广西大瑶山大黎花岗岩体年代学研究及地质意义
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摘要
大瑶山成矿带大黎花岗岩体主要岩性为花岗闪长斑岩、花岗闪长岩、二长花岗岩和二长花岗斑岩。岩体侵入于寒武系黄洞口组,两个花岗闪长斑岩的LA-ICP-MS锆石U-Pb定年结果为(99.5±1.4)Ma和(102.3±1.5)Ma,为早白垩世的岩浆活动产物。常量元素具有高硅、富碱、富钙的特点,为钙碱性准铝质系列岩石,显示I型花岗岩的特征。稀土元素具有右倾型的配分模式,∑REE为150.63×10-6~192.13×10-6,轻微的负铕异常,δEu值为0.73~0.85。微量元素富集Rb、U、Th、La、Ce等大离子亲石元素(LILE),亏损Nb、Ta、Ti、P等高场强元素(HFS)。大黎花岗岩的初始Sr比值为0.7076~0.7078,~(147)Sm/~(144)Nd值是0.0960~0.1055,(~(143)Nd/~(144)Nd)i值为0.5122~0.5123,εNd(t)值为-5.29~-3.55,模式年龄T1DM为0.98~1.12Ga;矫正后的~(206)Pb/~(204)Pb、~(207)Pb/~(204)Pb、~(208)Pb/~(204)Pb值分别为18.0745~18.2316、15.6241~15.664、38.4129~38.5852;上述Sr-Nd-Pb同位素特征表明大黎岩体的成岩物质来自于上地壳物质的部分熔融。构造环境判别图解中,大黎花岗岩体形成于一种碰撞的构造环境,可能与燕山晚期古太平洋板块的碰撞作用有关系。
The lithologica characters of Dali granite pluton in the Dayaoshan metallogenic belt mainly include granodiorite,granodiortie-porphyry,monzonitic granite and monzonitic granite porphyry,which intrusive into the Huangdongkou group in Cambrian system.The results of LA-ICP-MS zircon U-Pb age of two granodiorite-porphyries are respectively(99.5±1.4)Ma and(102.3±1.5)Ma,Which are the products of magma activity in the early Cretaceous Period.Major elements are characterized by high silicon,rich alkali and rich calcium.They belong to calc-alkaline metaluminous series,bearing the characteristics of I-type granite.Rare earth elements have right type of distribution pattern with slightly negative Eu abnormality,the∑REE is 150.63×10-6-192.13×10-6 andδEu is 0.73-0.85.The trace elements are enriched in Rb,U,Th,La,Ce which are large ion lithophile elements(LILE)and lacked of Nb,Ta,Ti,P which are high field strength elements(HFS).For Dali granite,its initial Sr ratio is 0.7076-0.7078,the value of ~(147)Sm/~(144)Nd is 0.0960-0.1055,the value of(~(143)Nd/~(144)Nd)iis 0.5122-0.5123,the value ofεNd(t)is-5.29--3.55,and the model age(T1 DM)is(0.98-1.12)Ga;its value of ~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb after correction are respectively 18.0745-18.2316,15.6241-15.664,38.4129-38.5852.The above characteristics of the Sr-Nd-Pb isotope show that the lithogenous materials of Dali granite pluton come from the partial molten complex of the upper crust.In the tectonic environment discrimination diagram,Dali granite pluton was formed in a tectonic environment of collision,which may have some relation with the collision of paleo-Pacific plate in the late Yanshanian period.
The lithologica characters of Dali granite pluton in the Dayaoshan metallogenic belt mainly include granodiorite,granodiortie-porphyry,monzonitic granite and monzonitic granite porphyry,which intrusive into the Huangdongkou group in Cambrian system.The results of LA-ICP-MS zircon U-Pb age of two granodiorite-porphyries are respectively(99.5±1.4)Ma and(102.3±1.5)Ma,Which are the products of magma activity in the early Cretaceous Period.Major elements are characterized by high silicon,rich alkali and rich calcium.They belong to calc-alkaline metaluminous series,bearing the characteristics of I-type granite.Rare earth elements have right type of distribution pattern with slightly negative Eu abnormality,the∑REE is 150.63×10-6-192.13×10-6 andδEu is 0.73-0.85.The trace elements are enriched in Rb,U,Th,La,Ce which are large ion lithophile elements(LILE)and lacked of Nb,Ta,Ti,P which are high field strength elements(HFS).For Dali granite,its initial Sr ratio is 0.7076-0.7078,the value of ~(147)Sm/~(144)Nd is 0.0960-0.1055,the value of(~(143)Nd/~(144)Nd)iis 0.5122-0.5123,the value ofεNd(t)is-5.29--3.55,and the model age(T1 DM)is(0.98-1.12)Ga;its value of ~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb after correction are respectively 18.0745-18.2316,15.6241-15.664,38.4129-38.5852.The above characteristics of the Sr-Nd-Pb isotope show that the lithogenous materials of Dali granite pluton come from the partial molten complex of the upper crust.In the tectonic environment discrimination diagram,Dali granite pluton was formed in a tectonic environment of collision,which may have some relation with the collision of paleo-Pacific plate in the late Yanshanian period.
引文
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[19]胡升奇,周国发,彭松柏,等.广西大黎铜钼矿石英二长(斑)岩年代学、地球化学特征及其地质意义[J].地球学报,2012,33(1):23-37.
