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冈底斯南带东段日多地区米忍岩体地球化学、年代学、锆石Lu-Hf同位素特征及其地质意义

乔新星, 周斌, 韩奎, 潘亮, 王峰, 赵焕强

乔新星, 周斌, 韩奎, 潘亮, 王峰, 赵焕强. 2019: 冈底斯南带东段日多地区米忍岩体地球化学、年代学、锆石Lu-Hf同位素特征及其地质意义. 地质通报, 38(9): 1417-1430.
引用本文: 乔新星, 周斌, 韩奎, 潘亮, 王峰, 赵焕强. 2019: 冈底斯南带东段日多地区米忍岩体地球化学、年代学、锆石Lu-Hf同位素特征及其地质意义. 地质通报, 38(9): 1417-1430.
QIAO Xinxing, ZHOU Bin, HAN Kui, PAN Liang, WANG Feng, ZHAO Huanqiang. 2019: Geochemistry, chronology and zircon Lu-Hf isotopic characteristics of the Miren rocks in Riduo area of east part of Southern Gangdise belt and their geological significance. Geological Bulletin of China, 38(9): 1417-1430.
Citation: QIAO Xinxing, ZHOU Bin, HAN Kui, PAN Liang, WANG Feng, ZHAO Huanqiang. 2019: Geochemistry, chronology and zircon Lu-Hf isotopic characteristics of the Miren rocks in Riduo area of east part of Southern Gangdise belt and their geological significance. Geological Bulletin of China, 38(9): 1417-1430.

冈底斯南带东段日多地区米忍岩体地球化学、年代学、锆石Lu-Hf同位素特征及其地质意义

基金项目: 

中国地质调查局项目《西藏日多地区1:5万区域地质调查》 121201010000150014

详细信息
    作者简介:

    乔新星(1989-), 男, 本科, 工程师, 从事区域地质调查、地球化学研究工作。E-mail:dbxxqz@163.com

  • 中图分类号: P591;P597+.3

Geochemistry, chronology and zircon Lu-Hf isotopic characteristics of the Miren rocks in Riduo area of east part of Southern Gangdise belt and their geological significance

  • 摘要:

    日多地区米忍岩体位于冈底斯南带东段,2件锆石U-Pb测年样品显示其形成年龄为54.9±1.6Ma和48.6±0.5Ma,岩石SiO2含量为60.18%~71.53%,全碱含量为5.85%~7.49%,K2O/Na2O值为0.58~1.05,里特曼指数在1.79~2.30之间,属钙碱性岩石,A/CNK值为0.85~0.95,投图显示为准铝质岩石,具有I型花岗岩的特征。岩石轻稀土元素及大离子亲石元素(Rb、K、Ba、Th、U)相对富集,重稀土及高场强元素(Nb、P、Hf、Ti)相对亏损,弱负Eu异常,具火山弧岩浆岩地球化学特征。176Hf/177Hf平均值为0.282945,Hf同位素二阶段模式年龄较年轻(613~719Ma),εHf(t)值为2.74~10.47,表明其岩浆源区以新生地壳的部分熔融为主或有地幔物质参与了成岩过程,据C/MF-A/MF投图分析,可能为基性或铁镁质岩浆底侵,导致中下地壳的物质发生熔融,这些特征均表明,日多地区始新世花岗闪长岩的形成可能与新特提斯洋板片的回转、断离有关。

    Abstract:

    The Miren rock in the Riduo Area is located in the eastern part of southern Gangdise belt. Zircon U-Pb dating of two samples reveals that the formation ages are 54.9±1.6Ma and 48.6±0.5Ma, and SiO2 content of the rock is 60.18%~71.53%, total alkali content is 5.85%~7.49%, K2O/Na2O ratio is 0.58~1.05, and Liteman index (σ) is 1.79~2.30, suggesting calc-alkaline rocks, with A/CNK value being 0.85~0.95. The diagram shows a quasi-aluminous rock with characteristics of type I granite. The light rare earth and large lithosphere ionic elements (Rb, K, Ba, Th, and U) are relatively enriched, and the characteristics of heavy rare earth and high-field strength elements (Nb, P, Hf, Ti) are relatively depleted with weak negative Eu anomalies, showing features of volcanic arc magma. The ratio of 176Hf/177Hf is 0.282819~0.283036, 0.282945 on average. The Hf isotope two-stage model is younger (613~719Ma) and the εHf(t) value is between 2.74 and 10.47, indicating that the magma source area was part of the new genetic crust. Melting or mantle material was involved in the rock-forming process. According to C/MF-A/MF mapping analysis, it may be basic or iron-magnesian magmatic intrusion, resulting in melting of material in the middle and lower crust. The formation of the Riduo granodiorite may have been related to the rotation and separation of the Neo-Tethys plate.

  • 蛇绿岩是一种可与现代大洋岩石圈对比的镁铁-超镁铁质岩石组合,在古洋消减、大陆造山带形成过程中,以构造侵位的方式产在造山带中,作为重大地质界线和板块缝合边界受到地学界的广泛关注[1],可以为古板块构造格局恢复、造山带演化、变形作用过程重建、深源成矿作用等研究提供重要信息,被广泛应用于全球板块构造系统研究,是目前人类探测地球深部物质组成的最好窗口[2-6]

    北疆地区东准噶尔造山带位于阿尔泰造山带和天山造山带之间,其古生代以来的大地构造演化是显生宙亚洲大陆增长和古亚洲洋演化的重要阶段,同时也涉及当今有关大陆造山带模型等重要理论问题[7-14]。然而东准噶尔构造带古生代以来的构造演化迄今未形成共识,尤其是对其中的蛇绿岩时代、构造属性、就位环境等存在争议[9-11, 14-18]。东准噶尔造山带大地构造相解剖表明[9-13, 19],自北向南由一系列岛弧杂岩带和增生楔杂岩组成,其大地构造相自北向南大致包括都拉特复合岛弧、阿尔曼太蛇绿岩、野马泉复合岛弧、卡拉麦里蛇绿岩、将军庙增生杂岩,研究区集中于争议较大的阿尔曼太蛇绿岩带(图 1),通过对蛇绿岩中基性岩块的岩石学和地球化学研究,探讨其岩石成因及地质意义。

    图  1  阿尔曼太蛇绿岩分布略图
    Q—第四系;O1—2Q—青河岩群;O3bs—晚奥陶世巴斯他乌组;D1t—早泥盆世托让格库都克组;D1k—早泥盆世康布铁堡组;D2k—中泥盆世库鲁木迪组;D2b—中泥盆世巴尔雷克组;D3kx—晚泥盆世卡希翁组;D3C1j—晚泥盆世-早石炭世江孜尔库都克组;C1j—早石炭世姜巴斯套组;C2b—中石炭世巴塔玛依内山组;Σ—札河坝-阿尔曼太蛇绿岩;γδοD—泥盆纪英云闪长岩;γβC—石炭纪黑云母花岗岩;ξγC—石炭纪正长花岗岩
    Figure  1.  Distribution map of Armantai ophiolite

