江西相山铀矿田河元背地区流纹斑岩地球化学、锆石U-Pb年龄及Hf-Sr-Nd同位素特征
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摘要
在江西相山铀矿田河元背地区实施的CUSD3钻孔,发现其深部存在晚期侵入到打鼓顶组流纹英安岩、凝灰岩、泥质粉砂岩中的流纹斑岩。利用激光等离子质谱分析技术(LA-ICP-MS)测得流纹斑岩的锆石~(206)Pb/~(238)U年龄为(131.8±0.7)Ma(MSWD=0.41),晚于前人所测的鹅湖岭组碎斑流纹岩年龄。该流纹斑岩具有高硅、富钾、铝过饱和等特点,还表现出高场强元素Rb、Th、U、La、Ce、Nd和LREE富集,Ba、Nb、Sr、P、Ti等元素亏损以及δEu明显负异常的特点。锆石的ε_(Hf)(t)值介于-6.77~-10.38之间,对应的二阶段Hf模式年龄T_(DMC)介于1 619~1 846 Ma,岩石的I_(Sr)值为0.710 92~0.712 01,ε_(Nd)(t)值为-8.18~-9.19。其稀土元素、微量元素分布模式及同位素特征与前人报道的碎斑流纹岩特征类似,暗示流纹斑岩与碎斑流纹岩具有相同的物质来源。以上特征说明河元背地区流纹斑岩形成于早白垩世造山运动碰撞后伸展阶段,为深部硅铝质地壳部分熔融的产物。相山西部流纹斑岩的发现,可以推测该区或许存在一个次级火山机构。
A suite of rhyolite porphyry was found at Heyuanbei in Xiangshan uranium ore-field of Jiangxi Province,which intruded into the rhyodacite,tuff,argillaceous siltstone. LA-ICP-MS U-Pb isotopic dating on zircons from the rhyolite porphyry yields magmatic crystallization age of( 131. 8 ± 0. 7) Ma( MSWD = 0. 41). The rhyolite porphyry is characterized by high in SiO_2,K_2O,Al_2O_3 and relatively low in MnO and P_2O_5. It is enriched in Rb,Th,U,La,Ce,Nd and light rare earth elements,depleted in Ba,Nb,Sr,P and Ti,and shown slightly negative Eu anomalies( δEu =0. 21-0. 25). The zircon ε_(Hf)( t) values range from -6. 77 to -10. 38,with Hf depleted mantle model ages( T_(DMC)) between 1 619 and 1 846 Ma. The I_(Sr)values range from 0. 710 92 to 0. 712 01. And the ε_(Nd)( t) values range from -8. 18 to -9. 19. The experimental results indicate that the rock was generated by partial melting of crustal rocks during extension in Lower Cretaceous. And a sub-volcanic conduit may exist in the west of Xiangshan.
A suite of rhyolite porphyry was found at Heyuanbei in Xiangshan uranium ore-field of Jiangxi Province,which intruded into the rhyodacite,tuff,argillaceous siltstone. LA-ICP-MS U-Pb isotopic dating on zircons from the rhyolite porphyry yields magmatic crystallization age of( 131. 8 ± 0. 7) Ma( MSWD = 0. 41). The rhyolite porphyry is characterized by high in SiO_2,K_2O,Al_2O_3 and relatively low in MnO and P_2O_5. It is enriched in Rb,Th,U,La,Ce,Nd and light rare earth elements,depleted in Ba,Nb,Sr,P and Ti,and shown slightly negative Eu anomalies( δEu =0. 21-0. 25). The zircon ε_(Hf)( t) values range from -6. 77 to -10. 38,with Hf depleted mantle model ages( T_(DMC)) between 1 619 and 1 846 Ma. The I_(Sr)values range from 0. 710 92 to 0. 712 01. And the ε_(Nd)( t) values range from -8. 18 to -9. 19. The experimental results indicate that the rock was generated by partial melting of crustal rocks during extension in Lower Cretaceous. And a sub-volcanic conduit may exist in the west of Xiangshan.
引文
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[2]刘昌实,朱金初,沈渭洲,等.华南陆壳改造系列花岗岩类型划分和成岩物质来源[J].地质学报,1990,64(1):43-52.
[3]夏林圻,夏祖春,张诚,等.相山高位岩浆房分异机制和演化[J].岩石学报,1992,8(3):205-221.
[4]夏林圻,夏祖春,张诚,等.相山中生代含铀火山杂岩岩石地球化学[M].北京:地质出版社,1992:1-35.
[5]李邦达.江西相山碎斑熔岩成因及其控矿作用的讨论[J].地质论评,1993,39(2):101-110.
[6]吴仁贵,余达淦,张树明.相山铀矿田流纹英安斑岩的厘定及与铀矿化的关系[J].铀矿地质,2003,19(2):81-87.
[7]范洪海,王德滋,沈渭洲,等.江西相山火山-侵入杂岩及中基性脉岩形成时代研究[J].地质论评,2005,51(1):86-91.
[8]张万良,李子颖.相山“流纹英安岩”单颗粒锆石U-Pb年龄及地质意义[J].岩石矿物学杂志,2007,26(1):21-26.
[9]刘国奇,夏菲,潘家永,等.基于多元统计的相山铀矿田微量元素地球化学特征分析[J].矿物岩石地球化学通报,2011,30(4):423-432.
[10]王德滋,刘昌实,沈渭洲,等.江西东乡—相山中生代S型火山岩带的发现及其地质意义[J].科学通报,1991,36(19):1491-1493.
[11]王德滋,刘昌实,沈渭洲,等.桐庐I型和相山S型两类碎斑熔岩对比[J].岩石学报,1993,9(1):44-54.
