赞比亚东北部正长花岗岩的锆石U-Pb年龄和Lu-Hf同位素特征
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摘要
本文采用LA-MC-ICP-MS方法获得班韦乌卢地块卡萨马北部正长花岗岩中锆石的~(207)Pb/~(206)Pb年龄加权平均值为2 011±20 Ma(N=17,MSWD=3.9),表明班韦乌卢地块基底中正长花岗岩主要形成于古元古代且可能与古元古代乌本迪构造带的活动有关。岩石中锆石Lu-Hf同位素的T_(DM2)年龄变化范围为3 018～2 184 Ma,明显大于锆石的形成年龄;具有不均一的ε_(Hf)(t)值(-7.1～6.6)显示形成正长花岗岩的原始岩浆具有壳幔混合的特点,可能为新太古代-古元古代地壳与幔源混染物质。
The zircon LA-MC-ICP-MS U-Pb dating results of the syenogranite show that their weighted ~(207)Pb/~(206)U age is 2011 ± 20 Ma(N=17, MSWD=3.9), indicating that the intrusion of the syenogranite intruded in the Palaeoproterozoic have a good relation with the Paleoproterozoic Ubendian Belt. The range of T_(DM2) ages from zircons Lu-Hf isotopic Compositions varies from 3 018 Ma to 2 184 Ma, which is obviously greater than the age of zircon weighted ~(207)Pb/~(206)U age. Zircon variable ε_(Hf)(t) values(from-7.1 to 6.6)show that the origin of the syenogranite was a mixture of Neoarchean-Paleoproterozoic crust-mantle.
The zircon LA-MC-ICP-MS U-Pb dating results of the syenogranite show that their weighted ~(207)Pb/~(206)U age is 2011 ± 20 Ma(N=17, MSWD=3.9), indicating that the intrusion of the syenogranite intruded in the Palaeoproterozoic have a good relation with the Paleoproterozoic Ubendian Belt. The range of T_(DM2) ages from zircons Lu-Hf isotopic Compositions varies from 3 018 Ma to 2 184 Ma, which is obviously greater than the age of zircon weighted ~(207)Pb/~(206)U age. Zircon variable ε_(Hf)(t) values(from-7.1 to 6.6)show that the origin of the syenogranite was a mixture of Neoarchean-Paleoproterozoic crust-mantle.
引文
[1] Andersen L S, Unrug R. Geodynamic evolution of the Bangweulu Block, northern Zambia[J]. Precambrian Research,1984, 25:187-212.
[2] De Waele B, Liégeois J-P, Nemchin A A, et al. Isotopic and geochemical evidence of proterozoic episodic crustal reworking within the irumide belt of south-central Africa,the southern metacratonic boundary of an Archaean Bangweulu Craton[J]. Precambrian Research, 2006,148:225-256.
[3]任军平，王杰，刘晓阳，等.非洲中南部卢弗里安弧CuCo矿床研究进展[J].地质科技情报，2013,32(5):142-152.
[4]任军平，左立波，许康康，等.赞比亚北部班韦乌卢地块演化及矿产资源研究现状[J].地质论评，2016,4:979-996.
[5]任军平，王杰，古阿雷，等.赞比亚卢弗里安弧地区矿产资源研究现状及找矿潜力分析[J].中国矿业，2017a,26(11):139-144.
[6]任军平，王杰，刘晓阳，等.非洲中南部铜多金属矿床研究现状及找矿潜力分析[J].吉林大学学报（地球科学版），2017b,47(4):1083-1103.
[7]任军平，王杰，古阿雷，等.赞比亚东北部卡萨马—陇都地区碎屑锆石裂变径迹年代学特征[J].原子能科学技术，2018,52(12):2275-2282.
[8]任军平，王杰，左立波，等.赞比亚北部省卡萨马西部石英闪长岩锆石U-Pb和Lu-Hf同位素及地球化学特征[J].地质学报，2019. DOI:10.19762/j.cnki.dizhixuebao.2019148.
[9]任军平，王杰，孙宏伟，等.赞比亚东北部卡萨马群形成环境:碎屑锆石U-Pb年龄与Hf同位素的限定[J].中国地质，2019,46(3):575-586.
[10]邢仕，张金达，任军平，等.非洲中南部伊鲁米德构造带演化及成矿作用探讨[J].地质调查与研究，2018,41(3):176-184.
