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广西六万山印支早期花岗岩地球化学特征及锆石U-Pb年龄

黄诚, 沈睿文, 南争路, 傅良刚, 刘胜, 蔡砥柱, 王慧, 余杨忠

黄诚, 沈睿文, 南争路, 傅良刚, 刘胜, 蔡砥柱, 王慧, 余杨忠. 2017: 广西六万山印支早期花岗岩地球化学特征及锆石U-Pb年龄. 地质通报, 36(2-3): 209-223.
引用本文: 黄诚, 沈睿文, 南争路, 傅良刚, 刘胜, 蔡砥柱, 王慧, 余杨忠. 2017: 广西六万山印支早期花岗岩地球化学特征及锆石U-Pb年龄. 地质通报, 36(2-3): 209-223.
HUANG Cheng, SHEN Ruiwen, NAN Zhenglu, FU Lianggang, LIU Sheng, CAI Dizhu, WANG Hui, YU Yangzhong. 2017: Zircon U-Pb ages and geochemical characteristics of Early Indosinian Liuwanshan granites, Guangxi. Geological Bulletin of China, 36(2-3): 209-223.
Citation: HUANG Cheng, SHEN Ruiwen, NAN Zhenglu, FU Lianggang, LIU Sheng, CAI Dizhu, WANG Hui, YU Yangzhong. 2017: Zircon U-Pb ages and geochemical characteristics of Early Indosinian Liuwanshan granites, Guangxi. Geological Bulletin of China, 36(2-3): 209-223.

广西六万山印支早期花岗岩地球化学特征及锆石U-Pb年龄

基金项目: 

中国地质调查局项目《广西钦杭成矿带西段博白县、六万山幅1:5万区域地质矿产调查》 12120113072000

详细信息
    作者简介:

    黄诚 (1987-), 男, 硕士, 工程师, 从事成矿作用地球化学研究。E-mail:hc_learn@126.com

  • 中图分类号: P588.12+1

Zircon U-Pb ages and geochemical characteristics of Early Indosinian Liuwanshan granites, Guangxi

  • 摘要:

    广西六万山印支早期花岗岩的岩性主要为堇青黑云二长花岗岩,根据岩石结构特征及侵入接触关系可划分为4个侵入单元。利用LA-ICP-MS U-Pb同位素测定技术,4个侵入单元的锆石206Pb/238U年龄加权平均值分别为252.8±1.9Ma(MSWD=0.92)、249.2±1.9Ma(MSWD=1.2)、248.3±3.2Ma(MSWD=2.1)、246.8±2.8Ma(MSWD=2.2)。地球化学分析结果表明,花岗岩在岩石化学上富集大离子亲石元素Rb、K等,相对亏损高场强元素Ta、Nb、Ti等,反映出与俯冲带有关的岛弧岩浆岩相似的地球化学特征。稀土元素球粒陨石标准化配分曲线呈右倾型,具明显的Eu负异常,相对富集重稀土元素,与典型壳源花岗岩配分曲线一致。部分熔融与分离结晶模型(La/Sm-La)显示,花岗岩主要由部分熔融作用形成,演化过程经历了一定程度的分离结晶作用。结合花岗岩岩石化学特征、微量元素地球化学特征及花岗岩构造环境判别图解,认为六万山印支早期花岗岩的形成经历了早期洋-陆俯冲阶段到晚期陆-陆碰撞阶段的构造演化过程。

    Abstract:

    The Liuwanshan granites consist mainly of cordierite-bearing biotite monzogranite, which can be divided into four emplacement units according to rock structure and the emplacement relationship. LA-ICP-MS zircon U-Pb dating shows that the 206Pb/238U weighted average ages of zircons from these emplaced units are 252.8±1.9Ma (MSWD=0.92), 249.2±1.9Ma (MSWD=1.2), 248.3 ± 3.2Ma (MSWD=2.1), and 246.8 ± 2.8Ma (MSWD=2.2), respectively. Geochemical data reveal that these granites are characterized by enrichment of large ion lithophile elements (LILE, such as Rb and K) and relative depletion of high field strength elements (HFSE, such as Nb, Ta and Ti), suggesting geochemical characteristics of typical subduction-related arc magmatic rocks. REE distribution patterns show right-inclined shape with obvious Eu negative anomaly and relative enrichment of HREE, which is consistent with crust-source granites distribution patterns. La-La/Sm diagram indicates that the Liuwanshan granites were mainly formed by partial melting and experienced a certain degree of fractional crystallization. Combined with petrochemical characteristics, trace elements geochemeical characteristics and tectonic setting discrimination diagrams, the authors have reached the conclusion that Liuwanshan granites were formed in a tectonic setting of early ocean-continent subduction and later continental collision.

  • 广西大容山-十万大山花岗岩带位于广西壮族自治区东南部,是桂东南印支期—海西期花岗岩的重要组成部分。该花岗岩带在大地构造上位于扬子板块与华夏板块的拼贴结合部位,以富含堇青石及局部 (钦州地区) 含石榴子石和紫苏辉石为特征[1-2](图 1)。研究区所处大地构造位置特殊且复杂,被认为是研究扬子板块和华夏板块拼合造山及其相互关系的关键部位[5]。《广西区域地质志》根据槽台说的观点将钦州残余地台划分出六万大山隆起和十万大山坳陷[6]。罗修泉[3]按单元和超单元的花岗岩研究方法,将大容山-十万大山划分为石南、葵山、六万山和旺冲4个超单元,其中六万山超单元即为大容山-六万大山岩体。此后又有学者采用将大容山-十万大山岩体划分为大容山岩体 (北体和南体-浦北岩体)、旧州岩体和台马岩体的方案[4, 7]。六万山复式岩体的概念由覃小锋等提出,总体上属于大容山-十万大山岩体的一部分,为大容山岩体南体即浦北岩体。前人对大容山-十万大山岩体,进行了详细研究,包括岩体年龄、成因、包体特征、岩石地球化学等[3-4, 7-10],但是对六万山印支早期花岗岩体的研究,尤其是年代学及岩石地球化学研究较少。本次在1:5万区域地质填图基础上,在岩体中系统地采集样品,对六万山印支早期各侵位单元进行精确定年,并结合岩石地球化学特征讨论岩体成因及其大地构造环境。

    ①覃小锋, 周府生, 胡贵昂, 等.广西1:25万玉林市幅区调修测报告.广西壮族自治区地质调查研究院, 2004.

    图  1  大容山-十万大山花岗岩带地质简图(据参考文献[3-4]修改)
    Figure  1.  Geological sketch map of the Darongshan-Shiwandashan granites belt

    研究区位于钦杭成矿带西段,处于潘桂棠等[11]划分的云开岛弧与六万大山-大容山岩浆弧的交界部位。区内出露古生代、中生代及新生代地层,缺失石炭纪、二叠纪、三叠纪及侏罗纪地层。古生代地层主要为海相沉积,其中早古生代地层为以厚层砂岩夹泥岩、薄-中层状砂、泥岩互层及薄层泥岩夹粉砂岩为主的浅海陆棚相类复理石沉积建造;晚古生代地层为不连续的滨浅海-半深海相的砂泥岩及碳酸盐岩沉积建造;中生代地层在博白盆地及顿谷断层南东侧的断陷盆地或洼地中有白垩纪山麓洪积相、河流相砂砾岩及火山-火山碎屑岩类陆相沉积物;新生代地层为古近纪、新近纪类磨拉石建造的陆相沉积物及第四纪沉积物 (图 1)。

    区内岩浆岩发育,主要为海西期堇青黑云花岗闪长岩及印支期堇青黑云二长花岗岩,此外,还发育燕山晚期含紫苏石英二长斑岩。

    主要的断裂构造为北东—北东东向顿谷断裂,晚期有印支期—燕山期形成的北西向及南北向断裂。顿谷断裂为区域上规模较大的断裂,是岑溪-博白断裂带的一部分,先后经历了海西期—印支期挤压逆冲、燕山早期伸展断陷、晚期挤压逆冲等转变,控制了研究区岩浆岩和博白盆地的展布。

