青海南山吾口侵入岩体锆石U-Pb年代学、地球化学特征及其地质意义
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摘要
本文对青海南山吾口正长花岗岩和花岗闪长岩进行了岩石学、岩石地球化学及年代学研究。首次测得吾口侵入岩体正长花岗岩的锆石206Pb/238U年龄为253. 8±3. 3Ma(MSWD=0. 96),形成时代为晚二叠世。岩石中Al_2O_3为(14. 13～16. 51)×10~(-2),K_2O为(1. 66～3. 59)×10~(-2),A/NK=1. 15～2. 35,A/CNK=0. 75～1. 03,TFe O/(TFe O+MgO)=0. 53～0. 81,岩石具偏铝质中-高钾钙碱性花岗岩特征;吾口岩体表现为富集大离子亲石元素Rb、K等,亏损高场强元素Nb、Ta、Ba等;轻重稀土分异较明显,具右倾特征,中等负Eu异常(δEu=0. 44～0. 68),具壳幔岩浆混合特征。吾口岩体代表了阿尼玛卿洋盆向北削减俯冲运动在青海南山构造带与西秦岭造山带和南祁连造山带的构造转换衔接部位的构造演化的地质记录。该侵入岩体形成时代及构造环境的确定,为研究印支早期青海南山构造演化及动力学机制提供重要依据。
The present paper deals in detail with the petrology,geochemistry and La-ICP-MS zircon U-Pb chronology of the syenogranite and granodiorite from the Wukou region in the Qinghainanshan area,Qinghai. The syenogranite from the Wukou region gives a zircon206Pb/238 U age of 253. 8 ± 3. 3 Ma( MSWD = 0. 96),which may be traced back to the Late Permian. Al_2O_3=( 14. 13-16. 51) × 10~(-2),K_2 O =( 1. 66-3. 59) × 10~(-2),A/NK = 1. 15-2. 35,A/CNK = 0. 75-1. 03,and TFeO/( TFeO + MgO) = 0. 53-0. 81,all of which are characteristic of metaluminous medium to high-K calc-alkaline granites. Both the syenogranite and granodiorite are enriched in large ion lithophile elements Rb and K,and depleted in high field strength elements Nb,Ta and Ba,noticeably differentiated in light and heavy rare earth elements with right-leaning REE distribution patterns,and moderately negative Eu anomalies( Eu = 0. 44-0. 68),indicating that the intrusive rocks in this area have the origins of the mixting of the crust and mantle magmas. This phase of magmatic thermal event represents the geological records of the tectonic transition between the western Qinling orogenic zone and the southern Qilian orogenic zone in the Qinghainanshan tectonic zone against the background of the northward subduction of the A'nyemaqen oceanic basin during the Late Permian. The timing of the intrusive rocks and determination of the tectonic settings may provide important evidence for the study of the tectonic evolution and dynamic mechanisms of the Qinghainanshan area during the early Indosinian.
The present paper deals in detail with the petrology,geochemistry and La-ICP-MS zircon U-Pb chronology of the syenogranite and granodiorite from the Wukou region in the Qinghainanshan area,Qinghai. The syenogranite from the Wukou region gives a zircon206Pb/238 U age of 253. 8 ± 3. 3 Ma( MSWD = 0. 96),which may be traced back to the Late Permian. Al_2O_3=( 14. 13-16. 51) × 10~(-2),K_2 O =( 1. 66-3. 59) × 10~(-2),A/NK = 1. 15-2. 35,A/CNK = 0. 75-1. 03,and TFeO/( TFeO + MgO) = 0. 53-0. 81,all of which are characteristic of metaluminous medium to high-K calc-alkaline granites. Both the syenogranite and granodiorite are enriched in large ion lithophile elements Rb and K,and depleted in high field strength elements Nb,Ta and Ba,noticeably differentiated in light and heavy rare earth elements with right-leaning REE distribution patterns,and moderately negative Eu anomalies( Eu = 0. 44-0. 68),indicating that the intrusive rocks in this area have the origins of the mixting of the crust and mantle magmas. This phase of magmatic thermal event represents the geological records of the tectonic transition between the western Qinling orogenic zone and the southern Qilian orogenic zone in the Qinghainanshan tectonic zone against the background of the northward subduction of the A'nyemaqen oceanic basin during the Late Permian. The timing of the intrusive rocks and determination of the tectonic settings may provide important evidence for the study of the tectonic evolution and dynamic mechanisms of the Qinghainanshan area during the early Indosinian.
