内蒙古东乌珠穆沁旗晚奥陶世辉长岩地球化学特征及其地质意义
发布时间：2018-08-08 12:51
【摘要】：内蒙古东乌珠穆沁旗朝不楞以西及巴润布尔嘎斯台地区出露一套辉长岩。LA-MC-ICPMS锆石U-Pb测年结果显示该辉长岩体侵位于450～461Ma,属于晚奥陶世。样品的Si O_2、K_2O、TiO、MgO含量低,σ=0.10～2.77,总体属低钾拉斑玄武质系列。随着Mg O含量的增加,主要氧化物如Si O_2、CaO、Fe_2O_3含量呈上升趋势,Al2O3、Na2O呈下降趋势。根据稀土和微量元素特征,可将辉长岩分为三类。第一类REE含量最高,具有微弱的Eu正异常,(La/Yb)_N=19.99～20.3,稀土配分曲线明显右倾,富集LILE(Rb、Sr、Ba),相对亏损Nb、Ta。第二类REE含量减少,具有明显的Eu负异常,(La/Yb)_N=4.88～9.68。第三类REE含量最低,具有明显的Eu负异常,(La/Yb)_N=1.33～2.03。后两类辉长岩均亏损Nb、Sr、Ba,富集Rb、Th、U、Zr、Hf,稀土配分曲线弱右倾,岩石形成过程中可能受到陆壳物质混染。三类辉长岩整体兼具MORB型及岛弧玄武岩特征,可能是晚奥陶世古亚洲洋向北俯冲过程中弧后盆地的产物。
[Abstract]:A set of zircon U-Pb dating results of gabbro. LA-MC-ICPMS indicate that the pyroxenite transgression occurred at 450 ~ 461 Ma and belongs to the late Ordovician. The content of MgO in Sio _ 2 + K _ 2O _ 2 O _ 2O _ 3 is low, 蟽 _ (0.10) ~ (2.77), which belongs to the Black Tortoise series of low K _ 2O _ 3. With the increase of MgO content, the content of main oxides such as Sio _ 2CaO _ 2O _ 2 Fe _ 2O _ 3 increases and Al _ 2O _ 3H _ 2O decreases. According to the characteristics of rare earth elements and trace elements, gabbro can be divided into three types. The first kind of REE has the highest content and weak EU positive anomaly, (La/Yb) tipped to the right of the partition curve of rare earth elements, enriched in LILE (RB ~ (2 +) S ~ (2 +) Ba), and relatively depleted in NB ~ (2 +) Ta. In the second group, the content of REE decreased and there was obvious negative EU anomaly, (La/Yb) was 4.88% 9.68%. The content of REE in the third group was the lowest, with obvious EU negative anomaly, and (La/Yb) was 1.332.03. The latter two types of gabbro are depleted in NB, Sr and Ba, enriched in RbTH, UZR and HF, and the REE partition curve is weakly right tilted, which may be contaminated by continental crust materials during the formation of the rocks. The three types of gabbro have the characteristics of MORB type and island arc basalt, which may be the product of the back-arc basin during the northward subduction of the Paleo-Asian Ocean in late Ordovician.
【作者单位】： 中国地质大学(北京)地球科学与资源学院;四川理工学院经济与管理学院;河北省区域地质矿产调查研究所;四川省地质工程勘察院;
【基金】：中国地质调查局地质调查项目(编号:1212010811001、1212011085490、12120114093901、1212011220465)的成果~~
【分类号】：P588.124
[Abstract]:A set of zircon U-Pb dating results of gabbro. LA-MC-ICPMS indicate that the pyroxenite transgression occurred at 450 ~ 461 Ma and belongs to the late Ordovician. The content of MgO in Sio _ 2 + K _ 2O _ 2 O _ 2O _ 3 is low, 蟽 _ (0.10) ~ (2.77), which belongs to the Black Tortoise series of low K _ 2O _ 3. With the increase of MgO content, the content of main oxides such as Sio _ 2CaO _ 2O _ 2 Fe _ 2O _ 3 increases and Al _ 2O _ 3H _ 2O decreases. According to the characteristics of rare earth elements and trace elements, gabbro can be divided into three types. The first kind of REE has the highest content and weak EU positive anomaly, (La/Yb) tipped to the right of the partition curve of rare earth elements, enriched in LILE (RB ~ (2 +) S ~ (2 +) Ba), and relatively depleted in NB ~ (2 +) Ta. In the second group, the content of REE decreased and there was obvious negative EU anomaly, (La/Yb) was 4.88% 9.68%. The content of REE in the third group was the lowest, with obvious EU negative anomaly, and (La/Yb) was 1.332.03. The latter two types of gabbro are depleted in NB, Sr and Ba, enriched in RbTH, UZR and HF, and the REE partition curve is weakly right tilted, which may be contaminated by continental crust materials during the formation of the rocks. The three types of gabbro have the characteristics of MORB type and island arc basalt, which may be the product of the back-arc basin during the northward subduction of the Paleo-Asian Ocean in late Ordovician.
【作者单位】： 中国地质大学(北京)地球科学与资源学院;四川理工学院经济与管理学院;河北省区域地质矿产调查研究所;四川省地质工程勘察院;
【基金】：中国地质调查局地质调查项目(编号:1212010811001、1212011085490、12120114093901、1212011220465)的成果~~
【分类号】：P588.124
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