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赞比亚索卢韦齐地区新元古代石英二长岩的成因:年代学、地球化学和Sr–Nd–Hf同位素约束

许康康, 孙凯, 吴兴源

许康康, 孙凯, 吴兴源. 赞比亚索卢韦齐地区新元古代石英二长岩的成因:年代学、地球化学和Sr–Nd–Hf同位素约束[J]. 西北地质, 2023, 56(5): 20-34. DOI: 10.12401/j.nwg.2023116
引用本文: 许康康, 孙凯, 吴兴源. 赞比亚索卢韦齐地区新元古代石英二长岩的成因:年代学、地球化学和Sr–Nd–Hf同位素约束[J]. 西北地质, 2023, 56(5): 20-34. DOI: 10.12401/j.nwg.2023116
XU Kangkang, SUN Kai, WU Xingyuan. Petrogenesis of Neoproterozoic Quartz Monzonite in Solwezi Region, Zambia: Constraint from Geochronology, Geochemistry and Sr–Nd–Hf Isotopes[J]. Northwestern Geology, 2023, 56(5): 20-34. DOI: 10.12401/j.nwg.2023116
Citation: XU Kangkang, SUN Kai, WU Xingyuan. Petrogenesis of Neoproterozoic Quartz Monzonite in Solwezi Region, Zambia: Constraint from Geochronology, Geochemistry and Sr–Nd–Hf Isotopes[J]. Northwestern Geology, 2023, 56(5): 20-34. DOI: 10.12401/j.nwg.2023116

赞比亚索卢韦齐地区新元古代石英二长岩的成因:年代学、地球化学和Sr–Nd–Hf同位素约束

基金项目: 中国地质调查局项目(DD20190439、DD20551801),国家重点研发计划课题“环太平洋和非洲成矿域战略性矿产信息及成矿规律”(2021YFC2901804)联合资助。
详细信息
    作者简介:

    许康康(1986–),男,高级工程师,主要从事地质矿产勘查与研究工作。E–mail:xukang06@163.com

  • 中图分类号: P581;P597

Petrogenesis of Neoproterozoic Quartz Monzonite in Solwezi Region, Zambia: Constraint from Geochronology, Geochemistry and Sr–Nd–Hf Isotopes

  • 摘要:

    研究卢菲利安弧地区新元古代与裂谷作用有关的基性–中酸性岩浆作用,对了解区域地壳生长和演化具有重要意义。研究表明,卢菲利安弧地区发育有大量新元古代与裂谷作用有关的基性岩类,但相关的中酸性岩岩浆作用却鲜有报道。笔者首次在赞比亚索卢韦齐地区发现有新元古代的石英二长岩体,锆石U–Pb年龄为(707.1±3.0)Ma。地球化学特征显示该岩体具有较低的MgO(0.46%~0.76%)、CaO(1.63%~1.76%)、K2O(0.49%~0.56%)、Mg#值(8~13)和Sr/Y值(1.14~2.50),较高的Al2O3(15.61%~16.02%)。岩体富集轻稀土和高场强元素HFSEs(Nb、Ta、Hf),(La/Yb)N值为6.64~7.86,亏损P、Ti、Zr和大离子亲石元素LILEs(Rb、Ba、Sr、K)。此外,石英二长岩具有低的初始87Sr/86Sr值(0.7058~0.7060),正的εNd(t)值(1.89~2.03)和锆石εHf(t)值(1.30~5.67),该特征与索卢韦齐地区新元古代早期辉长岩相似,推测石英二长岩可能为新生的镁铁质下地壳在中–低压条件下部分熔融形成的。综合地质年代学和岩石成因研究,笔者认为卢菲利安弧地区在新元古代经历了多阶段的地壳生长作用,后期侵位的地幔岩浆加热早期就位于下地壳的镁铁质岩石并导致其部分熔融,从而达到对地壳的改造作用。

    Abstract:

    The study of mafic–intermediate and felsic magmatism related to Neoproterozoic rift in the Lufilian Arc is of great significance for understanding the crustal growth and secular evolution of the region. Studies have shown that there are a large number of Neoproterozoic mafic rocks which are related to rifting in the Lufilan arc, but a few of related intermediate and felsic magmatism are discovered. A Neoproterozoic quartz monzonite with a zircon U–Pb age of 707.1±3.0 Ma was first discovered and reported in the Lufilian Arc. The pluton is characterized by relatively low MgO (0.46%~0.76%), CaO (1.63%~1.76%), K2O (0.49%~0.56%), Mg# values (8~13) and Sr/Y ratios (1.14~2.50), as well as high Al2O3 content (15.61%~16.02%). REE–normalized patterns show enrichment in LREE with (La/Yb)N of 6.64~7.86 and their primitive mantle-normalized trace element patterns are characterized by depletion of LILEs (Rb, Ba, Sr, K) and P, Ti, Zr and enrichment of HFSEs (Nb, Ta, Hf). They have a low initial 87Sr/86Sr ratios (0.7058~0.7060) with positive εNd(t) values (1.89~2.03) and their zircon εHf(t) values range from 1.30 to 5.67, their isotopic data are similar to those of the Neoproterozoic mafic intrusions in the Solwezi region, suggesting that the quartz monzonite were generated by partial melting of newly emplaced mafic lower crust. In combination with the studies of geochronology and petrogenesis, it is concluded that the Lufilian Arc experienced a multi–stage crustal growth in the Neoproterozoic, the late intrusive mantle magma heated the mafic rocks emplaced in the lower crust at early stage, resulting in partial melting and reworking the early crust.

  • 当前,对沉积盆地沉积碎屑岩的化学组分和碎屑锆石物源示踪研究已成为盆山耦合研究的主流方法(肖庆辉等,1995闫义等,2003)。沉积碎屑岩的组分特征能够通过化学组分很好地反映(Dickinson,1985),其地球化学特征在一定程度上反映了沉积物母岩特性和构造环境。近年来,通过碎屑岩微量、稀土元素进行沉积物源研究取得良好的效果(董顺利,2013徐多勋等,2020)。碎屑锆石LA–ICP–MS 原位U–Pb年代学研究方法已成为当前国内外学者开展古地理还原和古构造单元分析对比的主要方法手段,与传统测年方法对比,碎屑锆石具有稳定性强、富含放射性元素、不受部分熔融或变质作用的影响而能够保存源区岩石重要信息等特征,其U–Pb年代学方法具有不可替代的优势(彭守涛等,2009)。

    秦岭造山带作为中国中央造山带的中段,经历了长期复杂的构造运动,是中国中央造山带的重要组成部分(姜寒冰等,2023)。前人在南秦岭、北秦岭微地块及其邻区北祁连东段、扬子地块北缘、华北地块南缘的不同层位、不同地质体中投入了大量的物源示踪相关研究工作,取得了一定的进展(李怀坤等,2003闫全人等,2007祝禧艳等,2008徐学义等,2009王清海等,2011林振文等,2013敖文昊等,2014徐通,2016刘仁燕等,2020李平等,2023),但相关认识分歧较多,如南秦岭微地块南北两侧的“商丹洋”、“勉略洋”的存在时限、闭合时限均有不同的认识,从而限制了提供沉积物源的可能性。研究区所属的南秦岭微地块志留系中物源示踪工作研究鲜有报道,前人对研究区志留系迭部组的沉积时代主要参照区域地质调查和化石资料对比等,缺少相关同位素年代学证据。笔者试图通过对白龙江地区志留系迭部组浅变质碎屑岩进行微量稀土测试及碎屑锆石LA–ICP–MS原位U–Pb测年分析,结合区域上前人已有的研究成果,限定迭部组沉积时限,对迭部组的沉积物源区及其构造意义进行讨论分析,为研究和认识白龙江地区早古生代地层构造属性和西秦岭造山带构造演化提供科学依据。