[12]刘昌实,楚雪君,沈渭洲,等.江西东乡—相山中生代火山岩中富铝矿物的发现和成因意义[J].地质论评,1992,38(2):157-163.
[13]范洪海,凌洪飞,王德滋,等.江西相山铀矿田成矿物质来源的Nd、Sr、Pb同位素证据[J].高校地质学报,2001,7(2):139-145.
[14]王传文,侯文尧,万国良,等.相山及邻区碎斑流纹岩的特征和成因[J].放射性地质,1982(3):193-198.
[15]吴仁贵.相山地区如意亭剖面火山建造特征[J].华东地质学院学报,1999,22(3):201-208.
[16]张万良.相山火山-侵入杂岩的反方向岩浆演化系列研究[J].中国地质,2005,32(4):548-556.
[17]李子颖,张万良.江西相山矿田主要铀矿化类型及其地球化学特征对比研究[J].现代地质,2016,30(1):1-16.
[18]杨水源,蒋少涌,赵葵东,等.江西相山铀矿田邹家山矿床中流纹斑岩的锆石U-Pb年代学、岩石地球化学与Sr-Nd-Hf同位素组成[J].岩石学报,2012,28(12):3915-3928.
[19]聂江涛,李子颖,王健,等.江西相山矿田多金属成矿流体特征与成矿作用[J].地质通报,2015,34(2/3):535-547.
[20]杨水源,蒋少涌,姜耀辉,等.江西相山流纹英安岩和流纹英安斑岩锆石U-Pb年代学和Hf同位素组成及其地质意义[J].中国科学:地球科学,2010,40(8):953-969.
[21]陈正乐,陈柏林,潘家永,等.江西相山铀矿床成矿规律总结研究[M].北京:地质出版社,2015:1-10.
[22]YUAN H L,GAO S,DAI M N,et al.Simultaneous determinations of U-Pb age,Hf isotopes and trace element compositions of zircon by excimer laser-ablation quadrupole and multiple-collector ICP-MS[J].Chemical Geology,2008,247(1/2):100-118.
[23]LIU Y S,HU Z C,ZONG K Q,et al.Reappraisement and refinement of zircon U-Pb isotope and trace element analyses by LAICP-MS[J].Chinese Science Bulletin,2010,55(15):1535-1546.
[24]廖群安,李昌年,王京名.江绍断裂带晚侏罗世S型酸性火山岩特征及其地质意义[J].地球科学:中国地质大学学报,1999,24(1):63-68.
[25]CHAPPELL B W,WHITE A J R.Two contracting granite types[J].Pacific Geology,1974,8:173-174.
[26]李子颖,黄志章,李秀珍,等.相山火成岩与铀成矿作用[M].北京:地质出版社,2014:56-72.
[27]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(1):313-345.
[28]马昌前.结晶分异作用的岩浆动力学条件[J].地球科学:中国地质大学学报,1989,14(3):245-252.
[29]张旗.花岗质岩浆能够结晶分离和演化吗?[J].岩石矿物学杂志,2012,31(2):252-260.
[30]JAHN B W,WU F Y,HONG D W.Important crustal growth in the Phanerozoic:Isotopic evidence of granitoids from East-central Asia[J].Journal of Earth System Science,2000,109(1):5-20.
[31]陈迪云,周文斌,吴伯林.相山碎斑熔岩铷-锶、氧、铅同位素地球化学研究[J].南京大学学报(地球科学版),1994,6(1):45-50.
[32]陈小明,陆建军,刘昌实,等.桐庐、相山火山-侵入杂岩单颗粒锆石U-Pb年龄[J].岩石学报,1999,15(2):272-278.
[33]陈正乐,王永,周永贵,等.江西相山火山-侵入杂岩体锆石SHRIMP定年及其地质意义[J].中国地质,2013,40(1):217-231.
[34]范洪海,凌洪飞,沈渭洲,等.相山火山-侵入杂岩Nd-Sr-Pb同位素地球化学特征[J].岩石学报,2001,17(3):395-402.
[35]COLLINS W J,BEAMS S D,WHITE A J R,et al.Nature and origin of A-type granites with particular reference to southeastern Australia[J].Contributions to Mineralogy and Petrology,1982,80(2):189-200.
[36]李同柱,代堰锫,马国桃,等.扬子陆块西缘乌拉溪花岗岩体SHRIMP锆石U-Pb定年及地质意义[J].矿物岩石地球化学通报,2016,35(4):743-749.
[37]ALTHERR R,HOLL A,HEGNER E,et al.High-potassium,calc-alkaline I-type plutonism in the European Variscides:Northern Vosges(France)and Northern Schwarzwald(Germany)[J].Lithos,2000,50(1/3):51-73.
[38]范洪海,凌洪飞,王德滋,等.相山铀矿田成矿机理研究[J].铀矿地质,2003,19(4):208-213.
[39]李子颖,李秀珍,林锦荣.试论华南中新生代地幔柱构造、铀成矿作用及其找矿方向[J].铀矿地质,1999,15(1):9-17.
[40]李子颖.华南热点铀成矿作用[J].铀矿地质,2006,22(2):65-69.
[41]HARRIS N B W,PEARCE J A,TINDLE A G.Geochemical characteristics of collision-zone magmatism[J].Geological Society of London Special Publications,1986,19(5):67-81.
[42]PEARCE J A,HARRIS N B W,TINDLE A G.Trace element discrimination diagrams for the tectonic interpretation of granitic rocks[J].Journal of Petrology,1984,25(4):956-983.
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