赣中南城县辉绿岩锆石LA-ICPMS年代学及岩石地球化学特征
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摘要
燕山期是华南地区最主要的成矿阶段。近年,越来越多的学者认为该时期形成的众多金属矿床与基性岩脉关系密切。赣中南城地区Au-U等多金属矿化异常明显,区域范围内辉绿岩脉发育。本文针对地表辉绿岩样品进行岩石地球化学和年代学等方面研究。分析结果表明,研究区内岩石主量元素表现相对富铝(w(Al_2O_3)=12.07%～13.71%),富镁和富钙(w(MgO)=8.77%～10.86%;w(CaO)=10.77%～12.21%),低钛和低碱(w(TiO_2)=1.18%～1.58%;w(Na_2O+K_2O)=3.09%～4.01%),Mg~#=8.91～55.78,w(FeO~T)=14.41%～16.87%,表明研究区内辉绿岩的基性程度较高,初始岩浆演化程度不高,早期没有发生明显的分离结晶作用,岩浆来源具有壳幔混合特征。样品整体富集Rb,Ba,Th,La,Sm等元素,亏损K,Hf,Ti,Yb,Lu等元素。REE配分曲线呈平缓的右倾轻稀土元素富集型,样品(La/Yb)_N值在41.25～71.73之间且Ce,Eu无异常。其成岩年龄为158.0 Ma±3.4 Ma,形成于晚侏罗世,辉绿岩的成岩时间与该时期赣中南古陆大部分辉绿岩形成大地构造背景差异性较大,说明赣中南古陆在该时期大地构造背景复杂,推测当时研究区辉绿岩形成于华南和华北地块碰撞引起的多阶段岩石圈伸展拉张的构造环境。
Polymetallic mineralization abnormalies of Au-U in the Nancheng area of central Jiangxi Province are obvious. Geochemical and chronological study for the well developed diabase dikes in the area is carried out so as to understand the important metallogenic stages of Yanshanian.It shows that the main elements of the diabase in the study area are relatively rich in aluminum(w(Al_2O_3)=12.07%～13.71%),magnesium(w(MgO)=8.77%～10.86% and calcium w(CaO)=10.77%～12.21%),low in titanium(w(TiO_2)=1.18%～1.58% and alkali w(Na_2O+K_2O)=3.09%～4.01%),with the Mg~#=8.91～55.78 and w(FeO~T)=14.41%～16.87%,characteristic of high basic extent of the diabase,low evolution extent of magma,unclear fractional crystallization in the early stage and crust-mantle mixing magma.The diabase samples are enriched in Rb,Ba,Th,La and Sm,and depleted in K,Hf,Ti,Yb and Lu with gentle and right-incline REE distribution pattern.(La/Yb)_N value of the diabase sample is in the range of 41.25 to 71.73 and there is no abnormality for elements Ce and Eu.Zircon LA-IC-PMS age dating for the diabase yields a emplacement age of 158.0 Ma±3.4 Ma,a late Jurassic period magmatic product,which is quite different from the geotectonic setting of diabase in most of the ancient continents of central-south Jiangxi paleo-continent during this period.It is considered that the tectonic setting of the central-south Jiangxi paleo-continent in this period was complicated and the diabase in the study area was formed in the tectonic setting of multi-stage lithosphere extension caused by the collision between the South China block and North China block.
Polymetallic mineralization abnormalies of Au-U in the Nancheng area of central Jiangxi Province are obvious. Geochemical and chronological study for the well developed diabase dikes in the area is carried out so as to understand the important metallogenic stages of Yanshanian.It shows that the main elements of the diabase in the study area are relatively rich in aluminum(w(Al_2O_3)=12.07%～13.71%),magnesium(w(MgO)=8.77%～10.86% and calcium w(CaO)=10.77%～12.21%),low in titanium(w(TiO_2)=1.18%～1.58% and alkali w(Na_2O+K_2O)=3.09%～4.01%),with the Mg~#=8.91～55.78 and w(FeO~T)=14.41%～16.87%,characteristic of high basic extent of the diabase,low evolution extent of magma,unclear fractional crystallization in the early stage and crust-mantle mixing magma.The diabase samples are enriched in Rb,Ba,Th,La and Sm,and depleted in K,Hf,Ti,Yb and Lu with gentle and right-incline REE distribution pattern.(La/Yb)_N value of the diabase sample is in the range of 41.25 to 71.73 and there is no abnormality for elements Ce and Eu.Zircon LA-IC-PMS age dating for the diabase yields a emplacement age of 158.0 Ma±3.4 Ma,a late Jurassic period magmatic product,which is quite different from the geotectonic setting of diabase in most of the ancient continents of central-south Jiangxi paleo-continent during this period.It is considered that the tectonic setting of the central-south Jiangxi paleo-continent in this period was complicated and the diabase in the study area was formed in the tectonic setting of multi-stage lithosphere extension caused by the collision between the South China block and North China block.