    六万山印支早期花岗岩是六万山复式岩体的一部分,位于六万大山-大容山隆起区,呈北东向条带状分布,主要为印支早期侵入岩,其岩性为堇青黑云二长花岗岩,以普遍含堇青石且同时含有石榴子石及少量红柱石为特征。据岩石结构特征、矿物成分、含量变化及其侵入接触关系,可分为中细粒斑状堇青黑云二长花岗岩 (ηγcT11)(图版Ⅰ-A)、中粒 (斑状) 堇青黑云二长花岗岩 (ηγcT12)(图版Ⅰ-B)、中粗粒 (斑状) 堇青黑云二长花岗岩 (ηγcT13)(图版Ⅰ-C)、细粒堇青黑云二长花岗岩 (ηγc1T6)(图版Ⅰ-D)。其中ηγcT11ηγcT12ηγcT13之间呈涌动侵入接触关系,而ηγcT16呈脉动侵入于前三者。

      图版Ⅰ  A.中细粒斑状堇青黑云二长花岗岩(ηγcT11);B.中粒(斑状)堇青黑云二长花岗岩(ηγcT21);C.中粗粒(斑状)堇青黑云二长花岗岩(ηγcT31);D.细粒堇青黑云二长花岗岩(ηγcT61);E. ηγcT11镜下特征(正交偏光);F. ηγcT31镜下特征(正交偏光)。Q—石英;Kfs—钾长石;Pl—斜长石;Bt—黑云母;Crd—董青石

    (1) 中细粒斑状堇青黑云二长花岗岩 (ηγcT11)

    主要分布于六万山的睦威、横岭圩、福旺圩、江宁圩等地。岩石呈灰色-灰白色,具似斑状结构,基质具中细粒花岗结构,块状构造,偶夹石英包体。主要矿物成分为石英 (25%~35%)、斜长石 (20%~35%)、钾长石 (20%~35%)、黑云母 (5%~8%)、堇青石 (2%~5%)、石榴子石 (1%~2%) 等 (图版Ⅰ-E)。矿物颗粒根据粒径大小可分为两部分:斑晶,粒径一般为8~12mm,多为长石,含量在3%~10%之间;基质粒径一般在0.2~3mm之间,细粒居多 (大于75%)。岩石中可见明显的长石大斑晶。

    (2) 中粒 (斑状) 堇青黑云二长花岗岩 (ηγcT21)

    主要分布于六万山的江口、凤凰顶、车岗大岭等地。岩石呈灰色-灰白色,具似斑状结构或细中粒-中粒花岗结构,块状构造。主要矿物成分为石英 (25%~35%)、斜长石 (25%~35%)、钾长石 (25%~35%)、黑云母 (5%~8%)、堇青石 (2%~5%)、石榴子石 (1%~2%)、红柱石等。矿物颗粒根据粒径大小可分为两部分:斑晶,粒径一般在12~40mm之间,最大可达70mm,成分为长石,含量在5%~12%之间;基质,粒径一般在0.2~6mm之间,中粒居多 (含量大于75%)。

    (3) 中粗粒 (斑状) 堇青黑云二长花岗岩 (ηγcT31)

    主要分布于六万山的大冲、古龙、柯水勇岭、高屋岭等地。岩石呈灰色-灰白色,具似斑状结构或中粗粒花岗结构,块状构造。主要矿物成分为石英 (27%~35%)、斜长石 (23%~33%)、钾长石 (25%~35%)、黑云母 (5%~8%)、堇青石 (2%~4%)、石榴子石 (1%~2%)、少量红柱石等。矿物颗粒一般在2~12mm之间,以粗粒为主 (一般大于80%)(图版Ⅰ-F)。

    (4) 细粒堇青黑云二长花岗岩 (ηγcT61)

    主要分布于六万山的双凤、石井岭、月亮头等地。岩石新鲜面呈灰色-灰白色,具细粒花岗结构,块状构造。主要矿物成分为石英 (25%~40%)、斜长石 (20%~30%)、钾长石 (25%~35%)、黑云母 (3%~8%)、堇青石 (1%~3%) 等。矿物颗粒粒径一般在2mm以下。

    六万山印支早期花岗岩中包体形态各异,主要有长条状、浑圆状、棱角状等,排列无规律性。包体大小不一,粒径3~20cm不等,在主岩中分布不均匀,一般占主岩的2%~5%,局部可达10%。包体岩石种类主要为变粒岩、长石石英岩、角岩、片岩、脉石英或石英团块。此外,还有部分片麻岩、麻粒岩等。

    在广西博白地区开展1:5万区域地质矿产调查的过程中进行了详细的路线地质调查和剖面测制。本文样品主要采自路线地质调查及岩浆岩03号剖面 (PM03)。根据不同岩体分布位置系统采集了印支早期花岗岩岩石样品。LA-ICP-MS锆石U-Pb测年样品分别采自ηγcT11ηγcT21ηγcT31ηγcT61四个侵位单元 (图 1):样品D4054-Rz1(中细粒斑状堇青黑云二长花岗岩),地理坐标北纬为22°26′04″、东经109°47′11″;样品D2706-Rz1(中粒 (斑状) 堇青黑云二长花岗岩),地理坐标为北纬22°18′34″、东经109°52′05″;样品PM03-37-Rz1(中粗粒 (斑状) 堇青黑云二长花岗岩),地理坐标为北纬22°17′16″、东经109°52′30″;样品D1218-Rz2(细粒堇青黑云二长花岗岩),地理坐标为北纬22°12′03″、东经109°46′21″。此外,还在六垠、双凤、水鸣等地采集了蚀变较弱的新鲜岩石样品进行岩石地球化学测试。

    岩石地球化学分析在河北省区域地质矿产调查研究所实验室完成。对采集的样品去除风化表皮,碎样,研磨成200目以下的岩石粉末。采用粉末样品压片制样,主量元素用X射线荧光光谱仪 (XRF) 直接测量;稀土和微量元素采用电感耦合等离子体质谱仪 (ICP-MS) 和等离子体发射光谱仪 (ICP-AES) 分析。测试结果见表 1

