on hightemperature activity from sediment cores of the Saldanha hydrothermal field.Marine Geology,2011,279:128-140
[29]张亚冠,杜远生,徐亚军,等.湘中震旦纪-寒武纪之交硅质岩地球化学特征及成因环境研究.地质论评,2015,61(3):499-510
[30]Slack J F,Grenne T,Bekker A,et al.Suboxic deep seawater in the late Paleoproterozoic:evidence from hematitic chert and iron formation related to seafloor-hydrothermal sulfide deposits,central Arizona,USA.Earth and Planetary Science Letters,2007,255(1/2):243-256
[31]German C R,Klinkhammer G P,Edmond J M,et al.Hydrothermal scavenging of rare-earth elements in the ocean.Nature,1990,345:516-518
[32]遇昊,陈代钊,韦恒叶,等.鄂西地区上二叠乐平统大隆组硅质岩成因及有机质富集机理.岩石学报,2012,28(3):1017-1027
[33]Evans M J,Derry L A.Quartz control of high germanium/silicon ratios in geothermal waters.Geology,2002,30:1019-1022
[34]Hammond D E,Mcmanus J,Berelson W M.Oceanic germanium/silicon ratios:evaluation of the potential overprint of temperature on weathering signals.Paleoceanography,2004,19(2):399-420
[35]Kurtz A C,Derry L A,Chadwick O A.Germaniumsilicon fractionation in the weathering environment.Geochimica et Cosmochimica Acta,2002,66(9):1525-1537
[36]Froelich P N,Blanc V,Mortlock R A,et al.River fluxes of dissolved silica to the ocean were higher during glacials:Ge/Si in diatoms,rivers,and oceans.Paleoceanography,1992,7(6):739–767
[37]Mortlock R A,Froelich P N,Feely R A,et al.Silica and germanium in Pacific Ocean hydrothermal vents and plumes.Earth and Planetary Science Letters,1993,119(3):365-378
[38]Wang J,Chen D,Wang D,et al.Petrology and geochemistry of chert on the marginal zone of Yangtze Platform,western Hunan,South China,during the Ediacaran-Cambrian transition.Sedimentology,2012,59(3):809–829
[39]Fan H,Wen H,Zhu X,et al.Hydrothermal activity during Ediacaran-Cambrian transition:silicon isotopic evidence.Precambrian Research,2013,224:23-35
[40]江永宏,李胜荣.湘、黔地区前寒武-寒武纪过渡时期硅质岩生成环境研究.地学前缘,2005,12(4):622-629
[41]陈代钊,汪建国,严德天,等.中扬子地区早寒武世构造-沉积样式与古地理格局.地质科学,2012,47(4):1052-1070
[42]Rouxel O,Galy A,Elderfield H.Germanium isotopic variations in igneous rocks and marine sediments.Geochimica et Cosmochimica Acta,2006,70(13):3387-3400
[2]Shields-Zhou G,Och L.The case for a neoproterozoic oxygenation event:geochemical evidence and biological consequences.GSA Today,2011,21(3):4-11
[3]杨競红,蒋少涌,凌洪飞,等.黑色页岩与大洋缺氧事件的Re-Os同位素示踪与定年研究.地学前缘,2005,12(2):143-150
[4]朱茂炎.动物的起源和寒武纪大爆发:来自中国的化石证据.古生物学报,2010,49(3):269-287
[5]Canfield D E,Poulton S W,Knoll A H,et al.Ferruginous conditions dominated Later Neoproterozoic deep-water chemistry.Science,2008,321:949-952
[6]Chen D,Zhou X,Fu Y,et al.New U-Pb zircon ages of the Ediacaran-Cambrian boundary strata in South China.Terra Nova,2015,27(1):62-68
[7]Douthitt C B.The geochemistry of the stable isotopes of silicon.Geochimica et Cosmochimica Acta,1982,46(8):1449-1458
[8]陈永权,蒋少涌,周新源,等.塔里木盆地寒武系层状硅质岩与硅化岩的元素、δ30Si、δ18O地球化学研究.地球化学,2010,39(2):159-170
[9]Murray R W,Brink M R B T,Gerlach D C,et al.Rare earth,major,and trace element composition of Monterey and DSDP chert and associated host sediment:assessing the influence of chemical fractionation during diagenesis.Geochimica et Cosmochimica Acta,1992,56(7):2657-2671
[10]黄华,王国芝.浙黔桂地区寒武纪硅质岩的地球化学特征及其形成背景.沉积与特提斯地质,2011,31(1):100-106
[11]Frei R,Polat A.Source heterogeneity for the major components of~3.7 Ga banded iron formations(Isua Greenstone belt,Western Greenland):tracing the nature of interacting water masses in BIF formation.Earth and Planetary Science Letters,2007,253(1/2):266-281
[12]Delvigne C,Cardinal D,Hofmann A,et al.Stratigraphic changes of Ge/Si,REE+Y and silicon isotopes as insights into the deposition of a Mesoarchaean banded iron formation.Earth and Planetary Science Letters,2012,355/356:109-118
[13]Shen B,Lee C A,Xiao S.Germanium/silica ratios in diagenetic chert nodules from the Ediacaran Doushantuo Formation,South China.Chemical Geology,2011,280(3/4):323-335
[14]Dong L,Shen B,Lee C A,et al.Germanium/silicon of the Ediacaran-Cambrian Laobao cherts:implications for the bedded chert formation and paleoenvironment interpretations.Geochemistry Geophysics Geosystems,2015,16(3):751-763
[15]Alibert C,Kinsley L.Ge/Si in Hamersley BIF as tracer of hydrothermal Si and Ge inputs to the Paleoproterozoic ocean.Geochimica et Cosmochimica Acta,2016,184:329-343
