| 松潘造山带马尔康强过铝质花岗岩的成因及其构造意义 |
| |
| 引用本文： | 时章亮,张宏飞,蔡宏明.松潘造山带马尔康强过铝质花岗岩的成因及其构造意义[J].地球科学,2009,34(4):569-584. |
| |
| 作者姓名： | 时章亮 张宏飞 蔡宏明 |
| |
| 作者单位： | 1.中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉 430074 |
| |
| 基金项目： | 国家自然科学基金项目(Nos.40773019,40821061);;教育部和国家外国专家局高等学校学科创新引智计划(No.B07039) |
| |
| 摘 要： | 松潘造山带广泛出露印支期后碰撞型花岗岩类, 其中包括埃达克质花岗岩类、A型花岗岩和I型花岗岩, 但目前人们对该区印支期强过铝质花岗岩尚未有深入的研究.松潘造山带马尔康花岗岩属于强过铝质花岗岩(A/CNK=1.10~1.20), 其岩石类型主要为中粒二云母花岗岩和中细粒二云母花岗岩.利用LA-ICP-MS锆石U-Pb定年方法, 获得中粒二云母花岗岩的岩浆结晶年龄为208±2Ma, 中细粒二云母花岗岩的岩浆结晶年龄为200±2Ma.马尔康强过铝质花岗岩K2O/Na2O=1.13~1.75, 富Rb、Th和U, 贫Sr、Ba、Co和Ni等元素; 稀土元素组成上显示存在强到中等的负Eu异常(Eu/Eu*=0.15~0.65);全岩初始87Sr/86Sr比值(ISr) 为0.70712~0.71137, εNd (t) =-10.36~-8.43, 锆石εHf (t) =-11.8~-1.1.地球化学和Sr-Nd-Hf同位素组成一致表明, 它们的岩浆来自于地壳物质的部分熔融, 其中中粒二云母花岗岩的源岩类型主要为地壳中的泥质岩类, 而中细粒二云母花岗岩的源岩主要为地壳中的杂砂岩类.结合松潘带的地质背景、区域构造-岩浆事件及其岩浆岩的组合分析, 印支期岩石圈拆沉作用可以用来解释马尔康强过铝质花岗岩的形成机制.在松潘带, 印支期岩石圈拆沉作用导致软流圈物质上涌, 这不仅促使了加厚下地壳物质发生部分熔融, 如松潘带印支期埃达克质和I型花岗岩浆的形成, 而且还诱发了中地壳物质的部分熔融, 如马尔康强过铝质花岗岩的形成.这表明松潘带印支期岩石圈拆沉作用已使地壳不同层次发生部分熔融作用.
|
| 关 键 词： | 强过铝质花岗岩 锆石U-Pb定年 地球化学 Sr-Nd-Hf同位素 岩石成因 松潘造山带 |
| 收稿时间： | 2009-01-16 |
Petrogenesis of Strongly Peraluminous Granites in Markan Area,Songpan Fold Belt and Its Tectonic Implication |
| |
| SHI Zhang-liang,ZHANG Hong-fei,CAI Hong-ming, .State Key Laboratory of Geological Processes , Mineral Resources,China University of Geosciences,Wuhan ,China .Faculty of Earth Sciences,China.Petrogenesis of Strongly Peraluminous Granites in Markan Area,Songpan Fold Belt and Its Tectonic Implication[J].Earth Science-Journal of China University of Geosciences,2009,34(4):569-584. |
| |
| Authors: | SHI Zhang-liang ZHANG Hong-fei CAI Hong-ming State Key Laboratory of Geological Processes Mineral Resources China University of Geosciences Wuhan China Faculty of Earth Sciences China |
| |
| Institution: | SHI Zhang-liang1,2,ZHANG Hong-fei1,CAI Hong-ming1,2 1.State Key Laboratory of Geological Processes , Mineral Resources,China University of Geosciences,Wuhan 430074,China 2.Faculty of Earth Sciences,China |
| |
| Abstract: | In the Songpan fold belt, Indosinian post-collision granitoids, including adakitic, A-type and I-type granitoids, are widespread.However, studies on Indosinian strongly peraluminous granite in this area are rare.The Markan granites, including medium-grained two-mica granite and medium-fine grained two-mica granite, are strongly peraluminous granites with Al index (A/CNK) =1.10-1.20.By using LA-ICP-MS zircon dating method, magma crystallization ages 208±2 Ma for the medium-grained two-mica granite and 200±2 Ma for the medium-fine grained two-mica granite are obtained.Both the two-mica granites show K2O/Na2O=1.13-1.75, and are enriched in Rb, Th and U etc while depleted in Sr, Ba, Co and Ni etc.REE compositions display strongly fractionated patterns, with (La/Yb)N =6.08-51.84 and Eu/Eu*=0.15-0.65.In Sr-Nd-Hf isotopic compositions, they have initial 87Sr/86Sr ratios (ISr) of 0.707 12-0.711 37, εNd(t) values of-10.36 to-8.43 and zircon εHf(t) values of-11.8 to-1.1.Geochemical and Sr-Nd-Hf isotopic compositions suggest that the magmas for the medium-grained and medium-fine grained two-mica granites were derived from patial melting of argillaceous and greywacke sediments, respectively.According to the combined analysis of geological background, regional tectono-magmatic events and magmatism composition, Indosinian lithospheric delamination can account for the magma generation of the Markan strongly peraluminous granites.The Indosinian lithospheric delamination resulted in mantle asthenospheric upwelling, which promoted not only partial melting of the thickened lower crust (e.g.the adakitic and I-type granitoid magma gerneration), but also partial melting of the middle-lower crust (e.g.the Markan granite gerneration).This indicates that the Indosinian lithospheric delamination in the Songpan fold belt had resulted in partial melting at different levels of crust. |
| |
| Keywords: | strongly peraluminous granite U-Pb zircon dating geochemistry Sr-Nd-Hf isotopes petrogenesis Songpan fold belt |
| 本文献已被 CNKI 等数据库收录！ |
| 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》下载免费的PDF全文 |
|
