| 河北武安洪山正长岩杂岩体成因与地表快速隆升-剥蚀特征 |
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| 引用本文： | 张波,张晓旭,苏尚国,莫宣学,刘江涛,伍月,蒋校.河北武安洪山正长岩杂岩体成因与地表快速隆升-剥蚀特征[J].地球科学,2020,45(7):2571-2584. |
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| 作者姓名： | 张波 张晓旭 苏尚国 莫宣学 刘江涛 伍月 蒋校 |
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| 作者单位： | 1.中国地质大学地球科学与资源学院, 北京 100083 |
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| 基金项目： | 中国地质调查局项目12120115069701中国地质调查局项目DD20190429国家自然科学基金项目41272105教育部博士学科点基金20130022140001 |
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| 摘 要： | 为了解洪山正长岩杂岩体的源区和成因，以及其形成过程中伴随的地表快速隆升-剥蚀现象，在详细野外地质调查的基础上，采用岩石学、地球化学、U-Pb年代学和锆石Lu-Hf同位素研究.获得洪山正长岩杂岩体内粗粒辉石正长岩和粗面岩锆石U-Pb定年结果分别为125.6±1.2 Ma和121.9±2.3 Ma，粗粒正长岩年龄介于二者之间；岩体属于高硅、富碱、富铝、贫镁、Mg#较低的准铝质-过铝质碱性岩，经历了大量地壳流体的改造；粗粒辉石正长岩锆石普遍发育年龄相近的核-边结构，核部εHf（t）为-5.0~-8.4，具有较高的U、Th、Pb含量，边部与同时期的粗面岩锆石特征一致εHf（t）为-11.3~-14.4，U、Th、Pb含量较低，表明锆石结晶初期岩浆具有地壳来源的特征；喷出相的粗面岩直接覆盖在中心相的粗粒正长岩上，这一现象说明洪山正长岩杂岩体形成过程中伴随了地表的快速隆升-剥蚀.洪山正长岩杂岩体的形成过程与拆沉作用关系密切，是华北克拉通减薄作用在地表浅部的响应.
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| 关 键 词： | 正长岩杂岩体 中生代 锆石U-Pb年代学 地球化学 Lu-Hf同位素 隆升-剥蚀 克拉通减薄 |
| 收稿时间： | 2020-03-08 |
Genesis and Rapid Uplift-Erosion Characteristic of Hongshan Syenite Complex in Wuan,Hebei, China |
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| Abstract: | In order to understand the source and genesis of the Hongshan syenite complex, and the rapid surface uplift-erosion phenomenon accompanying its formation, on the basis of detailed field geological surveys, petrology and geochemistry, U-Pb chronology and zircon Lu-Hf isotope studies were used. The result show that:the U-Pb dating of coarse pyroxene syenite and trachyte zircon in the Hongshan syenite complex yields age of 125.6±1.2 Ma and 121.9±2.3 Ma, respectively. Coarse syenite's age is between 125.6±1.2 Ma and 121.9±2.3 Ma, The rock belongs to high-silicon, alkali-rich, aluminum-rich, magnesium-depleted, and low-Mg# metaluminous-peraluminous alkaline rocks, that have undergone a lot of crustal fluid transformation; coarse pyroxene syenite. Coarse-grained pyroxene syenite zircon has a similar core-edge structure of common developmental age. The core εHf (t) is -5.0 to -8.4, which has a high U, Th, and Pb content. The edges are consistent with the zircon characteristics of the trachyte at the same period, εHf (t)=-11.3 to -14.4, and low content of U, Th, and Pb, which indicates that the magma in the early stage of crystallization of zircon has the characteristics of crustal origin. the coarse-faced rocks of the ejected facies are directly covered on the coarse-grained ortho rocks of the central facies. This phenomenon indicates that the formation process of Hongshan syenite complex was accompanied by rapid uplift and erosion of the surface. The formation process of the Hongshan syenite complex is closely related to demolition, which is the response of the North China Craton thinning in the shallow surface. |
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