蒙古巴音苏赫图钨矿床正长斑岩锆石U-Pb年龄及其地质意义
发布时间：2018-09-12 10:34
【摘要】：正长斑岩是中蒙边界中生代重要的岩浆记录,其花岗岩年龄和地球化学特征对于揭示该时期的构造格局与演化历史具有重要意义。本文对蒙古国东南部出露的正长斑岩进行锆石的LA-ICP-MS定年,获得锆石U-Pb年龄为(170.6±1.7)Ma,表明该花岗岩形成于中—晚侏罗世。花岗岩的元素地球化学研究结果表明:该花岗岩属高钾钙碱性S型花岗岩;花岗岩具高硅特征,其Si O2质量分数为73.99%~74.28%,Al_2O_3为12.36%~14.30%,MgO为0.17%~0.45%,过铝质;稀土元素总量为51.92×10~(-6)~58.32×10~(-6),稀土元素分布型式为具有明显负铕异常的"燕型"曲线;在原始地幔标准化的微量元素蛛网图中,Rb、Th、U、K、Zr、Hf和轻稀土元素(如La、Ce、Nd和Sm等)富集,Ba、Sr、P和Ti等元素强烈亏损,Nb和Ta具有中等—弱亏损特点;n(~(143)Nd)/n(~(144)Nd)初始比值较高(0.512320~0.512451),平均为0.512404;ε_(Nd)(t)为-4.6~-2.3,均为负值。主量、微量元素和同位素特征表明,该正长斑岩形成于同碰撞向后造山构造体制转换过渡的伸展大地构造环境背景之下。地壳加厚作用和地壳物质部分熔融,很可能是形成本区花岗岩的两个最主要的动力机制。
[Abstract]:Syenite porphyry is an important record of Mesozoic magma in the boundary of China and Mongolia. Its granite age and geochemical characteristics are of great significance to reveal the tectonic framework and evolution history of this period. The LA-ICP-MS dating of zircon from syenite porphyry in the southeast of Mongolia has been carried out. The zircon U-Pb age of (170.6 卤1. 7) Ma, indicates that the granite was formed in the middle to late Jurassic. The results of elemental geochemistry show that the granite belongs to high potassium calc-alkaline S-type granite, the granite is characterized by high silicon content, and its Si O 2 mass fraction is 73.99 and 74.28%. The content of Al _ 2O _ 2O _ 3 is 12.36 ~ 14.30% and 0.17 ~ 0.45%, peraluminous. The total amount of rare earth elements is 51.92 脳 10 ~ (-6) (58.32 脳 10 ~ (-6), and the distribution pattern of rare earth elements is "swallow" curve with obvious negative europium anomaly. In the primitive mantle-standardized trace element cobweb map, RbTH, La,Ce,Nd, Sm, etc., are strongly depleted in elements such as La,Ce,Nd and Ti. NB and Ta are characterized by moderate to weak depletion (~ (143) Nd) / n (~ (144) Nd) initial ratio is higher (0.512 320 / 0. 512451), average is 0. 512 404; 蔚 _ (Nd) (t) is -4. 6 ~ 2. 3, all are negative values. The principal, trace elements and isotopic characteristics indicate that the syenite was formed in the context of an extensional tectonic environment during the transition from the same collision to the post-orogenic tectonic regime. Crustal thickening and partial melting of crustal materials are probably the two main dynamic mechanisms for the formation of granites in this area.
【作者单位】： 华北理工大学矿业工程学院地质系;中国科学院地质与地球物理研究所矿产资源研究重点实验室;河北省地矿局第五地质大队;造山带与地壳演化教育部重点实验室北京大学地球与空间科学学院;
【基金】：“十一五”科技支撑计划重大项目(编号:2006BAB01A02) 校级博士科研启动基金项目(编号:20164043)的成果~~
【分类号】：P597.3;P618.67
本文编号：2238737
[Abstract]:Syenite porphyry is an important record of Mesozoic magma in the boundary of China and Mongolia. Its granite age and geochemical characteristics are of great significance to reveal the tectonic framework and evolution history of this period. The LA-ICP-MS dating of zircon from syenite porphyry in the southeast of Mongolia has been carried out. The zircon U-Pb age of (170.6 卤1. 7) Ma, indicates that the granite was formed in the middle to late Jurassic. The results of elemental geochemistry show that the granite belongs to high potassium calc-alkaline S-type granite, the granite is characterized by high silicon content, and its Si O 2 mass fraction is 73.99 and 74.28%. The content of Al _ 2O _ 2O _ 3 is 12.36 ~ 14.30% and 0.17 ~ 0.45%, peraluminous. The total amount of rare earth elements is 51.92 脳 10 ~ (-6) (58.32 脳 10 ~ (-6), and the distribution pattern of rare earth elements is "swallow" curve with obvious negative europium anomaly. In the primitive mantle-standardized trace element cobweb map, RbTH, La,Ce,Nd, Sm, etc., are strongly depleted in elements such as La,Ce,Nd and Ti. NB and Ta are characterized by moderate to weak depletion (~ (143) Nd) / n (~ (144) Nd) initial ratio is higher (0.512 320 / 0. 512451), average is 0. 512 404; 蔚 _ (Nd) (t) is -4. 6 ~ 2. 3, all are negative values. The principal, trace elements and isotopic characteristics indicate that the syenite was formed in the context of an extensional tectonic environment during the transition from the same collision to the post-orogenic tectonic regime. Crustal thickening and partial melting of crustal materials are probably the two main dynamic mechanisms for the formation of granites in this area.
【作者单位】： 华北理工大学矿业工程学院地质系;中国科学院地质与地球物理研究所矿产资源研究重点实验室;河北省地矿局第五地质大队;造山带与地壳演化教育部重点实验室北京大学地球与空间科学学院;
【基金】：“十一五”科技支撑计划重大项目(编号:2006BAB01A02) 校级博士科研启动基金项目(编号:20164043)的成果~~
【分类号】：P597.3;P618.67
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