引文
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[14]袁道阳,张培震,雷中生,等.青海拉脊山断裂带新活动特征的初步研究[J].中国地震,2005,21(1):93-102.
[15] Liu Y,Hu Z,Gao S,et al. In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J]. Chemical Geology,2008,257(1-2):34-43.
[16] Liu Y S,Hu Z C,Zong K Q,et al. Reappraisement and refinement of zircon U-Pb isotope and trace element analyses by LA-ICP-MS[J]. Chinese Science Bulletin,2010,55(15):1535-1546.
[17] Liu Y,Gao S,Hu Z,et al. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb Dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J]. Journal of Petrology,2010,51(51):392-9.
[18]周红英,李惠民. U-Pb同位素定年技术及其地质应用潜力[J].地质调查与研究,2011,31(1):63-70.
[19]崔玉荣,周红英,耿建珍,等. LA-MC-ICP-MS独居石微区原位U-Pb同位素年龄测定[J].地球学报,2012,33(6):865-876.
[20]陈文,万渝生,李华芹,等.同位素地质年龄测定技术及应用[J].地质学报,2011,85(11):1918-1947.
[21]邱家骧.岩浆岩岩石学[M].北京:地质出版社,1985. 34-42.
[22]邱家骧,林景仟.岩石化学[M].北京:地质出版社,1991. 65-70.
[23] Irvine T N,Baragar A. A guide to the chemical classification of the common volcanic rocks[J]. Canadian Journal of Earth Sciences,1971,8(5):523-548.
[24] Rudnick R L,Gao S. Composition of the continental crust[A].Rudnick R L. Treatise on Geochemistry[C]. Oxford:Elsevier Pergamon,2003. 1-64.
[25]李昌年.火成岩微量元素岩石学[M].武汉:中国地质大学出版社,1992. 1-113.
[26] Sun S S,Mcdonough W F. Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J]. Geological Society London Special Publications,1989,42(1):313-345.
[27]高秉璋,洪大卫,郑基俭,等.花岗岩地区1∶5万区域地质填图方法指南[M].武汉:中国地质大学出版社,1991. 20-37.
[28]赵振华.关于微量元素构造环境判别图解使用的有关问题[J].大地构造与成矿学,2007,31(1):92-103.
[29]徐久磊,郑常青,施璐,等.大兴安岭北段雅尔根楚I型花岗岩年代学、岩石地球化学及其地球动力学意义[J].地质学报,2013,87(9):1312-1323.
[30] Wolf M B,Wyllie P J. Dehydration-melting of amphibolite at10kbar:The effects of temperature and time[J]. Contributions to Mineralogy and Petrology,1994,115(4):369-383.
[31]吴福元,李献华,杨进辉,等.花岗岩成因研究的若干问题[J].岩石学报,2007,23(6):1217-1238.
[32]郑永飞,杨进辉,宋述光,等.化学地球动力学研究进展[J].矿物岩石地球化学通报,2013,2(1):1-24.
[33]肖庆辉,邓晋福,马大铨,等.花岗岩研究思维与方法[M].北京:地质出版社,2002. 1-50.
[34] Wang K,Chung S,O'Reilly S Y,et al. Geochemical Constraints for the genesis of post-collisional magmatism and the geodynamic evolution of the Northern Taiwan Region[J]. Journal of Petrology,2004,45(5):975-1011.
[35] Rudnick R L,Fountain D M. Nature and composition of the continental crust:A lower crustal perspective[J]. Reviews of Geophysics,1995,33(3):267-309.
