扬子地台西南缘朱家坝辉绿岩地球化学特征及其地质意义
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摘要
近年来在扬子西缘大量的早—中元古代岩浆岩证据显示扬子地台内形成的断陷盆地及早中元古代岩浆岩与全球性的Columbia超大陆裂解事件有着密不可分的联系。这种联系主要表现在区内早中元古代的岩浆岩地球化学特征上。为了探讨武定裂陷槽朱家坝辉绿岩的地球化学特征及其意义,以12块朱家坝辉绿岩的地球化学分析数据为基础,在分析了其主微量和稀土元素的特征之后发现朱家坝辉绿岩w(SiO_2)为44.16%～48.08%,w(K_2O+Na_2O)为3.54%～4.26%,在化学成分上属于钙碱性岩石;其稀土元素的总量为183.1×10~(-6)～206.91×10~(-6),LREE/HREE=1.44～1.96,表明在其形成过程中发生了明显的地壳混然或者是岩浆分异作用,其化学成分基本可以反映出岩浆源区的化学组成特征。基于此,对朱家坝辉绿岩进行了源区性质、构造环境和可能的成因机制探讨,认为朱家坝辉绿岩形成于拉张环境之中,很有可能是在昆阳裂谷形成初期形成,其岩浆来源于较富集的地幔源区,形成过程中几乎没有地壳物质参与。
The geochemical characteristics of early-middle Proterozoic igneous rocks in the west margin of Yangtze platform shows that the magmatic activity is closely related to the global Columbia supercontinent splitting event.12 diabase samples at Zhujiaba area of Wuding rift trough are collected and the characteristics of major trace elements and rare earth elements are analyzed and studied.It shows that the w(SiO_2) content of Zhujiaba diabase is 44.16%～48.08%,w(K_2O+Na_2O) is 3.54%～4.26%.Total amount of REE is 183.1×10~(-6)～206.91×10~(-6),LREE/HREE=1.44～1.96.Based on the geometrical characteristics,the Zhujiaba diabase is discussed in terms of its source area property,tectonic environment and possible genetic mechanism.It is considered that the Zhujiaba diabase is formed in the extensional environment and probably in the early stage during the formation of Kunyang rift.The magma is originated from the enriched mantle source area and almost no crustal material is involved in the formation process.
The geochemical characteristics of early-middle Proterozoic igneous rocks in the west margin of Yangtze platform shows that the magmatic activity is closely related to the global Columbia supercontinent splitting event.12 diabase samples at Zhujiaba area of Wuding rift trough are collected and the characteristics of major trace elements and rare earth elements are analyzed and studied.It shows that the w(SiO_2) content of Zhujiaba diabase is 44.16%～48.08%,w(K_2O+Na_2O) is 3.54%～4.26%.Total amount of REE is 183.1×10~(-6)～206.91×10~(-6),LREE/HREE=1.44～1.96.Based on the geometrical characteristics,the Zhujiaba diabase is discussed in terms of its source area property,tectonic environment and possible genetic mechanism.It is considered that the Zhujiaba diabase is formed in the extensional environment and probably in the early stage during the formation of Kunyang rift.The magma is originated from the enriched mantle source area and almost no crustal material is involved in the formation process.
引文
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[23] 王生伟,蒋小芳,杨波,等.康滇地区元古宙构造运动Ⅰ:昆阳陆内裂谷、地幔柱及其成矿作用[J].地质论评,2016,62(6):1 353-1 377.
[24] 夏林圻,夏祖春,徐学义,等.利用地球化学方法判别大陆玄武岩和岛弧玄武岩[J].岩石矿物学杂志,2007,26(1):77-89.
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[27] Zou H,Zindler A,Xu X, et al.Major,trace element,and Nd,Sr and Pb isotope studies of Cenozoic basalts in SE China:mantle sources,regional variations,and tectonic significance[J].Chemical Geology,2000,171(1):33-47.
