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青海阿木尼克山地区牦牛山组火山岩地球化学特征、锆石U-Pb年龄及其地质意义

寇贵存, 冯金炜, 罗保荣, 周维贵, 柳树权

寇贵存, 冯金炜, 罗保荣, 周维贵, 柳树权. 2017: 青海阿木尼克山地区牦牛山组火山岩地球化学特征、锆石U-Pb年龄及其地质意义. 地质通报, 36(2-3): 275-284.
引用本文: 寇贵存, 冯金炜, 罗保荣, 周维贵, 柳树权. 2017: 青海阿木尼克山地区牦牛山组火山岩地球化学特征、锆石U-Pb年龄及其地质意义. 地质通报, 36(2-3): 275-284.
KOU Guicun, FENG Jinwei, LUO Baorong, ZHOU Weigui, LIU Shuquan. 2017: Zircon U-Pb dating and geochemistry of the volcanic rocks from Maoniushan Formation in Amunike area, Qinghai Province, and its geological implications. Geological Bulletin of China, 36(2-3): 275-284.
Citation: KOU Guicun, FENG Jinwei, LUO Baorong, ZHOU Weigui, LIU Shuquan. 2017: Zircon U-Pb dating and geochemistry of the volcanic rocks from Maoniushan Formation in Amunike area, Qinghai Province, and its geological implications. Geological Bulletin of China, 36(2-3): 275-284.

青海阿木尼克山地区牦牛山组火山岩地球化学特征、锆石U-Pb年龄及其地质意义

基金项目: 

中国地质调查局项目《柴达木周缘及邻区成矿带地质矿产调查评价》下属研究项目《青海省都兰县阿木尼克山地区J47E017001、J47E018001、J47E018002、J47E019003 四幅1∶5 万区域地质矿产调查》 编号:1212011221146

详细信息
    作者简介:

    寇贵存(1992-),男,在读硕士生,矿物学、岩石学、矿床学专业。E-mail:kgc1992@126.com

    通讯作者:

    冯金炜(1991-),男,在读硕士生,矿物学、岩石学、矿床学专业。E-mail:fengjw1991@163.com

  • 中图分类号: P588.14;P597+.3

Zircon U-Pb dating and geochemistry of the volcanic rocks from Maoniushan Formation in Amunike area, Qinghai Province, and its geological implications

  • 摘要:

    利用岩石地球化学分析和LA-ICP-MS锆石U-Pb定年方法,对阿木尼克山地区牦牛组火山岩进行了系统的地球化学特征和锆石U-Pb年代学研究。其地球化学特征为,SiO2含量介于53.94%~64.69%之间,全碱含量介于5.38%~9.86%之间,范围较大,里特曼指数介于1.45~4.54之间,属于碱性岩和钙碱性岩,铝饱和指数A/CNK均大于1.1,具有S型花岗岩的特征;稀土元素总量为68×10-6~372×10-6,LREE/HREE值介于4.51~18.25之间,轻稀土元素富集,重稀土元素亏损,稀土元素配分曲线右倾;微量元素中不相容元素Rb、Ba、Th富集,Ta、Nb亏损明显,蛛网曲线呈现峰谷迭起的曲线形式。锆石CL图像和U-Pb同位素分析结果显示,牦牛山组火山岩锆石自形程度好,均有岩浆振荡环带的特征,Th/U值介于0.4~1.3之间,属于岩浆成因锆石。测得该火山岩中2件样品的锆石206Pb/238U 年龄介于371~399Ma 之间,年龄加权平均值分别为374.8±3.1Ma 和392.4±3.3Ma,表明火山岩形成时代为中—晚泥盆世。结合区域特征,认为牦牛山组火山岩的形成与柴达木盆地北缘的演化有关,其是后碰撞阶段伸展作用的产物。

    Abstract:

    Geochemical analysis and LA-ICP-MS zircon U-Pb dating were conducted for zircon grains and geochemical characteristics of the volcanic rocks from Maoniushan Formation in Amunike area. The geochemical characteristics show that the volcanic rocks form Maoniushan Formation have the following data: SiO2=53.94%~64.69%, total alkali content(ALK(Na2O+K2O))=5.38%~ 9.86%, varying in a large range, Rittmann Index(δ)=1.45~4.54, belonging to alkaline rocks and calc-alkaline rocks, and all of aluminum saturation indexes A/CNK are higher than 1.1, exhibiting characteristics of S type granite. Rare earth element analyses reveal that ΣREE=68×10-6~372×10-6,and LREE/HREE=4.51~18.25, exhibiting right-dipping REE patterns strongly enriched in LREE and depleted in HREE. Trace elements analyses reveal strong enrichment of incompatible elements Rb, Ba, Th and conspicuous depletion of Ta, Nb, assuming the curve form that cobweb curve appears frequently in peak and valley. CL investigations show that zircon grains from Maoniushan Formation are euhedral in shape and display fine-scale oscillatory zoning as well as Th/U ratio of 0.4~ 1.3, implying their magmatic origin. Zircon dating of two samples indicates 206Pb/238U age of 371~399Ma, weighted mean 206Pb/238U ages of 374.8±8.1Ma and 392.8±3.3Ma, which are interpreted to be the time of the formation of volcanic rocks. Therefore, it is suggested that the Maoniushan Formation should occur in the Middle-Late Devonian period. Combined with regional characteristics, it is concluded that the formation of volcanic rocks in Maoniushan Formation was related to the evolution of the northern area of the Qaidam Basin, and volcanic rocks were probably formed by lithospheric extension at the post-collision stage.

  • 中国东北地区位于西伯利亚板块、华北板块和西太平洋板块的交汇部位[1],由额尔古纳地块、兴安地块、松嫩地块、佳木斯地块、兴凯地块等造山微陆块(图 1-a)在古生代拼合而成[2-5]。大兴安岭包含额尔古纳地块、兴安地块和松嫩地块南西部(图 1-b),以发育巨量显生宙岩浆岩为典型特征,为研究东亚地区构造演化提供了天然的实验室。以往研究表明,大兴安岭显生宙岩浆活动可分为古生代和中生代2个阶段,其中古生代岩浆活动常作为古亚洲洋闭合的产物,标志中亚造山带东段构造演化的结束[2, 6-7];而中生代岩浆活动则与软流圈地幔上涌[8-9]和新生地壳的卷入[2, 10-15]密切相关。

    图  1  东北地区构造分区图(a)和主要地理单元(b)(据参考文献[2-3]修改)
    Figure  1.  Tectonic subdivision (a) and main geographical units in Northeast China(b)

    受大兴安岭中生代岩浆活动分布面积广、时间跨度大等因素制约,相关构造背景和动力学机制仍存有较多分歧,目前主要有3种主流观点:①幔柱模式[16-18]; ②蒙古-鄂霍茨克洋闭合及后碰撞造山模式[19-23];③古太平洋板块俯冲模式[7, 24-31]。大兴安岭中生代岩浆岩呈北东向展布,岩浆活动时间跨度可达70 Ma,且未见同时代OIB的发育,加之地震层析成像识别出板片状高速异常[32],因此,本区发育地幔柱的可能性较小。蒙古-鄂霍茨克洋的闭合常被认为发生于中侏罗世[19, 21],大兴安岭仅额尔古纳等少数区域受其控制。另外,据前人对东亚晚中生代岩浆活动的统计分析可知,自大兴安岭向松辽盆地、吉黑东部直至朝鲜半岛,中生代岩浆岩年龄呈现逐渐年轻的趋势[25],蒙古-鄂霍茨克洋的闭合及后造山拉伸很难造成如此宽广的影响。但若为古太平洋板块的西向俯冲的结果,那古太平洋板块是如何俯冲如此远的距离(大于2000 km)触发额尔古纳等地区大规模的钙碱性系列岩浆活动,而对松辽盆地及其东部地区无明显影响呢?