引文
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[7] 赵正,陈毓川,曾载淋,等.江西银坑W-Ag-Au多金属矿田成矿规律与找矿方向:兼论华南两个成矿系列叠加问题[J].地学前缘,2017,24(5):54-61.
[8] 杨庆刊,张小亮,华琛,等.赣中大王山钨钼多金属矿集区辉钼矿微量元素地球化学特征[J].矿物岩石,2018,38(02):59-69.
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[13] 侯贵廷,刘玉琳,李江海,等.关于基性岩墙群的U-Pb SHRIMP地质年代学的探讨——以鲁西莱芜辉绿岩岩墙为例[J].岩石矿物学杂志,2005,24(3):179-185.
[14] 张明记,李晓峰,韦星林,等.江西德兴银山矿床辉绿岩锆石LA-ICP-MSU-Pb定年及其地质意义[J].矿物学报,2016,36(01):25-33.
[15] 刘勇,李廷栋,肖庆辉,等.湘南宜章地区辉绿岩、花岗斑岩、安山岩的形成时代和成因——锆石U-Pb年龄和Hf同位素组成[J].地质通报,2012,31(09):1 363-1 378.
[16] Wilson B M.Igneous petrogenesis[M].Springer,1989,1-457.
[17] 金鑫镖,王磊,向华,等.湖南桃江地区印支期辉绿岩成因——地球化学、年代学和Sr-Nd-Pb同位素约束[J].地质通报,2017,36(05):750-760.
[18] 池际尚.中国东部新生代玄武岩及上地幔研究[M].中国地质大学出版社,1988.
[19] 邱家骧.关于火山岩区工作的两个问题[J].地质与勘探,1977,(03):20-31.
[20] Sun,S.S,Mcdonough,W.F.Chemical and Isotopic Systematics of Oceanic Basalts:Implications for Mantle Composition and Processes[J].Geological Society of London Special Publications,1989,42,313-345.
[21] Mcdonough W F,Sun S S.The composition of the Earth [J].Chemical Geology,1995,120(3-4):223-253.
[22] 张健,李怀坤,张传林,等.塔里木克拉通东北缘Columbia超大陆裂解事件:库鲁克塔格地区辉绿岩床的地球化学、锆石U-Pb年代学和Hf-O同位素证据[J/OL].地学前缘,2018:1-18.
[23] WOOD D A.A variably veined suboceanic upper mantle-genetic significance for mid-ocean ridge basalts from geochemical evidence[J].Geology,1979,7(10):499-503.
[24] POLATA,HOFMANN A W,ROSING M T.Boninite-like volcanic rocks in the 3.7-3.8Ga Isua green stone belt,West Greenland:geochemical evidence for intra-oceanic subduction zone processes in the early Earth[J].Chemical Geology,2002,184(3):231-254.
[25] PEARCE J A.Immobile element finger printing of ophiolites [J].Elements,2014,10(2):101-108.
[26] 王生伟,廖震文,孙晓明,等.云南东川铜矿区古元古代辉绿岩地球化学——Columbia超级大陆裂解在扬子陆块西南缘的响应[J].地质学报,2013,87(12):1 834-1 852.
[27] Ewart A,Collerson K D,RegelousM.Geochemical evolution with in the Tonga-Kermadec-Lauarc-backarc systems:the role of varying mantal wedge compostion in space and time[J].Journal of Petrology,1998,39(3):331-368.
[28] 赵振华,包志伟,张伯友.湘南中生代玄武岩类地球化学特征[J].中国科学(D辑),1998(S2):8-15.
[29] 朱捌,凌洪飞,沈渭洲,等.粤北下庄矿田晚白垩世辉绿玢岩的地球化学特征及其构造意义[J].地质论评,2008,54(1):26-36.
[30] 李献华,胡瑞忠,饶冰.粤北白垩纪基性岩脉的年代学和地球化学[J].地球化学,1997,(02):19-21+25-36.