    表  1  六万山印支早期花岗岩主量、微量和稀土元素组成及其相关参数
    Table  1.  Major, trace elements and REE composition and related parameters of Early Indosinian Liuwanshan granites
    侵位单元
    样品编号
    ηγcT11ηγcT21ηγcT31ηγcT61
    D4054-
    Rz1
    D4059-
    Rz1
    D5170-
    Rz1
    D5174-
    Rz1
    D2706-
    Rz1
    D1210-
    Rz1
    D2682-
    Rz1
    D1054-
    TW1
    PM03-37-
    Rz1
    PM03-
    43-GSY
    PM03-
    9-XT1
    D2524-
    Rz1
    PM03-
    41-Rz1
    D5361-
    Rz2
    D1218-
    Rz2
    D5475-
    Rz1
    SiO273.3368.9968.3570.8770.1876.8273.2972.7070.1172.3369.0874.4976.2175.4276.7673.66
    TiO20.650.600.630.580.540.300.480.410.470.150.340.390.080.080.120.15
    Al2O316.5117.5615.4914.0514.3011.8713.1113.1214.9115.4016.2612.5213.5113.0913.2513.64
    Fe2O30.861.271.171.060.430.020.210.100.110.101.350.120.320.280.280.60
    FeO2.122.242.842.643.192.182.972.282.990.931.172.170.360.670.122.11
    CaO0.090.272.501.321.830.631.011.270.960.180.161.450.260.310.270.11
    MgO0.171.351.601.401.400.571.190.750.900.240.460.620.070.170.090.27
    MnO0.0050.0480.0540.0420.0660.0530.0570.0560.0660.0440.0440.0540.0250.0170.0330.026
    Na2O0.190.462.292.102.141.851.932.091.511.501.482.022.192.182.320.83
    K2O3.604.562.783.923.904.264.034.645.286.446.464.665.426.955.816.14
    P2O50.1230.1600.1840.1990.1650.1660.1740.1780.1940.1540.1730.1820.1630.1100.1240.121
    LOI (烧失量)2.162.301.941.651.711.201.432.282.372.452.931.211.360.690.792.33
    总量99.8299.8199.8499.8399.8699.9299.8799.8899.8899.9399.9199.8899.9899.9899.9799.98
    Na2O+K2O3.795.025.076.026.056.105.966.736.807.947.946.687.619.138.136.96
    K2O/Na2O18.909.871.211.871.822.302.082.223.494.284.362.312.473.182.517.43
    A/CNK3.772.841.371.391.291.351.401.221.501.581.671.141.361.121.251.66
    A/NK3.933.092.281.831.851.551.741.551.821.631.721.501.431.181.311.71
    La47.662.852.047.140.4429.2833.8131.2732.4119.3252.4031.849.8064.412.7220.9
    Ce103.0129.0100.095.381.1360.5068.1763.2166.6040.3394.9366.0323.5113130.1143.3
    Pr11.915.411.911.19.637.458.067.548.084.7213.827.842.9514.83.825.34
    Nd49.360.446.845.635.2027.3229.9028.2030.2716.5349.9829.3910.5360.313.3320.8
    Sm9.3611.28.468.377.146.495.876.046.914.0310.216.663.7511.54.465.58
    Eu2.081.361.811.471.140.651.050.890.960.671.270.920.131.250.160.35
    Gd7.809.287.396.716.136.105.215.306.563.627.316.063.689.314.234.16
    Tb1.391.551.121.190.871.180.780.791.090.671.041.050.871.541.011.16
    Dy7.288.114.996.284.737.194.494.366.474.395.476.305.927.747.038.63
    Ho1.311.530.891.200.871.390.810.771.210.840.961.201.081.301.351.80
    Er3.143.902.172.932.273.632.232.063.082.242.553.182.543.063.464.25
    Tm0.600.730.380.550.370.590.360.330.490.380.410.520.390.490.600.91
    Yb3.264.142.173.112.193.462.122.122.942.362.403.052.162.603.304.65
    Lu0.490.620.310.450.370.570.330.360.460.440.430.480.470.400.650.77
    Y30.838.821.430.223.7737.7122.5121.9833.0423.8623.6032.9831.9533.839.1250.0
    LREE222.87280.46221.26208.91174.68131.70146.86137.14145.2385.59222.61142.6950.67283.5564.6096.15
    HREE25.2729.8519.4222.4117.8124.1216.3216.0922.2814.9320.5721.8417.1226.4421.6226.33
    ΣREE248.14310.31240.67231.33192.49155.82163.19153.23167.50100.53243.18164.5367.79310.0086.23122.49
    LREE/HREE8.829.3911.399.329.815.469.008.526.525.7310.826.532.9610.722.993.65
    δEu0.7440.4080.6980.5980.5260.3180.5810.4810.4340.5370.4480.4450.1040.3700.1140.223
    δCe1.0581.0190.9881.0211.0081.0041.0121.0101.0091.0360.8651.0251.0711.0421.0591.004
    (La/Yb)N10.4810.8817.2010.8613.226.0711.4510.587.925.8615.687.483.2617.762.763.22
    (La/Sm)N3.283.633.973.633.662.913.723.343.033.103.313.081.693.621.842.42
    (Gd/Yb)N1.981.852.821.782.311.462.032.071.851.272.521.641.412.961.060.74
    Li33.456.939.246.679.6454.3747.2356.2330.7933.6171.0933.2322.3113.719.2469.8
    Be0.971.861.861.632.742.201.951.913.171.302.361.722.270.880.811.04
    Sc10.238.847.868.9310.2510.1613.6710.226.475.757.958.883.831.958.263.30
    V63.863.559.458.460.643.272.052.942.122.040.442.013.76.3320.33.43
    Cr31.927.734.528.637.525.341.324.326.713.018.918.210.81.9411.01.93
    Co2.699.8311.29.6510.24.59.86.47.82.46.84.71.21.380.22.31
    Ni7.2117.217.519.020.19.422.711.712.53.78.97.41.50.720.82.03
    Ga21.020.418.419.120.2616.9719.5919.8722.6820.2222.0316.9819.3912.718.1016.0
    Rb12316772.2175223.5275.0221.9271.5326.8360.4356.5224.0342.6266345.3332
    Sr10440.111595.3104.533.692.471.754.533.244.459.112.834.614.28.8
    Zr299315292268201.4161.4170.5177.7185.2111.9178.0196.675.510496.0104
    Nb10.810.59.1713.217.7713.3919.7816.3112.3610.0813.9313.5713.933.0413.3410.5
    In0.0830.0580.0610.0690.120.120.100.110.100.120.110.070.140.0460.100.11
    Cs6.313.78.6316.331.1423.4615.5718.1319.3716.0321.4011.059.686.648.4314.7
    Ba568638421531494.0173.6591.7516.5538.4285.3391.2401.623.054.525.335.7
    Hf10.211.410.58.837.166.185.605.629.794.827.799.543.303.713.373.54
    Ta1.111.220.821.331.400.861.681.421.501.231.471.062.150.481.461.43
    W1.991.150.921.282.862.391.020.683.813.302.631.432.162.293.111.79
    Tl0.480.700.510.781.231.290.971.321.761.611.811.011.811.281.511.47
    Pb40.838.024.232.130.925.031.334.134.742.646.028.232.244.432.033.0
    Bi0.690.860.520.560.150.270.480.650.780.651.300.300.857.521.071.49
    Th15.521.412.916.916.3511.6313.3312.1121.4611.4216.0914.8513.78.2611.4912.4
    U4.553.612.823.364.593.693.848.077.133.513.974.936.34.585.934.49
    Sn5.975.302.513.665.75.74.76.64.48.19.94.47.33.616.87.25
    As89.01.83.04.53.96.11.28.617.81.23.11.60.91.56.21.3
    Sb15.10.250.200.450.050.200.050.750.650.140.280.120.230.170.420.21
     注:样品岩石地球化学分析由河北省区域地质矿产调查研究所实验室完成。其中ηγcT119件;ηγcT21 19件;ηγcT31 10件;ηγcT61 8件,文中仅对每个侵位单元列出4个,共12个样品的分析结果。铝饱和指数A/CNK=Al2O3/(CaO+Na2O+K2O)(摩尔分数比);A/NK=Al2O3/(Na2O+K2O) (摩尔分数比),比值单位为1。主量元素含量单位为%,稀土和微量元素含量为10-6ηγcT21 —中细粒堇青黑云二长花岗岩;ηγcT21 —中粒(斑状)堇青黑云二长花岗岩;ηγcT31 —中粗粒(斑状)堇青黑云二长花岗岩;ηγcT61 —细粒堇青黑云二长花岗岩
    下载: 导出CSV 
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    将锆石样品破碎成全部通过60目的粉末 (岩石样品粒度小于0.3mm),再经过淘洗、电磁选、重液分选等步骤,分选出锆石单矿物,并根据晶型、颜色、透明度和有无明显包裹体挑选出浅棕黄色或无色自形柱状晶体。将锆石制作成环氧树脂样品靶,待样品靶固结硬化后打磨并抛光至锆石中心暴露,然后拍摄透射光、反射光及阴极发光图像。锆石UPb同位素测定在中国地质大学 (武汉) 地质过程与矿产资源国家重点实验室进行,使用的ICP-MS仪器为Elan 6100 DRC,激光剥蚀系统为德国LamdaPhysik公司的GeoLas 200M深紫外 (DUV)193nmArF准粉紫激光剥蚀系统。分析中采用的激光斑束直径为32μm,以29Si作外标,哈佛大学标准锆石91500作外标校正,分析方法及仪器参数见参考文献[12]。同位素比值、U-Pb年龄和含量计算采用Glitter 4.0程序完成,采用Anderson方法对普通Pb进行校正[13]。加权平均计算及U-Pb谐和图的绘制使用Isoplot 3.00程序完成[14]

    花岗岩各岩石样品的A/CNK值 (铝饱和指数) 范围为1.12~3.77,平均值为1.31~2.34;A/NK值范围为1.18~3.93,平均值为1.41~2.78(表 1),岩石化学组成均显示铝过饱和[15],表明其为过铝质花岗岩。全碱K2O+Na2O平均值的范围为4.97%~7.96%,由中细粒斑状堇青黑云二长花岗岩 (ηγcT11)→中粒 (斑状) 堇青黑云二长花岗岩 (ηγcT21)→中粗粒 (斑状) 堇青黑云二长花岗岩 (ηγcT31)→细粒堇青黑云二长花岗岩 (ηγcT61) 呈逐渐增高趋势;K2O/Na2O平均值为2.11~7.96,属于中高钾系列花岗岩。

