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冀东金宝沟花岗斑岩地球化学特征、LA-ICP-MS锆石U-Pb年龄和Hf同位素及其地质意义

李曼, 柴凤梅, 叶会寿, 苏慧敏, 路东宇, 张丽颖, 张海滨

李曼, 柴凤梅, 叶会寿, 苏慧敏, 路东宇, 张丽颖, 张海滨. 2016: 冀东金宝沟花岗斑岩地球化学特征、LA-ICP-MS锆石U-Pb年龄和Hf同位素及其地质意义. 地质通报, 35(5): 790-806.
引用本文: 李曼, 柴凤梅, 叶会寿, 苏慧敏, 路东宇, 张丽颖, 张海滨. 2016: 冀东金宝沟花岗斑岩地球化学特征、LA-ICP-MS锆石U-Pb年龄和Hf同位素及其地质意义. 地质通报, 35(5): 790-806.
LI Man, CHAI Fengmei, YE Huishou, SU Huimin, LU Dongyu, ZHANG Liying, ZHANG Haibin. 2016: LA-ICP-MS zircon U-Pb ages, geochemistry and Hf isotopic composition of Jinbaogou granite porphyry in eastern Hebei and their geological implications. Geological Bulletin of China, 35(5): 790-806.
Citation: LI Man, CHAI Fengmei, YE Huishou, SU Huimin, LU Dongyu, ZHANG Liying, ZHANG Haibin. 2016: LA-ICP-MS zircon U-Pb ages, geochemistry and Hf isotopic composition of Jinbaogou granite porphyry in eastern Hebei and their geological implications. Geological Bulletin of China, 35(5): 790-806.

冀东金宝沟花岗斑岩地球化学特征、LA-ICP-MS锆石U-Pb年龄和Hf同位素及其地质意义

基金项目: 

中国地质调查局项目 编号:1212011220492

详细信息
    作者简介:

    李曼(1991-),女,在读硕士生,矿物学、岩石学、矿床学专业。E-mail:339842391@qq.com

    通讯作者:

    柴凤梅(1971-),女,博士,教授,从事岩石学、矿床学的教学与研究工作。E-mail:chaifengmei@163.com

  • 中图分类号: P534.52;P597

LA-ICP-MS zircon U-Pb ages, geochemistry and Hf isotopic composition of Jinbaogou granite porphyry in eastern Hebei and their geological implications

  • 摘要:

    金宝沟金矿床是冀东地区近年查明的一个大型斑岩型金矿床,金矿体主要赋存于金宝沟花岗斑岩体及岩体与太古宙迁西群黑云角闪斜长片麻岩接触带中。为查明金宝沟含矿花岗斑岩体的成岩时代、岩石地球化学特征、岩浆源区特征及其与区域上峪耳崖、牛心山等成矿花岗岩体的关系,采用LA-ICP-MS锆石U-Pb定年方法,测得金宝沟2件花岗斑岩的成岩年龄分别为169.9±1.0Ma和170.4±2.0Ma,表明其形成于中侏罗世。金宝沟花岗斑岩属于过铝质钾玄岩系列岩石,ΣREE含量为38.17×10-6~136.51×10-6,岩石富集Rb、K等大离子亲石元素和Ba、Th、U,亏损Ta、Nb、Ti等高场强元素和P、Sr,显示出典型岛弧或活动大陆边缘岩浆岩的特征。锆石Hf同位素研究显示,2件花岗斑岩样品的锆石εHf(t)分别为-12.8~-7.4和-14.4~-8.8,两阶段模式年龄分别为1685~2028Ma和1773~2130Ma,暗示岩浆可能来源于古元古代地壳物质的部分熔融。金宝沟花岗斑岩岩浆形成的温度为788~834℃,岩浆形成压力为0.8~1.6GPa。结合区域地质资料认为,包括金宝沟花岗斑岩在内的冀东中侏罗世花岗岩及同时代的髫髻山组火山岩是在陆内收缩、地壳增厚、古太平洋板块向欧亚大陆俯冲的构造背景下,在挤压应力松弛的间隙环境侵位的。

    Abstract:

    The Jinbaogou gold deposit in eastern Hebei has been recently identified as a large porphyry gold deposit. The orebodies mainly occur in Jinbaogou granite porphyry and the contact zone between the granite porphyry and the biotite-hornblende plagiogneiss of Archean Qian'xi Group. In order to confirm the age, geochemistry,magma source characteristics of Jinbaogou granite porphyry and its relationship with Yu'erya and Niuxinshan granites, the authors conducted LA-ICP-MS zircon U-Pb dating of the two granite porphyries, which yielded ages of 169.9±1.0Ma and 170.4±2.0Ma, suggesting the products of Middle Jurassic. Jinbaogou granite porphyry falls into the peraluminous and shoshonite series, its total values of REE are 38.17×10-6~136.51×10-6; and the rock is characterized by enrichment of large lithophile elements (Rb, K) and Ba, Th, U but depletion of high-field strength elements (Ta, Nb, Ti) and P, Sr, displaying the characteristics of typical island arc or magmatic rocks of active continental margin. Zircon Hf isotope studies show that the εHf(t) values and TDM2 ages of two granite porphyry samples are -12.8~-7.4 and -14.4~-8.8, 1685~2028Ma and 1773~2130Ma, respectively, implying representatives of the Paleoproterozoic crustal reservoir. Integrated with the regional geological materials, it is considered that the Middle Jurassic granites in the eastern Hebei, including the Jinbaogou granite porphyry and volcanics of Tiaojishan, were under the tectonic settingsof crustal thickening and the subduction of ancient Pacific plate towards Eurasian plate, and were emplaced during the relaxation after extrusion stress.

  • 哀牢山构造带是藏东(东南亚)地区最重要的一条线性构造和显著的地质地貌分界线[1],是印支地块与扬子地块的分界线,是印度-欧亚大陆碰撞过程中逃逸块体的西边界,同时也是川滇菱形块体的西南边界,在青藏高原的大陆逃逸地球动力学模型中具有重要的意义[2],长期以来被国内外地学界所关注。以往的研究主要侧重于对哀牢山-红河走滑剪切带运动学特征、运动时限、运动模式及转换机制的研究,而对构成哀牢山构造带主体的深变质岩系(哀牢山岩群)的时代和构造属性的研究较少,且存在争议。前人[3-4]依据相关同位素测年结果和区域地质资料,将哀牢山深变质岩系(哀牢山岩群)暂定为新元古代,认为其物质组成和成矿作用特点与扬子准地台间有更多联系,因此将其划为扬子准地台丽江台缘褶皱带内的一个三级构造单元,即扬子地台的结晶基底;但也有学者认为,该构造带构造延伸方向与唐古拉-昌都-兰坪-思茅褶皱系较一致,将哀牢山岩群划为唐古拉-昌都-兰坪-思茅褶皱系的第一结晶基底[5]。近年来,部分学者的研究结果对哀牢山岩群原岩形成时代及构造归属提出了挑战,认为哀牢山岩群不全形成于元古宙,也不全是扬子地台的结晶基底[6-8]。造成上述不同认识的主要原因之一是,基底岩石已有的年代学研究结果少且准确度低。此外,由于造山作用的强烈改造,大多数地层的原有序列遭受破坏,一些古生代或中生代岩体由于遭受高级变质作用而被误认为是前寒武纪基底岩石。哀牢山深变质岩系的形成时代、变质时代,以及哀牢山岩群的构造属性,这些关键性问题都关系着对该区地质构造特征及成矿规律的认识。为解决上述问题,本文选取哀牢山岩群花岗质片麻岩、花岗闪长质片麻岩及花岗质岩脉,以及哀牢山岩群西侧的变质粉砂岩为研究对象,采用LA-ICP-MS 锆石U-Pb 同位素测定技术,揭示和探讨哀牢山岩群的原岩形成时代、变质变形时代及哀牢山构造带构造属性。