    前人研究认为,阿尔曼太蛇绿岩为SSZ型蛇绿岩,产于岛弧、弧后盆地等环境,其主要证据在于玄武岩的地球化学特征。分析认为,该区玄武岩Nb相对于Th、La、Ce亏损,稀土元素曲线皆为轻稀土元素(LREE)富集型,且变化范围较宽,说明了幔源的多样性。阿尔曼太蛇绿岩套变质橄榄岩由于强烈蛇纹石化,其主量元素的地球化学意义不大,而堆晶岩成分变化较大,显示了岩浆结晶分离作用的影响,浅成-喷出岩类以辉绿岩、玄武岩和安山玄武岩为主,主体为亚碱性系列[17]

    研究区阿尔曼太蛇绿岩带位于准噶尔盆地东北缘,乌伦古河南侧,西起准噶尔盆地东缘的札河坝附近,向东沿阿尔曼太山,断续延伸到中蒙边境,走向北西西,蛇绿岩带长约200km,宽3~5km。阿尔曼太蛇绿岩带不同区段各单元发育情况不同,出露宽度相差悬殊,最宽处在札河坝一带,变窄处在兔子泉以西,出露只有数十米,甚至缺失。在东段中蒙边境地区以变质玄武岩为主,变质橄榄岩仅零星出露;在阿尔曼太山主脊线一带,蛇绿岩套发育较完整,变质橄榄岩、堆晶辉长岩和辉绿岩、玄武岩、玄武安山岩均有发育,但完好剖面不多见,堆晶岩、辉绿岩一般以残块形式出现;在西段札河坝地区蛇绿岩以发育变质橄榄岩为主,堆晶岩和辉绿岩不及阿尔曼太山主脊线处发育,顶部有具枕状构造、变形强烈的玄武岩。

    本次研究对札河坝-二台蛇绿岩测制了Ⅹ、Ⅺ号剖面(图 2图 3)。剖面控制了岩块、基质的规模、产状、接触关系。从图 2可以看出,札河坝地区蛇绿岩组分较齐全,有(白云石)蛇纹岩、辉长岩、斜长岩、辉绿岩、玄武岩、放射虫硅泥质沉积。各个岩石单元呈断块产出,相互叠置,由于受断裂构造的影响,各块体岩石均破碎严重。剖面测制,均从围岩地层开始,绿岩各岩块均小规模出露,且间隔大片第四系,受比例尺影响,剖面均未能连续穿透。但基本岩石组合已经明确,后续多为重复出现。

    图  2  阿尔曼太蛇绿岩剖面(Ⅹ号实测剖面17~59层)
    1—粉砂岩;2—绢云母板岩;3—放射虫火山灰凝灰岩;4—硅质岩;5—辉绿岩;6—玄武岩;7—长岩;8—蛇纹岩;9—辉石橄榄岩;10—闪长岩;11—斜长花岗岩;12—碳酸盐脉;13—逆冲断层;14—透镜体
    Figure  2.  The section of Armantai ophiolite(the X measured section of 17~59 strata)
    图  3  阿尔曼太蛇绿岩剖面(Ⅺ号实测剖面0~21层)
    1—灰岩;2—白云岩;3—角砾岩;4—粉砂岩;5—长石岩屑砂岩;6—安山质角砾凝灰岩;7—滑石菱铁片岩;8—绢云千糜岩;9—硅质岩;10—辉绿岩;11—辉长岩;12—蛇纹岩;13—闪长岩;14—斜长花岗岩;15—透闪石岩;16—安山玄武岩;17—逆冲断层
    Figure  3.  The section of Armantai ophiolite (the XI measured section of 0~21 strata)

    蛇纹岩一般呈暗灰绿色、黑绿色或黄绿色,色泽不均匀,质软、具滑感,叶片、纤维、纤状变晶结构,块状构造,表面局部可见蛇纹石化石棉。镜下为交代网状结构,主要由蛇纹石(60%~65%)、菱镁矿(20%~25%)和磁铁矿(5%~10%)、滑石(2%~3%)、少量铬尖晶石及极少量透闪石组成。以细粒磁铁矿、菱镁矿集合体为网而以蛇纹石为格(结)组成交代网格结构,表明原始矿物是橄榄石,局部交代强烈被蛇纹石纤状结合体替代网格。其中蛇纹石有2种:一种是无序排列的叶蛇纹石鳞片集合体,一种是平行排列的纤蛇纹石。一般叶蛇纹石排列在内核,而纤蛇纹石排列在外环。菱镁矿呈斑点浸染分布,有时聚集成团块。磁铁矿主要呈细粒集合体网脉状结构,少量集合成磁铁矿粒晶(图 4-ab)。

    图  4  蛇纹岩(a、b)和变质玄武岩(c、d)宏观及显微照片
    Pl—斜长石;Cal—方解石;Tlc—滑石;Srp—蛇纹石;Px—辉石;Mgs—菱镁矿
    Figure  4.  Photos and microphotographs of serpentinite(a, b) and basalt(c, d)

    镁铁质火山岩蚀变相对较弱,岩性为玄武岩,出露面积较大,岩石为灰黑色、青灰色,风化面多为褐色,碎裂结构,块状构造,局部具有残破的枕状构造。镜下为斑状结构,基质具间粒间隐结构。斑晶含量20%~30%,粒径为0.5~3mm,主要由斜长石和辉石组成。斜长石斑晶有2类:一类以绢云母化为主,呈碎屑状或板柱状;一类以钠黝帘石化为主,常呈板柱状,与基质协调。辉石多呈聚晶,多数绿泥石化、方解石化,个别新鲜但内部被交代。基质更复杂,由斜长石、较多蚀变矿物(绿泥石、绿帘石、阳起石和方解石)和极少量石英组成。局部具有典型的间粒间隐结构(图 4-cd)。

    野外样品采自阿尔曼太蛇绿构造岩带,主要对蛇绿岩中具代表性的基性熔岩按路线进行采样,共采集3组样品,其中在阿尔曼太兔子泉地区采集1组样品(AMT06),在阿尔曼太山地区采集2组样品(AMT11、AMT12)。通过镜下岩相学研究,对较新鲜、蚀变弱、无脉体的样品进行了岩石地球化学测试,测试单位为中国地质调查局西安地质调查中心。主量元素的XRF分析在Xios4.0kwX-荧光光谱仪(仪器编号为SX-45)上完成,精度和准确度优于5%;微量和稀土元素采用等离子质谱仪ICP-MS(仪器编号为SX-50)进行分析,分析精度和准确度优于10%,其中样品AMT06、AMT11、AMT12测试结果见表 1