    研究区位于西秦岭地区迭部县尖尼–洛大一带,大地构造地处西秦岭造山带之南秦岭微地块,北以商丹缝合带与西秦岭之北秦岭微地块及祁连造山带拼接,南以勉略缝合带与扬子板块之碧口微地块相连。本区属西秦岭造山带的主体,先后经历了多期多次、不同属性的构造运动,构造变形复杂。

    区域地层出露以早古生代志留系为主,次有晚古生界、中生界。志留系在区内出露较为完整,层序清晰,属浅变质岩系列,厚度大,构成了白龙江背斜的核部及两翼地层,总体为一套复理石建造,由老到新依次分为迭部组、舟曲组、卓乌阔组(图1)。区域岩浆岩活动较弱,以三叠纪侵入的花岗闪长岩、石英闪长岩、石英二长闪长岩及石英二长岩等中酸性为主,一般以小岩株状侵位于志留系、泥盆系浅变质地层中。断裂构造以北西向为主,次为北东向。

    图  1  研究区地质简图(角图据李亦飞等,2018
    1.第四系全新统;2.第四系更新统;3.白垩系热当坝组;4.三叠系光盖山组;5.三叠系郭家山组;6.三叠系隆务河组;7.三叠系马热松多组;8.三叠系扎里山组;9.二叠系迭山组;10.二叠系大关山组;11.石炭系岷河组;12.石炭系略阳组;13.石炭系益哇沟组;14.石炭系擦阔合组;15.石炭系蒲莱组;16.石炭系下吾那组;17.泥盆系当多组;18.泥盆系普通沟组;19.志留系卓乌阔组;20.志留系舟曲组;21.志留系迭部组;22.奥陶系苏里木塘组;24.三叠纪黑云母石英闪长岩;25.三叠纪黑云母石英闪长岩;26.石英闪长岩脉/石英闪长玢岩脉;27.石英脉;28.花岗岩脉;29.花岗斑岩脉;30.闪长玢岩脉;31.地质界线;32.正常/倒转岩层产状;33.断层;34.采样位置及编号
    Figure  1.  Geological map of the study area

    志留系迭部组最早为翟玉沛在1977年研究西秦岭志留系时所命名的迭部群,被定义为一套海相碎屑岩夹少量硅质岩及火山岩沉积。《甘肃省岩石地层》将迭部群厘定为迭部组(表1)(甘肃省地矿局,1997),定义为一套深灰色千枚岩、变砂岩、黑灰色含碳硅质板岩、硅质岩为主夹有白云质灰岩、白云岩,属于笔石相沉积。其与下伏奥陶系苏里木塘组、上覆舟曲组呈整合接触关系,沿甘肃省迭部县、舟曲县和武都市大量出露,向东经甘肃省康县延入陕西省境内。

    表  1  志留系迭部组划分沿革表
    Table  1.  Stratigraphic division and evolution of Silurian Diebu Formation
    地层划分机构(时间)
    叶连俊
    等(1945)
    穆恩之
    (1992)
    翟玉沛
    (1977)
    原西安地质
    矿产研究所(1989)
    川西北地质
    大队(1990)
    《甘肃省岩石
    地层》(1997)
    志留系下统白龙江系白龙江群迭部群迭部群(尖尼沟组、
    各子组、安子沟组)
    白龙江群下地组迭部组
    拉垅组
    塔尔组
    下载: 导出CSV 
    | 显示表格

    为了确保样品的代表性和分析结果的准确性,本次研究选择志留系迭部组出露的浅变质碎屑岩新鲜面、后期脉体不发育、连续沉积广泛发育的地段系统采集样品。采集微量、稀土元素样品4件(编号分别为YQ-1、YQ-2、YQ-3、YQ-4)及碎屑锆石测年样品(编号TW-1,岩性及采样位置与YQ-2一致)。

    YQ-1样品(采样位置为N 34°00′57″,E 103°28′53″)为黑色碳硅质板岩,具隐晶质结构和板状构造,矿物成分主要由石英(65%±)、碳质(33%±)和少量绢云母(2%±)组成。石英和碳质为非常细小的晶体团粒,几乎为隐晶质,边缘和界线模糊不清。石英呈隐晶质,他形粒状、不规则粒状。碳质呈隐晶质,与石英一起略显定向。岩石后期有粒度较粗的石英脉斜切板粒状。

    YQ-2(TW-1)样品(采样位置为N 34°01′04″,E 103°28′52″)与YQ1岩性相似,黑色碳硅质板岩,具隐晶质结构和板状构造,矿物成分主要由石英(65%±)、碳质(34%±)和少量绢云母(1%±)组成。石英和碳质呈非常细小的晶体团粒,几乎为隐晶质,边缘和界线模糊不清。石英呈隐晶质,他形粒状、不规则粒状;绢云母呈显微隐晶质、鳞片状集合体、片径大多为0.004~0.03 mm、定向性不强;碳质呈隐晶质与石英一起略显定向。

    YQ-3样品(采样位置为N 33°57′31″,E 103°52′37″)为灰黑色绢云母泥质板岩,具变余泥状结构和板状构造,矿物成分主要由泥质–隐晶质矿物(68%±)、绢云母(15%±)、石英(12%±)和绿泥石(3%±)组成,其次为少量碳质(1%±)和自形立方体晶形黄铁矿(1%±)。

    YQ-4样品(采样位置为N 33°56′18″,E 103°43′09″)为深灰色千枚状泥质板岩,具变余泥状结构和板状构造,由泥质–隐晶质矿物(45%±)、绢云母(42%±)、石英(10%±)、绿泥石(3%±)及微量铁质等组成(图2)。

    图  2  迭部组岩石野外照片和显微镜下图
    a.碳硅质板岩野外照片;b.YQ-2正交偏光照片;c.千枚状泥质板岩;d.YQ-4正交偏光照片;Qtz.石英;Ser.绢云母;Chl.绿泥石;C.碳质
    Figure  2.  Field photos and micrographs of Diebu Formation rocks

    岩石微量、稀土元素样品的测试分析由核工业地质局分析测试研究中心完成,采用Agilent 7500a型ICP–MS仪测定,分析精度误差一般小于5%。分析数据详见表2