    哀牢山构造带在大地构造上位于扬子准地台、松潘-甘孜褶皱系和唐古拉-昌都-兰坪-思茅褶皱系3 个一级构造单元,以及扬子准地台内丽江台缘摺皱带和滇东台褶带2 个二级构造单元的接触过渡带[2]。它被作为哀牢山板块缝合线,具备双变质带的特征,其中哀牢山岩群为低压高温带[9]。有的将其作为喜马拉雅期的陆内左行走滑平移剪切带[10],有的将其看作逆冲-推覆构造[11],为表达统一,本文暂将其称为哀牢山构造带,构造带由九甲-墨江断裂、哀牢山浅变质岩系、哀牢山断裂、哀牢山深变质岩杂岩(哀牢山岩群)、红河断裂,以及分布于带内的超基性、基性、酸性岩体共同构成(图 1)。

    图  1  哀牢山构造带地质简图(据参考文献[1]修改)
    Figure  1.  Simplified geological map of the Ailaoshan tectonic belt

    哀牢山岩群为一套混合岩化强烈的中深变质岩系,因沿哀牢山脉分布而得名,两侧分别为哀牢山断裂和红河断裂所限,呈NW—SE 向条带状延伸,向北延至南涧县密滴附近,因上述2 条断裂相交而消失,向南延入越南,变质岩系延伸长度约500km,宽20~30km,厚度大于8500m,以中国境内分布为主。哀牢山断裂东侧红河断裂西侧为哀牢山深变质岩系(哀牢山岩群),一般达高绿片岩相-角闪岩相,局部具高角闪岩相的特点,主要由各类片岩、片麻岩、变粒岩、透辉大理岩等组成;哀牢山断裂西侧为一套低绿片岩相变质岩系,主要为岔河、大平坝、转马路及外麦地岩组,一般称为马邓岩群,岩性主要为千枚岩及千糜岩、片岩、板岩、变质砂岩等;深变质岩带因受剪切带活动影响,岩石局部发生糜棱岩化,同时由于该岩群岩石变质较深,混合岩化强烈,片理化或劈理化也强烈,加之多期构造运动的改造,使原岩面貌改变较大,岩石的结晶片理、片麻理已全面取代原生层理,难以建立确切的地层层序。1965 年云南省地质局区测队将该深变质岩系命名为哀牢山岩群[4],命名剖面位于云南元江县小羊街南满河( 小羊街组)、元阳县大文迷河( 凤港组、阿龙组)、个旧- 金平公路大平台(乌都坑组)。1973 年进一步将该群自下而上划分为小羊街组(Ptx)、阿龙组(Pta)、凤港组、乌都坑组,并作为一个向北东倾斜的单斜构造看待[4]

    样品SM-15 为碎裂岩系,采于云南新平县水塘镇拉博村新房子社SSE900m,即N24°6.164′、E101°30.403′,位于1∶20万新平幅地质图上Pta(a 阿龙组下亚组)(图 1-a)。野外露头呈浅灰黄色,风化严重,风化面为黄褐色(图版Ⅰ-a),主要矿物有石英、长石,次要矿物为黑云母、角闪石,粒径大小不一,肉眼可见;石英、长石含量约85%,云母和角闪石含量较低,约占10%;石英、长石颗粒被碎裂化,具有不规则的撕碎边缘,呈锯齿状、棱角状,黑云母发生扭曲,为典型的碎裂结构;岩石中矿物无定向排列,为块状构造(图版Ⅰ-e),初步定名为花岗质片麻岩或碎裂岩。

      图版Ⅰ  a、b、c. 深变质岩系野外露头;d. 浅变质岩系野外露头(SM-15、SM-22、SM-18、NO-1 代表岩石编号);e~h. 分别为样品SM-15、SM-22、SM-18、NO-1 显微镜下照片(+)。Qtz—石英;Bt—黑云母;Kfs—钾长石;Ms—白云母;Pl—斜长石

    样品SM-22 采自国道323 沿线,具体位置为元江镇咪哩乡土堆梁子新寨白岩浅沟处,即N23°33.063′、E101°55.019′,采样处位于1∶20 万墨江幅地质图中Ptx(b 小羊街组上亚组,图 1-c)。野外露头为灰白色,风化后颜色变化不大(图版Ⅰ-b),主要矿物有石英、长石,次要矿物为黑云母,石英、长石含量为60%左右,云母含量35%左右,为粒状鳞片花岗变晶结构,岩石以粒状矿物为主,片状矿物云母被长石、石英分开显得不连续,为典型的片麻状构造(图版Ⅰ-f),暂定名为花岗闪长质片麻岩。

    样品SM-18 采自新平县漠沙镇红旗村中部,即N23°46.066′、E101°43.621′,位于1∶20 万墨江幅地质图中Pta(a 阿龙组的下亚组,图 1-b)。样品呈灰白色,风化面为黄色(图版Ⅰ-c),主要矿物有石英、长石,副矿物有云母等,其中长石含量50%,石英、长石为90%左右;粒径3mm 左右;石英与长石相互穿插排列,细粒变晶结构,矿物无定向排列,为典型的块状构造(图版Ⅰ-g),初步定名为浅变粒花岗岩,属于后期同变形变质作用下形成的长英质脉体。

    样品NO-1 采自新平县建兴乡挖窖村奥特坡,即N23°43.093′、E101°40.416′,位于1∶20 万墨江幅地质图中T3?(图 1-b),紧邻哀牢山岩群西侧的浅变质岩系中,野外露头呈灰绿色,表面为土黄色(图版I-d),主要矿物成分为石英、云母;粒径较小,石英与云母定向性排列(图版Ⅰ-h),为典型的石英云母片岩或变质砂岩。

    用于锆石U-Pb 测年的样品粉碎至40~60 目,由河北省廊坊市区域地质调查研究院在双目镜下挑选出晶形完好、纯度在99%以上的锆石样品。将锆石样品置于环氧树脂中,制成样品靶,在样品靶改造固结后,打磨至约1/2 并抛光,使锆石中心部位暴露出来,用于锆石阴极发光(CL)照相。