    表  1  阿尔曼太基性岩主量、微量和稀土元素含量
    Table  1.  Major, trace and rare earth elements compositions
    样品SiO2TiO2Al2O3Fe2O3FeOMnOMgOCaONa2OK2OP2O5烧失量总计Mg#CuPbZnCrNiCoLiRbCsMoSrBa
    AMT06-147.110.7715.923.535.190.158.514.853.684.290.25.7999.990.6557.85.2976.140613136.323.417011.80.291.2162
    AMT06-248.120.8517.143.174.850.127.173.934.34.420.215.721000.6361.15.8575.113030.425.328.816410.90.3582.3193
    AMT06-347.90.8817.233.315.10.137.043.963.864.790.225.5799.990.6163.13.0272.213227.525.332.816511.30.6467.8273
    AMT06-447.460.8316.732.985.180.137.584.294.124.490.216.02100.020.6367.63.3873.91815024.229.117211.61.0189.2210
    AMT06-5480.816.573.214.930.147.444.454.343.950.225.96100.010.6371.54.8872.119166.228.926.31469.650.67108175
    AMT06-648.380.816.83.035.190.136.964.744.133.970.25.68100.010.6169.83.6468.425576.429.729.31448.950.5491.2258
    样品VScNbTaZrHfGaUThLaCePrNdSmEuGdTbDyHoErTmYbLuYΣREEδEu
    AMT06-1219264.240.3585.51.8516.90.963.0713.9303.8816.23.640.963.50.513.520.722.020.291.770.2818.981.20.81
    AMT06-223225.74.630.494.12.12180.953.2515.131.74.0416.63.71.053.590.493.710.762.170.3420.3118.885.60.87
    AMT06-324527.44.690.3696.92.0318.20.873.0514.330.94.0117.13.991.083.60.554.070.772.340.322.180.3520.385.60.85
    AMT06-423325.54.640.3589.41.9416.50.9314.230.93.8415.83.881.133.380.533.780.752.230.31.970.3219.3830.93
    AMT06-521224.14.640.494.82.1517.413.415.232.24.0716.83.961.193.660.543.50.762.190.32.020.3319.786.70.94
    AMT06-622426.34.530.3488.11.9417.30.953.2114.330.53.9816.33.741.023.410.533.560.742.160.292.010.2818.682.80.85
    样品SiO2TiO2Al2O3Fe2O3FeOMnOMgOCaONa2OK2OP2O5烧失量总计Mg#CuPbZnCrNiCoLiRbCsMoSrBa
    AMT11-145.241.5512.614.227.930.224.1313.263.930.520.156.1899.940.3993.31.8691.816676.94314.212.21.670.8343139
    AMT11-246.811.7112.673.668.430.214.5311.164.550.230.255.7899.990.4165.20.8698.113776.743.412.26.860.940.421260
    AMT11-348.041.6212.723.398.180.194.8510.824.520.220.235.299.980.4462.81.551011325137.613.15.670.640.8726993.5
    AMT11-445.21.5713.23.389.10.194.6710.94.20.580.196.899.980.4177.41.8410512450.741.11318.62.20.5126693.3
    AMT11-547.451.6512.773.768.080.24.810.984.390.330.245.3499.990.43532.5399.912945.53712.39.30.970.85276113
    AMT11-644.481.6213.14.248.690.214.7611.444.020.580.186.69100.010.41941.810413255.442.213.817.62.180.4823877.8
    AMT11-745.211.5713.83.657.480.18412.544.10.610.26.6499.980.41102.3187.112561.142.813.614.81.960.28353140
    AMT11-845.231.3413.494.135.460.17416.113.30.470.166.1399.990.44891.886195.848.1369.04101.40.24238128
    AMT11-946.421.4410.653.629.450.345.0614.443.220.350.164.8499.990.4262.80.6197.310550.744.812.97.940.920.0917678.2
    样品VScNbTaZrHfGaUThLaCePrNdSmEuGdTbDyHoErTmYbLuYΣREEδEu
    AMT11-130041.31.660.284.92.0215.80.270.143.4110.21.8310.73.971.254.970.816.021.333.960.543.790.5636.653.30.86
    AMT11-231445.82.060.17942.2914.80.240.113.86112.1312.34.511.515.970.957.121.644.780.694.620.745.161.80.89
    AMT11-330846.81.570.09790.52.1713.60.270.113.249.751.7711.64.091.45.320.856.71.544.530.624.250.6241.756.30.91
    样品VScNbTaZrHfGaUThLaCePrNdSmEuGdTbDyHoErTmYbLuYΣREEδEu
    AMT11-431944.61.40.1188.32.0615.10.210.13.069.391.7910.63.961.35.180.86.231.464.350.624.070.63953.40.87
    AMT11-529945.51.510.1189.91.9813.70.310.163.710.51.9711.53.91.295.550.886.781.454.640.664.20.6242.357.60.84
    AMT11-631243.31.440.1490.21.9717.80.230.053.089.41.7310.83.881.185.090.826.081.284.10.63.620.5437.252.20.81
    AMT11-728641.62.530.1596.42.1518.60.270.124.39122.0411.33.931.054.80.745.561.243.830.513.250.4833.655.10.74
    AMT11-826436.92.890.2183.41.7119.50.260.183.8910.41.710.23.220.994.160.674.751.033.270.4930.4429.148.20.82
    AMT11-9301422.740.1980.51.7913.80.240.123.269.381.549.293.7214.390.75.341.163.740.53.310.4833.247.80.75
    样品SiO2TiO2Al2O3Fe2O3FeOMnOMgOCaONa2OK2OP2O5烧失量总计Mg#CuPbZnCrNiCoLiRbCsMoSrBa
    AMT12-147.691.6214.042.19.360.168.568.583.490.20.174.0199.980.5887.31.1999.252828556.824.63.90.330.3309102
    AMT12-248.251.6313.512.248.710.168.868.753.440.310.183.961000.6801.458554026952.425.53.580.330.29282191
    AMT12-347.41.4814.081.787.60.147.279.753.880.580.195.851000.5966.11.048143119246.225.76.150.480.22225439
    AMT12-446.051.212.651.616.450.146.1513.373.541.040.147.6599.990.5876.81.2364.935116138.818.98.170.40.5207122
    0
    AMT12-546.671.5213.993.196.80.147.4313.592.470.210.173.7999.970.581011.3673.645223150.720.73.140.340.2375127
    AMT12-644.581.413.11.868.340.168.1211.852.980.60.166.8399.980.5971.91.281.444321449.228.86.490.560.18234554
    AMT12-745.721.4312.961.627.530.157.1212.523.450.510.186.82100.010.5978.20.9670.44112195021.25.290.280.3270418
    AMT12-947.31.3914.912.857.590.147.311.192.690.340.144.1499.980.5648.11.0579.94222004524.93.660.190.33381273
    样品VScNbTaZrHfGaUThLaCePrNdSmEuGdTbDyHoErTmYbLuYΣREEδEu
    AMT12-126833.214.31.011062.1618.70.320.8511.626.63.6416.54.311.44.950.794.7912.690.442.630.3626.181.70.92
    AMT12-226734.313.61.011042.1617.70.320.8710.824.73.5116.23.791.334.680.754.680.972.680.442.450.3425.477.30.96
    AMT12-323530120.8896.11.9714.50.450.6910.523.23.0914.83.471.114.230.744.540.942.510.412.50.3124.772.40.88
    AMT12-419624.79.290.7875.91.5613.10.30.587.83182.4411.32.741.23.590.593.650.82.10.342.120.2820.5571.17
    AMT12-525329.612.40.9897.22.0617.70.420.749.0221.43.1713.93.611.434.40.724.570.922.540.42.470.3324.468.91.09
    AMT12-623329.4120.8790.31.8315.60.560.6910233.1613.73.521.264.280.694.170.842.250.372.340.3122.769.90.99
    AMT12-722627.4120.93921.7215.40.50.689.7321.83.0114.63.341.194.110.654.290.892.290.422.420.3223.869.10.98
    AMT12-921227.812.60.871042.1321.60.391.099.7623.53.1514.33.411.414.20.674.30.872.330.392.570.2922.971.21.13
    注:Mg#=MgO/(MgO+TFeO)(分子数);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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    样品AMT06 SiO2含量为47.11%~48.38%,平均47.83%;TiO2含量为0.77%~0.88%,平均0.82%,与IAT(0.83%)较接近[20];Al2O3含量为15.92%~17.23%,平均16.73%,与岛弧拉斑玄武岩和板内溢流拉斑玄武岩高Al2O3含量特征相似,后两者分别为16%和17.08%[21],而明显不同于大西洋、太平洋和印度洋中脊拉斑玄武岩的Al2O3含量(分别为15.6%、14.86%、15.15%)[22];MgO含量为6.96%~8.51%,平均7.45%,相对较高;Mg#值为0.61~0.65,平均0.63,接近于原始岩浆成分(0.68~0.75),说明原生岩浆的分异演化较弱。Na2O + K2O含量为7.97% ~8.72%,平均为8.39。在SiO2-Nb/Y图解上,所有样品的Nb/Y值均小于0.7,位于亚碱性系列区;从SiO2-TFeO/MgO图解可以看出,所有样品点位于拉斑系列范围,且样品点非常集中,变化范围小(图 5)。