    在原始地幔标准化的微量元素蛛网图 (图 2) 中,研究区各侵位单元显示出较一致的分布模式,明显富集大离子亲石元素 (LILE),包括Rb、K等,相对亏损高场强元素 (HFSE),包括Ta、Nb、Ti等。Ta、Nb、Ti的相对亏损又称“TNT”负异常,显示出与俯冲带有关的岛弧岩浆岩相似的地球化学特征[17]。4个侵位单元中细粒堇青黑云二长花岗岩 (ηγc T16) 具有比前3期更强烈的“TNT”负异常。此外,大离子亲石元素Ba、Sr也显示出相对亏损的特征,表明岩浆经历过分异演化。

    图  2  六万山印支早期花岗岩微量元素蛛网图(球粒陨石标准值据参考文献[16];图例代号同图 1
    Figure  2.  Primitive mantle-normalized spider diagrams of Early Indosinian Liuwanshan granites

    4个侵位单元花岗岩稀土元素总量 (ΣREE) 分别为231×10-6~310×10-6、153×10-6~192×10-6、100×10-6~168×10-6及67×10-6~310×10-6(表 1)。各侵位单元稀土元素总量差异较大,其中ηγc T11稀土元素总量最高,平均为257×10-6。LREE/HREE值范围为2.96~11.39,(La/Yb) N值范围为2.76~11.76,表现为稀土元素富集。其中ηγcT61的LREE/HREE值 (2.96~10.72) 及 (La/Yb) N值 (2.76~11.76) 变化范围最大,表明其轻、重稀土元素分馏程度较高。δEu值为0.104~0.744,表现出负Eu异常;δCe平均值为0.865~1.071,无明显Ce异常。Eu在还原条件下呈Eu2+而与其他3价稀土元素分离,Ce在还原条件下呈Ce3+状态,只有在氧化条件下才呈Ce4+状态与其他稀土元素分离。因此,岩体明显Eu异常,而Ce无明显异常表明,岩体演化时物理化学条件为还原环境[18]

    六万山印支早期花岗岩各侵位单元岩石稀土元素球粒陨石标准化配分曲线整体右倾,表现为轻稀土元素分异程度大于重稀土元素的“V”型曲线。总体上,各侵位单元具相似的稀土元素配分曲线 (图 3),表明其具有同源性。但ηγcT61的稀土元素配分曲线相对于其他3期侵位单元分异程度小,且负Eu异常更明显 (图 3-D)。

    图  3  六万山印支早期花岗岩稀土元素配分曲线(球粒陨石标准值据参考文献[16];图例代号见表 1
    Figure  3.  REE distribution patterns of Early Indosinian Liuwanshan granites

    六万山印支早期花岗岩SiO2-ΣREE相关曲线图显示,当SiO2含量为72%时,ΣREE值差异最大 (图 4-a)。稀土元素总量与轻稀土元素基本呈线性相关关系;而重稀土元素比较分散,相关性较差 (图 4-b)。轻、重稀土元素比值在稀土元素总量约为160×10-6、SiO2为72%时,开始出现大、小不同的差异变化,暗示了岩浆结晶分异的开始 (图 4-c)。大体上,重稀土元素含量随SiO2含量增大而增大,相应的轻、重稀土元素比值则逐渐降低。稀土元素地球化学特征显示,六万山印支早期花岗岩在稀土元素总量为150×10-6~175×10-6时为岩浆分异阶段。

    图  4  六万山印支早期花岗岩特征值相关曲线(图例代号同图 1
    Figure  4.  Characteristic value diagrams of Early Indosinian Liuwanshan granites

    δEu与ΣREE呈抛物线性关系,稀土元素总量低于175×10-6时,δEu与ΣREE正相关,稀土元素总量越高,Eu异常越弱;当稀土元素总量高于175×10-6时,δEu与ΣREE呈负相关 (图 4-d)。δEu与LREE/HREE值主要呈正相关关系,同时也表现出负相关性趋势 (图 4-e)。Zr/Y-LREE/HREE (图 4-f) 与δEu-Zr/Y均显示正相关关系,表明δEu-LREE/HREE的正相关性与花岗岩所含副矿物成分有关,这是因为花岗岩中锆石、榍石、磷灰石等副矿物富集重稀土元素,因此,含锆石等副矿物多的陆壳花岗岩δEu-LREE/HREE正相关。δEu-LREE/HREE表现出负相关关系的趋势,表明其具有洋壳岛弧花岗岩特征,通常洋壳岛弧花岗岩表现为δEu-LREE/HREE负相关的稀土元素特征[19]

    大洋中脊地幔源岩浆岩基本没有稀土元素分异,稀土元素总量高于球粒陨石,且稀土元素配分曲线显示平缓直线;而地壳尤其是上地壳岩石具有明显的轻、重稀土元素分异,并且通常伴随有Eu的负异常。Eu异常的存在或缺失通常与和岩浆平衡的斜长石的量有关[20]。例如,负Eu异常的趋势越来越大,可能表明斜长石从岩浆中持续分离出去,ηγcT61中较高的负Eu异常可能与此有关。六万山印支早期花岗岩负Eu异常整体由小到大 (图 3) 的另外一个原因可能是,岩浆前进深熔作用过程中不断有地壳物质加入的结果[20]。ΣREE的含量随分异程度提高而降低,可能是富含REE的副矿物,如磷灰石、榍石、角闪石等的分离结晶作用造成的[21]。已有研究表明,岩浆结晶分异过程中,磷灰石的溶解度决定了REE的丰度,在过铝质熔体中,磷灰石溶解度与铝饱和指数 (A/CNK) 呈线性相关关系[22]

    黑云堇青二长花岗岩的锆石颗粒大多无色透明或浅色,个别略带深褐色,粒度一般为65~120μm,多呈长柱状自形晶。部分颗粒内部具继承性锆石残核,表面可见晶棱被圆化,可能为遭受后期热液蚀变或变质作用所致。CL图像显示,几乎所有锆石都具典型的韵律振荡环带,表明锆石为岩浆成因 (图 5)。

    图  5  六万山印支早期花岗岩锆石阴极发光图像和锆石U-Pb谐和图
    Figure  5.  Cathodoluminescence images and zircon U-Pb concordia diagrams of Early Indosinian Liuwanshan granites

    锆石U-Pb测年结果显示 (表 2图 5),4个侵位单元的锆石样品均具相对集中分布的年龄值。其中样品D4054-Rz1(ηγcT11)9个分析点 (3.1、5.1、6.1、7.1、8.1、9.1、11.1、13.1、14.1) 的年龄集中在246.0±4.3~257.0±3.0Ma之间,给出的年龄加权平均值为252.8±1.9Ma (MSWD=0.92)(图 5-a);样品D2706-Rz1(ηγcT21)10个分析点 (1.1、3.1、5.1、7.1、8.1、10.1、13.1、14.1、15.1、16.1) 的年龄集中在244.0±2.6~260.0±3.4Ma之间,给出的年龄加权平均值为249.2±1.9Ma (MSWD=1.2)(图 5-b);样品PM03-29-XT1(ηγcT31)10个分析点 (1.1、3.1、4.1、5.1、7.1、9.1、10.1、11.1、12.1、15.1) 的年龄集中在241.0±2.5~255.0±4.3Ma之间,给出的年龄加权平均值为248.3±3.2Ma (MSWD=2.1)(图 5-c);样品D1218-Rz2(ηγcT61)11个分析点 (2.1、3.1、4.1、7.1、8.1、10.1、12.1、13.1、14.1、15.1、16.1) 的年龄集中在241.0±2.4~253.0±2.6Ma之间,其年龄加权平均值为246.8±2.8Ma (MSWD=2.2)(图 5-d)。这些点相对集中分布于谐和线上及其附近 (图 5),代表了岩体的侵位结晶年龄。