    锆石的阴极发光照相(图 4)在中国地质科学院国土资源部成矿作用与资源评价重点实验室完成,用于锆石形态和内部结构研究。锆石原位U-Pb 同位素分析在中国地质科学院国家地质实验测试中心LA-ICP-MS 仪器上完成,测点的选取力求避开内部裂隙等区域,以获得较准确的年龄信息。实验中每个样品选取30 个点进行分析测试,分析仪器为Thermo ElementⅡ质谱仪和New Wave 193 型激光剥蚀系统,激光波长为193nm,激光剥蚀斑束直径为35μm,脉冲频率10Hz,脉冲能量0.155~0.160mJ,激光剥蚀样品的深度为20~40μm。等离子质谱参数:冷却气流速(Ar) 为16.92L/min,辅助气流速(Ar)为0.8 L/min,载气流速(He)为0.637 L/min,样品气流速(Ar)为0.769 L/min,射频发生器功率1090W。其他参数:采样时间202Hg、204Pb 是2ms,其他是5ms,每峰点数100,检测器模式238U、232Th 用模拟,其他是计数,剥蚀时间40s;单个样品点数据包括20s 空白信号及40s 样品信号;每分析10 个样品点,分析锆石标准样品GJ-1 及质量监控样品Plesovice 各2 次[12]。年龄加权平均值计算、U-Pb 谐和图等的绘制采用Isoplot(3.0 版)软件完成[13],单个数据的误差为1σ,年龄加权平均值误差为2σ,具95%的置信度。年轻锆石(寒武纪以后)采用206Pb/238U 年龄,古老锆石(前寒武纪)采用207Pb/206Pb 年龄[14]

    图  4  样品锆石U-Pb 年龄直方图
    Figure  4.  Detrital zircon U-Pb age histogram

    锆石CL 图像显示,锆石可分为2 类,第一类锆石(图 2-a,测点13、14、24、30)颗粒较小,具有明显的核-边结构,核部较宽,为50~120μm,发光明亮,有明显的岩浆结晶环带,边部较窄,一般小于15μm,极少数为30μm 左右(图 2-a,测点13),发光微弱,无明显的环带结构;第二类锆石无核-边结构,锆石颗粒较大,呈深灰色板状,隐约可见环带结构,边部环带清楚,其中锆石颗粒中部较脏,可能是后期热液溶蚀加上变质变形作用造成的。

    图  2  哀牢山深变质岩系(哀牢山岩群)样品SM-15、SM-22、SM-18 及邻区浅变质岩系NO-1 锆石阴极发光(CL)图像
    a—花岗质片麻岩SM-15;b—花岗闪长质片麻岩SM-22;c—浅变粒花岗岩SM-18;d—石英云母片岩NO-1
    Figure  2.  Cathodoluminescence (CL) images of zircons with analyzed spots and ages from the metamorphic rocks

    测年结果显示,其锆石年龄由2 组构成(图 3)。第一类锆石共计4 个点,其中点23 由于谐和度较差未参与计算,剩余3 个点中锆石的核部Th/U 值介于0.2~2.4 之间,为典型的岩浆锆石,年龄集中在722~740Ma 之间,具体的同位素比值及年龄结果见表 1图 3-a;第二类锆石共计26 个点,其中15 个点的谐和度较差未参与计算,剩余11 个点锆石Th/U 值普遍介于0.01~0.1 之间(测点4 的Th/U 为0.16),Th/U<0.1,为典型的变质锆石,年龄集中于29Ma左右。

    图  3  哀牢山变质岩系锆石U-Pb 谐和图
    Figure  3.  U-Pb concordia diagrams and weighted average age from the metamorphic rocks in Ailaoshan area

    根据锆石的CL 图像,可将锆石分为3 类:第一类锆石颗粒较大,大于100μm,具有较大的长宽比值,最大可达7∶1,外形特征为细长柱状或针状,晶棱尖锐,自形,平直棱柱面发育,具有亮色的阴极发光和窄的振荡环带(图 2-b)。研究表明,在低温条件下微量元素的扩散速度慢,易形成较窄的岩浆环带(如I 型和S 型花岗岩中的锆石)[15],说明该类锆石可能形成于后期相对较低的温度下;第二类锆石(测点9、12、21、25、30)除具备第一类锆石的特征外,还具有继承锆石的残留核,核部发光性强,边部具有环带结构,可能为后期变质重结晶作用形成的;第三类锆石为短柱状或圆饼状,具有明显的核-边结构,核部较宽,为50~60μm,发光明亮,有明显的岩浆环带,边部较窄,一般小于10μm(测点4、10、22、24、27),发光微弱,无环带结构。测年结果显示,其年龄由2 组构成(图 3),其中第一类锆石的19 个测点和第二类锆石中测点25 的边部可归为后期岩浆作用形成的,锆石的Th/U 值介于0.4~2.1 之间,为典型的岩浆锆石,锆石的UPb年龄集中在26~32Ma 之间;第二类锆石的核部(测点9、12、21、30)与第三类锆石的核部可归为早期岩浆作用形成的,锆石的Th/U 值介于0.11~0.97之间,也为岩浆锆石,由于测点10、11、21、22 谐和度较差,未参与计算,其余锆石的U-Pb 年龄集中在223~243Ma 之间,U- Pb 年龄加权平均值为232.3±4.3Ma,同位素比值及锆石U-Pb 定年结果见表 1图 3-b