[31] 支霞臣,冯家麟.汉诺坝玄武岩的地球化学.见:刘若新主编.中国新生代火山岩年代学与地球化学[M].北京:地震出版社,1992,114-148.
[32] 曹豪杰,黄国龙,许丽丽,等.诸广花岗岩体南部油洞断裂带辉绿岩脉的Ar-Ar年龄及其地球化学特征[J].地质学报,2013,87(7):957-966.
[33] Hofmann A W,White W M.Mantle plumes from ancient oceanic crust[J].Earth & Planetary Science Letters,1982,57(2):421-436.
[34] Rudnick R L,Gao S.Composit ion of the continental crust[J].Treatise on geochemistry,2003,1-64.
[35] Meschede M.A method of discriminating between different types ofmid-ocean ridge basalts and continental tholeiites with the Nb-Zr-Y Diagram[J].Chemical Geology,1986,56(3-4):207-218.
[36] Pearce J A,Norry M J.Petrogenetic implications of Ti,Zr,Y and Nb variations in volcanic rocks[J].Contributions to mineralogyand Petrology,1979,69(1):33-47.
[37] 陈培荣,华仁民,章邦桐,等.南岭燕山早期后造山花岗岩类:岩石学制约和地球动力学背景[J].中国科学,2002,32(4):279-289.
[38] 毛景文,谢桂青,李晓峰,等.华南地区中生代大规模成矿作用与岩石圈多阶段伸展[J].地学前缘,2004,11(1):45-55.
[39] 李献华.华南白垩纪岩浆活动与岩石圈伸展——地质年代学与地球化学限制[A] .中国科学院地球化学研究所.资源环境与可持续发展[C] .北京:科学出版社,1999,264-275.
[2] 胡瑞忠,李朝阳,倪师军,等.华南花岗岩型铀矿床成矿热液中ΣCO2来源研究[J].中国科学(B辑化学生命科学地学),1993(02):189-196.
[3] 郭锋,范蔚茗,林舸,等.湖南道县辉长岩包体的年代学研究及成因探讨[J] .科学通报,1997,42(15):1 661-1663.
[4] Hsu K J,Li J L,Chen H H,et al.Tectonic of South China:Key to understanding West Pactific geology[J].Tectonophys,1990,183:9-39.
[5] 金文山,孙大中.华南大陆深部地壳结构及其演化[M].北京:地质出版社,1997.
[6] 苏晔.赣中聚源钨矿花岗斑岩地球化学特征及其地质意义[D].东华理工大学,2017.
[7] 赵正,陈毓川,曾载淋,等.江西银坑W-Ag-Au多金属矿田成矿规律与找矿方向:兼论华南两个成矿系列叠加问题[J].地学前缘,2017,24(5):54-61.
[8] 杨庆刊,张小亮,华琛,等.赣中大王山钨钼多金属矿集区辉钼矿微量元素地球化学特征[J].矿物岩石,2018,38(02):59-69.
[9] Jackson SE,Pearson NJ,Griffin WL,et al.The application of laser ablation inductively coupled plasma-mass spectrometry to in situ U-Pb zircon geochronology[J].Chemical geology,2004,211:47-69.
[10] Belousova E A,Griffin W L,Shee S R,et al.Two age populations of zircons from the Timber Creek kimberlites,Northern Territory,as determined by laser-ablation ICP-MS analysis.[J].Australian Journal of Earth Sciences,2001,48:757-765.
[11] Ludwig K R.Users Manual for Isoplot/Ex rev.2.49.2001
[12] Vavra G,Gebauer D,Schmid R,et al.Multiple zircon growth and recrystallization during polyphase Late Carboniferous to Triassic metamorphism in granulites of the Ivrea Zone ( Southern Alps):An ion microprobe (SHRIMP) study[J].Contrib Mineral Petrol,1996,122(4):337-358.
[13] 侯贵廷,刘玉琳,李江海,等.关于基性岩墙群的U-Pb SHRIMP地质年代学的探讨——以鲁西莱芜辉绿岩岩墙为例[J].岩石矿物学杂志,2005,24(3):179-185.
[14] 张明记,李晓峰,韦星林,等.江西德兴银山矿床辉绿岩锆石LA-ICP-MSU-Pb定年及其地质意义[J].矿物学报,2016,36(01):25-33.
[15] 刘勇,李廷栋,肖庆辉,等.湘南宜章地区辉绿岩、花岗斑岩、安山岩的形成时代和成因——锆石U-Pb年龄和Hf同位素组成[J].地质通报,2012,31(09):1 363-1 378.