[16]Wang C,Wu H,Li W,et al.Changes of Ge/Si,REE+Y and Sm-Nd isotopes in alternating Fe-and Si-rich mesobands reveal source heterogeneity of the~2.54 Ga Sijiaying banded iron formation in Eastern Hebei,China.Ore Geology Reviews,2016,80:363-376
[17]夏文杰,杜森官,徐新煌,等.中国南方震旦纪岩相古地理与成矿作用.北京:地质出版社,1994
[18]Yeasmin R,Chen D,Fu Y,et al.Climatic-oceanic forcing on the organic accumulation across the shelf during the Early Cambrian(age 2 through 3)in the mid-upper Yangtze Block,NE Guizhou,South China.Journal of Asian Earth Sciences,2017,134:365-386
[19]Chen D,Wang J,Qing H,et al.Hydrothermal venting activities in the Early Cambrian,South China:petrological,geochronological and stable isotopic constraints.Chemical Geology,2009,258(3):168-181
[20]汪建国,陈代钊,严德天,等.湘西地区前寒武纪-寒武纪转折期碳酸盐-硅泥质沉积体系的截然转换:地层-沉积样式形成机理及意义.地质科学,2011,46(1):27-41
[21]Adachi M,Yamamoto K,Sugisaki R.Hydrothermal chert and associated siliceous rocks from the northern Pacific their geological significance as indication of ocean ridge activity.Sedimentary Geology,1986,47(1):125-148
[22]Herzig P M,Becker K P,Stoffers P,et al.Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86°W.Earth and Planetary Science Letters,1988,89(3):261-272
[23]Mc Lennan S M.Rare earth elements in sedimentary rocks:influence of provenance and sedimentary process.Reviews in Mineralogy and Geochemistry,1989,21(1):169-200
[24]彭军,夏文杰,伊海生.湘西晚前寒武纪层状硅质岩的热水沉积地球化学标志及其环境意义.沉积与特提斯地质,1999,19(2):29-37
[25]Murray R W,Gerlach D C,Iii G P R,et al.Rare earth,major,and trace elements in chert from the Franciscan complex and Monterey group,California:assessing REE sources to fine-grained marine sediments.Geochimica et Cosmochimica Acta,1991,55(7):1875–1895
[26]Bolhar R,Kamber B S,Moorbath S,et al.Characterisation of early Archaean chemical sediments by trace element signatures.Earth and Planetary Science Letters,2004,222(1):43-60
[27]Armstrong H A,Owen A W,Floyd J D.Rare earth geochemistry of Arenig cherts from the Ballantrae Ophiolite and Leadhills Imbricate Zone,southern Scotland:implications for origin and significance to the Caledonian Orogeny.Journal of the Geological Society,1999,156(3):549-560
[28]DiasáS,Früh-Green G L,Bernasconi S M,et al.Geochemistry and stable isotope constraints on hightemperature activity from sediment cores of the Saldanha hydrothermal field.Marine Geology,2011,279:128-140
[29]张亚冠,杜远生,徐亚军,等.湘中震旦纪-寒武纪之交硅质岩地球化学特征及成因环境研究.地质论评,2015,61(3):499-510
[30]Slack J F,Grenne T,Bekker A,et al.Suboxic deep seawater in the late Paleoproterozoic:evidence from hematitic chert and iron formation related to seafloor-hydrothermal sulfide deposits,central Arizona,USA.Earth and Planetary Science Letters,2007,255(1/2):243-256
[31]German C R,Klinkhammer G P,Edmond J M,et al.Hydrothermal scavenging of rare-earth elements in the ocean.Nature,1990,345:516-518
[32]遇昊,陈代钊,韦恒叶,等.鄂西地区上二叠乐平统大隆组硅质岩成因及有机质富集机理.岩石学报,2012,28(3):1017-1027
[33]Evans M J,Derry L A.Quartz control of high germanium/silicon ratios in geothermal waters.Geology,2002,30:1019-1022
[34]Hammond D E,Mcmanus J,Berelson W M.Oceanic germanium/silicon ratios:evaluation of the potential overprint of temperature on weathering signals.Paleoceanography,2004,19(2):399-420
[35]Kurtz A C,Derry L A,Chadwick O A.Germaniumsilicon fractionation in the weathering environment.Geochimica et Cosmochimica Acta,2002,66(9):1525-1537
[36]Froelich P N,Blanc V,Mortlock R A,et al.River fluxes of dissolved silica to the ocean were higher during glacials:Ge/Si in diatoms,rivers,and oceans.Paleoceanography,1992,7(6):739–767
[37]Mortlock R A,Froelich P N,Feely R A,et al.Silica and germanium in Pacific Ocean hydrothermal vents and plumes.Earth and Planetary Science Letters,1993,119(3):365-378
[38]Wang J,Chen D,Wang D,et al.Petrology and geochemistry of chert on the marginal zone of Yangtze Platform,western Hunan,South China,during the Ediacaran-Cambrian transition.Sedimentology,2012,59(3):809–829
[39]Fan H,Wen H,Zhu X,et al.Hydrothermal activity during Ediacaran-Cambrian transition:silicon isotopic evidence.Precambrian Research,2013,224:23-35
[40]江永宏,李胜荣.湘、黔地区前寒武-寒武纪过渡时期硅质岩生成环境研究.地学前缘,2005,12(4):622-629
[41]陈代钊,汪建国,严德天,等.中扬子地区早寒武世构造-沉积样式与古地理格局.地质科学,2012,47(4):1052-1070
[42]Rouxel O,Galy A,Elderfield H.Germanium isotopic variations in igneous rocks and marine sediments.Geochimica et Cosmochimica Acta,2006,70(13):3387-3400