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| 阿拉善右旗地区晚石炭世埃达克岩的发现及其大地构造意义 | |
| 引用本文： | 张伟,王金荣,陈万峰,翟新伟,马锦龙.阿拉善右旗地区晚石炭世埃达克岩的发现及其大地构造意义[J].高校地质学报,2014,20(3):378. |
| 作者姓名： | 张伟 王金荣 陈万峰 翟新伟 马锦龙 |
| 作者单位： | 兰州大学地质科学与矿产资源学院;甘肃省西部矿产资源重点实验室(兰州大学); |
| 基金项目： | 国家自然科学基金(41173014);中央高校基本科研业务费项目(Lzu-Jbky-2012-128)联合资助 |
| 摘 要： | 阿拉善地块西南缘沙枣泉石英闪长岩LA-ICP-MS锆石U-Pb年龄302 ± 9.2 Ma，SiO2含量在60.66%~61.37%之间，MgO 含量在2.13%~2.51%(Mg#= 0.48~0.51)之间，具高Al(Al2O3=17.98%~ 18.44%)，富Ca(CaO= 6.08%~6.59%)、富Na贫K(Na2O= 4.20%~4.46%，K2O= 0.67% ~0.92%，K2O/Na2O= 0.16~0.22)， 以及高Sr(582×10 - 6~620×10 - 6)， 低Y(11.4×10-6~13.7×10–6)、Yb(1.02×10- 6 ~1.51×10–6)，高的Sr/Y(35.15~53.25)，Y/Yb(11.00~11.23)和La/Yb(7.28~15.10)比值；岩石富集不相容元素（Rb,Th, K, U, Pb等） 及LREE，强烈亏损高场强元素Nb，Ta，Ti以及HREE，轻微的正Eu异常（δEu为0.97~1.18，平均值为 1.1）。岩体总体特征类似于环太平洋新生代埃达克岩。结合霍尔森-查干楚鲁蛇绿岩年代学及区域内其他花岗岩类地球化学 特征认为，沙枣泉埃达克岩是晚石炭世晚期霍尔森-查干楚鲁弧后盆地向南初始俯冲于阿拉善微陆块之下，玄武质洋壳 发生部分熔融且与地幔发生一定程度的交代作用、快速上升形成的，指示雅布赖-巴音诺尔公“陆缘弧”建造始于晚石 炭世-早二叠世, 古亚洲大洋最南端的南蒙古大洋闭合时限应介于275~250 Ma之间，为中-晚二叠世。 |
| 关 键 词： | 埃达克岩 岩石地球化学 锆石U-Pb年龄 古亚洲大洋 阿拉善地块 |
The Discovery of the Carboniferous Adakite and its Tectonic Implications in AlxaYouqi |
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| ZHANG Wei,WANG Jinrong,CHEN Wanfeng,ZHAI Xinwei,MA Jinlong.The Discovery of the Carboniferous Adakite and its Tectonic Implications in AlxaYouqi[J].Geological Journal of China Universities,2014,20(3):378. | |
| Authors: | ZHANG Wei WANG Jinrong CHEN Wanfeng ZHAI Xinwei MA Jinlong |
| Abstract: | The La-ICP-MS zircon U-Pb dating of the Shazaoquan quartz diorites in the southwestern margin of Alxa Block yields a weighted mean age of 302±9.2 Ma. The rocks show SiO2 contents ranging from 60.66% to 61.37%, MgO from 2.13% to 2.51%, and high Na and low K contents (Na2O=4.20~4.46%，K2O=0.67~0.92%, K2O/Na2O=0.16~0.22), and high Al（Al2O3=17.98~18.44%）， Ca (CaO= 6.08%~6.59%), and Sr （582×10-6~620×10-6） contents, but low Y （11.4×10 -6~13.7×10-6） and Yb （1.02×10-6~1.51×10-6) contents.They also have high Sr/Y （35.15~53.25） , Y/Yb （11.00~11.23） and La/Yb (7.28~15.10) ratios. The quartz diorites also show enrichment in incompatible elements （Rb, Th, K, U, Pb etc.） and LREE, and strong depletion in high field strength elements, such as Nb, Ta and Ti, and HREE, with slight positive Eu anomalies (δEu=1.1). The geochemical characteristics of the studied dioritic rocks resemble those of the Cenozoic adakites from the Pacific margin. Together with the regional geological settings, we suggest that the Shazaoquan quartz diorites originated from the partial melting of the subducted basaltic oceanic crusts under the Alxa Block and underwent metasomatization with the surrounding mantle. It also suggests that the formation of Yabulai-Bayinnuoergong arc began in Late Carboniferous-Early Permian and the closure of the southernmost of the Paleo-Asian Ocean occurred between 275~250 Ma. |
| Keywords: | Adakite petrology and geochemistry zircon U-Pb age Paleo-Asian ocean Alax Block |
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