    表  2  六万山印支早期花岗岩单颗粒锆石U-Th-Pb同位素测定结果
    Table  2.  U-Th-Pb isotopic dating results for the single-grain zircon from Early Indosinian Liuwanshan granites

    Pb232Th238U同位素比值年龄/Ma
    /10-6207Pb/206Pb207Pb/235U206Pb/238U208Pb/232Th207Pb/206Pb207Pb/235U206Pb/238U208Pb/ 232Th
    D4054-Rz1
    1.111116629390.05260.00170.3060.0100.041940.000530.014340.0007932275.92718.12653.328816
    2.125943522190.05640.00160.4970.0170.063490.001150.023750.0006546530.641011.43977.047413
    3.1461844150.05760.00440.2490.0240.039770.000680.011770.0006151721522619.42514.223712
    4.11413646190.05300.00300.4560.0230.062430.001210.018720.0006633212838215.73907.437513
    5.17515811350.05480.00260.3010.0150.039880.000440.011920.00066467105.526711.32522.724013
    6.113015742310.04970.00160.2650.0090.038960.000700.013930.0007718975.92387.52464.328015
    7.17324210570.05490.00270.3070.0150.040570.000520.011560.0005546911427211.82563.223211
    8.17515415410.04710.00190.2630.0110.040320.000390.013550.0007110296.32379.02552.427214
    9.112549012530.05470.00230.3030.0130.040170.000430.012470.0004046794.426910.02542.62518
    10.13204049940.06840.00221.1510.0520.117490.003930.033550.0014088066.777824.571622.766727
    11.17016015690.05340.00200.2910.0110.039630.000410.011690.0006534387.02598.52512.623513
    12.124924413790.06970.00201.0190.0340.104840.001800.038250.0013892063.971317.164310.575927
    13.114112143430.05680.00170.3210.0100.040600.000480.016910.0010948364.82838.02573.033922
    14.15913113560.05150.00240.2790.0130.039700.000410.013390.0007826510724910.02512.526916
    15.1991769160.05720.00220.6290.0390.074030.003080.021720.0012850285.249524.146018.543425
    16.17812911160.06180.00250.5620.0300.062750.002020.016010.0009873380.545319.239212.232120
    D2706-Rz1
    1.1420.05250.00280.2480.0150.039180.000500.011350.0009031613722511.82483.122818
    2.1641939810.05290.00250.3840.0210.050120.001200.012560.0006632410733015.73157.325213
    3.15412211060.05550.00260.3070.0140.040470.000460.016100.0008343210427210.72562.932317
    4.12142934950.07090.00231.4990.0520.152550.002220.044670.0012895467.893021.091512.488325
    5.1561997830.05310.00290.3000.0170.041100.000550.013560.0006433211926613.02603.427213
    6.119239312400.09820.00391.1560.0650.077360.002580.023880.00151159172.778030.548015.447730
    7.16017212310.05540.00240.3020.0130.039400.000450.012930.0007142896.326810.32492.826014
    8.1542585490.05250.00360.2130.0190.039740.000590.012300.0006031787.819616.02513.724712
    9.116826912780.07580.00310.9790.0640.082110.003010.028370.00170110083.369332.750917.956633
    10.18021816500.05040.00190.2750.0100.039400.000380.012700.0005621785.22478.12492.425511
    11.115811418540.06410.00140.8490.0200.095350.000980.024300.0011674647.162410.95875.848523
    12.1541157480.04980.00250.3590.0190.052630.001090.020040.0010918311931214.13316.740122
    13.14916310400.05040.00230.2750.0130.039640.000450.010300.0006821310724710.02512.820714
    14.14815510080.04950.00250.2630.0130.038610.000420.011350.0007116911423710.62442.622814
    15.1492046180.05340.00340.2880.0180.039370.000560.011720.0006034614325714.22493.523612
    16.1723986190.04990.00320.2680.0170.039180.000510.011300.0004219115624113.62483.22278
    PM03-29-Rz1
    1.1430.05100.00270.2740.0140.039310.004930.011930.0006124312224611.42493.124012
    2.117232551600.05030.00130.2540.0080.036450.000610.012380.0005020993.52296.22313.824910
    3.16314415690.05020.00200.2640.0100.038160.000390.013460.0008820686.12388.22412.527018
    4.1401735970.04940.00330.2660.0170.039840.000530.011550.0006316515224013.92523.323213
    5.1461667960.04820.00270.2630.0150.040200.000490.012940.0006810912623711.72543.126014
    6.123918318430.06680.00250.9740.0830.089520.005250.044680.0034283377.869142.755331.188466
    7.16019410930.05120.00220.2800.0120.039690.000450.012950.0006325698.12519.32512.826013
    8.19425419120.04840.00180.2820.0120.041860.000710.014980.0006811791.72539.62644.430114
    9.1361654100.05660.00520.3000.0270.039560.000640.013090.0006747623826721.22504.026314
    10.1421844930.04980.00460.2200.0240.040330.000690.013950.0007518778.620220.32554.328015
    PM03-29-Rz1
    11.1562227990.05290.00290.2800.0150.038430.000470.012820.0005532412425112.02432.925711
    12.1401087720.05600.00300.3020.0150.039380.000460.014940.0010245011926812.02492.930020
    13.1996017510.05030.00290.2450.0160.039930.000540.012190.0004120889.122213.32523.42458
    14.18219712280.04830.00190.3360.0170.049190.001290.017460.0008711786.129412.73108.035017
    15.17226111800.04980.00230.2660.0110.039130.000460.013630.000541871102399.02472.927411
    16.13548108520.06390.00220.7090.0320.078520.002170.032830.0008973974.154418.948713.065318
    D1218-Rz2
    1.15314211410.05370.00220.3630.0170.048600.000960.013360.0006236794.431512.33065.926812
    2.17918717240.05210.00300.2780.0160.039270.000540.012830.0005030013024912.62483.425810
    3.16523310680.05170.00200.2770.0100.039080.000410.011770.0004027288.92488.02472.62368
    4.110815316010.05030.00230.2630.0120.038070.000390.012660.000532091102379.32412.425411
    5.1951425160.05750.00390.4170.0310.052200.001420.019040.0006650915035422.13288.738113
    6.1602616920.05170.00210.2920.0120.040840.000520.011560.0005833395.42609.62583.223212
    7.1341533390.05270.00300.2760.0160.038660.000580.010740.0003732212524812.32453.62168
    8.11252018740.05890.00240.3090.0130.038360.000480.011220.0005356586.12739.82433.022511
    9.1642498820.05370.00170.3210.0120.043160.000800.013440.0006236774.12838.92724.927012
    10.1581647050.05310.00200.2810.0100.038490.000370.011140.0003733287.02528.22432.32247
    11.16214012920.05760.00230.3470.0140.043570.000480.014400.0005451788.930210.62753.028911
    12.1652858660.04950.00310.2650.0160.039580.000560.011310.0005017214423912.72503.522710
    13.1451559640.05400.00190.2990.0100.040070.000410.010850.0004136977.82668.12532.62188
    14.11464193530.05550.00310.3020.0170.039800.000510.011950.0004343512626813.02523.22409
    15.11276989570.05440.00220.2910.0120.038860.000410.011390.0004638790.72609.22462.62299
    16.11955791230.05470.00200.2990.0110.039540.000430.012110.0003539878.72668.92502.72437
    下载: 导出CSV 
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    早期研究认为,六万山复式岩体的侵位从晚二叠世258Ma到中三叠世240Ma (黑云母40Ar-39Ar、K-Ar法)[3]。邓希光等[7]利用高精度SHRMP锆石U-Pb测年研究表明,六万山岩体形成年龄为233±5Ma;最新对六万山永安花岗岩进行的LA-ICPMS锆石U-Pb测年结果为231.8±2.7Ma[23]。这些年龄值存在差异,且获得的年龄均为六万山复式岩体解体之前的年龄值,不能很好地反映六万山复式岩体印支早期各侵位单元的年龄。覃小峰等[10]利用黑云母40Ar-39Ar和K-Ar法获得了六万山复式岩体解体后的年龄分别为242Ma (ηγcT11)、255Ma (ηγcT21)、258Ma (ηγcT31)、239Ma (ηγcT61),但由于黑云母40Ar-39Ar和K-Ar法测年本身可靠程度偏低,且得到的年龄值与岩体实际侵位先后顺序存在一定矛盾,故同样不能精确约束各侵位单元的形成时代。此次研究获得六万山4个期次黑云堇青二长花岗岩的锆石U-Pb年龄分别为:252.8±1.9Ma (ηγcT11)、249.2±1.9Ma (ηγcT21)、248.3±3.2Ma (ηγcT31)、246.8±2.8Ma (ηγcT61)。该年龄值与研究区内印支早期花岗岩的总体形成年代 (240~258Ma) 具有较好的一致性[3],且与岩体侵入序次相符合。由此表明,该岩体形成于印支早期。

