诸广山南体乐洞花岗岩的地球化学特征与成因研究
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摘要
乐洞花岗岩位于诸广山岩体南部的北缘,其岩性主要为中粒二云母花岗岩。针对乐洞花岗岩的6件样品进行了岩石学、主量元素、微量元素、稀土元素和Sr,Nd同位素分析。主量元素方面,具有富硅(w(SiO_2)70.76%~71.90%,平均为71.63%)、富铝(A/CNK值0.97~1.14,平均为1.07)、钾大于钠(K_2O/Na_2O比值1.58~1.90,平均为1.75)等特征;富集大离子元素Rb,Th和亏损Ba,Sr,Nb,Ta,P,Ti等元素;ΣREE值(124.1×10~(-6)~244.9×10~(-6),平均值为170.3×10~(-6))较高,配分模式表现为明显的右倾型,Eu明显亏损(δEu值0.23~0.27,平均为0.25);具有低ε_(Nd)(t)值(-11.8)、较高[n(~(87)Sr)/n(~(86)Sr)]_i值(0.720 23)及古老Nd模式年龄(1 966Ma)的同位素特征;源区成分以泥质岩为主,砂质岩为次要组分。上述地球化学特征与南岭地区的S型花岗岩十分相似。指示乐洞花岗岩是在华南地块和印支地块碰撞形成的伸展构造环境中,古元古代地壳组分在减压、导水等因素的综合影响下,由变质沉积岩发生部分熔融而形成的,属于后碰撞花岗岩。
The main elements,trace elements,rare earth elements,Sr and Nd isotopes of 6samples from the Ledong middle grained monzonite in the southern granite pluton of Zhuguang Mountains are studied.It shows that the rock is rich in(w(SiO_2)70.76%~71.90%,average71.63%)and Al(A/CNK=0.97~1.14,average 1.07),with high ratio of K_2O/Na_2O(1.58~1.90,average 1.75).In the aspect of trace elements,the rock is enriched in large ion elements(Rb,Th)and depleted in Ba,Sr,Nb,Ta,P and Ti.The rare earth elements in the monzonite are significantly enriched(124.1×10~(-6)~244.9×10~(-6),average 170.3×10~(-6)),with right-declined distribution patterns,and with obvious negative Eu anormaly(δEu=0.23~0.27,average 0.25).A-nalysis of isotopes reveals that theε_(Nd)(t)value is low(-11.8),[n(~(87)Sr)/n(~(86)Sr)]_ivalue is high(0.720 23)and the Nd model age is 1 966Ma.Source region compositions are dominated by argillaceous rock with minor sandy rocks.These geochemical features consistently indicate that Ledong granite is resulted from partial melting of metamorphic sedimentary rocks in the Paleoproterozoic crust under the influence of decompression and water diversion,and in the extensional tectonic environment during the collision between the South China and Indo China block.
The main elements,trace elements,rare earth elements,Sr and Nd isotopes of 6samples from the Ledong middle grained monzonite in the southern granite pluton of Zhuguang Mountains are studied.It shows that the rock is rich in(w(SiO_2)70.76%~71.90%,average71.63%)and Al(A/CNK=0.97~1.14,average 1.07),with high ratio of K_2O/Na_2O(1.58~1.90,average 1.75).In the aspect of trace elements,the rock is enriched in large ion elements(Rb,Th)and depleted in Ba,Sr,Nb,Ta,P and Ti.The rare earth elements in the monzonite are significantly enriched(124.1×10~(-6)~244.9×10~(-6),average 170.3×10~(-6)),with right-declined distribution patterns,and with obvious negative Eu anormaly(δEu=0.23~0.27,average 0.25).A-nalysis of isotopes reveals that theε_(Nd)(t)value is low(-11.8),[n(~(87)Sr)/n(~(86)Sr)]_ivalue is high(0.720 23)and the Nd model age is 1 966Ma.Source region compositions are dominated by argillaceous rock with minor sandy rocks.These geochemical features consistently indicate that Ledong granite is resulted from partial melting of metamorphic sedimentary rocks in the Paleoproterozoic crust under the influence of decompression and water diversion,and in the extensional tectonic environment during the collision between the South China and Indo China block.
