| 内蒙古东乌旗巴彦都兰二长花岗岩年代学、地球化学特征及其地质意义 |
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| 引用本文： | 李敏,李敏,程银行,李艳锋.内蒙古东乌旗巴彦都兰二长花岗岩年代学、地球化学特征及其地质意义[J].地质科技通报,2015,34(4):6-14. |
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| 作者姓名： | 李敏 李敏 程银行 李艳锋 |
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| 作者单位： | 天津地质矿产研究所, 天津 300170 |
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| 基金项目： | 中国地质调查局中国地质调查项目“内蒙古1∶5万奥尤特等六幅区调”(1212011220446) |
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| 摘 要： | 为了解晚古生代西伯利亚板块南缘增生造山过程中的岩浆活动特征,对东乌旗巴彦都兰二长花岗岩岩相学、锆石U-Pb年代学、锆石Hf同位素和岩石地球化学进行了研究,并讨论了岩石成因和构造环境。锆石LA-ICP-MS U-Pb定年结果为(277.2±0.7)Ma,以正的锆石εHf(t)(6.8~14.1)为特征,具有年轻的锆石地壳模式年龄(tcDM)(865~655 Ma),属于早二叠世晚期岩浆活动产物。二长花岗岩以高钾w(K)=3.63%~4.95%,K2O/Na2O=0.91~1.47]、富碱w(K2O+Na2O)=7.52%~9.16%]、准铝质-弱过铝质(A/CNK=0.96~1.15)为特征;稀土元素总量较低(38.82×10-6~193.20×10-6),(La/Yb)N为3.91~23.08,轻、重稀土元素分异较明显,呈弱负铕异常(δEu为0.34~1.17);富集部分大离子亲石元素(LREE、Rb、K等);Zr弱负异常、Hf弱正异常,亏损Sr、Nb、Ta、P、Ti,显示后造山花岗岩特征。综合分析表明,巴彦都兰二长花岗岩形成于伸展的构造环境中,是贺根山洋盆闭合后的后造山阶段产物,为865~655 Ma前洋壳俯冲形成的先成地壳部分熔融而成。
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| 关 键 词： | Ⅰ型花岗岩 早二叠世 地球化学 锆石U-Pb年龄 锆石Hf同位素 |
| 收稿时间： | 2015-03-19 |
Characteristics and Geological Significance of Chronology and Geochemistry of Bayandulan Monzonitic Granites in Dong Ujimqin Qi,Inner Mongolia |
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| Affiliation: | Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China |
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| Abstract: | In order to learn the characteristics of magma activity along the southern plate of Siberianlate during Late Palaeozoic Eta.,petrography,U-Pb chronology of the zircon,zircon Hf-isotopeand geochemistry of the Bayandulan monzonitic granite are studied to constrain the genesis and tectonic setting of the rock in Dong Ujimqin Qi,Inner Mongolia.Zircon U-Pb dating obtained by LA-ICP-MS analyses from the monzonitic granite is(277.2±0.7) Ma,suggesting that it is the production of magmatic activities in later period of Early Permian.The εHf(t) values and the crust model ages(tDMc) of Bayandulan monzonitic granite,are 6.8-14.1and 865-655 Ma respectively.The Bayandulan monzonitic granite is enriched in K(K=3.63%-4.95%,K2O/Na2O=0.91-1.47)and alkali(K2O+Na2O=7.52%-9.16%),suggesting the feature of metaluminous to weak peraluminous(A/CNK =0.96-1.15).It is apparently different in LREE and HREE,with most rocks having weakly negative Eu anomalies(δEu=0.34-1.17).The rock is depleted in rare earth elements(∑REE=38.82×10-6-193.32×10-6),and Sr,Nb,Ta,P,Ti enriched in partial LILE(LREE,Rb,K and so on)with weakly negative Zr anomaly and weakly positive Hf anomaly,showing characteristics of post-orogenic granites.The monzonitic granite produced in extent environment,and was the product of post-orogenic evolution after closing of the Hegenshan Ocean.And the formation of the rock is partial melting of juvenile continental crust resulted from subducted oceanic crust exised during 865-655 Ma. |
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