    表  2  稀土及微量元素分析结果表(10–6
    Table  2.  Analysis results of rare earth and trace elements (10–6)
    样号YQ-1YQ-2YQ-3YQ-4样号YQ-1YQ-2YQ-3YQ-4样号YQ-1YQ-2YQ-3YQ-4
    Li9.58524.7652.3389.98 Ba48939862478.8797.7 Th9.3927.3220.3624.1
    Be1.3792.3842.1983.092La20.649.2442.1646.05U12.5911.033.745.065
    Sc5.45817.4414.6420.93Ce36.1495.2183.483.24∑REE112.93264.91225.31260.13
    Ti1450415746144362Pr4.59510.289.08910.25LREE82.58199.27172.84184.67
    V396.7204.5124.5151Nd16.5635.2931.3636.6HREE30.3565.6452.4775.46
    Cr29.1158.4861.17108.1Sm3.0876.2345.5476.926(La/Yb)N10.5211.8113.109.70
    Co0.40989.03414.9918.74Eu1.5993.0181.2851.608(La/Sm)N4.365.174.974.35
    Ni18.3944.542.3559.62Gd2.6995.4494.9536.543(Gd/Yb)N1.591.511.771.59
    Cu25.6428.6744.246.04Tb0.43940.86950.7641.028La/Th2.191.802.071.91
    Zn7.91662.6198.11134.1Dy2.2674.8254.0585.689La/Sc3.772.822.882.20
    Ga9.34621.2920.4830.17Ho0.54321.0980.88031.248Co/Th0.040.330.740.78
    Ge1.9034.9586.2448.296Er1.4513.0412.5633.525Th/U0.752.485.444.76
    As9.6435.7083.5397.486Tm0.25990.50370.36550.5656Zr/Sc11.419.9310.857.56
    Rb58.4153.8126.7198.9Yb1.4042.9912.3093.404Th/Sc1.721.571.391.15
    Sr44.1895.451.3967.11Lu0.25590.50170.37760.5651
    Y15.5728.9221.5631.96Hf1.7334.6964.1964.654
    Zr62.29173.2158.9158.2Ta0.76391.9241.6971.363
    Nb9.2624.3123.0715.41W1.2482.351.5772.437
    Mo30.8913.420.18790.2047Tl0.10890.091110.078030.0664
    Sn1.5033.9823.1144.161Pb15.3230.9210.718.752
    Cs3.4458.9667.35412.28Bi0.29530.50960.22120.5662
    下载: 导出CSV 
    | 显示表格

    锆石U–Pb法(LA–ICP–MS)同位素测年样品前期挑选、制靶等工作在北京天和信矿业技术开发有限公司实验室完成,样品通过粉碎、重选、磁选等常规程序分选、提纯,使用双目镜检查后手工挑选出晶形较为完整、透明度好、无明显裂隙和包裹体的锆石颗粒粘贴在环氧树脂上制靶。锆石经过打磨抛光等程序使其内部结构充分暴露,进行阴极发光(CL)显微图像、显微照相和激光剥蚀电感耦合等离子体质谱仪进行 U–Pb年龄测试,该项工作在南京大学实验室完成。激光剥蚀系统为Geolas200M,ICP–MS仪为Agilent7500a,激光剥蚀束斑直径为30 μm,激光脉冲为10 Hz,激光剥蚀样品的深度为20~40 μm。样品同位素比值和元素含量数据处理采用GLITTER软件,采用Andersen对测试数据进行普通铅校正,年龄计算机谐和图采用Isoplot软件完成,详见参考文献(Anderson,2002)。按照碎屑锆石年龄分布范围,对于大于1000 Ma的测点,采用207Pb/206Pb表面年龄;年龄小于1000 Ma的测点,采用更为可靠的206Pb/238U表面年龄(吴元保等,2004)。碎屑锆石U–Pb分析数据见表3,典型的锆石阴极发光图像如图3所示。

    表  3  碎屑岩LA–ICP–MS 锆石U–Pb年龄测定结果表
    Table  3.  LA–ICP–MS Zircon U–Pb dating results of clastic rocks
    样品号及
    分析点号
    PbThUTh/U同位素比值表面年龄(Ma)
    10–6207Pb/235U206Pb/238U207Pb/235U206Pb/238U
    TW1-095.7850.6660.850.8320.53990.00730.07070.0004438.44.8440.22.6
    TW1-0423.99127.21291.930.4360.54240.00760.06930.0004440.05.0432.12.5
    TW1-0826.15172.32277.630.6210.54310.00810.07060.0004440.55.4439.92.6
    TW1-25121.07105.37197.390.5340.54520.00640.07120.0005441.84.2443.33.1
    TW1-23140.93248.02287.740.8620.54540.00720.06970.0004442.04.7434.32.6
    TW1-26322.28212.26584.010.3630.55080.00730.07210.0005445.54.8449.02.7
    TW1-106.9637.97109.500.3470.55380.00790.07130.0005447.55.2444.13.1
    TW1-177.4562.0647.511.3060.55440.01180.07200.0005447.97.7448.43.2
    TW1-1316.5368.5186.690.7900.55500.00720.07190.0005448.34.7447.63.0
    TW1-1210.1662.20109.690.5670.55780.01350.07190.0006450.18.8447.33.7
    TW1(2)-6020.41429.00529.390.8100.56270.01170.07360.0007453.37.6458.04.5
    TW1-1535.09216.89376.090.5770.56550.00910.07320.0005455.15.9455.53.1
    TW1-1119.1166.37183.110.3620.56990.00920.07150.0004458.06.0445.02.5
    TW1-1428.22171.60291.240.5890.57010.00690.07220.0005458.14.5449.22.9
    TW1(2)-59103.271127.291152.010.9790.57670.01380.07360.0006462.38.9457.83.6
    TW1(2)-6237.26140.27386.550.3630.58230.01190.07580.0006465.97.6470.93.7
    TW1-1951.04127.08324.630.3910.58850.01190.07220.0005469.97.6449.53.3
    TW1-279.5054.31120.150.4520.59030.01130.07460.0007471.17.2463.64.1
    TW1(2)-64204.80286.521271.520.2250.59030.01620.07720.0008471.110.4479.34.6
    TW1(2)-6340.14214.11414.410.5170.59230.01280.07680.0008472.48.2477.24.6
    TW1-1631.82210.06343.860.6110.59690.01270.07800.0007475.38.1484.14.0
    TW1(2)-6125.75134.20257.130.5220.59780.02200.07410.0009475.814.0460.95.2
    TW1(2)-6728.81144.50288.260.5010.60140.01290.07980.0007478.18.2495.04.2
    TW1(1)-5347.13338.28477.280.7090.60410.02050.06970.0008479.813.0434.44.9
    TW1-4433.70304.87362.690.8410.61460.01150.08070.0008486.47.2500.34.7
    TW1-4217.65152.77194.230.7870.61520.01680.08000.0009486.810.6496.25.1
    TW1-2436.08221.50354.590.6250.61750.01160.07120.0009488.37.3443.25.3
    TW1(2)-6654.41262.32559.110.4690.61780.01350.07930.0007488.48.5492.24.4
    TW1-1829.71196.02342.730.5720.62190.01240.07930.0007491.17.8492.14.3
    TW1-41111.7938.61262.060.1470.62490.01160.07910.0007492.97.2490.94.3
    TW1-4839.60438.68406.491.0790.62940.00980.08120.0008495.76.1503.34.6
    TW1-408.3857.2292.250.6200.62980.01030.07760.0006496.06.4481.63.5
    TW1-4955.70375.96671.620.5600.63160.01230.08160.0007497.17.6505.94.2
    TW1(2)-6544.40221.13317.050.6970.63200.01090.07790.0008497.36.8483.65.0
    TW1-4744.33435.02497.840.8740.63310.01900.08110.0010498.011.8502.45.9
    TW1-4551.37175.51620.560.2830.63380.01200.08070.0008498.57.5500.64.5
    TW1-3030.67198.82370.040.5370.65730.01100.08350.0008512.96.8517.04.9
    TW1-287.0115.6516.230.9650.66120.01250.08300.0007515.37.7514.14.3
    TW1-3238.54176.81465.350.3800.66170.01470.08380.0008515.69.0518.55.0
    TW1-3167.79592.44715.470.8280.66220.02260.08350.0009515.913.8517.25.6
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    续表3
    样品号及
    分析点号
    PbThUTh/U同位素比值表面年龄(Ma)
    106207Pb/235U206Pb/238U207Pb/235U206Pb/238U
    TW1(2)-6813.87170.3977.002.2130.66250.01540.08590.0007516.19.4531.04.1
    TW1-4389.88547.821046.160.5240.66750.01190.08060.0007519.27.2499.74.1
    TW1-2018.83134.78193.410.6970.67130.01290.06480.0009521.57.8404.85.2
    TW1-2993.17434.87569.390.7640.68320.01800.08300.0008528.710.9514.24.8
    TW1-4655.44593.22643.820.9210.69840.01190.08100.0008537.87.1502.04.6
    TW1(2)-6983.99504.00813.350.6200.70730.01890.08890.0010543.111.2548.86.1
    TW1(1)-5016.03107.39176.200.6090.72140.01490.07980.0008551.58.8494.64.9
    TW1-3346.3582.49130.080.6340.72430.01530.08870.0009553.29.0547.85.6
    TW1-3434.01238.46376.360.6340.77340.01660.09430.0011581.79.5581.26.3
    TW1-36193.41293.75998.840.2940.86740.03450.10730.0014634.218.7657.08.1
    TW1-35341.75170.93764.530.2240.88660.01810.10320.0009644.59.7633.35.5
    TW1(2)-7139.88253.59444.570.5700.95370.03100.11230.0020680.016.1686.111.3
    TW1-3713.9198.38165.510.5941.19600.01890.13250.0013798.88.8801.97.2
    TW1(2)-7215.0159.18153.530.3851.20350.02160.13330.0015802.210.0806.58.4
    TW1-3829.72177.42307.690.5771.28570.01690.13990.0010839.47.5844.25.7
    TW1(2)-7385.35468.84869.610.5391.37020.04270.15000.0017876.318.3900.89.8
    TW1(1)-5115.6081.26181.480.4481.71100.04960.14530.00321012.718.6874.318.0
    TW1(2)-7486.03414.22487.410.8501.78780.02390.17400.00171041.08.71034.29.6
    TW1-3934.28207.02389.860.5312.32370.03590.20170.00241219.611.01184.313.0
    TW1(2)-7564.56344.62645.800.5343.78860.04590.28180.00211590.39.81600.310.8
    TW1(2)-7622.73106.76239.780.4454.42790.09030.30940.00381717.616.91737.718.5
    TW1(2)-7747.54278.03472.730.5886.00700.07590.36590.00301976.911.12010.014.4
    TW1(2)-7890.46476.32749.470.6366.10020.06360.37340.00241990.39.22045.611.2
    TW1(1)-5234.65208.34363.470.5737.01880.06310.35000.00222113.88.11934.810.5
    TW1(2)-7954.82354.98551.920.6439.74150.10070.43420.00312410.69.72324.713.8
    TW1(2)-8032.97153.56396.190.38810.22560.12930.46760.00392455.411.82473.017.4
    下载: 导出CSV 
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    图  3  碎屑锆石阴极发光图像及年龄图
    Figure  3.  Zircon cathodoluminescence image