    关于大容山-十万大山花岗岩体的成因,前人主要有以下3种认识:①中生代洋盆或洋陆俯冲作用,是岛弧环境的产物[24];覃小峰等[5] ①进一步指出,其应为古特提斯俯冲消减或是扬子板块和华夏板块之间的洋壳岩石圈向北俯冲形成的岩浆弧;②印支期推覆构造引起地壳叠置加厚作用的结果[7, 25]。印支期由于印支板块向北东方向运移碰撞,使得古特提斯洋关闭,同时Izanagi板块向北运动,导致云开地块再次向北西推挤碰撞,引发大规模逆冲断裂[26];③由碰撞造山作用形成的造山花岗岩[27-28]

    花岗岩岩石化学组成显示,六万山印支早期花岗岩各侵位单元均具富钾、铝过饱和的特征。岩体含过铝质矿物堇青石,属S型花岗岩[4, 9, 29]。部分熔融与分离结晶模型 (La/Sm-La) 显示,花岗岩主要由部分熔融作用形成,演化过程经历了一定程度的分离结晶作用 (图 6)。六万山印支早期花岗岩岩浆物源来自存留年龄不同的地壳物源区,负Eu异常的不断增大可能是岩浆前进深熔作用过程中,不断有地壳物质加入的结果[20]

    图  6  六万山印支早期花岗岩La-La/Sm图解(图例代号同图 1
    Figure  6.  La-La/Sm diagram of Early Indosinian Liuwanshan granites

    六万山印支早期花岗岩微量元素具有较低含量的Nb和Ta (表 1),在原始地幔标准化蛛网图中,相对富集大离子亲石元素 (Rb、K等),而相对于相邻元素K、La、Eu、Dy,明显亏损高场强元素Ti、Nb、Ta (图 2),即“TNT”负异常,显示出岛弧花岗岩的特征[17]。具有负Eu异常,同时具有较高的REE含量 (ΣREE=60 × 10-6~499 × 10-6) 和LREE/HREE值 (8.9~56) 的花岗岩,通常形成于大陆边缘环境[21]。六万山印支早期花岗岩ΣREE为67.79 × 10-6~310.31×10-6,LREE/HREE=2.96~11.3,暗示其形成于活动大陆边缘环境。

    六万山印支早期花岗岩为过铝质花岗岩、富含堇青石,且其成岩物质主要来源于地壳[4, 9, 20, 29]。该类花岗岩属Barbarin提出的含堇青石过铝质花岗岩 (CPG),其形成的构造背景为陆-陆碰撞环境[30-31]。同时,六万山印支早期花岗岩的微量元素特征反映出一定的岛弧花岗岩的地球化学特征。在构造环境判别图解[32](图 7) 中,早期侵位的岩体ηγcT11大多数落入火山弧区域,而较晚侵位的ηγcT21ηγcT31ηγcT61岩体大多落入同碰撞岩浆岩区。因此,笔者认为,六万山印支早期花岗岩经历了早期洋-陆俯冲阶段到晚期陆-陆碰撞阶段的构造演化过程,与区域上钦-防构造带西南段印支早期花岗岩具有相似的演化过程[5]

    图  7  六万山印支早期花岗岩的构造环境判别图解(图例代号同图 1
    VAG—火山弧花岗岩;syn-COLG—同碰撞期花岗岩;WPG—板内型花岗岩;ORG—洋中脊型花岗岩
    Figure  7.  Discrimination diagrams illustrating tectonic setting of Early Indosinian Liuwanshan granites

    (1) 六万山印支早期花岗岩体由同源不同阶段侵入的中细粒斑状堇青黑云二长花岗岩 (ηγcT11)、中粒 (斑状) 堇青黑云二长花岗岩 (ηγcT21)、中粗粒 (斑状) 堇青黑云二长花岗岩 (ηγcT31)、细粒堇青黑云二长花岗岩 (ηγcT61) 组成。LA-ICP-MS锆石U-Pb定年结果显示,由ηγcT11ηγcT61其侵位年龄分别为252.8±1.9Ma、249.2±1.9Ma、248.3±3.2Ma、246.8±2.8Ma。

    (2) 花岗岩各侵位单元岩石稀土元素球粒陨石标准化配分曲线整体右倾,具明显的负Eu异常,表现为轻稀土元素分异程度大于重稀土元素。其中细粒堇青黑云二长花岗岩 (ηγcT61) 的稀土元素配分曲线相对于其他3期侵位单元,斜率较小,且负Eu异常更明显,是岩浆前进深熔作用地壳物质不断加入的结果。

    (3) 当SiO2含量为72%时,稀土元素总量高低差异最大。稀土元素总量与轻稀土元素基本呈线性相关关系;而重稀土元素比较分散,相关性较差。轻、重稀土元素比值在稀土元素总量约为160×10-6、SiO2含量为72%时,开始出现大、小不同的差异变化。稀土元素地球化学特征显示,六万山印支早期花岗岩在稀土元素总量为150×10-6~175×10-6时为岩浆分异阶段。

    (4) 研究区印支早期花岗岩属过铝质中高钾系列岩石,总体上显示出富集大离子亲石元素 (如Rb、K等),相对亏损高场强元素 (如Ta、Nb、Ti等),反映出与俯冲带有关岛弧岩浆岩相似的地球化学特征。

    (5) 六万山印支早期花岗岩形成于活动大陆边缘环境,其形成经历了早期洋-陆俯冲到晚期陆-陆碰撞阶段的构造演化过程。

    致谢: 成文过程中得到东华理工大学谢财富教授、武汉地质矿产研究所赵小明、龙文国研究员及广西地调院教授级高工邓军的指导和帮助,在此一并致以衷心谢意。
  • 图  1   大容山-十万大山花岗岩带地质简图(据参考文献[3-4]修改)

    Figure  1.   Geological sketch map of the Darongshan-Shiwandashan granites belt

    图版Ⅰ   A.中细粒斑状堇青黑云二长花岗岩(ηγcT11);B.中粒(斑状)堇青黑云二长花岗岩(ηγcT21);C.中粗粒(斑状)堇青黑云二长花岗岩(ηγcT31);D.细粒堇青黑云二长花岗岩(ηγcT61);E. ηγcT11镜下特征(正交偏光);F. ηγcT31镜下特征(正交偏光)。Q—石英;Kfs—钾长石;Pl—斜长石;Bt—黑云母;Crd—董青石

    图  2   六万山印支早期花岗岩微量元素蛛网图(球粒陨石标准值据参考文献[16];图例代号同图 1

    Figure  2.   Primitive mantle-normalized spider diagrams of Early Indosinian Liuwanshan granites

    图  3   六万山印支早期花岗岩稀土元素配分曲线(球粒陨石标准值据参考文献[16];图例代号见表 1

    Figure  3.   REE distribution patterns of Early Indosinian Liuwanshan granites

    图  4   六万山印支早期花岗岩特征值相关曲线(图例代号同图 1

    Figure  4.   Characteristic value diagrams of Early Indosinian Liuwanshan granites

    图  5   六万山印支早期花岗岩锆石阴极发光图像和锆石U-Pb谐和图

    Figure  5.   Cathodoluminescence images and zircon U-Pb concordia diagrams of Early Indosinian Liuwanshan granites

    图  6   六万山印支早期花岗岩La-La/Sm图解(图例代号同图 1

    Figure  6.   La-La/Sm diagram of Early Indosinian Liuwanshan granites

    图  7   六万山印支早期花岗岩的构造环境判别图解(图例代号同图 1

    VAG—火山弧花岗岩;syn-COLG—同碰撞期花岗岩;WPG—板内型花岗岩;ORG—洋中脊型花岗岩

    Figure  7.   Discrimination diagrams illustrating tectonic setting of Early Indosinian Liuwanshan granites