[28] 郭阳,王生伟,孙晓明,等.扬子地台西南缘古元古代末的裂解事件——来自武定地区辉绿岩锆石U-Pb年龄和地球化学证据[J].地质学报,2014,88(9):1 651-1 665.
[29] Mingram B,Trumbull RB,Littman S, et al.A Petrogenetic study of anorogenic felsic magmatism in the Cretaceous Paresis ring complex,Namibia:Evidence for mixing of crust and mantle derived components[J].Lithos,2000,54(1-2):1-22.
[30] Neal C R,Mahoney J J,Chazey W J.Mantle Sources and the Highly Variable Role of Continental Lithosphere in Basalt Petrogenesis of the Kerguelen Plateau and Broken Ridge LIP:Results from ODP Leg 183[J].Journal of Petrology,2002,43(7):1 177-1 205.
[31] 朱弟成,潘桂棠,莫宣学,等.青藏高原中部中生代OIB型玄武岩的识别:年代学、地球化学及其构造环境[J].地质学报,2006,80(9):1 312-1 328.
[2] Zhao X F,Zhou M F,Li J W, et al.Late Paleoproterozoic to early Mesoproterozoic Dong Chuan Group in Yunnan,SW China:Implications for tectonic evolution of the Yangtze Block[J].Precambrian Research,2010,182(1-2):57-69.
[3] Zhao X F,Zhou M F,Hitzman M W, et al.Late Paleoproterozoic to Early Mesporterozoic Tangdan Sedimentary Rock-Hosted Stratabound Copper Deposit,Yunnan Province,Southwest China[J].Econ Geol,2012,107:357-375.
[4] Greentree M R,Li Z X.The oldest known rocks in south-western China:SHRIMP U-Pb magmatic crystallisation age and detrital provenance analysis of the Paleoproterozoic Dahongshan Group[J].Journal of Asian Earth Sciences,2008,33(5-6):289-302.
[5] 王冬兵,尹福光,孙志明等.扬子陆块西缘古元古代基性侵入岩LA-ICP-MS锆石U-Pb年龄和Hf同位素及其地质意义[J].地质通报,2013,32(4):617-630.
[6] 尹福光,王冬兵,孙志明,等.哥伦比亚超大陆在扬子陆块西缘的探秘[J].沉积与特提斯地质,2012,32(3):31-40.
[7] 杨斌,周邦国,郭阳,等.云南东川奚家坪玄武岩的地球化学特征、成因及其地质意义[J].矿物岩石,2012,32(2):74-80.
[8] 杨斌,王伟清,董国臣,等.扬子地台西南缘康滇断隆带海孜双峰式侵入岩体年代学、地球化学及其地质意义[J].岩石学报,2015,31(5):1 361-1 373.
[9] 凌文黎,高山,郑海飞,等.扬子克拉通黄陵地区崆岭杂岩Sm-Nd同位素地质年代学研究[J].科学通报,1998,43(1):86.
[10] Qiu Y M,Gao S,McNaughton N J, et al.First evidence of ≥3.2 Ga continental crust in the Yangtze craton of South China and its implications for Archean crustal evolution and Phanerozoic tectonics[J].Geology,2000,28:11-14.
[11] 高山,Yumin QIU,凌文黎.崆岭高级变质地体单颗粒锆石SHRIMP U-Pb年代学研究——扬子克拉通>3.2 Ga陆壳物质的发现[J].中国科学:地球科学,2001,31(1):27-35.
[12] 任光明,庞维华,孙志明,等.扬子西缘会理地区通安组角闪岩锆石U-Pb定年及其地质意义[J].矿物岩石,2014,34(2):33-39.
[13] 庞维华,任光明,孙志明,等.扬子地块西缘古-中元古代地层划分对比研究:来自通安组火山岩锆石U-Pb年龄的证据[J].中国地质,2015,42(4):921-936.