    浅变质碎屑岩的化学成分主要取决于源岩的化学成分,与成岩相关的风化、搬运等地质作用也不容忽视。与源区风化作用相关的信息可借助岩石化学成分来实现,氧化作用和U的丢失对其影响较大,Th/U值与风化程度呈正相关关系(McLennan et al.,1993),一般认为Th/U值大于4,指示风化作用较强。样品Th/U–Th图解显示(图4),志留系迭部组YQ-1、YQ-2的Th/U值小于4,表明其风化程度较弱。YQ-3、YQ-4的 Th/U 值远大于上地壳的平均值(3.8),表明其经历较强的风化作用。

    图  4  样品Th/U–Th图解(据McLennan et al.,1993
    Figure  4.  Th/U–Th discrimination diagram

    沉积物化学成分的变化、矿物的分选程度可以通过研究Zr/Sc和Th/Sc值来做出判断,陆缘碎屑沉积物的Zr/Sc和Th/Sc值线性正相关关系总体上表明物源区成分具有与岩浆分异相似特征的变化趋势(McLennan et al.,1993)。Th/Sc 值能够很好地反映物源区的平均比值,沉积物的改造、锆石的富集一般与Zr/Sc 值呈正相关关系(McLennan et al.,1993)。4个样品的 Sc 含量远低于上地壳的平均含量,而其Zr含量平均值分别为 62.29×106~173.2×106,低于或略低于上地壳的平均含量(190×106),造成 Zr/Sc值较高。Zr/Sc和Th/Sc值表明迭部组碎屑组分大多没有经历再旋回(图5),指示沉积区距源区一般较近。

    图  5  样品Zr/Sc–Th/Sc图解(据McLennan et al.,1993
    Figure  5.  Zr/Sc–Th/Sc discrimination diagram

    前人通过研究稀土元素的配分型式来判别沉积物物源性质(McLennan et al.,1993)。4个样品的稀土元素含量、特征比值(表2)和球粒陨石标准化后的配分型式(图6)显示,迭部组∑REE 为112.93×106~264.91×106,平均为215.82×106;(La/Yb)N值为9.70~11.81,(La/Sm) N值为4.35~5.71,(Gd/Yb) N值为1.51~1.77。迭部组浅变质碎屑岩具有轻稀土明显富集,重稀土亏损的特征,且Eu负异常明显,指示迭部组碎屑岩的源岩为富硅的长英质岩石,如上地壳的酸性岩或沉积岩。

    图  6  样品稀土元素球粒陨石标准化配分图(据Boynton,1984
    Figure  6.  Rare earth element pattern distribution diagram

    La/Th–Hf 判别图解可以判别迭部组浅变质碎屑岩的构造环境沉积物物源(董顺利,2013),4个样品 La/Th–Hf投点均位于长英质物源区或其周围(图7a),与稀土元素结果较一致。在Co/Th–La/Sc图解中,样品投点主要位于长英质岩浆岩区(图7b)。

    图  7  样品La/Th–Hf(a)(据Floyd et al.,1987) 和Co/Th–La/Sc(b)(据Bhatia,1983)源岩属性判别图解
    Figure  7.  (a) LA/Th–Hf and (b) Co/Th–La/Sc discrimination diagrams of source rocks

    综上所述,迭部组浅变质碎屑岩成分来自上地壳长英质岩浆岩。

    风化作用、变质作用和成岩作用等因素一般会导致浅变质碎屑岩化学组分的变化,但其微量元素的地球化学标准仍然被广泛有效用来判别沉积构造环境(Sun et al.,1989董顺利,2013)。迭部组浅变质碎屑岩微量元素分析结果(表2)显示,它们在微量元素蛛网图呈规律性变化,Ba、U、Th等大离子亲石元素(LILE)相对富集,高场强元素(HFSE)Sr、Nb相对亏损,曲线分布特征与大陆上地壳的微量元素蛛网相似(图8)。微量元素在沉积过程中变化较弱,其活泼性较低,而沉积物微量元素的含量主要取决于源岩和风化作用,其对于判别沉积盆地构造环境有很好的指示作用(McLennan et al.,1993)。在Ti/Zr–La/Sc构造环境判别图解(图9)中,样品主要落入或靠近活动大陆边缘区域;在La–Th–Sc图解中,样品落入大陆岛弧、活动大陆边缘与被动大陆边缘区域(图10a);在Th–Sc–Zr/10图解中,样品落入活动大陆边缘及其附近区域(图10b);在Th–Co–Zr/10图解中,样品落入活动大陆边缘及其附近区域(图10c),综合判断迭部组主要呈现出活动大陆边缘型物源区的特征。

