| 内蒙古乌兰沟埃达克岩锆石U-Pb年龄及构造环境 |
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| 引用本文： | 王金芳,李英杰,李红阳,董培培.内蒙古乌兰沟埃达克岩锆石U-Pb年龄及构造环境[J].地质通报,2018,37(10):1933-1943. |
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| 作者姓名： | 王金芳 李英杰 李红阳 董培培 |
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| 作者单位： | 河北地质大学资源学院, 河北 石家庄 050031,河北地质大学资源学院, 河北 石家庄 050031,河北地质大学资源学院, 河北 石家庄 050031,河北地质大学资源学院, 河北 石家庄 050031 |
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| 基金项目： | 国家自然科学基金项目《内蒙古西乌旗迪彦庙蛇绿岩年代学、地球化学及大地构造意义》（批准号：41502211）、中国地质调查局项目《内蒙古1∶5万高力罕牧场三连等四幅区域地质矿产调查》（编号：1212011120711）、《内蒙古1∶5万哈腊特等四幅区域地质矿产调查》（编号：12120114064201）和河北省教育厅项目《白音布拉格蛇绿岩岩石学和地球化学研究》（编号：ZC2016013） |
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| 摘 要： | 内蒙古中部贺根山缝合带的梅劳特乌拉蛇绿岩中,新发现乌兰沟埃达克岩,岩性为花岗闪长岩。LA-ICP-MS锆石UPb测年结果表明,乌兰沟埃达克岩的侵位年龄为279.3±1.4Ma,其形成时代为早二叠世。乌兰沟埃达克岩SiO_2含量为65.92%~69.65%,MgO为1.34%~2.16%,Al_2O_3为15.30%~17.33%,Na_2O/K_2O值为3.95~14.09,Sr=359.60×10~(-6)~734.00×10~(-6),Yb=0.83×10~(-6)~2.02×10~(-6),Y=6.65×10~(-6)~12.84×10~(-6);富集K、Rb、Sr等大离子亲石元素,亏损Nb、Ta、Ti、P等高场强元素;稀土元素总量为32.18×10~(-6)~65.41×10~(-6),明显较低,轻、重稀土元素分馏明显,(La/Yb)N值为2.84~7.56,无明显Eu异常,显示出高硅埃达克岩(HSA)的地球化学特征。该埃达克岩具有岛弧型岩浆岩特征,形成于俯冲带岛弧环境,可能为洋内俯冲洋壳+俯冲深积物部分熔融并与上覆地幔楔橄榄岩反应成因。根据乌兰沟埃达克岩与梅劳特乌拉蛇绿岩的时空分布与演化特征,贺根山缝合带在早二叠世可能存在洋内俯冲作用。
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| 关 键 词： | 埃达克岩 锆石U-Pb定年 岛弧环境 洋内俯冲作用 内蒙古乌兰沟 |
| 收稿时间： | 2017/10/23 0:00:00 |
| 修稿时间： | 2018/3/20 0:00:00 |
Zircon U-Pb dating and tectonic setting of the Wulan'gou adakite in Inner Mongolia |
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| WANG Jinfang,LI Yingjie,LI Hongyang and DONG Peipei.Zircon U-Pb dating and tectonic setting of the Wulan'gou adakite in Inner Mongolia[J].Geologcal Bulletin OF China,2018,37(10):1933-1943. |
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| Authors: | WANG Jinfang LI Yingjie LI Hongyang and DONG Peipei |
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| Institution: | School of Nature Resources, Hebei GeoUniversity, Shijiazhuang 050031, Hebei, China,School of Nature Resources, Hebei GeoUniversity, Shijiazhuang 050031, Hebei, China,School of Nature Resources, Hebei GeoUniversity, Shijiazhuang 050031, Hebei, China and School of Nature Resources, Hebei GeoUniversity, Shijiazhuang 050031, Hebei, China |
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| Abstract: | The newly recognized Wulan''gou adakite in the Meilaotewula ophiolite along the Hegenshan suture zone in Inner Mongolia consists mainly of granodiorites. The LA-ICP-MS zircon U-Pb dating shows that the age of the adakite is 279.3±1.4Ma, suggesting a product of Early Permian. The rock has high SiO2 (65.92%~69.65%),Al2O3 (15.30%~17.33%),Sr(359.60×10-6~734.00×10-6), and low MgO(1.34%~2.16%), Yb(0.83×10-6~2.02×10-6),Y(6.65×10-6~12.84×10-6) content,with Na2O/K2O ratio varying from 3.95 to 14.09. The adakiteis enriched in large ion lithophile elements K, Rb and Sr, and depleted in high field strength elements Nb,Ta,Ti and P. The total REE is low(32.18×10-6~65.41×10-6), whereas REE fractionation is clear((La/Yb)N=2.84~7.56), without obvious Eu anomaly. All of the geochemical characteristics indicate that the Wulan''gou pluton belongs to high-SiO2 adakites (HSA). The adakiteis characterized by the island-arc magmatite generated in subduction zone,which suggests that it might have been formed in an island arc setting in petrology and geochemistry. It might have been derived from the intra-oceanic subducted oceanic crust plus sediment partial melting and subsequently melts reaction with overlying mantle wedge peridotite. According to the temporal and spatial distribution and evolution characteristics of the rock assemblage series of pillow tholeiite, boninite, Nb-enriched basalt, High-Mg diorite and adakite in the Meilaotewula ophiolite, the authors suggest that there might have been an intra-oceanic subduction in the Hegenshan suture zone during the Early Permian period. |
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| Keywords: | adakite zircon U-Pb dating island arc setting intra-oceanic subduction Wulan''gou Inner Mongolia |
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