    图  5  Nb/Y-SiO2图解和SiO2-TFeO/MgO图解
    Figure  5.  Nb/Y-SiO2 and SiO2-TFeO/MgO diagrams

    样品AMT11 SiO2含量为44.08%~48.04%,平均46.01%;TiO2含量为1.34%~1.71%,平均1.56%,与MORB的TiO2(1.5%)较接近[20];Al2O3含量为10.65%~13.80%,平均12.78%,含量较低;MgO含量为4.00%~5.06%,平均4.53%;Mg#值为0.39~0.44,平均0.42,说明原生岩浆发生分异演化。Na2O含量为3.22%~4.55%,平均4.03%;K2O含量为0.22%~0.61%,平均0.43%;Na2O+K2O含量为3.57%~4.78%,平均4.46%。主量元素相对富MgO,贫Al2O3、K2O,Na2O含量大于K2O含量,类似于MORB型岩石。在SiO2-Nb/Y图解上,所有样品的Nb/Y值均小于0.7,位于亚碱性系列区;从SiO2-TFeO/MgO图解可以看出,所有样品点位于拉斑系列范围(图 5)。

    样品AMT12 SiO2含量为44.58%~48.25%,平均46.71%;TiO2含量为1.20%~1.63%,平均1.46%,介于IAT(0.83%)与MORB(1.5%)之间[20],更接近于MORB。Al2O3含量为12.65% ~14.91%,平均13.66%,近于大西洋、太平洋和印度洋中脊拉斑玄武岩的Al2O3含量(分别为15.6%、14.86%、15.15%)[21],明显不同于岛弧拉斑玄武岩和板内溢流拉斑玄武岩高Al2O3含量特征,后两者分别为16%和17.08%[22];MgO含量为6.15%~8.86%,平均7.60%,较高;Mg#值为0.56~0.60,平均0.58%,低于原始岩浆成分(0.68~0.75),说明原生岩浆发生较弱的分异演化。Na2O含量为2.47%~3.88%,平均3.24%;K2O含量为0.20%~1.04%,平均0.47%;Na2O+K2O含量为2.68%~4.58%,平均3.72%。在SiO2-Nb/Y图解上,所有样品的Nb/Y值均小于0.7,位于亚碱性系列区;从SiO2-TFeO/MgO图解可以看出,所有样品点位于拉斑系列范围(图 5)。

    AMT06样品的稀土元素总量(∑REE)较高,为81.19×10-6~86.72×10-6,平均为84.14×10-6,轻、重稀土元素比值(LREE/HREE)在2.07~2.24之间,(La/Yb)N=4.46~5.33,(La/Sm)N=2.24~2.55,(Gd/Yb)N=1.34~1.60,表明轻稀土元素富集而重稀土元素亏损,轻、重稀土元素分馏明显,轻稀土元素组内部的元素分馏程度较重稀土元素分馏强。在球粒陨石标准化配分模式图(图 6)中,配分曲线右倾,强烈富集轻稀土元素,Eu显示弱的负异常(δEu值为0.81~ 0.94,平均0.87)。原始地幔标准化微量元素蛛网图(图 6)显示,大离子亲石元素Rb和K富集,Sr强烈亏损,而高场强元素相对亏损,具有较强的负Nb异常和较弱的Hf、Ti负异常,Zr、Sm显示为较弱的正异常。

    图  6  稀土元素球粒陨石标准化配分图解[23]和微量元素原始地幔标准化配分图解[23]
    Figure  6.  Chondrite-normalized REE patterns and primitive mantle normalized trace element patterns

    AMT11样品的∑REE较高,为47.81×10-6~61.78×10-6,平均为53.98×10-6,LREE/HREE值在0.48~0.65之间,(La/Yb)N=0.51~0.92,(La/Sm)N=0.48~0.75,(Gd/Yb)N=1.01~1.19,表明轻稀土元素亏损而重稀土元素富集,轻、重稀土元素分馏不明显,轻稀土元素内部的元素分馏程度较重稀土元素分馏弱。从球粒陨石标准化配分模式图(图 6)可以看出,轻稀土元素亏损,而重稀土元素呈平坦型分布,稀土元素配分模式与洋脊拉斑玄武岩稀土元素配分曲线相似,Eu显示弱负异常(δEu值为0.71~0.91,平均0.83)。在原始地幔标准化的微量元素蛛网图(图 6)上,大离子亲石元素Rb、Ba、U和K富集,Sr弱亏损,高场强元素显示Nb、P等的负异常。高场强元素分异不明显,显示岛弧岩浆的特征,说明该玄武岩的形成与板块俯冲有关。

    AMT12样品的∑REE较高,为56.98×10-6~81.70×10-6,平均为70.92×10-6,LREE/HREE值在1.28~1.46之间,(La/Yb)N=2.48~3.00,(La/Sm)N=1.56~1.89,(Gd/Yb)N=1.32~1.55,表明轻稀土元素富集而重稀土元素亏损,轻、重稀土元素之间分馏明显,轻稀土元素组内部的元素分馏程度较重稀土元素分馏强。球粒陨石标准化配分模式图(图 6)显示,配分曲线右倾,强烈富集轻稀土元素,Eu无明显异常(δEu值为0.88~1.17,平均1.02)。在原始地幔标准化微量元素蛛网图(图 6)上,大离子亲石元素Rb、Th和K亏损,Ba、U具正异常,而高场强元素相对亏损,具有较强的正Ta异常和较弱的负Hf异常,Hf、Sm显示为较弱的正异常。