    图  8  样品微量元素原始地幔标准化蛛网图(据Sun et al.,1989
    Figure  8.  Spider diagram of trace elements in clastic rocks of Diebu Formation
    图  9  样品Ti/Zr–La/Sc构造环境判别图解(据Bhatia,1983
    Figure  9.  Ti/Zr–La/Sc discrimination diagram of tectonic environment
    图  10  构造环境判别图解(据Bhatia,1983
    a. La–Th–Sc图解;b. Th–Sc–Zr/10图解;c. Th–Co–Zr/10图解;A.大洋岛弧;B.大陆岛弧;C.活动大陆边缘;D.被动大陆边缘
    Figure  10.  Discrimination diagram of tectonic environment

    上述分析表明,迭部组浅变质碎屑岩显示上地壳长英质火山岩的物源特征,源区应以活动大陆边缘背景下构造环境为主。

    TW-1样品中大部分锆石颗粒呈浅粉色,晶形以半自形柱状、粒状为主,次圆粒状次之,自形晶少量,表面多呈粗糙状,个别可见裂纹,显示后期有受力迹象,大小为0.03~0.12 mm,延长系数为1.2~3,锆石分选性好,磨圆度一般。前人研究认为岩浆成因锆石Th/U值一般大于0.4,变质成因锆石Th/U值小于0.1(Hoskin,2002),文中所测的65颗有效碎屑锆石的Th/U值为 0.14~2.213,53颗锆石Th/U值大于0.4,无小于0.1的锆石,显示以岩浆成因为主(表3),CL图像亦显示该区间大多数的锆石具典型的岩浆锆石震荡环带特征(图3)。

    65个有效碎屑锆石 U–Pb 年龄中(表3),61个不谐和度小于或等于 5%(占93%),其谐和曲线见图11。从年龄谱图上看(图12),U–Pb有效年龄主要集中在440~680 Ma、798~876 Ma、1012~1291 Ma、1590~1990 Ma和 2113~2455 Ma等5个峰值。其中,440~680 Ma峰值共有51个碎屑锆石年龄,占该样品总有效数据的76.9%,其算术平均值为488 Ma,相对概率峰值为498 Ma,该区间年龄数据的不谐和度为−5%~10%,平均为 3%,因此是主要的和可信的年龄区间之一,可细分为438.4~553.2 Ma和581.7~680 Ma两个亚组,相对概率峰值年龄分别为498 Ma和644 Ma。798~876 Ma峰值共有4个碎屑锆石年龄,占该样品总有效数据的6.1%,其算术平均值为829 Ma,相对概率峰值为802 Ma。1012~1291 Ma峰值共有3个碎屑锆石年龄,占该样品总有效数据的3.1%,算术平均值为1130 Ma,相对概率峰值为1012 Ma。1590~1990 Ma峰值共有4个碎屑锆石年龄,占该样品总有效数据的6.1%,其算术平均值为1818 Ma,相对概率峰值为1976 Ma。2113~2455 Ma峰值共有3个碎屑锆石年龄,占该样品总有效数据的4.6%,算术平均值为2326 Ma,相对概率峰值为2324 Ma。

    图  11  锆石U–Pb 谐和曲线图
    Figure  11.  U–Pb harmonic curve of zircon
    图  12  锆石U–Pb年龄谱图
    Figure  12.  Zircon U–Pb age spectrum

    迭部组浅变质碎屑岩地处西秦岭造山带白龙江地区,前人在迭部县尖泥沟一带黑色碳质千枚岩中发现了大量笔石类化石(甘肃省地矿局,1999),其中Oktavites spiralisMonograptus cf. proboscifornis 均为中国下志留统标准分子,指示迭部组时代为早志留世,相当于早志留世晚凡伦期。

    笔者在迭部组中获得碎屑锆石最小年龄为440 Ma、最大年龄为2455 Ma,限定了迭部组原岩沉积时代的上限年龄,即其沉积时代不早于440 Ma(不早于早志留世),支持将迭部组时代定为早志留世。

    迭部组浅变质碎屑岩的样品共65颗碎屑锆石的LA–ICP–MS U–Pb年代学信息显示,锆石年龄主要集中在5个组(图11图12),结合区域地质资料及前人研究成果,其与区域构造岩浆热事件存在较好的对应关系。

    第一组年龄为440~680 Ma,为主要年龄分布区,峰值年龄为498 Ma,年龄相对集中,且呈现最强烈峰值特征,该组年龄基本为岩浆锆石谐和年龄,代表与早古生代加里东期构造运动有关的岩浆活动事件的年龄谱,与Gondwana大陆汇聚(650~500 Ma)时期大致相当。可细分为438.4~553.2 Ma和581.7~680 Ma两个亚组。438.4~553.2 Ma亚组在西秦岭北缘构造带发育的一系列加里东期岩浆活动,如天水关子镇蛇绿混杂岩中变辉长(534±9 Ma)和变斜长花岗岩(517±8 Ma)、武山蛇绿混杂岩中变辉长岩(440±5 Ma)和鸳鸯镇变辉长闪长岩(456±3 Ma,李王晔,2008)、关子镇蛇绿混杂岩中的变辉长岩(499.7±1.8 Ma)(裴先治等,2007);在北祁连造山带东段加里东期岩浆活动同样频繁,如阎家店闪长岩体(440.2±0.92 Ma)(魏方辉等,2012)、黄门川花岗岩体(442.8±2.1 Ma)(魏方辉等,2012)、张家川南寒武纪石英闪长岩体(547.7±68.8 Ma)等与该时限均接近。581.7~680 Ma亚组区域上南秦岭地区随枣盆地中发育较多的该时限基性–超基性岩浆活动,如南秦岭周庵超镁铁质岩体(637 Ma)(王梦玺等,2012)、寿山岩体(636±11 Ma)(洪吉安等,2009)、 独崇山岩体(632±6 Ma)(薛怀民等,2011)和 巴山岩体(631±11 Ma )(洪吉安等,2009),耀岭河群中变流纹质火山熔岩和晶屑岩屑凝灰质火山碎屑岩岩层中锆石的U/Pb 年龄为(685±5) Ma(凌文黎等,2007)。

    第二组年龄为798~876 Ma,年龄峰值为802 Ma,该组年龄代表了新元古代晚期构造岩浆活动时间,与Rodinia超大陆裂解时间(860~740 Ma)大致相当(李王晔,2008)。区域上与祁连造山带东端榆中县兴隆山群中火山岩(824~713 Ma)(王清海等,2011)、五峰村花岗岩体(846±2 Ma)(雍拥等,2008);北秦岭新阳-元龙花岗质片麻岩后期花岗岩浆事件(827~861 Ma)(刘会彬等,2006);南秦岭耀岭河群基性火山岩(808±6 Ma)(李怀坤等,2003)、南秦岭武当群火山岩(802±13 Ma)(刘仁燕等,2020);碧口地体坪头山闪长岩体(855±6 Ma)、关口垭闪长岩体(884±14 Ma)、白雀寺杂岩体(855±6 Ma)、铜厂闪长岩体(821±7 Ma)、二里坝花岗闪长岩体(823±7 Ma)、康县地区基性火山岩(841±19~812±11 Ma)(闫全人等,2007)、略阳郭镇地区铧厂沟金矿变玄武岩和变英安岩(802±5 Ma)(林振文等,2013)、张儿沟埃达克质岩(840±5 Ma)(徐通,2016);扬子地块北缘西乡群孙家河组流纹岩(832.9±4.9 Ma)和辉石玄武岩(845.0±17 Ma)(徐学义等,2009)、西乡群大石沟组(789.0±4.4 Ma)等岩浆岩结晶年龄相近。