引文
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[14]Maniar P D,Piccoli P M.Tectonic discrimination of granitoids[J].Geol Soc Amer Bull,1989,101:635-643.
[15]徐克勤,孙鼐,王德滋,等.华南花岗岩成因与成矿[A].见:徐克勤,涂光炽.花岗岩地质与成矿关系[C].南京:江苏科学技术出版,1984.
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[19]高山,骆庭川,张本仁,等.中国东部地壳的结构和组成[J].中国科学(D辑),1999,29(3):204-213.
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[25]Maniar P D,Piccoli P M.Tectonic discrimination of granitoids[J].Geol Soc Amer Bull,1989,101:635-643.
[26]李继亮,孙枢,郝杰,等.论碰撞造山带的分类[J].地质科学,1999(02):4-13.
[27]金文山,赵风清,王祖伟,等.湘黔桂雪峰期地层单元岩石地球化学特征[J].湖南地质,1997(02):10-16+23.
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[29]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.
[30]王岳军,廖超林,范蔚茗,等.赣中地区早中生代OIB碱性玄武岩的厘定及构造意义[J].地球化学,2004,33:109-117.
[31]王强,赵振华,简平,等.武夷山洋坊霓辉石正长岩的锆石SHRIMP U-Pb年龄及其构造意义[J].科学通报,2003(14):1 582-1 588.
[32]Liegeois J P,Naves J,Hertogen J.Contrasting origin of post-collisional high-K calc-alkaline and shoshonitic versus alkaline and peralkaline granitoids.The use of Sliding normalization[J].Lithos,1998,45:1-28.
[33]王岳军,范蔚茗,梁新权,等.湖南印支期花岗岩SHRIMP锆石U-Pb年龄及其成因启示[J].科学通报,2005(12):1 259-1 266.
[34]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(04):426-432.
[35]张敏,陈培荣,黄国龙,等.南岭东段龙源坝复式岩体La-ICP-MS锆石U-Pb年龄及其地质意义[J].地质学报,2006(07):984-994.
[36]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探讨[J].地质学报,2004(03):352-358.
[37]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(10):2 493-2 508.
[38]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(06):1 441-1 456.
[39]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.
[2]朱捌,邓平,凌洪飞,等.粤北红山岩体形成时代及成因研究[J].铀矿地质,2009,25(6):321-329.
[3]黄国龙,曹豪杰,凌洪飞,等.粤北油洞岩体SHRIMP锆石U-Pb年龄、地球化学特征及其成因研究[J].地质学报,2012,86(4):577-586.
[4]黄国龙,刘鑫扬,孙立强,等.粤北长江岩体的锆石U-Pb定年、地球化学特征及其成因研究[J].地质学报,2014,88(5):836-849.
[5]邓平,任纪舜,凌洪飞,等.诸广山南体燕山期花岗岩的锆石SHRIMP U-Pb年龄及其构造意义[J].地质论评,2011,57(6):881-888.
[6]邓平,任纪舜,凌洪飞,等.诸广山南体印支期花岗岩的锆石SHRIMP U-Pb年龄及其构造意义[J].科学通报,2012,57(14):1 231-1 241.
[7]张敏,陈培荣,陈卫峰,等.粤北地区产铀岩体的铀矿化特征及其成矿机制探讨[J].化工矿产地质,2006,28(1):9-14.
[8]钟福军,潘家永,夏菲,等.粤北长江铀矿田成矿过程中稀土元素地球化学特征[J].矿物岩石,2017,37(02):63-73.
[9]阮昆,吴星根,龙自强,等.粤北塘湾地区燕山晚期小岩体地球化学特征与铀成矿探讨[J].矿物岩石,2017,37(03):38-45.