    表  1  哀牢山变质岩系LA-ICP-MS 锆石U-Th-Pb 同位素测定结果
    Table  1.  LA-ICP-MS zircon U-Th-Pb data of the metamorphic rocks in Ailaoshan area
    点号锆石特征分析部位同位素比值同位素年龄/Ma年龄/Ma同位素含量/10-6
    207Pb/206Pb206Pb/238U207Pb/235U207Pb/206Pb207Pb/206U206Pb/238U207Pb/235U ThU
    样品SM-15 花岗质片麻岩
    1环带环带0.13960.00290.004890.00010.094530.0022222353219221103039
    2板状板状0.047990.00110.004730.00010.030120.00198543013011234629
    3环带环带0.051040.00130.004620.00010.030250.001243573013012964685
    4板状板状0.04820.00100.004120.00010.026750.00110948271271300619032
    5环带环带0.049760.00110.004240.00010.027890.00118452271281382357
    6环带环带0.049590.00140.004590.00010.029670.00117663301301181594
    7环带环带0.047590.00100.004870.00010.031420.00178503113111193540
    8环带环带0.048310.00110.004570.00010.030650.001115522913112025860
    9环带环带0.0590.00180.004250.00010.038550.00156765271381412013
    10环带环带0.048760.00100.004530.00010.029660.001136502913016006150
    11环带环带0.106750.00220.004520.00010.079030.0021745372917728739742
    12环带环带0.047570.00100.004890.00010.031030.0017749321311100613060
    13核-边0.066780.00150.118960.00281.036850.030831477251672215536217
    14核-边0.069360.00150.118560.00271.217740.03191043722168091478137
    15环带环带0.069860.00150.004550.00010.045180.001924422914511794324
    16板状板状0.053990.00110.004720.00010.030280.0013704730130179013044
    17环带环带0.051210.00110.004360.00010.028020.001250492812814266005
    18环带环带0.048350.00100.004830.00010.031480.001116493113211465291
    19环带环带0.051070.00130.004220.00010.028920.00124459271291793909
    20环带环带0.051220.00120.004540.00010.030730.001251532913111865701
    21环带环带0.04880.00110.004260.00010.028930.001138532712913056003
    22环带环带0.054140.00130.003850.00010.027490.00137754251281993555
    23核-边0.064070.00140.106070.00250.886890.02374445650146451235267
    24环带环带0.049920.00110.004360.00010.028780.00119149281291603502
    25环带环带0.048210.00100.004560.00010.029970.001110492913011814426
    26环带环带0.046340.00100.004660.00010.030080.00116503013011474676
    27环带环带0.050880.00120.004220.00010.028340.00123552271281422940
    28环带环带0.048990.00120.004250.00010.027130.001147552712711102924
    29环带环带0.048610.00110.004560.00010.030250.00112951291301442002
    30核-边0.06430.00130.121570.00281.071180.02675143740167391382370
    样品SM-15 花岗质片麻岩
    1环带环带0.050520.001310.004550.00010.029340.0008321959290.7290.85881568
    2环带环带0.050270.001930.004420.000110.028950.0011420887280.7291.1554448
    3板状板状0.049480.001510.004610.000110.029090.0009417170300.7290.918101099
    4核-边0.053220.001450.035540.000820.248530.00777338612255.12256.3320411
    5环带环带0.078950.00250.004090.00010.04490.00149117161260.6451.415031977
    6环带环带0.045470.002220.004620.000120.029460.001460.183300.8301.4358411
    7环带环带0.053530.002550.004740.000120.03070.00148351104310.8311.5494431
    8环带环带0.053960.001750.004630.000110.029970.0010236971300.7301.02061285
    9核-边0.053270.001220.037150.000840.261390.00686340512355.32365.5184616
    10核-边0.064480.001440.040870.000930.365330.00946758462585.83167.044394
    11板状板状0.050860.001110.023950.000540.163190.00408235501533.41543.6394667
    12核-边0.050770.001210.035220.000810.251380.00689231542235.02285.6365396
    13环带环带0.05170.002420.004450.000120.029750.00141272104290.7301.41154961
    14环带环带0.05160.001510.004330.00010.027710.0008626866280.7280.944172035
    15环带环带0.048410.001140.004450.00010.028850.0007512054290.7290.7431902
    16板状板状0.054410.002340.004530.000110.030490.0013338893290.7311.3299344
    17环带环带0.053310.002390.004050.00010.028830.0013134298260.7291.3623560
    18环带环带0.052870.001890.00410.00010.028790.0010732379260.6291.1938535
    19环带环带0.052680.002250.004890.000120.031130.0013531594310.8311.320381086
    20环带环带0.069210.004040.004350.000130.033380.00193905116280.8331.9365321
    21核-边0.051020.001080.040450.000920.285020.00696242482565.72555.593439
    22核-边0.053860.001210.016190.000370.119740.00305365501042.31152.866552
    23环带环带0.058070.002310.00510.000130.031980.001353285330.8321.3659606
    24核-边0.05170.00130.036580.000840.255060.00735272562325.32315.9184348
    25核-边0.050250.001390.004730.000110.030310.000920763300.7300.98791204
    26环带环带0.048250.001320.00410.00010.025990.0007711263260.6260.8809493
    27核-边0.050380.001060.037530.000850.264360.00641212482385.32385.2626645
    28环带环带0.047290.001120.004590.000110.02920.000776456300.7290.8363787
    29环带环带0.051230.002570.004580.000120.029950.00152251111300.8301.5470256
    30核-边0.055720.001170.038450.000870.278080.00673441462435.42495.469466
    样品SM-18 变粒花岗岩
    2环带环带0.046770.001360.004160.00010.026630.000833768270.6270.8357675
    3环带环带0.061020.001250.003750.000090.032990.0007864043240.6330.816018931
    4环带环带0.04880.001070.004520.00010.028670.0007213851290.7290.77186249
    5环带环带0.049210.001080.004640.000110.029740.0007415850300.7300.719453916
    6环带环带0.047350.001070.00410.00010.026630.000686653260.6270.71172103
    7环带环带0.052210.001080.003580.000080.025980.0006229546230.5260.6163116956
    8环带环带0.046090.001260.004120.00010.026650.00079264270.6270.82323025
    9环带环带0.04650.001020.004310.00010.027850.00072351280.6280.73774513
    10环带环带0.057270.001330.004190.00010.030660.000850251270.6310.820034975
    11环带环带0.046850.001380.004270.00010.027290.000864169280.7270.91311810
    12环带环带0.04880.001050.004090.000090.027940.0006913950260.6280.710233242
    13环带环带0.048380.00110.004260.00010.028730.0007411853270.6290.71202014
    14环带环带0.048150.001210.004430.00010.029530.0008210759290.7300.81712804
    15环带环带0.048380.001060.003890.000090.02580.0006411851250.6260.66885468
    16环带环带0.04780.001120.004560.000110.029570.000788956290.7300.82892244
    17环带环带0.049990.001330.004250.00010.029220.0008519561270.6290.81252052
    18环带环带0.048510.00110.004260.00010.028960.0007412453270.6290.71473449
    19环带环带0.046740.001030.003890.000090.025920.000653651250.6260.620772723
    20环带环带0.046230.001020.004270.00010.027870.00071052280.6280.75105163
    21环带环带0.049370.001070.004590.000110.029060.0007216550300.7290.715083562
    22环带环带0.054380.001420.00390.000090.029670.0008538757250.6300.82602813
    23环带环带0.048630.001030.004290.00010.027610.0006713049280.6280.711827621
    24环带环带0.047270.001010.004280.00010.028090.000696250280.6280.73084610
    25环带环带0.04750.001210.004410.00010.028420.000797460280.7290.85632820
    26环带环带0.048760.001090.003910.000090.027610.000713752250.6280.712672411
    27环带环带0.048740.001040.004230.00010.02950.0007213650270.6300.71562593
    28环带环带0.056420.001190.003690.000090.029730.0007246847240.6300.7201715942
    29环带环带0.050870.00110.003780.000090.028710.0007123549240.6290.710588084
    30环带环带0.047610.001280.00420.00010.028760.000847964270.6290.8921604
    样品NO-1 变质砂岩
    1环带环带0.07270.00150.146890.00331.392840.0341006418841988614445469
    2核-边0.072620.00150.140540.00321.308380.033100342848188491499254
    3板状板状0.075980.00170.15950.00371.568730.0441095449542095818101122
    4核-边0.070970.00160.171920.00391.726660.0499574410232210191810998
    5环带环带0.051590.00110.03950.00090.28120.0072674825062526455426
    6环带环带0.060710.00130.098010.00220.807130.020629446031360111167253
    7环带环带0.074110.00150.168480.00391.683810.041104441100421100216151205
    8环带环带0.052320.00110.040250.00090.282470.0073004925462536307244
    9环带环带0.068910.00150.155560.00361.511020.04089643932209351678104
    10核-边0.06730.00140.128920.00301.159450.029847427821778213324243
    11环带环带0.061140.00130.107270.00250.899750.023644456571565212339256
    12核-边0.06750.00150.160310.00381.559390.04785346959219541927578
    13核-边0.065340.00140.14710.00351.382160.03878545885198811689111
    14环带环带0.051610.00110.040090.00090.279180.0072685025362506161165
    15环带环带0.052590.00120.038960.00090.275830.0073115024662476177168
    16核-边0.080240.00160.186760.00441.962380.049120340110424110317124159
    17板状板状0.050950.00120.03940.00090.281550.008239542496252665101
    18核-边0.117770.00240.311170.00734.566690.116192336174736174321230252
    19环带环带0.055010.00120.042740.00100.304670.0084124727062706269282
    20环带环带0.055680.00120.043660.00100.312360.0084394627662766214308
    21环带环带0.075140.00160.146110.00351.392290.0371072418792088616137305
    22板状板状0.088120.00180.231320.00552.740830.06713853813412913401860406
    23环带环带0.051920.00110.041890.00100.294580.0082824826562626202202
    24环带环带0.051890.00110.040140.00100.28530.0072814725462556251294
    25环带环带0.072880.00150.151320.00361.444560.0351011409082090814269664
    26核-边0.074370.00150.178650.00431.82280.0471052411060241054172111167
    27环带环带0.051050.00120.040410.00100.28340.0082435225562536498303
    28环带环带0.064020.00130.100420.00240.836990.02174242617146181195201
    29环带环带0.061760.00120.102270.00250.86030.021666426281563011141480
    30环带环带0.054020.00120.039560.00100.281730.008372502506252672109
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    花岗岩SM-18 的锆石粒度较大,CL 图像显示具典型的岩浆结晶环带,无继承性核、无变质增生边(图 2-c),属岩浆结晶产物。对样品进行了30 个点的U-Th-Pb 同位素测定,获得的同位素比值及年龄结果见表 1图 3-c,其中18 个点(点1、3、4、5、7、10、12~16、19、21、22、25、26、28、29)由于谐和度差,不参与计算,其余12 个点的投影均分布在U-Pb谐和线上(图 3-c),12 个分析点的206Pb/238U 年龄加权平均值为27.19±0.36Ma(MSWD=0.48),代表锆石结晶年龄。该年龄与样品SM-15、SM-22 中第一类锆石和第二类锆石的边部年龄接近,反映脉体形成可能与区域混合岩化有关。