[36]邓晋福,吴宗絮,杨建军,等.格尔木—额济纳旗地学断面走廊域地壳—上地幔岩石学结构与深部过程[J].地球物理学报,1995,38(增刊Ⅱ):130-144.
[37]张永明,裴先治,李佐臣,等.青海南山当家寺花岗岩体锆石U-Pb年代学、地球化学及其地质意义[J].地质学报,2017,91(3):523-541.
[38]张成立,王涛,王晓霞.秦岭造山带早中生代花岗岩成因及其构造环境[J].高校地质学报,2008,14(3):304-316.
[39]李婷,徐学义,陈隽璐,等.西秦岭造山带礼县地区中川岩体LA-ICP-MS锆石U-Pb定年及其构造环境[J].地质通报,2012,31(6):875-882.
[40]张旗,潘国强,李承东,等.花岗岩构造环境问题:关于花岗岩研究的思考之三[J].岩石学报,2007,23(7):829-844.
[41]倪志耀,卫管一.地壳重熔型花岗岩形成的源岩、构造及物化条件的制约[J].西北地质,1996,17(1):6-11.
[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,1984,25:956-983.
[2]张雪亭,杨生德,王秉璋,等.青海省板块构造研究[M].北京:地质出版社,2007.
[3]张国伟,郭安林,姚安平.中国大陆构造中的西秦岭—松潘大陆构造结[J].地学前缘,2004,11(3):23-32.
[4]张永明,裴先治,李佐臣,等.青海南山沟后岩浆杂岩体锆石U-Pb年代学、岩石成因及其地质意义[J].大地构造与成矿学,2017,41(5):908-932.
[5]陈宏伟,罗照华,莫宣学,等.东昆仑造山带三叠纪岩浆混合成因花岗岩的岩浆底侵作用机制[J].中国地质,2005,32:386-395.
[6]张宏飞,陈岳龙,徐旺春,等.青海共和盆地周缘印支期花岗岩类的成因及其构造意义[J].岩石学报,2006,22(12):2910-2922.
[7]张永明,裴先治,李佐臣,等.青海南山当家寺花岗岩体锆石U—Pb年代学、地球化学及其地质意义[J].地质学报,2017,91(3):523-541.
[8]李生虎,石玉莲,田滔,等.青海南山早三叠世石英闪长岩地球化学特征、LA-ICP-MS定年及地质意义[J].青海大学学报:自然科学版,2017,35(3):25-32.
[9]拜永山,王秉璋,王永文,等. J47C003004(门源县)幅、J47C004004(西宁市)幅1∶25万数字区域地质调查报告[R],2007.
[10]许志琴,杨经绥.阿尼玛卿缝合带及"俯冲-碰撞"动力学[C].蛇绿岩与地球动力学研讨会. 1996.
[11]张刚.东昆仑造山带东段哈拉尕吐花岗岩体地质特征、形成时代及地质意义[D].西安:长安大学,2012.
[12]陈功,裴先治,李佐臣,等.东昆仑东段巴隆地区朝火鹿陶勒盖花岗闪长岩体锆石U-Pb年龄、地球化学及其地质意义[J].地质通报,2016,35(12):1990-2005.
[13]王二七,张旗,Clark B. Burchfiel.青海拉鸡山:一个多阶段抬升的构造窗[J].地质科学,2000,(4):493-500.
[14]袁道阳,张培震,雷中生,等.青海拉脊山断裂带新活动特征的初步研究[J].中国地震,2005,21(1):93-102.
[15] Liu Y,Hu Z,Gao S,et al. In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J]. Chemical Geology,2008,257(1-2):34-43.
[16] Liu Y S,Hu Z C,Zong K Q,et al. Reappraisement and refinement of zircon U-Pb isotope and trace element analyses by LA-ICP-MS[J]. Chinese Science Bulletin,2010,55(15):1535-1546.
[17] Liu Y,Gao S,Hu Z,et al. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb Dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J]. Journal of Petrology,2010,51(51):392-9.