    表  1   六万山印支早期花岗岩主量、微量和稀土元素组成及其相关参数

    Table  1   Major, trace elements and REE composition and related parameters of Early Indosinian Liuwanshan granites

    侵位单元
    样品编号
    ηγcT11ηγcT21ηγcT31ηγcT61
    D4054-
    Rz1
    D4059-
    Rz1
    D5170-
    Rz1
    D5174-
    Rz1
    D2706-
    Rz1
    D1210-
    Rz1
    D2682-
    Rz1
    D1054-
    TW1
    PM03-37-
    Rz1
    PM03-
    43-GSY
    PM03-
    9-XT1
    D2524-
    Rz1
    PM03-
    41-Rz1
    D5361-
    Rz2
    D1218-
    Rz2
    D5475-
    Rz1
    SiO273.3368.9968.3570.8770.1876.8273.2972.7070.1172.3369.0874.4976.2175.4276.7673.66
    TiO20.650.600.630.580.540.300.480.410.470.150.340.390.080.080.120.15
    Al2O316.5117.5615.4914.0514.3011.8713.1113.1214.9115.4016.2612.5213.5113.0913.2513.64
    Fe2O30.861.271.171.060.430.020.210.100.110.101.350.120.320.280.280.60
    FeO2.122.242.842.643.192.182.972.282.990.931.172.170.360.670.122.11
    CaO0.090.272.501.321.830.631.011.270.960.180.161.450.260.310.270.11
    MgO0.171.351.601.401.400.571.190.750.900.240.460.620.070.170.090.27
    MnO0.0050.0480.0540.0420.0660.0530.0570.0560.0660.0440.0440.0540.0250.0170.0330.026
    Na2O0.190.462.292.102.141.851.932.091.511.501.482.022.192.182.320.83
    K2O3.604.562.783.923.904.264.034.645.286.446.464.665.426.955.816.14
    P2O50.1230.1600.1840.1990.1650.1660.1740.1780.1940.1540.1730.1820.1630.1100.1240.121
    LOI (烧失量)2.162.301.941.651.711.201.432.282.372.452.931.211.360.690.792.33
    总量99.8299.8199.8499.8399.8699.9299.8799.8899.8899.9399.9199.8899.9899.9899.9799.98
    Na2O+K2O3.795.025.076.026.056.105.966.736.807.947.946.687.619.138.136.96
    K2O/Na2O18.909.871.211.871.822.302.082.223.494.284.362.312.473.182.517.43
    A/CNK3.772.841.371.391.291.351.401.221.501.581.671.141.361.121.251.66
    A/NK3.933.092.281.831.851.551.741.551.821.631.721.501.431.181.311.71
    La47.662.852.047.140.4429.2833.8131.2732.4119.3252.4031.849.8064.412.7220.9
    Ce103.0129.0100.095.381.1360.5068.1763.2166.6040.3394.9366.0323.5113130.1143.3
    Pr11.915.411.911.19.637.458.067.548.084.7213.827.842.9514.83.825.34
    Nd49.360.446.845.635.2027.3229.9028.2030.2716.5349.9829.3910.5360.313.3320.8
    Sm9.3611.28.468.377.146.495.876.046.914.0310.216.663.7511.54.465.58
    Eu2.081.361.811.471.140.651.050.890.960.671.270.920.131.250.160.35
    Gd7.809.287.396.716.136.105.215.306.563.627.316.063.689.314.234.16
    Tb1.391.551.121.190.871.180.780.791.090.671.041.050.871.541.011.16
    Dy7.288.114.996.284.737.194.494.366.474.395.476.305.927.747.038.63
    Ho1.311.530.891.200.871.390.810.771.210.840.961.201.081.301.351.80
    Er3.143.902.172.932.273.632.232.063.082.242.553.182.543.063.464.25
    Tm0.600.730.380.550.370.590.360.330.490.380.410.520.390.490.600.91
    Yb3.264.142.173.112.193.462.122.122.942.362.403.052.162.603.304.65
    Lu0.490.620.310.450.370.570.330.360.460.440.430.480.470.400.650.77
    Y30.838.821.430.223.7737.7122.5121.9833.0423.8623.6032.9831.9533.839.1250.0
    LREE222.87280.46221.26208.91174.68131.70146.86137.14145.2385.59222.61142.6950.67283.5564.6096.15
    HREE25.2729.8519.4222.4117.8124.1216.3216.0922.2814.9320.5721.8417.1226.4421.6226.33
    ΣREE248.14310.31240.67231.33192.49155.82163.19153.23167.50100.53243.18164.5367.79310.0086.23122.49
    LREE/HREE8.829.3911.399.329.815.469.008.526.525.7310.826.532.9610.722.993.65
    δEu0.7440.4080.6980.5980.5260.3180.5810.4810.4340.5370.4480.4450.1040.3700.1140.223
    δCe1.0581.0190.9881.0211.0081.0041.0121.0101.0091.0360.8651.0251.0711.0421.0591.004
    (La/Yb)N10.4810.8817.2010.8613.226.0711.4510.587.925.8615.687.483.2617.762.763.22
    (La/Sm)N3.283.633.973.633.662.913.723.343.033.103.313.081.693.621.842.42
    (Gd/Yb)N1.981.852.821.782.311.462.032.071.851.272.521.641.412.961.060.74
    Li33.456.939.246.679.6454.3747.2356.2330.7933.6171.0933.2322.3113.719.2469.8
    Be0.971.861.861.632.742.201.951.913.171.302.361.722.270.880.811.04
    Sc10.238.847.868.9310.2510.1613.6710.226.475.757.958.883.831.958.263.30
    V63.863.559.458.460.643.272.052.942.122.040.442.013.76.3320.33.43
    Cr31.927.734.528.637.525.341.324.326.713.018.918.210.81.9411.01.93
    Co2.699.8311.29.6510.24.59.86.47.82.46.84.71.21.380.22.31
    Ni7.2117.217.519.020.19.422.711.712.53.78.97.41.50.720.82.03
    Ga21.020.418.419.120.2616.9719.5919.8722.6820.2222.0316.9819.3912.718.1016.0
    Rb12316772.2175223.5275.0221.9271.5326.8360.4356.5224.0342.6266345.3332
    Sr10440.111595.3104.533.692.471.754.533.244.459.112.834.614.28.8
    Zr299315292268201.4161.4170.5177.7185.2111.9178.0196.675.510496.0104
    Nb10.810.59.1713.217.7713.3919.7816.3112.3610.0813.9313.5713.933.0413.3410.5
    In0.0830.0580.0610.0690.120.120.100.110.100.120.110.070.140.0460.100.11
    Cs6.313.78.6316.331.1423.4615.5718.1319.3716.0321.4011.059.686.648.4314.7
    Ba568638421531494.0173.6591.7516.5538.4285.3391.2401.623.054.525.335.7
    Hf10.211.410.58.837.166.185.605.629.794.827.799.543.303.713.373.54
    Ta1.111.220.821.331.400.861.681.421.501.231.471.062.150.481.461.43
    W1.991.150.921.282.862.391.020.683.813.302.631.432.162.293.111.79
    Tl0.480.700.510.781.231.290.971.321.761.611.811.011.811.281.511.47
    Pb40.838.024.232.130.925.031.334.134.742.646.028.232.244.432.033.0
    Bi0.690.860.520.560.150.270.480.650.780.651.300.300.857.521.071.49
    Th15.521.412.916.916.3511.6313.3312.1121.4611.4216.0914.8513.78.2611.4912.4
    U4.553.612.823.364.593.693.848.077.133.513.974.936.34.585.934.49
    Sn5.975.302.513.665.75.74.76.64.48.19.94.47.33.616.87.25
    As89.01.83.04.53.96.11.28.617.81.23.11.60.91.56.21.3
    Sb15.10.250.200.450.050.200.050.750.650.140.280.120.230.170.420.21
     注:样品岩石地球化学分析由河北省区域地质矿产调查研究所实验室完成。其中ηγcT119件;ηγcT21 19件;ηγcT31 10件;ηγcT61 8件,文中仅对每个侵位单元列出4个,共12个样品的分析结果。铝饱和指数A/CNK=Al2O3/(CaO+Na2O+K2O)(摩尔分数比);A/NK=Al2O3/(Na2O+K2O) (摩尔分数比),比值单位为1。主量元素含量单位为%,稀土和微量元素含量为10-6ηγcT21 —中细粒堇青黑云二长花岗岩;ηγcT21 —中粒(斑状)堇青黑云二长花岗岩;ηγcT31 —中粗粒(斑状)堇青黑云二长花岗岩;ηγcT61 —细粒堇青黑云二长花岗岩
    下载: 导出CSV