[16] Wilson B M.Igneous petrogenesis[M].Springer,1989,1-457.
[17] 金鑫镖,王磊,向华,等.湖南桃江地区印支期辉绿岩成因——地球化学、年代学和Sr-Nd-Pb同位素约束[J].地质通报,2017,36(05):750-760.
[18] 池际尚.中国东部新生代玄武岩及上地幔研究[M].中国地质大学出版社,1988.
[19] 邱家骧.关于火山岩区工作的两个问题[J].地质与勘探,1977,(03):20-31.
[20] Sun,S.S,Mcdonough,W.F.Chemical and Isotopic Systematics of Oceanic Basalts:Implications for Mantle Composition and Processes[J].Geological Society of London Special Publications,1989,42,313-345.
[21] Mcdonough W F,Sun S S.The composition of the Earth [J].Chemical Geology,1995,120(3-4):223-253.
[22] 张健,李怀坤,张传林,等.塔里木克拉通东北缘Columbia超大陆裂解事件:库鲁克塔格地区辉绿岩床的地球化学、锆石U-Pb年代学和Hf-O同位素证据[J/OL].地学前缘,2018:1-18.
[23] WOOD D A.A variably veined suboceanic upper mantle-genetic significance for mid-ocean ridge basalts from geochemical evidence[J].Geology,1979,7(10):499-503.
[24] POLATA,HOFMANN A W,ROSING M T.Boninite-like volcanic rocks in the 3.7-3.8Ga Isua green stone belt,West Greenland:geochemical evidence for intra-oceanic subduction zone processes in the early Earth[J].Chemical Geology,2002,184(3):231-254.
[25] PEARCE J A.Immobile element finger printing of ophiolites [J].Elements,2014,10(2):101-108.
[26] 王生伟,廖震文,孙晓明,等.云南东川铜矿区古元古代辉绿岩地球化学——Columbia超级大陆裂解在扬子陆块西南缘的响应[J].地质学报,2013,87(12):1 834-1 852.
[27] Ewart A,Collerson K D,RegelousM.Geochemical evolution with in the Tonga-Kermadec-Lauarc-backarc systems:the role of varying mantal wedge compostion in space and time[J].Journal of Petrology,1998,39(3):331-368.
[28] 赵振华,包志伟,张伯友.湘南中生代玄武岩类地球化学特征[J].中国科学(D辑),1998(S2):8-15.
[29] 朱捌,凌洪飞,沈渭洲,等.粤北下庄矿田晚白垩世辉绿玢岩的地球化学特征及其构造意义[J].地质论评,2008,54(1):26-36.
[30] 李献华,胡瑞忠,饶冰.粤北白垩纪基性岩脉的年代学和地球化学[J].地球化学,1997,(02):19-21+25-36.
[31] 支霞臣,冯家麟.汉诺坝玄武岩的地球化学.见:刘若新主编.中国新生代火山岩年代学与地球化学[M].北京:地震出版社,1992,114-148.
[32] 曹豪杰,黄国龙,许丽丽,等.诸广花岗岩体南部油洞断裂带辉绿岩脉的Ar-Ar年龄及其地球化学特征[J].地质学报,2013,87(7):957-966.
[33] Hofmann A W,White W M.Mantle plumes from ancient oceanic crust[J].Earth & Planetary Science Letters,1982,57(2):421-436.
[34] Rudnick R L,Gao S.Composit ion of the continental crust[J].Treatise on geochemistry,2003,1-64.
[35] Meschede M.A method of discriminating between different types ofmid-ocean ridge basalts and continental tholeiites with the Nb-Zr-Y Diagram[J].Chemical Geology,1986,56(3-4):207-218.
[36] Pearce J A,Norry M J.Petrogenetic implications of Ti,Zr,Y and Nb variations in volcanic rocks[J].Contributions to mineralogyand Petrology,1979,69(1):33-47.
[37] 陈培荣,华仁民,章邦桐,等.南岭燕山早期后造山花岗岩类:岩石学制约和地球动力学背景[J].中国科学,2002,32(4):279-289.
[38] 毛景文,谢桂青,李晓峰,等.华南地区中生代大规模成矿作用与岩石圈多阶段伸展[J].地学前缘,2004,11(1):45-55.
[39] 李献华.华南白垩纪岩浆活动与岩石圈伸展——地质年代学与地球化学限制[A] .中国科学院地球化学研究所.资源环境与可持续发展[C] .北京:科学出版社,1999,264-275.