    在基性熔岩的TiO2- MnO×10-P2O5×10图解(图 7)中,AMT06样品点主要落入钙碱性玄武岩(CAB)和岛弧拉斑玄武岩(IAT)分界线区域,AMT11、AMT12总体落入洋中脊玄武岩(MORB)区域,其中AMT12样品点大部分落入MORB,少数有从IAT到MORB的过渡趋势。在Nb/La-(Th/Nb)N图解(图 8-a)中,除AMT12样品外,其余样品Nb/La值均小于1,且除AMT11和AMT12以外,其余样品(Th/Nb)N值均大于1。以上特征显示,除AMT12样品外,AMT06和AMT11样品均遭受地壳不同程度的混染。在基性熔岩Zr-Zr/Y图解(图 8-b)中,AMT06和AMT12样品点主要投在板内玄武岩(WPB)及与MORB的边界区域,Zr及Zr/Y值(65.70×10-6~119.00×10-6, 3.00~5.36)与大陆玄武岩(Zr>70×10-6, Zr/Y>3)相符。AMT11样品点均落入洋中脊玄武岩区域和岛弧玄武岩区域,并具有过渡的趋势,Zr及Zr/Y值(40.90×10-6~122.00×10-6, 1.84~3.02)与岛弧玄武岩(Zr < 130×10-6, Zr/Y < 4)相符[24]。在此基础上,基性熔岩的Th-Ta-Hf/3(图 9-a)和Nb×2-Zr/4-Y(图 9-b)图解显示,AMT06和AMT11样品点主要投入MORB和IAB区域,反映其与洋中脊和消减带的岛弧环境相关,AMT06样品主要显示岛弧玄武岩特征,而AMT11样品主要显示洋中脊玄武岩特征。AMT12样品点投入板内碱性玄武岩和板内玄武岩区域,表明其与板内拉张有关。

    图  7  TiO2-MnO×10-P2O5×10图解
    CAB—钙碱性玄武岩;IAT—岛弧拉斑玄武岩;MORB—洋中脊玄武岩;OIT—洋岛拉斑玄武岩;OIA—洋岛碱性玄武岩
    Figure  7.  TiO2-MnO×10-P2O5×10 diagram
    图  8  (Th/Nb)N-Nb/La图解(a)和Zr-Zr/Y图解[24](b)
    WPB—板内玄武岩;MORB—洋中脊玄武岩;IAB—岛弧玄武岩
    Figure  8.  (Th/Nb)N-Nb/La(a)and Zr-Zr/Y(b)diagrams
    图  9  基性熔岩Hf/3-Th-Ta(a)和Nb×2-Zr/4-Y(b)图解
    a中:A—N型洋中脊玄武岩;B—E型洋中脊玄武岩和大陆拉斑玄武岩的区分;C—大陆碱性玄武岩和大陆玄武岩的区分;D—消减性板块边缘玄武岩区分;图b中:AⅠ、AⅡ—板内碱性玄武岩;B—P型洋脊玄武岩;AⅡ+C—板内拉斑玄武岩;D—N型洋脊玄武岩;C+D—弧火山岩
    Figure  9.  Hf/3-Th-Ta (a) and Nb×2-Zr/4-Y (b) diagrams of basic lava

    据研究,Ba、Th、Nb、La四个分配系数相近的极不相容元素在海水蚀变或变质过程中较稳定,尤其是它们的比值在部分熔融和分离结晶过程中均保持不变,可最有效地指示源区特征。在基性熔岩La-La/Nb(图 10-a)和Nb-Th/Nb(图 10-b)图解中,AMT06样品点投入IAB区域,AMT11样品点主要投入MORB区域,AMT12样品点位于洋岛玄武岩(OIB)区域或其边界附近,且兼具二者特征或从MORB向IAB过渡的特点。

    图  10  基性熔岩La-La/Nb(a)和Nb -Th/Nb(b)图解
    IAB—岛弧玄武岩;MORB—洋中脊玄武岩;OIB—洋岛玄武岩
    Figure  10.  La-La/Nb (a) and Nb-Th/Nb (b) diagrams of basic lava

    研究区基性熔岩AMT06样品的Nb/La值(平均0.31)与典型的岛弧岩浆岩的Nb/La值(约为0.3)接近或一致,说明AMT06样品具有岛弧玄武岩特征;AMT11样品中,Th/Ta=0.63~1.45,平均值为0.83,La/Ta=17.05~33.64,平均值为24.62,与MORB中Th/Ta =0.75~2,La/Ta=10~20[25]一致,说明AMT11样品的Th/Ta、La/Ta值,更接近SSZ环境对应的比值(Th/Ta=3~5, La/Ta=30~40);AMT12样品Nb/La的平均值为1.24,与洋岛玄武岩Nb/La值(约1.3)接近,说明AMT12样品具有板内洋岛玄武岩特征。

    由此可见,阿尔曼太蛇绿岩中的基性熔岩包括3种类型,即岛弧型玄武岩(AMT06)、洋中脊玄武岩(AMT11)和洋岛玄武岩(AMT12)。其中,OIB是在洋壳俯冲时被刮削下来与其组分一起卷入蛇绿岩带就位形成的,并非蛇绿岩组分;MORB和IAT属于蛇绿岩组成部分,其球粒陨石标准化配分曲线具有轻稀土元素略亏损型的MORB特征和轻稀土元素略富集的IAT特征,原始地幔标准化配分曲线表现为IAT和MORB的双重特点,主量、微量元素判别图解显示,IAT和MORB兼具并呈现过渡的特点,相关微量元素比值特征也显示相似的特征,该特点与阿曼蛇绿岩相似[20]。结合对南智利中这种过渡型蛇绿岩的研究:从洋脊到海沟,蛇绿岩地球化学特征有从MORB向SSZ方向过渡演化的趋势,并且越向海沟,SSZ的特点就越明显[26]。针对这一特性,笔者认为,阿尔曼太蛇绿岩的形成可能介于洋脊到海沟之间的偏海沟区域。

    在基性岩Zr/Nb-Nb/Th图解(图 11-a)中,AMT06样品点主要投在岛弧玄武岩区域(ARC),AMT11样品点主要投入N-MORB的亏损地幔区域,AMT12样品点投在洋底玄武岩(OPB)边界附近。在基性岩Nb/Y-Zr/Y图解(图 11-b)中,样品点均主要落在△Nb线两侧,大多投入介于洋底玄武岩(OPB)的原始地幔(PM)与N-MORB的亏损地幔(DM)之间,指示这些样品可能为相同岩浆体系下演化的产物,且AMT12样品表现出该基性岩形成过程中,分别受到批次熔融(F)和俯冲流体作用的影响。样品在Zr/Nb-Nb/Th图解(图 11-a)中,主要集中在大陆岩石圈(EN)和大陆上地壳(UC)区域,表明其形成与岛弧或陆壳物质的带入密切相关,与岛弧带关系密切。

