| 内蒙古北山地区阿民乌素公婆泉组变质火山岩年代学、地球化学特征及地质意义 |
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| 引用本文： | 孟庆涛,徐翠,张正平,董洪凯,薛鹏远.内蒙古北山地区阿民乌素公婆泉组变质火山岩年代学、地球化学特征及地质意义[J].矿物岩石,2021,41(1):67-79. |
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| 作者姓名： | 孟庆涛 徐翠 张正平 董洪凯 薛鹏远 |
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| 作者单位： | 河北省区域地质调查院,河北廊坊 065000 |
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| 基金项目： | 中国地质调查局项目《大兴安岭南段地质矿产调查(项目编码:12120113056000):内蒙古1∶5×104标山等四幅区域地质矿产调查》。 |
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| 摘 要： | 内蒙古北山地区阿民乌素一带公婆泉组变质火山岩主要由钠长阳起岩、斜长阳起岩和斜长阳起片岩组成。三者主量元素显示相对高钠w(Na_2O)=0.32%~2.46%,低钾w(K_2O)=0.08%~0.38%、钛w(TiO_2)=0.93%~1.03%,略富镁w(MgO)=9.61%~12.04%、钙w(CaO)=9.96%~12.53%特征。w(SiO_2)为45.48%~48.76%,A-C-FM和((al+fm)-(c+alk))-Si原岩判别图解显示其原岩为基性火山岩。Zr/Ti-Nb/Y和FeO~t/MgO-w(SiO_2)图解显示亚碱性玄武岩,拉斑玄武岩系列特征。ΣREE(31.83~40.13×10~(-6))明显高于球粒陨石值,无铕异常,稀土配分模式为平坦型;球粒陨石标准化蛛网图显示大离子亲石元素Rb, Ba, K相对富集,而高场强元素Nb, Ta, P,Zr, Ti亏损明显,显示与俯冲带有关火山岩特征。钠长阳起岩LA-ICP-MS锆石U-Pb年龄475±2 Ma,时代为早奥陶世。资料研究表明,红柳河—牛圈子—白云山—洗肠井古亚洲洋自早奥陶世起持续向北俯冲,在公婆泉—东七一山一线形成时代跨度大的岩浆弧(O-S)。阿民乌素变质火山岩是该岩浆弧重要组成部分,是北山造山带早古生代洋陆转换的地质记录,对北山地区大地构造演化研究具有重要意义。
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| 关 键 词： | 公婆泉组 地球化学 岛弧环境 年代学 阿民乌素 |
THE GEOCHEMICAL,CHRONOLOGICAL CHARACTERISTICS AND GEO-LOGICAL SIGNIFICANCE OF THE ARMINWUSU GONGPOQUAN FORMA-TION META VOLCANIC ROCKS IN BEISHAN AREA,INNER MONGOLIA |
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| Meng Qingtao,Xu Cui,Zhang Zhengping,Dong Hongkai,Xue Pengyuan.THE GEOCHEMICAL,CHRONOLOGICAL CHARACTERISTICS AND GEO-LOGICAL SIGNIFICANCE OF THE ARMINWUSU GONGPOQUAN FORMA-TION META VOLCANIC ROCKS IN BEISHAN AREA,INNER MONGOLIA[J].Journal of Mineralogy and Petrology,2021,41(1):67-79. |
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| Authors: | Meng Qingtao Xu Cui Zhang Zhengping Dong Hongkai Xue Pengyuan |
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| Institution: | (Hebei Institute of Regional Geological Survey,Lang fang,Hebei 065000,China.) |
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| Abstract: | The Gongpoquan Formation metavolcanic rocks at Aminwusu,Beishan area,Inner Mongolia are mainly composed of sodium actinolite,anorthosity and plagioclase actinolite schist.The main elements of the three types of rock are relatively high in sodium w(Na2O)=0.32%-2.46%,low in potassium w(K2O)=0.08%-0.38%,titanium w(TiO2)=0.93%-1.03%,and slightly rich in magnesium w(MgO)=9.61%-12.04%and calcium w(CaO)=9.96%-12.53%.SiO2 is in the range of 45.48%-48.76%.The discrimination diagram of A-C-Fm and(Al+Fm)-(C+Alk)-Si shows that the protolith of the Gongpoquan Formation metavolcanic rocks are basic volcanic rocks,and the Zr/Ti-Nb/Y and FeOt/MgO-w(SiO2)diagrams show the characteristics of subalkaline basalts and tholeiite series.ΣREE(31.83-40.13×10-6)is significantly higher than chondrite values without Eu anomalies,and displays flat type rare earth distribution patterns.The chondrite standardized cobweb map shows that large ion lithophile elements(Rb,Ba,K)are relatively enriched,while high field strength elements(Nb,Ta,P,Zr,Ti)are significantly depleted,and the characteristic of volcanics is related to subduction zones.LA-ICP-MS zircon U-Pb dating for sodium actinolite yields an age of 475±2 Ma(early Ordovician).Research data show that the Paleo-Asian Ocean has been subducting northward since the Early Ordovician,forming a magmatic arc(O-S)with a long time span along the line of Gongpoquan and Dongqiyi Mountain.The Aminwusu metavolcanic rock is an important part of the magmatic arc,which is the geological record of the ocean-continent transition of the Beishan orogenic belt in the Early Paleozoic,and is of great significance to the study of tectonic evolution in the Beishan area. |
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| Keywords: | Gongpoquan Formation geochemistry island-arc environment chronology Aminwusu |
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