    样品NO-1中锆石呈次圆状和次棱角状,多数保持较自形的棱柱状(图 2-d),其大小为50~150μm,具有振荡环带,其中少数几颗锆石具有均一的内部结构或核边结构(多为残留核)。选取30 个点进行测试,其同位素比值及年龄结果见表 1,其中测点22和29 的Th/U 值介于0.1~0.2 之间,可能为变质成因,其余锆石的Th/U 值均大于0.4。以上特征表明,锆石可能遭受了沉积作用的磨损,但仍为典型的岩浆锆石。对30 个点进行统计分析,其年龄可分为4 组(图 3):246~276Ma(n=11)、600~800Ma(n=5)、800~1000Ma(n=9)和1000Ma 以上(n=5);最老的锆石年龄测点18 的年龄值为1922.7Ma,其中第一组年龄较为集中,且投影点均分布在U-Pb 谐和线上(图 3-d),显示出很好的谐和度,锆石U-Pb 年龄加权平均值为252.5±4.7Ma(MSWD=0.087,n=6),其余的年龄值较为分散,且谐和度较差。

    关于哀牢山群的形成时代一直是地质界关注的热点,关系着区域地质构造演化等重大地质问题,但迄今为止,并未得到一致的看法。最早在1945 年黄汲清的《中国主要地质单位》[15]一书中,曾把哀牢山变质带称之为红河结晶片岩带,并推论其可能由太古宙花岗岩及片麻岩组成,但是并未获得确切的资料加以证实。云南区测队1965 年将沿哀牢山分布的一套混合岩化强烈的变质岩系命名为哀牢山岩群,并将其时代定为前奥陶纪,云南第二区测队1970 年将其归于元古宙[4];随后不同学者依据Sm-Nd、40Ar/39Ar、K-Ar 法等获得了一些年龄较大的数据,如斜长角闪岩Sm- Nd 模式年龄为1971.9Ma、1958.3Ma 和1672.2Ma,石榴辉石岩40Ar/39Ar 年龄为1710.3±2.4Ma[17-18]。中国科学院地质研究所用Rb-Sr 法测得年龄为839±73.9Ma,K-Ar 法年龄值为1360Ma 和1393Ma[19]。依据上述同位素测年结果,将哀牢山岩群的形成时间暂定为元古宙,并作为扬子板块的基底。但笔者认为,上述年龄值范围较宽,且精度较差,解释多样。此外,由于造山作用的强烈改造,加之强的混合岩化作用,岩石普遍片理化或劈理化,导致大多数地层的原有序列遭受破坏,一些岩体由于经历了高级变质作用而被误认为是前寒武纪基底岩石。最近也有部分学者依据锆石U-Pb 测年获得的相关数据,对哀牢山岩群的形成时代提出了质疑,认为其形成时代不全是元古宙,也不全属于扬子地台的结晶基底[6-8]

    本文采用锆石U-Pb 测年法对哀牢山岩群的原岩形成时代进行了研究,其中样品SM-15 中第一类锆石核部、样品SM-22 中第二类锆石和第三类锆石的核部年龄可代表哀牢山岩群原岩的形成时代。锆石U-Pb 测年结果显示,样品SM-15 中第一类锆石较少,仅有4 颗,其中测点23 由于谐和度较差,未参与计算,剩余3 点年龄集中于722~740Ma 之间,年龄加权平均值为729±18Ma(NSWD=0.34,n=3),可代表原岩的形成时代,属于新元古代;SM-22 中第二类锆石与第三类锆石的核部U-Pb 年龄加权平均值为235±10Ma,属于三叠纪。