[11] Brewer M S, Haslam H W, Darbyshire D P F, et al. Rb-Sr age determinations in the Bangweulu Block, Luapula Province, Zambia[R]. Institute of Geological Sciences, London,1979, Report 79/5:1-11.
[12] De Waele B, Fitzsimons I C W. The nature and timing of Palaeoproterozoic sedimentation at the southeastern margin of the Congo Craton; zircon U-Pb geochronology of plutonic, volcanic and clastic units in northern Zambia[J]. Precambrian Research, 2007,159:95-116.
[13] Master S, Rainaud C, Armstrong R A, et al. Provenance ages of the Neoproterozoic Katanga Supergroup(Central African Copperbelt), with implications for basin evolution[J].Journal of African Earth Sciences, 2005,42(1):41-60.
[14] Armstrong R A, Master S, Robb L J. Geochronology of the Nchanga Granite, and constraints on the maximum age of the Katanga Supergroup, Zambian Copperbelt[J]. Journal of African Earth Sciences, 2005, 42(1):32-40.
[15] Unrug R. The Mid-Proterozoic Mporokoso Group of northern Zambia:stratigraphy, sedimentation and regional position[J]. Precambrian Research, 1984,24:99-121.
[16] De Waele B, Kampunzu A B, Mapani B S E, et al. The Mesoproterozoic Irumide belt of Zambia[J]. Journal of African Earth Sciences,2006b,46, 36-70.
[17] Debruyne D, Wilderode J V, Balcaen L, et al. Geochemistry and isotopic evolution of the central African Domes, Bangweulu and Irumide regions:Evidence for cryptic Archean sources and a Paleoproterozoic continental arc[J]. Journal of African Earth Sciences,2014,100:145-163.
[18] Geng J Z, Qiu K F, Gou Z Y, et al. Tectonic regime switch over of Triassic Western Qinling Orogen:Constraints from LA-ICP-MS zircon U-Pb geochronology and Lu-Hf isotope of Dangchuan intrusive complex in Gansu, China[J].Geochemistry,2017,77:637-651.
[19] Liu Y S, Gao S, Hu Z C, et al. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J]. Journal of Petrology, 2010,51(1-2):537-571.
[20] Ludwig K R. User’s manual for Isoplot/Ex, version 3.70.A Geochronological Toolkit for Microsoft Excel[M]. Berkeley Geochronology Center Special Publication, 2003,4:1-76.
[21] Anderson T. Correction of common lead in U-Pb analyses that do not report204Pb[J]. Chemical Geology, 2002,192(1/2):59-79.
[22]耿建珍，李怀坤，张健，等.锆石Hf同位素组成的LAMC-ICP-MS测定[J].地质通报，2011,30:1508-1513.
[23] Kazimoto E O, Schenk V, Appel P. Granulite-facies metamorphic events in the northwestern Ubendian Belt of Tanzania:ImplicationsfortheNeoarcheantoPaleoproterozoiccrustalevolution[J].PrecambrianResearch,2015,256:31-47.
[24] Sanislav I V, Wormald R J, Dirks P H G M, et al. Zircon UPb ages and Lu-Hf isotope systematics from late-tectonic granites, Geita Greenstone Belt:Implications for crustal growth of the Tanzania Craton[J]. Precambrian Research,2014, 242:187-204.
[2] De Waele B, Liégeois J-P, Nemchin A A, et al. Isotopic and geochemical evidence of proterozoic episodic crustal reworking within the irumide belt of south-central Africa,the southern metacratonic boundary of an Archaean Bangweulu Craton[J]. Precambrian Research, 2006,148:225-256.
[3]任军平，王杰，刘晓阳，等.非洲中南部卢弗里安弧CuCo矿床研究进展[J].地质科技情报，2013,32(5):142-152.
[4]任军平，左立波，许康康，等.赞比亚北部班韦乌卢地块演化及矿产资源研究现状[J].地质论评，2016,4:979-996.
[5]任军平，王杰，古阿雷，等.赞比亚卢弗里安弧地区矿产资源研究现状及找矿潜力分析[J].中国矿业，2017a,26(11):139-144.