[18]周红英,李惠民. U-Pb同位素定年技术及其地质应用潜力[J].地质调查与研究,2011,31(1):63-70.
[19]崔玉荣,周红英,耿建珍,等. LA-MC-ICP-MS独居石微区原位U-Pb同位素年龄测定[J].地球学报,2012,33(6):865-876.
[20]陈文,万渝生,李华芹,等.同位素地质年龄测定技术及应用[J].地质学报,2011,85(11):1918-1947.
[21]邱家骧.岩浆岩岩石学[M].北京:地质出版社,1985. 34-42.
[22]邱家骧,林景仟.岩石化学[M].北京:地质出版社,1991. 65-70.
[23] Irvine T N,Baragar A. A guide to the chemical classification of the common volcanic rocks[J]. Canadian Journal of Earth Sciences,1971,8(5):523-548.
[24] Rudnick R L,Gao S. Composition of the continental crust[A].Rudnick R L. Treatise on Geochemistry[C]. Oxford:Elsevier Pergamon,2003. 1-64.
[25]李昌年.火成岩微量元素岩石学[M].武汉:中国地质大学出版社,1992. 1-113.
[26] Sun S S,Mcdonough W F. Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J]. Geological Society London Special Publications,1989,42(1):313-345.
[27]高秉璋,洪大卫,郑基俭,等.花岗岩地区1∶5万区域地质填图方法指南[M].武汉:中国地质大学出版社,1991. 20-37.
[28]赵振华.关于微量元素构造环境判别图解使用的有关问题[J].大地构造与成矿学,2007,31(1):92-103.
[29]徐久磊,郑常青,施璐,等.大兴安岭北段雅尔根楚I型花岗岩年代学、岩石地球化学及其地球动力学意义[J].地质学报,2013,87(9):1312-1323.
[30] Wolf M B,Wyllie P J. Dehydration-melting of amphibolite at10kbar:The effects of temperature and time[J]. Contributions to Mineralogy and Petrology,1994,115(4):369-383.
[31]吴福元,李献华,杨进辉,等.花岗岩成因研究的若干问题[J].岩石学报,2007,23(6):1217-1238.
[32]郑永飞,杨进辉,宋述光,等.化学地球动力学研究进展[J].矿物岩石地球化学通报,2013,2(1):1-24.
[33]肖庆辉,邓晋福,马大铨,等.花岗岩研究思维与方法[M].北京:地质出版社,2002. 1-50.
[34] Wang K,Chung S,O'Reilly S Y,et al. Geochemical Constraints for the genesis of post-collisional magmatism and the geodynamic evolution of the Northern Taiwan Region[J]. Journal of Petrology,2004,45(5):975-1011.
[35] Rudnick R L,Fountain D M. Nature and composition of the continental crust:A lower crustal perspective[J]. Reviews of Geophysics,1995,33(3):267-309.
[36]邓晋福,吴宗絮,杨建军,等.格尔木—额济纳旗地学断面走廊域地壳—上地幔岩石学结构与深部过程[J].地球物理学报,1995,38(增刊Ⅱ):130-144.
[37]张永明,裴先治,李佐臣,等.青海南山当家寺花岗岩体锆石U-Pb年代学、地球化学及其地质意义[J].地质学报,2017,91(3):523-541.
[38]张成立,王涛,王晓霞.秦岭造山带早中生代花岗岩成因及其构造环境[J].高校地质学报,2008,14(3):304-316.
[39]李婷,徐学义,陈隽璐,等.西秦岭造山带礼县地区中川岩体LA-ICP-MS锆石U-Pb定年及其构造环境[J].地质通报,2012,31(6):875-882.
[40]张旗,潘国强,李承东,等.花岗岩构造环境问题:关于花岗岩研究的思考之三[J].岩石学报,2007,23(7):829-844.
[41]倪志耀,卫管一.地壳重熔型花岗岩形成的源岩、构造及物化条件的制约[J].西北地质,1996,17(1):6-11.
[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,1984,25:956-983.