    基于此,本文详细研究大兴安岭北段吉峰地区火山岩-花岗岩岩石学、年代学和地球化学特征,并结合大兴安岭及其邻区晚中生代岩浆岩的成岩时代、岩石成因类型及其空间展布规律,深入探讨大兴安岭及其邻区中生代构造演化特征及动力学机制。

    吉峰地区火山-侵入杂岩体位于大兴安岭北段金河-三望山火山喷发带金河火山岩盆地和阿南林场火山岩盆地,大地构造位置属兴安地块鄂伦春褶皱带(图 1图 2-a)。区内植被茂密、露头条件不佳,仅出露秀山、旭光等小型花岗岩体,而广泛发育大面积中生代火山岩地层,两者呈侵入接触关系(图 2-b)。

    图  2  大兴安岭北段(a)(据参考文献[32]修改)和吉峰地区地质图(b)(据参考文献修改)
    Figure  2.  Geological map of the middle part of the Da Hinggan Mountains(a)and Jifeng area(b)

    吉峰花岗岩主要为二长花岗岩和石英二长斑岩。二长花岗岩主要由长石(约70%)、石英(约25%)和黑云母(约5%)组成,其中斜长石粒度0.2~2 mm,轻微粘土化,碱性长石粒度一般为2~5 mm,可见文象结构,石英呈他形粒状,粒度0.2~2 mm,可见轻微波状消光(图 3-a)。二长斑岩斑晶由斜长石、少量钾长石和暗色矿物构成,粒度一般0.5~3.5 mm;基质由长石、石英、少量暗色矿物构成,粒度一般小于0.05 mm(图 3-b)。

    图  3  吉峰地区花岗质岩石岩石学特征
    a—二长花岗岩(+);b—石英二长斑岩(+);c—满克头鄂博组流纹岩(+);d—玛尼吐组熔结凝灰岩(-) Qtz—石英;Pl—斜长石;Kfs—钾长石;Bi—黑云母;Cry—晶屑;Det—岩屑;Hya—玻屑
    Figure  3.  Petrological characteristics of granitic rocks in Jifeng area

    火山岩地层主要为满克头鄂博组(J3mk)和玛尼吐组(J3mn)。满克头鄂博组流纹岩斑晶由斜长石、钾长石、石英、黑云母组成,粒度0.2~2.5 mm,其中斜长石多高岭土化和绢云母化,钾长石轻微高岭土化,石英部分被熔蚀呈浑圆状、港湾状,黑云母呈片状,多色性明显;基质由长石、石英组成(图 3-c)。玛尼吐组熔结凝灰岩由晶屑、岩屑、玻屑及少量火山尘组成,以小于2.0 mm的凝灰物为主。其中晶屑由长石、黑云母构成,可见熔蚀现象,且长石可见强绢云母化,黑云母长轴多定向排列;岩屑以塑性为主、刚性次之;玻屑呈蚯蚓状、细纹状等,均脱玻为隐晶状长英质,被少量粘土交代(图 3-d)。

    锆石挑选在河北省区域地质矿产调查研究所进行,将岩石样品粉碎至100 μm后,磁选和浮选出锆石精样,并在双目镜下手工挑选具代表性的锆石,粘靶、抛光和镀金后,在北京燕都中实测试技术有限公司进行阴极发光(CL)内部结构照相。LA-ICP-MS锆石U-Pb同位素定年使用布鲁克M90等离子质谱与NewWaveUP213深紫外激光剥蚀系统测定,束斑直径为30 μm,应用标准样GJ-1进行分馏校正,元素含量采用SRM610为外标,具体原理、测试条件及流程见参考文献[33]。LA-ICP-MS锆石U-Pb同位素数据列于表 1,误差为1σ,普通铅校正使用标定的240Pb,年龄加权平均值及谐和图采用Isoplot程序[34]完成。

