桂东北苗儿山张家花岗岩LA-ICP-MS锆石U-Pb年龄与地球化学特征
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摘要
对张家岩体乍古田矿床及张家矿床的2件赋矿围岩样品,开展LA-ICP-MS锆石U-Pb同位素定年,获得乍古田矿床赋矿围岩形成年龄为218.0±1.4Ma,张家矿床赋矿围岩形成年龄为226.8±5.7Ma。另外,对张家岩体8件样品的主量、微量元素及Sr-Nd同位素分析测试显示,张家花岗岩富硅(Si O2=74.35%~76.29%)、高铝(Al2O3=12.54%~14.03%)、高碱(Na2O+K2O=6.95%~9.17%)、低镁(Mg O=0.34%~0.45%)、低钙(Ca O=0.68%~1.03%)、低钛(Ti O2=0.106%~0.18%),属高钾钙碱性花岗岩;富集Rb,亏损Ba、Sr,Rb/Sr值高,属于低Ba-Sr花岗岩;轻稀土元素富集,负Eu异常;富U(平均21.5×10-6),Th/U值低(平均1.63),有利于铀矿化;(87Sr/86Sr)i高(约0.7247),低εNd(t)值(平均-13.95),二阶段Nd模式年龄为2.07~2.19Ga。张家花岗岩属于强过铝质S型花岗岩,可能是华夏板块古元古代基底变泥质岩经部分熔融形成的。
Two samples were collected near the Zhagutian uranium ore deposit and Zhangjia uranium ore deposit respectively to carry out LA-ICP-MS zircon U-Pb isotopic dating. The analytical result demonstrates that the formation age of the host rock in the Zhagutian uranium ore district is 218.0±1.4 Ma, whereas the formation age of the host rock in the Zhangjia uranium ore district is 226.8±5.7 Ma. Furthermore, the Zhangjia granite is characterized by high Si O2(74.35%~76.29%), Al2 O3(12.54%~14.03%) and(Na2 O+K2 O)(6.95%~9.17%), but low Mg O(0.34%~0.45%), Ca O(0.68%~1.03%) and Ti O2(0.106%~0.18%), so it belongs to high-K calc-alkaline series granite. The Zhangjia granite is rich in Rb, and poor in Ba, Sr with high Rb/Sr ratio, so it belongs to low Ba-Sr granite series.The granite is rich in LREEs with negative Eu anomalies. Meanwhile, The granite is rich in U(21.5×10-6 on average)with low Th/U ratio(1.63 on average), so it is very favourable for uranium mineralization. The granite has high(87 Sr/86 Sr)i(~0.7247), low εNd(t)(-13.95 on average) and its two-stage Nd isotopic model ages are(2.07~2.19 Ga). The Zhangjia granite belongs to strongly peraluminous S-type granite. It probably originated from partial melting of Proterozoic sedimentary metamorphic rocks.
Two samples were collected near the Zhagutian uranium ore deposit and Zhangjia uranium ore deposit respectively to carry out LA-ICP-MS zircon U-Pb isotopic dating. The analytical result demonstrates that the formation age of the host rock in the Zhagutian uranium ore district is 218.0±1.4 Ma, whereas the formation age of the host rock in the Zhangjia uranium ore district is 226.8±5.7 Ma. Furthermore, the Zhangjia granite is characterized by high Si O2(74.35%~76.29%), Al2 O3(12.54%~14.03%) and(Na2 O+K2 O)(6.95%~9.17%), but low Mg O(0.34%~0.45%), Ca O(0.68%~1.03%) and Ti O2(0.106%~0.18%), so it belongs to high-K calc-alkaline series granite. The Zhangjia granite is rich in Rb, and poor in Ba, Sr with high Rb/Sr ratio, so it belongs to low Ba-Sr granite series.The granite is rich in LREEs with negative Eu anomalies. Meanwhile, The granite is rich in U(21.5×10-6 on average)with low Th/U ratio(1.63 on average), so it is very favourable for uranium mineralization. The granite has high(87 Sr/86 Sr)i(~0.7247), low εNd(t)(-13.95 on average) and its two-stage Nd isotopic model ages are(2.07~2.19 Ga). The Zhangjia granite belongs to strongly peraluminous S-type granite. It probably originated from partial melting of Proterozoic sedimentary metamorphic rocks.