    样品NO-1 中碎屑锆石测年结果显示,其年龄可分为4 组:246~276Ma、600~800Ma、800~1000Ma、1000Ma 以上;最老锆石年龄为1922.7Ma,为古元古代。其中第一组年龄较为集中,其余各组年龄较为分散,不具有指示意义,只能说明NO-1 中可能存在元古宙的岩石。第一组锆石U-Pb 年龄加权平均值为252.5±4.7Ma,为晚二叠纪,而碎屑锆石的最小年龄可代表沉积岩的下限年龄,即沉积岩的沉积时代,因此252.5±4.7Ma 可代表变质砂岩的形成时代;而在1∶20 万墨江幅地质图上标注的是T3?(图 1-b),笔者认为该变质砂岩形成时代应早于晚三叠世,为晚二叠世—早三叠世;此外由于碎屑锆石呈次圆状和次棱角状,指示较差的分选磨圆和较近的源区,推断其可能来源哀牢山岩群,因此哀牢山岩群中也应包括NO-1 中锆石的4 组年龄。

    综上可以看出,哀牢山岩群中既有元古宙,又有二叠纪—三叠纪的岩浆岩或地层,哀牢山深变质岩带(哀牢山岩群)至少在元古宙和二叠纪末—三叠纪初各发生一期构造-岩浆事件,其中又以235~255Ma 为主,这一年龄与最近一些学者在哀牢山构造带中获得的年龄较为接近[20-23],说明构造带在二叠纪末—三叠纪初受印支运动的影响,经历一期空间上广泛分布的构造-岩浆活动,同时可能导致哀牢山古特提斯洋盆或弧后盆地的基本闭合。此外,这一构造-岩浆活动时间(235~255Ma)与二叠纪2次生物灭绝事件在时间上存在耦合关系,其与生物灭绝间的关系有待进一步研究。

    前已述及,SM-15 中第二类锆石和SM-22 第一类与第二类锆石测点25 的边部年龄可指示哀牢山岩群的主变质时代,样品SM-18 采自同变形的长英质脉体中,其锆石年龄也指示变质变形时代,且上述3 件样品中该类锆石占各自全部锆石的比例较大,说明该期变质变形作用可能为哀牢山岩群的变质峰期或主变质期,其测年结果分别为SM-15 为29.9 ± 0.5Ma;SM- 22 为29.2 ± 0.4Ma;SM- 18 为27.19±0.36Ma,与近期研究成果较为符合[6-7],且这些变质年龄主要集中在27~32Ma 之间,与哀牢山-红河韧性剪切带左行走滑剪切的主要时代(30Ma 左右)较一致[24-26],同时也与喜山运动的第一幕发生间大致吻合(始新世末期—渐新世初期),说明喜山运动与哀牢山-红河剪切带的左行走滑运动之间存在必然联系,符合前人的观点[10]。综上笔者认为,哀牢山岩群的主变质时代发生在27~32Ma,现今所见的哀牢山岩群可能是由地质历史上浅变质或未变质的地层和岩浆岩在该时期发生强烈的变质变形作用而形成的[6],其变质变形作用可能归因于喜山运动。

    (1)哀牢山岩群至少包括元古宙岩浆岩(722~740Ma)、二叠纪末—三叠纪初岩浆岩或地层(235~255Ma),以及古近纪—新近纪岩浆岩(27~32Ma),至少经历了3 期构造-岩浆活动,是一个复杂的变质岩带,而不是以往认为的全部属于元古宙。

    (2)哀牢山岩群的主变质时代集中在27~32Ma之间,现今的哀牢山岩群面貌主要是由于地质历史上的浅变质或未变质的地层和岩浆岩在该时期发生强烈的变质变形作用而形成的,以往研究把哀牢山岩群全部归为前寒武纪扬子板块的变质结晶基底是不妥当的,其构造归属有待进一步研究。

    (3)哀牢山岩群西侧浅变质岩系中的变质砂岩,最大沉积时代为252.5±4.7Ma,为晚二叠世—早三叠世,而不是1∶20万墨江幅地质图标注的晚三叠世。

    致谢: 锆石Hf 同位素分析过程中得到中国地质科学院国土资源部成矿作用与资源评价重点实验室郭春丽副研究员的指导,成文过程中得到中国地质大学(北京)曹晶博士和王赛硕士的帮助与指导,在此一并表示衷心的感谢。
  • 图  1   冀东地区区域地质及金矿床分布简图(据参考文献[2]修改)

    1—中侏罗统;2—古生界;3—中、新元古界;4—太古宙遵化-青龙变质杂岩;5—燕山期花岗岩;6—印支期花岗岩;7—断裂;8、9、10、11—金矿床规模(大、中、小、矿点)

    Figure  1.   Simplified regional geological map showing distribution of gold deposits in eastern Hebei

    图  2   金宝沟金矿矿区地质略图(据参考文献①( ① 高军辉,甘先平,张宝琛,等. 河北省平泉县下营坊矿区金矿详查 报告.2012.)修改)

    1—第四系;2、3、4—长城系高于庄组白云质灰岩、大红峪组砂质白云岩、常州沟组石英砂岩;5—太古宇变质岩;6—花岗斑岩;7—流纹斑岩脉;8—石英二长斑岩脉;9—闪长岩脉;10—石英正长斑岩脉;11—构造角砾岩;12—金矿体;13—地层产状;14—正断层;15—逆断层;16—采样位置

    Figure  2.   Geological sketch map of the Jinbaogou gold deposit

    图版Ⅰ   a.花岗斑岩野外露头;b、c.花岗斑岩手标本;d.花岗斑岩中石英、钾长石斑晶(正交偏光);e、f.花岗斑岩中的石英、钾长石、黑云斑晶(正交偏光)。Qtz—石英;Kfs—钾长石;Bt—黑云母

    图  3   金宝沟花岗斑岩锆石阴极发光图像

    (图中两排数据分别为锆石206Pb/238U 年龄值和相应的εHf (t)值)

    Figure  3.   Zircon CL images of granite porphyry in the Jinbaogou gold deposit

    图  4   金宝沟花岗斑岩锆石U-Pb 谐和图

    Figure  4.   U-Pb concordia diagram of zircon in Jinbaogou granite porphyry

    图  5   金宝沟花岗斑岩的SiO2-K2O 图解[23]

    Figure  5.   SiO2 versus K2O diagram of Jinbaogou granite porphyry

    图  6   金宝沟花岗斑岩A/CNK-A/NK 图解[24]

    Figure  6.   A/CNK versus A/NK diagram of Jinbaogou granite porphyry

    图  7   金宝沟花岗斑岩体稀土元素球粒陨石标准化分布型式图(a)和微量元素原始地幔标准化蛛网图(b)(标准值据参考文献[22])

    Figure  7.   Chondrite-normalized REE patterns (a) and primitive mantle-normalized trace element spidergram (b) of Jinbaogou granite porphyry

    图  8   金宝沟花岗斑岩锆石Hf 同位素组成εHf (t) 和两阶段模式年龄TDM2柱状图

    Figure  8.   Zircon Hf isotopic compositions and TDM2 of Jinbaogou granite porphyry