    图  11  基性岩Zr/Nb-Nb/Th(a)和Nb/Y-Zr/Y(b)图解[27]
    DEP—高度亏损地幔;EN—富集单元,包括上地壳和大陆岩石圈,后者可能具有消减带化学特征;REC—循环单元,包括Em1、Em2和HIMU;HIMU—高(U/Pb)地幔源区;Em1、Em2—富集地幔源区;UC—大陆上地壳;ARC—岛弧产生的玄武岩;N-MORB—洋脊玄武岩;OIB—洋岛玄武岩;OPB—洋底玄武岩;PM—原始地幔;DM—浅部亏损地幔单元。单箭头指示批次熔融(F)和俯冲流体(SUB)作用,△Nb线为地幔柱源区和非地幔柱源区的分界线
    Figure  11.  Zr/Nb-Nb/Th (a) and Nb/Y-Zr/Y (b) diagrams of basic lava

    对阿尔曼太基性熔岩的微量元素比值与不同地幔端元进行对比(表 2),基性熔岩的相关微量元素比值特征显示,其明显介于亏损地幔与大陆地壳之间,反映其来源于亏损地幔,并受到后期地壳物质的混染作用或来自消减残板片析出流体的交代作用,即与板块的俯冲相关。

    表  2  阿尔曼太基性熔岩微量元素比值与不同地幔端元的对比
    Table  2.  Comparative studies of the trace element ratio in lava and different mantle elements
    样品Zr/NbLa/NbBa/NbBa/ThRb/NbTh/NbTh/LaBa/LaTh/U
    原始地幔14.80.949.0770.910.1170.1259.64.1
    亏损地幔30.01.074.3600.360.0700.0704.0
    大陆地壳16.22.2054.01244.700.4400.20025.03.8
    HIMU2.7~5.50.66~0.774.9~6.539~850.30~0.430.078~0.1010.107~0.1336.8~8.73.5~3.8
    Em15.3~11.50.86~1.1911.4~17.8103~1540.88~1.170.105~0.1220.107~0.12813.2~16.94.50~4.86
    Em212.0~15.350.89~1.097.3~11.067~840.59~0.850.111~0.1570.122~0.1638.3~11.3
    阿尔曼太基性熔岩对应不同地幔端元微量元素比值平均值
    阿尔曼太
    基性熔岩
    AMT0620.053.1846.3467.2535.170.690.2214.653.37
    AMT1148.451.8955.12901.456.460.060.0328.920.47
    AMT127.820.8137.75614.860.430.060.0845.562.00
    注:HIMU为高(U/Pb)值地幔端元;Em1、Em2为富集地幔端元1和2;元素含量为平均值;地幔端元数据据贾大成等[28]
    下载: 导出CSV 
    | 显示表格

    (1)阿尔曼太蛇绿岩为以泥盆纪地层为基质,各构造岩块为其组成部分的蛇绿岩带。蛇绿岩中变质橄榄岩、堆晶岩、基性火山岩较发育,代表扩张机制的岩墙群规模很小,札河坝地区硅质岩较发育,并识别出斜长岩和斜长花岗岩岩块。层序组合虽受构造破坏,但从总体看仍是一套组合较完整的蛇绿岩。

    (2)对阿尔曼太蛇绿岩中基性熔岩岩石地球化学特征研究表明,基性熔岩可分为3种类型,即洋岛玄武岩(OIB)、洋中脊玄武岩(MORB)和岛弧玄武岩(IAT)。其中洋岛玄武岩不属于蛇绿岩成分,与地幔柱或热点作用有关,是后期卷入蛇绿岩带随其他组分一同构造就位而成的;基性熔岩主量和微量元素特征揭示,岩浆源于亏损的地幔源区,并且存在消减组分加入的交代作用,表明其成因与俯冲作用有关。

    (3)结合阿尔曼太蛇绿岩构造环境判别图解,基性熔岩显示出IAT和MORB兼具并呈现过渡的特点,推断该蛇绿岩的形成与岛弧相关,其形成可能介于洋脊到海沟之间的偏海沟区域。通过分析基性熔岩的物质来源,指示其可能为相同岩浆体系下演化的产物,并表明其形成与岛弧或陆壳物质的带入密切相关,与岛弧带关系密切。

    致谢: 感谢陕西省矿产地质调查中心边小卫、李新林等教授级高工和陕西省区研院韩芳林教授级高工对本项目野外工作的热情指导,陕西省地质规划研究中心周斌、陕西省矿产地质调查中心韩奎两位工程师在撰写过程给予很大帮助,审稿专家提出很多宝贵意见,在此一并表示感谢。
  • 图  1   日多地区大地构造位置(a)及区域地质简图(b)(据参考文献修改)

    JSSZ—金沙江缝合带;LSSZ—龙木错-双湖缝合带;BNSZ—班公湖-怒江缝合带;SNMZ—狮泉河-纳木错蛇绿混杂岩带;LMF—洛巴堆-米拉山断裂带;YZSZ—印度-雅鲁藏布江缝合带;STDS—藏南拆离系;Pt1-2N—念青唐古拉岩群;J1-2y—叶巴组;J-K—包括多底沟组、林布宗组、楚木龙组、塔克那组和设兴组;K1b—比马组;E1-2L—林子宗群;Q—第四系;★—测年样位置及年龄;F1—米拉山口逆冲推覆带;F2—沃卡脆韧性剪切带

    Figure  1.   Tectonic position (a) and geological map (b) of Riduo area

    图  2   日多地区米忍岩体野外露头(a、b)及镜下照片(c、d)

    Pl—斜长石;Pth—条纹长石;Kfs—钾长石;Qtz—石英;Am—角闪石;Bt—黑云母

    Figure  2.   Outcrop (a, b) and microscopic (c, d) photos of Miren rocks in Riduo area

    图  3   日多地区米忍岩体TAS图解[21](a)和SiO2-K2O图解[22](b)

    Figure  3.   TAS (a) and SiO2-K2O (b) diagrams of Miren rocks in Riduo area

    图  4   日多地区米忍岩体A/CNK-A/NK图解(a)[23]和(b)K2O-NaO2图解[24]

    Figure  4.   A/CNK-A/NK (a) and K2O-NaO2 (b) diagrams of Miren rocks in Riduo area

    图  5   日多地区米忍岩体球粒陨石标准化稀土元素配分型式图(a)和原始地幔标准化微量元素蛛网图(b)

    (球粒陨石数据据参考文献[17];原始地幔数据据参考文献[23])

    Figure  5.   Chondrite-normalized REE patterns (a) and primitive mantle normalized spider diagram (b) of Miren rocks in Riduo area

    图  6   日多地区米忍岩体锆石阴极发光(CL)图像及测点位置

    (实线圆圈表示U-Pb测点,虚线圆圈表示Lu-Hf测点,数字代表测点号及206Pb/238U年龄(Ma))

    Figure  6.   CL images and analyzing locations of zircons from Miren rocks in Riduo area

    图  7   日多地区米忍岩体锆石U-Pb谐和图(a)及206Pb/238U年龄加权平均值图(b)