    表  1  吉峰花岗质岩石LA-ICP-MS锆石U-Th-Pb定年数据
    Table  1.  LA-ICP-MS zircon U-Th-Pb age data of granitic rocks in Jifeng area
    分析点Pb/10-6Th/10-6U/10-6Th/U同位素比值年龄/Ma
    207Pb/235U206Pb/238U207Pb/206Pb207Pb/235U206Pb/238U207Pb/206Pb
    TW426,英安质熔结凝灰岩,18个测点年龄加权平均值为145.2±1.1 Ma,MSWD=1.4
    TW426-042.3357.4766.860.860.44500.02910.02430.00050.12840.0072373.820.51553.32076.898.2
    TW426-021.2934.3241.160.830.31230.01410.02430.00060.10520.0058275.910.9154.73.51718.2101.7
    TW426-072.2167.1269.670.960.22900.01000.02300.00040.07730.0040209.38.3146.82.71127.8103.2
    TW426-011.9553.8663.030.850.23090.01020.02340.00040.07670.0038210.98.5148.92.71114.598.2
    TW426-093.61142.07101.321.400.22840.01040.02310.00040.08010.0049208.98.6147.22.41199.1120.4
    TW426-052.86106.6182.761.290.22820.01070.02330.00040.07650.0039208.78.8148.42.61109.399.1
    TW426-081.8959.6963.840.940.22460.01080.02290.00050.07590.0040205.79.0146.32.91094.4106.0
    TW426-063.22113.4790.031.260.22660.00950.02350.00040.07460.0037207.47.8149.92.21057.493.5
    TW426-103.0496.7397.660.990.20840.01000.02300.00030.06900.0035192.28.4146.62.2901.9110.2
    TW426-032.8494.9486.751.090.20450.00960.02310.00040.06750.00321898.1147.42.3853.797.4
    TW426-01-12.95120.0892.551.300.16410.00570.02220.00030.05500.0020154.35.0141.31.741384.3
    TW426-03-13.34113.37105.891.070.16650.00510.02300.00020.05320.0017156.44.5146.51.5338.972.2
    TW426-07-13.15122.8198.271.250.16490.00550.02270.00020.05340.00181554.8144.81.5346.443.5
    TW426-05-12.2275.7875.251.010.16060.00610.02260.00030.05280.0022151.25.41441.7320.488.0
    TW426-04-12.66106.7884.301.270.15930.00570.02270.00030.05170.0018150.15.0144.91.7272.383.3
    TW426-10-13.07115.4399.191.160.15600.00560.02260.00020.05050.0018147.24.9144.31.5220.449.1
    TW426-02-12.85101.9194.981.070.14960.00530.02260.00030.04910.0018141.64.7143.91.6150.185.2
    TW426-06-13.21128.53104.891.230.15320.00490.02230.00020.05050.0017144.84.3142.11.5216.780.5
    TW426-08-12.8391.8995.320.960.15600.00520.02290.00020.05080.0018147.24.6145.71.4231.681.5
    TW426-09-12.61104.5781.181.290.15560.00570.02300.00030.05030.0019146.85.0146.41.7205.691.7
    TW3,流纹岩,16个测点年龄加权平均值为125.4±0.8 Ma,MSWD=0.36
    TW3-06-12.7346.94115.340.410.15820.00660.01990.00030.06070.0027149.25.81271.8627.896.3
    TW3-093.0576.01125.660.600.15630.00760.01970.00030.05930.0030147.46.7125.92.0588.9109.2
    TW3-03-13.4095.66137.310.700.15260.00580.01950.00030.05810.0022144.25.1124.51.660083.3
    TW3-09-13.8292.93152.110.610.15090.00560.01970.00020.05720.0023142.75.01261.5498.287.0
    TW3-02-12.9274.51113.790.650.15510.00570.02050.00030.05620.0021146.45.0130.91.9457.583.3
    TW3-064.70143.10183.690.780.14650.00530.01970.00030.05470.0020138.84.7125.61.6398.278.7
    TW3-04-13.1467.78128.150.530.14500.00590.01970.00020.05460.0023137.55.21261.6398.292.6
    TW3-07-14.94159.41186.530.850.14040.00480.01950.00020.05310.0019133.44.3124.31.4344.579.6
    TW3-024.38114.83176.930.650.14300.00570.01970.00030.05410.0022135.85.1125.71.7372.392.6
    TW3-10-14.5797.84187.070.520.14190.00520.01980.00020.05330.0021134.74.7126.51.6342.788.9
    TW3-013.71100.82152.500.660.13960.00690.01960.00030.05420.0028132.76.1124.81.8388.9118.5
    TW3-076.47225.87254.280.890.13520.00460.01930.00020.05140.0018128.84.1123.51.4257.584.3
    TW3-05-16.51234.01239.650.980.13700.00430.01970.00020.05140.0017130.43.9125.51.5257.577.8
    TW3-053.6995.75147.270.650.13850.00650.01990.00030.05240.0026131.75.8126.91.9301.9111.1
    TW3-01-14.75112.59194.060.580.13140.00470.01960.00020.04920.0018125.34.3125.31.4166.882.4
    TW3-045.03154.98194.500.800.13250.00520.01970.00030.04910.0019126.34.6125.61.6153.890.7
    TW3-084.18116.38168.970.690.13130.00550.01960.00030.04940.0021125.34.91251.6168.6100.0
    TW3-08-17.44249.24250.011.000.14620.00470.02190.00030.04890.0016138.54.2139.51.6142.774.1
    TW4,二长花岗岩,19个测点年龄加权平均值为125.5±1.8 Ma,MSWD=6.7
    TW4-06-12.2553.7391.690.590.16590.00720.01960.00030.06650.0034155.86.3125.32.0821.9100.9
    TW4-10-13.5587.37140.580.620.15690.00680.02010.00030.05770.00261485.9128.11.8520.496.3
    TW4-05-12.4755.0799.000.560.15830.00700.02030.00030.05930.0027149.26.2129.82.057698.1
    TW4-09-14.74112.86179.780.630.15940.00550.02070.00030.05690.0020150.14.8132.11.8487.179.6
    TW4-07-18.18199.41316.380.630.15090.00460.02080.00020.05280.0015142.74.01331.4320.466.7
    TW4-053.54110.76145.870.760.14110.00440.01980.00020.05240.00161343.9126.21.4305.670.4
    TW4-023.82125.50158.370.790.13010.00370.01900.00020.05070.0015124.23.3121.51.4233.473.1
    TW4-084.24136.70179.380.760.12620.00380.01910.00020.04830.0014120.73.4122.11.3122.373.1
    TW4-063.73116.73156.960.740.12860.00370.01920.00020.04970.0015122.83.4122.41.318970.4
    TW4-0310.78457.45413.131.110.12810.00250.01920.00010.04870.0010122.42.3122.40.9131.646.3
    TW4-08-18.35211.54348.210.610.13180.00410.01920.00020.04990.0015125.73.7122.41.3187.170.4
    TW4-147.42304.99297.871.020.13490.00620.01920.00030.05120.0023128.55.6122.52.0250.1101.8
    TW4-04-115.37476.94598.790.800.12730.00300.01940.00020.04780.0011121.62.7123.91.1100.157.4
    TW4-029.67487.47333.541.460.12900.00570.01970.00020.04780.0021123.25.1125.71.587.1103.7
    TW4-073.2998.98136.250.730.13460.00440.01980.00020.05070.0018128.24.0126.51.5233.481.5
    TW4-01-13.4471.52137.850.520.14000.00510.01980.00030.05360.00211334.5126.61.7366.788.9
    TW4-044.41110.45184.670.600.13790.01000.02020.00040.05100.0041131.28.91292.7239185.2
    TW4-03-16.06142.05239.110.590.14090.00490.02050.00020.05050.0018133.84.3130.71.6220.449.1
    TW4-069.23293.04347.050.840.14630.00780.02080.00030.05170.0028138.76.91331.9272.3127.8
    TW4-0316.41500.73502.201.000.17120.00690.02480.00030.05030.0020160.46.0157.81.8209.388.0
    TW4-02-16.78146.85209.130.700.17410.00500.02490.00030.05200.00161634.4158.31.8283.470.4
    TW4-0816.28791.81392.012.020.17650.00610.02490.00030.05200.00191655.3158.31.9283.483.3
    TW4-1213.66308.29437.330.700.17090.00910.02500.00030.04960.0026160.27.9159.42.2172.3122.2
    TW6,花岗斑岩,19个测点年龄加权平均值为125.8±1.0 Ma,MSWD=2.4
    TW6-09-13.6990.47153.580.590.15260.00620.01920.00030.06000.0026144.25.4122.51.6611.194.4
    TW6-07-14.06137.21155.140.880.14840.00550.01940.00030.05660.0022140.54.91241.647685.2
    TW6-088.25234.92337.240.700.14620.00450.01970.00020.05440.0017138.54.0125.61.4387.168.5
    TW6-05-16.96174.85273.190.640.14410.00420.01990.00020.05320.0016136.73.81271.4344.5100.9
    TW6-06-111.20418.86385.641.090.14300.00380.02070.00020.05080.0013135.73.4131.81.4227.865.7
    TW6-074.00117.11162.720.720.12570.00560.01910.00030.04990.0026120.25.1121.71.7190.8120.4
    TW6-08-16.87192.56277.460.690.13690.00440.01940.00020.05220.0018130.33.9123.61.3294.577.8
    TW6-0110.25394.76373.871.060.12800.00370.02000.00020.04710.0014122.33.3127.41.453.866.7
    TW6-02-112.42403.63472.630.850.13410.00340.01950.00020.05030.0013127.73.1124.61.2209.393.5
    TW6-04-132.851132.261223.710.930.13590.00260.01980.00020.04950.0008129.42.3126.61.3172.338.9
    TW6-034.42133.86176.600.760.13730.00590.02000.00030.05100.0022130.65.3127.72.1242.7102.8
    TW6-01-111.08474.07386.391.230.12940.00340.01960.00020.04840.0013123.53.11251.3116.867.6
    TW6-046.76175.91279.380.630.13630.00460.02000.00030.05010.0017129.74.2127.81.7211.281.5
    TW6-0611.03296.75455.480.650.13630.00380.02000.00020.04980.0014129.83.4127.61.4183.469.4
    TW6-105.33159.45210.360.760.13320.00540.01960.00020.04990.00211274.9125.21.6190.893.5
    TW6-03-118.44554.42693.880.800.13310.00270.01970.00020.04920.0010126.82.5125.81.1166.848.1
    TW6-10-110.45420.23382.961.100.13090.00410.01950.00020.05070.0020124.93.7124.51.5233.495.4
    TW6-028.77253.19359.050.710.13340.00440.01990.00020.04930.0017127.14.0127.11.5161.279.6
    TW6-0916.49581.43623.690.930.13280.00300.01970.00020.04920.0011126.62.7125.61.3166.853.7
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    全岩地球化学分析在北京燕都中实测试技术有限公司完成。主量元素使用日本岛津XRF-1800型波长色散X射线荧光光谱仪测定,分析误差优于5%;微量元素使用布鲁克(Bruker)公司生产的aurora M90 ICP-MS电感耦合等离子质谱仪测定,分析误差优于10%。全岩地球化学数据见表 2