    图  9   金宝沟花岗斑岩SiO2-Ce 和Zr-TiO2判别图

    Figure  9.   SiO2 versus Ce and Zr versus TiO2 diagrams of Jinbaogou granite porphyry

    图  10   金宝沟花岗斑岩t-176Hf/177Hf 和tHf (t) 图解[38]

    Figure  10.   176Hf/177Hf versus t and εHf versus t diagrams of Jinbaogou granite porphyry

    图  11   金宝沟花岗斑岩岩浆形成压力判别图解[47]

    Figure  11.   Discrimination diagram of pressure of Jinbaogou granite porphyry

    图  12   金宝沟花岗斑岩构造环境判别图及Rb/30-Hf-3Ta 图解[71]

    VAG—火山弧花岗岩;ORG—洋中脊花岗岩;WPG—板内花岗岩;syn-COLG—同碰撞花岗岩;

    Figure  12.   Tectonic setting discrimination diagram and Rb/30- Hf-3Ta diagram of Jinbaogou granite porphyry

    表  1   金宝沟花岗斑岩LA-ICP-MS 锆石U-Th-Pb 同位素定年结果

    Table  1   LA-ICP-MS zircon U-Th-Pb dating of Jinbaogou granite porphyry

    点号元素含量/10-6Th/U同位素比值同位素年龄/Ma
    ThPbU206Pb/238U207Pb/235U207Pb/206Pb206Pb/238U207Pb/235U207Pb/206Pb
    样品B107-JBG
    111272700.410.0263±0.00010.1827±0.00600.0505±0.0016167±1170±6216±75
    211272340.480.0266±0.00020.1854±0.00630.0506±0.0017169±1173±6222±77
    3158103490.450.0262±0.00010.1798±0.00380.0497±0.001167±1168±4180±49
    4120182200.540.0428±0.0012.3059±0.12670.3906±0.0103270±61214±673873±40
    510962200.500.0267±0.00020.1847±0.00690.0502±0.0018170±1172±6202±85
    6244163610.670.0318±000020.8190±0.02220.1865±0.0041201±1608±162712±36
    712062200.550.0267±0.00020.1858±0.00860.0505±0.0021170±1173±8218±97
    8200103440.580.0271±0.00010.1840±0.00440.0492±0.0012172±1171±4157±56
    925893220.800.0270±0.00020.1831±0.00460.0491±0.0012172±1171±4153±55
    107081750.400.0324±0.00030.9383±0.03940.2098±0.0071206±2672±282904±55
    1195101760.540.0369±0.00051.4153±0.05860.2784±0.0082233±3895±373354±46
    12159422040.750.0844±0.00177.5229±0.21550.6461±0.0086523±112176±624615±19
    1318972700.700.0271±0.00020.1845±0.00570.0494±0.0015172±1172±5168±70
    147871640.470.0317±0.00020.8144±0.02300.1865±0.0046201±1605±72712±41
    1517282930.590.0270±0.00030.3926±0.01760.1054±0.0035172±2336±151721±60
    1613672450.550.0268±0.00020.1864±0.00700.0504±0.0019171±1174±7213±87
    17165692940.560.0918±0.00158.3788±0.21240.6618±0.0082566±92273±584650±18
    1810752020.530.0268±0.00020.1818±0.01030.0491±0.0027171±1170±10154±131
    1911872420.490.0267±0.00020.1829±0.00700497±0.0018170±1171±6180±85
    2012361990.620.0267±0.00020.1838±0.00910.0499±0.0024170±1171±8188±113
    219451750.540.0265±000020.2473±0.00950.0678±0.0025168±1224±9862±76
    2211762310.510.0266±0.00010.1803±0.00660.0491±0.0018169±1168±6154±84
    237241250.570.0266±0.00020.2951±0.01210.0803±0.029169±12263±111206±71
    2416451471.120.0265±0.00030.1857±0.02360.0508±0.0065169±2173±22231±195
    样品B115-JBG
    18241490.550.0263±0.00020.3305±0.01340.0913±0.0035167±1290±121452±73
    213651770.770.0251±0.00020.1725±0.00910.0499±0.0025160±1162±8189±117
    313261940.680.0263±0.00020.3247±0.01240.0894±0.0032168±1286±111413±69
    410461990.520.0265±0.00020.3393±0.01170.0930±0.0030168±1297±101488±60
    511682360.490.0268±0.00020.4237±0.02650.1147±0.0059171±1359±221874±93
    610772190.490.0268±0.00020.3807±0.01060.1029±0.0026171±1328±91676±46
    77041550.450.0258±0.00020.1836±0.01070.0516±0.0029164±1171±10269±128
    814062250.620.0268±0.00020.1832±0.00810.0496±0.0020170±1171±8178±92
    911451930.590.0265±0.00020.1842±0.00400.0505±0.0010168±1172±4217±47
    1012251820.670.0267±0.00020.1824±0.00750.0495±0.0017170±1170±7170±82
    1112562370.530.0261±0.00020.1850±0.01090.0514±0.0024166±2172±10258±105
    1220793270.630.0263±0.00010.1834±0.00520.0506±0.0013167±1171±5225±61
    138041620.490.0270±0.00020.1828±0.00480.0491±0.0011172±1170±5152±54
    14372760.490.0267±0.00020.1829±0.01750.0496±0.0048170±1171±16177±224
    159351790.520.0266±0.00020.1875±0.00620.0511±0.0015169±1174±6245±66
    16368112291.610.0329±0.00030.6904±0.02520.1520±0.0045209±2533±192369±50
    178041500.530.0268±0.00020.1827±0.00600.0495±0.0016170±1170±6170±75
    188541570.540.0264±0.00020.1834±0.00890.0503±0.0024168±1171±8209±110
    196831150.600.0265±0.00020.1821±0.01230.0499±0.0034168±1170±11189±158
    2011351620.700.0274±0.00020.1808±0.00830.0478±0.0022175±1169±889±107
    214831030.460.0276±0.00030.1842±0.01470.0484±0.0029176±2172±14117±140
    2217472250.770.0279±0.00020.1826±0.00620.0474±0.0016177±1170±671±80
    2311081730.640.0316±0.00020.7218±0.01360.1656±0.0028201±1552±102514±28
    2415472080.740.0277±0.00020.1834±0.00720.0480±0.0017176±1171±7100±86
    下载: 导出CSV

    表  2   金宝沟花岗斑岩主量、微量和稀土元素分析结果

    Table  2   Major, trace and rare earth elements analyses of Jinbaogou granite porphyry