    表  2   六万山印支早期花岗岩单颗粒锆石U-Th-Pb同位素测定结果

    Table  2   U-Th-Pb isotopic dating results for the single-grain zircon from Early Indosinian Liuwanshan granites


    Pb232Th238U同位素比值年龄/Ma
    /10-6207Pb/206Pb207Pb/235U206Pb/238U208Pb/232Th207Pb/206Pb207Pb/235U206Pb/238U208Pb/ 232Th
    D4054-Rz1
    1.111116629390.05260.00170.3060.0100.041940.000530.014340.0007932275.92718.12653.328816
    2.125943522190.05640.00160.4970.0170.063490.001150.023750.0006546530.641011.43977.047413
    3.1461844150.05760.00440.2490.0240.039770.000680.011770.0006151721522619.42514.223712
    4.11413646190.05300.00300.4560.0230.062430.001210.018720.0006633212838215.73907.437513
    5.17515811350.05480.00260.3010.0150.039880.000440.011920.00066467105.526711.32522.724013
    6.113015742310.04970.00160.2650.0090.038960.000700.013930.0007718975.92387.52464.328015
    7.17324210570.05490.00270.3070.0150.040570.000520.011560.0005546911427211.82563.223211
    8.17515415410.04710.00190.2630.0110.040320.000390.013550.0007110296.32379.02552.427214
    9.112549012530.05470.00230.3030.0130.040170.000430.012470.0004046794.426910.02542.62518
    10.13204049940.06840.00221.1510.0520.117490.003930.033550.0014088066.777824.571622.766727
    11.17016015690.05340.00200.2910.0110.039630.000410.011690.0006534387.02598.52512.623513
    12.124924413790.06970.00201.0190.0340.104840.001800.038250.0013892063.971317.164310.575927
    13.114112143430.05680.00170.3210.0100.040600.000480.016910.0010948364.82838.02573.033922
    14.15913113560.05150.00240.2790.0130.039700.000410.013390.0007826510724910.02512.526916
    15.1991769160.05720.00220.6290.0390.074030.003080.021720.0012850285.249524.146018.543425
    16.17812911160.06180.00250.5620.0300.062750.002020.016010.0009873380.545319.239212.232120
    D2706-Rz1
    1.1420.05250.00280.2480.0150.039180.000500.011350.0009031613722511.82483.122818
    2.1641939810.05290.00250.3840.0210.050120.001200.012560.0006632410733015.73157.325213
    3.15412211060.05550.00260.3070.0140.040470.000460.016100.0008343210427210.72562.932317
    4.12142934950.07090.00231.4990.0520.152550.002220.044670.0012895467.893021.091512.488325
    5.1561997830.05310.00290.3000.0170.041100.000550.013560.0006433211926613.02603.427213
    6.119239312400.09820.00391.1560.0650.077360.002580.023880.00151159172.778030.548015.447730
    7.16017212310.05540.00240.3020.0130.039400.000450.012930.0007142896.326810.32492.826014
    8.1542585490.05250.00360.2130.0190.039740.000590.012300.0006031787.819616.02513.724712
    9.116826912780.07580.00310.9790.0640.082110.003010.028370.00170110083.369332.750917.956633
    10.18021816500.05040.00190.2750.0100.039400.000380.012700.0005621785.22478.12492.425511
    11.115811418540.06410.00140.8490.0200.095350.000980.024300.0011674647.162410.95875.848523
    12.1541157480.04980.00250.3590.0190.052630.001090.020040.0010918311931214.13316.740122
    13.14916310400.05040.00230.2750.0130.039640.000450.010300.0006821310724710.02512.820714
    14.14815510080.04950.00250.2630.0130.038610.000420.011350.0007116911423710.62442.622814
    15.1492046180.05340.00340.2880.0180.039370.000560.011720.0006034614325714.22493.523612
    16.1723986190.04990.00320.2680.0170.039180.000510.011300.0004219115624113.62483.22278
    PM03-29-Rz1
    1.1430.05100.00270.2740.0140.039310.004930.011930.0006124312224611.42493.124012
    2.117232551600.05030.00130.2540.0080.036450.000610.012380.0005020993.52296.22313.824910
    3.16314415690.05020.00200.2640.0100.038160.000390.013460.0008820686.12388.22412.527018
    4.1401735970.04940.00330.2660.0170.039840.000530.011550.0006316515224013.92523.323213
    5.1461667960.04820.00270.2630.0150.040200.000490.012940.0006810912623711.72543.126014
    6.123918318430.06680.00250.9740.0830.089520.005250.044680.0034283377.869142.755331.188466
    7.16019410930.05120.00220.2800.0120.039690.000450.012950.0006325698.12519.32512.826013
    8.19425419120.04840.00180.2820.0120.041860.000710.014980.0006811791.72539.62644.430114
    9.1361654100.05660.00520.3000.0270.039560.000640.013090.0006747623826721.22504.026314
    10.1421844930.04980.00460.2200.0240.040330.000690.013950.0007518778.620220.32554.328015
    PM03-29-Rz1
    11.1562227990.05290.00290.2800.0150.038430.000470.012820.0005532412425112.02432.925711
    12.1401087720.05600.00300.3020.0150.039380.000460.014940.0010245011926812.02492.930020
    13.1996017510.05030.00290.2450.0160.039930.000540.012190.0004120889.122213.32523.42458
    14.18219712280.04830.00190.3360.0170.049190.001290.017460.0008711786.129412.73108.035017
    15.17226111800.04980.00230.2660.0110.039130.000460.013630.000541871102399.02472.927411
    16.13548108520.06390.00220.7090.0320.078520.002170.032830.0008973974.154418.948713.065318
    D1218-Rz2
    1.15314211410.05370.00220.3630.0170.048600.000960.013360.0006236794.431512.33065.926812
    2.17918717240.05210.00300.2780.0160.039270.000540.012830.0005030013024912.62483.425810
    3.16523310680.05170.00200.2770.0100.039080.000410.011770.0004027288.92488.02472.62368
    4.110815316010.05030.00230.2630.0120.038070.000390.012660.000532091102379.32412.425411
    5.1951425160.05750.00390.4170.0310.052200.001420.019040.0006650915035422.13288.738113
    6.1602616920.05170.00210.2920.0120.040840.000520.011560.0005833395.42609.62583.223212
    7.1341533390.05270.00300.2760.0160.038660.000580.010740.0003732212524812.32453.62168
    8.11252018740.05890.00240.3090.0130.038360.000480.011220.0005356586.12739.82433.022511
    9.1642498820.05370.00170.3210.0120.043160.000800.013440.0006236774.12838.92724.927012
    10.1581647050.05310.00200.2810.0100.038490.000370.011140.0003733287.02528.22432.32247
    11.16214012920.05760.00230.3470.0140.043570.000480.014400.0005451788.930210.62753.028911
    12.1652858660.04950.00310.2650.0160.039580.000560.011310.0005017214423912.72503.522710
    13.1451559640.05400.00190.2990.0100.040070.000410.010850.0004136977.82668.12532.62188
    14.11464193530.05550.00310.3020.0170.039800.000510.011950.0004343512626813.02523.22409
    15.11276989570.05440.00220.2910.0120.038860.000410.011390.0004638790.72609.22462.62299
    16.11955791230.05470.00200.2990.0110.039540.000430.012110.0003539878.72668.92502.72437
    下载: 导出CSV
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  • 收稿日期:  2015-09-29
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