    表  2  吉峰地区花岗质岩石全岩地球化学数据
    Table  2.  Whole rock geochemical data of granitic rocks in Jifeng area
    元素TW4TW5JP6TW06JP6TW08TW6JP11TW02TW426TW362TW3TW302TW383TW082
    二长花
    岗岩
    二长花
    岗岩
    二长花
    岗岩
    二长花
    岗岩
    花岗斑岩花岗斑岩英安质
    凝灰岩
    流纹岩流纹岩流纹岩流纹岩粗面岩
    SiO275.0373.9774.3674.2366.8873.4967.6874.9171.9073.6171.1962.67
    TiO20.200.170.200.200.390.180.770.200.270.250.370.91
    Al2O313.5614.2113.3113.4416.2214.0616.6613.2614.6114.6415.3816.44
    Fe2O30.931.020.920.931.261.212.901.130.801.101.124.17
    MgO0.060.040.050.050.100.040.060.080.030.020.050.10
    MnO0.240.130.240.240.640.130.850.230.190.070.391.18
    CaO0.680.220.820.761.610.390.470.240.530.471.201.84
    Na2O3.124.213.873.923.344.261.763.525.034.813.623.39
    K2O5.154.695.115.166.535.605.694.994.783.624.615.07
    P2O50.030.030.030.040.100.030.200.040.050.040.130.27
    烧失量0.540.910.580.541.440.482.400.940.511.201.373.44
    FeO0.440.220.460.451.300.090.310.361.080.070.410.26
    总计100.0399.85100.00100.0099.9699.9699.7999.9399.9199.9099.8899.77
    K2O/Na2O1.651.111.321.321.961.323.231.420.950.751.271.49
    FeO*/MgO5.258.455.325.283.828.913.446.009.3014.923.603.41
    A.R.3.774.224.494.553.485.292.544.424.683.522.972.72
    A/CNK1.141.150.991.001.051.021.681.141.011.161.171.14
    A/NK1.271.181.121.121.291.081.841.181.091.241.401.49
    Q35.6331.3230.4929.9918.2626.5034.8834.9722.7931.2230.1419.36
    C1.701.920.010.110.990.377.431.750.322.092.592.78
    Or30.6128.0130.3730.6939.2333.2734.5429.8028.4721.6527.6931.09
    Ab26.5536.0232.9333.3428.6936.2015.3130.1142.8841.2331.1129.78
    An3.200.863.853.557.461.751.060.912.312.065.197.65
    Di(FS)0.000.000.000.000.000.000.000.000.000.000.000.00
    Di(MS)0.000.000.000.000.000.000.000.000.000.000.000.00
    Hy(MS)0.610.340.610.611.610.332.170.580.490.181.003.05
    Hy(FS)0.000.000.000.000.900.000.000.000.940.000.000.00
    Mt1.040.311.071.041.860.000.000.861.160.000.420.00
    Il0.380.330.390.380.760.270.820.380.520.200.710.81
    Hm0.220.820.190.210.001.222.980.550.001.110.854.33
    Ap0.070.080.080.080.240.060.470.100.120.100.300.64
    DI92.7995.3593.8094.0186.1895.9684.7394.8794.1494.1088.9480.22
    Rb222.17175.89189.92217.42280.54189.92220.61169.65201.37199.29156.52266.24
    Sr114.62143.9948.7253.01160.0532.93302.50162.47331.65202.84250.80193.82
    Ba374.76818.52117.55127.84895.44126.16555.12793.801004.40265.32545.52959.64
    Nb21.5812.3123.0330.1524.0317.3215.1512.0917.1121.5213.5718.01
    Ta1.911.191.823.961.982.011.281.211.811.981.141.36
    Zr170.59218.33177.91194.18523.10208.69369.65332.98324.31254.52238.68469.60
    Hf7.365.556.878.1014.046.5010.748.919.758.908.3611.90
    V31.0737.2511.2412.9061.5413.6237.3643.7668.9235.8633.5975.84
    Ni1.541.640.320.276.721.072.551.632.242.011.404.69
    Be4.092.494.395.375.743.613.123.103.844.493.573.61
    Co1.410.611.181.216.050.754.541.494.820.832.488.67
    Li51.0621.0012.0414.0431.176.7224.7313.3447.7713.5815.9221.47
    Th22.5317.1516.9325.2123.1913.4919.8616.0320.6525.2815.8118.69
    U3.493.153.565.244.442.344.293.434.534.071.532.97
    Sc5.766.882.222.689.951.108.578.219.916.535.5811.56
    La31.6625.1641.1041.4957.8114.2246.5135.0738.7255.7332.5748.13
    Ce59.1961.5277.1178.63142.5937.8292.5876.1681.2099.7763.24109.73
    Pr5.775.779.029.3715.303.3810.158.809.1610.866.5413.70
    Nd17.9619.7532.6433.2758.3011.7836.2732.7834.3137.1721.7754.12
    Sm2.432.875.305.649.062.255.335.495.645.383.048.81
    Eu0.310.470.340.371.480.251.010.661.020.600.631.66
    Gd2.722.964.674.938.072.045.174.995.415.082.977.36
    Tb0.390.500.720.791.190.360.790.850.840.750.441.09
    Dy2.222.733.914.506.022.283.984.714.774.082.185.58
    Ho0.450.560.770.871.130.470.790.950.960.820.431.02
    Er1.401.642.422.803.031.572.222.662.642.371.202.64
    Tm0.290.330.440.500.520.300.420.520.500.430.230.45
    Yb2.082.292.983.443.382.122.813.433.353.041.602.90
    Lu0.390.530.510.600.730.530.610.660.590.550.320.67
    Y14.2416.3222.4325.9031.2212.8922.2526.5927.7923.8912.4329.05
    Ga17.8417.4618.2324.5415.9520.0016.0621.98
    Pb35.9421.8320.8536.7023.5324.7915.2021.98
    TZr/℃803825792801890807908868845840833885
    注:FeO*=0.8998×TFe2O3; A/NK=摩尔Al2O3/(Na2O+K2O); A/CNK=摩尔Al2O3/(CaO+Na2O+K2O); A.R.=wt%(Al2O3+CaO+(Na2O+K2O))/(Al2O3+CaO-(Na2O+K2O));DI=Q+Or+Ab+Ne+Lc+Kp; TZr=12900/(2.95+0.85M+ln(49600/Zr), 其中M=摩尔(K+Na+2Ca)/(Si×Al);主量元素含量单位为%, 微量和稀土元素含量单位为10-6
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    LA-ICP-MS锆石U-Pb同位素定年选取典型花岗岩样品2件(TW4和TW6)、满克头鄂博组流纹岩样品1件(TW3)、玛尼吐组英安质熔结凝灰岩样品1件(TW462)。锆石阴极发光(CL)与测点视年龄图、U-Pb谐和年龄与年龄加权平均值图见图 4。所挑选的锆石颗粒粒径80~130 μm,晶形较好,以长柱状为主,长宽比为1:1~3:1,晶体具有明显的生长环带和韵律结构,Th/U值多大于0.7,具有典型的岩浆成因锆石特征,所测年龄能够代表岩浆的侵位时间[35]。由图 4可知,4个样品的测试结果较理想,大部分测点位于U-Pb谐和线附近,少量测点206Pb/238U年龄偏大,可能为残留锆石,在加权平均计算时予以剔除。其中花岗岩样品TW4的206Pb/238U年龄加权平均值为125.5±1.8 Ma(MSWD=6.7);样品TW6的206Pb/238U年龄加权平均值为125.8±1.0 Ma(MSWD=2.4);满克头鄂博组流纹岩样品TW3的206Pb/238U年龄加权平均值为125.4±0.8 Ma(MSWD=0.36);玛尼吐组凝灰岩样品TW426的206Pb/238U年龄加权平均值为145.2±1.1 Ma(MSWD=1.4)。