[6]任军平，王杰，刘晓阳，等.非洲中南部铜多金属矿床研究现状及找矿潜力分析[J].吉林大学学报（地球科学版），2017b,47(4):1083-1103.
[7]任军平，王杰，古阿雷，等.赞比亚东北部卡萨马—陇都地区碎屑锆石裂变径迹年代学特征[J].原子能科学技术，2018,52(12):2275-2282.
[8]任军平，王杰，左立波，等.赞比亚北部省卡萨马西部石英闪长岩锆石U-Pb和Lu-Hf同位素及地球化学特征[J].地质学报，2019. DOI:10.19762/j.cnki.dizhixuebao.2019148.
[9]任军平，王杰，孙宏伟，等.赞比亚东北部卡萨马群形成环境:碎屑锆石U-Pb年龄与Hf同位素的限定[J].中国地质，2019,46(3):575-586.
[10]邢仕，张金达，任军平，等.非洲中南部伊鲁米德构造带演化及成矿作用探讨[J].地质调查与研究，2018,41(3):176-184.
[11] Brewer M S, Haslam H W, Darbyshire D P F, et al. Rb-Sr age determinations in the Bangweulu Block, Luapula Province, Zambia[R]. Institute of Geological Sciences, London,1979, Report 79/5:1-11.
[12] De Waele B, Fitzsimons I C W. The nature and timing of Palaeoproterozoic sedimentation at the southeastern margin of the Congo Craton; zircon U-Pb geochronology of plutonic, volcanic and clastic units in northern Zambia[J]. Precambrian Research, 2007,159:95-116.
[13] Master S, Rainaud C, Armstrong R A, et al. Provenance ages of the Neoproterozoic Katanga Supergroup(Central African Copperbelt), with implications for basin evolution[J].Journal of African Earth Sciences, 2005,42(1):41-60.
[14] Armstrong R A, Master S, Robb L J. Geochronology of the Nchanga Granite, and constraints on the maximum age of the Katanga Supergroup, Zambian Copperbelt[J]. Journal of African Earth Sciences, 2005, 42(1):32-40.
[15] Unrug R. The Mid-Proterozoic Mporokoso Group of northern Zambia:stratigraphy, sedimentation and regional position[J]. Precambrian Research, 1984,24:99-121.
[16] De Waele B, Kampunzu A B, Mapani B S E, et al. The Mesoproterozoic Irumide belt of Zambia[J]. Journal of African Earth Sciences,2006b,46, 36-70.
[17] Debruyne D, Wilderode J V, Balcaen L, et al. Geochemistry and isotopic evolution of the central African Domes, Bangweulu and Irumide regions:Evidence for cryptic Archean sources and a Paleoproterozoic continental arc[J]. Journal of African Earth Sciences,2014,100:145-163.
[18] Geng J Z, Qiu K F, Gou Z Y, et al. Tectonic regime switch over of Triassic Western Qinling Orogen:Constraints from LA-ICP-MS zircon U-Pb geochronology and Lu-Hf isotope of Dangchuan intrusive complex in Gansu, China[J].Geochemistry,2017,77:637-651.
[19] Liu Y S, Gao S, Hu Z C, et al. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J]. Journal of Petrology, 2010,51(1-2):537-571.
[20] Ludwig K R. User’s manual for Isoplot/Ex, version 3.70.A Geochronological Toolkit for Microsoft Excel[M]. Berkeley Geochronology Center Special Publication, 2003,4:1-76.
[21] Anderson T. Correction of common lead in U-Pb analyses that do not report204Pb[J]. Chemical Geology, 2002,192(1/2):59-79.
[22]耿建珍，李怀坤，张健，等.锆石Hf同位素组成的LAMC-ICP-MS测定[J].地质通报，2011,30:1508-1513.
[23] Kazimoto E O, Schenk V, Appel P. Granulite-facies metamorphic events in the northwestern Ubendian Belt of Tanzania:ImplicationsfortheNeoarcheantoPaleoproterozoiccrustalevolution[J].PrecambrianResearch,2015,256:31-47.
[24] Sanislav I V, Wormald R J, Dirks P H G M, et al. Zircon UPb ages and Lu-Hf isotope systematics from late-tectonic granites, Geita Greenstone Belt:Implications for crustal growth of the Tanzania Craton[J]. Precambrian Research,2014, 242:187-204.