    样品号B3-JBGB5-JBGB9-JBGB106-JBGB107-JBGB110-JBGB115-JBG
    SiO270.2576.8874.9272.0867.3370.0465.4
    Al2O314.913.2313.9513.7414.1414.2415.05
    CaO0.870.070.271.060.960.381.33
    Fe2O30.450.150.521.272.691.673.15
    MgO0.470.180.190.450.480.470.97
    MnO0.060.030.050.060.230.050.42
    K2O6.235.654.535.797.075.455.15
    Na2O1.791.374.071.650.022.530.01
    P2O50.070.010.020.070.070.070.16
    TiO20.20.070.10.190.210.210.34
    LOI2.451.080.722.984.493.315.82
    Total97.7498.7299.3499.3497.6998.4297.8
    K2O/Na2O2.292.710.730.010.010.010.03
    K2O+Na2O8.027.028.67.447.097.985.16
    A/CNK1.321.561.151.221.121.091.33
    La33.39.1512.326.923.529.312.8
    Ce60.515.324.852.649.455.837.5
    Pr6.422.122.695.174.785.555.01
    Nd22.406.958.4318.116.71920.5
    Sm4.021.011.342.822.772.873.74
    Eu0.770.190.230.650.70.690.73
    Gd2.510.870.991.972.372.233.06
    Tb0.370.130.150.330.310.310.4
    Dy2.390.780.811.751.711.842.29
    Ho0.440.170.160.360.370.380.48
    Er1.290.520.481.0111.011.28
    Tm0.220.110.090.150.160.160.2
    Yb1.630.730.631.131.241.231.39
    Lu0.250.140.090.190.210.20.23
    Y15.88.138.039.889.4610.314
    Rb153187131140206137193
    Ba97772.8140102212391033255
    Th9.9710.25.777.86.88.644.57
    U4.722.941.351.581.812.642.3
    Ta0.961.21.010.620.570.630.56
    Nb11.614.214.510.39.191012.5
    La33.39.1512.326.923.529.312.8
    Ce60.515.324.852.649.455.837.5
    Sr16311.237.27488.1138106
    Nd22.46.958.4318.116.71920.5
    Zr266197288152167158214
    Hf8.716.728.714.54.654.665.25
    Sm4.021.011.342.822.772.873.74
    ΣREE136.5138.1753.19113.13105.22120.5789.61
    LREE/HREE1410.0614.6415.4213.2815.388.6
    (La/Yb)N14.658.991417.0813.5917.096.61
    δEu0.690.600.580.80.810.80.64
    δCe0.950.821.011.021.0811.15
    注:LOI 为烧失量;Total 为主量元素总和;A/CNK=(Al2O3)/(CaO+K2O+Na2O)摩尔分数比; 里特曼指数δ=(K2O+Na2O)2/(SiO2-43);球粒陨石、原始地幔数据据参考文献[22];主量元素含量单位为%,微量和稀土元素为10-6
    下载: 导出CSV

    表  3   金宝沟花岗斑岩锆石Hf 同位素分析结果

    Table  3   Zircon Hf isotopic composition of Jinbaogou granite porphyry

    点号年龄/Ma176Yb/177Hf176Lu/177Hf176Hf/177Hf176Hf/177Hf (t)εHf(0)εHf(t)TDM1/MaTDM2/MafLu/Hf
    样品B107-JBG
    11670.0378430.0014010.2824630.0000190.282459-3938.3-7.411271685-0.96
    21690.0393390.0014440.2823420.0000200.282337-3936.6-11.713011956-0.96
    31670.0381440.0013850.2823980.0000190.282394-3937.4-9.712191831-0.96
    51700.0359370.0012830.2824130.0000210.282409-3937.6-9.111951796-0.96
    71700.0272970.0010080.2823470.0000190.282344-3936.6-11.412771940-0.97
    81720.0347160.0012610.2823680.0000200.282364-3936.9-10.612571894-0.96
    91720.0343330.0012730.2823080.0000190.282304-3936.1-12.813422028-0.96
    131720.0298540.0011160.2823440.0000170.282341-3936.6-11.512861946-0.97
    161710.0379940.0014250.2824440.0000190.282439-3938.0-8.011551727-0.96
    181710.0272750.0010360.2823390.0000190.282335-3936.5-11.712911959-0.97
    191700.0332280.0012360.2823490.0000200.282345-3936.7-11.412831938-0.96
    201700.0346340.0012800.2824040.0000180.282400-3937.4-9.412061814-0.96
    221690.0277900.0010550.2823410.0000190.282338-3936.6-11.612881955-0.97
    241690.0457910.0016520.2823720.0000210.282367-3937.0-10.612641889-0.95
    B115-JBG
    71640.0305010.0011630.2823520.0000230.282348-3936.7-11.412771935-0.96
    81700.0344510.0013300.2823370.0000210.282333-3936.5-11.813031964-0.96
    91680.0318580.0012360.2824200.0000240.282416-3937.7-8.911831780-0.96
    101700.0407540.0016320.2822640.0000260.282259-3935.5-14.414172130-0.95
    111660.0378770.0014430.2823420.0000210.282338-3936.6-11.713001957-0.96
    121670.0377390.0014280.2823220.0000200.282318-3936.3-12.413272000-0.96
    131720.0245070.0010040.2823890.0000180.282386-3937.2-9.912191846-0.97
    141700.0284990.0011750.2824220.0000200.282419-3937.7-8.811781773-0.96
    151690.0310580.0012820.2824150.0000190.282411-3937.6-9.011911790-0.96
    171700.0313010.0012750.2823400.0000180.282336-3936.5-11.712971958-0.96
    181680.0214090.0008620.2823180.0000190.282315-3936.2-12.513142006-0.97
    191680.0316100.0012820.2823640.0000210.282360-3936.9-10.912631905-0.96
    201750.0336580.0013840.2823360.0000190.282332-3936.5-11.713061964-0.96
    211760.0258310.0010520.2823680.0000210.282364-3936.9-10.612511891-0.97
    221770.0276720.0011350.2823110.0000190.282307-3936.1-12.513332017-0.97
    241760.0317110.0012920.2823260.0000190.282322-3936.3-12.113181986-0.96
    注:εHf (t)={[(176Hf/177Hf)s-(176Lu/177Hf)s×(eλt-1)]/[(176Hf/177Hf)CHUR,0-(176Lu/177Hf)CHUR×(eλt-1)]-1}×10000;TDM1=1/λ×ln{1+[(176Hf/177Hf)s-(176Hf/177Hf)DM]/[(176Lu/ 177Hf)s-(176Lu/177Hf)DM];TDM2=1/λ×ln{1+[(176Hf/177Hf)s,t-(176Hf/177Hf)DM,t]/[(176Lu/177Hf)C-(176Lu/ 177Hf)DM]}+t;(176Lu/177Hf)s和(176Hf/177Hf)s为样品测定值;(176Hf/177Hf)CHUR,0=0.282772,(176Lu/177Hf)CHUR =0.0332,(176Hf/177Hf)DM=0.28325,(176Lu/177Hf)DM=0.0384;λ=1.867×10-11a-1,(176Lu/177Hf)C=0.015,t=锆石结晶年龄
    下载: 导出CSV
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出版历程
  • 收稿日期:  2015-09-16
  • 修回日期:  2016-02-24
  • 网络出版日期:  2023-08-16
  • 刊出日期:  2016-04-30

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