    图  4  吉峰地区岩浆岩锆石U-Pb谐和图、阴极发光(CL)图像及年龄值(Ma)
    Figure  4.  LA-ICP-MS zircon U-Pb concordia diagrams, CL images and ages of Jifeng igneous rocks

    (1) 主量元素

    在使用主量元素地球化学图解前,均去除烧失量,重新换算成100%。在TAS图解上,玛尼吐组凝灰岩(TW426)落入流纹岩与英安岩边界;早白垩世花岗岩和满克头鄂博组火山岩样品点分布于流纹岩与粗面岩区域(图 5-a)。

    图  5  吉峰地区花岗质岩石判别图
    a—TAS图解;b—A/CNK-A/NK图解;c—SiO2-K2O图解;d—A.R.-SiO2图解
    Figure  5.  Discrimination diagrams of Jifeng granites and tuffs

    表 2可知,早白垩世花岗岩和满克头鄂博组火山岩地球化学特征较一致:①大多数样品SiO2含量(66.88%~75.03%)与分异指数(87.4~97.2)较高(除粗面岩TW082外);②岩石Al2O3含量高(13.26%~16.44%),铝饱和指数(A/CNK)介于0.99~1.17之间,在A/CNK-A/NK图解上大体投影于过铝质岩区域(图 5-b),在CIPW标准矿物中则可见刚玉分子的出现;③全碱含量高,K2O+Na2O值为8.23%~9.87%,K2O/Na2O值多大于1.1,在SiO2-K2O图解上,样品点主要落入橄榄粗玄系列和高钾钙碱性系列(图 5-c),而在A.R.-SiO2图解上,大体落入碱性岩区域(图 5-d);④在Harker图解中,TiO2、Al2O3、TFe2O3、CaO、P2O5含量随SiO2含量增高而降低(图 6)。

    图  6  吉峰花岗质火山-侵入杂岩哈克图解
    Figure  6.  Harker diagrams of Jifeng granitic volcanic-intrusive complex

    而玛尼吐组火山岩样品TW426地球化学特征则稍有不同,具有较低的SiO2含量(67.68%),高的Al2O3含量(16.66%)和铝饱和指数(1.68),在A/CNK-A/NK图解上位于强烈过铝质区域,低全碱含量(7.65%)和Wright碱度率(2.54)及高K2O/Na2O值(3.23)等特征。

    (2) 微量元素

    表 2可知,早白垩世花岗岩、满克头鄂博组流纹岩及玛尼吐组凝灰岩微量元素地球化学特征较一致。在球粒陨石标准化稀土元素配分模式图(图 7-a)中,所有样品均表现出右倾的海鸥式配分模式,具有相对富集的LREE、较高的(La/Yb)N值(4.82~14.60)及轻微-中等的负Eu异常。在微量元素原始地幔标准化蛛网图(图 7-b)中,大离子亲石元素(LILE)Rb、U、Th、K及Pb富集,Ba和高场强元素(HSFE)Ti、Nb、Ta、Sr、P等则明显亏损。

    图  7  吉峰花岗岩-火山岩球粒陨石标准化稀土元素配分模式图(a)和原始地幔标准化微量元素蛛网图(b)(标准化值据参考文献[36])
    Figure  7.  Chondrite-normalized REE patterns(a)and primitive-mantle-normalized trace element spidergrams(b)for the Jifeng granites and tuffs

    前文已述,大兴安岭北段吉峰地区秀山花岗岩、旭光花岗岩、满克头鄂博组流纹岩和玛尼吐组凝灰岩的锆石U-Pb年龄分别为125.5±1.8 Ma,125.8±1.0 Ma,125.4±0.78 Ma,145.2±1.1 Ma,指示该区至少经历了约145 Ma和约125 Ma两期岩浆活动。

    本文采集的岩石样品的A/CNK=0.99~1.68(平均1.14),CIPW标准矿物计算中出现刚玉分子(0.01%~7.43%),表现出准铝质-过铝质岩石的特征,暗示其与S型花岗岩的亲缘性。但其P2O5含量低(0.03%~0.28%),P2O5与SiO2表现出明显的负相关趋势(图 6),且岩石未见堇青石、石榴子石等矿物,因而基本排除其为S型花岗岩的可能[37-40]