引文
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[2]徐伟昌,张洪运.苗儿山岗岩复式岩基年代学研究的进展及时代划分方案[J].岩石学报,1994,10(3):330-334.
[3]谢晓华,陈卫锋,赵葵东,等.桂东北豆乍山花岗岩年代学与地球化学特征[J].岩石学报,2008,24(6):1302-1312.
[4]石少华.桂北沙子江铀矿床矿床地球化学[D].中国科学院地球化学研究所博士学位论文,2011:1-116.
[5]胡欢,王汝成,陈卫锋,等.桂东北豆乍山产铀花岗岩的铀源矿物研究[J].地质论评,2012,58(6):1056-1068.
[6]胡欢,王汝成,陈卫锋,等.桂东北豆乍山产铀花岗岩热液活动时限的确定与铀成矿意义[J].科学通报,2013,36:3849-3858.
[7]方适宜,范立亭,陶志军,等.豆乍山产铀花岗岩中暗色残留体特征及其成因[J].铀矿地质.2014,30(4):2012-2018.
[8]孙涛,王志成,陈培荣,等.南岭地区晚中生代花岗岩成因与岩石圈动力学演化[M].北京:科学出版社,2007:504-519.
[9]Anderson T.Correction of common Pb in U-Pb analyses that do not report204Pb[J].Chemical Geology,2002,192:59-79.
[10]Liu X M,Gao S,Diwu C R.Simultaneous in situ determination of U-Pb age and trace elements in zircon by LA-ICP-MS in 20μm spot size[J].Chinese Science Bulletin,2007,52(9):1257-1264.
[11]Ludwig K R.User's Manual for Isoplot 3.0:a geochronological Toolkit for Microsoft Excel[J].Berkeley Geochron Center,Special,Publication,2003:41-71.
[12]周佐民,谢才富,孙文良,等.江西乐安咸口花岗岩体的锆石LAICP-MS定年及构造意义[J].地质学报,2015,89(1):83-98.
[13]王军,万传辉,赖湘濡,等.粤北下庄矿田太平庵地区闪长玢岩的发现及其年代学特征[J].地质论评,2016,C1:335-336.
[14]陈金勇,范洪海,王生云,等.纳米比亚欢乐谷地区白岗岩型铀矿成矿物质来源分析[J].地质学报,2016,90(2):219-230.
[15]王志成.南岭湘桂段中生代壳源岩浆作用和铀成矿作用[D].南京大学博士学位论文,2003.
[16]吴元保,郑永飞.锆石成因矿物学研究及其对U-Pb年龄解释的制约[J].科学通报,2004,49(16):1589-1604.
[17]Belousova E,Griffin W,O'Reilly S,et al.Igneous zircon:trace element composition as an indicator of source rock type[J].Contrib.Mineral.Petrol,2002,143(5):602-622.
[18]李妩巍,王敢,陈卫锋,等.香草坪花岗岩体年代学和地球化学特征[J].铀矿地质,2010,26(4):215-221.
[19]Watson E B.Zicron saturation in felsic liquids:Experimental data and applications to trace element geochemistry[J].Contributions to Mineralogy and Petrology,1979,70:407-419.
[20]Watson E B,Hamson T M.Zicron saturation revisited:Temperature and composition effects in a variety of crustal magma types[J].Earth Planetary Science Letters,1983,64:295-304.
[21]Middlemost E A K.Naming material in the magama/igneous rock system[J].Earth-Sci.Rev.,1994,37:215-224.