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[22]任纪舜,牛宝贵,刘志刚.软碰撞、叠覆造山和多旋回缝合作用[J].地学前缘,1999,6(3):285-293.
[23]华仁民,陈培荣,张文兰,等.南岭与中生代花岗岩类有关的成矿作用及其大地构造背景[J].高校地质学报,2005,11(3):291-304.
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[25]万天丰.中国大地构造学纲要[M].北京:地质出版社,2004:152-162.
[26]王强,赵振华,简平,等.华南腹地白垩纪A型花岗岩类或碱性侵入岩年代学及其对华南晚中生代构造演化的制约[J].岩石学报,2005,21(3):795-808.
[2]钟立峰,夏斌,刘立文,等.粤西-桂东成矿带园珠顶铜钼矿床成矿年代学及其地质意义[J].矿床地质,2010,29(3):395-404.
[3]蔡明海,孟祥金,刘国庆.大瑶山金成矿带成矿时代研究[J].矿床地质,2002,21(增刊1):945-948.
[4]蔡明海,刘国庆,战明国.桂东大瑶山地区金矿床成因及成矿时代研究[J].华南地质与矿产,2000,10(3):58-63.
[5]崔彬,翟裕生,蒙义峰,等.广西大瑶山-西大明山金银成矿系统研究[J].地球科学,2000,25(4):352-355.
[6]胡楚雁.广西大瑶山隆起区不同金矿化类型的矿物标型特征[J].桂林工学院学报,1999,19(1):34-39.
[7]胡楚雁.桂东大瑶山隆起区地下水直接成矿类型金矿化特征、成矿条件分析及意义[J].桂林工学院学报,2000,20(3):220-224.
[8]雷良奇,宋慈安,赵东军.大瑶山隆起区西南缘MVT矿带含矿岩系及流体成矿[J].桂林工学院学报,2006,26(2):153-161.
[9]陈懋弘,莫次生,黄智忠,等.广西苍梧县社洞钨钼矿床花岗岩类锆石LA-ICP-MS和辉钼矿Re-Os年龄及其地质意义[J].矿床地质,2011,30(6):963-978.
[10]肖柳阳.广西昭平湾岛金矿地质特征与成矿机理[D].北京:中国地质大学,2014.
[11]谢永彬.广西大瑶山东段花岗岩类地球化学特征及其年代学研究[D].桂林:桂林理工大学,2014.
[12]王新宇,刘名朝,周国发,等.桂东大瑶山成矿带新坪矿区花岗斑岩与金多金属成矿作用关系[J].现代地质,2013,27(3):585-592.
[13]朱桂田,朱文风.广西大瑶山古里脑和龙头山金矿岩浆期后断裂成矿作用及找矿意义[J].矿产与地质,2006,20(3):214-218.
[14]陈富文,李华芹,梅玉萍.广西龙头山斑岩型金矿成岩成矿锆石SHRIMP U-Pb年代学研究[J].地质学报,2008,82(7):921-926.
[15]许华,黄炳诚,倪战旭,等.钦杭成矿带西段古龙花岗岩株群岩石学、地球化学及年代学[J].华南地质与矿产,2012,28(4):331-339.
[16]黄炳诚,许华,潘艺文,等.钦杭成矿带西段罗容杂岩体岩石学、地球化学及年代学[J].华南地质与矿产,2012,28(4):321-330.
[17]黄惠民,和志军,崔彬.广西大瑶山地区花岗岩成矿系列[J].地质与勘探,2003,39(4):12-16.
[18]周新民,孙涛,沈渭洲.华南中生代花岗岩-火山岩时空格局与成因模式[C]//南岭地区晚中生代花岗岩成因与岩石圈动力学演化.北京:科学出版社,2007:179-195.
[19]胡升奇,周国发,彭松柏,等.广西大黎铜钼矿石英二长(斑)岩年代学、地球化学特征及其地质意义[J].地球学报,2012,33(1):23-37.
[20]秦亚,张青伟,康志强,等.桂东大瑶山成矿带花岗岩类岩石年代学格架的厘定[J].吉林大学学报(地球科学版),2015,45(6):1735-1756.
[21]LIU Y S,GAO S,HU Z C,et al.Continental and oceanic crust recycling-induced melt-peridotite interactions in the transNorth China orogen:U-Pb dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J].Petrology,2009,51(1/2):537-571.
[22]任纪舜,牛宝贵,刘志刚.软碰撞、叠覆造山和多旋回缝合作用[J].地学前缘,1999,6(3):285-293.
[23]华仁民,陈培荣,张文兰,等.南岭与中生代花岗岩类有关的成矿作用及其大地构造背景[J].高校地质学报,2005,11(3):291-304.
[24]ZHOU X M,LI W X.Origin of late Mesozoic igneous rocks in Southeastern China:implications for lithosphere subduction and underplating of mafic magmas[J].Tectonophysics,2000,326(3/4):269-287.
[25]万天丰.中国大地构造学纲要[M].北京:地质出版社,2004:152-162.
[26]王强,赵振华,简平,等.华南腹地白垩纪A型花岗岩类或碱性侵入岩年代学及其对华南晚中生代构造演化的制约[J].岩石学报,2005,21(3):795-808.