    同时,岩石具有高硅、高铝、高分异指数、轻重稀土元素中等分异、LILE富集、HSFE强烈亏损、部分主量、微量元素与SiO2呈负相关等高分异特征,与I型花岗岩有较好的相似性。Chappell等[41]指出,在高分异的情况下,A型花岗岩原本高的Zr、Nb、Ce、Y含量会明显降低[42],导致其与I型花岗岩之间成因类型判别困难。在花岗岩成因判别图解中,大部分样品具有Ga/Al×10000>2.6、(Zr+Nb+Ce+Y)>350×10-6、Zr>250×10-6等特征,投影于A型花岗岩区域[43](图 8)。加之吉峰地区岩浆岩锆石饱和温度为792~908 ℃,平均841 ℃,高于I型和S型花岗岩形成温度(表 2)。因此,在无较富镁铁质岩石伴生的情况下,笔者倾向于利用Whalen等[43]的指标,将吉峰地区上述2期花岗质岩石归为A型花岗岩。

    图  8  吉峰花岗岩成因类型判别图解(底图据参考文献[43])
    a—K2O-Na2O图解;b—10000Ga/Al-K2O+Na2O图解;c—10000Ga/Al-Nb图解;d—10000Ga/Al-Zr图解;e—(Zr+Nb+Ce+Y)-FeO*/MgO图解;f—(Zr+Nb+Ce+Y)-(K2O+Na2O)图解。FG—分异的长英质花岗岩; OGT—未分异的M、I、S花岗岩
    Figure  8.  Classification diagrams indicating Jifeng granites belonging to A-types granite

    前文已述,大兴安岭北段吉峰地区2期岩浆岩均为A型花岗岩。通常认为,A型花岗岩形成于较高温度、来源于较浅部的中上地壳(成岩压力较低),与大陆裂谷、大洋热点区、后造山等拉张构造背景息息相关[37, 43-47]。在构造背景判别图上,吉峰地区大部分样品点落入后碰撞区域(图 9),指示大兴安岭北段在晚侏罗世(145.2 Ma)和早白垩世(125.4~125.8 Ma)均处于伸展的大地构造背景。

    图  9  吉峰地区花岗质岩石大地构造背景判别图(底图据参考文献[48])
    Figure  9.  Tectonic background discriminant diagram of granitic rocks in Jifeng area

    为更全面地理解大兴安岭北段吉峰地区晚中生代的构造背景和成岩动力学机制,本文系统分析了大兴安岭及其邻区已发表的170~100 Ma的年龄和地球化学数据。由图 10可知,大兴安岭岩浆活动自170 Ma开始逐渐增强,在约132 Ma达到高峰,之后逐渐减弱,在约120 Ma后岩浆活动近于停歇。但若依据岩石成因类型进行分类统计,可见岩浆活动随时间有规律地进行:①晚侏罗世(170~145 Ma),在大兴安岭全区广泛发育,其中158 Ma和150 Ma存在2个小的活动峰期,岩石介于碱性-亚碱性之间,以钙碱性为主[3, 49-55];②早白垩世早期(145~135 Ma),岩石以高钾钙碱性I型(部分为埃达克质岩)和A型花岗质岩浆岩共同发育为典型特征(图 10)[25, 56-69],相对晚侏罗世,该期岩浆活动进一步活跃,岩石极性显著增大;③早白垩世中期(135~120 Ma),岩浆活动强烈发育,在约132 Ma达到峰值,岩石主要为A型花岗质岩石和后碰撞花岗岩[2, 25, 52, 58, 67, 70-76],岩石极性进一步增大;④早白垩世晚期(120~100 Ma),大兴安岭地区岩浆活动迅速减弱,而松辽盆地开始发育大量A型花岗岩和双峰式火山岩(图 10)[77-85];吉黑东部则以钙碱性组合为主兼有碱性岩特征,并具有自陆缘向陆内极性成分增加的趋势[3]

    图  10  大兴安岭及其邻区晚中生代年龄直方图
    (图a数据据本文及参考文献[4, 49-162],图b数据据参考文献[52])
    Figure  10.  Histogram of the Late Mesozoic ages in the Da Hinggan Mountains and their adjacent areas

    基于前文大兴安岭及其邻区岩浆岩年龄框架,笔者认为,大兴安岭及其邻区构造演化可能并非受单一构造体系域的控制。

    (1) 中晚侏罗世(170~145 Ma)

    大兴安岭、东蒙古和外贝加尔地区在该期岩浆活动强烈[7, 26, 52-53, 89, 163-164],而松辽盆地及其东部地区岩浆作用却十分少见。古太平洋板块很难俯冲如此远的距离(大于2000 km)触发大兴安岭以西地区大规模岩浆活动,而对松辽盆地及其东部地区无显著影响。因而大兴安岭地区中晚侏罗世钙碱性岩石组合可能更多地受蒙古-鄂霍茨克洋闭合制约[3]。但同时需明白,古太平洋板块西向俯冲及南部特提斯洋向北俯冲的远程效应,驱动华北北缘增生带向北与西伯利亚板块俯冲碰撞,并导致大兴安岭岩石圈挤压和增厚[165]

    (2) 早白垩世早期(145~135 Ma)

    高Sr、低Y的埃达克质岩石的发育,指示大兴安岭地区在该期仍以蒙古-鄂霍茨克构造体系域为主,发生了加厚地壳的部分熔融,而A型花岗岩则可能为加厚条件下岩浆底侵下地壳部分熔融的产物,也表明该时期大兴安岭地区即将发生由挤压加厚向伸展的转换。

    (3) 早白垩世中期(135~120 Ma)

    尽管该期仍可见埃达克质岩的发育,但A型花岗质火山-侵入岩和后碰撞花岗岩比例逐渐增大,岩石极性亦逐步增大,指示大兴安岭地区处于强烈的拉张环境,可能为蒙古-鄂霍茨克后造山阶段或拆沉阶段。但值得注意的是,该时期黑龙江、饶河等地可见构造核杂岩[2],指示中国东北地区伸展作用的广泛分布。因此,也不能排除古太平洋板块后撤导致的加厚地壳拆沉的可能。

    (4) 早白垩世晚期(120~100 Ma)

    本阶段大兴安岭地区岩浆活动迅速减弱,指示蒙古-鄂霍茨克构造体系域控制作用的结束。而松辽盆地大规模的A型花岗岩和双峰式火山岩,指示东北地区拉伸作用的快速东移;吉黑东部岩浆岩呈现出由东向西极性增大的趋势[3],则可能受东部俯冲板片的局部挤压的控制。这表明东北地区在该期主要受古太平洋构造体系域的控制。

    (1) 大兴安岭北段吉峰地区发育约145.2 Ma和约125.4 Ma两期岩浆活动,2期岩浆岩均具有A型花岗岩的地球化学特征。其中第一期A型花岗岩可能为以挤压加厚为主、向伸展转换的构造背景下地壳部分熔融的产物;而第二期A型花岗岩可能为强烈拉伸环境下大兴安岭加厚地壳大规模拆沉的产物。