    第三组年龄1012~1291 Ma,峰值年龄为1012 Ma,Grenvillian造山运动(900~1300 Ma)与本次碎屑锆石限定的1012~1291 Ma年龄区间年代基本吻合,该组年龄代表中元古代早期构造岩浆活动时间。区域上与北祁连东段马衔山地区中元古代花岗岩(1192±38 Ma)(王洪亮等,2011)、兴隆山地区玄武岩(1032~1172 Ma)(徐学义等,2009);扬子地块北缘黄陵背斜庙湾蛇绿混杂岩中的变辉长岩(1118~1096 Ma)(蒋幸福等,2014)、扬子地块西缘桃树湾辉长岩(1375±7 Ma)(任光明等,2017)等岩浆岩结晶年龄大致相当。

    第四组年龄1590~1990 Ma,峰值年龄为1 976 Ma,该组年龄代表中元古代晚期—古元古代早期构造岩浆活动时间,与Columbia超大陆汇聚–裂解时间(2100~1700 Ma)(Rogers et al.,2002)大致相当。前人研究显示,扬子地块西缘~1.40 Ga从Columbia超大陆裂解成洋(刘伟,2019)、华北地区碱性岩岩浆事件(1635~1625 Ma)与Columbia超大陆裂解有关(张健等,2015),指示该时限的锆石年龄为Columbia超大陆汇聚、裂解在区域上的响应。区域上华北地块南缘、北祁连东段、秦岭地块均分布有这一时期的岩浆活动,如华北地块南缘的熊耳群火山岩(1.80~1.75 Ga)(赵太平等,2004)、华北地块西南缘鲁山太华杂岩斜长角闪岩原岩为早元古代侵入的碱性玄武岩(1932±48 Ma)(林慈銮,2006)、华北地块铁岭组钾质斑脱岩(1437±21 Ma)(苏文博等,2010);祁连东段张家川新元古代复式深成杂岩体(1450 Ma)、长宁驿花岗质片麻岩(1765±57 Ma)(王银川等,2012);太白岩基中巩坚沟变形侵入体和宝鸡岩基胡店变形侵入体(1741±12 Ma、1770±13 Ma)(王洪亮等,2011)等岩浆岩结晶年龄接近,具有一定的亲缘性。

    第五组年龄2113~2455 Ma,峰值年龄为2324 Ma,该组年龄代表古元古代早期—新太古代晚期构造热事件,与全球性地壳增生事件的时间(峰期2500 Ma)(胡建等,2007)接近,代表古老变质结晶基底年龄。区域上与北祁连造山带陇山岩群正片麻岩结晶基底(1900 Ma、2300 Ma、2500 Ma)(何艳红等,2005);南秦岭略阳新太古代鱼洞子岩群花岗片麻岩(2661±17~2703±26 Ma)(张欣等,2010)、南秦岭陡岭杂岩主体的条带状闪长质–花岗质片麻岩(原岩侵位年龄为2469±22 Ma、2479±12 Ma、2501±17 Ma和2509±14 Ma)(胡娟等,2013);北秦岭古元古代秦岭岩群(1.0~0.95 Ga)(罗芬红,2019)、北秦岭中新元古代带宽坪岩群片麻状花岗岩(结晶年龄为1806±18 Ma)(高盛等,2015);碧口地体鱼洞子岩群中的TTG质片麻岩套(2.7~2.45 Ga)(刘宝星,2020)、鱼洞子岩群中磁铁石英岩(2645 Ma);华北地块南缘北沟岩体(2569~2530 Ma)(郭荣鑫,2018)、华北地块南缘新太古代安沟杂岩(2.54~2.51 Ga)(黄波,2020)等古老变质基底年龄接近,具有较好的亲缘性。

    综上所述,研究区所属的南秦岭微地块及其周缘微地块均有相近的岩浆事件。本次采取的碎屑锆石整体磨圆一般、部分锆石晶形较为完整,指示沉积物搬运距离有限,且Zr/Sc和Th/Sc值同样指示沉积区距源区一般较近,说明距离研究区较近的南秦岭微地块、北秦岭微地块、扬子地块北缘、北祁连东段提供物源的可能性明显大于华北地块南缘。

    前人研究表明,南北秦岭之间的“天水–武山洋”初始消减时限为早寒武世,期间发育大量岛弧型中基性杂岩和洋内岛弧火山岩,早中奥陶世后撤扩展形成二郎坪弧后盆地,后大约于400 Ma闭合(李王晔,2008);北秦岭地区早古生代发生的“商丹洋”俯冲碰撞造山伴随大量的俯冲碰撞花岗岩、双峰式火山岩等岩浆热事件,其俯冲碰撞时限为奥陶纪,志留纪已进入碰撞造山阶段(徐通,2016);奥陶纪发生以北秦岭关子镇蛇绿岩为代表的古洋盆扩张,并伴有洋壳俯冲作用、产生火山岩浆岛弧(裴先治等,2007);北秦岭秦岭岩群黑云斜长片麻岩中侵入的长英质脉体形成于(442±9)Ma,为商丹洋向北俯冲引起的构造热事件(兰瑞烜等,2020)。因而,南北秦岭微地块之间的“商–丹”洋闭合时限应不晚于440 Ma,早古生代是北秦岭重要的岩浆–变质作用时期。北秦岭与华北地块之间在新元古代时属于统一构造背景,广泛发育新元古代岩浆活动(凌文黎等,2007祝禧艳等,2008),二者在新元古代之后对接拼合(丁振举等,2018);对北秦岭与华北地块之间的宽坪岩群的相关研究认为,早志留世(~440 Ma)二郎坪陆源盆地与宽坪陆源盆地的闭合导致华北地块与北秦岭微地块拼接完成(王海杰等,2020)。北秦岭微地块和北祁连东段结合部位被以新阳–元龙大型韧性走滑剪切构造带分割(丁仨平等,2009),二者物质差异较大。研究发现,北秦岭木其滩斜长角闪岩为早古生代(锆石U–Pb 年龄为488.9±4.4 Ma)“商丹洋”西延洋壳俯冲的结果,北祁连造山带东段红土堡组变基性岩微量元素比率指示其为弧后盆地的构造背景,北秦岭微地块与北祁连造山带具有早古生代西秦岭北缘俯冲的特征,可能经历了相似的构造演化(尚渊甲,2021);北祁连造山带与北秦岭微地块结合部位发育的俯冲型花岗岩(471~440 Ma),指示二者早古生代发生拼接(魏方辉等,2012);中元古代早期北祁连东段属于华北地块的一部分,二者构造岩浆热事件同步,表现为相同的结晶基底和构造属性,该期构造热事件可能与Columbia超大陆在区内响应有关(王银川等,2012)。北秦岭微地块与扬子地块之间的勉略洋盆于新元古代早中期(~800 Ma)闭合,其双向俯冲于北秦岭微地块和碧口微地块之下,与Rodinia超大陆裂解事件在区域上的响应有关(李亦飞等,2018)。随后,南秦岭微地块、勉略缝合带、扬子地块西北缘(碧口微地块)进入后碰撞–裂解进程,志留纪形成勉略裂陷槽接受稳定沉积(徐通,2016)。综上所述,南秦岭微地块及其周缘板块经历了复杂的构造岩浆热事件,在早志留世(440 Ma)南秦岭微地块与华北地块、北祁连东段、北秦岭微地块、扬子地块(碧口微地块)都以不同方式、不分先后、不同程度的拼接在了一起。据此认为北秦岭微地块、祁连造山带、华北地块南缘、扬子地块北缘,其与南秦岭微地块自身都存在为迭部组提供物源的可能性。