    Figure  7.   Zircon concordia diagram (a) and 206Pb/238U age weighted average value diagram (b) of Miren rocks in Riduo area

    图  8   日多地区米忍岩体锆石t-εHf(t)图解(a)和tDM2统计直方图(b)

    Figure  8.   Diagram of t-εHf(t) (a) and histogram of tDM2(b) for Miren rocks in Riduo area

    图  9   日多地区米忍岩体C/MF-A/MF源区判别图解(a)及构造环境判别图解(b、c)

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

    Figure  9.   C/MF-A/MF discrimination diagram(a)and tectonic discrimination diagrams(b, c)of Miren rocks in Riduo area

    图  10   冈底斯东段始新世构造-岩浆演化模式图(据参考文献[44]修改)

    Figure  10.   Eocene tectonic-magmatic evolution pattern of the eastern Gangdise belt

    表  1   日多地区米忍岩体主量、微量和稀土元素分析数据

    Table  1   Major, trace and rare earth element compositions of Miren rocks in Riduo area

    样品编号D4253/1D0204/1D6015/1D2271/1D0499/1D6422/1D6436/1
    SiO262.1567.4671.5362.4163.6960.1863.88
    Al2O315.9314.8313.4015.2715.3416.1715.25
    TFe2O36.474.463.226.135.897.046.04
    MgO2.351.470.772.602.442.882.46
    CaO4.962.952.734.704.475.334.45
    Na2O3.663.884.713.753.143.483.15
    K2O2.193.612.712.933.262.633.31
    P2O50.190.160.080.150.140.240.14
    MnO0.130.080.090.120.110.120.11
    TiO20.810.610.400.590.570.910.59
    烧失量0.791.030.270.630.810.640.71
    总计99.63100.5499.9199.2899.8699.62100.09
    K2O/ Na2O0.600.930.580.781.040.761.05
    Σ1.792.291.932.301.982.172.00
    DI76.8865.8865.8562.4883.7959.3866.3
    SI11.1916.9917.2916.506.8618.5316.84
    A/CNK0.950.910.850.920.860.890.90
    La30.333.971.624.636.239.037.6
    Ce58.967.312249.563.977.569.2
    Pr7.257.4412.85.847.449.517.73
    Nd28.027.843.322.228.236.726.3
    Sm5.785.126.584.995.47.465.46
    Eu1.461.231.581.191.31.831.25
    Gd5.24.435.444.344.966.685.06
    Tb0.90.690.740.710.751.020.73
    Dy4.4343.053.623.95.33.76
    Ho1.060.840.680.80.881.180.88
    Er2.682.331.982.142.343.032.25
    Tm0.40.320.320.340.390.490.39
    Yb2.752.482.212.332.543.222.47
    Lu0.360.40.320.370.40.50.4
    Y3024.720.624.125.334.524.6
    P9536775158206901172587
    Sr386330339347368405355
    Ba428507714483440515400
    Zr17717719984.9104221104
    Rb67.910676.893.611081.4113
    Th7.078.213.810.531.911.642.2
    U1.311.70.8234.382.176.87
    Nb8.4217.87.6813.49.1215.39.21
    Hf1.066.911.11.041.211.531.33
    Ta0.820.920.80.720.820.830.77
    ΣREE179.47182.98293.2147.07183.9227.92188.08
    LREE/HREE2.763.557.302.803.443.083.64
    (La/Yb)N9.8110.227.577.9023.248.6910.92
    (La/Sm)N4.274.333.183.387.023.374.45
    (Gd/Yb)N1.481.621.541.562.041.721.69
    δEu0.790.770.780.810.810.790.73
    Th/Yb5.8622.247.984.5511.066.3830.25
    注:主量元素含量单位为%,微量和稀土元素含量单位为10-6
    下载: 导出CSV

    表  2   日多地区米忍岩体LA-ICP-MS锆石U-Th-Pb同位素分析结果

    Table  2   LA-ICP-MS U-Th-Pb isotopic data of zircons from Miren rocks in Riduo area

    分析点含量/10-6Th/U同位素比值年龄/Ma
    PbThU207Pb/206Pb207Pb/235U206Pb/238U207Pb/206Pb207Pb/235U206Pb/238U
    D0204-1-012.30130.0160.882.140.043830.010530.047880.011610.007970.000264711512
    D0204-1-022.1384.8062.021.370.045060.006380.051660.007530.008130.00022517521
    D0204-1-031.6059.3042.041.410.051120.007800.059030.009340.008350.00023256309589541
    D0204-1-041.9974.7361.371.220.047920.008890.051800.009310.008110.0003095389519522
    D0204-1-051.5553.0953.420.990.049880.007430.059730.008570.009090.00027191311598582
    D0204-1-062.0871.8764.751.110.045630.004290.058790.006320.009050.00026586582
    D0204-1-071.4561.9275.310.820.115710.010140.072590.006110.004690.000201891159716301
    D0204-1-081.4755.3646.341.190.048850.009150.064210.012600.009380.000291393936312602
    D0204-1-0910.74360.72168.732.140.123310.019480.197090.039130.010250.00042200628318333663
    D0204-1-102.80128.4281.771.570.051720.008980.056670.009330.008020.00025272356569512
    D0204-1-111.4255.7146.691.190.057350.012380.064560.014200.008760.000275064156414562
    D0204-1-122.3687.7666.411.320.055940.007820.064690.008410.008430.00028450319648542
    D0204-1-131.8365.4058.941.110.052050.010370.051180.012790.008370.000512874005112543
    D0204-1-143.0497.5194.711.030.029200.005600.036880.007400.010100.00028377652
    D0204-1-152.7567.7558.331.160.130190.009610.201040.017560.011540.00048210213018615743
    D0204-1-162.7196.7892.071.050.000000.000000.052320.008590.008320.00034528532
    D0204-1-172.8983.2462.581.330.081170.049340.084510.045770.008460.0002712268808243542
    D0204-1-184.17165.06146.941.120.059760.008850.065930.007440.008390.00022594326657541
    D0204-1-191.8769.1068.681.010.043070.014020.050600.016560.007930.000345016512
    D0204-1-201.6446.7141.461.130.064260.015560.087410.023080.009850.000477504978522633
    D0204-1-211.4351.4644.761.150.056010.012570.065490.014170.008910.000314544336414572
    D0204-1-221.6263.4353.291.190.051020.007770.063180.009960.009230.000252433186210592
    D0204-1-232.83120.9873.611.640.046700.007070.059720.009250.009640.0003135326599622
    D0204-1-242.81101.4866.371.530.056300.006780.074650.008980.009850.00031465269738632
    D0204-1-251.9973.2565.811.110.050430.007570.057710.008670.008490.00025213315578552
    D0204-1-262.89113.0170.901.590.045050.011100.053840.013230.008490.000245313552
    D0204-1-271.6350.3244.071.140.053820.011480.060920.012870.008610.000293654186012552
    D0204-1-283.10111.9196.601.160.048840.006740.055260.006850.008590.00028139296557552
    D0204-1-291.7762.0556.571.100.060360.009500.070730.010880.008600.000296173446910552
    D0204-1-301.4753.5147.481.130.051410.010390.056280.010720.008210.000312614725610532
    D2271-1-0112.93454.74458.200.990.048830.005660.049220.005470.007460.00017139252495481
    D2271-1-027.23318.13311.421.020.044540.011330.045550.011330.007390.000314511472
    D2271-1-036.28352.21316.301.110.072280.034830.037710.036630.007730.000699947563836504
    D2271-1-0412.81487.61555.000.880.047590.004270.048270.004270.007410.0001680200484481
    D2271-1-0514.52487.01576.020.850.046010.004200.046680.003940.007510.00016464481
    D2271-1-0621.46782.84796.980.980.047150.003550.050280.003840.007700.0001558170504491
    D2271-1-0714.86531.33547.430.970.086430.046550.050130.008530.007710.000211348791508491
    D2271-1-086.59302.13299.781.010.056490.015360.050440.013740.007430.000244725115013482
    D2271-1-0918.59650.14571.681.140.047440.004710.049910.004790.007740.0001878222495501
    D2271-1-1017.62625.43652.630.960.047820.004970.048410.005250.007360.00017100220485471
    D2271-1-1128.911250.91916.961.360.046310.004300.046630.004030.007470.0001813220464481
    D2271-1-1210.02355.94376.330.950.048060.006980.051130.007240.007620.00023102311517491
    D2271-1-1313.49581.85419.231.390.050660.007360.050880.006860.007450.00017233298507481
    D2271-1-1499.434785.101917.082.500.047520.001870.051150.002010.007840.000167689512501
    D2271-1-1513.99451.56485.180.930.047910.007220.053330.008080.008320.0003095322538532
    D2271-1-168.34310.14312.870.990.038030.010500.044170.014130.007740.000224414501
    D2271-1-1727.121148.15679.001.690.049380.004040.057280.005200.008660.00048165181575563
    D2271-1-1813.71546.36433.971.260.048970.005390.050730.005390.007760.00016146241505501
    D2271-1-1922.72694.60647.131.070.045840.008050.049420.008290.007810.00025498502
    D2271-1-2025.23755.58817.030.920.077660.006530.081930.007120.007670.000181139169807491
    D2271-1-2111.05447.91370.701.210.048490.009490.053360.010560.008120.000201244045310521
    D2271-1-2219.61881.08624.441.410.047310.003720.048230.003710.007440.0001565178484481
    D2271-1-239.72362.06351.351.030.047130.007560.047360.007530.007500.0001658341477481
    D2271-1-2411.40465.90530.570.880.047200.005370.050050.005650.007590.0001561248505491
    D2271-1-2513.46514.88490.811.050.047240.005560.048460.005700.007500.0001961259486481
    下载: 导出CSV