    (2) 大兴安岭晚中生代大规模岩浆活动受蒙古-鄂霍茨克和古太平洋构造体系域的共同控制,其中早白垩世中期以前主要受蒙古-鄂霍茨克构造体系域控制,早白垩世晚期则以古太平洋构造体系域为主。

    致谢: 野外工作中得到青海省地质矿产勘察院的帮助,锆石U-Pb 定年得到中国地质大学(北京)的帮助,审稿老师提出了宝贵的修改意见,在此一并表示诚挚的感谢。
  • 图  1   区域大地构造位置

    Figure  1.   The regional tectonic map

    图  2   牦牛山组火山岩TAS 图解

    Figure  2.   TAS diagram of the volcanic rocks in Maoniushan Formation

    图  3   牦牛山组火山岩SiO2-K2O 图

    Figure  3.   SiO2-K2O diagram of the volcanic rocks in Maoniushan Formation

    图  4   牦牛山组安山岩(a)和酸性火山岩稀土元素配分图(b)

    Figure  4.   Chondrite-normalized REE patterns of the andesite rocks (a) and the acid volcanic rocks (b) in Maoniushan Formation

    图  5   牦牛山组安山岩ORG 标准化蛛网图(a)和酸性火山岩ORG 标准化蛛网图(b)

    Figure  5.   Trace element spider diagram of the andesite rocks (a) and the acid volcanic rocks (b) in Maoniushan Formation

    图  6   火山岩代表性锆石阴极发光(CL)图像

    Figure  6.   CL image of zircons of the volcanic rocks

    图  7   牦牛山组火山岩LA-ICP-MS 锆石U-Pb谐和图(a、c)及206Pb/238U 年龄图(b、d)

    Figure  7.   Zircon LA-ICP-MS U-Pb age of the volcanic rocks (a,c) and 206Pb/238U data (b,d) in Maoniushan Formation

    图  8   安山岩Th-La/Yb 图解

    Figure  8.   Th-La/Yb diagram of the andesite rocks

    图  9   酸性火山岩Y-Nb 图解

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

    Figure  9.   Y-Nb diagram of the volcanic rocks

    图  10   酸性火山岩SiO2-Al2O3图解

    IAG+CAG+CCG—岛弧花岗岩类+大陆弧花岗岩类+大陆碰撞带花岗岩类;POG—造山期后花岗岩类;PRG+CEUG—与裂谷有关的花岗岩类+大陆造陆抬升花岗岩类

    Figure  10.   Mass fraction of SiO2-Al2O3 diagram from the volcanic rocks

    表  1   牦牛山组火山岩主量元素分析数据

    Table  1   Major element compositions of the volcanic rocks in Maoniushan Formation

    %
    样品编号岩性SiO2Al2O3Fe2O3FeOMgOCaONa2OK2OTiO2MnOP2O5烧失量总量ALKδA / CNK
    P3-16 REE1粗面英安岩64.6913.792.560.500.462.960.149.180.110.0430.0334.7199.179.783.841.12
    P3-21 REE1流纹岩72.7711.550.740.350.142.151.088.390.100.0210.0192.4699.779.712.980.99
    P5-3 REE1流纹岩71.6712.031.520.470.801.541.876.060.270.0250.0533.3999.708.202.161.27
    P10-3 REE1英安质晶屑凝灰岩62.9914.103.921.700.853.083.914.500.530.0460.203.9299.768.763.401.23
    P10-5 REE1安山玻质岩61.8818.570.892.702.770.479.250.120.800.0140.271.8799.609.544.541.89
    P12-11 REE1粗面安山岩53.9416.834.752.544.124.186.171.181.050.0860.164.3199.317.694.421.46
    P12-12 REE1杏仁状流纹岩71.9914.081.250.260.190.702.975.960.370.0140.0821.8399.709.102.731.46
    YP07(3) REE1碳酸盐化流纹岩70.1312.620.190.530.912.113.855.700.220.0440.0553.1299.499.863.311.08
    D3450 REE1流纹岩73.0813.412.010.730.290.794.093.520.180.0190.0331.7499.897.741.911.60
    P16-60 REE1流纹岩69.6513.500.431.880.752.033.445.010.350.0410.0882.5599.738.672.641.29
    P19-6 REE1流纹岩76.6110.750.470.640.251.553.313.680.120.0320.0261.9299.367.121.451.26
    P19-30 REE1流纹岩67.6012.080.880.970.834.481.815.360.400.0480.0665.0399.567.552.021.04
    P19-32 REE1安山岩55.6616.772.544.873.966.543.321.931.120.130.2512.3099.395.382.071.42
    D3560GS1流纹岩75.4812.540.740.200.41.183.4513.7460.07210.01770.07211.7899.687.331.591.50
    D-D7015GS1凝灰岩70.8115.581.240.430.371.263.504.420.120.0160.0632.1099.908.082.231.70
    D4012GS1安山岩59.1516.731.225.312.193.554.491.871.100.0970.333.3599.386.582.381.69
    P35-35GS1流纹岩72.5614.210.810.150.600.683.424.150.0690.0210.0333.35100.057.831.911.72
    下载: 导出CSV

    表  2   牦牛山组火山岩稀土元素分析数据

    Table  2   Rare earth element compositions of the volcanic rocks in Maoniushan Formation

    10-6
    样品
    编号
    岩性LaCePrNdSmEuGdTbDyHoErTmYbLuYΣREELREEHREELREE/
    HREE
    LaN/YbNδEu
    P3-16
    REE1
    粗面英
    安岩
    70.61157.9514.3957.9510.820.879.601.235.591.053.150.453.130.4725.56337.26312.6024.6612.6816.210.26
    P3-21
    REE1
    流纹岩34.6092.738.4034.676.940.647.281.267.341.524.540.674.390.6335.98205.61177.9727.646.445.650.27
    P5-3
    REE1
    流纹岩27.9873.956.8028.885.811.346.070.975.501.093.200.442.710.4024.41165.12144.7420.377.117.410.69
    P10-3
    REE1
    英安质晶
    屑凝灰岩
    27.9673.876.8529.986.211.596.401.055.961.243.870.553.560.5534.06169.64146.4623.186.325.630.76
    P10-5
    REE1
    安山玻
    质岩
    18.3643.374.6420.234.271.344.780.834.910.992.720.382.310.3430.29109.4792.2217.255.345.710.90
    P12-11
    REE1
    粗面安
    山岩
    13.3933.753.7917.483.971.584.320.734.430.922.820.402.600.4022.8490.5873.9616.634.453.701.16
    P12-12
    REE1
    杏仁状
    流纹岩
    20.0369.735.2922.824.931.065.030.834.730.962.810.422.700.4229.06141.76123.8617.906.925.320.64
    YP07(3)
    REE1
    碳酸盐化
    流纹岩
    82.39180.1715.4561.6610.051.449.101.054.410.802.460.342.280.3521.62371.95351.1720.7816.9025.940.45
    D3450
    REE1
    流纹岩19.0244.414.7319.613.881.123.800.593.270.641.980.292.020.3315.95105.6992.7712.927.186.750.88
    P16-60
    REE1
    流纹岩22.0458.655.0920.573.971.043.960.613.370.672.130.301.980.3018.38124.67111.3613.318.368.000.79
    P19-6
    REE1
    流纹岩21.5163.315.8825.685.880.596.321.086.651.404.160.624.080.6134.50147.77122.8624.914.933.780.30
    P19-30
    REE1
    流纹岩29.3080.407.2029.615.541.465.380.794.210.842.550.352.340.3725.35170.33153.5116.829.139.000.81
    P19-32
    REE1
    安山岩24.4166.326.2327.905.391.625.390.784.160.832.280.302.010.2920.26147.90131.8716.038.238.730.91
    D3560
    GS1
    流纹岩17.6226.123.6813.152.480.391.820.240.950.160.480.070.480.086.3567.7263.464.2614.8826.500.54
    D-D7015
    GS1
    凝灰岩27.1269.795.1818.513.260.722.630.461.340.380.780.240.750.258.30131.42124.596.8318.2525.790.73
    D4012
    GS1
    安山岩31.7470.587.9534.507.001.626.351.135.261.263.040.562.600.5232.00174.10153.3820.717.418.760.73
    P35-35
    GS1
    流纹岩23.9245.185.5120.544.010.652.970.391.490.300.710.130.810.128.75106.7299.806.9114.4421.120.55
    下载: 导出CSV