    根据前人研究成果和文中对研究区及其周缘可能物源区的区域性岩浆事件统计结果显示(图13),研究区440~680 Ma时限的年龄谱图与北秦岭微地块吻合度极高,其次与南秦岭、扬子北缘有一定的吻合度,显示北秦岭微地块为迭部组浅变质碎屑岩提供了主要的物源,与前人研究认为北秦岭微地块广泛发育古生代岩浆作用(李亦飞等,2018)对应,其次为南秦岭微地块、扬子地块北缘、北祁连东段;798~876 Ma时限的年龄谱图与南秦岭微地块、扬子北缘吻合度高,该时限碎屑锆石提供了主要物源,其次为北秦岭微地块;1012~1291 Ma时限的年龄谱图显示,该时限的主要碎屑锆石来源于北秦岭微地块,北祁连东段可能参与部分物源供给;1590~1990 Ma时限的碎屑锆石主要北秦岭微地块提供,华北地块南缘虽有该时限的结晶年龄、但提供物源的可能性不大;2113~2455 Ma时限的碎屑锆石与华北地块南缘的岩浆事件具有一定的对应性,其可能来源于华北地块南缘,但因碎屑锆石的磨圆特征且该时限数量较少不具代表性,不排除南、北秦岭微地块中的老地层参与供给但抬升被剥蚀已经不再保存或被后期构造掩盖的可能性。

    图  13  研究区及其邻区碎屑锆石U–Pb年龄累计频谱图(据罗芬红,2019任龙,2019寇琳琳等,2022
    Figure  13.  Cumulative U–Pb age spectrum of detrital zircon in the study area and its adjacent areas

    自早古生代以来,受“商丹洋”闭合影响,海域面积大幅度减少,甘肃境内南秦岭地区志留世接受广泛的物源沉积,而北秦岭地区基本未见志留世沉积,指示“商丹洋”闭合过程中北秦岭微地块抬升、遭受剥蚀,南秦岭微地块的抬升明显低于北秦岭,为区内迭部组接受物源沉积提供有利的地形条件。同时,岩石化学判别显示迭部组碎屑岩源区形成以活动大陆边缘背景下构造环境为主,印证了区内沉积物源主要来源于北秦岭的可能性。综上所述,北秦岭作为源区为其南侧志留系迭部组提供主要的沉积物质,南秦岭微地块、扬子地块提供部分沉积物源,北祁连东段可能参与物源供给。

    (1)迭部组碎屑组分大多没有经历再旋回,沉积区距源区不远;母岩为沉积岩或上地壳酸性岩,源区形成于活动大陆边缘背景下构造环境特征。

    (2)迭部组沉积的浅变质碎屑岩碎屑锆石U–Pb最小年龄为440 Ma,代表了其沉积下限,其与区域笔石类化石定年结论相同,指示迭部组时代为早志留世。

    (3)迭部组沉积的物源年龄构成主要有440~680 Ma、798~876 Ma、1012~1291 Ma、1590~1990 Ma、 2113~2455 Ma等5个年龄组,显示区内物源类型的复杂性。总体来看,迭部组沉积物源主要来自北秦岭微地块,少量来自于南秦岭微地块、扬子地块,祁连东段可能参与部分物源供给。

  • 图  1   赞比亚Solwezi地区石英二长岩分布(a)及南部非洲构造划分图(b)(据Katongo et al.,2002Johnson et al.,2005Selley et al.,2005

    I. 外部褶皱逆冲带;II. 穹隆区;III. 复向斜带;IV. 加丹加高原;V. 前陆盆地

    Figure  1.   (a) The distribution of quartz monzonite in Solwezi area and (b) the tectonic division ofthe Southern Africa

    图  2   赞比亚穹窿区石英二长岩野外(a)、手标本(b)及显微照片(c、d)

    Pl. 斜长石;Hbl. 角闪石;Kfs. 钾长石;Q. 石英

    Figure  2.   (a) Field photographs, (b) hand specimen and (c, d) micrographs of quartz monzonite in Dome area, Zambia

    图  3   石英二长岩代表性锆石CL图像(a)和锆石U–Pb年龄谐和图(b、c)

    Figure  3.   (a) Cathodoluminescence (CL) images and (b, c) U–Pb concordia diagrams for representative zircons from quartz monzonite

    图  4   石英二长岩Zr/TiO2–Nb/Y图解(a)(据Middlemost,1994)和AR–SiO2图解(b)(据Wright,1969

    Figure  4.   (a) Zr/TiO2–Nb/Y and (b) AR–SiO2 diagrams for quartz monzonite

    图  5   石英二长岩主量元素和代表性微量元素Harker图解

    Figure  5.   Harker plots of major and selected trace elements for quartz monzonite

    图  6   原始地幔标准化微量元素(a)和球粒陨石标准化稀土元素(b)图解(据Sun et al.,1989

    Figure  6.   (a) Primitive Mantle (PM) normalized trace elements and (b) Chondrite–normalized REE elements diagrams of quartz monzonite

    图  7   石英二长岩锆石εHft)–207Pb/206Pb年龄图解(a)和εNdt)–87Sr/86Sr(i)图解(b)

    Figure  7.   (a) εHf(t)–zircon 207Pb/206Pb age and (b) εNd(t) –87Sr/86Sr for quartz monzonite