[22]Peccerillo R,Taylor S R.Geochemistry of eocene calc-alkaline volcanic rocks from the Kastamonu area,Northern Turkey[J].Contrib.Mineral Petrol.,1976,58:63-81.
[23]Maniar P D,Piccolli P M.Tectonic discrimination of granitoid[J].Geol.Soc.Am.Bull.,1989,101:635-643.
[24]Nakada S,Takahashi M.Regional variation in chemistry of the Miocene intermediate to felsic magmas in the Outer Zone and the Setouchi province of southwest Japan[J].Journal of the Geological Society of Japan,1979,85:57125-57182.
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[26]Boynton W V.Geochemistry of the rare earth elements:Meteorite studies[C]//Henderson P.Rare earth element geochemistry.Elsevier,1984:63-114.
[27]孙涛,周新民,陈培荣,等.南岭东段中生代强过铝花岗岩成因及其大地构造意义[J].中国科学(D辑),2003,33(12):1209–1218.
[28]Gao S,Luo T C,Zhang B R.Structure and composition of the Continental crust in east China[J].Science in China(Seires D),1999,42(2):129-140.
[29]Rudnick R,Land Fountain D M.Nature and composition of the continental crust:A lower crustal Perspective[J].Review of Geophysics,1995,33:267-309.
[30]赵伦山,张本仁.地球化学[M].北京:地质出版社,1988:1-404.
[31]Zhao K D,Jiang S Y,Ling H F,et al.Late Triassic U-bearing and barren granites in the Miao’ershan batholith,South China:Petrogenetic discrimination and exploration significance[J].Ore Geology Reviews,2016,77:260-278.
[32]Janh B M,Wu F Y,Lo C H,et al.Crust-mantle interaction induced by deep subduction of the continental crust[J].Chem.Geol.,1999,157:119-146.
[33]沈渭洲,朱金初,刘昌实,等.华南基底变质岩的Sm-Nd同位素及其对花岗岩类物质来源的制约[J].岩石学报,1993,9:115-124.
[34]Sylvester P J.Post-collisional strongly peraluminous granites[J].Lithos,1998,45(1/4):29-44.
[35]舒良树.华南构造演化的基本特征[J].地质通报,2012,31(7):1035-1053.
[36]谢才富,朱金初,丁式江,等.海南尖峰岭花岗岩体的形成时代、成因及其与抱伦金矿的关系[J].岩石学报,2006,22(10):2498-2508.
[37]周新民.对华南花岗岩研究的若干思考[J].高校地质学报,2003,9(4):556-565.
[38]郭福祥.中国南方中新生代大地构造属性和南华造山带褶皱过程[J].地质学报,1998,72(1):22-23.
[39]Carter A,Roques D,Bristow C.Understanding Mesozoic accretion in Southeast Asia:Significance of Triassic thermotectonism(Indosinian orogeny)in Vietnam[J].Geology,2001,29:211-214.
[40]于津海,王丽娟,王孝磊,等.赣东南富城杂岩体的地球化学和年代学研究[J].岩石学报,2007,23(6):1441-1456.
[41]舒斌,王平安,李中坚,等.海南抱伦金矿的成矿时代研究及其意义[J].现代地质,2004,18(3):316-320.
[42]邓希光,陈志刚,李献华,等.桂东南地区大容山-十万大山花岗岩带SHRIMP锆石U-Pb定年[J].地质论评,2004,50(4):426-432.
[43]邱检生,Mc Innes B I A,徐夕生,等.赣南大吉山五里亭岩体的锆石LA-ICPMS定年及其与钨成矿关系的新认识[J].地质论评,2004,50(2):125-133.
[44]张文兰,华仁民,王汝成,等.江西大吉山五里亭花岗岩单颗粒锆石U-Pb同位素年龄及其地质意义[J].地质学报,2004,78(3):352-358.
[45]徐夕生,邓平,O’eifly S Y.华南贵东杂岩体单颗粒锆石激光探针ICPMS U-Pb定年及其成岩意义[J].科学通报,2003,48(12):1328-1334.
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