[10]周航兵,潘家永,钟福军,等.粤北长江铀矿田细粒黑云母花岗岩的成因及其与铀成矿关系[J].矿物岩石,2018,38(01):10-19.
[11]陈小明,王汝成,刘昌实,等.广东从化佛冈(主体)黑云母花岗岩定年和成因[J].高校地质学报,2002,8(3):293-307.
[12]Middlemost E A K.Naming materials in the3magmas/igneous rock system[J].Earth Sci Rev,1994,37:215-224.
[13]Peccerillo A,Taylor S R.Geochemistry of Eocene calc-alkaline volcanic rocks of the Kastamonu area,northern Turkey[J].Contrib Mineral Petrol,1976,58:63-81.
[14]Maniar P D,Piccoli P M.Tectonic discrimination of granitoids[J].Geol Soc Amer Bull,1989,101:635-643.
[15]徐克勤,孙鼐,王德滋,等.华南花岗岩成因与成矿[A].见:徐克勤,涂光炽.花岗岩地质与成矿关系[C].南京:江苏科学技术出版,1984.
[16]Green T H.Significance of Nb/Ta as an indicator of geochemical processes in the crust-mantle system[J].Chem Geol,1995,120:347-359.
[17]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.
[18]Irber W.The lanthanide tetrad effect and its correlation with K/Rb,Eu/Eu*,Sr/Eu,Y/Ho,and Zr/Hf of evolving peraluminous granite suites[J].Geochim Cosmochim Acta,1999,63:489-508.
[19]高山,骆庭川,张本仁,等.中国东部地壳的结构和组成[J].中国科学(D辑),1999,29(3):204-213.
[20]Taylor S R,McLennan S M.The geochemical evolution of the continental crust[J].Rev Geophys,1995,33:241-265.
[21]Pearce J A.Role of the sub-continental lithosphere in magma genesis at active continental margins[A].In:Hawkesworth C J and Norry MJ(eds.).Continental basalts and mantle xenoliths[C].Nantwich:Shiva,1983.
[22]Taylor S R,McLennan S M.The continental crust:its composition and evolution[D].Oxford:Blackwell,1985.
[23]Sylvester P J.Post-collisional strongly peraluminous granites[J].Lithos,1998,45:29-44.
[24]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,2000,50:51-73.
[25]Maniar P D,Piccoli P M.Tectonic discrimination of granitoids[J].Geol Soc Amer Bull,1989,101:635-643.
[26]李继亮,孙枢,郝杰,等.论碰撞造山带的分类[J].地质科学,1999(02):4-13.
[27]金文山,赵风清,王祖伟,等.湘黔桂雪峰期地层单元岩石地球化学特征[J].湖南地质,1997(02):10-16+23.
[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),1998,28(增刊):7-14.
[29]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.
[30]王岳军,廖超林,范蔚茗,等.赣中地区早中生代OIB碱性玄武岩的厘定及构造意义[J].地球化学,2004,33:109-117.
[31]王强,赵振华,简平,等.武夷山洋坊霓辉石正长岩的锆石SHRIMP U-Pb年龄及其构造意义[J].科学通报,2003(14):1 582-1 588.
[32]Liegeois J P,Naves J,Hertogen J.Contrasting origin of post-collisional high-K calc-alkaline and shoshonitic versus alkaline and peralkaline granitoids.The use of Sliding normalization[J].Lithos,1998,45:1-28.
[33]王岳军,范蔚茗,梁新权,等.湖南印支期花岗岩SHRIMP锆石U-Pb年龄及其成因启示[J].科学通报,2005(12):1 259-1 266.
[34]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(04):426-432.
[35]张敏,陈培荣,黄国龙,等.南岭东段龙源坝复式岩体La-ICP-MS锆石U-Pb年龄及其地质意义[J].地质学报,2006(07):984-994.
[36]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探讨[J].地质学报,2004(03):352-358.
[37]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(10):2 493-2 508.
[38]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(06):1 441-1 456.
[39]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.