    图  8   石英二长岩的Mg#–SiO2图解(a)(据Wang et al.,2005)和Th/U–Th图解(b)(据Rudnick et al.,2003

    Figure  8.   (a) Mg#–SiO2 and (b) Th/U–Th diagrams for quartz monzonite

    图  9   石英二长岩AFM图解和摩尔Na–K–Ca图解(据Zhao et al.,2010

    Figure  9.   Ternary AFM and molar Na–K–Ca diagrams for quartz monzonite

    图  10   石英二长岩的SiO2–TiO2(a)和SiO2–MgO(b)图解(据Jung et al.,2002

    Figure  10.   (a) SiO2–TiO2 and (b) SiO2–MgO diagrams for quartz monzonite

    表  1   石英二长岩LA–MC–ICP–MS锆石U–Pb定年结果统计表

    Table  1   LA–MC–ICP–MS zircon U–Pb dating results of quartz monzonite

    点号含量(10–6Th/U比值年龄(Ma)
    ThU 207Pb/206Pb207Pb/235U206Pb/238U207Pb/206Pb207Pb/235U206Pb/238U
    0116400.410.06600.00471.02860.06440.11640.00238061507183271013
    0240610.650.06540.00351.02550.05060.11570.00187871147172570611
    0357800.710.06490.00261.02400.04050.11540.001476985716207048
    0438630.610.06390.00341.01350.05530.11490.0015739107711287019
    0534580.580.06470.00251.02280.03960.11540.001476588715207048
    0644620.700.06260.00340.99630.04980.11660.0014694117702257118
    0738610.620.06420.00301.01470.04210.11610.001475094711217088
    0846690.670.06390.00261.00940.03920.11590.001473985709207078
    0946720.640.06470.00351.02400.05520.11520.00177651177162870310
    1033640.510.06630.00321.06600.04520.11970.00208171007372272911
    1138620.610.06530.00381.00880.05190.11480.00197871227082670011
    1231510.610.06290.00311.00110.04590.11710.0016703104704237149
    1318440.420.06460.00321.01630.04720.11550.0016761104712247059
    1426560.460.06390.00281.02090.04370.11560.001573986714227059
    1522410.540.06520.00591.01260.08460.11500.00257891937104370214
    1668920.730.06400.00241.02660.03780.11660.001374380717197117
    1734460.740.06350.00311.02500.05180.11720.00197241107162671411
    1850730.690.06200.00270.98860.04190.11510.001667688698217029
    1923580.400.06280.00280.99750.04370.11590.0017702967032270710
    2030550.550.06280.00291.00360.04590.11600.0015702101706237089
    2146700.660.06260.00281.00590.03900.11650.001669695707207109
    221231410.870.06010.00490.98510.05230.11640.00176091716962771010
    2324480.510.06230.00430.96860.05800.11540.00206871506883070411
    2415360.430.06160.00500.98230.06920.11710.00236611796953571413
    2533540.610.06180.00310.98240.04760.11570.0016666101695247069
    2632680.480.06510.00361.03150.05710.11500.00217761157202970212
    2759750.790.06390.00261.02500.03820.11630.001373992716197098
    2851820.630.06360.00251.02080.04080.11620.0018728857142170910
    2938750.510.06280.00290.99090.04340.11520.001270294699227037
    3033570.580.06160.00330.98990.05380.11580.00176611156992770610
    3124450.540.06310.00420.97130.05610.11570.00217221456892970612
    3241690.590.06280.00341.01040.05300.11680.00177021157092771210
    3352710.730.06400.00341.01800.04830.11620.0014743108713247098
    3445620.720.06450.00301.02150.04220.11510.001476198715217028
    3538560.680.06140.00420.97440.05590.11520.00186541466912970310
    3658780.740.06350.00281.02050.04420.11640.001572493714227109
    3737530.710.06390.00341.01040.05280.11550.0017 7391187092770510
    下载: 导出CSV

    表  2   石英二长岩的主量元素(%)和微量元素(10−6)分析结果表

    Table  2   Major element (%) and trace element compositions (10−6) for quartz monzonite

    样品号SiO2Al2O3Fe2O3FeOCaOMgOK2ONa2OTiO2P2O5MnO灼失CuPbZnCrNiCoRb
    ZS05-160.9015.806.992.831.760.760.548.001.010.20.0230.8711.71.7426.54.6711.110.73.16
    ZS05-261.7116.027.671.261.650.460.558.621.020.240.0150.6411.11.5326.20.618.439.342.35
    ZS05-361.3415.618.481.301.670.460.568.241.020.240.0160.9311.91.1522.40.608.168.461.96
    ZS05-461.5315.836.862.701.630.740.497.950.970.140.030.8210.81.3326.32.7611.910.21.57
    样品号CsSrBaVScNbTaZrHfGaUThLaCePrNdSmEuGd
    ZS05-10.0415466.26.9626.189.95.3184831.334.31.708.697814726.310520.96.0119.1
    ZS05-20.0316856.77.4027.990.95.5589433.736.51.811.8014212446.219438.510.7036.6
    ZS05-30.0313449.05.2225.489.55.2884432.033.01.468.3912813042.418036.210.0034.1
    ZS05-40.0414248.77.4624.892.65.5188132.933.81.4010.707510522.79017.14.9416.1
    样品号TbDyHoErTmYbLuYMg#Th/UΣREEδEuδCe(La/Yb)N87Sr/86Sr(tεNdtTDM2(Ma)
    ZS05-12.9815.22.858.491.187.921.2261.7135.11442.250.900.786.650.70581.891243
    ZS05-25.7930.55.7116.202.2314.12.08131.096.56668.610.860.376.79///
    ZS05-35.5028.25.2215.002.0213.01.90118.085.75631.540.860.426.640.70602.031232
    ZS05-42.3811.82.196.740.956.391.0149.4137.64362.200.900.617.86///
     注:Mg#=100×(MgO/40.32)/(MgO/40.32 + FeOt/71.94)。
    下载: 导出CSV

    表  3   石英二长岩锆石原位Lu–Hf同位素结果表

    Table  3   Zircon in situ Lu–Hf isotope data of quartz monzonite

    点号年龄(Ma)176Yb/177Hf176Lu/177Hf176Hf/177HfεHftTDM1TDM2
    017070.03610.00080.00120.00000.2823830.0000221.300.95123330154050
    027070.03310.00050.00110.00000.2824620.0000234.150.92111832136052
    037070.04910.00060.00150.00000.2824660.0000274.071.02112738136661
    047070.03840.00050.00120.00000.2824970.0000245.340.94107234128655
    057070.03140.00050.00100.00000.2824950.0000225.340.84107130128649
    067070.03820.00050.00130.00000.2824710.0000204.350.80111329134847
    077070.03450.00050.00110.00000.2824250.0000212.800.82117330144648
    087070.03870.00020.00120.00000.2824210.0000242.620.93118134145755
    097070.04400.00070.00140.00000.2824000.0000241.820.95121534150754
    107070.05420.00130.00170.00000.2824260.0000252.571.01118936146057
    117070.03150.00010.00100.00000.2823930.0000221.690.92121531151551
    127070.02870.00020.00100.00000.2824010.0000202.050.81120028149346
    137070.02450.00030.00080.00000.2824900.0000245.230.95107334129355
    147070.03470.00010.00120.00000.2824150.0000272.431.02118838146960
    157070.03220.00050.00110.00000.2824770.0000264.641.10110036133060
    167070.04800.00030.00160.00000.2824730.0000234.290.89111833135253
    177070.02960.00060.00100.00000.2823900.0000231.630.91121733151953
    187070.03490.00020.00120.00000.2824350.0000243.130.97116034142555
    197070.04180.00030.00140.00000.2824880.0000254.910.95109235131356
    207070.02260.00010.00080.00000.2824170.0000232.670.91117432145453
    217070.03480.00070.00110.00000.2823950.0000241.720.92121633151354
    227070.03690.00090.00120.00000.2824700.0000264.350.99111237134859
    237070.06710.00070.00220.00000.2824520.0000263.251.00116937141759
    247070.02810.00030.00090.00000.2824830.0000254.951.01108635131057
    257070.03140.00060.00110.00000.2824520.0000223.780.98113332138453
    267070.03330.00060.00110.00000.2824110.0000262.330.98119136147558
    277070.02930.00210.00100.00010.2825040.0000245.670.97105734126556
    287070.04320.00010.00150.00000.2824360.0000233.050.96116732143052
    297070.02720.00010.00100.00000.2824320.0000253.140.95115735142457
    307070.03590.00070.00120.00000.2824880.0000215.020.87108530130649
    下载: 导出CSV
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  • 收稿日期:  2023-04-02
  • 修回日期:  2023-06-10
  • 录用日期:  2023-06-11
  • 网络出版日期:  2023-06-27
  • 刊出日期:  2023-10-19

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