    表  3   牦牛山组火山岩微量元素分析数据

    Table  3   Trace element compositions of the volcanic rocks in Maoniushan Formation

    10-6
    样品编号岩性AsBaBiCoCuGaHfMoNbNiPbRbSbSrTaThTiUVZnZr
    P3-16 REE1粗面英安岩299845.67.717.682462412.745.293.02514.354.53623.35250.15.4838.031.37924.866726.58711.3732.32178.6
    P3-21 REE1流纹岩448446.77.0210.98387.6513.235.560.8213.644.177.61210.755.7431.291.2419.286093.643.309.36170.2
    P5-3 REE1流纹岩33.0715.82.998.19131.612.376.160.3258.3132.8285.486151.93.2040.860.88415.5716443.22910.987.494204.2
    P10-3 REE1英安质晶屑凝灰岩20.3476.644.18.37774.3517.858.060.86811.353.33218.6130.123.364.610.87813.7531923.04515.8527.65262.2
    P10-5 REE1安山玻质岩2.2939.673.319.54521.6118.325.050.15711.363.676.63430.921.8024.80.9287.81548141.46530.4112.94163
    P12-11 REE1粗面安山岩6.45333.92.4622.7517.8417.664.20.4097.956446.39762.11.51252.70.6185.61562721.437118.666.46152.2
    P12-12 REE1杏仁状流纹岩3.14499.13.176.22318.7218.416.610.5217.4513.29133.67158.12.8139.340.72715.4922033.891866.1211.6
    YP07(3) REE1碳酸盐化流纹岩27.8478.10.287.051.84214.737.521.4068.6252.093178.1100.19.0140.290.47214.5413473.2566.845329.4250.8
    D3450 REE1流纹岩1.13646.50.167.563.8115.489.010.3210.381.3340.78128.650.6992.430.7412.2210741.782.34119.70312.8
    P16-60 REE1流纹岩3.15640.90.278.5371.90314.264.560.5525.73112.314.42159.10.9365.680.65412.6421213.17733.2541.25150.1
    P19-6 REE1流纹岩3.97424.10.327.1834.97213.774.360.45911.275.7426.38139.90.7564.840.92218.917143.8197.66925.96131.4
    P19-30 REE1流纹岩9.5410580.485.9847.29914.415.052.4449.8167.84629.43207.40.7184.250.74811.8824203.39144.6632.46176.5
    P19-32 REE1安山岩2.60582.10.0720.0418.1218.74.891.15212.1217.1914.5266.380.55355.50.6316.92966881.458138.888.92177.9
    D3560GS1流纹岩58413.42.5112.8516.45.6130.6228.91.3110.82.0015.2389.4
    D-D7015GS1凝灰岩7532.934.1113.11148.85258.91.1612.33.077.1674.77131
    D4012GS1安山岩39816.76.619.733.1763.15246.50.7710.22.3576.274.2253
    P35-35GS1流纹岩51711.23.3410.81.01145.47183.91.089.082.843.1247.77599.5
    下载: 导出CSV

    表  4   牦牛山组火山岩LA-ICP-MS 锆石U-Th-Pb 年龄测定结果

    Table  4   LA-ICP-MS U-Th-Pb ages of zircons from the volcanic rocks in Maoniushan Formation

    测点Pb
    /10-6
    Th
    /10-6
    U
    /10-6
    Th/U207Pb
    /235U
    206Pb
    /238U
    206Pb/238U
    年龄/Ma
    谐和
    度/%
    YP07(3)TW1流纹岩
    01261854240.450.4470.0100.0610.0013808-1.32
    02141052330.460.4450.0110.0590.00137280.54
    03211623870.420.5810.0160.0550.001338914.20
    04151212500.480.4100.0150.0580.00137311-4.38
    05-2345390.450.0110.0550.0010.00134389.33
    06122141981.090.4560.0160.0590.00137192.96
    078631400.440.4820.0140.0600.00137983.09
    08302035020.420.4500.0190.0590.00137192.16
    09211533520.450.4570.0160.0590.00137192.96
    1091011580.660.4470.0210.0600.0013769-0.27
    11161172650.440.4730.0100.0610.00138083.42
    12221683660.470.4420.0110.0600.0013739-0.27
    13202733290.830.4530.0190.0600.00137790.80
    14231703960.430.5000.0130.0580.001363813.22
    159721560.460.4410.0140.0590.00137190.00
    1611811850.440.4770.0140.0600.00137396.17
    17181342980.450.5690.0130.0610.00137597.20
    18191723660.470.5790.0190.0510.001317810.73
    19231743950.440.4300.0160.0590.00137111-2.16
    20131992090.950.4840.0100.0600.00137893.62
    21201453380.430.4900.0100.0590.001368810.05
    22272144560.470.4450.0110.0600.0013759-0.27
    23171332960.450.4440.0130.0580.00137382.47
    YP07(3)TW1流纹岩
    248591400.421.1151.0120.0600.0013759-0.27
    D3450TW1流纹岩
    01121171980.590.4740.0090.0630.00139260.51
    02353205520.580.5140.0100.0640.00139965.51
    03132031991.020.5050.0210.0630.00139275.87
    04121021860.550.5660.0180.0630.001393615.78
    05161372540.540.4710.0120.0630.00139260.00
    06221983540.560.4780.0130.0620.00139061.79
    07262324150.560.4850.0090.0630.00139262.30
    08253463890.890.4730.0080.0630.0013956-0.51
    09222023550.570.6650.0140.0630.001396630.81
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出版历程
  • 收稿日期:  2016-03-08
  • 修回日期:  2016-07-10
  • 网络出版日期:  2023-08-15
  • 刊出日期:  2017-02-28

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