    表  3   日多地区米忍岩体锆石Hf同位素组成分析结果

    Table  3   Hf isotopic data of zircons from Miren rocks in Riduo area

    样品号t/Ma176Yb/177Hf176Lu/177Hf176Hf/177HfεHf(0)εHf(t)(176Hf/177Hf)itDM1/MatDM2/MafLu/Hf
    D0204-1-0151.20.042282060.000920.0011940670.00002610.2828190.00001991.72.70.282817859616.6949.9-0.964045
    D0204-1-0252.20.040380350.0003810.0011679990.000009860.28289850.00002024.55.60.282897361503.0769.3-0.96483
    D0204-1-0353.60.022714280.00006740.0006517010.000001340.28295290.00001826.47.60.282952247419.7644.0-0.980376
    D0204-1-0452.10.025569680.0002320.0007528140.000005470.28286950.00001713.44.60.282868767538.3834.1-0.977332
    D0204-1-0658.10.059825620.0002780.0017494380.000008510.2829330.00001995.76.90.282931102461.0689.0-0.947322
    D0204-1-0860.20.023765530.0001010.0006853010.000002810.28294550.00001876.17.40.28294473430.5656.8-0.979365
    D0204-1-1051.50.064526030.001270.0017950060.00003630.28289580.00002054.45.40.282894074515.5777.1-0.94595
    D0204-1-1156.20.021670350.00007710.0006260350.000001360.28290460.00001824.75.90.282903942487.3751.8-0.981149
    D0204-1-1254.10.044132580.0003330.0012455860.00001030.28291190.00001924.96.10.282910641484.9738.0-0.962494
    D0204-1-1353.70.023367320.0002270.0006699590.000005150.28290740.00001994.85.90.282906728483.9747.1-0.979827
    D0204-1-1653.40.036003780.0001420.0010622790.000004220.28291810.00001755.26.30.28291704473.8723.9-0.968013
    D0204-1-1853.90.047900060.0002860.0013871010.000007090.28293770.00001755.97.00.282936304449.8679.9-0.958232
    D0204-1-1950.90.050505860.0005540.0014178830.00001630.28295260.00001986.47.50.282951251428.8647.9-0.957306
    D0204-1-2259.30.035275190.0006740.0009823770.00001670.28292240.00001695.36.60.282921313466.7710.5-0.970419
    D0204-1-2361.80.035306930.0001870.0009932840.00000460.28293960.00002095.97.20.282938453442.4670.0-0.970091
    D0204-1-2554.50.034957780.0001150.0010384610.000004110.28296220.00001966.77.90.282961142410.8623.2-0.96873
    D0204-1-2654.50.042247880.0007760.0011606590.00002190.28288130.00001993.95.00.282880118527.4806.9-0.965051
    D0204-1-2755.30.04000080.000160.0011369540.00000370.2829460.00002086.27.30.282944826435.0659.7-0.965765
    D0204-1-2855.10.036025790.0002410.0012257470.000007980.28298910.0000187.78.80.282987838374.4562.2-0.963091
    D0204-1-3052.70.02863140.0001160.0008104880.000004370.28291940.000025.26.30.282918602468.8720.8-0.975595
    D2271-1-0147.90.027144770.00001580.000783770.000001640.28295320.00001276.47.40.282952499420.7647.1-0.976399
    D2271-1-0247.50.027028430.00020200.000795360.000005090.28297900.00001247.38.30.282978294384.4588.8-0.976051
    D2271-1-0349.60.040254950.00014900.001199150.000006410.28294630.00001536.27.20.282945188435.3662.5-0.963892
    D2271-1-0447.60.027681710.00008420.000815250.000001510.28296620.00001316.97.90.282965476402.7617.8-0.975452
    D2271-1-0548.20.031517120.00004430.000930780.000002240.28298690.00001457.68.60.282986061374.6570.6-0.971973
    D2271-1-0649.50.034534710.00024900.001000780.000005530.28297920.00001377.38.40.282978275386.2587.5-0.969865
    D2271-1-0749.50.031212210.00002480.000908200.000000470.28295880.00001366.67.70.282957961414.2633.6-0.972653
    D2271-1-0949.70.025934690.00005480.000776690.000001730.28290640.00001334.85.80.282905679486.7752.1-0.976613
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  • 收稿日期:  2018-05-03
  • 修回日期:  2018-07-20
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