[14] 杨斌,董国臣,郭阳,等.扬子地台西南缘大竹棚流纹岩的年代学、地球化学特征及其地质意义[J].矿物岩石,2016,36(2):82-91.
[15] 杨崇辉,杜利林,任留东,等.华北克拉通南缘安沟群的SHRIMP年龄及地层对比[J].岩石学报,2009,25(8):121-130.
[16] 尹福光,孙志明,任光明,等.上扬子陆块西南缘早一中元古代造山运动的地质记录[J].地质学报,2012,86(12):1 917-1 932.
[17] 王生伟,廖震文,孙晓明,等.云南东川铜矿区古元古代辉绿岩地球化学——Columbia超级大陆裂解在扬子陆块西南缘的响应[J].地质学报,2013,87(12):1 834-1 852.
[18] 王生伟,廖震文,孙晓明,等.会东菜园子花岗岩的年龄、地球化学——扬子地台西缘格林威尔造山运动的机制探讨[J].地质学报,2013,87(1):55-70.
[19] 王子正,郭阳,杨斌,等.扬子克拉通西缘1.73 Ga非造山型花岗斑岩的发现及其地质意义[J].地质学报,2013,87(7):931-942.
[20] 李怀坤,张传林,相振群,等.扬子克拉通神农架群锆石和斜锆石U-Pb年代学及其构造意义[J].岩石学报,2013,29(2):673-697.
[21] 王生伟,孙晓明,蒋小芳,等.东川铜矿原生黄铜矿的Re-Os年龄及其成矿背景[J].矿床地质,2012,(s1):609-610.
[22] 周家云,毛景文,刘飞燕,等.扬子地台西缘河口群钠长岩锆石SHRIMP年龄及岩石地球化学特征[J].矿物岩石,2011,31(3):66-73.
[23] 王生伟,蒋小芳,杨波,等.康滇地区元古宙构造运动Ⅰ:昆阳陆内裂谷、地幔柱及其成矿作用[J].地质论评,2016,62(6):1 353-1 377.
[24] 夏林圻,夏祖春,徐学义,等.利用地球化学方法判别大陆玄武岩和岛弧玄武岩[J].岩石矿物学杂志,2007,26(1):77-89.
[25] Han Y J,Stucky G D,Butler A.Mesoporous silicate sequestration and release of proteins [J].Journal of the American Chemical Society,1999,121(42):9 897-9 898.
[26] Riley T R,Leat P T,Pankhurst R J, et al.Origins of large volume rhyolitic volcanism in the Antarctic Peninsula and Patagonia by crustal melting[J].Journal of Petrology,2001,42(6):1 043-1 065.
[27] Zou H,Zindler A,Xu X, et al.Major,trace element,and Nd,Sr and Pb isotope studies of Cenozoic basalts in SE China:mantle sources,regional variations,and tectonic significance[J].Chemical Geology,2000,171(1):33-47.
[28] 郭阳,王生伟,孙晓明,等.扬子地台西南缘古元古代末的裂解事件——来自武定地区辉绿岩锆石U-Pb年龄和地球化学证据[J].地质学报,2014,88(9):1 651-1 665.
[29] Mingram B,Trumbull RB,Littman S, et al.A Petrogenetic study of anorogenic felsic magmatism in the Cretaceous Paresis ring complex,Namibia:Evidence for mixing of crust and mantle derived components[J].Lithos,2000,54(1-2):1-22.
[30] Neal C R,Mahoney J J,Chazey W J.Mantle Sources and the Highly Variable Role of Continental Lithosphere in Basalt Petrogenesis of the Kerguelen Plateau and Broken Ridge LIP:Results from ODP Leg 183[J].Journal of Petrology,2002,43(7):1 177-1 205.
[31] 朱弟成,潘桂棠,莫宣学,等.青藏高原中部中生代OIB型玄武岩的识别:年代学、地球化学及其构造环境[J].地质学报,2006,80(9):1 312-1 328.
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