| 赣东北蛇绿岩带新元古代(~800Ma)高镁安山岩的发现及其意义 |
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| 引用本文： | 王存智,余明刚,黄志忠,洪文涛,赵希林,姜杨,周效华,段政,邢光福.赣东北蛇绿岩带新元古代(~800Ma)高镁安山岩的发现及其意义[J].地质论评,2016,62(5):1185-1200. |
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| 作者姓名： | 王存智 余明刚 黄志忠 洪文涛 赵希林 姜杨 周效华 段政 邢光福 |
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| 作者单位： | 中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016,中国地质调查局南京地质调查中心，南京，210016 |
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| 基金项目： | 本文为中国地质调查局项目“华东地区地质系列图件编制与综合研究”（编号：1212011120120）、“钦杭东段关键地区区域地质调查”（编号：12120113065200）和“江南造山带东段新元古代沟弧盆体系演化与大陆生长研究”（编号：12120114039001）的成果。 |
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| 摘 要： | 在赣东北蛇绿岩带中的樟树墩地区新发现新元古代高镁安山岩,其LA-ICP-MS锆石U-Pb法年龄为794.8±6.0 Ma。它们的Si O2介于54.90%~58.45%,Al2O3介于15.31%~16.77%(平均小于16%);Ca O为2.46%~6.73%,Fe OT/Mg O变化于0.87~1.20,具有高Mg O(6.39%~8.76%)、高Mg#(64~71)特点;富集轻稀土元素且具弱负Eu异常,明显富集LILE而亏损HFSE,Sr含量(普遍200×10-6)和Sr/Y比值(4.11~7.29)均较低,具有典型高镁安山岩的地球化学特征,类似于日本Setouchi火山带的Sanukitoids。锆石εHf(t)值介于10.23~17.79之间,反映它们起源于亏损地幔。主、微量及同位素特征均表明,本区高镁安山岩是被俯冲板片释放的含水流体交代的地幔楔部分熔融的产物,形成于大洋岛弧(洋内弧)环境,指示赣东北地区在约800Ma前时仍存在洋壳俯冲,双溪坞弧尚未增生到扬子东南缘,暗示扬子和华夏两大陆块此时尚未碰撞拼合。
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| 关 键 词： | 高镁安山岩 新元古代 樟树墩 赣东北蛇绿岩带 江南造山带 |
| 收稿时间： | 2015/5/27 0:00:00 |
| 修稿时间： | 2016/6/17 0:00:00 |
Recognition and Significance of Neoproterozoic (ca. 800 Ma) High Mg Andesites in the NE Jiangxi Ophiolite Belt |
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| WANG Cunzhi,YU Minggang,HUANG Zhizhong,HONG Wentao,ZHAO Xilin,Jiang Yang,ZHOU Xiaohu,DUAN Zheng and XING Guangfu.Recognition and Significance of Neoproterozoic (ca. 800 Ma) High Mg Andesites in the NE Jiangxi Ophiolite Belt[J].Geological Review,2016,62(5):1185-1200. |
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| Authors: | WANG Cunzhi YU Minggang HUANG Zhizhong HONG Wentao ZHAO Xilin Jiang Yang ZHOU Xiaohu DUAN Zheng and XING Guangfu |
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| Institution: | Nanjing Center, China Geological Survey, Nanjing, 210016,Nanjing Center, China Geological Survey, Nanjing, 210016,Nanjing Center, China Geological Survey, Nanjing, 210016,Nanjing Center, China Geological Survey, Nanjing, 210016,Nanjing Center, China Geological Survey, Nanjing, 210016,Nanjing Center, China Geological Survey, Nanjing, 210016,Nanjing Center, China Geological Survey, Nanjing, 210016,Nanjing Center, China Geological Survey, Nanjing, 210016 and Nanjing Center, China Geological Survey, Nanjing, 210016 |
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| Abstract: | The newly discovered Neoproterozoic high Mg andesites are located at Zhangshudun of the NE Jiangxi ophiolite belt and are dated at a zircon U Pb age of 794.8 ± 6.0 Ma. They have variable SiO2 (54.90%~58.45%), CaO (2.46%~6.73%), relatively consistent Al2O3 (15.31%~16.77%, mostly less than 16%) and FeOT/MgO values (0.87~1.20), and show relatively high MgO contents (6.22~8.47%), high Mg# (64~71), which clearly exhibits the diagnostic features of typical high Mg andesites. The study samples are enriched in LREE and have slightly negative Eu anomalies. In spider diagram, they show enrichment of LILE (eg. Rb, Ba) while depleted in Nb and Sr elements. These andesites have relatively low Sr abundance and Sr/Y ratios (4.11~7.29), similar to Sanukitoids of the Setouchi volcanic belt in Japan. The zircon Hf isotopes show positive initial epsilon Hf values ranging from +10.3 to +17.8. These geochemical data indicate Zhangshudun high Mg andesites should derived from the deplted mantle wedge metasomatized by fluids released from the subducted slab, within an oceanic arc setting. Therefore, it is inferred that the Shuangxiwu arc was away from the southeastern margin of the Yangtze Block, and the Yangtze and Cathaysia blocks had not collided at least at ca.800Ma. |
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| Keywords: | High Mg andesite Neoproterozoic Zhangshudun the NE Jiangxi ophiolite belt Jiangnan orogen |
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