| 柴北缘西段晚古生代牛鼻子梁高镁闪长岩成因机制及地球动力学过程 |
| |
| 引用本文： | 钱兵,张照伟,吕鹏瑞,王亚磊.柴北缘西段晚古生代牛鼻子梁高镁闪长岩成因机制及地球动力学过程[J].地球科学,2018,43(12):4375-4389. |
| |
| 作者姓名： | 钱兵 张照伟 吕鹏瑞 王亚磊 |
| |
| 作者单位： | 1.自然资源部岩浆作用成矿与找矿重点实验室, 陕西西安 710054 |
| |
| 基金项目： | 国家自然科学基金项目41873053陕西省自然科学基础研究计划面上项目2017JM4002中国地质调查局"东昆仑铜镍多金属资源基地调查"二级项目DD20160013国家自然科学基金项目41603050国家自然科学基金项目41602094国土资源部公益性行业科研专项项目201511020 |
| |
| 摘 要： | 牛鼻子梁地区首次发现的高镁闪长岩对于探讨柴北缘地区岩石圈地幔演化历史具有重要意义.为确定该类岩石成因及地球动力学过程，对其开展矿物学、岩石主-微量元素分析、锆石U-Pb定年和Hf同位素分析工作.岩石地球化学特征显示，岩石均为钙碱性岩石，具有富Mg（Mg#=62~72）、Cr、Ni、LREE（LREE/HREE=2.84~4.61）值、低FeOT/MgO（0.70~1.12）比值特征，属于高镁闪长岩；所有样品均表现出富集大离子亲石元素（Rb、Ba、Th、U、K）和LREE，而相对亏损高场强元素Nb、Ta、Ti、P和HREE，与典型的"赞岐岩"地球化学特征一致；锆石U-Pb同位素年代学研究表明岩石形成时代为388 Ma，为中泥盆世岩浆作用的产物.锆石Hf同位素特征显示岩石εHf（t）均为正值（4.4~11.6），表明岩浆起源于亏损地幔.结合区域构造演化过程认为，牛鼻子梁高镁闪长岩是由早古生代（540~520 Ma）消减带流体交代地幔楔后的富集地幔经历晚古生代（400~388 Ma）岩石圈伸展作用部分熔融的产物.
|
| 关 键 词： | 高镁闪长岩 岩石成因 岩石圈地幔 牛鼻子梁地区 柴北缘造山带 地球化学 |
| 收稿时间： | 2018-03-20 |
Petrogenesis and Geodynamics Processes of Early Paleozoic Niubiziliang High-Mg Diorites in West Segment of North Qaidam,Qinghai |
| |
| Abstract: | The high-Mg diorites, newly discovered in Niubiziliang area, are important for discussing the evolution history of lithospheric mantle in North Qaidam, Qinghai Province. To determine the petrogenesis and geodynamic processes of these rocks, the major and trace element analysis, zircon U-Pb dating and Hf isotopic analysis have been carried out in this paper. The petrogeochemistry shows that the rocks are calc-alkaline rocks, and enriched in Mg (Mg#=62-72), Cr, Ni and LREE (LREE/HREE=2.84-4.61) elements, with low FeOT/MgO (0.70-1.12) ratios.They belong to high-magnesium diorite. All the rocks are enriched in large iron lithiphile elements (Rb, Ba, Th, U, K and LREE) and depleted in high strength field elements (Nb, Ta, Ti, P and HREE).Additionally, the diorite rocks have the same characteristics of geochemistry as typical sanukitoids. The mean U-Pb age of the zircons in these high-Mg diorites is 388 Ma, suggesting that the rocks were formed in Middle Triassic. The zircon Hf isotopes show that all the εHf(t)(4.4-11.6) are positive, indicating the magma was originated from the depleted mantle.Combined with the regional tectonic evolution process, it is suggested that the mantle source of the Niubiziliang high-Mg diorite was formed by the reaction of the slab-derived fluids with the overlying mantle peridotite in Early Paleozoic (540-520 Ma). In Late Paleozoic (400-388 Ma), partial melting of the enriched mantle might generate the studied high-Mg diorites due to lithospheric extension. |
| |
| Keywords: | |
|
| 点击此处可从《地球科学》浏览原始摘要信息 |
|
点击此处可从《地球科学》下载全文 |
|
